Phytoplankton Productivity in Tomahawk Lagoon, Lake Waipori, and Lake Mahinerangi

Fisheties Research Bulletin No. j

By S. F. Mitchell,

Fishedes Research Division

New Zøla¡d Marine Department Phytoplankton Productivity in Tomahawk Lagoon, Lake \)Øaipori, and Lake Mahine rangi Frontispiece: Water samples being taken from Tomahawk Lagoon with a Van Dorn sampler on a calm winter's day. Fisheties Research Bulletin No. j

Phytoplankton Productivity in Tomahawk Lagoon, Lake \Øaipori, and Lake Mahinerangi

By S. F. Mitchell, Department of ZooIogy, University of Otago

Fisheries Research Division

New Zealand Marine DePatment Published by the New Zealand Marine Departnent Wellington 1971

This series of research bulletins, which was begun in 1968, after the establishment of the Fisheries Research Division, is a different series from that published by the New Zealand Marine Department between 1927 and 1957 and entitled Fisheries Bulletins Nos. 1 to 12.

Received for publication 29 April 1968 FOREWORD

THOSE of us interested in the proper use of our water resources are concerned with the eflects of natural and induced changes on the productivity of the environment, yet relatively few fundamental observations have been made of primary production in fresh water in temperate regions. But such observations are essential if we are to be able to measure accurately the changes taking place.

In providing a critical appreciation of techniques a.nd fundamental i¡formation on three South Island lakes Dr Mitchell has established a. basis for those comparative studies which future workers will certainly desire to make. He has also indicated how variation of chemical and physical conditions may alter primary productivity, and his observations on the apParent mutual exclusion of phytoplankton and macrophytes must be of interest to those concerned with the aesthetic appearance, as well as the productivity, of our inland waters.

G. DuNcnN Weucrr, Director, Fisheries Research Division. CONTBNTS Page INTRODUCTION 9 DESCRIPTION OF THE LAKES 10 Tomahawk Lagoon No. 2 10 Lake Mahinerangi l1 Lake Waipori t2 CLIMATE l4 METHODS l5 Sampling Methods t5 Chemical and Physical MMethods 15 PhvtoplanktonPhytoplankton Productivitvvity t7 Calculationlalculation of Daily Production 19 Nutrient Fertilisation Experiments 21 SEASONAL DISTRIBUTION OF PHYTOPLANKTON PRODUCTIVITY 22 ALGAL SPECIES COMPOSITION 25 fntroduction 25 Tomahawk Lagoon 25 l-ur.ã wuipo.i är,J Luk" Mahinerangi 25 PHYSICAL AND CHBMICAL CONDITIONS 27 Temperature 27 Secchii Disc Transparency 27 Oxygen Concentrations 27 Ionic Solutes 28 SAMPLING BRRORS AND REGIONAL VARIATIONS IN PHYTOPLANKTON PRODUCTIVITY 3l Introduction 31 Tomahawk Lagoon 31 Lake Mahinerangi 3l Lake Waipori 33 THE RELATION BETWEEN 14C AND L AND DB ESTIMATES 35 INTERRELATIONS ÉETWEEN PHYTOPLANKTON AND MACROPHYTES IN TOMAHAWK LAGOON 37 Introduction :tl Light Penetration 37 Chloride 39 pH and Alkalinity 40 Calcium and MasMagnesium +l Phosphate 4l Nitrogen and Potassium 43 Discussion +3 ANNUAI PRODUCTION 45 Introduction 45 Comparison of Tomahawk LagoÀ, Lake Waipori, arrd Lake'Mahinàrangi 45 Comparison of the Otago Lakes with Lakes in Other Countries +5 Production and Rèspiration 47 THE RELATION OF PHYTOPLANKTON PRODUCTIVITY TO ENVIRON- MENTAL FACTORS 49 Introduction 49 Lake Mahinerangi 49 Lake Waipori 53 ÍáÀrr'"-Ër,"go."-.. :: .: .. 54 INDICES OF PHYTOÞLANKTON PRODUCTIVITY 55 Introduction 55 Chlorophyll a 55 Secchi Disc TransfarencyT 57 GENERAL DISCUSSION AND CONCLUSIONS 61 Lake Mahinerangi 6l Lake Waipori 63 Tomahawk Lagoon 64 Methods 65 SUMMARY 66 ACKNOWLEDGMENTS 6B REFERENCBS . . 69 APPENDIX I: EVALUATION OF METHODS 72 A. Methods for Measuring pH 72 B. Methods To Determine Carbon Dioxide Concentrations . 73 C. Calculation of 14C Assimilated in Photosynthesis 74 D. Standardisation of the laC Method . 75 E. Calculation of Sa.turation Values for Calcium Carbonate 76 APPENDIX II: RBSULTS A. Productivity Data 78 B, Oxygen Concentrations . . 81 C. Surface Water Temperatures in Lake Mahinerangi, Lake Waipori, and Tomahawk Lagoon 82 D. Secchi Disc Transparencies in Lake Ma.hinerangi B3 E. Data Used in Multiple Regression Analyses B3 F. Data from Analyses To Determine Concentrations of Phytoplankton Pigments 84 FIGURES Page 1. The locations of the three lakes studied, Tomahawk Lagoon No. 2, Lake Waipori, and Lake Mahinerangi, in the Otago district 9 2. Tomahawk Lagoons l0 3. Lake Mahinerangi 11 t2 t+

22 January 1966 g. Maximum hourly rates of gross productivity an^d net productivity per unit volume 22 ofoI TomahawÉI OmanawK Lagoon,L4B,uull, JutyJ ury 1963-Augustr JwJ-r !u 1964 ' of Tomahawk Lagoon, 1 0. Phytoplankton productivity beneath unit surface area July 1963-January 1966 23 11. Phytoplankton productivity per unit volume of Lakes Waipori and Mahinerangi' ÑoïemberNovember IvoJ-January1963-'lanuary rroo1966 23 12. Phytoplankton proáuctivity bene-ath unit surface area of Lake Mahinerangi' November 1963-November 1965 2+ 13. Phytoplankton productivity beneath unit surface area of Lake Waipori, November 1963-November 1965 2+ 14. Chlorophyll ø concentrations and Secchi disc transparencies in Tomahawk Lagoon 27 15. ',Ihe concentrations of reactive phosphorus in Lakes Mahinerangi and waipori, May-December 1965 16. Alkalinity, pH, and total hardness in Lake Mahinerangi, December 1964-January 29 1 966 17. Alkalinity, pH, Lake Waipori during 1965 30 lB. comparison of different sampling stations in Lake Mahinerang 32 19. Typical depth ctivity in Tomahawk Lagoon 3B 39 20. Alkatinity and pH of Tomahawk Lagoon . ionic solutes, and phytoplankton prodÙctivity in Tomahawk Lagoon in 21. Rainfall, 40 May-July 1965 +2 22. The concentrations of reactive phosphorus in Tomahawk Lagoon in 1965-66 23. Comparison of the estimates of phytoplankton.productivity obtained experimentally foì Luke Mahinerangi with those calculated from the multlPle regresslon 'Ltke, ' 51 52 2+, Waip it' igo+-oo ' ' Lakes erangi on a logarithmic 25. ty of 53 temPerature " and 26 chloroPhYll in Lakes WaiPori Mahinerangi, October 1964-August 1965 56 57

59 J'

TABLES Page 1. Analysis of variance of samples for phytoplankton productivity from Lakes Mahine- raîgi and Waipori and Tomahawk Lagoon t7 2. Precision of 14C estimates 18 3. Depth of P..* and relation between productivity at 0.75 m and P*^* in Lake Waipori 1B ,!. Diurnal variation in P-* in Tomahawk Lagoon 19 Page 5. Ratio of hourly rates of proCuction for the period sunrise-sunset to hourly rates for the 4-hour period in the middle of thd day . . 20 6. Dominant- pJa-nkton algae^and occurrence of argal" brooms-- - --:in Tomahawk ""Lagoon, July 1963-Decæmbei 1966 . .- . -*" .".' 2s 7. Range of variation in chemical conditions in the three lakes and streams entering Tomahawk Lagoon and Lake Waipori, 1963-66 . . 29 Chemical conditions in Lake Mahinerangi . 32 9. compaúson of-phytoplankton.productivìty at different sampling stations on Lale Waipori and the corresponding chloridó ors .1.1 10. "orr""rri.ut chemical conditions in drainage water purrìped into Lake waipori from the Taieri Plain 34 ll' comparison of ¡esults from the 14c and L and DB oxygen methods for 4-hour experiments in Tomahawk Lagoon 35 l2' Phytoplanïton produotivity in Tomahawk Lagoon in July-December, 1963-65 5t 13. Chloride, calcium, and magnesium concentrations in Tomahawk Lagoon 40 14. Phytoplankton productivity in some lakes of diflerent countries 46 15. Maximum rates oJ phytoprankton productivity obtained by various worken during dinoflagellate blooms 47 16. An{rual.production and respiration by prankton in Tomahawk Lagoon and Lake Ma.hinerangi +B 17. The relation between p-." in Lake Mahinerangi and temperature, day length, and water level' 50 18. concentrations of chlorophyll and carotenoid pigments in Lakes Mahinerangi and Waipori and Tomahjwk Lagoon 5B 19. Standardisation of the. distillation-absorption method of estimating total concentration of carbon dioxide in water t5 20, compariso" _gf .th" pH-alkalinity merhod with the distillation-absorption method in Lakes Waipori and Mahinerangi t5 21. Comparison, of the pH-alkalinity method with the distillation-absorption method rn I omanawk Lagoon t3 22. compaúson.-9f..the- pH.-arkalinity_method, with the method of McKinney and Amorosi (1944) lor the three-Otago lakes IJ 23. Com_parison of counting rates obtained by Geiger-Müller counting of raC_labelled phytoplanl{ton on Millipore filters, and tho"se obtained bt-ti.i"iã scintillation counting after wet combrxtion of the samples 75 24. counts per ampoule laclabelled of the stock solution of bicarbonate . 76 25. Phytoplankton proàuodvity in Tomahawk Lagoon measured by the L and DB method 78 26' Phytoplankton productivity in Tomahawk Lagoon measured by the 1ac method . 79 27. Diurnal variatioru in phytoplankton prod.ctivity in Tomahawk Lagoon 79 28. Phytoplanlton productivity in Lake waipori measured by the L and DB method 79 Ph;ntoplanÌton 29. productivity in Lake waipori measured by the rac method 79 30. Phytop-lan-kton pro{uctivity in Lake Mahinerangi measured by the L and DB method BO 31. Phytoplankton prodtrctivity in Lake Mahinerangi measured by the rae method . BO 32. Oxygen concentratiÖns in Tomahawk Lagoon at sunrise B1 33. Oxygen concentrati.ons in Tomahawk Lagoon at Doon BI 34. Oxygen concentrations in Tomahawk Lagoon at 10.30 a.m. 81 35. Oxygen concentrations in Lake Waipori at sunrise B1 36. Oxygen concentrations in Lake Mahinerangi at sunrise BI 37. surface temperatures in Lake Mahinerangi, November 1963-August 1964 B2 38. Surface temperatures in Lake Waipori, November 1963-August 1964 . . B2 39. surface temperatures in Tomahawk Lagoon, september lg64-January 1966 B2 40. Diurnal variations in temperaturÊ in Tomahawk Lagoon B3 41. Secchi disc transparencies in Lake Mahinerangi B3 42. Daø-gsed in multiple regression analyses of the relation between p-", - ". in Lake Mahinerangi and tempóratute, day iength, and water level I B3 43. Temperatures and P,u". Lake Waipuri, the multiple regression equation w ke Uahineiranli . . B4 44. Daø from analyses to phytoplankton pigments in tomanawß Lagoon B4 45. Data. from.analyses to determine concentrations of phytoplankton pigments in Lake Waipori B5 46' Dala .from_ analyses ,to determine concentrations of phytoplankton pigments in Lake Mahineransr 85 INTRODUCTION

Between July 1963 and January 1966 an experi- was continued at irregular intervals until Decem- mental investigation of phytoplankton productivity ber 1966. The aims of the study were to establish was carried out on f-omahawk Lagoon No. 2, the level of phytoplankton productivity and to Lake Waipori, and Lake Mahinerangi, which all investigate the influence of some environmental lie between latitude 45" 50' and 46o S, in the factors on phytoplankton productivity. Most Otago district of the South Island, New Zealand studies of phytoplankton productivity have been (fiS. l). Some observational data were gathered made in tropical or continental regions, and this on macrophytic vegetation during this period, and is one of the first in an area having an oceanic observation of the phl,toplankton and macrophytes climate .

Fig. I : The locations of the three lakes studied, Tomahawk Lagoon No. 2, Lake Waipori, and Lake Mahinerangi, in the Otago district. DESCR.IPTION OF TIIE LAKES

TOMAHAWK LAGOON NO. 2 has been increased by dredging to between 2.0 and 2.6 ¡n in an area of about 2,000 sq m near the The two Tomahawk Lagoons (fiS. 2) are coastal centre of the basin. Dredging with a suction pump lagoons lying on the southern side of the Otago has been carried out since 1961 by a local organisa- Peninsula on the outskirts of the city of Dunedin. tion wishing to improve conditions for trout, and They have been forn-red in two small river vallel's the spoil has been used to reclaim aî area on the by the grou,th of a bar across their estuarl', and a southern shore. There are small areas of swamp small stream runs through sandhills from No. 1 at the south-western and north-eastern ends of Lagoon to the sea. The two lagoons are separated No. 2 Lagoon, but the northern and south-eastern by a natural spit which carries a road, but are shores slope steeply and there is only a narrow linked under the road by a narrow channel. The swamp zone between hill pasture and the lake. direction of flow was always observed to be from The lake sediment is 0.4-1.3 m thick in the centre No. 2 Lagoon to No. 1. Number I Lagoon is more of the basin and lies on a substratum of sancl (Dr saline (Cl-: 2,500 mg/l) than No. 2 (Cl-: Ð. Scott, pcrs. comm. ), It is black when wet, and 278-sB0 ms/l). a dried sample contained 8.55 percent of carbon 0.83 percent nitrogen. Number 2 Lagoon is 400 m from the sea. It has and of an area of 9.6 hectares, a length of 600 m, and a The drainage basin has an area of 1.8 sq km, maximum width of 300 m. Its depth is between and the geological substratum is Basic Volcanic 1.0 and 1.2 m over much of the basin, but this Rocks. The soils are Southern ancl Central Yellow-

fDeþqrtment of Land; ønd Snruey þhoto.

Fig. 2: Tomahawk Lagoons. Number 2 Lagoon is on the right. S: Sampling station.

t0 tèb

ooì

I mile :1.61 km

Nos. 2-7' Forest is indicated by Fig. 3: Lake Mahinerangi' I : Main sampling station' 2-7: Sampling Stations stippling.

dunes rvith some urban development.

LAKE, MAHINERANGI 6.2 m. The mean rate of outflorv is 6.45 m'/second, Lake Mahinerangi (fiS. 3) is an artificial lake so that the mean retention time is about B months' formed by the damming of the Waipori River in There has been little shoreline erosion ancl much of the shore is hard clay coverecl with a thin layer of gravel. There are areas of bog along the lower ..uãh.t of the inflowing streams' The sediment is grey, and after being dried a sample contained 3'3 percent of carbon. in 1862, and dredging and sluicing were carried The drainage basin has an area of about 33 out there until the lake was formed (Pairman sq km. The lake is fed by the Waipori River and 1ss1). by a number of smaller streams' the largest of 'Ihe rock of The lake is 390 m above sea level anrl is 30 km rvhich are named in fig. 3. basement Zone Schist and the from the sea, It has an area of 19.7 sq km, a length the catchment area is Chlorite Earth. There of 14.5 km, and a maximum width of 1.6 km' The soil is High Country Yellow-Brown rate at which electricity is generated varies, and is a pine plantation of 1B'5 sq km round the lower the exception of an area of this causes the lake level to fluctuate. During the half of thì lake. With of lake period of study the depth at the dam varied from about 20 hectares on the southern side the ll fDeþottnent of Lønd.s ø^d 51.Ì!e! þhoto. Fig-a 4: Lake .Waipori. P: Chan-nel.thrgr1sþ r*'hìch drainage is received. 1: Main sampling station. 2 and 3: Other sampling stations. The Wai ¡ori River florvs in at 1op right and out at lou,er left. oPposite the main sampling station, which rvas which is protected from flooding by a sropbank sown with grass in 1964, the rest of the drainage built along trvo sides of the lake. The Waipori basin was undeveloped tall tussock grassland until River enters it through three main channels in the September-October 1965, when aÍr area on the north-eastern region and leaves by two main chan- northern side of the lake was ploughed in prepara- nels at the south-west. These rejoin and flow to tion for subsequent development. By Februarl' the Taieri River after receiving drainage from 1967 the area under development was about 3.9 nearby Lake Waihola. The margins of the lake, sq km. which is surrounded by willows, are swampy. Although it is 10 km from the sea, LAKE WAIPORI Lake Waipori is tidal. The depth over most of the basin is nor- Lake Waipori (fig. 4), which also lies on the mally about 0.6 m at low tide and a little more lVaipori River system, has an area of 2.4 sq km. than I m at high tide. There is no intrusion of It is a natural lake on the low-lying Taieri Plain, saline rvater. The macrophyte Anacharis canadensis

t2 the two (Michaux) Planchon usually covers much of the differences in water chemistry between bottom of the lake from spring until late autumn' lakes. The bottom deposits consist mainly of sand mixed The lake also receives drainage, which is col- with fine silt. After leaving Lake Mahinerangi the Waipori River receives only one large tributary-the Con- tour Channel, an artificial stream carrying drain-

the capacity of the Pumps it was estimated that this contribution rarely exceeds about 1-2 percent of the volume of the lake in any one day. In addition, one small stream, the Meggat Burn, enters the northern side of the lake. The mean retentiort time for the lake water is about 76 hours' This figure is based on the mean rate of flow in the Waipori River ancl on the assumption that the mean depth of the l¿Lke is 0.75 m'

13 CLIMATE

'fhe climate of the region is characterised by Àt the Dunedin r\irport neteorological station, windy and variable conditions, without extremes rvhich is 10 km from Lake Waipori, sunshine hours of temperature, and with a moderate rainfall in all and rainfall are similar to those at Musselburgh, months. Monthly mean values for temperature) though temperatures are frequently i to 2oc lower. hours of bright sunshine, and rainfall for the years At the Lake Mahinerangi meteorological station, 1963-66 at the Musselburgh meteorological station, rvhich is 7 km from the main sampling station on rvhich is 1 km from Tomahawk Lagoon, are shown the lake, temperatures are generally a further 1-2' in fig. 5 with day length. Temperatures have been lower, and the rainfall is generally similar to that derived by taking monthly means of daily maxima at Musselburgh. No sunshine records are available and daily minima and taking a mean of the two. for this station.

tÃ o 4

Et gÊ |! o cm hr "C 12 180 15 -

t0-

60 5-

0- MJJASOND

Months

Fig. 5: Day lengtl and meteorological conditions at the Musselburgh meteorological station (mean values for the years 196366).

t4 METI{ODS

SAMPLING METHODS exposed to light for onl;' a few seconds during the lemoi,al cf simples or the addition of newly filled Tomahawk Lagoon was sampled al weekly ones. Timing of the experiment began with the intervals. Sampling of the other lakes on alternate opening of the box after the collection and pre- weeks was attempted, but it could not alwal's be liminary treatment of the samples ancl encled when done. The light and dark bottle oxygen produc- the box lvas closed on the bottles. The samples tion method (L ana DB ), which is often attributed rvere taken in orcler fron-r the surface and removed to Gaarder and Gran (1927 ), but which was used in the same order. 1'hey rvere attached to the line i¡r reverse orcler. Final treatment of the samples usually began within half an hour of the end of the experiment. The sample bottles were suspencled vertically, r.vith the shoulclers of the bottles at the experi- noon, half a sun-day, from sunrise or astronomical mental depths. The method of attachment and the was used in Tomahawk Lagoon. In the olher lakes type of float have been d samples were set out at sunrise and retrieved at ( 1963 ) . Vertical intervals ,rr.rt.t. With the'aC nlethod a 4-hour experimental were kept to at least 0.5 m period was used in all three lakes, the experiments from either end of the float. being started 2 hours before astronomical noon' for wind and s'.in at the beginning of incubatiorl The sampling depths most fre quently used were: to prevent entanglement of the anchor and sample Tomahawk Lagoon-surface, 0.25 m, 0.5 m, and suspension ropes and shading of the deeper samples 0.75 m or 1 m; Lake Waip6¡l-5¡¡f¿çç, 0.25 m, by the float. per- 0.5 m, and also 0.75 m when tidal conditions Sampling stations are indicated in figs. 2,3' and the mitted this sample to be suspended free of 4. The main stations tvere always sampled' Between 0'5 m, 1 nt, bottom; Lake h'fahinerangi-surface, May 1965 and January 1966 samples were also 2 m, 4 m, and occasionaLlll' 6 m. Surface and taken from one of the other stations on Waipori 0.25 m samples were taken from a few centimetres or Mahinerangi on each sampling day. The minor below the surface. All other samples were sus- station was sampled first, usually at 0'5 m and taken' pended at the depth from which thel' were 1.0 m in Mahinerangi and 0.25 m and 0.5 m in The samples were taken with a 5.5-t non-metallic Waipori. All samples were incubated at the main water sarnpler (Van Dorn 1956) coated on the stations, and those from the other stations were outside with black tape. The sample bottles were held in the box in subdued light for 20 to 30 filled in shadow in the bottom of the boat ancl thel minutes while they lvere moved between stations. were flushed with an amount of lvater equal to Samples for chemical analysis were taken in three or four times their volume' With the L and Pyrex glass bottles at a depth of a few centimetres DB method 25O-ml Pyrex glass bottles with taC at the start of the experiments. Phosphate samples stoppers were used, ancl with the ground-glass were taken in polyethylene bottles impregnated method similar bottles o'f 114-mt to 130-m1 with iodine (Heron 1962). All glass bottles were capacity were used. Two light bottles and one cleaned with chromic acid cleaning mixture, fol- dark bottle were suspended at each depth with lowed by six rinses with tap water, six rinses with the and DB method, but with the 'nC method L distilled water, and a further three rinses with dark bottles were suspended at only two or three lake water before being filled. The water sampler depths. A 250-ml sample was taken at each depth was scrubbed with detergent solution and rinsed' for the alalysis of the total carbon dioxicle concentration or the initial oxygen concentration. CHEMICAL AND PHYSICAL METHODS After being filled and at the completion of an experiment, bottles were stored in darkness b1' Secchi disc transparency was measured with a being wrapped in a large sheet of black poly- disc of the type described by Welch (1948)' When ethylene in a wooden box' Bottles in the box were the L and DB method was used estimates were

15 taken 3-4 hours after sunrise in Mahinerangi and l-he time taken for each titration was constant to at noon in Tomahawk Lagoon. All readings were within about 30 to 40 seconds. Oxygen saturations taken 2 hours before noon when the 'aC method were calculated from the nomogram of Mortimer was used. Temperature readings were taken at a (1956). A standard erro¡ of 0.048 mg/l was depth of 10 cm at the beginning and end of each obtained from five replicate estimations from experiment and the mean was recorded. Subsurface 'Iomahawk Lagoon, and in a similar test with six temperatures were measured with a thermistor samples from Lake Nlahinerangi the standard unit. Approximate estimates of chloride were crror was 0.020 mg/I. The difference can pro- obtained by N4ohr's method (Vogel l95l). Total bably be attributed to the presence of large hardness, calcium, and magnesium were estimated amounts of seston in the lagoon, as this may reduce by EDTA titrations with the indicators Solo- the precision (for example, Steemann Nielsen 1958). The precision for Waipori was assumed to be similar to that for Mahinerangi. Initially pH was estimated with a Beckman portable pH meter. This was replaced in Decem- ber 1964 by a Lovibond comparator, which was used with B.D.H. indicators. The bromocresol Chlorophyll and carotenoid pigments were esti- purple indicator was used for samples from Lake mated by the spectrophotometric method of Waipori and Lake Mahinerangi from 12 May to Richards and Thompson (1952) as described by 26 August, and the phenol red indicator was used Strickland and Parsons (19G0), by use of Milli- at other times. This instrument was replaced by a pore filters (grade HA, having a mean pore size of Metrohm portable pH meter in September 1965. 0.45 p.) and with minor modifications to increase The calibration of these methods is described and the optical densities. Filter membranes containing discussed in Appendix IA. Both the Metrohm algae were stored in darkness in a desiccator at meter and the phenol red indicator appeared to minus 5oc for a maximum period of 2 weeks. A give satisfactory estimates, but corrections had to standard er¡or of 0.265 mg of chlorophyll afm" be applied to the estimates obtained with the was obtained from six replicate estimates having a bromocresol purple indicator. The Beckm¿Ìn meter mean concentration of 5.08 mg/m'. The amount was not checked against any other method. of water filtered was restricted for these estimations so that photometric errors would be similar Total carbon dioxide was estimated initially by to those for routine estimations at lower concen- the titration method of McKinney and Amorosi trations of chlorophyll ø than this. (19+4). In December 1964 this was replaced by the pH-alkalinity method, and the concentration Dissolved oxygen was estimated with methods of carbon available for photosynthesis was calcu- described by the British Ministry of Housing and lated from a table (Saunders, Trama, and Bach- Local Government (1956). The Rideal-Sæwart mann (1962)). In most samples from Tomahawk permanganate modification of the Winkler method Lagoon phenolphthatein alkalinity was present and was used for the early samples from Tomahawk it was necessary to use the modification of the Lagoon, but this was soon replaced by the Alster- method which is described by these authors for berg sodium azide modifica,tion, which was used waters of high pH. This modification is essentially for all samples from Lakes Waipori and Mahine- the phenolphthalein-methyl orange method, re- rangi. The reagents were added to the light and viewed by Partridge and Schroeder (1932). The dark bottle samples in the field, and these were method which these authors describe was used in returned to the laboratory and titrated immedi- the laboratory as a check on the accuracy of ately. Samples the for initial oxygen concentration pH-alkalinity method. In Partridge and were !h. titrated soon after collection, either in the Schroeder's method the carbon dioxide is ãistilled field or in the laboratory. One or two 50-ml from the sample and absorbed in standard harium samples were titrated from each bottle. The iodine hydroxide solution by recirculation of the air in indicator of B.D.H. (Inrernational) Ltd. was used a closed system. The residual barium hydroxide is and this was added when about 0.2 ml of N/80 titrated with standard hydrochloric acid. The thiosulphate was needed to complete the titration. sample volume was 250 ml, and N/50 solutions

16 I t.

of acid and barium hydroxide were used. Results number was often not reached in the time avail- for the calibration of the field methods are dis- able. Light bottle samples were counted for a cussed in Appendix IB. A correction of minus maximum period of 10 minutes and dark bottle ì ll 0.95 mg of carbon/l was applied to the pH- samples were each counted for 5 minutes. Count- ri rl alkalinity estimates for f'omaha,wk Lagoon, and ing rates were corrected for the individual bottle a correction of plus 0.5 mg of carbon/l was volumes (Appendix IC). A correction of plus applied to the estimates obtained with McKinney 5 percent was applied for isotopic discrimination and Amorosi's method for Lakes Waipori and (Strickland 1960). The method was standardised Nfahinerangi. by liquid scintillation counting of the'nCO, formed by wet combustion of labelled plankton samples PHYTOPLANKTON PRODUCTIVITY and by acidification of aliquots of the 'nCO, solution (Appendix raC Method ID). A stock solution of Na,'nCO' having a specific Precision of laC Bstimates activity of 20.6 millicuries/millimole was diluted A preliminary graphical examination of the to a concentration of 5 microcuries/ml with water data indicated that the devia,tions of the paired that had been distilled twice in P)'r.* glass. samples frorn their means were approximately pro- Aliquots of 1 ml rvere then dispensed into clean portional to the means, and so a logarithmic trans- glass ampoules which were sealecl and autoclaved. formation of the data was made (Snedecor 1956, The contents of an ampoule were added quanti- p. 320). The transformed data rvere used in a tatively with a glass hypodermic syringe to each single classification analysis of variance which was sample. Dark bottles were treated first ancl then rnade for the three lakes separately. The sample light bottles in order frorn the surface. After incu- for Mahinerangi was the 51 pairs of bottles bation the phytoplankton were re- "C-labelled obtained between 11 November 1964 and 20 moved from the samples by filtration with 25-mm June 1965, for Waipori the 52 pairs obtained between Millipore HA filters. Dark bottle samples were 28 November 1964 and 15 1965, and for filtered first and then light bottle samples in order June Tomahawk Lagoon the 53 pairs obtained between from the greatest depth. One or two aliquots of 28 December 1964 and 7 1965. A summary 10, 25, or 50 ml were filtered from each sample. June of this anall,sis is given in table 1. The square root Pressure filtration was used at first, but in March of the mean square due to differences between 1965 this was replaced by a vacuum filtration replicate bottles was retransformed to give the system having the same effective filtration area. standard error of a single bottle, and the standard Filtration was carried out at a pressure of 1 atmo- error for the two bottles used was calculated from sphere or a vacuum of half an atmosphere. With both systems the walls of the containers were rinsed with 5-10 ml of distilled water followed by 5 ml TABLB of 4 percent formalin. The filter was suckecl dry phytopla and the pressure released after each rinse. The Waipori filters residue were mounted on 3-cm with their Source of Sum of Degrees of Mean metal discs smeared lightly with petroleum jelly Lake variation squares freedom square and were stored cardboard boxes. in Mahinerangi Betrveen samples 15.870967 50 Bet$'een bottles 0.128188 51 0.002513 The radioactivity of the samples was deter- Total 15.999155 101 t mined with a thin window Geiger-Müller tube Waipori Betweensamples 9.759077 51 within 2 weeks of sampling. A correction was Betweenbottles 0.067293 52 0.00 1 294 r: applied for variations in counting efficiency by Total 9.82637 0 103 counting a standard source of ra"diation (1O-micro- Tomahau,k Betweensamples 35.173726 52 fr curie 'nC-labelled plastic designated CFP. by the Betu,eenbottles 0.087029 JJ 0.001642 Total 35.260755 105 Radiochemical Centre, Amersham, Buckingham- I *In rl shire, England) for 5 minutes at intervals the tables in this bulletin the following symbols denote f $-hourly the meanings shown: \ and correcting sample counts to a standard count- _ nil or zero ing rate of 410 c/s for this. Counting to a total of .. figures not available .. . not applicable 4,000 counts per sample was attempted, but this - - amount too small to be expressed t7 fi t this. Results are shown in table 2 as percentages Waipori and Mahinerangi. For maximum a¡rd of the means. minimum day length respectively, the error in this region becomes abo,ut 1.2 and 2.5 mg of carbonf TABLB 2: Precision of 14C estimates (percentage of mea¡)' m'.hour. Differences between duplicate samples Standard error Standard error of from Tomahawk Lagoon were often larger than Lake of bottle mean mean for 2 bottles would be expected from the titration errors, so Mahinerangi 12.2 8.6 that for this lake the main source of error was Waipori 8.6 6.1 Tomahawk 9.1 6.9 probably bio,logical rather than analytical.

Extrapolation of Depth Profrles L and DB Method Depth profiles were almost invariably of the and resPira- The figures for oxygen production most typical form for unstratified lakes, in which use of tion were converted to units of carbon by productivity declines exponentially with increasing the equations given by Strickland (1960). A photo- depth from a maximum (P'*') occurring at the quotient synthetic quotient of 1.2 and a respiratory surface or at some depth below the surface. When of 0.83 were used. P¡uax occurs below the surface it represents an Samples from Lakes Waipori and Mahinerangi approximation to production at optimal light in which bubbles formed were discarded. Bubbles intensity. Depth profiles were plotted to a depth frequently formed in surface and 0.25-m samples of 0.75 m for Lake Waipori, 1 m for Tomahawk from Tomahar,r'k Lagoon at times of high produc- Lagoon, and 6 m for Lake Mahinerangi. These tivity, and sometimes these results had to be used were the estimated mean depths in the first two as approximate estimates. In an attemPt to elimi- and the greatest depth at which significant pro- nate this source of error 50 ml of each sample was duation could usually be detected in Lake Mahine- replaced by "boiled-out" distilled water on a rangi. On days when no experimental estimate of number of the sampling days between January productivity at 6 m in Lake Mahinerangi was and X4arch 1964 and a correction for dilution was made, a value was estimated indirectly by extra- applied to the results. On 2 days this method was polating a straight line fitted by eye to the linear checked by comparison with the usual method at lower part of the curve when the depth profile was depths where no bubbles formed and the results plotted on a semi-logarithmic scale. Some esti- did not differ by more than 10 percent. However, mates for the l-m depth in Tomahawk Lagoon the effects of dilution with distilled water are un- rvere obtained in the same way. be likely to be constant and this procedure must Only the upper portion of the depth profile was considered undesirable. Other more satisfactory obtained in Lake Waipori, so that it was necessary procedures which have been recommended involve to use a different method of extrapolation. The sample, the removal of oxygen from the either by productivity at 0.75 m was determined on only 7 applying a partial vacuum (Steemann Nielsen days. The relation between productivity at 0.75 m 1958) or by bubbling nitrogen through it (Strick- and P."* for these samples is presented in table 3. land and Parsons 1960), though these would cause a reduction of carbon dioxide concentrations, TABLE 3: Depth of P-.. and relation between productivity r¡'hich can greatly influence photosynthesis (for at 0.75 m (Po.ou.) and P... in Lake Waipori. example, Felföldy and 1958). Kalkó Po'ro - Depth of P-"" Precision of L and DB Estimates Date (- ) P-^" Mean The precision of the L and DB method was not 4/tl/65 0 0.83 0.83 calculated. Strickland (1960) has suggested an 10/3/65 0.25 0.626 ideal precision of 20 mg of carbon/m'.day. This 22/4/65 0.25 0.608 0 656 19/lt/65 0.25 0.733 figure was derived on the assumption that the only errors were manipulative and that these were re- L9/B/65 0.75 1.13 Po." - 1/10/65 0.5 0.954 1.0r duced to the lowest level rvhich can reasonably be tt/10/65 0.5 0.926 expected. Although it is not claimed that this As the 0.75 m bottles lay among macrophytæ for much of the experi- degree of precision was obtained in this study, it ment on the single day when tbis depth was sampled with the L and DB method, the result o{ this experiment has not been included in the provides a minimal estimate of enors for Lakes table.

18 When productivity at 0.75 m was uot estimated constant light intensity of 350 foot-candles for clirectly it was assumed to be 83 percent of P."' 4 hours, and one result from Lake Mahinerangi. rvhen P^n* was reco,rded at the surface, 66 percent A subsurface maximum was recorded for both of P-o* when P^o- was recorded at 0.25 m, and rnorning and afternoon experiments only on 12 Pmax recorded at m. equal to P-o* when wâs 0.5 July, B September, and 4 October 1965. The mean Phytoplankton productivity beneath unit surface morning P*u* area of the lake (P I area) was calculated from the for the relation for these was 0.98. unsmoothed profiles. afternoon P-"* The samples incubated at constant light intensity CAI,CULATION OF DAILY PRODUCTION also failed to reveal any differences which might Day length (sunrise-sunset) in Dunedin varies cause asymmetry in the daily production curve, from a minimum of 8.55 hours in June to a maxi- and morning and afternoon experiments were each mum of 15.75 hours in December, so that the assumed to represent half of the daily production 4-hour experimental period used with the 'nC for Tomahawk Lagoon. This result differs from method represents a varying fraction of the daily those obtained by a number of authors, who report illumination, and correction factors for the calcu- that productivity during the morning is generally lation of daily production had to be derived. Five higher than in the afternoon (for example, Doty studies of the diurnal distribution of production and Oguri 1957; Ohle 1958; Vollenweider and were carried out on Tomahawk Lagoon between Nauwerck 1961 ; Vollenweider 1965). and November 1965, the experimental periods July taC Method being: sunrise to 2 hours before noon, 2 hours before noon to 2 hours after noon, and 2 hours The three curves obtained in each diurnal study after noon to sunset. The complete results are pre- were summed, and the maximum in the resultant sented in Appendix IIA. With the oxygen produc- depth profile represents a daily estimate of P-o" tion method, both morning and afternoon experi- (day P-"*). Each of these estimates was dividecl ments were conducted on two sampling days. by the corresponding estimate of P-o* obtained in the 4-hour midday experiment (midday P-u*), L and DB Method and the dividends were plotted against day length. The results for production beneath unit surface The estimates obtained for the sunrise-sunset area were processed in the sarne way (figs. 6 and experimental period in Lakes Waipori and Mahine- 7 The least squares linear regression equations rangi were assumed to represent daily production. ). were: Results for the diurnal oxygen production studies : 0.242 0.156 X in Tomahawk Lagoon are shown in table 4, with Y + and : 0.129 X the morning and afternoon estimates obtained in I' 0.56 + the diurnal studies by the 'aC method. Also in- day P*o" day Pf area cluded in this table are results for a single day on where ts is -. , tsris- which samples were taken at sunrise anel 2 hours midday P-** midday P f area after noon, and exposed in the laboratory to a and X is day length. The standard errors of the

TABLE 4: Diurnal variatim in P",., in Tomahawk Lagoon (mg of carbon,/m5,hour) as shown by a comparison of rates in the morning with those in the corresponding part of the afternoon. Morning P-", lvlorning Af ternoon Date Method P-.' P^., .{,f ternoon P-^' Note

27 /r/6+ L and DB (gross production) 683 599 t.t4 Both maxima at surface 6/2/64 L and DB (gross production) 79 72 1.10 Afternoon maximum at surface t2/7 /65 1lC 9.17 8.90 l 03 t7 /7 /65+ raC(Om) 13.25 13.+7 0.98 14c(0.5 m) 12.57 12.7 s 0.99 30/B/65 14C 0.38 0.54 0.7 0 Morning maximum at surface B/9/65t 14C 0.79 0.84 0.94 +/ t0/65 14C 0.71 0.74 0.96 B/tr/65 14C 1.5 3 2.52 0.61 Both maxima at surface 26/ |t/65 14C 2.09 2.48 0.84 Morning maximum at surface r These samples were incubated in the laboratory at constant light intensity. i Lake MahÍneranei.

19 SE,dSONAL DISTRIBUTION OF PHYTOPLANKTON PRODUCTIVITY

The annual cycles for phytoplankton produc- With the exception of the curves for Tomahawk tivity are shown in figs. B-13, and the complete Lagoon in 1965-66, which will be considered in productivity data are given in Appendix IIA. detail in the section "Interrelations between Phyto-

Gross 02 14c = - P at surface .to ^ max o ' P max not at surface E c l¡o r! (, o E'l E

.JUL JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN Fig. B: Phytoplankton productivity per unit volume of Tomahawk Lagoon for the period July 1963-January 1966 shown as maximum rates from the depth piofiles (P-..). These resule have been correcteã to repreient hourly ratãs for the period sunrise-sunset. See text pages 19 and 20.

Gross productivity x------x Net productivity o 450 - Pmax o recorded 400 at surface E x - o 350 ¡¡ ,,Y tú IJ x o Þ) E

'x,')i

JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG 1963 1964

Fig. 9:. Maximum lrourly rates of gross productivity (P..,) and net productivit), per unit volume of Tomahawk Lagoon fo¡ the period July 1963-August 1964, estimated by the L and DB òxygen proãúction method.

22 plankton and Macrophytes in Tomahawk Lagoon", seasonal distribution will be considered in the all of the curves showed well-defined summer- section "The Relation of Phytoplankton Produc- autumn maxima and seasonal minima in winter tivity to Environmental lìactors"' or early spring. The factors responsible for this

1963-64 Gross 02 1964-65 Gross 02 ^------^ 14C x ------x 1964-65 >------.1965-66 14C

E 150 o ¡l tú u o

\vl

--'L,-.' -..-x x '- X. ..x JUt- AUG SEP NOV FEB APR MAY JUN period 1963- Fic. l0: Phvtoplankton productivity beneath unit surface atea (P/atea) of Tomahawk Lagoon for the July for the period sunrise-sunset. See text pages Jmuury 1þ06. These iesults have been corrected to represent hourly rates 19 and 20.

Waipori Mahinerangi x-x , Pn,,u, ut surface A

m E o

lú u t'o/ o o| E

F A.M.J J.A'S N'D J 1965 1963 1964 Fig. ll: phytoplankton productivlty per unit-^volume of Lakes Waipori and Mahinerangi, at the main sampling stations, for the period November 1963-January 1966 stå*., a, maximum rates from the deptli p.rofiles. ß-".). These results ir;;-bË;-;";".t"d to;p;;"i h;ríy rates for the period sunrise-sunset. See text pages 19 and 20.

23 o À¡t tr o l¡ fit u '02 Gross ,/ o X x x t4c'--"' cD tl È I tl \t \t/ ,xorNet tt lrl \i

N¡ D JIF F r 963 I 964 196 5 Fig' 12: -Phytoplankto-n--productivity-be_leatï,unit_^s^u_rface area (P/arca) -of Lake Mahinerangi ar rhe main sampling station for the period November 1963-November 1965. The'e resrìit" i'""i ¡ãà"-.át'.;;ä'ä;;i;".t rior"iy iät";i;î-til; period sunrise-sunset. See text pages 19 and 20.

fl ll It 5 o 5 li Â ! lt ,\ ô¡ tl/\ È i Gross O2,-. lii Net O¡ x---'x lto |ii 14 r' r! fi o r!r'i i ¡\ o lì o| .* It-. I I E t' \.. I t.- \. I ./ I \r\. I

\'t/ zïllf \.. "\l

NID JIF J ¡F I 963 196 4 I 965 Fig. 13: Phyto-plankton p¡g$rlgtivity. ben_e^atJr unit surface area (P/arca) of Lake 1{aipori at rhe main sampling station for the period November 1963-November 1965. These results have'been dorrected to r"lp.ãì"ii-trã".ìv t.i*'rã"-trr"iãiir¿ sunrise-sunset. See text pages 19 and 20. u ALGAL SPECIES COMPOSITION

INTRODUCTION Changes in species composition were frequently reflected by variations in the phytoplankton pro- Phytoplankton were collected by centrifugation ductivity. A notable example was the sudden end of surface water samples at 1,500 rpm for 10 tc the Anabaena bloom of 1963-64, which was minutes. The relative abunclance of different accompanied by a decline in productivity by a species was determined on a rather subjectil'e factor of 9-10 between the samples of 27 January assessment of cell numl¡ers ancl cell volumes, No and 6 Februarv (figs. B and 10). The increase in cell counts rvere rnadc, and absolute variations are productivity that follorved was eqr.rally striking. reported only u'hen these were very obvious. Within 2 weeks productivity was as high as during the Anabacna l¿7oom. This sccond bloom consisted of a nrixttrre of species, including Scenedesmus TOMAHAWK LAGOON quadricauda Chodat, Ankistrodesm¿¿t spp., Coelas- trum sp., Oocystis sp., Coelosþhaerium sp., and N{ajor features of thc composition of the phyto- Cytclotella sp. (probably C. meneghiniana Kützing). plankton in Tomahalvk Lagoon are shorvn in table 6. The species which formed the blooms in July 1963 and February-N4arch 1964 ancl the dinoflagellate Gytnnocliniurn,'rvhiclt rvas recl, were iden- LAKE WAIPORI AND LAKE MAHINERANGI tified by Dr E. ¡\. Flint. The Anabaena was identified as A. flos-aquae (Lyngbye) Brébisson b1' 'Ihe species composition of the phytoplankton Dr G. A. Prorvse, who examined specimens fron-l rvas generally similar in these two lakes. In contrast the 1966 bloom. to Tomahawk Lagoon no water bloom occurred The species composition of the phytoplankton and there was little qualitative seasonal change in was extremely variable, both from month to month the phytoplankton. The diatom Cyclotella stelligera and from year to year. For example, Anacystis Cleve and Grunow and the dinoflagellate Gymno- (possibly A. incerta Drouet and Daily), which dinium (G. limitatuzn Skuja and Gymnodinium formed a midwinter bloom in 1963, rvas not sub- sp.) were recorded as the dominant algae on sequently recorded and the genera which formed almost every sampling day in both lakes. Gymno- summer blooms were also irregular in their occur- dinium rvas generally the more abundant of the rence. Such variations are characteristic of small two between November and Februarl,, and Cyclo- eutrophic lakes in tenrperate regions (for example, tella was dominant betwecn June and September. Hutchinson 1967). At other times the;' were usuall)' about equal.

TABLE 6: Dominant plankton algae and the occurrence of algal blooms* in Tomaharvk Lagoon during the period July 1963-December 1966.

Jnl A.tg S"p Oct Nov Dec J.t.t Feb Mar Ap. Muy Jnn +e 1963-64 e- Bloom A number of species replaced one -++Bloom-+Bloom - Green algae Anacystis-+* anotherãs dominants Anabaena several species ' 1964-65 -- Green algae ++-- Ankist¡odesmus and. -rê- Bloom - -t+ No clear dominance c.entric diatom - GYmnodinium * Anabaena'

* Smaller concentrations of - green algae

1965-66 - Flagellate *- No clear dominance. Flagellates, diatoms. ' No observations Total concentrations lou' ê- - +e t 1966 No observations - - Bloom Bloom --+e Anabaena Cymnodiniunt * The term "blæm" ìs used in the sense of sulñcieDt conceutrations of algae to cause a marked discoloration of the water.

25 Other algae, which were usually much less Staurastrum spp. abundant, included: Staurodesmus Bacillariopþceae Chlorophyceae Asterionella (f ormosa?) Ankistrodesmus spp. Pinnularis Asterococcus Synedra Arthrodesmus Tabellaria Chlorella Cryptophyceae Chodatella. Cryþtomonas Cosmocladium Euglenineae Cosmørium Euglena Dictyosþhaerium Trachelomonas Gonium Chrysophyceae Kirchneriella Dinobryon Neþhracytium Pseudokeþhyrion Oocystis The algae were identified by Dr E. A. Flint, P e diastrum telr as (Ehrenberg ) Ralfs who examined a number of fresh samples from . Spondylosium Mahinerangi in 1966 and 1967.

26 PHYSICAL AND CHEMICAL CONDITIONS

TEMPBRATURE rarely when the action. Factors Detailed results are in Appendix IIC' Presented se lakes will be of the lakes stratifies thermally, and all three None tions between were usually isothermal, though warming or cool- and lr4acrophytes in lomahawk Lagoon" and ing of the upper few centimetres occurred some- "Indices of Phytoplankton Productivity". Detailed times. All of the lakes froze occasionally, but never results are given in fig. 14 and in Appendix IID' for more than a few hours. Surface temPeratures rarely exceeded 20oc. OXYGBN CONCENTRATIONS SBCCHI DISC TRANSPARENCY Oxygen concentrations, like the temperatures' in The Secchi disc transparency in Lake Mahine- we¡e almost invariably the same at all depths rangi varied from 1.5 to 4.0 m' In Tomahawk all three lakes (Appendix IIB)' At sunrise Lakes Lagoon the transparencT was extremel)¡ variable' Mahinerangi and Waipori were usually 90-100 Readings as lorv as 15 cm wcre obtained during percent saturated lvith oxygen, and Tomahawk the Anabaen¿ bloom of 1963-64, whereas on many Lagoon was often more undersaturated than this. sampling da1,s ¿n.tttg 1965 the disc remained The lowest saturation recorded for Tomahawk visible at the bottom of the lagoon at a depth of Lagoon was 23 percent (2.1 mg/l) for a sarnple 2.5-2.6 m. In Lake Waipori the shallow depth ancl taken at the surface on 6 February 1964 immedi- fairlv high transparency prevented nteasurement ately after the Anabaen¿ bloom of December- (m) (ms/m3)

2'5 601 Tr"nrparency 1963-64 !4 tti_ ü1_1_1-lJ--l I t I"x a TransparencY 1964- 65 x---x t I I ChlorophYll o 1964- 65 t I '< , l/ , ll , lt t 2.0 48 I , t , , , t -x, 1.5 36 \i X.T ,(-x

0.5 12 x r X-X

Months Arrows indicate Fie. 14: Chlorophyll ¿ concentrations (mg,/m3) and Secchi disc transparencies (m) in Tomahawk Lagoon. "t".t itt rvhicÉ the disc was still visible át the bottom of the lagoon' n January. Although no subsurface measurements in the section "Interrelations between Phytoplank- rvere made on this day, respiration in the surface ton and À.{acrophytes in Tomahanvk Lagoon". rvater, represented by the difference between gross In Lake Mahinerangi phosphate concentrations and net productivity in fig. 9, rvas very low. Thc were very low and fairly constant, but in Lake low oxygen concentration probably resul,ted there- Waipori they were higher and more variable (fig. fore from the decay of the bloom in the deeper 15). This difference may be partly due to the water or at the mud-water interface, and concen- shallow dep'th of Waipori, which allows disturb- t¡ations below the surface were likely to have been ance of the sediments by wave action. The turbidity even lower. A summer fish-kill sometimes occurs in of Lake Waipori greatly increased after strong the lagoon, and oxygen deficiency may well be an winds on 5 days when phosphate samples were important factor in this. taken. On these days PO*-P concentrations varied from 5.05 to 8.73 mg/m'. On only one other day IONIC SOLUTBS was a concentration higher than 4.2 mg/m' Chemical conditions in the lakes and inflowing obtained. This was on 18 September 1965, when streams are summarised in table 7. Concentrations 5.95 mg/m' was recorded. Zicker, Berger, and of the major ionic solutes were generally very much Hasler (1956) found that agitarion of experi- higher in Tomahawk Lagoon than in the other mental mud-water systems led to increased lakes, with Lake Waipori having slightly higher amounts of phosphate being rele.ased from the concentrations than Lake Mahinerangi. The influ- sediments. ence of physical and bio,logical factors on chemical Both alkalinity and total hardness are very low conditions in Tomahawk Lagoon rvill be discussed in Lake Mahinerangi. Jolly (1959) obtained lower

*/\ x

Ma h inera ngi a

P04-P ms/m3

1965 Fig. The-c-oncçntrations 15: of _r_eactive phosphorus at the main sampling stations at Lakes Mahinerangi and Waipori for the period May-December 1965.

28 the streams which enter Tomahalvk Lagoon TABLE 7: Rangc of variation in chemical conditions in the three--lak-es, -?nd in ."a il[ä fù"ip*i øi ãu *-pri"l iãtl"*, 1963-66.'The concentrations are in ms/|. WaiPori Tomahawk Mahinerangi Coniour Drainage channel Chemical condition Lagoon Stream Lake Lake Channel pH 7.0-9.8 7.4 6.75-7.3 6.9-7.7 7.4 <5.,2-8.6 1 16-1,000 2 7B-580 95 4.5 2.5-35 9.0 cl- 40*-2 15 Total alkalinity (as CaCOs) 39.3-68 3B,B +.o-7 2 8.1-2 0.8 24 .6 5 80-98 3 0.8-88.6 tr.2 0.9-2.0 0.8-2 6.2 Ca++ 46-80 Mg++ t2.3-24.3 10.8 0.2- 1.0 0.3-2. 1 3.2 POa-P (X 103) 2.1-133 14.6-t24 0.5-3.0 t.7 -8.7 NOg-Nt <0.08 <0.08 <0.08 NOz-N 0.001 <0.001 <0.001 NH+-N 0.003 <0.002 <0 002 Total solids t,t32 29 28 So+- - 319 3.5 4.0 Fe (total) 0.25 0.2 * No ûgure is available for the days when the lowest pH was recorded' Division, D'S'I'R', in Octobe¡ 1964' Results for the three forms of nitrogen, total solids, sulphate, and iron are from analyses bv the Chemistry t from sampling stations' The other figures represent ti" ,".s-" of v"lu"s obtained by the author for a varying number of analyses all pH figures in only one of the 19 New Zealand lakes more variable than in Lake Mahinerangi, and that she investigated. Alkalinity, total hardness, was also generally higher (fig. 17). These differ- winter and pH in Lake Mahinerangi are lowest in ences can be attributed to the influence of water and increase gradually during spring and decline received from the Contour Channel (table 7) and during autumn, though the total range of seasonal residual eflects from drainage variation is small (fig. 16). In Lake Waipori alkal- possibly also to inity and total hardness were slightly higher and water (see page 33). pH ms/l CaC03 7.3

7.2 7.5

7.0 7.0

6.8 6.

6.6 6.0

pH x Alkalinity a Hardness

J J D f966 t964 19 65 and magnesium as mg,/l of cacos) at the main Fis. 16: Alkalinity (as mg,/l of caco"), pH, ald total .ha¡dness (-9]9itm ^ ^iltriii"i-ìoti;; 1964-Januarv t966' "i LakË Mahineransi, December 29 msll cl- pl-l CaCO3 lms/l) 7.j 21

7.5

7.3

7.1 /\ ^/'Å:i^'"" 5.5 6.9 ac t- , It 4.5 t- lkalinity

3.5

2.5 M Months Fig. U: Alkalinity.(as and total hardness (calcium and magnesium as mgll of CaCOr) at the main samplþS. 1965. Samp-les-33. considered to have bern"influenced byïrainage water pumped from the Tai text page

30 SAMPLING ERR.ORS AND REGIONAI, VARIATIONS IN PHYTOPLANKTON PRODUCTIVTTY

INTRODUCTION because of unevcnness in the clistribution of the algae. A vertical unevenness results fror'";' Anabaena To calculate annual or mean figures for the floating to the surface on calm days, and horizontal productivity of a lake from samples taken at a patchiness was also observed. Productivity was single sampling station at regular intervals, two much higher at the surface than at 0.25 m during assumptions are necessary: firstly that the samples this period, so that its sensitivity to variations in are representative of the variations that occur in light intensity would also have been high. the intervals between sarnpling, and, secondly, that the sampling station is representative of the lake as a whole. These assumptions are aPart from any LAKE MAHINERANGI on the validity of the methods used. In Lake h,Iahinerangi the productivity curves Very large day-to-day variations in the produc- obtained with the "C method during winter and tivity of Lake Erken are reported by Rodhe spring were very stable, with changes occurring (1958), who samplecl this lake daily for 3 months systematically over long periods (figs' 11 and 12)' This suggests that the programme of sampling at when it was in sLrmner stratification' There was 'fhe intermittent intrusion of hypolimnial water into the 2-lveekly intervals lvas adequate. estimates epilimnion, and some of the variability was attri- obtained with the L and DB methocl in this lake buted to different water masses being sampled. cluring winter and spring were close to the limits Small-scale spatial variations in the productivity of sensitivity of the method, and no significance of marine phytoplankton have been investigated can be attached to the fluctuations recorded' by Cassie (1962), rvho demonstrated that homo- During summer and autumn, however, when geneity canno,t be expected for samples separated productivity was higher, large fluctuations werc by intervals greater than about 15 cm. These recorded at the main sampling station, which sug- results suggest that sampling errors should be con- gests that fortnightly sampling was not adequate' sidered during investigations of phytoplankton Furthermore, the fluctuations at other stations did productivity, not parallel those at the main station, so that the sampling programme was clearly less than ade- the spatial sense also (fig. 1B). These TOMAHAWK LAGOON quate in variations lvere striking. For example, between 29 The weekly sampling intcrvals used for 1-oma- October and 11 November, productivity at Station hawk Lagoon appeared to be generally adequate 4 increased from 79 percent to 193 percent of the for P-o*, as the variations that r+'ere recorclecl were correspcnding figures for the main station. Simi- usually regular. Although large changes in pro- larly, productivity at Station 3 was 179 percent ductivity occurred from sample to sample, the of the corresponcling value for the main station on direction of the changes seldom differed in con- 23 December, but by 6 January it had decreased secutive samples (fig. B). Short-term fluctuations to 73 percent. These results were consistent for in the Pf area curve (fig. 10) appeared to be trvo depths at each station, two bottles being used larger, and this can probably be attributed to the at each depth. During winter and spring the rela- greater influence of day-to-day variations in light productivitl' different stations tion between ^t intensity on this curve. rvas fairly constant. It appears,'nt therefore, that ;\lthough large fluctuations were recorded when sampling errors may ha.ve been important only sampling was carried out at closer intervals than when productivity was highest. Although this is a week during the Anabaena bloom in January only a small part of the year' it accounts for a 1964, it appears that the same general pattem large portion of the annual production, so that the would have been obtained from rveekly sampling, calculated annual production may have a¡ error and the calculated annual production would not which is disproportionately large. The magnitude have differed greatly. There was reason to expect of this error could be estimated only by more productivitv to be more variable during this period detailed sampling. 3l ¡o= CA Ê,

o .a l! o o Et E 2

A DJ I 965 1966 Fig. 18: Comparison of phytoplankton productivity at different sampling stations in Lake Mahinerangi from August 1965 to January 1966. The solid line joiru the P-.. values obtained for the main sampling station (Statión 1) on dãys when this was compared with others. Other points represent P-a¡ values calculated for ôther sampling stations, usually on the basis of comparison with the main sa,mpling st¿tion at two depths. The locations of th : sampling stations are indiCated in frg. 3.

Station 2, which lies in the uppermost basin of results appeared to reflect the water chemistry at this reservoir, represents a less productive region these stations. Alkalinity, pH, total hardness, and than the main station. In the four comparisons of phosphate were all generally lower at Station 2 the two stations, productivity at Station 2 vaned lhan at the main station, but at Station 3 they did f.rom 24 to 56 percent of that at the main station. not differ significantly from those at the main Results at Station 3 did not differ significantlv station (table B). from those at the nain station for the samples The main source of water in the upper basin, taken in winter and early spring. These early represented by Station 2, is the Waipori River. At

TABLE B: Chemical conditions at difrerent s"-pling stations at LaI

7 /4/65 1 7.1 6.5 2 6.9 5.+ 20/6/6s I 7.t 5.9 r.27 2 6.75 4.0 0.97 26/B/65 I 6.75 5.7 o.zi 2 6,75 5.15 5.5 t3/t0/65 I 7.15 6.0 6.65 2 7.05 +.95 5.15 29/10/65 1 7.o5 6.0 + 7.05 5.t tr/tr/65 I 7.1 6.3 + 7.0 5.5 12/5/65 I 7.t5 6.5 3 7.t5 6.7 9/B/65 I 6.75 6. l5 3 6.75 6.15 ?3/t?/65 1 7.1 6.2 3 7.t 6.4 6 7.0 6.5 7.2 6.2 6/r/66 I 7.t 6.4 j 7.t 6.3 5 7.1 6.3

32 the main station this has been mixed with the 9 days of pumping. Water from this source ap- smaller inflow of the Nardoo and Lammerla.w peared to vary, both in its distribution within the Streams and probably also from Northwest Stream. Iake and in its influence on the phytoplankton No other large streams flow into the lake above productivity (table 9). Although the general sig- Station 3, so that these early results suggested that nificance of drainage water could not be assessed one or more of these streams may carry potentialll' rvithout more detailed knowledge of its distribution more productive water than the Waipori River. at different times, these results suggest that its net Alkalinity and pH at Station 4 appeared to be effect on the annual production of phytoplankton between the levels obtained at the main station rvas probably slight. None of the effects was large and those at Station 2, and this is consistent with in relation to the differences that were founcl be- its location. Productivity, however, was inter- tween sampling stations when neither appeared to mediate only in the first of the two samples from be influenced (15 J"ly) or when both were equally (1 September). Furthermore, t Station 4, and it is clear from the second sample influenced and those taken subsequently from Station 3 that the short retention time for the lake water Pre- ) at least at times of high productivity it was not vented drainage water from accumulating within variations in alkalinity or one of its covariates that the lake. * governed variations in productivity. the drainage channel are I Chemical data for t . shown in table 10. The samples of lake water con- i LAKE WAIPORI siderecl to be influenced by drainage were those i In Lake lVaipori there we¡e also large variations having chloride concentrations higher than 7.8 ,I in productivity between the three sampling mg/I, and those having a concentration of 5.3 stations. Productivity at Station 2 and Station 3 mg/l or less rvere considered to be no,t influenced. varied respectively frorn 77 to 212 percent and This distinction, though somewhat arbitrary, was from 59 to 160 percent of that at the main station. based on a natural division in the values obtained, lt appears that these variations were at least partl1' and it appeared consistent with the relative due to the influence of the drainage water rvhich chloride concentrations of the Waipori River (4.5 is pumped into the lake. Pumping rvas done more mg/1, one sample ) and the Contottr Channel (9.0 fre quently from about the time that I began mg/l, cne sample) and the observed relative flow sampling at different sampling stations, ancl none rates. Total hardness and alkalinity provided a of the 11 days on which different stations rvere check. The small floating vascular plant Lemna sampled followed pumping by more than 3 days. minor L. grew in the drainage channel, and its Previously only one sample had been taken within piesence sometimes provided visual confirmation

TABLE 9: Comnarison of Þhytoplankton productivity at differ¿nt sampling stations on Lake lVaipori and the corresponding chloride concentiations. (PÎryíopiankton pioductivity-at the station influencid o_r most stronglyin-flu_enced by_drainage water-is expressed as a percentagè oi tlie produc-tivity at the other station, a mean value being used for the two depths compared') Productivity S ta tions Chloride at Stations not Chlo¡ide at A influenced stations influenced stations not Herbicide (station No. ) influenced (station No. ) influenced B in I 965 (A) (ms/l) (B) (ms/t) (%) channel

1/+ I (possiblyinfluenced) 2 Bl No 2t/5 I (possiblyinfluenced) 2 B0 Yes 2/6 3 (possiblyinfluenced) I 59 Yes 30/6 1 2 4.3 76 Yes 15/7 2 2.5 77x Yes I 2.5 2 2.5 47 Yes 2B/7 1 7.8 tg/B I 7.8 2 90 No No 1/9 1 13.1 :u 63t 3 12.l 2+/10 I 8,4 2 3'.2 116 No 4/tt I 22.7 2 3.5 90 No tg/tt 3 8.9 I 5.3 132 No * Station 2 Ì Station I

Station 1 Station 3 wo eJi-.tì" of chloride oititii-h-"r¿"."s were obtained on 1 April, 2l M.ay, or 2 June. The frgures for alkaliuity indicated that otre station may have been influenced by drainage or influenced more strongly than the other.

33 i

I \ TABLD 10: Chemical conditions in tåc drainage water which but owing to the variability o,f chloride in the is pumped inø Lake Waipori from the Tãieri Plain. channel accurate calculations were not possible. Total Total alkalinity hardness Chloride A further complicating factor was the addition Date pH (msll CaCOg) (mg,zl CaCOs) (mg,/l) of herbicide to the drainage channel between May 22/+/65 7.6 t70 and to control the growth of aquatic weeds. 16/6/65 4.6-5.2 July 30/6/65 4.6-5.2 : . irð This caused the low pH values shown in table 10 t5/7 /65 6.5 53.9 2B+ and also appeared to kill the phytoplankton, as 2B/7 /65 6.4 40 390 256 r/9/65 7.2 there were almost no algae in the channel through- 2t/9/6s 7.5 183 : : r,doi out this period. During these months the drainage tt/lo/65 7.7 190 568 804 2t/10/65, 7.8 110 water was only slightly inhibitory to phytoplankton 4/tt/65 8.05 215 :: dß productivity after dilution within the lake. By 24 lB/tt/65 8.55 October a phytoplankton crop had again developed lhat a sampling station was influenced by drainage in the channel. In the three subsequent tests the water. The chloride concentrations suggest that at drainage water appeared to be inhibitory at the the stations influenced about 3 to 10 percent of highest level of addition and stimulatory at the the water was derived from the drainage channel, lower levels, though neither effect was large.

34 THE RELATION BETWEEN I4C AND L AND DB ESTIMATES

In both the 'nC and L and DB methods samples and subsequent investigations by Fogg and his have confirmed that this may sometimes are enclosed in bottles during the experiments, and associates t'C chis may result in "bottle errors" of various types be an important source of error in the method (Smayda 1957; Doty and Oguri l95B; Pratt and (Fogg, Nalewajko, and Watt 1965; Fogg and Nalewajko 1966)' Rup- Berkson 1959 ; Vollenweider and Nauwerck 1 961 ) . Watt 1965; Watt 1966; It has also been suggested that minor clifferences in ture of cells during filtration may also contribute the handling of samples may influence the photo- to these losses (Arthur and Rigler 1967)' synthetic characteristics of the algae (Cassie 1962 ) . The washing technique used for the removal of Because of these difficulties neither method pro- inorganic 'aC from the filters in the present study vides a completely accurate estimate of produc- (page 17) was rather severe and this may have led tivity in the waters sampled. Physiological factors to some leaching of organic 'nC from cells on the influencing the interpretation of 'nC results have filter and caused 'nC assimilation to be under- been reviewed by Fogg ( 1963 ) and Thomas estimated. Two washes were required to obtain ( 1963), and the interpretatior^ of both 'nC and L quantitative transfer of the phytoplankton to the and DB results is reviewed by itrickland (1960). filter with the pressure filtration s)'stem used in Both methods apparently have several sources of the early experiments, and this method was re- error whose influence Ûlay l-,s variable, so that tained when the vacuum filtration system became only an approximate agreement can be expected. available so that all of the 'nC results would be methods decontamination For the few samples in which the methocls were comparable. Various of include compared directly in Tomahawk Lagoon the L have been used by different workers. These or with and DB method gave estimates of net productivity rvashing with formalin (Goldman 1963) that were higher than the productivity estimated acid in varying strengths (see McAllister 1961), fumes (Steemann by'nC assimilation (table 11). As L and DB esti- exposure to hydrochloric acid and no de- mates of net productivity might be expected to be Nielsen 1952, 1964; Wetzel 1965b), too low, owing to the respiration of heterotrophic contamination at all (McAllister 1961). Some have been desirable organisms within the bottles (for example, Nelson form of acid treatment may and Edmondson 1955; Pratt and Berkson 1959)' for the samples taken from Tomahawk Lagoon the pH was high, owing to the these results suggest that 'aC estimates rePresent during 1965, when precipitated the light less than net productivity. Similar results have pcssibility of 'oCO, being in Wetzel been obtained by a number of other workers in- bottles (Goldman and Mason 1962; cluding Vollenweider and Nauwerck (1961), 1e65b). 1aC McAllister et al. ( 1961 ), Antia, McAllister, When Pfarea is considered, however, the Parsons, Stephens, and Strickland (1963), and results will not necessarily be lower than L and Barnett and Hirota (1967). It has been suggested DB estimates for net productivitl'. The negative that a significant portion of the assimilated 'aC bias of the latter, resulting from heterotrophic may be excreted as soluble organic matter and respiration, becomes increasingly important as lost in filtration (FogS 1963; Antia et al. 1963), Iight intensities decline from saturating levels, and

TABLE ll: C,omparison of results from the laC and the L and DB oxygen methods for 4-hour experiments in Tomahawk Lagoon' 14C t4C Depth Gross 02 Net 02 14C Date (*) (ms C,/m-3) (mg C,/ms) (mg C,/mS) Net Oz Gross 02 r+/9/64 o 320 290 115 0.40 0.3 6 0.5 170 140 67 0.48 0.39 2/12/64 0 380 360 336 0.93 O.BB 0.5 225 200 150 0.75 0.67 0.5 760 sBB 0.95 0.77 8/3/65 o 26/7/65* 0 1B ::: 0.50 0.5 6 8.9 1^48

* Oxygen production values are t'ery close to tbe limits of sensitivity of tl¡e method

35 for a complete water column this error will tend to sequently obtained with the method appeared tnC. "C cornpensate for any excretory losses of In to be generally comparable with both of them Lake Mahinerangi the compensation depth, below (fig.13). which nct oxygen production is negative, wffi It was not considered rvorth while to compare generally about 3 m, though "C generally con- lhe trvo methods directly in Lake Nlahinerangi or tinued to be assimilated to a depth of 6 m. The Lake Waipori, as the L and DB estimates were results in fig. 12 suggest that '1C estimates for frequently close to the limits of sensitivity of the P f arca lay between gross and net productivity as method. A similar pattern rvas obtained with the estimated by the L and DB method. A similar two methods for both the depth distribution of situation was found in Tomahawk Lagoon, though productivity and the seasonal distribution, but no Pf area estimated by the L and DB method was attempt could be made to equate the values less frequently negative than in Lake Mahinerangi. obtained. Although the direct comparisons between In Lake Waipori only the upper portion of the the two methods for Tomahawk Lagoon gave euÞhotic zone is represented, so that net Pfarea, variable results, the variations were small in rela- estimated by the L and DB method, was only tion to the total variation in productivity for the slightly lower than gross, and the estimates sub- lagoon.

36 INTERRELATIONS BETWEEN PHYTOPLANKTON AND MACROPHYTE,S IN TOMAHAWK LAGOOI\

INTRODUCTION Figures B and 10 indicate that throughout most of the final year of study phytoplankton productivity in Tornahawk Lagoon was much lower than in the previous 2 years. As an illustration of the magnitude of the decline, mean productivities for nutrients, and the interrelation might be governed the period 15 Ðecember, for which 3 years' July-31 directly by one or other of these or indirectly by rcsults are available) are presentecl in table 12. other factors. IABLE 12¿ Phytoplankton productivity -in Tomahawk Lagoon for the peiioä July-Decèmber in- the ,3 yea.s 1963-65 LIGHT PENETRATION " (mean hourly iatés for the daylight hours). P*-- P/arca Year Method (mg C,/m3.hr) (rngC/m2.hr)

1 963 L and Dll 98.6 (net) 48.3 (gross) 1964* 14C 42.3 3t.2 1965 14C 2.3 1.6 * The 1964 means include two results obtained with the L and DB oxygeu method. were rccognisable in these data: the period rvhen dominant (J"ly 1963- The difierences bet\t¡een the means for 1963 -Decemberphl,toplankton were the transition period (December and those for 1964 were probably largely related 1964), 1965), and the period when macro- to thc change in the method of measurement (see 1964-April 1965-April 1966)' table 11). The decline in phytoplankton produc- phytes were dominant (April coincided with the development of tivity in 1965 The Period of Phytoplankton Dominance a large crop of the macrophytes Myrioþhyllum elatinoides Gaudichaud-Beaupré and Ranunculus Detailed depth profiles for phytoplankton pro- are presented in Appendix IIA. Before fluitans Lamouroux. In 1963 and 1964 there were ductivity no large crops o{ macrophytes in the lagoon. Emer- November 1963 gross phytoplankton procluctivity 1 percent gent patches we re first observed in the more at 1 rn had usually declined to less than shallow regions on 1B January 1965. Furtl-rer of P^"*, and it was rarely cletectable. Between 18 growth ¡vas evident until mid April, wllen macro- November and 16 December 1963 the Secchi disc phytes had emerged over about 20 percent of the surface of the lagoon and had reached to within about 30 cm of the surface in all but isolated patches and an area of about 2,000 sq m near the sampling station where the lagoon has been December the transparency decrealed shatply, and too deepened by dredging. There appeared to be little app es at 1 m were again change in the distribution of macrophytes fron't low esis bY the PhYtoPlankton' April 1965 until April 1966, when regular obser- Thi , rvith the excePtion of vations were discontinued. The algal blooms which isolated sampling days, until June 1964. had characterised the previous summers did not occur in 1965-66 and though no estimates of phytoplankton productivitl' ry... made after 6 January 1966, algal populations appeared to remain very lorv until April. At all times during this investigation, therefore, to have been limited by low light intensities be- there were large crops of phytoplankton or of tween mid November and mid December in 1963, macrophytes, but not of both together, and the this period may not have been long enough to phvtoplankton productivity declined as the macro- permit a large crop of macrophyte to become

37 established before the transparency decreased Similar curyes were obtained in November of both again in late Decembcr. It appears that light con- years. In December 1964, during the early stages ditions may have been favourable for the growth of the dinoflagellate bloom, the Secchi disc trans- of weeds from June 1964, though they did not parency increased to values higher than any pre- become dominant until some months later. viously recorded. The depth profiles showed a Strong, though indirect, evidence that the low corresponding change, so that the rate of decline transmission of light rvas due to the density of in productivity u'ith depth was lower. Produc- phytoplankton is provided by the inverse varia- tivities remained relatively high at 1 m, and the tions of chlorophyll ¿ and Secchi disc transparency higher light intensities which permitted this ma1' in fig. 14. Macrophytes may therefore have been also have permitted the initiaÌ growth of macro- limited largely by an inability to compete with the phytes, or induced more rapid growth by any phytoplankton for the available energy small crop that had become established earlier. light 'Ihe during this period, In Lake \tindermere it has pH increased sharply between mid November been found that the greatest depth at which and late December 196a (fig. 20), and this is aquatic macrophytes can grow is inversely related likely to have been largely due to photosynthetic to the abundance of phytoplankron in the epilim- removal of carbon dioxide by macrophytes, as the nion (Pearsall and Ullvott 1934). phytoplankton productivity increased little during this period. The Transition Period The decrease in transparency in December 1963 Differences in the depth profiles of phytoplank- was related to the occurrence of an Anøbaena ton productir,{ty between the transition period bloorn. In the following summer Anabaena occurred (December 1964-April 1965) and the correspond- only briefly toward the end of the dinoflagellate ing period of the previous year are illustrated by bloom i¡ lebruary-March 1965. Although its the selection of depth profiles shown in fig. 19, occurrence was marked by a reduction in the rvith the corresponding Secchi disc transparencies. transparency, this was comparatively slight and it

ocT APR-MAY

1 1 1011164 zrslslæ I 1.zzlsl64 \zsl1zl64 I I t 64 \ 0.25 \ I x I I I /l I I o.¡ x I fct x o t o I t I I I I I , /t I I I I l.6m 1.0 01 400 0 1020304050607080 mg of carbon/m3.hou,

Fi s of l: 1963-64 curves ll8 November. 2: Mty). The horizontai bu.r r"p."."ní c tr productivity obtained with the L and 964

38 pH Alkalinity 1964'ñ5 Total alkalinitY r f 0.0 1964-65 pH x pH 1963'64 ^

I I I 1964-65 \ll

1964-65 X-X-X t li i!Ðc^"4---^.A

7.0 30 l0'0 1965-66 Total alkalinitY o pHx

7'0 30 soN Months curve Fis. 20: Alkalinity (as mgll of CaCG) and pH of Tomahawk Lagoon. The last seven pH values in the 1964-65 Íepresent minimaÌ estimates.

le at the lasted for only 2 or 3 weeks. Moreover, macro- May 1965 the dis a. There phytes were by this time well establishecl and had bottom of the lag gro*n upward to a depth where light intensities was a concurrent ations ol could be assumed to be still fairly high. chlorophyll a. The 1964-65 curve fot P.u* startecl to diverge CHLORIDE (TABLE 13) As chloride is not a major nutritional requirement for algae, chloride concentrations provide an was not so great initiallY. index to the influence of some abiotic factors on the chemical environment. Evaporation and the addition of wind-borne chloride would increase The Period of Macrophyte Dominance the chloride concentrations; inflow from the more source of Secchi disc transparencies continued to increase saline No. 1 lagoon is another potential as the growth of macroph)'tes continued. After increase, though this was not observed during the

39 study. reasonable It is to assume that rainfall on TABLE 13: -Chloride, calcium, and magnesium concentra- the lake surface would have reducecl tions in Tomahawk Lagoon i-g/l). the concen- Calcium trations, and replacement of lake water by water Date Chloride Calcium (max.)* Magnesium from the stream would have had a similar effect. 5/10/641 500 88.6 132 12.3 Chloride 25/l/65 2,500 concentrations decreased from Januarl, (No. 1 Lagoon) 1965 until the end of sampling in Januai.y 1966. 25/t/65 600 22/2/6s 530 Although this might have influenced the species 22/3/65 57i composition of the phytoplankton, it seems unlikely 29/3/651 56.s 40.0 that it would have brought 6/5/65 49s about the large decline 3l/5/65 505 in productivity which was recorded, and. chloride 1s/6/65 435 28/6/65 3{0 changed little during the initial d.ecline in phyro- s/7 /65 327 3+.0 3.6 23.3 plankton productivity. The decrease in chloride 12/7 /65 32.0 2.3 23.8 concentration was particularly 19/7 /6s 317 32.0 1,5 24.3 rapid in June after 2/8/65 305 32.8 +.6 22.4 heavy rainfall on 30 ancl 31 May and further rain 2-3/8/65 291 31.6 1.3 22.6 23/8/65 (stream) in (fig. 21). 95 11.2 10.8 June 16/9/65 276 30.8 b.bz 17.0 28/9/65 282 pH AND ALKALINITY (FIG. 20) t9/10/65 292 30.8 o.97 27.g B/tI/65 297 Before December 1964 the pH of the lagoon was 22/11 165 300 3/l/66 275 normally between 7.0 and 7.7, and was higher * Saturation values fo¡ iouic calcium. Tbe calculation of these is than this only at times of high phytoplankton pro- illustrated in Apoendix lE_ i Ä,nalyses by Cbèinistry Division, D.S.I.R.

Rainfall (cm)

pH tt8o"*91-

PO4 - P (nrs/m3¡ ^ Pmax (mg C/m3.hour) 10 60 Cl- (mg/l) x pH

94010

30 / a---r-a_ ,, I 820 t

10 \¡ 7 ^-^ 17 71421 285121926 May Jun Jul Fis' 2t: Rainfall. ionic soltttes, and phy[oplankton productivity-in Tomahawk Lagoon phosphate in May-July 1965. The large increase in concentrations'*u, á..útnåd to huvL occurred'fràm tB M"y, when_aerial topdressing rvas carried out in the u,ith superphosphate north-eastern end of the drainage ¡uri".-fllã irit'i"1"à.-i* j"iv'rãpi"*ïttminimal estimates.

40 ductivity. During the transition from dominance creasecl, and the amount of calcium which could by plankton to dominance by macrophytes pH remain in solution showed a corresponding de- increased, and it remained at or above 9.0 through- crease. Iìowever, much of the calcium remained out most of 1965. A decline below pH 8.4 occurred in the water, probably as colloidal calcium car- only in June 1965 and coincided with a rapid bonate (Ohle 1952). Even if this was unavailable decline in chloride concentrations aJter heavy rain- to the phytoplankton, it appears from the evidence fall (fig. 21). The total alkalinity increased from revierved b1' Ketchum (1954) and Lund (1965) September to December in both 1964 and 1965, that the ionic concentrations present would have and it did not differ greatly in the 2 years. The been ample. It also appears unlikely that mag- single estirnate from the stream suggests that mix- nesium levels would have been limiting. ing of the two waters would have had little effect PHOSPHATE (FIG. 22) on the total alkalinity. Concentrations of phosphate showed a ver); High pH may have a number of indirect effects wide range of variation in the lagoon (2-133 mg on algae, including an increase in the toxicity of of POo-P/m'). The high concentration on 31 N4a1' ammonia (for example, Rodhe 1948), and a 1965 was produced by agricultural topdressing decrease in the amounts of carbon avaiìable for rvith superphosphate in the north-eastern end of photosynthesis. These might have adversely affected drainage basin of the lake on 28 Nzfay 1965. the phytoplankton, but plankton bloorns are the was spread by aeroplane, and widely reported to occur at high pH levels, and This sr-rperphosphate some drift over the lagoon was rePorted' Hearl' pH and carbon dioxide are not generally con- rain rvhich fell on 30 and 31 l\{a,v may have caused sidered to be important limiting factors for algae considerable leaching of phosphate into the lagoon. cven at the levels recorded in Tomahawk Lagoon The added phosphate rvas rapidlv removed fronr during 1965 (for example, Lund 1965) . Scenedes- the water. Within 2 rveeks PO'-P declinecl frorn mus quadricauda, a species which occurred in the 71 mg/m' to lI.7 mg/m'. The decline in chloride Iagoon in 1964, can utilise bicarbonate (Osterlind concentrations during this period shows that there l9+7, 1948) so the absence in 1965 of this species ; rvas considerable replacement of lake water by at least was clearly not due to the carbon supply stream water, and as the stream had a very high being inadequate. concentration of phosphate rvhen tested during a method was used in The nutrient fertilisation flood on 28 June (124 rrrglm'), the total removal one experiment to test the effects of lowering the of phosphorus rvithin the lake was probably greater pH. Samples were taken on 2 March 1966, when than the decrease in conceutration inclicated. The the pH was 9.1. In the experimental bottles it was relative importance of macrophytes, phytoplank- lorvered to 7.2 by the addition of 0.8 ml of lN ton, bacteria, and inorganic processes in the re- hydrochloric acid. Although no tests rvith 'nC were moval of the added phosphate is not known. Phyto- carried out, by 16 i\4arch, when the experiment plankton productivity increased brieflv some weeks rvas ended, there had been no obvious quantitative later, and the phytoplankton may have derivecl or qualitative changes in the phytoplankton of the some benefit. A similar rapid removal of phosphatc experimental bottles or the controls. Although this added to natural rvaters and a lag in the response result can hardly be considered conclusive, the by plankton algae are rvidell' reported (for ex- total available evidence does not suggest that the ample, Einsele 1941; Smith 1945; Pratt 1949). reduction in phytoplankton productivity was deter- However, large changes occurred in all of the mined b), th. change in pH. Hasler and Jones chemical factors measlrred in Tomahawk Lagoon (1949) found that phytoplankton populations during this period (fig. 21), so that the increase were much lower in experimental tanks containing in phytoplankton productivity could not be un- macrophytes than in those without, though pH equivocally attributed to the added phosphate. varied little from 8.4. Although the phytoplankton productivitl, increased, the highest level reached was cornparable CALCIUM AND MAGNESIUM (TABLE 13) only rvith the lowest of the preceding years, when Both calcium and magnesium are essential plant there were no large crops of macrophytes present. nutrients. As a result of the increase in pH during Phosphate increased from October 1965 to early 1965 the concentration of carbonate in- Nt[arch 1966 and reached high concentrations for 4l P04-P ^s/^

M 1965 1966 Fig. 22: The concentrations of reactive phosphorus in Tomaharvk Lagoon in 1965-66. S: Concentrations in the inflowing stream. an unpolluted lake, though no evicl-ence of further crease in phosphate was recorded (28 hours), than pollution was found. There was no more agricul- during November-December, when the concentra- tural topdressing, and the concentrations of phos- tion increased rapidly (26 hours). During 1965 phate in the stream, rvith the constancy of the the high pH of the water may have allowed the chloride concentrations in the lake, indicate that liberation of phosphate through the hydrolysis of the stream had little influence during this period. ferric phosphate (Cooper 1948). In experimental Of the other possible sources of the added phos- mud-r,l'ater systems from Lake Windermere, Mack- phate, regeneration from the sediments provides ereth (1953) found that the concentration of a more likely explanation than decay of the macro- phosphate in the water in equilibrium with mud phytes. If the macrophytes were the source, a net increased regularly from 1 mg of POo-P/m' at decline in these would be implied, ancl- this would pH 7 to about 100 mg/m' at pH 10. There lvas no not normally be expected during the spring grow- direct relation between PO'-P and pH in Toma- ing season. Phosphate ions diffusing from lake hawk Lagoon, but equilibrium is hardly to be sediments may be precipitated as ferric phosphate expected under natural conditions. on reaching the oxidised microzone at the mud- The presence of 3-7 mg of POn-P/m' during rvater interface and thus be prevented from enter- August and September and of higher concentra- ing the n'ater (Nlortimer 1941, 1942). The expo- tions later suggests that phosphorus was not a sure of deeper sediments resulting from dredging limiting nutrient throughout this period. The con- of the lagoon may have aided the liberation of centrations during December were within the opti- phosphate, though the dredge was operated for a mum range suggested by Hammer (1964) for longer period during July-Âugust, when no in. Anabaena flos-aquae, and water temperatures were

42 therefore does not pro- also close to the suggested optimum. Although this The available evidence reduction in species was recorded in high concentrations in vide any likely explanation for the the fact other summers, it did not occur in 1965-66. phytoplankton productivity, apart from ifrat il was related to the Presence of macrophytes' Direct inhibition of the algae by some metabolite NITROGEN AND POTASSIUM Nitrogen and potassium were not measured in the lake water. No response \vas obtained in a fertilisation experiment conducted between 22 N{arch and B April 1966, in rvhich 500 mg of gated, and it has been asserted that the algae may be inhibited at timcs (Hegrash and Matvienko 1965 ). able. ) phytop days earlier was 133 mg of PO,-P/m'. of one phate, calcium, or magnesium. DISCUSSION Conditions that might favour a return to dominance of the lagoon by phytoplankton are stron€f Hasler and (1949) rePort that Jones Phlto- winds with heavy rain. Damage to the macro- plankton populations were much lower in experimental tanks which contained macrophytes than in those without. Similar effects have been noted by a number of other workers and it appears that the decline in phytoplankton productivity in Tomahawk Lagoon was almost certainly related origin, and the lake water, in some way unsuitable for the growth of algae owing to the presence of macrophytes, is partly replaced by unaffected stream water. As a result the phytoplankton ma1' develop, which causes a further increase in thc turbidity. The combined cffect of these changes will be to reduce the light energ'y available to the short periods when the light penetration increased macrophytes. A minimal light intensity must exist, before December 1964. However, the accumulation for the macrophytes maintain themselves by photo- of phosphate in the water in the latter part of 1965 synthesis. If light intensities remained lower than indicates that it was not inability to compete for this level for long enough, there would be an in- this nutrient which limited the phytoplankton. ft crease in nutrients in the water through decay ancl also appears unlikely that they were limited by autolysis of the macrophytes. This would in turn of calcium or magnesium or by direct or deficiency favour more plankton development, which would indirect effects of the high pH. The experiments further reduce the light energy available to the with nitrate and pota.ssium do not allow any con- macrophytes. In this way dominance by the phyto- clusions to be drawn on whether these nutrients plankton might be restored. The changes of this were limiting. nature which occurred in June and July 1965 Another possible explanation is that once the were apparently not sufficient to allow this postu- macrophytes became established they retained lated synergistic process to begin. Active growth dominance by successful competition for the avail- by the macrophytes was indicated by the rapid able light energ)'. However, macrophytes were return to high pH levels, and the macrophvtes never emergent over more than 20-30 percent of quickly re-established dominance. the lake surface, and over the rest of the lake there appeared to be typically about 30 cm of cleal Black swans, Cygnus atratus (Latham), might water above them. During 1963-64 the upper 30 also be an important factor in the decline of the cm usually accounted for most of the phytoplank- macrophytes. Up to 200 of these large bircls arrivc ton productivity beneath unit surface area' at the lagoon each year cluring I\{a1', anrl most of

43 them leave again in July and August. The damage a decrease in the nonliving component of the done to the r-nacrophl'tes b1' their feeding may rvell seston. Thc depth profiles for phytoplankton pro- be significant. ductivity indicate that there rvas probably suf- In 1964-65 the developmenr of rnacrophytes ficient light available to allorv some growth of coincided with a dinoflagellate bloom. Members macrophytes even before the dinoflagellate bloom of the Tomahawk Lagoon Improvement Society, developed. The establishment of macrophytes rvho dredge the lagoon, have reported that the might be expected to reduce the turbulent mixing occurrence of Myrioþhyllum has previously coin- of the water immediately above the sediments and cided rvith "red \,r,ater" blooms in summer, and so reduce the entry of detritus into the open water. they attributed the red colour of the water to the This might explain the increase in transparency. pollen of Myrioþltyllum.In 1966, after the macro- Whether the macrophytes continue to grow may phytes had declined between April and November, then depend on the unknown factors which in a bloom of Anabaena was observecl on I December. some years favour the dincflagellate rather than By 30 December a dinoflagellate bloom rvas in Anabaena or other algae that greatly reduce the progress, the transparency appeared to have in- transparenc), apparently by attaining greater creasecl greatly, and there rvas again development population densities than the dinoflagellate. of Myrioþhyllum elatinoides and Ranuncu.lus f.ui- Although the domination of the lagoon alter- tans over much of the basin. There is therefore nately by phytoplankton and by macrophl,tes is an some evidence that the initial development of large irregular rather than a seasonal phenomenon, the crops of macroph)'tes may generally coincide with changes in dominance might be confinecl to specific dinoflagellate blooms. As noted previously, neither seasons. In 1964-65, 1966-67, and possibly in some occurred in 1963-64. The 1964-65 results slrggest earlier )¡ears the large weed crops developed in a pcssible reason for this correlation. The water summer. This ma1, have been brought about merely became substantially.more transparent during the by light intensities becoming high at these times, eerliest stages of the dinoflagellate bloom, and this or there may be a requirement for high tempera- would no doubt have favoured the growth of tures as rvell. No observations were made during a period when phytoplankton became dominant macrophytes. The phytoplankton crop, as indicated and the rveeds declined, but this change is more by the concentrations of chlorophyll ø at the sur- likely to occur in winter if it is brought about by face, became denser during the initial increase in the synergistic processes which, it is postulated, transparency in December 1964, and this suggests may be initiated by storms, or if damage done to that the increase in transparency \vas produced by the macrophytes b1' slvans is the major factor.

44 ANNUAL PRODUCTION

INTRODUCTION plankton crops present, and this largely compensated for the lorver P.o*. Ihis effect is r^¿ell knolvtt of phytoplankton productivity in A comparison in lakes, (for example, Ruttner 1953, p. 14-7)' The other the Otago lakes with that in some lakes in shallow depth of Lake \Vaipori prevents the low presented table 14 a generally countries is in in P,o*- levels from being compensated by any con- productivitl,. Figures for descending order of sequent increase in the depth of the euphotic zone, Tomahawk, Waipori, and Pf area and P-n* for but it allows the growth of periphyton and macro- weighting the Mahinerangi rvere obtained by phytes, whose contribution to the primary pro- varling intervals calculated daily values for the ductivity of the lake during their seasonal occur- between samples. rence is not kuown. Similarly, in Tomahawk Lagoon during 1965 macrophytes contributed to COMPARISON OF TOMAHAWK LAGOON, the primary production, and the contribution of LAKE WAIPOR.I, AND LAKB MAHINBRANGI phytoplankton was likely to have been of onll' minor significance. During the latter part of 1965 In Tomahawk Lagoon Pmax wãs initially very P area was similar in these two lakes and lower higher than was in the other lakes, though f much it than in Lake N4ahinerangi by a factor of about 3. the lagoon after macrophytes became dominant in Although an investigation of the productivity of Figure 11 indi- all three lakes were comparable. rnacrophl,tss in Lake Waipori and Tomahawk autunn of 1964' cates that during the summer and Lagoon rvas considered desirable, this was not when the and DB method was used, Poax wíì.S L possible in the present study. Parallel investigation \4ahinerangi than in generally higher in Lake of the productivity of ph1'toplankton, periphyton, Subsequently, rvhen the'aC method Lake Waipori. and macrophl,tes in a lake appears to have been was reversed. appears un- was used, this result It carried out onl;, bv Wetzel (1964). likely that this change was produced by the change in methods, as s)'stematic differences betrveen the L and DB and 'nC methods might be expected to COMPARISON OF THB OTAGO LAKES apply equally to both of these lakes owing to their WITH LAKES IN OTHER COUNTRIES composi- similar water chemistry and algal species No results have been included in table 14 lot of a systematic dif- tion. Because of the possibility experiments lasting more than 24 hours, though ference the two methods, it is not known between el'en with this restriction, r-esults are likely to have was produced by an increase whether the change been influenced by the starting times and experi- decrease Lake Mahine- in Lake Waipori or a in mental periods used by the different authors. liur- obtained from direct rangi, though both the results ther limitations are imposed by differences in the Tomahawk comparison of the two methods in experimental techniques used and differences in of the environ- Lagoon and the greater variability the corrections applied to raw data. In addition, suggest that an increase in ment in Lake Waipori it can be assumed that the significance of sampling be the more likely ex- Waipori after 1964 may errors is variable. Because of these difficulties only sampling interval, planation. Even with a 2-weekly an approximate equivalence between the different errors are likely to be important holvever, sampling results can be assumed. Where necessary, units were frequently in these lakes. Sampling intervals have been altered by using a photosynthetic greater this when the L and DB method was than quotient of. I.2 and a standard day length of 12 relative change may not have used, so that the hours. Errors introduced by this are unlikely to be as large as fig. 11 would suggest. been large in relation to other differences. Some of the Before the development of macrophytes Toma- figures in table 14 have been abstracted from pub- hawk Lagoon was only about three times as pro- lished graphs, and these may not be precise. Many ductive as Lake trIahinerangi when compared on of the European lakes listed in table 74 freeze, so a basis of. Pf area (L and DB gross). This was due that even those considered to be eutrophic may to the euphotic zone being much more extensive have very low minitna of phytoplankton produc- in Lake Mahinerangi as a result of the smaller tivitv. Consequenth', where annual productivities

45 TABLE l4r Ph¡oplankton productivity in some lakes of different countries. Lake Latitude Pmar rangê Annualmean P/arearznge Annua.lmean Referencg method, and (") (mgC,/m3.hr) (mgC/m3.hr) (mgC/rr.z.day) (msC,/m2.day) remarks

Ayyangulam, temple c.l3 6,000-1 1,000 Sreenivasan ( 196a) ; pond, Madras State, L and DB; 5 samples India

Victoria, Kenya- 0-2 15.5-38 1,400-4,000 2,200 Talling (1965); L and Tanzania-lJganda DB; lGmonth study

Sylvan, Indiana, 4l 9-4,959 1,5 64 Weøel (1966a) ; 14C U.S.A.

Spllerod S4, Denmark 55 max. 3,800 I,430 Steemann Nielsen ( 1955 ) ; L and DB; lake receives purified sewage

Lagoon in Sudan 10 max. 407 max.4,310 I Talling (1957a, 1965) ; Reservoir in Sudan l5 I 10-1 1B 1,050-2,800 I L and DB; isolated George, Uganda 0 max. 1,100 J estimates

Tomahawk Lagoon I 963-64* 0-726 206 0-3,840 830 L and DB (gross) ; few macrophytes I 964-65 19.7 -t34 60.5 134-1.220 562 laC; Sep 1964-Mar 1965; considerable macrophytic growth

Tystrup S4 55 0.5-290 6-4,200 920 Kristiansen and Mathiesen (North Basin), (196a); laCt; 1959-62 Denmark

Lakes of U.S.S.R. Highly eutrophic l 30-260 2,400-3,200 Eutrophic 25- 1 30 775-2,400

Goose Lake, Indiana, u.s.A. +l 166-1,752 729 Weøel (1966a);1aC

Fures@, Denmark 55 0.8-58 20-1,840 620 Jónasson and Mathiesen (1959);laCt;7 samples

Esrom S@, Denmark 56 3.5-42 30-1,460 490 Jónasson and Mathiesen (1959); laCf; 1955-58

Clear Lake, California, Goldman and Wetzel U.S.A. 39 3.3-140 2-2,440 +38 (1963); raç

Crooked Lake, U.S.A. +l 23-t,364 4t+ I Wetzel ( 1965a, 1966b) ; Little Crooked Lake, I toC; marl lakes in U.S.A. 41 9-2,+51 608 J Indiana

Erken, Sweden 59 1.5-60 +0-2,4O0 I Rodhe ( 195s ¡ ; uç ' Gervilon, Sweden 59 4-50 I 60- 1,7 00 I eutrophic lakes Lakes of U.S.S.R. Mesotrophic and Lrsually (13, secondary sometimes 3 20-2,300 I oligotrophic up to 25 I Vinberg (1963);laO, Low-producing I L and DB; usual shallow acid lakes 2.5-5 I 60-32 0 I midsummer values 1 60-32 0 Primary oligotrophic Usually (2.5 J Waipori 46 I 963-64 4.9-9.7 67 25-78 42 L and DB (gross) ; Nov 1963-Aug 1964; phytoplankton only 1964-6st 0.59-9.34 3.32 3. I -94 26 1aC ; phytoplankton only

Tomahawk Lagoon +6 May 1965-Jan 1966 0.58- 12.1 2.57 5.2-84 25 laC; phytoplankton only; macrophytes dominant

46 TABLE 14: Phytoplanhton productivity in some lakes of difrerent countries ( cont. )

Lake Latitude Pnar range Annual mean P/atearange Annual mean Reference, method, and (" ) (r"s C,/mtlnr) (mg C,h3.hr) (mg C,/m2.day) (mg C/m2.dav) remarks

Mahinerangi 46 1963-64 3.t-t7.5 8.42 39.3-5 3 0 266 L and DB; Nov 1963-Aug 1964 14C 1964-65$ 0.58-5.61 2.02 t9.6-220 76

Lakes of Swedish Lapland 64 0.4-3 2 1-l l0 Rodhe (1958);1aC; oligotrophic lakes

Lunzer lJntersee, Austria +8 0.25-2.r B-210 B2 Steemann Nielsen ( 1959) ; laCt; altitude 608 m; 7 measurements; I Year laC; Schrader, Alaska, U.S A. 69 1-167 l9 I Hobbie ( 1964); Peters, Alaska, U.S A. 69 0.2-20.7 25 | 1959, 1960-61; altitude j B50m

* as for 2 ust 1964. t positive i ai tor z 964-October 1965' i ;¡ f"; t 'Decmber 1965' r values have not been presented for the Buropean lakes, it sirnilar in P f area to a number of lakes which are is probably best to compare these with the New considered to be eutrophic. hi 1965, when the Zeitand lakes on the basis of seasonal maxima' lagoon was dominated by macrophytes, its P-a* Neither Lake Waipori nor Tomahawk Lagoon was similar to those of the least productive group (during 1965) can be usefully compared with the of lakes. other lakes on a basis of P f area. A comparison Some investigations of phytoplankton produc- would be valid only if the production of macro- tivity during "red water" dinoflagellate blooms have been made by marine workers. Some of the naximum productivities obtained in these studies are shown in table 15 with the highest estimates for the 1964-65 bloom in Tomahawk Lagoon. i\part from the very high maximum obtained for the Lake Mahinerangi is comparable with the least the Georgian estuary in 1955, it appears that in productive temperate lakes that have been studied. bloom in Tomahawk Lagoon was comparable The P-"* values for Lake Waipori, though usually intensity rvith those of marine areas. those for lVfahinerangi' are also a little higher than PRODUCTION AND RBSPIRATION of similar magnitude to those for the least productive group of lakes. During 1963-64, when pLank- DaiIy (24-hours) net oxygen Pf arca was calcu- ton algae \vere the dominant primary producers' Iated by applying a correction for respiration to the mean P'n"* for Tomahawk Lagoon was similar the daily gross production, which rvas obtainecl to those for other highly productive lakes, and the from the estimates of respiration in the dark maximum rates obtained were comParable with bottles. The annual oxygen production and con- the highest ever recorded' The lagoon was also sumption were calculated from the 24-hour values'

TABLE 15: Maximum rates of phytoplankton productivity obtained by various workers during dinoflagellate bloors. Region mg C,/m3.day mgC/mz'day Dominant genus Author and method Eruaiell¿ Steven ( 1966), 14C Kingston Harbour, Jamaica .2'tl7 (1954), New"Haven Harbór, Connecticut 1,512 :: Gonyaula* Conover L and DB (gross) laC Tomahawk Lagoon 1,7 40 1,2 l0 Gymnodiniunt Author, Duplin River estttary, Georgia Ragoøkie and Pomeroy ( 1957 1955 16,500 Gymnodiniunt- ), L and DB (gross) Ragoøkie Pomeroy ( 1957), r 956 5,840 2,870 Gymnodinium and L and DB (gross)

47 TABLE 16: Annual prod"lt-ion a'r-d respiration bI plankton in Tomaharvk Lagoon a¡¡d Lake Mahinerangi, as estimated from short-term L and DB experiments (g of oxygèn,/¡2.yeat).

Gross Gross production Lake Period production Respiration Net production Respiration Tomaharvk Annual mean* 968 t,032 -64 0.94 Mahinerangi Annualt 3 10 603 0.51 * -293 July 1963-June 196-1 and September 1963-August 1964. ï Mean daily values for the period November 1963-August 1964 were assumed to be epresentative of the annual mean daily value.

iìesults for Tomahawk Lagoon and Lake l\{ahine- (Pratt and Berkson 1959). These aurhors and rangi are shown in table 16. Zobe\l (1943) have shown rhat enclosing samples in bottles leads to a rapid growth of bacteria, The result for Tomaharvk Lagoon suggests that which may cause estimates of respiration to be too there ¡¡'as almost a balance between the production high, and this makes any such results rather and the consumption of oxygen by the plankton ambiguous. Photosynthetic energy-fixation by the community. The annual production in Lake benthic vegetation seems unlikely to account for Mahinerangi appears to have been only about half the deficit in Lake Mahinerangi, as filamentous of the respiration. This seems to suggest that the algae were sparse on the bottom, and vascular plankton community depends largely on a source aquatic plants appeared to be absent, possibly of energy other than that provided by phytoplank- because of fluctuations in water level, strong wave ton photosynthesis. A negative net annual produc- action, and the hardness of the bottom on the tion of oxygen has been reported for other lakes shallow sloping shores. Apart from bacterial photo- (for example, Riley 1939, 1940; Wright 1954; synthesis, on which there is no information, the Vinberg 1963). The present results are not neces- other possible source of energy is allochthonous sarily accurate, as they were based only on organic matter. Microscopic examination of water measurements made during daylight hours, and from the lake and from the inflowing streams re- many of the values were close to the limits of vealed what appeared to be fairly large amounts sensitivity of the method. I\4oreover, only 13 of organic detritus. Only about 200 ml of lake measurements were made over a lO-month period. water could be filtered through a 47-mm HA The deficit for tr4ahinerangi was larger than most Millipore filter before it became clogged, though others reported, but this might reflect differences when chlorophyll concentrations in the two lakes in the experimental techniques used rather than were similar, about three times this amount could any difference in lake metabolism. À4ost of the be filtered from Tomahawk Lagoon. Allochthonous published results rvere obtained from experiments organic material might therefore be a significant lasting between 24 hours and a week, and it has element in the annual energ'y budget, though it been shor,vn that algal populations in the light and will probably not be as important as the figures for dark bottles may differ strongly after onll' 48 hours production and respiration imply.

.18 THE RELATION OF PHYTOPLANKTON PRODUCTIVITY TO ENVIRONMENTAL FACTORS

INTRODUCTION generalisation was not valid for the period when Tomahawk Lagoon was dominated by macro- Although most attention has been given to phos- phytes. Experimental fertilisation provides a more phorus, nitrogen, and silicon as the chemical fac- direct appro,ach to the problem of nutrient limita- tors most likell' 16 limit productivity, at least 13 tion of phytoplankton productivity than chemical other inorganic nutrients are known to be required analysis of lake waters) but the advantages of the by algae (for example, Lund 1965). In addition, approach are at least partly nullified the need of various algae for certain specific experimental by the fact that often rigorous interpretation can- organic substances has been shown (for example, not be placed on the results obtained. Difficulties Droop 1962; Lund 1965). Any of these is Poten- the interpretation of experimental results are tially limiting, ancl limitation of phytoplankton in considered in detail by Wetzel (1965a). productivity by nutrients other than nitrogen, known. For example, phosphorus, or silicon is well LAKE MAHINERANGI Goldman (1960a, 1960b, 1964) has demonstrated that the ph),toplankton productivity of various A series of small-scale nutrient fertilisation ex- lake waters may be increased by small additions periments was carried out in the spring of 1965 of molybdenum, cobalt, magnesium, iron, or zinc, with phosphate (2, 5, 10, and 100 mg of and stimulation by the addition of vitamins to PO,-P/mn), nitrate (0.35 mg of NO'-N/I), sul- cultures of lake water has been reported by Gold- phate (2.3 mg/l), calcium (1.0 mg'/l), and mag- man (1964) and Wetzel (1965a). nesiunr (0.61 mg/l). No response was obtained in any of these, a result which might reflect inade- is based on the Correlation anallrsis, even if it quacies in the experimental design rather than concentrations simultaneous measurement of the indicate the absence of these nutrients as limit- nutrients, likely to be in- of all the required is ing factors. adeqr-rate for explaining seasonal variations in pro- in ductivity for the following reasons: Apart from The absence of any large seasonal changes stability of the role of physical environmental factors ancl the the algal species composition and the suggest that the organic environment, different species have dif- the chemical conditions measured may ferent nutrient requirements; algae may accumu- annual pattern of phytoplankton productivity by physical conditions rather late certain elements in excess of their immediate have been controlled investiga- requirements (for example, Ketchum 1939; than chemical conditions. In a further were car- Rodhe 1948; l\4ackereth 1953); production is a tion of this, multiple regression analyses whether the seasonal variations in dyn:r"mic process and can therefore be expected to ried out to find be related to the rate of supply of a limiting hourly P^u^ rates could be explained largely by and day nutrient rather than to the concentration at a variations in temperature, water level, particular time; certain algae may be limited by length. Because of the insensitivity of the L and the excessive concentrations of nutrients (for example, DB oxygen method, and the uncertainty of and Rodhe 1948); the concentrations of nutrients de- relation betrveen the results obtained with this termined analytically are not necessarily available with the 'aC method, only the 'nC results were to the algae; and requirements for one nutrient used. vary in relation to the availability of others (for Temperature, aplrt from direct physiological example, Rodhe 1948). Because of these difficul- effects on the phytoplankton, could also be ex- ties close correlations cannot necessarily be expected to influence the decay processes responsible pected between phytoplankton productivity and for the supply of nutrients. The temperature re- the concentrations of single nutrients, and none sponse obtained could also be expected to include was found in the present study. Although the mean a component from the interaction of temperature levels of phytoplankton productivity in the three with light intensity (for example, Steemann Nielsen lakes appeared to be related to the mean concen- and Hansen 1959). As many physiological pro- trations of many of the ions measured, even this cesses show a response to temperature that is

49 approximately exponential, and as the sum of an increase in lake level increasing the concentra- exponential functions is also an exponential, this tion of allochthonous organic material and a de- type of response was tested in the analysis. crease causing no change. However, as there was Lake level could also be expected to have a a more or less continuous increase in lake level complex effect on phytoplankton productivity. throughout the period of 'nC measurement, and Firstly, in a water column mixing at a constant as there were no theoretical grounds for preferring rate the level will influence the mean light inten- any other functional relationship, a linear relation- sity to which each plankter is exposed. Secondly, ship was tested. when the lake level rises, the inundation of terrestrial and bog regions at the margins could be Hourly rates of production can also be expected expected to increase the total concentration of to be influenced by day length. Phytoplankton nutrients by the addition of dead plant material of photosynthesis results not merely in the production terrestrial origin. This need not be reflected by of organic materials but in the production of changes in the ionic concentration of nutrients, as plankton crop, which in turn is able to photo- these may be assimilated by the phytoplankton or synthesise. Thus if an increase in day length re- bacteria as they reach the water. Merna (1964) sulted in a higher daily production, this would be found that there was a significant increase in the reflected by a subsequent increase in the hourly mean concentrations of total phosphorus in a marl production. Because of this compounding effect an lake after the lake level had been permanently exponential response might be expected, and this raised, though no significant increase in the mean type of response was tested. Although the response ionic concentrations was detected. The annual pro- might be modified if production per unit crop duction of phytoplankton in a lake in Sweden in- varied with crop density, it does not appear that creaged by a factor of.23 after the water level had this effect would be important in Lake Mahine- been raised, though changes in the chemical con- rangi (see page 56). Another possible effect could ditions were slight or absent (Rodhe 1964). This occur if there was a daily periodicity of phyto- effect might be expected to be discontinuous, with plankton productivity of the type noted by a

TABLE 17: The ¡elation between P.., in Lake Maþineranqi and tempcrature, day length, and water level shown as coded results for the multiplc regression analysi.

Regression Variable b t R R2 2dr". sr a dÍ I Xt 2.34085 1.825 0.6006 0.3608 6.2898 0.5473 7.ttzt 2l Xs 0.00155146 3.256

II Xt 3.332679 4.267 0.8851 0.7834 2. 1 308 0.3264 7.90392 20 Xz 0.0163595 6.247 Xs -0.00138102 2.517 III X1 2.93520 3.991 0.9143 0.83598 0.299+ 7.7693 IB X2 0.0152617 6.233 Xz2 0.0000193802 0.548 Xs 2.692 Xs2 -0.00242491 -0.0000027 47 1.671 TV Xt l.46588 1.182 0.9241 0.8540 1.4362 0.2906 7.7510 t7 x] 1.450 Xz -18.385000.0132477 4.812 Xz2 -0.00000056969 0.015 xs -0.00229179 2.606 Xs2 -0.0000040269 2.208 V x1 l.l777t 0.443 0,9242 0.8542 t.+3+B 0.2994 7.7393 l6 xf 0.971 xf -16.954417.9581 0.123 X¿ 0.0128731 3.101 Xz2 0.061 Xs -0.000002527 2.+59 Xs2 -0.002269880.00000408077 2.116 Y=log"l,000P-.";Xr=log"(waterlevelXl0)-6.8iX2:temperatureXl0-100;Xr=daytengthXl00-1,000;D:partia¡regres. lR : sion cæfficient; cæfficient of multiple correlation; >d2y.= deviation sum of squares; Sr" : standard e¡ror of the estimate of ts; a = ¡ntercept of multiple regression line; t = value obtained in t test foi significance of regression, wherð df : degrees of frædom in this test. Only the last , in each polynomial series has any meaning except with respect to the coded data.

50 number of authors (for example, Doty and Oguri In the first regression, with temperature elimi- 1957) and if this were light conditioned' nated, the square of the multiple linear correlation The form of the relation tested was thus coefficient was 0.360, so that only 36 percent of log" P*u* - a * å' temperature * b, day length * the variation in log Pmar w&s explained by varia- å, log" water level. In addition, the effects of intro- tions in day length and rvater level. In regresqion ducing the second order polynomials in tempera- II, in which temperature was also included, 78.3 ture and day length, and higher polynomials in percent of the variation was explained. When the log" water level, were tested in various combina- second order polynomials in temperature and day tions. Dr R. M. Cassie, of the University of Auck- length were next introduced, in regression III, land, who had a computer programme of his own theie was only slight improvement in the relation, design which was suitable for the planned analysis, and the ú tests indiiate tliat there was no significânt kindly carried out the computing. As eight sig- regression on either of the X2, so that their inclu- nificant figures were carried in the programme, sion was considered unjustified (Snedecor 1956, and as the highest correlation between any pair of p. a19). Similarly, the further introduction of the independent variables was only 0.86, the pro- second order polynomial in lvater level (regressi'on gramme was considered adequate for the separa- IV) produced little further improvement in the tion of the effects of the three variables (Snedecor relation, and again the regression was not sig- 1956, p. 438). The data and coding are presented nificant on any of the X2. Consideration of higher in Appendix IIE and results (in coded form) are powers in the independent variables in various shown in table 17. other combinations (regression V and others not

J o oa' E

rú o o Ð

1964 1965 1966

Fig.. WI ob be 23

5l presented ) also resulted in little improvement in negative suggests that the effects of a diurnal the relation, so that these also could be excluded. periodicity in photosynthetic potential were the It therefore appears that the postulated model of most important of the postulated effects of an exponential response by P.o* to temperature changing day length. The fact that the partial and day length, and a linear response to variations regression coefficient for water level was positive in water level, was reasonably adequate. After suggests that the stimulatory effects of the nutrient decoding, the multiple linear regression equation increment resulting from an increase in lake level was: outweigh any inhibitory effects which may result Y"*¡ : 3.33261o9" X' + 0.1635 X" from a decrease in the aver:age light intensity to 0.1381 X, t4.0+97 which each phytoplankter is exposed. where - - Yu", is the estimated value for log" P-"* (mg The productivities calculatecl from the multiple of carbon/m3.hour), X' is the water level at the regression equation are shown in fig. 23 with those dam (ft) X, is the temperature (oc), and is , X. obtained with the 'nC method. This equation ex- the day length (hour). plains most of the major features of the annual The / tests for significance of regression indicate cycles of P-o', with agreement being particularly that variations in temperature were the major close during winter. Much of the variability during factor influencing va¡iations in P*o* (P <0.001). summer and autumn was also explained, and this Variations in water level were only slightly less appeared to be related largely to variations in important, and this regression was also highll' sig- temperature. The occurrence of the annual mini- nificant (P <0.001). Variations in day length mum in phytoplankton productivity in early spring appeared to be the least important of the three was an unusual feature of the annual cycle. Values factors, being significant only at the 0.05 level of estimated from the regression equation were gener- probability. If this level of probability is accepted, ally higher than those obtained with the 'nC the fact that the partial regression coeflìcient was method at this time. This may have been due to

Mahinerangi a Waipori x

o o - 15 Ir J x I G' o ê É ; 10

it It I I I

s J J I 964 1965 196 6 Fig. 24: Surface temperatures in Lakes Waipori and Mahinerangi in 1964-66.

52 x llt tr a-

0-5 -4 -3 -2 Temperature difference ( Waipori - Mahinerangi) "C Fie..-?iinãL".årl 25: The relative productivity of Lakes Waipori and Mahine¡angi on, a- log-arith.mic scale plotted against temperature ir* .rriå-ri""îpér""t" ttr. t"-påtrt"r" iesponse suglested for-Mahinerangi by the partial regression coefficient in the multiple regression equation. for the random deviations, or -comc other factor lna)' previous or following estimate obtained This was done become important in sPring. rnain station at Lake t\4ahinerangi. as as possible the effects of 'fhe results of this analysis suggest thac the to eliminate far day length, ancl only '¿ on was changing water level and ProductivitY were used' g in temperature' The samples separated by less than 10 days Theie results were plotted against the correspond- v Year of studY were in temperature and rvere compared generally higher than in the first, and this dif- ing differences temperature response suggested for f....r.. appeared to be related largely to variations wittr the Mahinerangi by the partial regression coefficient in water level. on temperature in the multiple regression equation' LAKE WAIPORI Only the Waipori samples considered to be not It appears from fig. 11 that there was a fairly influenced by drainage rvater (page 33) have been IIE close correlation between the Pn'"* values for Lakes included. The data are shown in Appendix Mahinerangi and Waipori, which suggests that and the results in fig. 25. similar factors may control productivity in the Most of the estimates for Pn'o* for Lake Waipori two lakes. It has been suggested on page 33 that rvere higher than the temperature differences and at least a part of the greater variability in Waipori the corresponding estimates for IVlahinerangi may be due to the influence of drainage rvater that would suggest. One of the exceptions occurred on is pumped from the l-aieri Plain. An improvement a day rvhen the abnormally high temperature of in nutrient conditions in lvlahinerangi resulting 24oc rvas recorded at 0.5 m in Waipori, and in from an increase in water level should be reflected these conditions some modification of the tempera- by a similar improvement in Waipori, and day ture response might possibly be expected. It is length is the same at both lakes. In view of the therefore unlikely that clifferences in temperature similar phytoplankton species composition, a simi- were the only factor responsible for the differences lar temperature resPo'nse might also be expected. in P^",. Although temperature may still be a Surface temperatures of the two lakes from 1964 major controlling factor in Waipori' control is to 1966 are shown in fig. 24; those in Waipori apparentlv exercised about a higher mean level, were almost invariably higher. To find whether which is governed by other conditions. These this alone would account for the differences be- might include the higher mean light intensities for tween corresponding P'*" values in the two lakes, the water column in \{aipori, resulting from the each estimate of P'n"* for the main sampling station more shallow depth, and differences in edaphic at Waipori was expressed as a fraction of the conditions.

53 On many sampling days it appears that a de- closer to P.", &nd hence more productive than the crease in surface light intensity would, within corresponding onc effectively removecl from thc certain limits, have led to an increase in phyto- top. A similar increase would have resulted from plankton productivity beneath unit surface area. a decrease in light intensity sufficient to raise P-"* The shallow depth and moderately high trans- to between 0.25 m and 0.5 m on the days when parency of Lake Waipori cause the depth profiles Pmax lvâs recorded at 0.5 m. It is not clear what for phytoplankton productivity to be truncated, would have been the effects of either a greater with P-"" most often occurring in the bottom half lowering of the light intensity than those specified of the water column. For any particular depth or any decrease at all on the rather cloudy days profile the effects of a decrease in light intensitl' rvhen P-o* was recorded at 0.25 m, as interactions rvill be governed by two factors. The first is the betrveen the symmetry and the displacement of the vertical distance through which the curve is effec- profile could not be evaluated. On the two rather tively raised, and this will be related to the frac- dark days when P-o" was recorded at the surface tional change in surface light intensity and the any further lowering of the surface light intensity transparency of the water (Steemann Nielsen would have caused a lowering of Pfarea. On 26 1954). The second is the symmetry of the curve of the 38 sampling days Pma" wâs recorded at about P-o". Productivity measured 25 cm above 0.5 m or 0.75 m and it therefore appears that light the depth of P.o" was lower than at a depth 25 cm intensities are supra-optimal for the phytoplankton below it on seven occasions, equal to it twice, and on at least 2 days in 3. slightly greater on 2 of the 1l days for which this information was available, so that there w¿ìs a TOMAHAWK LAGOON tendency for productivity to decline faster in the 25 cm immediately above the depth of p.u" than Unlike those in the other two lakes, both the in the 25 crn immediately below it, though this phirtoplankton species composition and chemical result might have been produced by sampling bias. conditions in Tomaharvk Lagoon are very variable On the bright sunny days when Pmax wâs re- from month to month and from year to year. It corded at 0.75 m a lowering of the surface light has also been suggested on pagæ 37-44 that the intensity sufficient to raise P-", to a depth of 0.25 presence or absence of macrophytes is of major m would have led to an increasein Pf area. This is importance for the phytoplankton productivity in because, apart from the possible as)/mmetry noted, this lake. Because of these factors it was considered the stratum rvhich would in effect have been added that any simple model based on physical variables to the bottont of the profile ryould hare been rvould be inadequate.

54 INDICES OF PHYT'OPLANKTON PRODUCTIVITY

INTRODUCTION chlorophl,ll o ænd Phytoplankton productivity lakes shorvn frg.27. Indices of primary productivity are of two types (P,"o')* for the three are in value obtained December based on estimates of the photosynthetic The for Waipori on 7 ditrered the data a -thosecrop and those based on changes produced in the 1964 from other Waipori with degree statistical has chemical environment by the processes of produc- high of probability and it analysis. reason for tion. Crop estimates are an expression of the been excluded from the The accumulated production, but, being static esti- this difference is not known. mates, they have inherent disadvantages as indices The correlations obtained for the three lakes of the dynamic process of production. They do not appear to be comparable rvith those reported by in themselves indicate the rate of flow of energy other workers (for example, Bdmondson 1955; or turnover of materials, and to use them for the Cassie 1963; Anderson and Banse 1965). None of calculation of productivity it is necessary to apply the correlation coefficients was high, even when rate corrections that must be rather arbitrary. the lakes are considered individually. Furthermore, relation chlorophyll P*u* dif- Indices based on changes in the chemical the between a and fered three lakes, and Tomahawk environment have the disadvantage that these for the for Lagoon results obtained before 1965 changes may be produced not only by primarv the 7 May production but also by other biotic and abiotic differed consistently from the later results. The processes whose relative contributions cannot mean relative assimilation rates (mg of carbon assimilated/mg of chlorophyll a. hour) were: always be assessed accurately. Measurements of the rate of removal of phosphate from the water Tomahawk until7l5l65 4.38 have been used with varying success to determine Tomaharvk after 7 /5165 1.06 productivity in oceanography (for example, Waipori (excluding value on 7 l1216+) 0.97 Cooper 1958; Steele 1958), but this method is not Mahinerangi 0.61 suitable for use in limnology. It and similar T'hese decreased in the same order as the mean methods used for marine waters are reviewed by productivities. The total range for relative assimila- Strickland ( 1960 ) . Observations of diurnal tion rates was 0.2-10 mg of carbon/mg of chloro- changes in the concentration of oxygen or total phyll a. hour, which appears to be similar to the carbon dioxide have been used in lake ancl pond range of published figures, though the mean for studies, but the exchange of these gases with the Mahinerangi was lower than those most commonly atmosphere presents a difficulty with these reported. Other authors also have founcl that the methods. There are also difficulties in the measut'e- relation between'nC assimilation and chlorophyll a ment of small changes in concentrations of carbon may show seasonal and regional variations (for dioxide, and these methods are not in common use. example, Steele and Baird 1961). If chlorophyll a Although the 'aC and L and DB oxygen methods is to be used for the estimation of phytoplankton are the most direct methods commonly used, they productivity, for example, by the method of Ryther provide no more than approximate estimates of and Yentsch (1957), this relation must be con- the phytoplankton productivity owing to their stant. many potential sources of error. As no exact Several workers report that the rate of produc- method is available for measuring phytoplankton tion per unit crop tends to vary inversely with the productivity, other indices usually have to be crop density when this is expressed as plant evaluated by the artificial standard of how closely volumes (McQuate 1956) or chlorophyll concen- they correlate with 'nC or L and DB results, a trations (Rodhe, Vollenweider, and Nauwerck standard rvhich may underestimate their worth. 1958; Wright 1960). The relation between productivity per unit chlorophyll ¿ anel the concentra- CHLOROPHYLL ø tion of chlorophyll ¿ is shown in fig. 28, which Chlorophyll 4 concentrations in Tomahawk indicates that there was no relation between the Lagoon are shown in fig. 14; those for the other lakes are presented in fig. 26. The relations between +Hourly rates for the -hour midday experimental period.

55 Mahinerangi o Waipori x

(Ð EI E'l E a

E ct o I 6 o

N J 1964 196 5 Fig. 26: The concent¡atioru of chlorophyll a at ¡}re surface at the main sampling stations on Lakes Waipori and Mahinerangi for the period October 1964-August 1965. trvo when results for the different lakes are com- by bleaching of chlorophyll at the surface (Rabino- bined. When the results obtained for Tomahawk rvitch 1945, p. 532). The relation between chloro- Lagoon before and after 7 };'4ay 1965 are con- phyll ø and productivity may also be influencecl by sidered separately there appears to be a tendency varying amounts of inactive chlorophyll.* The toward inverse variations, and the Nlahinerangi efficiency of extraction of chlorophylls may vary data show a similar pattern. However, none of rvith the species composition of the plankton these relations was particularly close, and produc- (Strickland and Parsons 1960), ancl the analysis tion per unit chlorophyll was always largely in- based on chlorophyll a alone ignores the role of dependent of chlorophyll content over a fairly wide the other pigments in photosynthesis. range of concentrations. The relative amounts of the different pigments Several factors are likely to reduce the signific- were not constant, but in view of the uncertainty ance of the relations between chlorophyll a and of trichromatic spectrophotometric methods for productivity. It is the gross photosynthetic produc- pigments other than chlorophyll a (f.or examPle, tion which can be expected to be directly related to Humphrey 1963; Parsons 1966), the potentially chlorophyll ø, but 'aC assimilation is probably large photometric errors, and the large amounts more closely related to net production than gross. of calculation involved, only a few of the concen- Chlorophyll samples were taken at the surface and were compared with the P'u' values, which were usually recorded at some depth below the surface, so that results may have been influenced by vertical unevenness in the distribution of phytoplankton or rapidly by the acetone.

56 M ah i nerang i Tomahawk A + f = 0.26 2,11 X Y=0.40+0.27 X r = 0.75 r=0.71

(Ð E ctt E

(ü

! cl o Waipori Tornahawk B I Y= 1.59+0.71X f =1.41X- 0.69 o r ¡ = 0.51 =0.84

Pmax (mg of carbonrm3.hour)

Fig.27: Regressions of chlorophyll ¿ on phytoplankton p_roductivity. The-period of readings-for Tomahawk A was from T òctob"r" 1964 to O May igOS; that ÎorTõmahawk B wa from 17 May to 11 August 1965. trations of the other pigments were calculated this method of estimation is used (Parsons and in 1963). Although very high concentra- (table 1B ) . Detailed results are presented Strickland Appendix IIF. The lower relative assimilation rates tions of a red pigment were present, little quanti- in this table do not appear to have been produced tative significance can be a.ttached to the figures by - increased contribution from pigments other obtained. than chlorophyll a. Cassie (1963), using multiple SECCHI DISC TRANSPARENCY regression analysis, found that there was no con- Within a single lake variations in the seston are stancy from experiment to experiment in the likely to be the major factor influencing variations amount of improvement produced by introducing in the Secchi disc transparency (Hutchinson 1957, chlorophyll c or carotenoids into the relation, but p. 403 ). Consequently, where variations in the this result was also obtained with pigment con- phytoplankton are large in relation to variations in centrations estimated by the method of Richards other components of the seston, changes in the and Thompson (1952). transparency may provide an index to variations Very high concentratiotls were attributed to the in the phytoplankton crop. Being an index of crop, "animal t1,pe" astacin carotenoids during the dino- they might also be expected to relate to phyto- flagellate blcom in 1964-65, but the pigments pre- plankton productivity, at least under these re- sent were likely to have been plant pigments, some stricted conditions. In Tomahawk Lagoon an in- of which give positive readings for astacin when verse relation between Secchi disc transparency

5',1 o o Tomahawk Oct 1964-7May 1965 "; x Tomahawk after 7 MaY 1965 o L T L,Waipori I A L, Mahinerangi o o E) E

l)o (,rú o E'} E

4 A x (t s- A'TT E clJ A o- o s9 e2 A

.x x x x

l0 20 30 40 50 600 2 4 6 I 10 12 14 Chlorophyll (mg/m3) " Fig. 28: The relation between rates of production per unit chlorophyll a at near-optimal light intensity and the concentrations of chlorophyll ø.

TABLB lB: A selection of results obtained for the concentrations of chlorophyll and carotenoid pigments in Lakes Mahinerangi and Waipori and Tomahawk Lagoon as calculated from the equations of Richards anùThompson (1952). Chlorophylls Carotenoids ab¿Non-astacinAstacin Date A.Q. (mslm3) (mg,/m3) (MSPU,zms) IVÍSPU/mB) (MSPU/n3)

Tomahawk 5/ l0/ 6+ 2.53 20.7 3.85 64.7 rB/t0/64 5.7 t 16.4 3.64 3+.7 2/12/64 5.27 15.0 1.50 53.7 L4/12/64 10.00 t 1.l 1.99 27.9 8/2/65 9.76 10.+ +.53 37.4 22/2/65 2.00 41.0 -ve -ve -ve 201.0 8/3/65 3.19 60.8 -ve 10.3 -ve 98.4 t2/4/65 3.11 7.06 -ve -ve 2.95 0.5 17 /5/65 0.90 2.03 -ve -ve 0.64 L.17 5/7 /6s 0.55 26.0 2.09 -ve B.15 -ve tt/B/65 1.11 0.86 0.52 -ve 0.45 -ve

Waipori t7 /2/65 0.99 584 -ve 3.06 2t/5/65 o.54 35 -ve -ve l.98 0.05

Mahinerangi L0/2/65 0.50 t3,7 -ve -ve 10,20 7 /4/65 0.26 9.0 -ve 2.72 4.46 0.50 9/B/65 0.56 2.82 1.7 B -\'e 1.14 -ve

A.Q. Relative assimilation ¡ate (mg of carbon/mg of chlorophyll o.bour at near-optimal light intensities). -ve Negative values.

58 Tomahawk net 02 O Tomahawk 14c x Mahinerangi net Oa ¡ Mahinerangi 14; ^

ã o 100 <'¡' x )q xXx ¡¡o fit IJ o "ltt Ð O¡ E x x ltt tr q. IX t xal t |ixf*'^1 ¡ ^ ^r^ ^ti¡, t^a xtt "\ A \X A - 0.1 t'o l0 Secchi disc transparencY (m) phytoplankton productivity (P-"') Lake Mahinerangi -Fig. 29: The relation between Secchi disc transparency qnd in ä"ã-io*"tã*t l-ãgoo",-u"¿ th" least squares regression line for the comtined results. and chlorophyll ø has been noted on page 38 and were considered independently the correlation was similar relations have been recorded by other not significant (r: -0.212), so that Secchi disc workers (for example, Rodhe l94B). In Lake transparency is of no value as an index of varia- Mahinerangi the two were not related. tions in productivity in this lake. These results The relation between Secchi disc transparency agree closely with those of Vollenweider (1960)' and P*o" for the two lakes is shown in fig' 29, who found that the correlations were close for two which includes estimates obtained with the 'nC highly productive Swedish lakes, but poor for two and L and DB methods, expressed as hourly rates less productive, more transparent ones. Although for a sunrise-sunset experimental period. For the transparency is of no value in predicting varia- Tomahawk Lagoon alone the correlation coefficient tions in productivity in Mahinerangi, the Mahine- lay close to the curve fitted to Toma- for the double logarithmic relation was -0'860, rangi data which indicates a fairly close correlation between hawk Lagoon results, so that this curve does estab- the two variables. When the Mahinerangi data lish the general level of productivity of Mahine-

59 rangi. The correlation coefficient for the combined ficiently close to be considered useful, in spite of data was -0.91 and the regression equation was: potential bias from the different methods of mea- Y :3.7099 - 0.798 log.oX suring P-u", the uncertainty of the correction for where Y is log'oP-n" (mg of carbon/m'.hour) and the different experimental periods used, and the X is the Secchi disc transparency (cm). The stan- measurement of Secchi disc transparency at dif- dard error of the estimate of Y was 0.2918, which ferent times of the day with the two methods. This rvhen retransformed gives a confidence ratio of result, obtained for two such widely different lake 1.96; that is, there is a probability of about 70 types, suggests that Secchi disc transparency might percent that a single estimate of phytoplankton possibly have some general predictive value for productivity from the Secchi disc transparency will phytoplankton productivity. This could apply only be between a half of the corresponding experi- in the limited sense of establishing general levels m€ntal estimate of P."* and twice the experimental of productivity, and would probably not apply to estimate. As the total variation in Pma* was by a highly coloured lakes or those which receive large factor of more than 1,000, this relationship is suf- amounts of allochthono-irs materials in suspension.

60 GENERAL DISCUSSION AI..[D CONCLUSIONS

LAKE MAHINERANGI phytoplankton, so that observation of productivity curves or simple correlation techniques do not For Lake Mahinerangi a coefficient of multiple allow any conclusions to be reached on the influ- mul- correlation (.R) of 0.8851 was obtained in a ence of a single environmental variable unless it is tiple regression analysis in which temperature, day greatly important in relation to all others. Nor do independent length, and water level were used as such methods allow the effects of different environ- variables and hourly rates for phytoplankton pro- mental variables that are intercorrelated to be (P-"") ductivity at near-optimal light intensity isolated. as the dependent variable. The multiple regression equation: Results of the present investigation suggest that impor- Yest : 3.3326\ogn X' + 0.1635 X" variations in temperature were the most - 0.1381 X" - l+.0497 tant factor influencing productivity in Lake therefore explains 78.3 percent (R') of the varia- Mahinerangi. 'l-he partial regression coefficient on tion in productivity that occurred during the tcmperature rvas highly significar-rt (P < 0.001), period that the "C method rvas used, where Y""t and the coefficient of multiple correlation was in- is the estimated value for log" Pn n* (mg of carbon/ creased from 0.66, when only water level and dav m'.hour), X, is the water level at the dam (ft), length were included, to 0.89 when temperature X, is the temperature ('c), and X' is the day rvas also considered. It appears that the large fluc- length (hour). Although an exponential response tuations in productivity which occurrecl during to temperature and day length and a linear re- summer were largely related to variations in temi sponse to water level were the only relationships perature. There are similar fluctuations in many tested directly, the absence of any significant re- published curves. By the use in this analysis of gression on higher powers of these variables sug- P^o*, which represents an approximation to pro- gests that the responses were appropriate. This ductivity under optimal conclitions of illumination, does not imply that no other curvilinear relations light intensity could be neglected as a factor. The would have been appropriate, but merely that the optimal value for light intensity is not constant' model was reasonably adequate. Riley (1939) however, but is conditioned by other factors, in- found that a curvilinear response by phytoplank- cluding temperature (for example, Ryther 1956; ton productivity in Linsley Pond to temperature Rodhe et al. l95B; Steemann Nielsen and Hansen was more appropriate than a linear one, and he 1959; Ryther and X4enzel 1959; Jorgensen and states that it appeared to have an exPonential Steemann Nielsen 1965). The indicated tempera- form. Talling (1957b) also found that there was ture response can therefore be expected to include an exponential relation between Pnrnx per uûit a component from the interaction of light and population and temperature in Asterionella. temperature, so that the effects of light intensity Although Eflord (1967) has suggested that phyto- have not been eliminated entirely, but merely pla.nkton productivity at 1 m in Marion Lake, attributed to temperature. Riley ( 1940 ) reports British Columbia, bears a relation to temperature that productivity at the surface of Linsley Pond that is linear at temperatures above l0oc, it seems showed significant partial correlations with chloro- likely tha.t an exponential would fit his clata well phyll and temperature, but not with light. For the if the productivities which he obtained at temPera- rvhole of the euphotic zone light ancl temperature tures below 10"c were also included. were significant, but chlorophl,ll was not. Riley (1939, 1940) appears to have been the The partial regression coefficient for tempera- only worker previously to use multiple regression ture for Lake l\{ahinerangi suggests that the mean analysis to aid the interpretation of annual cycles temperature coefficient (Q'o) for Pmax wâS 5.1 over of productivity in lakes, and in the 1939 paper he the range of temperalures measured (2.0-18.6'c). has reviewed the advantages and limitations of the This coefficient is high in relation to those obtained method in detail. The chief advantage is that it for other aspects of algal biologl'. For example, allows the influence of different environmental Lund (1949) found that with adequate enrich- factors to be isolated. Many factors act on the ment of nutrients, an increase in temperature from

61 10o to 20oc increased the rate of cell division of production of fish, thorrgh srrch regrrlation will Asterionella formosa Hassall by a factor of about 2, usually be subservient to other uses of the water, and Talling (1957b) obtained a Q'o of 2.3 lor such as the generation of electricity. 1-he present light-saturated rates of photosynthesis per unit results, though pointing to the importance of the population for the same species. Although no great rvatcr level for phytoplankton productivity, fall rveight can be placed on the particular value short of this objective, as many other factors would obtained for a regression coefficient in multiple need to bc considered for most effective manage- regression or in any exponential relation, there is ment. These factors include the loss of those ben- every reason to expect the present temperature co- thic animals which cannot migrate as the water efficient to be higher than these examples. Tem- level falls, the corresponding gain of terrestrial perature could be expected to influence the algae food organisms when it rises, the rate at which directly, and also indirectly, by its effect on the terrestrial vegetation becomes re-established on chemical and decay proccsses affecting the supply newly exposed shores, and the relation between of nutrients. There rvill also be an effect from phytoplankton productivity and fish production. temperature-induced population changes and an- N{oreover, an increase in lvater level during one other from the interaction of temperature and part of the year might be more effective than light. These will all combine to produce the tem- during another, but the present analysis provides perature coefficient obtained. no information on this. Nevertheless, there is at least a possibility that the intermittent raising and The importance attributed to temperature sug- lowering of the level of Lake Mahinerangi by the gests that temperature differencès might have con- Dunedin City Corporation Electricity Depart- tributed to the variability of the relation between ment may be of some l¡enefit to the angler. productivity rt different sampling in stations The partial regression coefficient for day length summer. Temperatures at thé minor sampling rvas negative. This might mean that there is a stations were not recorded, but some difierences cliurnal periodicity of photosynthetic potential, might be expected in an irregular basin as such with a tendency for the potential to decline during this. the period between 2$ hours after sunrise (the There is evidence from other Þtudies that an in- starting time in mid winter) and 5nê hours after crease in phytopla.nkton productivity or nutrients sunrise, which was the starting time a-t the summer results from lake levels being raised permanently solstice. A detailed experimental investigation (Rodhe 1964; Merna 1964). These effecrs have would be needed to confirm this, however, as the g5 been attributed to the addition bf nutrients by the response rvas significant only at a percent con- deca;' sf drowned terrestrial vegfetation and leach- fidence level, and no evidence of a periodicity was in.g from the soil. In the present.study there was a found in a single direct test, conducted on 9 Sep- highly significant regression of P,n", on water level tember 1965, in which experiments rvere started (P <0.001), uttd the fluctuatio¡s in water level at sunrise, 2 hours before astronomical noon, and that occu¡ in other reservoirs lvill also be likely to 2 hours after astronomical noon. The highest value have some effect on the phytciplankton produc- obtained from a depth profile showing surface in- tivity. Multivariate analysis appþars to be the only hibition of productivity (P-",) does not represent technique by which these effeets can be investi- a true optimal value, as it may be influenced by gated, as the problem is not amenable to experi- variations in light intensity during the period of mental investigation. During the period of the measurement. The negative regression coefficient present investigation, August 1964-January 1966, obtained may thelefore merely reflect a greater the lake level was continually rising. The land in- variability in light intensity during the 4-hour undated before l{ay 1965 had previously been experimental period in summer than in winter, flooded early in 1964, but much of that sub- though no evidence is available on this point. This sequently flooded had not been under water since analysis was based on hourly rates of production. September 1960. Some estimations of daily production in Toma- hawk Lagoon indicated that the 4-hour experi- If the effects of rvater level on the biota of a mental period represents a varying fraction of the reservoir can be elucidated, it may then be pos- daily production, with the variations being almost sible to regulate the levels to obtain the maximum directly proportional to day length.

62 in The occurrence of the annual minimum of multiple correlations are less likely to be found typical ph;'teplutrUron productivity in early spring was an the more complex situations that are more bodies of unusr.ral feature of the annual cycle in Lake of lakes, and hydrographically simple ated from the regres- water seem to offer the best prospects for the than those obtained analysis of the efiects of physical environmental period, in both 1964 variables on phytoplankton productivity. been due to random im- deviations or to some other factor becoming LAKE WAIPORI

¡\n ProductivitY in Lake lar to those in Lake interPret them were hampered by several faciors, including the crcase in the zooplankton crop until 29 October, short retention time for the water, the shallow some time after the minimum in phytoplankton depth, and the complex hydrology. Just before it varia- productivitr'. Although a large part of the reiches Lake Waipori the water which flows from tioir in productivity could be explained without Lake Mahinerangi in the Waipori River is mixed reference to grazing by zooplankton, this does not with water from the Contour Channel, which has necessarilf in-rply that grazing wzrs unimportant' a higher ionic concentration, and an addition of Grazing presslrre rnay well have been closely cor- nutrients from this source probably accounts related rvith temperatLlre, rvater level, or day largely for the higher P length, in which case its effects would have been pori per unit volume. attributed to one of these. Nor does the close drainage water, which correlation with ph1'sical variables imply that the concentration than eith phytoplankton were not limited by nutrient de- which for a time contained a herbicide, add to the lake ficiency. The very low productivity of the complexity. The pattern of mixing and distribution suggests in itself that nutrients lvere limiting, and of the different water masses appears to be vari- the close correlation obtained with other variables able and is probably governed by interactions nutrient may merely indicate that the degree of between wind, tidal ebb and flow, and variations limitation rvas fairly constant or, as postulated in the relative rates of flow- earlier, that the rate of nutrient supply is correlated rvith water level and temperature. It is conceivable that the productivity may have of the phyto- Riley (1940) found that phytoplankton pro- been limited at times by an inability development cluring the ductivity in Linsley Poncl was not significantly plankton to reach full time the rvater was retained in the lake, but correlated with the concentration of nitrate or short is no e'"'idence of this. Zooplankton popuia- phosphate, but multiple regression techniques are there verv small, and this may have not well suited to the investigation of limitation tions appeared to be an inability of these more slowly of phytoplankton productivity by nutrient defici- been due to organisms to reach their full develop- ency unless, perhaps, they are based on intra- reproducing ment in the time available' The absence of high pH cellular levels of the nutrients ancl rates of regener- the low buflering capacity of ation rather than concentrations in the water. It values, in spite of and the growth of large amounts of appears that careful observation ancl experimenta- the water at times, was probablv also due to the tion have more to offer here, as exernplified in the Anacharis work of Lund (for example, 1949, 1950a, 1950b, short retention time. 1964) on lakes of the English Lake District, It appears from an empirical anall'515 of the Rodhe (1948) on Swedish lakes, and others. depth profiles that within certain limits a decrease Lake N{ahinerangi is characterised by the in ihe surface light intensity rvould have produced absence of any thermal stratification or marked an increase in the phytoplankton productivity seasonal changes in water chemistry, and the (P larea) on at least two-thirds of the sampling phytoplankton is dominated by the same two or clays. It is likely that this will be founcl for other three species of algae throughout the year. Close shallorv transparent lakes as well.

63 TOMAHAWK LAGOON times a prolific growth of Spirogyra associated with the weeds in Tomahawk Lagoon. The most striking feature of the results for Tomahawk Lagoon was the large decline in phyto- The evidence on possible limitation of the phytoplankton productivity which occurred in 1965, plankton by nutrient deficiencf is equally incon- after the development of a large crop of macro- clusive. The figures for pH and alkalinity pre- jn phytes the summer of 1964-G5. Although there sented by Hasler and Jones (1949) indicate that are scatterecl references to this phenomenon in there would have been ample carbon dioxide avail- limnolo is not known horv gener- able in their experiments, and it seems unlikely ally it own experimentally with that this would have been of major importance a high al probability that popu- even at the higher pH levels obtained for Toma- lations were lower in tanks cãn- hawk Lagoon. It also appears that there were taining Anacharis canadcnsiç and srnaller amounts adequate amounts of calcium and magnesium, and of Potamogeton foliosu,s Rafinesque-Schmaltz than there were very large a"mounts r_rf reactive phos- others rvithout rveeds (Ha:ler and Jones lg4g). phate in the lagoon during the period that phvto- Although they did not inl'estigatc rhe mechanism plankton grorvth was inhibited. by which ph1'toplankton \vere inhibitecl, Hasler The only direct evidence on nitrate was the lack and Jones have postulated that b1, emerging early of any response by the phytoplankton to the add!- in spring the weeds might inhibit the subsãquent tion of 500 mg of NOr-N/ms to water from the emergence of phytoplankton bv shading the lagoon in a single small-scale experiment. It might bottom. It seems unlikely that this was the mech- be significant that in addition to other algac there rvere alwal,s Anabaena appeared to be inhibited in the snmmer iir diarneter, and of 1965-66, as members of this genus are often ded a reservoir of associated rvith the fixation of atrnospheric nitro- perennatcd phytoplankton for the colonisation of gen (see Lund, 1965), but clearly more evidence the open lvater. Furthermore, several species of is needed on the possible roles of nitrogen ancl the algae appeared to increase in summer and earlv other nutrients which were not investigated. autumn, after the weeds had become establisheá but before the decline of phytoplankron hacl be- Although no quantitative estimates of ¡veed come evident, though this might have represented crop were made, there tvas apparently little weed merely an increase by species previously present in in the lagoon between July 1963 and December very low numbers. There was a large increase in 1964, and because of the large phytoplankron at least one species of flagellate in the winter of crops, light reaching the bottom of the lagoon was 1965, at a time when the weeds were dominant, probably insufficient to permit their grorvth during and this appeared to be related to replacement of much of this period. By subsequently inhibiting much of the lake water during a floocl, rvhich the growth of phytoplankton the weeds were able seems to favour a theory of chemital limitation. to increase the amount of light available for the'r orvn grorvth. The fact that the decline in phyto- Chemical limitation might l¡e brought about plankton productivity in 1965 was so large may either by the weeds producing some substance be partly related to the rather which is i uniform depth of the lagoon, which resulted ability of in weeds becoming quickly established right across the basin, and fully for s relations between the two are likely be expressed dence on to rnore subtly in bodies of water with shores that Hegrash and N4atvienko (19G5), who found that slope more gently. aqueous extracts of a variety of macrophytes at times inhibited growth in cultures of Myxophy- Hasler and Jones (1949) rvere able ro demon- ceae. The eeneral significance of these results is strate an antagonistic effect of macrophytes on not clear. If there is an inhibitory substance, it is Rotifera, but not on planktonic Crustacea. fn clearly rather specific in its efÏects, as the filamen- Tomahawk Lagoon the decline in phytoplankton tous attached algae Spirogyra and Rhizoclonium productivity in 1965 was accompanied by a similar grerv in the weed-filled tanks of Hasler ancl Jones decline in all the major groups of the zooplankton, in the first vear of their studv, and there is some- rvhich included Rotifera, Cladocera, and Cope-

64 poda. These results u'ill be presented in a later are used, production will be, on average' 55 to 60 paPer. percent of daily production (Vollenweider, 1965)' METHODS As r,vith the method used in this study, however, this method is likely to be inaccurate in regions Although the "C and L and DB methods are where climatic conditions are unstable. It has been probably the best available methods for measuring claimed that amore accurate correction is obtainecl trave potential phytoplankton productivìty, both by assuming that diurnal variations in P f area arc sources of error, and results represent only approxi- directly proportional to the variations in light mations to productivity in the waters sampled' The energy reaching the lake surface. Continuous light L and DB method, usecl in the early part of this recordings are made from sunrise to sunset on the study, was not well suited to Ltse in Lake Mahine- days that experìments are conducted, and the rangi or Lake Waipori owing to its lack of sensi- short-term estimates are corrected accordingll' tivity and th: lorv productivity of these lakes. It (Wetzel 196tìa). rvas also unsuitable for Tomahawk Lagoon at r\ further difficulty was experienced in convert- times because of the very high productivity, which rng P f area for 4-hour experiments to daily P f area. caused the v¡ater to become higlily supersaturated T'his was caused by a large s)'stematic increase in rvith oxygen and led to the formation of bubbles the transparencv of Tomahawk Lagoon in the in the sample bottles. latter part of 1965, ',1'hen the correction curve was A practical clifficulty rvas experienced with the derived, rvhich resulted in only the upper portion 'nC method in the estimation of the total carbon of complete depth profiles being obtained. As the dioxide concentrations of the lake waters. Neither ccrrection factors might be expected to vary with of the methocls used in the field gives accurate the fraction of a complete depth profile obtained, tesults in all circumsta.nces, and empirical correc- errors may have been introduced by the use of tions, basecl on comparisons with a more accurate these factors for Waipori and Mahinerangi and laboratory method, were sometimes necessary. even for the earlier results from Tomahawk There appears to be a need for a methocl which is Lagoon, though it appears unlikelv that these accurate and adapted for use in the field. would have been large. Various starting times and experimental periods Several methods have been used for standard- have been used for productivity experiments by ising the "C method. l\4ost workers have precipi- clifferent investigators. It has been shown that tated the "C as barium carbonate and have plotted rates of tnC assimilation are reduced when samples self-absorption curves from planchettes having are exposed to natural light for more than 3 to 6 varying thicknesses of barium carbonate. The hours (Vollenrveider and Nauwerck 1961), but curve is then extrapolated to zero thickness. The if a short experimental period is used, the correc- extrapolation can be only a.pproximate, and results tion factors.necessar)¡ for the calculation of dail,v obtained with this method have been shown to be production nust be determined. Irregular fluctua- as much as 27 percent too low (Jitts and Scott tions in light intensity introduce an error into the 1961) or 31 percent too high (Steemann Nielsen correction, rvhich in this region is possibly greater 1965). This problem has been overcome by com- than that resulting from "bottle errors" during a busting plankton samples and counting the "CO, longer exposure. For Tomahawk Lagoon hourl,v in the gas phase (Goldman 1960a, 1963); or by rates of production for the period sunrise-sunset the use of Chlorella to collect the 'nCO, quanti- (calculated from short-term experiments) were on tatively (Steemann Nielsen 1965); or more in- average 70 percent of the corresponding rates for directly by forming a film of 'nC-labelled plastic a 4-hour period in the middle of the day. The which is assumed to be infinitely thin. The absolute correction showed no significant variation with activity of the film is then determined by liquid day length, but this may have been due to the scintillation counting (Jitts and Scott 1961). The influence of irregular diurnal fluctuations in light techniques used for standardisation in this study intensity. It has been suggested on theoretical have not previously been used for this purpose' grounds that if the period sunrise-sunset is divided The method is direct, precise, and easy to use, into five equal periods, Pf arca will be equal to and has the advantage that knowledge of the about 30 percent of daily production during either absolute efficiency of the liquid scintillation coun- the second or third period. If both of these periods ter is not required.

65 SUMMARY

In Lake N4ahinerangi, a power-supply reser- Phytoplankton productivity per unit volume in voir, the phytoplankton productivity as estimated Lake Waipori was slightly higher than that in by the 'aC method is comparable rvith that in the Lake Mahinerangi, though production for the least productive temperate lakes that have been water column was lower because of the shallorv investigated. Mean rates of production in the depth. Annual mean rates for the daylight hours, daylight hours in 1964-65 were 2.02 mg of carbon/ as estimated by the 'aC method, were 3.32 mg oí mt.hour at near-optimal light intensity (P-"*) and carbon/m'.hour (P-u*) and 26 mg of carbonfrn2. 76 mg of carbon/m2.day. day. Because of the shallow depth and moder- Multiple regression analyses showed that 78.3 ately high transparency of Lake Waipori the maxi- percent of the variation in hourly Pn,"* during mum in productivity often occurred in the lower 1964-65 could be accounted for by va"riations in half of the water column and on these days a temperature, water level, and day length. The decrease in surface light intensity would, within partial regressions on both temperature and water certain limits, have caused production for the level were highly significant (P < 0.001). Th. water column to increase. partial regression coefficient for day length was The concentrations of ionic solutes were slightly negative, but was significant only at a much lower higher than those in Lake N4ahinerangi. Phosphate level probability of than this (0.01 < P < 0.05). concentrations were generally highest after the During summer and autumn, when productivity sediments had been disturbed by strong wave was highest, large fluctuations in productivity were action. Oxygen concentrations at sunrise were recorded at the main sampling station at Lake rvithin the range of 84-98 percent of saturation. Mahinerangi and these appeared be related to Tomahawk Lagoon No. 2, a shallow fresh water largely to variations in temperature. Results coastal lagoon, is dominated alternately by phyto- obtained during periods when the seasonal cycles plankton and by macrophytes in an irregular cycle. were more stable indicated that productivity in- Betrveen July 1963 and Nlarch 1965 phyroplank- creases from the uppermost basin to the third one ton productivity was high. l\4ean rates of produc- and then changes little from one part to another tion for the daylight hours, as estimated by the down the lake. The annual minimum, which was '*C and light and dark bottle oxlrgen prcduction rvell defined, occurred in early spring. methods, rvere 157 mg of carbon/m'.hour (P-u*) The annual production of oxygen by photo- and 741 mg of carbon/m2.day. The absence of synthesis in Lake Mahinerangi, as estimated from any large crop of macrophytes during most of this bottle experiments during 1963-6+, amounts to period was probabl), due largely to light exclusion only about half of the annual consumption by by the large crop of ph,vtoplankton in the overlying respiration. water. There tvas a lvinter bloom of a blue-green alga (pc'ssibly Anacystis incerta Drouet and Daily) The concentrations of soluble reactive phosphate in 1963, and a bloom of Anabaena ranged from 0.5 to 3.0 mg of POn-P/m, and July flos-aquae (Lyngbye) Brébisson in December 1963 ancl- showed no seasonal pattern of variation. Concen- Janu- ary 1964. This was followed immediately by a trations of other ionic solutes were low by com- bloom of mixed composition. In the summer of parison with those in other Nerv Zealand lakes. 1964-65 Anabaena occurred later, after a bloom Oxygen concentrations at sunrise were within the of a red Gymnodinium species December and range of 90-101 percent of saturation and did not in vary with depth. January. During the Gymnodinium bloom there was an increase in the transparency of the water, In almost all of the samples from Lakes À4ahine- and a large crop of the aquatic rveeds Myrioþhyl- rangi and Waipori, rvhich lie on the same river Ium elatinoides Gaudichaud-Beaupré and Ranun- system, the most abundant phytoplankton were culus fluitans Lamouroux developed. These per- Cyclotella stelligera Cleve and Grunow and one sisted for at least 16 months, during r+'hich the of two species of Gymnodinium (.G. limitatum phytoplankton productivity was remarkably low Skuja and G. sp.). bv comparison rvith the earlie¡ results. The mean

66 Toma- Oxygen*Lugoo.t concentrations at the surface in hawk during 1963-64 were within the range of ZS'|OZ percent of saturation at sunrise ¿rnd 41-162 Percent at noon' Variations in the phytoplankton productivity of Tomahawk Lagoon were reflected quite closely by inverse variations in the Secchi disc transparency' This relation was not shown for Lake Mahine- rangi, though the Mahinerangi data were scattered about the iegression line fitted to the results for some r\pril 1966, and there clined at time after Tomahawk Lagoon. were again blooms of Anabaena and Gymnodinium in the summer of 1966-67. For the three lakes the coefficient of correlation and the con- Large amounts of phosphate entered the lagoon between phytoplankton productivity from 0'51 to in May-June 1965 as a result of heavy rainfall centration of chlorophyll ø varied the mean after superphosphate was applied to pastoral land 0.84. When the lakes were compared in the in the drainage basin. This remainecl in a soluble assimilation per unit chlorophyll decreased reactive form for only about 2 weeks. Phytoplank- sarne order as the mean productivity. not increase until 5 weeks ton productivity did Phytoplankton productivity, as estimated by the phosphate rvas added, and this pulse after the method, varied between 36 and BB percent of Factors other than phos- "C lasted for only 3 weeks. light and dark bottle oxygen production estimates phate might have contributed to the increase in of gross productivity when the methods were com- of productivity productivity, and though the level pai.d aiiectly in 4-hour experiments in Tomahawk period was high in relation to that during this Lagoon. during most of 1965, it was still very low bY comparison with that in 1963 and 1964. The 'nC method was standardised by wet com- There was a gradual increase in the concentra- busting labelle d plankton samples to carbon tion of soluble reactive phosphate in Tomahawk dioxidã, which was absorbed in hyamine hydroxide Lagoon throughout the spring and summer of and counted in a liquid scintillation counter' The of 1965-66 to a maximum concentration of 133 mg carbon dioxide that was evolved when aliquots of POo-P/m'. Phosphate of allochthonous origin the labelled bicarbonate solu'tion were acidified did not appear to contribute to this increase. rvas absorbed and counted in the same way,

67 ACKNOWLBDGMENTS

This bulletin has been derived from a thesis of the Chemistry Division, Department of Scien- submitte d to the University of Otago for the tific and Industrial Research, for making a num- degree of Doctor of Philosophy, 1967.I thank the ber of chemical analyses. following: 'fhe New Zealand University Grants Committee for a research grant; the Otago I also thank the following members of the stafi Acclimatisation Society for financial support from of the University of Otago: Dr G. W. Emerson, of 1963 to 1965; the New Zealancl lvlarine Deparr- the Biochemistry Department, for instruction in ment for financial support from March 1966; Dr the techniques used for standardisation of the D. Scott, the supervisor of this project, for his 'nC method; Dr R. F. Entwistle, of the Physics guidance; Dr G. R. Fish, of the Marine Depart- Department, for advice on counting methods; Mr ment, Dr V. M. Stout, of the University of Canter- R. H. lvlcKeown, of the Pharmacology and Phar- bury, and Dr R. G. Wetzel, of Michigan State macy Department, for advice on chemical methods, IJniversity, for their helpful comments on the and the heads of their respective departments for original presentation; Dr E. A. Flint, of the Soil the use of laboratorv facilities; and Mr T. G. Bureau, Department of Scientific and Industrial Robertson, of the Mathematics Department, and Research, and Dr G. A. Prowse, of the Tropical Mr K. W. Duncan, formerly of the Department Fish Culture Research Institute, Malacca, foi the of Zoology, for their comments on mathematical identification of algae; Miss R. Mason, of the aspects of the work. Botany Division, Department of Scientific and Industrial Research, for identification of macro- The Taieri Anglers' Club, Mr R. Shrubsole, phytes; Dr R. M. Cassie, of the University of and Mr J. R. G. Scott have made boats and huts Auckland, for providing the comp-,rter programme available. Others, too numerous to mention in- used for the multiple regression analyses and for dividually, have provided assistance in the field or carrying out the computin.q; and Mr G. R. Scott helped in other wa)¡s, and I thank them also.

68 RBF'BRENCES

ANornsoN, G. C., and BaNsn, K. 1965: Chlorophylls in Gor-orvraN, C. R. 1960a: Primary productivity and limiting marine phytoplankton: correlation with carbon up- factors in three lakes o[ the Alaska Peninsula. E¿ol. take. Deeþ Sea Res. 12: 531-3. Monogr.30:207-30. ANtre, N, J., McAlr-rsTr:n, C. D., PansoNs, T,-_B., 1960b: Molybdenum as a factor lirn'ting primary 'Srnpr¡äÑs, K., and St*tcxr-aÑo, J' D. H. 1963: productivity in Castle Lake, California. Science, N.Y., Further measuiements of primary production using a 1 32: 1016-7. large-volume plastic sphe:e. Limnol. Oceanogr. B: 1962: A method of studying nutrient limiting I 66-8 3. factors in situ in water columns isolated by poly- Anrnue, C. R., and Rtclnn, F. H. 1967: A possible source elhylene frtrn. Limnol. Oteanogr. 7: 99-101. 1aC of measuring primary pro- of error in the method - 1963: Thc measrÌrement of primary productivity and ductivity. Lirnnol. Oceanogr. 12: l2I-4. limiting factors in freshwater with carbon-14. In BanNerr, A. M., and Hrnore, J Doty, M. S. (Ed.), "Proceedings of the Conference apparent rate of 1aC uPtake on Þrimary ProduCtivity Measurement, Marine and period in natural phytoplan Freshwater", pp. 103-13, TID-7633. U.S. Atomic Oceanogr. 12: 349-53. Energy Commission, Division of Technical Inforrna- Bucn, K. 1933: On boric acid in the sea and its influence tion, Tennessee. int. on the carbonic acid equilibriurn. J. Cons. þerm' 1964: Primary productivity and micro-nutrient limit- ExþIor. Mer B: 309-25. ing factors in some North American and New Zearand. C¡ssr¡, R. M. 1962: l\{icrodistribution and olher error com- lakes. Verh. int. Verein. theor. angeut. Limnol. 15: ponents of C1a primary production estimates. Limnol 365-7 4. Oceanogr. 7: l2I-30. plant pigments and gro:s Colorra.n, C. R., and lvl¡,sox, D. T. 1962: Inorganic pre- 1963: Relationship between productivity utilis- primary production in Skeletonemd, costotum. Limnol. cipitation of carbon in experiments 136:1049-50. Oceanogr. B: 433-9. ing carbon-14. Scien.ce, N.Y., CoNovnr, S. A. M. 1954: Observations on the structure of Gor-olreN, C. R., and Wnrznr-, R. G. 1963: A study of the red tides in Nerv Haven Harbor, Connecticut. J. mar. primary productivity of Clear Lake, Lake County, Res. 13: 145-55. California. Ecology 44: 283-94. Cooenn, L. H. N. 1948: Some chemical considerations on Fl.,rlrrrr:n, U. T. 1964: The srLccession of "bloom" species of the distribution of iron in the sea. l. mar. biol. Ass. blue-green algae and some causal factors. Verh, int. U.K. 27: 314-21. Ver¿in. theor. angeu. Limnol IS: 829-36. - 1958: Consumption of nutrient salts in the Englisli Il¡s¡-¡n, A. D., and Joxrs, E. 1949: Demonstration of the Channel as a means of measuring production. Ra1y'. antagonistic action of large aquatic plants on algae - P.-u. Réun. Cons. þerm. int. Exþlor. Mer 144:35-7' and rotifers. Ecology 30: 359-64. Dorv, M. S., and Ocunr, M. 1957: Evidence for a photo- Hocn.lsn, A. I(., and M,lrvrexro, S. O. 1965: AJgicidal synthetic daily periodicíty. Limnol. Oe eanogr' 2: properties of aquatic and shore plants of the Kremen- 37 -+0. chug Reservoir with respect to the blue-green algae 1958. Selected features of the isotopic carbon pri- Llicrocystis þuluerea and, Anabaen.a hassalü. Míkro- mary productivity technique. Raþþ. P.-u. Réun. Cons. biol. Zh. Akad. nauk. UKR RSR 27 (2):39-42. (In - þerm. int. ExþIor. Mer 144:47-55. Russian ) Cited f.rotn BioI. Abstr. (1966) 47: 3005 Dnooe, M. R. 1962: Organic micronutrients. In Lewin,.R. A (No. 35596). (Ed.), "Physiology and Biochemistry of Algae", pp. IInnoN, J. 1962: Detelmination of phosphate in water after 149-59. Academic, New York. siorage in polyethyler-re. Lirnnol. Oceanogr. T: 316-21. Factors affecting productivity in Eorrorvnsow, W. T. 1955: 14 measnrements primary and Oceanogr., llonnra, J. E. 1964: Carbon of fertilized salt water'. Paþ. mar. BioL production Alaskan lakes. Verh. int. Res. (suþþ|.): 451-64. in two Arctic Deeþ Sea 3 Verein. theor. øngeu. Limnol. 15; 360-4. Enrono, L E. 1967: Temporal and spatial differences in phytoplankton productivity in Marion I.ake, British Hltvp Columbia. I. Fish. Res. Bd Can. 24: 2283-307. ErNsrr-r, W. 1941: Die lJmsetzung von zugeführtem,.qn- oiganischem Phosphat im eutrophen See und ihre seinen Gesamthaushalt' Z. Fisch. Rückwirkung auf Technical Information, Tennessee. 39:407-BB. Fer-rör-ov, L. J. M., and Kar-ró, Z. F, I95B: The rate of HurcrrrxsoN, G. E. 1957: "A T¡eatise on Limnology: Vol. photosynthesii and nnderwater radiation in Lake I-Geography, Physics, and Chemist¡y." Wiley, New Balaton. Observations of summer 1957. Annls Inst. York. 1015 pp. biol Tihany 25: 303-29. (In Hungarian with an 1967: "A Treatise on Limnology: Vol. II-Intro- Bnglish summary.) duction to Lake Biology and the LimnoplanÏton." Foco, G. E. 1963: The role of algae in organic production Wiley, New York. 1115 pp. in aquatic environments, Br. þhycoI. Bull.2: 195-205. Jrrrs, H. R., and Scorr, B. D. 1961: The determination of Focc, G.8., and Werr, W. D. 1965: The kinetics of release zero-thickness activity in Geiger counting of C1a of extracellular products of photosynthesis by phyto- solutions used in marine productivity studies. Limnol, plankton. Memorie Ist. ital. Idrobiol. IB (suþþ1.): Oceanogr.6r 1 16-23. 167 -74. study of some New Zea- Foco, G. E., Ner-owe¡ro, C., and Warr, W. D. 1965: Jorr,v,- V. H. 1959: A limnological products phytoplankton photosyn- land lakes. (Ph.D. Thesis, lodged in University of Extracellular of library.) thesis. Pro¿. .R. ,9oc., Ser. B, 162: 517-34. Otago Fnnen, G. L., and JouNstow, J. 1929: The solubility of JóNlssow, P. M., and MlrnrnsnN, H. 1959: Measurements calcium carbonate (calcite) in certain aqueous solu- of primary production in two Danish eutrophic lakes, tions at 25'.1. Am. chem. Soc.51 :2082-93. Esrom Sp and Fures4. Oikos 10:137-67. Gaenoen, T., and Gnar..t, H. H. 1927: Investigations of the Joncr,wsrN, E. G., and Sreru¡,rqx Nror-snN, E. 1965: prodrrction of plankton in the Oslo Fjord. Raþþ. P.-u. Adaptation in plankton algae. Memorie Ist. ital. Ráun. Cons. þerm. int. ExþIor. Mer 42: 7-48. Idrobiol. IB (suþþ1.): 38-46.

69 KnTcnuu, B. H. 1939: The development and restoration Nrlsorv, P. R., and EouolvosoN, W. T. 1955: Limnological of deflciencies in the phosphorus and nitrogen com- effects of fertilizing Bare Lake, Alaska. Fishery Bull. position of unicellular plants. /. cell. comþ. Physíol. Fish Wildl. Seru. U.5.56; 415-36. 13:373-Bl. Onr-r, W. 1952: Die hypolimnische Kohlendioxyd-Akkumu- 1954: Mineral nutrition of phytoplankton. A. Re¿. lation als produktionsbiologischer Indikator. /¡clr. PI. Physiol. 5: 55-74. Hydrobiol. 46 : 1,53-285. KnrsrreNsoN, J., and Merrrrosolv, H. 1964: Phyloplankton 1958: Diurnal production and destruction rates of of the T'ystrup-Bavelse Lakes. Primary production and phytoplankton in lakes. Raþþ. P.-u. Réun. Cons. þerm. standing crop. Oikos 15: l-43. int. Exþlor. Mer 144: 129-31. LuNr, W. 1949: Studies on Asterionellø. The origin J. G. I. planktonic green alga at and nature of the cells producing seasonal maxima. östonr-Irn, S. 1947: G¡owth of a EcoI. 37: 389-419. various carbonic acid and hydrogen-ion concentra- J. tions. Nature, Lond., 159: 199-200. 1950a: Studies on Asterionella fornosa Hass. II. Nutrient depletion and the spring maximum. Part I. 1948: Influence of low bicarbonate concentrations on the growth of a- green alga. Nature, Lond., 161: - Observations on Windermere, Esthwaite Water and Blelham Tarn. /. EcoI. SB: l-14. 3 l 9-20. Pernuer, R. 1951: The development of the Dunedin C.C. 1950b: Studies on Asterionellø lormosa Hass. IL depletion and the spring maximum. Part II. Electrical Department and its associated Waipori Nutrient hydro-electric scheme. elect. (11): Discussion. EcoI. 38: 15-35. Falls N.Z. J.2a J. 926-3 l. 1964: Primary production and periodicity of phytoplankton PensoNs, T. R. 1966: The determination of photosynthetic (Edgardo Baldi Memorial Lecture). Verh. pigments int. Verein. lheor. angeu. Límnol. 15: 37-56. in sea-water. A survey of methods. UNESCO Monogtaþhs on Oceanographic Methodology 1: 19-36. 1965: The ecology of the freshr¡,ater phytoplankton. Biol. Reu. 40: 231-93. Pensors, T. R., and Srnrcrr-eNo, J. D. H. 1963: Discus- sion of spectrophotometric determination of marine- l\'fcAr,r-rsran, C. D. 1961: Decontamination of filters in the plant pigments, with revised equations for ascertain- C1a method of measuring marine photosynthesis. ing chlorophylls and carotenoids. I. rnør. Res. 21: Limnol. Oceønogr. 6: 447-50. 1 55-63. McAr,lrsrn,n, C. D., Pansoxs, T. R., Srnerrr,Ns, K., and P.l,ntnrocn, B. P., and ScHnoroen, W. C. 1932: Determina- Srercrr-axo, J. D. H. 1961: Measurements of tion of hydroxide and carbonate in boiler waters. I. primary production in coastal sea water using a Methods. Ind. Engng Chem. ønalyt. Edn 4: 271-3. large-volume plastic sphere. Limnol. Oceanogr. 6: Pnenser-r-, W. H., and lJr-ryorr:, P. 1934: Light penetration 237 -58. into fresh water. III. Seasonal variations in the light McAr-r-rsrrn, C. D., Sue.u, N., and Stnrcrr.aNo, J. D, H. conditions in Winderme¡e in ¡elation to vegetation. 1964: Marine phytoplankton photosynthesis as a l. exþ. Biol. 11; 89-93. function of light intensity: a comparison of 1949: Experiments a methods. Fish. Res. Bd Can. 21: 159-Bl. Pnerr, D. M. in the fe¡tilization of J. salt water pond. /. mar. Res. B: 36-59. by MAc

70 RvrHon, J. H. 1956: Photosynthesis in the ocean as a -- 1957b ' Fhoiosynthe:ic characteristics of sone fresh- function of light intensity. Limnol. Oceanogr. 1: water plankton dialoms in relation to underwater 6 1-7 0. radiation. Neu Phytol. 56: 29-50. Rvrnr,n, J. H., and MnNznr-, D. W. 1959: Light adaptation 1965: The photosynthetic activity of phytoplankton in marine phytoplankton. Limnol. Oceanogr. 4: 492'7. in East African lakes. 1zt. Reaue ges. Hydrobiol. S0: Rvrnnn, J. H., and Yr,Nr:scn, C. S. 1957: The estimation t-32. of phytoplankton production in the ocean from Trrorres, W. H. 1963: Physiological factors affecting the chlorophyll and light daTa. Lirnnol. Oceanogr. 2: interpretation of phytoplankton proCuction measure- 28 1-6. ments. f?x Doty, M. S. (Ed.), "Proceedings of the S.*anr, W. (Ed.) 1955: "Handbook of Isotope Tracer Conference on Primary Productivity Measurement, Methods." Department of BiochemistrT, School of Marine and Freshwater", pp. l+7-62, TID-7633. Medicine, Western Reserve University, Cleveland, U.S. Atomic Energy Comrnission, Division of Tech- Ohio. 188 pp. nical Information, Tennessee. SeuNlnns, G. W., Tn.+rra, F. B., and Becnnaewx, R. W. Ve.r,r Donrv, lV. G. 1 95 6 : Large-volume rvater sanplels 1962: Evaluation of a modified C1a technique for' Trans. Am. geoþhys. Un. 37: 682-4. shipboard estimation of photosynthesis in large lakes. \/rN Sr-vro, D. D., and For.crr, J. 1940: Manometric carbon gt Lakes Res. Inst. B. pp. Publs 6l determination. l. biol. Chem. 1 36 : 509-41. Suevoe, T. J. 1957: Phytoplankton studies in Lou'er Nar- \/rwnr,nc, G. G. 1963: "The Primary Production of Bodies Bay. Limnol. Oceanogr. 342-59. ragansett 2: of Water", AEC-tr-5692 (Books I and 2 ). U.S. Sutru, M. W. 1945: Preliminary observations upon the Atomic Energy Commission, Division of Technical fertilization of Crecy Lake, New Brunswick. Zr¿ns. Information, Tennessee. 601 pp. (Translation of Am. Fish. Soc.75: 165-74. "Pervichnaya Produktsiia Vodoemov", published by SNaor,con, G. W. 1956: "Statistical Methods Applied to the Institute of Biology of the Academy of Sciences Experiments in Agriculture and Biology." 5th ed of the Belorussian S.S.R., Minsk, 1960.) Iowa State College, Ames. 534 pp. Vocør-, A. I. 1951: "A Text-Book of Quantitative Inorganic SnonNrvesex, A. 1964: The limnology, primary production, Analysis. Theory and Practice." 2nd ed. Longmans, and fish production in a tropical pond. Limnol. Green, London. 918 pp. Oceanogr. 9: 391-6. Vor-r-¿Nwnronn, R. A. 1960: Beiträge zur I(enntnis optischer t'""'uñJ;,Jd"!.'fru.n..!i"I'Èä"."t*Tio':,;i?",:";:ii;i. Eigenschaften der Gewässer und Primärproduktion. Memorie Ist. ital. Idrobiol. 12:20I-44. , Mer 144: 79-84. --- 1965. Calculation models of photosynthesis-depth Srauo, f. H.. and Barn¡, I. B. 1961: Relations between curves and some implications regarding day rate esti- primary production, chlorophyll, and particulate mates in primary production measurements. Memorie èarbon. Limnol. Oceanogr. 6: 68-78, Ist. ital. Idrobiol. lB (suþþ|.):425-57. SroBueNl¡ Nrr,r-snN, E. 1952: The use of radio-active carbon Vor-¡-eNw¡r;nn, R. 4., and Neuwnncr, A. 1961: Some (Cla) for measuring organic production in the sea. observations on the Cr{ method for measuring primary !. Cons. þerm. int. Exþlor. Mer 18: Il7-40. production. Verh. int. Verein. theor. angeu. LintnoL. 1954: On organic production in the oceans. J. Cons. 14: 134-9. t þ"iîr:r',"'r!;o'::"#,:i":t Welr, W. D. 1966: Re'ease of dissolved organic material phytoplankton populations. R. matter by the from the cells of Proc. phytoplankton in a Danish"i"";Tic lake receiving extra- Soc., Ser. B, 164: 521-51. ordinarily great amounts of nutrient salæ. Hydro- Wrlcn, P. S. 1948: "Limnological Methods." McGraw-Hill, biologia 7: 68-74. New York. 38l pp. ' 1958: Experimental rnethods for measuring organic Wurznr-, R. G. 1964: A comparative study of the primaly production in the sea. Raþþ. P.-u. Réun. Cons. þerm. productivity of higher aquatic plants, periphyton, and int. Exþlor. Mer 144: 38-46. phytoplankton in a ìarge, shallow lake. Int. R¿uue 1959: IJntersuchungen ubel die Primärproduktion ges. Hydrobiol. 49 : l-61. in einigen Alpenseen Osterreichs. Oiftos 1965a: Nutritional aspects of algal productivity in des Planktons - 10 : 24-37 . marl lakes with particular reference to enrichment bioassays interpretation. Ist. ital. 1964: Recent advances in measuúng and under- and their Memorie standing nrarine primary production. J. Ecol. 52 Idrobiol. 1B (suþþ1.): 137-57, (suþþ1.); I 19-30. 1965b: Necessity of decontamination of frlters in . the determination of the activity in laC- C1a measured rates of photosynthesis in freshwaters' 1965: On 540-2. ampoules for measttring primary production. Limnol. Ecology 46: Oceanogr. 10 (suþþ1.): R247-52. 1966a: Variations in productivity of Goose and hypereutrophic Sylvan Lakes, Indiana. Inuest. Indianø SrnnrtlNx Nrnr-soN, E., and Ha,wsnN, V. K. 1959: Light adaptation in marine phytoplankton populations and Lakes Streams 7: 147-84. . its interrelation with temperatute. Physiologia PI. 12: 1966b: Productivity and nutrient relationships in I g53-70. nrarl lakes of northern Indiana. Verh. int. Ver¿in. J Srr,vr'N, D. M. 1966: Chalacteristics of a red-water bloom lheor. angew. Limnol. 16: 321-32. i in Kingston Harbor, Jarnaica, W.I. /. mar. Res. 24: Wnrcrr, J. C. 1954: The hydrobiology of Atwood Lake, a 1 13-23. flood-control reservoir. Ecology 35: 305-16. Srnrcrr-euo, J. D. H. 1960: Measuring the production of 1960: The limnology of Canyon Ferry Reservoir: marine phytoplankton. Bull. Fish. Res. Bd Can. 122. IIL Some observations on the density dependence of 172 pp. photosynthesis and its cause. LimnoL, Oceanogr. 5: t'*''"å1x?;J,"3,;X;,îî,*',1"äi?,)"¡'i 356-6 1. ï,1:%i t#."ä?' Ztcl<øn, E. L., Bancrn, K. C., and Hlsr-en, A. D. 1J56: = Phosphorus release from bog lake muds. Linnol. Oceanogr. l: 296-303. | 1^"tr*::trof. 1957a: Diurnal changes of stratification ancl phoLosynthesis in some tropical African waters. Proc. Zotøt-t, C. E. 1943: The effect of solid surfaces upon bac- R. Soc., Ser. B, 147: 57-83. terial activity. J. Bact. 46: 39-56. 7t APPENDIX I: EVALUATION OF METHODS

APPENDIX IA: METHODS FOR MEASURING pH

The X{etrohm pH meter was tested with a num- solution, and the sample rvas shaken vigorously for ber of freshly prepared buffer solutions and gave a few minutes before readings rvere taken with the accurate readings (-t0.05 unit) within a range of two methods. With the phenol red indicator the at least 1 unit from the pH at which it was zeroed. two methods showed satisfactory agreement, but It gave replicable readings for the lake waters, when the bromocresol purple indicator was used though about I minute was required for stabilisa- there was a considerable difference between the tion of the reading for samples from Lakes Wai- results (fig. 30). The curve fitted by eye to these pori and Mahinerangi. This instrument was con- data was used to correct the values obtained with sidered to give the best available estimate of pH the bromocresol purple indicator during the short in the field. period when this was used. This correction had to be applied only for estimates obtained with bromo- The Lovibond comparator w¿rs calibrated cresol purple that were within the range 6.4-6.6. against the Nletrohm meter with water samples The ex'treme va-lues in fig. 30 suggest that the cor- from Lakes Waipori and lVlahinerangi. The pH rected pH would not have been in error by more was adjusted by adding N/50 HCI or NaOH than 0.15 unit.

Mahinérangi lab, samples . Mahinerangi field samples X Waipori lab. sanrples ^

o o a = I XO o ^

6,2 6.4 6.6 pH ( lndicator ) Fig. 30: Iltercalibration of methods of estimation of pH in Lakes Mahinerangi and Waipori, showing the relation between results obtained with the Metrohm portable meter and the Lovibond compara-tor with bromocresol purple indicator.

72 Ihe pH of the bromocresol purple indicator is buffered waters, though these results might also 6.0, and its buffering capacity was possibly suf- have been produced by the presence of interfering ficient to lower the pH of samples from these poorlv substances in the water.

APPENDIX IB: MBTHODS TO DETERMINE CARBON DIOXIDE CONCENTRATIONS

Results

TABLE 19: Standardisation of the distillation-absorption method of estimating the total concentration of carbon TABLE 20: Comparison of the pH-alkalinity method with dioxide in water (the method of Partridge and Schroeder the distillation-absorption method in Lakes Waipori and (1e32)). Mahinerangi. III I II By rveight By absorption Difference pH-alkalinity* Absorption (mg C,/l) method (mg C,/1) II minus I method method Difference 5.45 -+0.2 5.95 +0.1 +0.5 Lake Date (mg C/l) (mg C/l) II minus I 8.75 -t-0.2 8.5 +0.1 -0.25 I4ahinerangi +/3/65 1.95 +0.15 2.15 +0.1 +0.2 7.55 -f0.2 7.35 -+0.1 1.95 +0.1 -r-0.2 +-0.1 -0.2 Mahinerangi 24/3/65 2.0 -0.05 1 1.0 11.0 0.0 Waipori 1/4/65 2.7 -+0.2=0.15 2.4 r-0.1 3.+ -r0.2 3.5 -{- 0.1 +0.1 -0.3 +.35 -+-0.2 +.6 +0.1 +0.2s The estimated precision of the pH-alkalinity method in all samples was the maximum error resulting from an error of 0.15 pH unit and an The estimated erroL for total error of 0.025 ml of N/50 hydrochloric acid for the alkalinity titration, titration error o1 0,2 ml titrations used in a single es ighed " pH was estimated with the Lovibond comparator and phenol red samples was assumed to ds to indica tor. a weighing er¡or of 0.5

TABLE 21: Comparison of the pfl-alkalinity method with the distillation-abiorption method in Tomahawk Lagoon. I II pH-alkalinity Absorption method method Difference Date (mg C/l) (mS C,/l) II minus I -r- 8/3/65 B.l '+0.25 7 .0 0.1 -1.1 15/3/65 8.65 -È0.25 7.3 -r-0.1 - 1.35 22/3/65 8.6 -f 0.25 7.4 -È0.1 -1.2 29/3/65 B.B5 +0.25 8.1 +0.1 -0.75 12/4/65 7.+ -t- 0.25 6.55 -r-0.1 -0.85 23/6/65 8.45 -f0.25 7.95 +0.1 -0.5 29/6/65 9.7 +0.25 B.B -+.0.1 -0.9 : Mean difference -0.95 Standard error : 0.11 'lhe estimated precision of tlre pH-alkalinity'hvdrochloric method corresponds to a total titration ãrror of 0 1 ml- of N,/50 acid for the estimation of the phenolphthalein alkalinity and the total alkalinity.

TABLE 22: Comparison of the pH-alkalinity method with the method of McKinney and Amorosi (19'f4) for the three Otago lakes' II I McKinney and Depth pH-alkalinity Amorosi method Difference Lake Date (m) (mg C/l) (mg C/l) II minus I Tomaharvk 18/1/65 0 t 6.5 -r0 25 15. 85 -r0.2 -0.65 Waipori r0/1/6s o 5.61 5.36 -0.25 l0/t/65 0.5 5.64 -+-0.2 5.45 -0.2 Mahinerangi 25/12/64 0 2 .05 -+'0. 15 t.20 r-0.15 -0.85 25/12/6+ 1.0 1.99 t,22 -0.7 s 27 /1/65 0 2.06 -F0.15 t.46 -0.60 27 /l/6s 1.0 2.03 -{-0. 15 t.57 -0.45 Mean difference : : -0.54 or, excluding the result fol Tomahawk Lagoon, mean 4ifference -0'51 and standard error : 0 10 The estimated precision of the pH-alkalinity method was calculated iu the sane way as for tables 20 aud 21. It Discussion alkalinitl'. There was also no clear evidence of a Standardisation of the Distillation-absorption relation to chloride concentration or to the Secchi approxi- Method: Results for the absorption method agreed disc transparency, which may provide an with weighed values to within the estimated experi- mate index to the amount of material in suspen- mental error for all but the first estimation. Mani- sion in the water. Some such relation could well pulative errors were probably high in this first exist, however, and remain hidden by experimental estimation and it was concluded that the distilla- errors. The i¡fluence of the salinity of Tomahawk tion-absolption method gave satisfactory results. Lagoon water on the expression used for the calculation of inorganic carbon with the pH-alkalinity Comparison of the pH-alkalinity Method with method was investigated bv an approximate deriva- the Distillation-absorption Method: Results ob- tion of the modified dissociation constants for the tained in Lakes Waipori and Mahinerangi from carbon dioxide system in water. The resulting cor- the two methods agreed to within the estimated rection amounted to less than 1 percent, so that errors. For these waters, which have very low total this was clearly of little importance. The mean of carbon dioxide concentrations, the estimated error the differences found was -0.95 mg of carbon/l for the distillation-absorption method was com- and this correction was applied to the estimates paratively large, and this method did not provide obtained with the pH-alkalinity method. a completely satisfactory neans of testing the pH- alkalinity method. However, results suggest that Comparison of the pH-alkalinity Method with the pH-alkalinity method was probably not in the i\{ethod of McKinney and Amorosi: The not error by more than about 12 percent. method of McKinney and Amorosi, though compared directly with the distillation-absorption The pH-alkalinity method gave results that were method, gave consistently lower values than the consistently higher than those for the distillation- pH-atkalinity method. McKinnel' and Amorosi absorption method for Tomahawk Lagoon. These report consistent negative errors for five standard differences varied from 6 to 15.6 percent of the solutions of carbon dioxide (0.75-14 mg of car- concentrations estimated by the pH-alkalinity bon/l) having no added impurities. These errors' method. report Partridge and Schroeder (1932) determined under laboratory conditions, had a that estimates obtained with the phenolphthalein- mean of 0.15 mg of carbon/I. A systematic nega- methyl orange method were consistently too high tive error is likely to arise in this methocl from the lor 12 solutions of known carbonate concentration difiusion of carbon dioxide into the sample at any (1.2-17 mg of carbon/l) having no added impuri- stage after the solution is boiled. The need to deter- ties. The mean of these errors has been calculated mine four titration end points would reduce the to be 0.16 mg of carlnnfl. They suggest that errors precision of results. The mean of the six differences are likely to be greater in the presence of salts of for Lake Waipori and Lake N{ahinerangi, deter- acids other than carbon dioxide, neutral salts, and mined in the field, was 0.5 mg of carbon/I. This colour in the solution. They report results which amount was added to the estimates obtained with are too high by as much as 15 mg of carbon/l for lVlcKinney and Amorosi's method for the five boiler waters and quote a number of other authors sampling dates at Lake Waipori and the four at as finding large positive or negative errors for this Lake Mahinerangi rvhen this method was used. method. This correction was about 10 percent of the pH- The differences between the results obtained alkalinity estimates for Lake Waipori and 25 per- with the two methods from samples from Toma- cent for Lake Mahinerangi. The concentrations hawk Lagoon did not appear to be related to the estimated for Tomahawk Lagoon with this BH, the total alkalinity, or the phenolphthalein method were not corrected.

APPENDIX IC: CALCULATION OF t4C ASSIMILATED IN PHOTOSYNTHESIS

The expression for total assimilation of 'oC in 4r0 (LV) the light bottle, adjusted to the standard counting X-X (.9cls-bgc/s) efficiency (410 c/s for the Perspex standard) and Std cls (VF) corrected for the individual bottle volume, is: where Std c/s is the counting rate for the Perspex

74 standard, LV is the volume of the light bottle, ZF The third term inside the square bracket was is the volume of sample filtered, S c/s is the count- neglected. With background radiation typically ing rate for the sample, and bg c/s is the counting 0.3 c/s, the differences between light and dark rate for background radiation. bottle volumes usually less than 5 ml, and total Similarly for the dark bottle: c/s per light bottle usually more than 10, the error +t0 (DV) produced by this was rarely more than 0.5 percent. x x (D cls bg cls) 1 - 'Ihe to Std cls --(VF) term was left inside the bracket r,vhere DV is the volume of the dark bottle and -VF D c/s is the counting rate for the dark sample. facilitate calculation with an electric calculating When the second is subtracted from the first, to machine. No correction was applied for the co- give the total c/s assimilated by photosynthesis in incidence error of counting. the light bottle, the expression reduces to:

410 (LV x S c/s) (DV X D cls) bg cls (LV - DV) Std cls Vþ' VF VF

APPEI\DIX ID: STANDARDISATION OF THB 14C METHOD

Nine plankton planchettes which had each been usecl. The mean of the duplicate samples was applied, counted to 10,000 counts after correcticn for back- taken, a volume correction of X 3.5 was ground radiation and relative counting efficiency Geiger c/s were selected for standardisation' These \ì,¡ere and the factor was calcu- chosen to represent all three l¿rkes and a range of Liquid scintillation c/s sample volumes. They lvere oxidised by the wet lated for each planchette. Results are presented in combustion method of van sll'þç and Folch table 23. There do not appear to have been any (1940) and the apparatus of Sakami (1955, p. 1). systematic differences in self-absorption between The carbon dioxide evolved was absorbed in 3.5 nil these samples. of 2N sodium hydroxide. Duplicate 1-m1 aliquots of the sodium hydroxide rvere then transferred to 30-ml bottles having a centre well to rvhich had been added 1 ml of 1.0 M hyamine hydroxide in TABLE counting rates obtained bY stoppered rvith rubber Geiger-M Clabelled phytoplankton on methanol. The bottles were Millipore tained by liquid scintillation serum caps, and 1.2 ml of 2N sulphuric acid was co bustion of the samples' added through the stopper to the sodium hydroxide syringe. The carbon dioxide Volume of with a hypodermic sample Corrected Geiger c/s evolved was transferred to the hyamine by shaking Date filtered Corrected liq. sc.c/s ( (mean) sc.c/s the bottle for 2 hours at 20" c. Lake 1964) (ml) Geiger c/s Liq. The hyamine was then transferred by syringe to Tomahawk 19/10 25 49.5 51 1.0 0.0969 7 - 0.102 3 6 ml of a liquid scintil- 19/10 25 7t.B 02.1 counting vials containing 26/ t0 25 26.5 280.+ 0.0945 lator consisting of 4 g of PPO/I and 0.05 g of 26/10 2s 42.2 401.8 0.1050 Three washes with l\tfahinerangi 2l / l0 50 17 .7 179.5 0.0986 POPOP/I in toluene. l-ml Waipori 28/10 50 7.96 72.5 0.1098 scintillator were used to bring the total volume to 28/t0 50 31.9 287.O 0.1110 Samples were counted for two 7-minute 19/ lt 25 22.5 218.0 0.1032 10 ml. 19/tl 25 t9.37 183.0 0. 1058 periods in a Packard Tricarb Liquid Scintillation Spectrometer to a minimum of 40,000 counts. A Mean : 0.1030 standard background correction of 0.5 c/s was Standard error : 0.0019

75 Eleven ampoules were chosen to represent a TABLE 24: Counts per ampoule of the stock solutiou of laCJabcllcd bicalbouate, ¿s dsls¡r¡ri¡sd by liquirl sulltill¿tlol range of times throughout the dispensing period. counting. The contents of each were transferred quanti- Ampoule Corrected tatively to a llitre volumetric flask containing (in order of liquid scintillation about 500 mg of A.R. sodium carbonate dissolved dispensing) - c,/s ( X 10-3) in distilled water. The volume wa-s made up to I 12+.63 , 1 r20.52 litre and three 1-ml aliquots were withdrawn, J I 18.30 added to transfer vessels, transferred to hyamine + tt7.4t 5 l2 1.15 hydroxide, and counted by the methods previously 6 127.41 described. These samples were counted for two t25.2t 121.15 5-minute periods. Counting rates were corrected 9 I 29.35 for background radiation, and means for the three 10 119.53 subsamples were taken. The number of c/s per l1 t21.30 ampoule was obtained by applying a volume cor- :: ,,."0".0lnil'] rection of X 1,000 to these means, and a mea¡r was "?.13 taken for the 11 ampoules. Results are presented Each figure represents the mean for th¡ee subsamples in table 24. The variation between the 1-ml subsamples was l-2 percent for each sample. ditions of self-absorption. fhe figure obtained was The mean for c/s per ampoule (122,360) was 12,603. As both the plankton samples and the sodium carbonate-taC solution were counted as Geiger c/s carbon dioxide in the same liquid scintillation multiplied by the factor system, knowledge of the absolute counting effici- Liquid scintillation c/s ency of this system was not required. It does not estimated from the wet combustion of plankton appear from table 24 that there was any significant samples (0.1030), to give c/s per ampoule at loss of 'nCO, by exchange with atmospheric carbon Geiger-counting efficiency under the existing con- dioxide during the 36-hour dispensing period.

APPENDIX IE: CALCULATION OF SATURATION VALUES FOR CALCIUM CARBONATE

The solubility product of calcium carbonate carbon dioxide. In this titration 4.66 ml of N/50 (K"n) - 4,9 X 10-'gmoles/l at 25"c (Frear and hydrochloric acid was used for a 100-ml water Johnston 1929). On 5 October 1964 the carbonate sample. This equals 9.3 X 10-'moles/I, concentration was calculated as follows: For practical purposes this may be considered IH.] [CO,=] to be the concentration of bicarbonate, since only _fa r\2 0.32 percent of the acid was used converting - in LHCO,-l carbonate to carbonic acid and carbon dioxide. : 3.2 10-" (Buch 1933) X Therefore therefore [CO.=] 3.2 X 10-" [CO,=] : 9'3 X 10-n X 1'6 X 10-'moles/l : 1.49 X 10-u moles/l [HCO,-] [H.] The maximum amount of calcium that would The pH wusT.7 enter solution therefore IH.] : 2X 10-'moles/l Ksp [c^..] - moles/l therefore ICO'=] 3.2 x 10-" Ico.=] [HCO,-] 2 x 10-' 4.9 x 10-' moles/l :1.6X 10-' 1.49 X 10-. In the alkalinity titration carbonates and bi- carbonates are converted to carbonic acid and 132 rngll

76 77 APPENDIX IT: RESULTS

APPENDIX IIA: PRODUCTIVITY DATA

In this appendix the following reference marks indicate: + Negative values. f Obtained by extrapolation. f Samples diluted with distilled water. $ All samples from the surface.

TABLE 25: Phytoplankton productivity in Tomahawk Lagoon(mg oi carbon/m5.hour) measured by ttre L and DB method, Date 0m 0.25m 05m 0.75m 1m 1.25m Date 0m 0.25m 0.5m 0.75m 1m 1.25m

'27 18/7/635 300 132 23 2 Sross / r/6++ 683 482 I gross 276 108 * * net (morning) 594 393 *i net 28/7/635 204 gross ¿7 / | /64f. 599 gross t87 net (afternæn) 503 '36 'tit net t2/8/63 BB s5t 32 2t 13 gross 6/2/645 79 st ,it gross s5 221 ** net (morning) 5B t5 *l *t *t net 20/8/63 133 6B 231 B.+ lt gross 6/2/645 6B 72 gross 96 30 *t**t net (afternoon) 43 +B net 2/9/63 156 61 t4 121 10 gross Ll/2/64 250 lB5 130 50t 2r gross t22 28 **f* net 218 r53 6r net 9/9/63Ê 149 52 4tt gross tB/2/6++ 659 87 -2t -3t5 gross **t 285 20t 131 33 I net 495 122**t* net t6/9/63 tt7 69 13 gross 2+/2/64t. 464 Lr2 22 B 3t gross 100 52 **t*-t net 398 +7***t net 23/9/63 83.6 63.7 9.? 4t gross s/3/6++S 682 67 gross 71.3 5r.4 .**f net 502 *** net 30/9/63 177 l 19 gross t6/3/645 2BB 31 I gross t57 99 net 246 *** net 7/t0/63 B+ 55 .1 sross 23/3/6+S 277 6284-t gross 4+ 16 net 250 35++*t net 1+/10/63 1 gross 30/3/648 gross cn+ 4tt 69+- ** net 391 49** net 2t/10/63 I 1.9 gross 27 **¡3.1 t 6/+/64Ë 323 136 31 t3 +l Sross 16* I net 274 87***t net 28/t0/63 153t 153 51 9 4t gross t+/4/645 363 159 22 gross 125t t25 17**t net 339 135 * * net 4/11/63 126 34 3-t gross 20/4/64 261 75 26 r+ 7t gross **r 82* I net 235 +g**t net 1t/rt/63s 84 54 t7 6t 3t gross +/s/64ï 25 14663t gross 52 22 **t*+ net 11 ***t net 18/tr/63 38 43 31 23 15t gross *l 1r/5/6+ 54 25t r0 4.51 2t gross 18 23 11 2 net 36 net 76 10t gross 1l**t*t 25/11/63 29 28 gross 30 net 22/5/645 62 76255-l 51 net 3/t2/63-46 119 97 -977 -2836 -+6125t gross 6514**t 100 78 55 13 2l net B/6/6+5 137 498- gross 9/12/63 t22 77 4t 19 10t gross 116 28** net B+ 39 3x*t net 15/6/6+ 87 1o272BT gross t6/t2/63 70 l 10 95t 61 40t gross 62 7758*t net 69 109 s4I 60 3et net 22/6/645 95 BB 46 20 9t gross 23/t2/635 LBï 239 90t 3ot I gross 65 net * 5815**t 154 210 61t lt net '29/6/6+ 36 74 52 29 lst gross 6/1/6+ 439 280t r73 19 5t gross 26 65 43 20 6t net 175t net 33+ 69** 6/7 /6+ 66 72 50 35t 251 gross 7/t/64I 278 91 251 10t 5t gross (morning) 50 eî net 172 n *t *t *t nct 56 3+ rsl 6/7 /6+ 54 59 gross 10/r/64 502 116 30 I 1.5t gross (afternæn) 445 59 **t*t net 4I 3+ net t3/r/64| 450 tzg 37 12 6t gross 20/7 /64 26 41 4t 32 25t gross 360 38 ***l net 17 31 3l 22 15f net 20/t/64I5 725 lB5 t2 gross 11/B/6+ 3B 521962t gross 676 1 36 net 34 +8153*t net

78 Waipori TABLE 262 Phvtoolankton productivitv in Tomahawk TABLE 28: Phfoplankton productivity in lake 'caibon/m5.hõur) measured by the l4C measured by thê L and DB metlod' Lagoon (o's of |^lil "irt""/rÁ¡'hïur) method ( not corrected to a sunrise-sunset experimental Date 0 m 0.25 m 0.5 m 0.75 m period). 28/ tr/63 6.39 9.26 6.39 Sross Date 0m 0.25 m 0.5 m 0.75 m 1m + 1.76 +.63 1.7 6 net 9.69 5.21 9/r/6+ 1.87 7.26 +.57 gross 14/9/64 28.l 23.5 16.2 net 2t/9/6+ 30.+ 50.2 31.9 20.0 10.01 +.77 2.0B 6.06 gross 5 28.l 47.7 26.3 23/r/64 t.25 5.85 / t0/64 s2.3 net t2/ ro/64 16.9 54.9 52.2 3+.O 2 93 l 46 24.0 5/3/64 t.02 4.32 5.08 5.08 t gross 19/ t0/6+ 45.3 93.6 76.6 * 34.4 31.2 8.5 0.76 1.52 1.52f net 26/ t0/6+ 52.4 net 9/ tr /64 66.1 53.9 2.87 0.41 21/3/6+ 5.43 7.23 7.23 4.771 2/12/64 i9.1 57.5 3+.9 16.7 2/4/645 9.52 . 5.6 3'70t gross t+/12/6+ 44.0 111.0 97.4 43.4 6.44 , 2.52 0.62t net 49.1 B+.7 67.9 16/+/645 6.01 5.41 3.31 2.00t gross 28/12/64 96.7 net tB/ r/65 52.7 34.3 16.6 5.41 4.81 2.7 I 1.40t 32.0 77.3 4+.2 t6/5/64 4.5+ 6.29 6.64 6.64t gross 25/r/65 72.0 net r/2/65 59.8 7 0.6 50.2 47.6 2.79 +.5+ 4.89 4.891 B/2/65 61.0 101.5 91.6 60.0 2/7 /6+g 0.7 + 6.65 7.02 7 .021 sross 22/2/65 55.7 60.8 38.6 4.06 4.+3 4.+3t net 82.0 * gross 1 .2 65.8 t3/B/6+ 3.86 4.18 4.18t B/3/65 106.3 9l .3 147 * t5/3/65 167.0 85.5 38.6 7.0 2-89 3.22 3'221 net 22/3/65 46.1 t1+.4 103,1 74.0 5/+/65 17.8 32.2 31.3 24.4 12/+/6s 22.6 20.0 17 .0 I 1.6 TABLE 2 in Lake WaiPoti 26/4/6s 7.38 5.89 +.93 1 1.6 (ú 14C method. (not 6/5/65 13.4 16.8 19.1 16.3 "fcorre "; ental Period)' 17 /5/65 0.98 1.82 1.76 1.69 3r/5/65 2.5+ 2.08 1.66 1.01 Date 0 m 0.25 m 0.5 m 0.75 m 7 1.57 1.7 6 1.31 /6/65 1.89 t7 /e/6+g 0.,1 1 0.55 0.59 0.59 t 28/6/65 3.59 3.7 t 3.23 1.61 t4/ to/6+ 0.71 2.91 3.95 3.9s t 5/7 /65 12.9 t+.2 9.78 5.7 0 28/10/64 0.67 3.45 3.73 3.73 t r7.3 1 0.10 12/7 /65 +,97 16.+ t9/tl/64 O.BB 4.09 4.Bo 4.Bo t rs/7 4.48 10.4 8.66 /65 5.77 7 /t2/6+ tt.37 13.20 11.30 8.70t 26/7 /6s 2.20 2.12 1.84 2.19 23/t2/6+ 5.69 6.18 5]0 4.10 t 2/B/65 0.58 1.02 l.l7 1 .12 20/r/6s 4.98 7.85 12.40 12.40 t tr/B/65 0.69 0.94 0.87 0.78 +/2/65 3.35 7.05 10.25 10.25 0.84 t 23/B/65 0.48 0.93 0.95 t7 4.23 5.78 5.33 3.Bl 0.66 /2/6s t 30/B/65 0,44 0.82 LO/3/65 3.78 5.2I +.30 3.3 0 t5/9/65 1.49 1.99 1.93 1.35 r/4/65 0.48 1.10 0.99 28/9/65 0.86 Station 1 1.69 3.65 3.68 3.70 0.85 t +/ t0/65 0,5 2 t.L7 1.01 Station 2 4.45 L9/10/65 0.66 t.79 1.69 2.20 22/4/65 t"?2 r.eö 1.35 1.08 26/ r0/65 1.41 3.20 3.05 2.96 t4/5/65 t.+5 2.3+ 3.08 3.08 t 3/rt/65 1.30 3.96 4.53 5,14 2r/5/65 B/ 2.82 2.58 1.95 tt/65 3.29 Station 1 0.62 l.B9 1.85 | ,25 2.30 2.00 I 22/ rt/65 2.93 2.5+ Station 2 2.37 26/ rr /65 1 .95 +.73 3.15 too3.05 2/6/65 13/12/65 2.53 3.30 1.79 Station I r.92 3.36 3.+7 3.47 1.48 I .89 1.59 I 3/r/66 1.90 Station 3 1.96 16/6/65 2.65 4.41 4. 1 0 2.91 I TABLE 27: Diurnal variations in phytoplankton productivity 30/6/65 in Tomah¿wk Lagoon as estimated by the laQ method. Station 1 2.+9 3.23 3.+9 3.49 + 2 +.24 Duration Production (mg C/ma) Station (h.) 0m 0.25m 0.5m 1m 15/7 /65 Date Experiment Station I t87 2.68 2.68 t l2/7 /65 Morning 2.65 19.9 24.3 22.8 13.9 Station 2 2.06 Midday +.0 19.9 65.7 69.2 40.3 2B/7 /65 Afternoon 2.55 15.3 22.7 t6.+ 6.0 Station 1 0.42 0.BB 1.25 1.2s t S'tation 2 2.03 2.4+ 30/B/65 Morning 3.3 L26 0.90 1.00 19/B/65 Midday +.0 t.7 6 3.30 2.65 Station 1 0.38 0.89 1.55 1.7s Afternoon 3.45 r.7 t 1.80 1.70 Station 2 1.00 t.7 3 r/9/65 +/10/65 Morning 4.35 2.08 3.09 3.07 2.86 Station I 0.54 l.4B 2.12 1.96 Midday +.0 2.08 4.69 4.03 3.4t Station 3 2.46 3.20 Afte¡noon +.35 2.25 3.2+ 2.65 2.08 20/9/65 1.35 2.64 3.22 3.36 tt / t0/65 0.86 2.+9 3.59 3.33 S/ 1I/65 Morning 5.25 8.05 6.04 5.22 2'80 t0/65 Midday 4.0 11.30 13.14 10'32 7.80 24/ Station 1 4.00 +.29 4.62 +.62 (24tu) Afternoon 5.30 13.33 11.67 7 +.33 | '86 Station 2 3.97 26/lI/65 Morning 5.65 1l.B 1l.B 10.9 5.25 4/11/65 Midday 4.0 7.8 17.5 12.6 t2.20 Station 1 5.3 1 5.15 5.25 4.44 Afternoon s.65 13.7 14.0 12.5 5.95 Station 3 5.82 5.83 18/tt/65 Mornins: Sunrise to 2 hours before middav' Station I 263 8.90 7,32 6.53 -\fiddavj 2 hours before midday to 2 bours afte¡ 11.80 .{fternoorr: 2 hours after midday to sunset. Station 3 9.53

79 TABLE 30: Phytoplankton productivity in Lake Mahinerangi (mg of carbon,/m3.hour) measured by the L and DB method.

Date 0m 0.5 m 1m 15n 2m 4m 6m 2l/11/63 r.7 5 5.69 +.82 t.97 0.8 t gross * 3.5 0 2.63 * *t net 5/ 12/63 2.79 6,01 7.08 7.08 4.50 gross + 2.08 2.t5 2.r5 * net t9/ 12/63 5.2 0 5.62 4.t6 2.50 t.25 gross 3.r+ 3.5+ 208 0.+2 * * net r6/r/648 2.09 5.00 4.59 3.13 0.63 gross * 2.29 2.07 0.61 net 29/r/6+ 11.1 1 1.6 9.84 0.7 t gross 7.05 7.+9 5.7 7 * *t net t3/2/645 9.2 8.97 6.67 1.38 1.61 gross 3.68 3.45 1. 15 * net t9/3/645 4.3 17.5 16.9 6.0 109 0.55 gross * 12.3 tt.7 0.8 * net 9/+/6+ 5.28 10.9 * 9.75 6.96 2.5t 084 gross 2.7 B t.67 * + net 23/4/64 5.78 12.5 10.0 6.38 2.7 I 1.0 t gross 2.r3 B.B1 6.40 2.73 *+ *l net 7 /5/64 5.32 13.I 12.+ 6.7 4 gross 4.26 12.0 11.4 5.68 net rB/6/6+ 0.40 2.79 2.39 0.80 gross * * * net

22/7 /64 3.8+ 5.34 384 0.35 T gross 2.r 3.5 21 + *t net 27 /8/64 1.5 0 5.4r gross * 3.30 net

TABLB 31: Phytoplankton productivity i¡ r,ake Mahinerangi (mg of carbon/m3.hour) measured by the 14Q method (not corrected to l sunrise-sunset experimental period).

Date 0m 0.5m 1m 2m 4m 6m Date 0 m 05m I m 2m 4m 6m 24/9/64 0.22 0.75 0.81 0.4+ 0.23 0.12t 26/B/65 21/ t0/64 0.49 1.06 1.15 0.74 0.12 0 04t Station 1 0.09 0.95 t.20 1 .33 o.9 l 0.6 21 tt/ 11 /64 0.71 1.3t 1.36 d.91 0.53 0.14t Station 2 . . 0.54 0.5+ t0/ 12/ 6+ 0.48 2.78 2.68 2.4+ L04 0.47t B/9/65 25/t2/6+ 0.78 4.84 4.80 q.03 1.14t Morning 0.52 0.75 0.7 9 0.64 2.3s Midday 0.10 0.58 0.69 0.BB 0.62i 0.44y 27 1/6s / 2.19 5.52 5.18 3..23 0.7 2 0.15 i Afternoon 0.19 0.43 0.66 0.84 to/2/65 0.54 6.00 6.90 4.95 0.7 5 0.13 t 23/9/65 0.32 1.08 0.87 0.91 0.32 0.0b 4/3/6s 0.98 2.t6 2.24 1.62 0.12 0.0 t 13/10/65 24/3/65 2.46 4,68 3.40 1.96 0.32 0.08t Station 1 0.29 2.75 3.03 3.13 1.98 1.1 t 7 /4/6s Station 2 . . 1.59 1.64 Station 1 233 2t7 t52 0.76 0.1 1 0.0 t 29/ 10/65 Station 2 106 Station 1 0.28 2.3+ 2.Bt 3.71 2.73 2.0 I t2/5/6s Station + . . l.9B 2.04 Station 1 0.70 2.84 3.00 283 o14 0.07t rt/tl/65 Station 3 2.76 Station 1 l.B6 3.03 T 7B 0.35 005 26/5/65 0.89 2.21 2.41 2t5 061 0.18t Station 4 . . 5.98 5.48 20/6/65 23/ 12/65 Station I . . 5.05 Station 1 0.BB 2.21 2.04 1.68 0.35 0.05 3.26 Station 3 . . 7.36 7 .60 Station 2 0,52 Statiox 6 3.93 4.50 7 /7 1.7 2 /6s 0.31 1.62 l.+3 0.35 0.06 Station 7 . . 4.36 6.19 22/7 /65 0.1B 0.94 t.2B 1.40 0.60 0.26t 6/ r/66 9/B/65 Station I 8.02 Station I 0.13 083 1.58 156 t42 04t Station 3 . . +.83 4.90 Station 3 . 1.64 1 67 Station 5 4.5 0 5.20

80 APPENDIX IIB: OXYGEN CONCENTRATIONS

Subsurface concentrations are reported only when they differed from those at the surface.

TABLE 32: Oxygen concentrations in Tomahawk I"agoon at sunrise.

Approximate APProximate Date Temperature Oxygen saturation Date Temperature Oxygen saturation ("c) (ms/t) (%) ("c) G"s/t) (%) t8/7 /631 6.2 I 1.15 93 16/ t2/63 13.4 B.B4 88 2B/7 /63Ë ,1 11.30 82 23/ t2/63Ë 10.6 9.50 BB t2/B/63 6.3 10.63 88 20/ | /6+S 14.0 9.82 99 20/B/63 6.3 10.91 89 27 / r /6+S 18.8 7.78 86 2/9/63 8.6 rt.43 101 6/2/6+S 18.6 2.lr 23 s/s/63s 8.0 10.21 89 24/2/6+ t+.4 8.96 90 16/9/63 9.0 9.87 84 30/3/645 13.6 8.32 83 23/9/63 B.B 9.76 87 20/+/64 11.2 7.98 75 30/9/63 10.6 9.35 86 tt/5/64 B6 7.88 7 0 7/10/63 13.0 7.79 77 B/6/645 4.6 11.16 89 83 t4/ t0/63 rr.2 7 ,TB 68 1s/6/64 0m 0.4 tr.72 84 2r / t0/63 13.8 7.87 78 05m 2.+ 11.60 28/ 10/63 14.0 t0.27 103 6/7 /6+ 5.2 9.17 74 4/tr/63 12.8 7.37 72 20/B/64 +.2 B.7B 70 tt/rr/63s B.B 9.26 83 2/1/65 1m +5 13.30 106 18/ tr /63 10I 8.59 B0 I m, among 25/lI/63 0 m 15 6 8.49 8B rveeds +.2 12.50 100 0.75 m

TABLE 33: Oxygen concentratio¡x in Tomaharvk Lagoon TABLE 35: Oxygen concentrations in Lake Waiporr at noon. at sunrise. Approxima*-c Approximate Date Temp"erature Oxygen saturatlon Date Temperature Oxygen saturatlon (c) (ms/l) (%) ( c, (ms/l) (%)

9/ t2/63 t7 .+ 8.18 89 28/ tt/63 10.8 9.5 0 B9 6/r/64 17.6 rt.62 125 9/ | /64 1+.6 8.96 91 r0/r/64 l4.B 10.26 104 23/t/6+ 13.4 9.45 94 t3/l/6+ 13.+ t2.20 120 7 /2/64 15.0 9.14 94 84 6/2/64 1 7.6 3.85 +l 20/2/64 t4.6 8.25 90 rl /2/ 64 22.0 7 ,59 89 5/3/6+ t4.+ 8.92 B9 17 /2/64 2 0.0 t+.52 162 2r /3/6+ 13.0 9,09 (minimal estimate) 2/+/64Ë t2.6 9,7 | 95 tB/2/6+ 18.6 I 1.36 12+ r6/4/645 t2.6 10.10 9B 9/3/645 15.5 10.76 111 16/5/64 6.6 10.71 91 16/3/648 t2.4 8.90 B6 2/7 /6+E +.0 12,35 98 23/3/649 12.0 9.37 90 r3 /B/6+ +.6 I 1.63 9+ 6/4/6+g 10.5 1 1.80 109 t4/4/649 13.0 9.76 96 +/5/6+E 8.4 8.59 76 1r/5/6+ 9.0 9.01 B 1 TABLE 36: Oxygen concentrations in Lake l{ahinerangi 22/5/64Ë 4.6 9.79 79 at sunrise. 22/6/645 +.0 I 1.76 93 29/6/6+ 6.0 9.3+ 78 Approximate 6/7 /6+ 7.0 9.85 84 Date Temp.eraturc Oxygen saturatton t 1 /B/6+ 8.0 10.48 92 ( c/ (^s/t) (%) 2t/ 1r/63 11.0 10.15 95 5 / 12/63 l+.2 9.5 0 96 Tomahawk Lagoon 19/t2/63 t+.2 8.96 90 TABLE 34: Oxygen concentrations in 96 at 10'30 a'm. t6/r /648 r+.0 9.62 29/t/6+ 13.8 8.98 90 Approximate t3/2/645 20.2 9.06 02 Date Temp.erature Oxygen saturatlon 19/3/645 12.0 9.24 B9 (cJ (msll) (%) 9/+/64 t2.0 10. 10 97 23/+/64 10.2 10.1 2 93 t4/9/6+ 10.2 9.42 87 7 /5/64 8.4 1 0.38 92 2/12/64 13,0 9.08 89 tB/6/64 3.6 12.07 97 8/3/65 15.0 10.28 105 22/7 /6+ 3.4 12.12 9+ 26/7 /6s 5.2 t2 07 98 27 /8/64 3.6 12.28 96

81 APPENDIX IIC: SURFACE \,VATER TEMPERATURES IN LAKE MAHINERANGI, LAKE WAIPORI, AND TOMAHAWI( LAGOON

Where there were detectable changes in temperature with depth () 1'c) this is recorded in the foot- notes to the tables.

TABLE 37: Surface temperatures in Lake Mahinerangi, TABLE 39: Surface temperatures in Tomahawk Lagoon, November 1963-August 1964. September 1964-January 1966.

Date Surface temperature Date Surface temperatru'e (c) (c,

14/9/64 10.2 2r/ rt/63 1 1.0 2t /9/6+ B.B ( 10.45 a.m.) 5/12/63 1+.2 5/ r0/6+ 12.0 t9/t2/63 t+.2 12/10/64 13.9 16/1/64 t+.0 19/ t0/6+ 14.6 26/10/64 10.5 29/1/64 t 3.B 9/ 11 /6+ t2.5 t3/2/64 20.2 2/ t2/64 13.0 19/3/64 t2.0 14/ t2/64 20.4 9/4/64 12.0 28/12/64 19.6 23/4/64 l 0.2 t8/ r/65 22.0 ( 10.45 a.m.) 25/r/65 +.6 7 /5/64 8.4 r/2/65 7.6 1B/6/64 3.6 B/2/65 7.o 22/7 /64 3.5 22/2/65 4.7 8/3/65 (10.45 a.m.) 27 /8/64 3.6 5.0 t5/3/65 6.2 22/3/65 6.0 No subsurface measufements were made on 29 lantaty,9 April, 5/4/65 2.3 7 lrlay, or 27 Augusl 1964. On 13 February 1964 the temperature 12/4/65 2.s declined with depth to 17.6"c tt 6m. Su¡face tempe¡atures for tha 26/4/65 0.5 ( 10.45 a.m. period ) September 1964-lanuary 1966 have been presented h frg. 24. 6/5/65 8.0 There were no significant cbanges period. witb depth during this t7 /s/65 7.5 3t/5/65 7.0 7 /6/65 5.0 15 /6/65 +.5 28/6/65 3.0 5/7 /65 3.5 t2/7 /65 3.4 17 /7 /6s 2.5 TABLE 3B: Surface temperatures Lake in Waipori, t9/7 /6s 4.2 November 1963-August 1964. 26/7 /6s 5.2 2/B/65 5.0 Date Surface temperature rt /8/ 65 6.1 (c/ 23/B/65 6.2 30/8/65 8.4 28/11/63 t3.2 16/9/65 I 1.0 12/12/63 16.3 28/9/65 7.5 15.2 9/1/64 4/r0/65 9.2 23/1/6+ 15.5 19/ 10/65 10.0 7 /2/64 17.5 26/ to/65 1 1.5 5/3/6+ t5.2 3/tr/65 12.5 (sunrise 21/3/64 13.0 only) B/tt/65 12.5 2/4/6+ t2.B 22/ tt /65 12.8 t6/4/64 13 0 26/ll/65 16.0 t6/5/6+ 6.8 13/12/65 21.5 2/7 +.6 /64 3/ | /66 t4.2 t3/7 /6+ 5.0 Surface temperatures in Tomahawk Lagoon from July 1963 to August Surface temperatures in Lake Waipori for the period September 1964 1964 are shown in tables 32 and 33, in Appendix IIB. These were November 1965 have been presented in ñg. 24. recorded at the beginning of the experiments.

82 TABLE 40: Diurnal variations in temperature in Tomahawk Lagoon.

I emperature ( c,l Temperature ('c) Date Time 0m 0.5m Date Time 0m 0.5 m

12/7 /6s 8.18 a.m. 0.5 3.0 4/ 10/65 10.45 a.m. 3.0 3.5 ( cont. ) 2.28 p.m. 9.5 2.45 p.m 3.7 3.9 6.50 p.m. 9.5 5.18 p.m. 3.5 B/ 1r /65 5.04 a.m. 12.5 10.21 a.m. 30/B/65 7.22 a.m. 8.0 2.21 p.m. 10.40 a.m. 7.38 p.m. 125 2.40p.m. 8.6 6.08 p.m. 26/ lr/65 4.45 a.m. 16 0 10.25 a.m 160 +/ r0/65 6.06 a.m. B5 2.25 p.m. 10.28 a.m. BB 8.04 p.m, 162

APPENDIX IID: SECCHI DISC TRANSPARBNCIBS IN LAKE MAHINERANGI

TABLE 41: Secchi disc transparencies in Lake Mahinerangi'

Date Transparency Date Transparency (^) (m)

2t/ rt/63 1.5 10/2/65 t,75 t.7 5 5 / 12/63 2.75 +/3/65 t9/12/63 2.7 5 24/3/65 2.2 16/1/64 1.5 7 /4/65 2.3 2.0 29/r/6+ 2.0 t2/5/65 to t3/2/6+ 2.1 26/5/65 t9/3/64 1.5 20/6/6s 2.6 9/+/6+ 2.25 7 /7 /65 qJ 23/4/64 2.0 22/7 /65 18/6/6+ 2.r 9/8/65 2.6 22/7 /6+ 2.3 26/8/65 J..t 24/9/64 2.0 23/9/65 2.3 2r / t0/ 6+ 1.9 13/ l0/65 rt / t1 /64 t.75 29/t0/65 4.0 r0/t2/6+ 1.7 5 tl/tl/65 3.0 25/12/64 t.7 5 23/ t2/65 2.9 3.2 27 /r/65 t.7 5 6/r/66

APPBNDIX IIE: DATA USBD IN MULTIPLE REGRESSION ANALYSES

TABLE 422 Data used in multiple regression analyses of the relation between P^* in Lake Mahinerangi and temperature' - daí length, and water level.

Water level TemPera- D^Y Water level Tempera- Day P",., at dam ture length Date P^u. at dam ture length (mg C,/m3.hr) face (ft) ("c) (h") (mg C/m3.hr) face (ft) ("c) (hr) 91.7 9.2 7.+ 2.1 22/7 /65 0.98 2.0 24/9/6+ 0.56 77.3 9r.7 9.9 7+.3 11.1 5.t 9/8/65 1.10 2.6 2l/10/6+ 0.80 91.8 r0.7 0.95 7+.4 10.5 4.7 26/8/65 0.93 3.5 t1/tt/6+ 0.62 92.3 11.35 1.90 76.9 14.+ 5.65 8/9/65 +.6 t0/t2/64 0.75 93.3 7.0 r2.r5 25/12/64 3.52 tB.6 5.75 23/9/65 t3/ 10/65 2.t9 93.6 7 .2 t3.2 27 /r/6s 3.86 81.4 16.6 4.85 16.8 4.55 29/10/65 2.60 94.8 11.5 t4't 10/2/65 4.83 B 1.8 96.2 t2.0 1+.7 +/3/65 1.57 8r.+ 13.0 3.1 tr/tt/65 2.12 23 / 12/65 3.5+ 99.4 15.8 15.75 2+/3/65 3.28 B4.B t+.5 2.1 15.55 6/ 1 /66 s.61 102.3 16.0 7 /4/65 1,63 B4.B t2.4 L25 BB.5 6.5 9.35 To meet the tequirement t2/5/65 2.r0 coded, Temperature was 26/5/6s 1.69 89.0 5.5 9.05 Day length was multipli 20/6/65 1.54 91 .5 3.5 8.65 level was multinlied t¡Y 2.8 B.B been taken,6.8 was sub 7 /7 /65 1.13 92.0

83 TABLE 43: Temperatures and P-"* values used i¡r. testil¡g, lor-Lakg Waipori, the multiple regression equation which had been derived for Lrke Mahinerangi,

Temperature difrerence Waipori Mahinerangi P-* Waipori (Waipori minus Date P-"= Temperature Date D Temperature Mahinerangi) (mg C,/m3.hr) ('c) (mg C,/m3.hr) ( "c) P^"* Mahinerangi ('c)

17 /9/64 059 7.6 24/9/6+ 0.57 7.+ 1.0+ 0.2 t+/ t0/6+ 277 4.5 2r/r0/6+ 080 11.1 3.46 3.4 28/10/64 2.61 1 1.6 2r / r0/ 6+ 0.80 11 1 3.26 0.5 t9/ 1t/6+ 3.36 16.8 rt/ tt/6+ 0.96 10.5 3.5 0 6.3 7 /12/6+ 9.24 16.4 r0/ 12/ 61 1.90 r4.+ 4.86 2.0 23/12/64 4.33 180 25/ 12/6+ 3.52 18.6 r.23 20/l/65 B.6B 2+.0 27 / 1/65 3. 86 16.6 2.25 -0.67.4 4/2/65 7.21 17 .6 t0,/2/65 4.83 16.8 1.49 0.8 t7 /2/6s 4.05 16.3 10/2/65 4.83 16.8 0.84 r0/3/65 3.70 t4.0 +/3/65 t.57 13.0 2.36 -0.51.0 14/5/6s 2.r6 6.2 12/5/65 2.to 65 I .03 2/6/65 2.43 7.5 26/5/65 1.69 5.5 t.44 -0.32.0 t6/6/65 2.65 +.5 20/6/65 15+ 35 t.7 2 1.0 tt/t0/6s 2.51 I 1.0 13/10/65 2.19 7.2 t.15 3,8 lB/11/65 6.23 15.5 11/tt/65 2.12 l2 0 2.94 3.5

APPBNDIX IIF: DATA FROM ANALYSES TO DETERMINB CONCBNTRATIoNS oF PTIYTOPLANKTON PIGMENTS

TABLE 44: Data from analyses to determine concentrations of ph¡oplankton pigments in Tomahawk Lagoon.

Sample volume Extraction volume Optlg{- density at rvavelength (m¡r) of Date (ml) (ml) 750 665 6+s 630" ' 5iô With l-cm cells 5/ 10/64 179 9.9 0.003 0.026 0.014 0.017 12/10/64 160 9.9 0 005 0.023 0.016 0.018 19/ ro/6+ 307 5.4 0.003 0.070 0.041 0.048 26/t0/64 (a) 269 5.2 0.008 0.069 0.043 0.047 (b) 262 4.9 0.007 0.061 0.035 0.039 9/ 1t/ 64 200 6.+ 0.012 0.107 0.063 0.068 2/12/6+ 289 5.55 0.007 0.063 0.037 0.0+l I+/12/6+ (a) 275 4.65 0.005 0.049 0.027 0.031 (b) 275 7.4 0.003 0.032 0.018 0.020 28/12/6+ 225 5.3 0.023 0 060 0.041 0.045 t8/1/65 4t0 6.0 0.008 0.101 0.050 0.056 25/r/65 400 0.002 0.076 0.064 0.064 1.368 1.960 r/2/65 400 6.5 0 001 0.059 0.043 0.043 0.885 1.294 B/2/6s 350 6.4 0.001 0.043 0.031 0.033 0.770 1.131 With 4-cm cells 22/2/65 150 9.3 0 059 0.229 0.060 0.070 2.40 3.43 B/3/6s 200 9.15 0.o+2 0.394 0.105 0.108 1.785 2.08 t5/3/65 200 9.4 0 029 0.35+ O.O74 0.075 1.08 1.74 22/3/65 200 9.4 0.035 0.222 0.063 0.061 0.489 0.831 5/4/65 500 9.3 0 035 0.157 0.065 0.062 0.176 0.398 12/4/65 450 10.0 0.030 0.114 0.0+4 0.043 0.117 0.231 6/s/65 600 9.5 0 023 0.134 0.043 0.0+2 0.099 0.218 17 /5/65 700 0.2 0.023 0.059 0.025 0.025 0.1 13 0.188 31 /5/6s 750 0.0 0 036 0.063 0.041 0.040 0.084 0.130 7 /6/65 900 0.0 0.046 0.087 0.054 0.054 0.122 0.195 15/6/65 450 0.0 0.051 0.068 0,056 0.059 0.106 0.142 28/6/65 350 0.0 0 014 0.062 0.024 0.021 0.060 0.126 5/7 /65 350 0.0 0.019 0 264 0.092 0.066 0.062 0.285 26/7/65 (a) 3Ofl 0.0 0.01 1 0.052 0.019 0.017 0.058 0.125 (b) 300 0.0 0.014 0 052 0.024 0.02 1 0.057 0.124 (c) 300 0.0 0.010 0.053 0.020 0.016 0.050 0.119 (d) 300 0.0 0.011 0.053 0.019 0.016 0.054 0.123 (e) 300 0.0 0.019 0.060 0.028 0.025 0.070 0.141 (f) 300 0.0 0.011 0.050 0.020 0.017 0.054 0.118 t1 /8/65 500 0.0 0.01 I 0.036 0.026 0.017 0.037 0.094

84 TABLE 45: Data from analyses to determine concentrations of phytoplankton pigments in Lake Waipori.

Sample- volume Extraction volume Optical density at wavelength (+ry) of Date (ml) (*l) 750 66s 6+5 630 510

With 1-cm cells r+/ r0/6+ 3t8 10.0 0.000 0.009 0.003 0.00s ls/11/64 (a) 350 +.8 0.008 0.017 0.013 0 013 (b) 300 4.9 0.005 0.016 0,013 0.014 6/12/64 (a) 400 5.4 0.000 0.011 0.008 0.009 (b) 400 5.0 0.002 0.015 0.010 0.01 1

With 4-cm cells t7 /2/65 350 9.4 0.012 0.070 0.018 0.01ri t0/3/65 300 9.6 0.015 0.060 0 027 0.027 0.057 0.130 | /+/65 s50 9.6 0.030 0.094 0.051 0.052 22/+/65 500 10.0 0.022 0.041 0.027 0.027 o.'oog o.'oriz 2r/5/65 600 9.5 0.013 0.071 0.020 0.020 0.055 0.1+2 2/6/65 445 10.0 0.037 0.087 0.049 0.051 0.11r 0.193 16/6/65 300 10.0 0.033 0.082 0.043 0.044 0.095 0.166

TABLE 46: Data from analyses to determine concentrations of phytoplankton pigments in Lake Mahinerangi.

Sample volurne Extraction volume Optical dcnsity at wavelength (m¡¡) of Date (ml) (ml) 750 665 645 630 510 480

With l-cm cells 2t / t0/ 64 566 6.4 0 002 0.017 0.012 0.013 10/12/64 (a) 300 5,15 0.005 0.012 0.009 0.010 (b) 300 5.3 0.003 0.009 0.007 0.008 28/ t2/6+ 225 5.3 0 023 0.060 0 04r 0.045 lVith 4-cm cells 10/2/65 300 9.4 0 033 0.147 0.042 0.046 0.136 0.348 24/3/65 400 9.35 0.025 0.187 0.053 0.061 o.t29 0.348 7 /+/65 500 9.0 0.006 0.138 0.030 0.033 0.104 0.27 4 12/5/6s 400 9.7 0.017 0.054 0.021 0.021 0.059 0.1 1 1 26/5/65 350 10.0 0 023 0.052 0.028 0.028 0.054 0.096 20/6/65 600 10.0 0.029 0,130 0 045 0.045 0.102 0.235 0.27 3 7 /7 /65 500 10.0 0.043 0.150 0.060 0.063 0.136 9/B/65 300 10.0 0.017 0.041 0.032 0.023 0.047 0 099 26/B/65 300 10.0 0 01 1 0.036 0.026 0.017 0 037 0.094

oa ò-ì INDEX

Aerial topdressing, 40, 41. Distillation-absorption method, ? 3 -7 4. Light and dark bottle oxygen produc- Algal blooms, 25-26, 37. Drainage water, 13, 29, 30, 33, 34, tion metlod, 15, 18, 19, 21,22,31, Algal species composition, 25-26, +5, 53,63. 35-36, 37, 38, +5, 48, 49, 55, 59, 49. Dunedin Airport meteorological station, 65, 78, 79, 80. Alkalinity, 16, 28, 29, 30, 32, 33, 3+, 14. Light intensity, 19, 20, 37, 38, 43, 4+, 39, 40-+1,64. Dunedin City Corporation Electricity 49, 50, 51, 52, 53, 54,58, 61, 62, Allochthonous material, 43, 48, 50, 60. Department, 11, 62. 63, 65. Ammonia, toxicity of, 41. Dunedin, city of, 10, 19. Light penetraion, 37. Anøbaena, 25, 27 , 31, 37 , 38, 44, 64. Duplin River estuary, 47, Linsley Pond, 61, 63. Anabaena fl.os-aquae, 25, 42. Little Crooked Lake, 46. Anacharis, 63. Lunzer Untersee, 47. Anacharis canadensis, 12, 64. Esrom 54, 46. Anacystis, 25. Euglena, 26. Anacystis incerta, 25. Euglenineae, 26. Macrophytes, 9, 78,45, 47, 49, 54, 64. Ankistrodesmus, 25. Exuuiella, 47. Macrophytes and phytoplankton, inter- Ankistrodesmus spp., 25, 26. relations between, 37-44. Annual production, 45-48. Magnesium, 16, 29, 30, 40, 4I, 43, Arthrodesmus, 26. Flint, E. A.,25,26. 49, 64. Asterionella, 26, 61. raC and L and DB estimates, relation Marion Lake, 61. Asterionella I ormosa, 62. between, 35-36. Maungatua (Mt), 13. Asteroeoccus, 26. 1aC assimilated in photosynthesis, cal- Meggat Burn, 13. Ayyangulam (temple pond), 46. culation of, 74-75. Methods, l5-21, 65. 1aC method, standardisation of, 7 5-7 6. Methods, evaluation of, 72-77. laC sampling method, 15, 16, 17-18, Methods for measuring p}J, 72-73. Bacillariophyceae, 26 19-21, 37, 35-36, 37, 38, 41, 45, Methods to determine carbon dioxide 43. Black swans, 49, 50, 51, 52,55, 59, 65, 79, 80. concentrations , 7 3-7 +. Fures4, 46. Molybdenum, 49. Musselburgh meteorological station, Calcium, 16, 29, 30, 40, 41, 43, +9, 14. 6+. Gonium, 26. Myrioþhyllum elatinoídes, 37, 44. Calcium carbonate, calculation of Gonyøulax, 47. Myxophyceae, 43, 64. saturation values for, 76-77. Goose Lake, 46. Carbon, 10, 11, 16, lB,41,74. Gymnodinium, 25, 47. Carbon dioxide, 16, lB, 38, 41, 55, Gymnodinium limitatum, 25. Nardoo Stream, 33. 6+, 65,73-74. Gymnodiniutn sp., 25. Neþhrocytium, 26. Carotenoid pigments, 16, 57, 58. New Haven Hatbor, 47. Cassie, R. M., 51. Nitrate, 43,49,63,64. Chemical conditions, 27-30. Hardness, total, 16, 28, 29, 30, 32, Nitrogen, 10, 18, 29, 43, 49, 64. Chemical methods, 15-17. 33,3+. Northwest Stream, 33, Chlorella, 26, 65. Nutrient fertilisation experiments, 21. Chloride, 16, 30, 33, 34, 39-40, +1, ¿-() i ¿- Chlorophyceae, 26. Indices of phytoplankton productivity, Oocystis,26. Chlorophyll, 76, 27, 38, 39, 4+, 48, 55-60. Oocystis sp., 25, 26. 55-57, 58, 59, 61. Ionic solutes, 28-30, 40. Otago district, 9. Chodatella, 26. Iron, 49. Otago lakes compared with lakes in Chrysophyceae, 26. other countries, 45-47. Cladocera, 64. Otago Peninsula, 10. Clear Lake, 46. I(ingston Harbour, 47. Oxygen, 16, 18, 19, 27-28, 35, 36, Climate, 14. Kirchneriella, 26. 48, 55,65, 81. Cobalt, 49. Oxygen, dissolved, estimation of, 16. Coelastrurn sp., 25, C oelos þ haerium sp., 25. Lake Erken, 31, 46. Contour Channel, 13, 29, 33, 63. Lake George, 46. Pediast¡um tetras,26. Copepoda, 64. Lake Gervilon, 46. pH, 16, 29, 30, 32, 33, 34, 35, 38, 39, Cosntariurn,26. 40-47, 42, 43, 63, 64,72-73. Cosnocladiurn, 26. pH-alkalinity method, 16, 17, 73-74. Crooked Lake, 46. Phosphate, 15, 16, 28, 32, 40, +l-43, Crustacea, 64. +9,55,63, 64. Cryþtomonas, 26. Phosphorus, 28, 41, 42, 49, 50. Cryptophyceae, 26. Photosynthesis, 16, lB, 35, 37, 38, 41, Cyclotella mene ghiniana, 25. 43, sp., 45,48,50, 52, 55, 56,62,74-75. Cyclotella 25. Lake Peters, 47. Physical conditions, 27-30. Cyclotellø stelligera, 25. Lake Schrader, 47, Physical methods, 15-17. Cygnus atratus, 43. Lake Victoria, 46. Phytoplankton and macrophytes, inter- Lake Waihola, 12. relations between, 37 -44. Lake Waipori, 9, 12-13, l,l, 15, 16, Phytoplankton pigments, data from Daily production, calculation of, 19-21. 17, tB, 19, 23, 2+, 25-26, 27, 28, analyses to determine concentrations Day length, 14, 19, 20, 45, 49, 50, 51, 29, 30, 33-3+, 36, 4.5-+8, 52, 53-54., of, 84-85. 52,53,61, 62, 63, 65, 83. 55, 56, 57, 58,63, 65, 72, 73,74, Phytoplankton productivity, relation Detritus, organic, 48. 79, 81, 82, 84, 85. of, to environmental factors, 49-54. Dictyosþhaerium, 26. Lake Windermere, 38, 42. Pinnularía, 26. Dinobryon, 26. Lakes of Swedish Lapland,, 47. Plankton blooms, 41. Dinoflagellate blooms, 25, 38, 44, 47, Lammerlaw Stream, 33. Potamogeton loliosus, 64. 57. Lemna minor, 33. Potassium, 43.

86 Production and respiration, 47'48. Secchi disc transparency, 15' 27' 37' Tomaharvk Lagoon ImProvement Productivity data, 78-80. 38, 39, 57-60, 7+, 83. Prowse, G. 4., 25. Seston, 16, 4+,57. Pseudokeþhyrion, 26. Silicon, 49. S4llerod Sd, 46. Spirogyra, 64. Radiochemical Centre, 17. Stondvlosium, 26. t4, 40, 41, +3. S'taurastrum rpp., 26. lus fluitans,37, 44. Staurodesmus, 26, 83, 84. lagoon in, 46. Topdressing, aeial, 4O, 4I. ter" .blooms,. +4, 47. Sudan, variations in PhYtoPlankton Sudan, reservoir in, 46' Tolal hardness, 16, 28, 29,30,32,33' productiviry, 31-34. Sulphate, 49. J ti. Reipiration and productiory 47-48. Sunshine hours, 14. Trachelomonas, 26, Results, 78-85. Surface water temperature, 82-83. Tystrup Sø, 46. Rhizoclonium, 64. Sylvan Lake, 46. Rotifera, 64. Synedra, 26. Swans, black,43. U.S.S.R. lakes, 46.

Sa.mpling depths, 15. Sampling errors, 31-34, 45. Waipori River, 11, 12, 13, 32, 33, 63. 53, Sampling methods, 15. Tabellaria, 26. Watèr level, +3, 48, 49, 50, 52, 83. Sampling stations, 10, 1 1, 12, 15, Taieri Plain, 12, 73, 30, 34' 53. 61, 62, 63, J I-JJ. Taieri River. 12. Seened¿smus quadricauda, 25, 41, Temperature, 14, 16, 27,42,49, 50, Seasonal distribution of phytoplankton 51, 52, 53, 61, 62, 63, 81, 82-83, Zinc, 49. productivity, 22. 84, Zooplankton, 63,64.

87 Bulletins of the Fisheries Research Division

No, l. The New Zealand Cetacea. By D. E. Gaskin. Published in 1968. 92 pp. 2. Galaxias maculatus (Jenyns), the New Zealand whitebait. By R. M. McDowall. Published in 1968. 84 pp. 3. Phytoplankton productivity in Tomahawk Lagoon, Lake Waipori, and Lake Mahinerangi. By S. F. Mitchell. Published in 1977. 87 pp. 4. Some aspeets of the bionomics of ûsh in a brown trout nursery stream. By C. L. Hopkins. Published in 1970. 38 pp.

Prinfed by "The Eveninq Post", Wellinqton, by aufhority A, R. Shearer, Government Prinfer.