Plankton Disturbance at Suape Estuarine Area

Plankton disturbance at Suape estuarine area -

Pernambuco - Brazil after a port complex implantation

S. Neumann-Leitao, M. L. Koening, S. J. Macedo,

C. Medeiros, K. Muniz and F. A. N. Feitosa Department of Oceanography of the Federal University of Pernambuco, Campus Universitdrio, 50.679-901, Recife, Pernambuco, Brazil

Abstract

The plankton structure was investigated at the estuary of the River Ipojuca after 1 0 years implantation of a Port Complex. Plankton was sampled in one fixed station. Concurrent hydrological, climatological and chlorophyll a data were taken. The course of the river alteration resulted into an estuary that tends to evolves from a classical towards a coastal lagoon type. Chlorophyll a presented low values for an estuarine mangrove area. Plankton high diversity (> 3.0 bits.ind"*) can be explained by the spatial heterogeneity, although a general biodiversity decrease was registered after port implantation. Phytoplankton presented 98 taxa outranking diatoms (72 species). Zooplankton presented 63 taxa outranking rotifers (29 species) and copepods (21 species). Less than 5% of these taxa were very frequent. Irregular fluctuations in plankton densities were observed with a sharp abundance decrease after port implantation. The community was dominated by marine eurihaline species with a high proportion of littoral taxa. Meroplanktonic larval recruitment was reduced by landing and dredging. The anthropic impacts affected the system balance.

1 Introduction

A Port Complex was implanted in the south coast of Pernambuco State, Noth eastern Brazil in 1979/1980 as a solution to the State economy collapse. Two years before (1977/1978), an Ecological Study Program was introduced to

Transactions on Ecology and the Environment vol 27 © 1999 WIT Press, www.witpress.com, ISSN 1743-3541 48 Ecosystems and Sustainable Development obtain the general diagnosis of the area. These studies (Melo Filho\ Cavalcanti et al\ Eskinazi-Lega & Koening^, Paranagua^, Neumann-Leitao et a/7, and others) revealed a high productive balanced ecosystem and suggestions were made to minimize the impacts. After the Port implantation, ecological studies were made by the Department of Oceanography of the Federal University of Pernambuco, from

1886 to 1991; the present paper focalizes the reef area in 1990-1991 at the mouth of the River Ipojuca to assess some of the impacts and summarizes the seasonal and nyctemeral structure of the plankton dynamics.

2 Study area

The Suape coastal estuarine complex is located at 8°15' - 8°30' S and 34°55' - 35°05' W, about 40 km south of Recife City (Figure 1). Climate is warm- humid, pseudo-tropical (Koppen As') with mean annual temperature 24°C and rainfall 1500-2000 mm.yr"\ concentrated from March to August. Humidity is higher than 80%. Predominant winds are from the southeast. The former Atlantic plain forest has largely been replaced by sugar cane culture (Neumann- Leitao & Matsumura-Tundisi®). Before the port implantation four rivers (Massangana, Tatuoca, Ipojuca and

Merepe) converged to Suape Bay, itself an estuary partly isolated from the ocean by an extensive arenitic reefline. Today, converge into Suape Bay the rivers Massangana and Tatuoca. The Ipojuca and Merepe had their communication with the bay interrupted by intensive embankment to build the Port Complex. As a result of the weak communication with the sea, the reflow of these rivers flooded the surrounding fields causing damage to agriculture. The Government solution was a partial breakage of the reefline. In consequence a high amount of suspended material now pass through the reefline opening settling inside the Port, with a high cost dredging. In Suape area more than 600 hectares of mangrove have been destroyed (Neumann et al^).

3 Material and Methods

Climatologycal data were obtained from the Usina Salgado Meteorological Station, located 5 km southwest Suape Port. Samples were collected at 1 fixed station close to the reef, in a spring tide, during consecutive 24 h, each 1 hour interval (hydrology) and each 2 hours interval (plankton and clorophyll a), in August/90 (rainy season) and January/91 (dry season). Hydrological data were collected at surface and at 1m from the bottom with a Nansen bottle. Water temperature - reversion thermometer affixed to

Nansen bottle; salinity - Mohr-Knudsen method (Strickland & Parsons^); pH - Beckman Zeromatic II pHmeter; dissolved oxygen - Winkler method (Strickland & Parsons^); nutrients - (Strickland & Parsons^); water transparency - Secchi disc. For sampling the phytoplankton it was filtered 60 liters of water through a

PVC pipe 30 cm high and 10 cm diameter with a mesh size 45 urn fitted in one

end. For the zooplankton it was used the same methodology although the mesh size was 65 jj,m. After filtration the material of each sample was transferred to a proper flask and preserved in 4% formaldehyde-seawater solution. Phytoplankton analysis was made in an inverted microscope. Zooplankton entire samples were analysed in a Sedwick-Rafter chamber under Zeiss microscope. Chlorophyll a was collected with 1 liter Van Dorn bottle at surface and 0.1% of surface incident light intensity. Chlorophyll a was measured by

Micronal B280 Spectrophotometer according to Strickland & Parsons^. Species diversity was calculated by the Shannon^ index. Persons's product-moment correlation was calculated to measure the relationships between species of all samples after a matrix of log transformed abundances

(number of taxa per nf). A cluster analysis was performed using the Weighted Pair Group Method, Arithmetic Averages (WPGMA). The Principal Component Analyses was computed based in the matrix formed by planktonic taxa (> 35% occurrence), Chlorophyll a, Species Diversity and hydrological data. Standardization was performed to all data.

Statistical analyses were carried out using the Numerical Taxonomy and Multivariate Analyses System - NTSYS - ver. 1.30 (Metagraphics Software Corporation, California - USA, 1987).

-8"22'S

-8°23'S

ATLANTIC OCEAN - 8°24'S

1 35°W 34°57W

Figure 1 - River Ipojuca area, Suape, Pernambuco, Brazil *A - Sampling station

4 Results and Discussion

4.1 Abiotic dynamics

The average rainfall from 1970-1990 was minimum in October (51.40 mm) and maximum in July (396.30 mm). The total annual average was 1,814 mm and the rainy season occurring from March to August. The water temperature was not a limitant factor due the narrow range of values measured. A clear minimum (26.2°C) during rainy season (July/90) and a maximum (30.0 °C) in the dry season (January/91), reflected the tropical condition of Suape area. Salinity showed an irregular pattern. At the rainy season, the surface salinity decreased from 36.41%o (5:30 h) to 11.7%o (13:30 h), rising to 36.00%o at 16:30 h followed by a decrease to its minimum of 4.17%o at 1:30 h. The bottom salinity presented a similar pattern. At the dry season, the salinity continuously oscillated up and down, both surface and bottom, with maximum at 5:30 h (37.18%o - surface; 39.04%o - bottom) and minimum of 11.15%o at 3:30 h (surface) and 21:30 h (bottom). Vertical stratification was restricted to the rainy season when a complete flushing of the estuary by freshwater occurred during ebb and low tide. In 1990 and 1991 the salinity regime was polihaline, while in 1986 to 1987 it had a strong limnetic influence; and according to Cavalcanti et at' it was polihaline to limnetic before port implantation. Salinity fluctuations reflected a complex set of factors, namely the circulation in the estuary with the continuous discharge of the River Ipojuca partialy darned at its mouth. It is worth mentioning the change of the surface sediment distribution in the estuary that had high influence in the depth decrease and higher evaporation. Before the port implantation the sediment distribution in the estuary was predominantly determined by river action. The circulation was controlled by tidal movements and only a small contribution to estuarine sedimentation was made by marine sediments. After the reef partial opening the sediment was characterized by a fluvio-marine sand facies. Marine sediments that previously were transported to Suape Bay became traped at the estuary resulting in a sandfilling of the mouth area and the shifting of the main channel of the Ipojuca River (Neumann et a//). Surface and bottom dissolved oxygen saturation showed no clear trends, ranging from supersaturation to very low levels. Significant oxygen depletion was found during the ebb and low tide, mostly at dry season.

The pH was always above 7.5. Water transparency was high during high tide for both seasons. Reduced levels were registered at the rainy season at low tide, due intense fine clay resuspension. A strong sedimentation near the river mouth decreased the local depth. This sedimentation summed up to the river- ocean partial closure transformed the estuary into a lagoon (Neumann et al.^). Rates of nutrient suply (NO?, NO^ PC>4 and SidJ varied seasonally; rainfall brought pulses from terrestrial run-off. Nutrients levels indicated eutrophy. Chlorophyll a oscillated continuously with higher values at the 1% light depth. Low tide and rainy season showed higher values (maximum 7.86

Ecosystems and Sustainable Development 51 mg.m^). Chlorophyll a had strong correlation with nitrate and was considered low to a mangrove estuarine area (average of 3.07 mg.m"^ to the rainy season and 2.11 mg.m"^ to the dry season).

4.2 Plankton community analysis

Tables 1 and 2 present the phytoplankton biodiversity. It was identified 98 taxa outranking diatoms with 72 species. Phytoplankton was characterized by marine planktonic neritic, marine oceanic and marine littoral species. Freshwater species was not significant, mostly registered at rainy season. Five species were very frequent: Gyrosigma balticum, Oscillatoria princeps, Chaetoceros lorenzianus, Climacosphenia moniligera and Licmophora abbreviata. Phytoplankton density was higher at the dry season (minimum 262,000 cel.T* at

3:30 h and maximum of 1,789,000 cel.l^ at 15:30 h). Two diurnal cycles were observed a higher from 11:30 to 15:30 h and a smaller from 1:30 to 3:30 h. At the rainy season densities varied from 142,000 cell"* at 19:30 h to 740,000 cel.l" 'at 13:30 h (Figure 2).

High loads of suspended material, mainly at the rainy season, caused a decrease in phytoplankton reproduction. Phytoflagellate was abundant in the nanophytoplankton fraction. Phytoplankton biodiversity and ecology changed with the port implantation (Eskinazi-Leca & Koening^), predominating now epyphytic and benthic species; a decrease of about 70% in cells density was registered to this area. The 63 identified zooplankton taxa are listed in Tables 3 and 4. The list contains tycoplanktonics reflecting the shallowness of the estuarine area at the river mouth, tides turbulence and continuous dredging.

Table 1 - List of the phytoplankton taxa (except for CHRYSOPHYTA) recorded at the Ipojuca River Estuary in August/90 (rainy season) and January/91 (dry season).

CYANOPHYTA Ceratium massiliense (Gourret) Joigensen Men'smopedia tenuissima Lemmermann Ceratium pentagonum Gourret Oscillatoria limosa Agardh ex Gomont Ceratium teres Kofoid Oscillatoria princeps Vaucher ex Gomont Ceratium trichoceros (Ehrenberg) Kofoid Oscillatoria tetwis Agardh ex Gomont Cei-atam tiiposvwpulchettu m (Schroder) Lopez Oscillatoria willei Gardner Protoperidinium claiidicans (Paulsen) Oscillatoria sp Protoperidinium grande (Kofoid) Spindina major Kiitzing Protoperidinium venustrum (Matzenauer) Anabaena sp Protoperidinium sp CHLOROPHYTA EUGLENOPHYTA Euglena sp Pediastrum duplex Meyen PYRROPHYTA Pediastnim simplex (Meyen) Lemmermann Ceratiumjitiica (Ekenbag) Clapaitde & Lachman Scenedesmus quadiicauda (Turpin) Brebisson Ceratium fusus (Ehrenberg) Dujardin Closterium setaceum Ehrenberg Ceratium macroceros (Ehrenberg) VanhofFen Staui'astrum sp

Table 2- List of the CHRYSOPHYTA recorded at the Ipojuca River Estuary in

August/90 (rainy season) and January/91 (dry season). Dictyochafibida Ehrenberg Asterionellopsis glacialis (Castracane) Round Coscinodiscits centralis Ehrenberg Climacosphenia moniligera Ehrenberg Coscinodiscus oculusiridis Ehrenberg FragilariacapuciriaDcsmazieKS&, Kutzing Coscinodisciis sp Grammatophora hamulifera Kutzing

Cyclotella stylorum Brigjhtwell Grammatophora marina (Lyngjbye) Kutzing Melosira moniliformis (O. Muller) Agardh Grammatophora oceanica Ehrenberg Paralia sidcata (Ehrenberg) Cleve Licmophora abbreviata Agardh Thalassiosira leptopus (Grunow) Hasle & Fryx Podocystis adriatica Kutzing Actinoptychus spendens (Shadbolt) Ralfs Rhabdonema adriaticum Kutzing Giiinardiastolterfothii(P&gal\o) Hasle Rliabdonemapwictatum (Harvey & Bailey) Stodder Rhizosolenia imbricata Brightwell Striatella interrupta (Ehrenberg) Heiberg Rhizosolenia setigera Brightwell Synedrasp Bacteriaslrm delicatulum Cleve Tlialassionema nitzschioides Grunow Bacteriastrum hyalinum Lauder Thalassiothrixfrauenfeldii Grunow Chaetoceros cwvisetus Cleve Achnanthes brevipes Agardh

Chaetoceros decipiens Cleve Campyloneis grevillei (Wm. Smith) Grunow Qiaetoceros diversus Cleve Diploneis sp Chaetoceros laeve Leuduger- Fortmorel Gyrosigma balticum (Ehrenberg) Rabenhorst Chaetoceros lorenzianus Grunow Lyrella lyra (Ehrenberg) Karajeva Chaetoceros peruvianus Brightwell Mastogloiasplendida(GrQV\[\e) Grunow Chaetoceros sp Navicula Immerosa Brebisson Bellerochea malleus (Brightwell) Van Heurk Navicula sp Biddulphiapulchella Gray Pinnularia nobilis Ehrenberg Biddulphia tridens Ehrenberg Amplwra aj"enai"ia Donkin Cerataulus twgidus Ehrenberg Amphiprora alata (Ehrenberg) Kutzing Dityhim brightwelli (West) Grunow Bacillariapaxillifer Gmelin

Heliotheca thamesis Shrubsole Cylindivthecadostejium (Ehrenberg) Reiman&Lewis Hemiaulus niembranaceus Cleve Ni(zschialongissima(BrQb\sson) Grunow Hemiaulits sinensis Greville Nitzschiapungens var atlantica Cleve Isthmia enervis Ehrenberg Nitzschia scalaris (Ehrenberg) Wm. Smith Odontella awita (Lyngbye) Agardli Nitzschia sigma (Kutzing) Wm. Smith Triceratiumfavus iqwdrata Grunow Campylodiscus biangulatus Greville Triceratiumpentacrinus Ehrenberg Cainpylodiscus ctypeus Ehrenberg Terpsinoe miisica Ehrenberg Siirirellafastuosa Ehrenberg Hemidisais hardmardanus (Greville) Man Swirellafebigerii Lewis Astenonella notata Grunow Simrella sp

The zooplankton was essentially composed of typical marine estuarine species. The most diversified taxon was Rotifera (28 species and 2 varieties) followed by Copepoda (21 species) and Tintinnina (11 species). Most of the Rotifera were limnetic estuarine and had less than 1% of numerical abundance. Most abundant were Rotaria rotatoria, Rotaria sp, Platyias quadhcornis, Brachionus plicatilis and Filinia longiseta, all eutrophy indicators. Among the Copepoda it was distinguished a dominant group of marine euryhaline species: Paracalanus crassirostris, Acartia lilljeborgi, Oithona hebes, O. oswaldocruzi and Euterpina acutifrons.

Ecosystems and Sustainable Development 53

Among Tintinnina Leprotintinnus nordqvisti was dominant. The most frequent meroplanktonic group was Bivalvia veliger followed by Cirripedia nauplii. Meroplanktonic larval recruitment was reduced by landing, dredging and low estuary-ocean communication.

Total zooplankton density varied from 585 org.m^ to 65,989 org.m'l The dry season presented higher abundance (Figure 2). Copepoda (Paracalanus crassirostris and Oithona hebes) was the most abundant group (maximum 23,690 org.m'3).

Table 3. List of the zooplankton (without ROTIFERA) recorded at the Ipojuca River Estuary in August/90 (rainy season) and January/91 (dry season).* tycoplankton

TESTACEA Centropages velificatus (Oliveira, 1947) Arcellavulgaris Ehrenberg, 1838 Arcella dentata Ehrenberg, 1838 Calanopia americana F. Dahl, 1894 LabidocerafluviatilisE. Dahl 1894 Centropyxis acureata Stein, 1840 AcartialilljeborgiGiesbrocfa, 1892 FORAMTN1FERA Oithona nana Giesbrecht, 1892 *Textulariasp Oithona hebes Giesbrecht 1891 * Quinqueloculina sp Oithona oswaldocruzi Oliveira, 1945 * Planispirillina denticulata (Brady, 1884) Halicyclops oraeeburnensis Lindberg, 1957

Globorotalia sp Halicyclops thermophilus Kiefer, 1929 Tretornphalus bulloides d'Orbigny 1826 RADIOLARIA (Spumellaria) Coiycaeusgiesbrechti¥. Dahl, 1894 TINTINNIDA Euterpina acutifrons (Dana, 1852) Leprotintinnus nordqvisti (Brandt, 1906) *Nifroca sp 1 Tintinnopsis compressa Daday. 1 887 *Nifroca sp 2 Tintinnopsis lobiancoi Daday, 1887 *Longipedia sp Tuitinnopsis mortensenii Schmidt 1901 ^Natwopuspalusfris Brady, 1880 Tintinnopsis directa Hada, 1932 *Ecriinosomatidae Tintinnopsis tocantinensis Kofoid& Campbell, 1929 *(%GfzcQ3np6# /WKyywW (Blanchad &Ridiaid, 1891) Codonellopsis morchella (Cleve, 1900) CIRRIPEDIA

Favella a^W^^ (Oapai^& Laadimann, 1858) Lepas sp(nauplius) l, 1881) Balanus sp (nauplius and cypris) ISOPODA(manca) Eutintinniis tennis Kofoid & Campbell, 1929 AMPHIPODA HYDROIDA - Obelia sp PENAEIDAE (mysis) S1PHONOPHORAE (others) -Izw/asp SEGEST1DAE-Luciferfaxoni Borradaile, 1915 NEMATODA BRACHYURA (zoea and megalopa) GASTROPODA (veliger) INSECTA (larvae) PELECYPODA (veliger) BRYOZOA (cyphonauta) POLYCHAETA CHAEIOGNAIHA -6qgz%z rg/wA9 Conant, 18% Maupasia sp LARVACEA Nereis sp (larvae) Oikopleura longicauda (Vogt, 1854)

COPEPODA OikopleuradioicaFol, 1872 Paracalanus quasimodo Bowman, 1 97 1 Fritillaria sp Paracalanus crassirostris?. Dahl, 1894 QSTEICHTHYES (egg and larvae)

Table 4. List of the ROTIFERA recorded at the Ipojuca River Estuary in August/90 (rainy season) and January/91 (dry season). ).* tycoplankton *Rotariamtatoria(Pattas, 1766) *Lecanepapuana (Murray, 1913) *Rotaria neptunia (Ehrenberg, 1832) *Lecane leontiw (Turner, 1892)

*Lecanefiti'cata (Murray, 1913) Platyias quadricomis (Ehrenberg, 1832) *Lecane unguitata (Fadeew, 1925) *Bmchionuspatuluspatulus (O. F. Muller, 1786) *Lecanestenroasi(MQissii\er, 1908) *Brachionuspatuh4s macracanthus (Daday, 1905) *Lecane lunaris (Ehrenberg, 1832) ^Bivdwnus quadridentatus w#i3My(Daday, 1897) *I^cme W/a (Gosse, 1886) Bmchionnsplicotilis (0. F. Muller, 1786) *Lecawquadridentata(E\\rzrkxxg, 1832) , 1851) *Lecane sp *Cephalodellasp , 1832) PofyarthravulgarisCzrlm 1943 , 1886) Aspkwckna sp

3. F. Muller, 1786) *Testudiwllapatina (Hermann, 1783) *Lecane ciirvicomis (Murray, 1913) Filinia longiseta (Ehrenberg, 1834) F. Muller, 1776)

PHYTOPLANKTON

2000000 1800000 1600000 1400000 1200000 1000000 800000 600000 400000 200000 0

RAINY SEASON DRYSEASON

ZOOPLANKTON

70000 60000 50000 £ 40000 E> 30000 o 20000 10000 0 CoO CoO CoO CoO CoO CoO oCO 3888 £ g T- ro «o r£ o> 5 S r^ oi ^ co T-: co in RAINY SEASON DRY SEASON

Figure 2-Plankton density at the Ipojuca River Estuary, Pernambuco, Brazil, in August/90 (rainy season) and January/91 (dry season).

Ecosystems and Sustainable Development 55

At the rainy season it was registered a peak of zooplankton at 7:30 h and at the dry season two peaks were registered one at 9:30 h and another smaller at 20:30 h. Phytoplankton presented similar peaks which match inversely the zooplankton, showing intense grazing.

Plankton Species Diversity was high (> 3 bits.ind"') in most samples. No significant difference was observed between tides and seasons. Eveness was also high (> 0.5). The high diversity can be explained by the spatial heterogeneity.

Plankton species association presented 3 groups: i) marine planktonic; ii) marine-littoral and tycoplankton; iii) and marine estuarine residents. The low correlations in cluster mean according to Guzman del Proo et al? a complex food web. All these groups were most composed of r-strategists. However, in a constant impacted estuary many organisms are living in their maximum tolerance limit (Neumann-Leitao & Matsumura-Tundisi®). The 3 first Principal components were responsable for 52.97% of the variance. The first axis (21,04% of the variance) was related to the greater plankton abundance and contained the more frequent taxa in the area (marine estuarine residents); this group was influenced by salinity, transparence, dissolved oxygen and pH. Axis 2 (17,39% of the variance) was related to the marine littoral and tycoplankton. Axis 3 (14.54% of the variance) associated the eutrophic indicators species to nutrients, chlorophyll a and low oxygen. The area balance was strongly affected suggesting a disturbed plankton community.

5 References

1. Cavalcanti, L. B., Coelho, P. A., Eskinazi-Leca, E., Luna, J. A. C., Macedo, S. J. & Paranagua, M.N. Condiciones ecologicas en el area de Suape (Pernambuco - Brasil). Mem. del Seminario sobre el Estudio Cientifico e

Impacto Humano en el Ecossistema de Manglares, ed. UNESCO, Oficina Regional de Ciencia y Tecnologia para America Latina y el Caribe, Cali, pp. 243-256, 1980.

2. Eskinazi-Leca, E. & Koening, M. L. Distribuicao das diatomaceas (Bacillariophyceae) na area de Suape (Pernambuco-Brasil). Trabalhos Oceanogrdficos da Universidade Federal de Pernambuco, 19, pp. 73-100, 1985/86.

3. Gusman del Proo, S. A., Chavez, E. A., Alatriste, F. M., Campa, S., Cruz, G., Gomez, L., Guadarrama, R., Guerra, A., Mille, S. & Torruco, D. The impact of the Ixtoc-I oil spill on zooplankton. Journal of Plankton

/feyewc/z, 8 (3), pp. 557-581, 1986.

4. Melo Filho, J. A. S. Caracterizacao da situacao atual da area Programa Suape sob o ponto de vista poluicao ambiental. Recife, CONDEPE,

Comunicaqao Tecnica, 1, pp. 1-15, 1977.

5. Neumann, V. H. M. L., Queiroz, C. M. & Ivo, P. S. Bottom sediments of the Suape lagoon, Pernambuco - Brazil. Proc. of the 14^ International

Sedimentological Congress, Recife, 1994.

6. Neumann, V. H., Medeiros, C., Parente, L., Neumann-Leitao, S. & Koening, M. L. Hydrodynamism, Sedimentology, Geomorphology and

Plankton Changes at Suape Area (Pernambuco - Brazil) after a Port Complex Implantation. Anais da Academia Brasileira de Cencias, 70(2), pp. 313-323, 1998.

7. Neumann-Leitao, S., Paranagua, M. N. & Valentin, J. L. Ecology of planktonic rotifers of the estuarine lagunar complex at Suape, Pernambuco (Brazil). Hydrobiologia, 232, pp. 133-143, 1992.

8. Neumann-Leitao, S & Matsumura Tundisi, T. Dynamics of a perturbed estuarine zooplanktonic community: Port of Suape, PE, Brazil. Verh. ., 26, pp. 1981-1988, 1998.

9. Paranagua, M. N. Zooplankton of Suape area (Pernambuco-Brazil). Trabalhos Oceanogrdficos da Universidade Federal de Pernambuco, 19,

pp. 113-124, 1985/86.

10. Shannon, C. E. A mathematical theory of communication. Boll. Syst. Tech. J. 27, pp. 379-423, 1948.

11. Strickland, J. D. H. & Parsons, T. R. Production organic matter in the primary stages of marine food chain. Chemical oceanography, eds. J.P. Riley & B. Kirrow, London, Academic Press, pp. 477-610, 1963.

12. Strickland, J. D. H. & Parsons, T. R. A manual of seawater analysis. Bulletin Fisheries Research Board of Canada, 125, pp. 1-205, 1965.