Journal of Coastal }{pspal'ch Charlottesville

Effects of Surrounding Physical and Chemical Environment on the Spatial Heterogeneity in Phytoplankton Communifies of Bay,

Tetsuo Mukai

Institute of Environmental Chemistry Faculty of Engineering Hiroshima University Shitami, Saijo-cho, Highashihtroshtrna-shi, 724 Japan AHRTRACT _

M l r1-\ AI. T., 1~)~ 7 E ff'f.'ct." of surrounding physical a nd chemical environment 011 1hE' spat ial hplprogt>l1pitv in phytoplankton communities of Hiros.h ima Hav, .lapan. -lournal oIC()a ..... tal Research, :q:n, ~(;!I.:n9. Charloti osvillo. ISSN 07 4!l-()~()H. ~ . •••4""""" • The surface waters of Hiroshima Bay, a larg-e coastal embayment subject to marked eut­ ••• rophication. were sampled over a three month period. Important aspects ofin situ environ­ mental het.erogeneitv include (1) the phytoplankton community, which is sensitive to variations in environmental conditions, and (2) the surrounding physical and chemical environment as habitat for the phytoplankton community. Two multivariate analyses were used to elucidate spatial relationships between these two environmental heterogeneities. Cluster analyses based on phytoplankton composition indicated three different water masses that approximately correspond to the northern, western, and central-to-southern parts of the hay. Mult.iple discriminant analysis in water quality indicated that spatial dif­ ferences in phytoplankton composition throughout the bay were a primary response ofthe phytoplankton community to in situ spatial variations in the physical and chemical environ­ ment as represented by water quality.

ADDITIONAL INDEX WORDS: Aquatic ecosystem, cnrironmcntal hctcroecncit», phvtoplanhton communitv..«emi-cnclo ..... cd cuuslu] bov, uatcr qualitv, multicuriatc onalvsis.

INTRODUCTION relationships exist between the distributional pat­ terns in the aquatic organism community present Due mainly to tidal mixing, river inputs and the and the in situ heterogeneity of the surrounding morphometric features of a water body, environ­ environment. mentally heterogenous areas with a variety of physi­ In general, aquatic ecosystems may be described cal, chemical, and biological characteristics are in terms of (1) aquatic organism communities and frequently formed spatially and temporally in es­ (2) the surrounding abiotic (physical and chemical) tuarine and coastal water bodies. This sit uation is habitat. Consequently, heterogeneity of aquatic particularly marked in semi-enclosed coastal em­ ecosystems is approachable from these two view­ bayments such as Hiroshima Hay, where there is points. Of the various types of aquatic organism limited water exchange and increasing exposure to communities, the phytoplankton community was environmental stresses induced by human activi­ selected as primary indicators of changes in the sur­ ties. Thus, for the development of programs for rounding environments, especially in view of its water resource management and available utiliza­ place in the food web and becuase of its high adap­ tion of such aquatic ecosystems, it is becoming tability or high sensitivity to varying environmental increasingly necessary to make allowance for in situ conditions among organism communities. Para­ spatial heterogeneity of the environment. In addi­ meters of water quality, e.g., watertemperature and tion, it is of interest to elucidate whether ecological salinity, were studied because they characterize

86() 1() rccoiccd 12 February 19H1;; accepted in rcri..... ion 2:i June conditions of the physaical environment. Dissolved I.9H6 inorganic nitrogen (DIN) and phosphorus (DIP), 270 Mukai primarily important anthropogenic su bstances in among various factors. Therefore, of the various eutrophicated coastal water bodies, are also con­ mu Itivariate analyses widely used in ecological sidered in this study. These water qualities are also work, the procedure proposed by (;REEN and major factors that control algal growth and hence VASCOTTO (1978) was applied as a means: in situ affect the distribution of the phytoplankton com­ spatial heterogeneity in the phytoplankton com­ munity in estuaries and other coastal waters. munity was identified by cluster analysis based on The major purpose of this study is to thus clarify the phytoplankton composition. Further, multiple the degree to which the phytoplankton community discriminant analysis (canonical analysis) of the responds to the surrounding environment, par­ surrounding environment, with respect t.o water ticularly from the viewpoint of spatial hetero­ quality as a phytoplankton habitat, was conducted geneity of aquatic ecosystems on a macro scale. In over a wide area in Hiroshima Hay, .Iapan. Results complex environments such as estuarine and coast­ of these statistical procedures provided useful al ecosystems, spatially unidirectional gradients of information for understanding and describing eut­ various environmental factors are not always evi­ rophication processes in Hiroshima Bay (Ml"KAI ct dent, presumably due to complex interactions aL, 1985).

N

021 41 0 017

olB

10 !

Figure 1. Hiroshima Ray, -Iapan. Numbers indicate t he number of sampling stations.

.Iournal of Coastal Research, Vo!. :L No. :L 19H7 Spatial Heterogeneity in Phytoplankton 271

STUDY AREA depth) were taken with Van Dorn bottles using a boat of the in October 1977, Hiroshima Bay (Figure 1), situated on the west­ .Iune 1978, and March 1979. Salinity and water ern part of the , is a typical example temperature were determined with a Salinity and of the semi- enclosed coastal embayment which has Temperature Measuring Bridge (Electronic a surface area of about 946 km", a volume of about Switchgear (London) Limited, Type MC-5L cali­ 24.2 x 109 m", and an average depth of25.6 m. The brated periodically with standard seawater and a mean freshwater discharge into the bay is about mercury thermometer. 149 x 10f) m'd-1. The northern part of Hiroshima Water samples for nutrients and chlorophyll a Bay, the most enclosed region of the bay, receives analyses were prefiltered immediately after collec­ large amounts of municipal-industrial effluents tion on board through a precombusted 0.8 /-lm glass generated in Hiroshima City (population is about fiber filter (Toyo GA 200) and stored in an ice chest one million) either directly or through the Ohta during the return to the laboratory. Nutrient con­ River. This area is thus the most polluted and eu­ centrations were immediately determined for dis­ trophicated compared to other parts of the bay. Red solved inorganic nitrogen (DIN) as ammonium-N tides also frequently occur in this area. In the west­ (GRASSHOFF and ~JOHANNSEN, 1972), nitrite-N ern part of Hiroshima Bay, treated sewage waters (BENDSCHNEIDER and ROHINSON, t952) and are discharged mainly from oil refineries, petro­ nitrate-N (WOOD ei al., 1967), and dissolved in­ chemical, textile, pulp and paper industries in the organic phosphorus (DIP) as phosphate- P Iwakuni- Ohtake industrialized regions located on (MURPHY and RILEY, 1962). The filter residue was the west coast of the bay. The central to southern used to determine the concentration of chlorophyll parts of the bay contrastwith these areas because it a by colorimetry after acetone extraction is largely free from land- based sources of pollution. (STHICKLAND and PARSONS, 1968). This southern area is only subject to secondary Non- prefiltered water samples used for phyto­ pollution associated with currents within the hay. plankton analyses were preserved with neutralized Although data relating to the loading of major nu­ :3l)1,) formalin and LugoI' s solution immediately after trients that stimulate algal growth are very scarce, collection for estimation of phytoplankton com­ the equivalent of about :31.91 tons of total nitrogen position in the laboratory. Because regional dif­ per day and 3.56 tons of total phosphorus per day ferences in the phytoplankton community over the entered the bay (whole- bay basis) in 1977. These entire bay were detectable at the genus level in the figures were provided by the Hiroshima pre­ preliminary survey, phytoplankton were identified fectural authorities. to genus and enumerated using a binocular micro­ Hiroshima Bay has low flushing characteristics scope (Nikon Model S-Ke) with phase-contrast due to limited water exchange capacity with neigh­ optics. Counts to at least1 O:~ cells were recorded for boring seas through the channels of the extreme each sample, because the increase in the value of southern part of the bay. An average period in the Shannon-Weaver diversity index, a measure of which a parcel of water remains within the bay was the structure ofthe phytoplankton community, was estimated to he of the order of 151 tidal cycles, or no longer observed at 1 O:~ cells or more in the pre­ approximately 76 days. This observation is based liminary experiment. on tracking miniature floating balls and tracing the Cluster analysis (based on phytoplankton com­ path of dyes using the large-scale hydraulic model position) and multiple discriminant analysis (based of the Seto Inland Sea containing Hiroshima Hay on water quality) were performed on a HITAC (lJESHIMA et al., 1984a, 1984b). While there are M-200H computer at Hiroshima University using other studies of Hiroshima Ray (e.g MUKAI ct al., programs contained in Biomedical Computer Pro­ 1980,1982,1984,1985), there is little information grams (BMI)P)(1975) and a Statistical Package for concerning in situ spatial heterogeneity of this the Social Sciences (SPSS)(NIE et al., 1975), res­ aquatic ecosystem. pectively. Cluster analysis (hierarchical classifica­ tion analysis) in each sampling month was based on MATERIALS AND METHODS phytoplankton genera which appeared during the sampling periods (Tables 1, 2 and :1) and their rela­ Sampling stations were established to include tive percentage abundance at each station. Sim­ the major geographical su bdivisions of Hiroshima ilarities in phytoplankton composition between Bay (Figure 1). Surface water samples (0.5 m in stations were calculated from Euclidean distance.

.lournal of Coastal Research, Vol. ;~, No. ;~, 19H7 '272 Mukai

This distance between clusters was also computed Table 1 Auera,l,'"e relatiuc composition of the major genera of with respect to the centroid of each cluster. On the phytoplankton (,'d for threo fi!"OUps (A H. and C) identified by cluster analysis in ()cto!>l'r /977. other hand, multiple discriminant analysis (canoni­ cal analysis) using environmental factors was made on the basis of natural logarithmic transformation Croup of physical and eutrophication-related water qual­ A B C ities such as water temperature, salinity, DIN and Sheletoncma P,2.;) :W.~) LUi DIP. In the present study, I)IN represents the total Cho.ctoccro« 4.1 22.S :~;LS sum of the concentrations of ammonia-N, nitrite-N Tholassioeiro 4.4 1.4 and nitrate-N. Nit.zschia :L9 ;).1 :tfl Thnlassil)nl'ma O..-l l.B ;Ui Asterionclln 1.1 6.P, O.B RESULTS J.cptocvlindrus 1.:~ 2.7 1.2 Rhirusolcnia 0.1 0.7 0.4 Phytoplankton Community lsoctcriastrum 0.4 O.R Coscinodiscu...,· O.:~ 4.9 lB.;) Diiylum o.t O.B l.~ The phytoplankton genera that occupied Tholassiothrix () . :~ O.G Hiroshima Bay on each sampling date are sum­ Eucampia 0.1 O.r-, Hemiaulu« 0.2 marized in Tables 1, 2 and 3. The numbers of Guinardu: 0.:1 o.:~ 2.4 genera varied considerably during the sampling Biddulphia 0.4 periods, possibly because of seasonal variations. Of Flagellates 0.:2 6.0 6.9 Others 1.2 6.~ all genera found during each sampling period, 11./ Skeletonema; Chaetoceros, Thalassiosira; Nitzschia, Leptocylindrus, Rhizosolenia; and flagellates were Table 2. Same as Table I, hut for ,JUTll' 197H the most common constituents of the phytoplank­ ton community. As a whole, the phytoplankton Grnup composition in October 1977 was relatively diverse A Ii C and showed a greater variety ofgenera compared to other sampling months. Shclctoncma 0.9 11.B 1;').1 Chactoccros 1. :~ ;Ll Dendrograms produced by cluster analysis, sum­ Tholassioeira o.:~ 1. :~ O.G of-squares agglomeration, based on the phyto­ Nitzschia 1.2 LO l.h plankton composition of the major genera for the l.cptocvlindrus 1.0 Hi.7 :~4.7 Rhizosolrnia 0.2 ;).4 17.6 three groups (or clusters) identified are also in­ Ccrutaulina 1.7 2.1 dicated in Tables 1 to 3. As seen from the den­ Flagellates ~)r) .;~ S7.0 2:L6 drograms in each sampling month, the stations Others 1.1 'l.H l.H were tightly divided into three distinct groups with differing phytoplankton composition, designated Tahlc :]. Same a .... Toblc l . hut for March 1979. by A, B, and C in the cluster analysis. These three clusters were produced approximately at the :31, (;roup 36, and 48.5 levels of similarity based on sum-of­ A Ii C squares distance in October 1977, June 1978, and March 1979, respectively (see Figures 2, 3, and .'-,'kl'l('(oflemn 7S.P, IP,.n 0.;) 4). Cliaetocero« G.G :Hl.6 f).H 'l'h(l[(l.,\",i()sira OA 0.6 O.S There were marked differences in phytoplankton Nitzschia 0.;) :2.1 1.0 composition among the three groups identified by Thalassioni -ma 0.1> 0.1 cluster analysis for each sampling month. In Oc­ I.eptocv!indrus O.t> O.! Rhizosolenia o.: n.2 0.7 tober 1977, in Group A, Skeletonema was the most ( 'oscinodiscus 0.1> 0.1 n.B abundant genera, comprising 82.5'/:' of the total Diivlum O.!> phytoplankton community. Other genera, however, Eucurnpia [).~ 11.B ;~:-l. 0 were sparsely distributed. In Group B, Sheletonema Hcmiaulus o.t 0.1 0.2 Guinardui 0.1 0.1> O.S remained dominant but its relative composition Corethron 0.1> decreased to 39.9();, of phytoplankton present com­ Bidtlulphia 0.1> pared with Group A. Chaetoceros was the second Flagellates 11.9 :W.O S4.1 Others 0.2 0.2 O.R dominant genera. In Group C, Sheletonema de-

.Iournal of Coastal Research, Vol. ;{, No. :~, I BB7 Sput ial Heterogeneitv in Phytoplankton

SUM OF SQUARES 60 40 20 a ( 3 ( 33( 35 ( 38 ( 37( 2 ( 39( 40( I) 32 ( I 29 ( I 1 25011 22 ( I ) 36 (I II ) 17 ( I ) 30 (I ) 26( III) A------j 18 ( I ) 19 ( I ) 23 ( I) 41 (III) ?2 fdd 24 ( III) c 15 (III) 16 ( III ) 21 ( II ) 34 (1I I) B 6 ( I ) 9 (I I) 1 1 ~ IfI ~ 10 ( r J) 5 ( I) Figure ? Clust er-analysis dendrogram of phvtoplankt on composition, hased on sum-of-squares dist ance in October 1977

Toblc-! f nscriminant nnulv-i« o/stulio1/s !Jasl'{!on surfac« u-atcr quolitic« ofHiroshima Hay in October /977. June /97H, and March 1979. Th« data ucrc iran ...../ormed into thr natural louurithm.

Ort oher 1~)77 .luno 197H March 19/~ Discriminant function 1 I 1 2 Canonical correlation (U)()~) (1.~91 O.H4G O.:24:l O.H,SH O.U):! Percent of separation HfiA(i I ;l.;)4 97,!)7 :!.4:l 9;")';)/ ;L4:~

Standardized discriminant function coefficients

Variahlps \Vater temperature O./IO --O.7(iO -().[)fi7 0.729 -0,120 0.199 Salinity 0.177 O.(i;W O.H;")() n.isn 1A!):! O.:~:W nI:\ O.:2;)l) l.:2:n 0.272 -O.;)!)1 1.1 :):~ l.4;W DIP ().2;~ 1 -O.7I;) -O.;)l~ 0.160 -0.077 -O.;)7;~

creased in its relative composition and Ch aetoccros creased to 57 .O(;{', of phytoplankton present. In con­ spp. were dominant genera. Group B is thus inter­ trast, Leptocylindrus and Sheletonema were rela­ mediate between Groups A and C (Table 1). In -Iune tively abundant, comprising 16.7% and 11.8 'X' of 1978, in Croup A, the most abundant genera con­ the total phytoplankton community, respectively. sisted of flagellates (95.:~(X of the total phyto­ In Croup C, flagellates were the second abundant plankton community) whereas other genera were genera withLcptocylindrus being the first dominant extremely low in relative abundance. In Group R, (Table 2). In March 1979, in Group A, Sheletonema flagellates were still the most abundant hut de- was dominant (7 5.8~, of phytoplankton present)

.Iournal of Coastal Research, Vol. :L No, ;~, 19R7 274 Mukai

SUM OF SQUARES 60 40 20 o 1 (I ) 40( [) 38 ( II) 5 ( 1 ) 39 ( I ) 2 ( I ) A.------~ 37 ( I I ) 4 ( I) 29(~) T1 ? l~ d 33 ( I I) 23 ( II ) 17 ( II I ) 6 (l [1) B 32 ( I I) 28 ( u ) 26 ( II) 21 ( II ) 35 (Ill) 27 ( I ) 31 ( I I ) 36 (1I I) 25 (Ill) 9 (Ill) 16(111) 14(1I1) 15 ( 111) 24 (Ill) c 34 ( [II ) 41 (III) 10(111) 19 ( I r ) 18 ( 1I) 20 (III) 22 (III) 30( III) Figure:L Cluster- analysis dendrogram of phytoplankton cornposit ion, based on sum-of- sq uares distance in ,June 197 H; ast erisk denotr-s the lack of water quality data.

Table G. A 1.)('rtuu I ioaicr qualitic« [or three grout)« (I, Il. and III) s('/)(]rated bv discriminant nnalvsi». '()~I'!h('r with chlorophvll a canerntral itin.

October 1977 .lune 197H March 1979 (~roup (~roup Group

II III II III II U] Wah'r temperature CC) 22.20 2:LHfl 22.G7 2~.;) 1 2:1.10 21. 70 12 ,O:~ 11.78 11.(;;~ Salinity (0/",) ;)1.:19 :~:LOS :~2.[)2 20J)O 2(),;)() 2H,HI :W.72 ;~2.HO ;~;L;)9 DIN (IJ-gat 1 1) 1.1H 1. 7~) 2.2f) :dL2 1. :~H 1.;~2 ?,Of) 1.09 2.7;) DIP (IJ-gat 1- 1) 0.;\7 O.;)} O.GO 0.90 0.14 O.1:~ 0.2-1 0.07 O.2·t Chlorophyll (J (IJ-g I-i ) 10.4B 1.70 :2.07 7;L[) 1 11.47 ~.H9 {,AO ;L69 2.'27 while in Group B Chaetoceros was dominant (:36.6(X habitats on phytoplankton composition, water of the total phytoplankton community) accom­ quality (water temperature, salinity, DIN and DIP) panied by a marked decrease in Shelctonema was subjected to multiple discriminant analysis (18.0%). In Group C, f1agellates were dominant, based on the three groupings in phytoplankton followed byEucampia; Sheletonema was reduced to community composition described in Figures 2 to 0.5'/;) of phytoplankton present (Table :i). 4. I assumed that the physical and chemical en­ vironment of the study area comprised the three Surrounding Physical and Chemical environmentally heterogeneous areas. Consequent­ Environment ly, by using the two discriminant functions ob­ tained, each station was discriminated and sep­ In an effort to clarify the influence ofsurrounding arated into three groups (with respect to water

.lournal of Coastal Research. Vol. ;~, No. ;~. I DH7 Spat inl Hpj t'l'ogeneity in Phvtoplankton

SUM OF SQUARES 60 40 20 o I I I I I I I 1 ( I ) 38 ( I ) 6 ( I ) 37 ( II) ~ 35 ( II I) I 26 ( II ) 5 ( I ) I r------c 4 (~) 3 ( I ) A L-e= 2 ( I ) 22 ( II ) r 23 ( 11 ) 33 (III) 17 ( II ) 9 (III) r- 15 ( Ill) I L...- 41 ( lll) c ~ I I 34 ( III) I 16 ( [11 ) 14 (Ill) ~ 11 (Ill ) I 24 ( III ) 10 ( UI ) 32 ( I ) 27 ( 11 ) 14 21 ( I I ) I 36 ( 11 I) 1----1 28 ( II ) 30( 1 ) B 29( I I) 19 ( II ) 20 ( II) 18 ( 1I ) 40( I) 25 (11 I) I 39 ( 1 ) 31 ( I ) Figure 4. Clust er-nnnlvsis dpno!'ogram of ph~.. toplaukton composition, hased on su m-ol-xquares distance in March 1979. Asterisk denotes the lack of watt'!' qualitv data, quality) to produce maximum differences among apparent, possibly because their concentrations groups. The results of these operations are sum­ are subject to marked fluctuation in response to marized in Table 4. 'The average water qualities for algal growth and discharge of these su bstances into the three groups so separated are given in Table f> the bay. In some cases reduced salinity was accom­ together with chlorophyll a concentration. Figure f panied by a high concentration of nutrients. The shows these groups projected on the two axes of the concentrations of chlorophyll a decreased with discriminant functions (shown in Tahle [)) so that increasing salinity in all sampling months. the stations with similar environmental regimes may form a separate cluster on this graph. The Spatial Heterogeneities in Phytoplankton three groups separated are denoted by I, II, and III Communities in Relation to Surrounding of multiple discriminant analysis in each sam pling Environment month. On the whole, the separation of the stations into the three groups with different water quality The geographical distributions of these three environments seems to be relatively distinct in phytoplankton communities and surrounding June 1978 and March 1979, whereas in October habitats are shown in Figures (-) and 7, respectively. 1977 the stations appear to be loosely separated. It is evident from these figures that these three During the sampling period, average water tem­ groups were closely related to the geographical perature tended to increase in October 1 ~)77 and position of each station. decrease in March 1979 with increasing average Interpretations of spatial heterogeneity in the salinity. Trends in DIN and f)IP, which are as­ phytoplankton community are summarized as fol­ sociated with eutrophication, were not readily lows. In October 1977, Group A included stations in

.Iournal of Coastal H('spal'ch, Vol. ;~. No, ;~, 1!-)H7 Mukai

from the central to southern parts of the bay (Figure 6 b). In March 1979, Group A consisted of stations off Hiroshima and Iwakuni. Group R represented

a) o nearshore stations along the northern and western 2 f- coasts of the bay, whereas Group C characterized most stations in the central and southern parts of the bay (Figure 6 c). o r- The three groups were distinguished geo­ • graphically on the basis of water quality. In October -1 - • • ] 977, Croup I was composed of stations off o o -2 r- o Hiroshima and in the western coastal areas. Group

I I I I I 1 II characterized stations near the mouth of the bay. Group III represented stations from the central to z b) o 2 f- • southern parts of the bay that were almost free from I-­ • • U land- based pollution (Figure 7a). In .Iunc 1978, Z ::::J o •• Group I was characterized by stations situated in LL o o • I-­ o f- the innermost region of the bay, i. (' those which are «Z o o susceptible to the highest anthropogenic inputs in z -1 r- o Hiroshima Bay. Croup II represented stations from 2 oc -2 ~ o the northern to to western parts of the bay, whereas u if) Croup III included almost all stations in the south­ o -3 r-- o ern area (Figure 7 b). In March 1979, Group I was

I I I II I L restricted to stations from the northern part of the hay, whereas Groups II and III tended to occupy c) o 2 r- o stations from the west ern and central-to-southern o parts of the bay, respectively (Figure 7 c). o o In sum, environmental heterogeneities In o r-- • Hiroshima Bay were successfully delimited by •....• biological physical and chemical features. Further, -1 t- • • as seen from comparison of Figures 6 and 7, spatial -2 t- • patterns in heterogeneity of the phytoplankton J L J l l I community closely resembled those of surround­ -5 -4 -3 - 2 -1 0 1 2 3 4 ing environments. DISCRIMINANT FUNCTION 1 Figure G. Sampling stat ions in t he into t h"ep watcr-qualitv groups dust ered by similar environment al regimes, for Oct ober DISCUSSION 1977 (a), .lune E17H (h), and March 1979 (c). The ope-n circles, solid cirlces, and trianlges show groups L II. and III, rcspertivobv, (;roups I, II, and III, based on multiple discrimi­ nant analysis of water quality, are indicated in parentheses in Figures 2 and 4, together with the northern and western nearshore areas that were clustering of the stations into Groups A, B, and C, exposed to major river and wastewater inputs. based on phytoplankton composition. Croup B represented many stations t hat were adja­ In October 1977, Group A contained almost all cent to open channels whereas Group C consisted the stations of Group I, except for Stations 2.5, 26. of stations in the central and southern parts of the :~6, and 41 of Group III. On the other hand, a large bay (Figure 6a). In .Iune 1978, Group A was com­ part of Groups Hand C contained the stations of posed of stations in the extreme northern part ofthe Groups II and III, with the exception of Stations 4, bay that experienced extreme eutrophic condi­ 5, and 6 of Group I; (;roup C was composed of the tions. Group B included stations that were con­ stations of (;roup TIl alone while Group R was tiguous to the northernmost part of the bay, as dominated by the stations of Group II (Figure 2). In shown by Group A, and stations in the western part ,June 1978. Group A was nearly composed of the of the bay that were subject to relatively strong stations of (;roup I (6 out of 8 stations), except for influences of river discharge or direct wastewater Stations :~7 and :38 of Group II and Station 29 with inputs. Stations represented by Group C extended an unfortunate lack of water quality data. In Croup

.lournal of Coastal Research, Vo!' ;~, No. :L I ~lH7 Spat ial Het f'rogeneit:v in Phytoplankton 277

Figure 6. Ceographical distribution of the three groups with respec-t to the phytoplankton communities, reprcsent ed by the open, solid and small solid circles (nroups A, H, and C, respect ivclv), for October 1977 (a), .luno 197S (h), and March 1979 (c).

Figure 7 Geographical distrihut ions of the t hree groups wit h rcspect to the surrounding hahitat s, for Oct ober 1H77 (a), .June 1~)7 R (h). and March 1979 (d. The open, solid and small solid circles show Group» I, II, and Ill, respect ivelv.

B, the stations of Group II were more abundant dominated by stations of Group II (7 out of 14 than thoseofGroupslandIII(7 out.of l S stations), stations: see Figure 4). whereas a large portion of Croup C was composed The above results indicate that an ecological of the stations of (Iroup Hl (1:3 ou t of 15 stations: relationship exists between the phytoplankton see Figure :3). In March 1979, most of Group A con­ community and its surrounding habitats. On the tained stations of both Groups I and II, while all the other hand, when spatial relationships between the stations of Group C were separated into Group III phytoplankton community and surrounding en­ alone with respect to water quality. Group H was vironment is considered, it seems that the dis-

.Iournal of Coastal Research, Vol. ;~, No. :l, 19H7 '27R Mukai tributions of phytoplankton community in the water quality on the phytoplankton community be­ study area approximately parallel major physical cause the spatial inhomogeneities in the phyto­ and chemical conditions. This relationship may be plankton community in estuarine and coastal em­ interpreted as a primary response of the phyto­ bayments result from complicated interactions plankton community to changes in environmental among water qualities considered here and because conditions, since the phytoplankton community is multiple other factors of unknown relative impor­ generally sensitive to fluctuations in the surround­ tance may be involved ('J'AKAHASHI and FlTKAZA\VA, ing environment and thus can often be utilized as 1982; 'rAKIMO'l'O et ai., 1~)R2, 198~3). Finally, it seems biological indicators of water pollution (c.g that the local physical and chemical environment WILLIAMS, 1968; VILLE(;AS and C~I;\lEI{, 197~3): dif­ greatly influences the kinds of phytoplankton that ferences in phytoplankton composition are con­ occur, as well as regional differences in phyto­ sidered to relect differences in the physical and plankton composition. These observations could chemical environment as represented by water lead to better understanding of the relative sig­ quality. 'rhus, patterns of variability in the con­ nificance of regional characteristics in eutrophicat­ stituent genera provide more information about ing processes Hiroshima Bay (MUKAI et al., 1985). characteristics of the habitat than does variation in a single genus. Further, it seems that these dif­ A(~KNOWLEDGEMENTS ferences in phytoplankton composition are at­ tributable to differences in microhabitats caused I express my gratitude to the Hiroshima prefec­ by in situ environmental heterogeneity within the tural authorities for their great assistance in sample bay and corresponding habitat preferences of in­ collection. I would also like to thank Mr. H. dividual phytoplankton species. In addition, as Takayama of the Hiroshima Fisheries Experimen­ revealed in dendrograms, the number of stations tal Stations for his great help with phytoplankton constituting each group (or cluster) with respect to identification. In addition, I am most appreciative the phytoplankton community appears to fluctuate of the efforts by many students, too numerous to in response to the magnitude of in situ hetero­ mention, in sample collection and analysis. Finally, geneity in the surrounding physical and chemical special thanks are due to Dr. K. Takimoto for environment that presumably varies with spatial his encouragement and kindness during this and temporal fluctuations in river discharge, indus­ investigation. trial and domestic activities. anthropogenic inputs, hydrographical conditions, etc. which are charac­ LITERATURE CITED teristic phenomena in estuarine and coastal en­ BEI)SCHNEIDER, K. and ROBiNSON, R.»J., 1952. A vironments. Accordingly, these three types of new spectrophotometric method for the determination group with respect to the phytoplankton com­ of nitrite in seawater. Juurnal of Marine Research 1L munity occupied geographically varying propor­ H7~96. tions of Hiroshima Bay in each sampling month. For RMDP, 197G. HM[)J> Biomedical Computer Program ...,' (Dixon, W.,J., ed.). University of California Press. this reason, it was difficult to draw consistent geo­ Cl{ASSHOFF, K. and .JOHANNSEN, H., 1972. A new graphical boundaries among the three regions of se nsit ive and direct method for t he automatic deter­ Hiroshima Bay. The patterns of water mass flow mination of ammonium in sea water. Journal du Consri]. (see Figures 6 and 7) were suggestive of t he coun­ Conscil International pour (Exploration de La Mer, ;~4, terclockwise circulation which was observed by the G1G-;)21. nREEN, R.H. and VASCOTTO, (~.L., 1978. A method Maritime Safety Agency of -Iapan within the for the analysis of environmental factors controlling pat­ central-to- southern parts of the bay (see Figure 1:3 terns of species composition in aquatic communities. in Mt JKAI et al, 1985). These 0 bservations were Water Research, 12, r)8:~~f)90. also confirmed in a hydraulic model experiment MUKAI, T.; l'AKIMOTO, K.; SEKIGA\VA, K., KANESHICE, T.; KANESHIGE, N. and MYO.JO, M.. (UESHIMA et al., 1984a, 1984b). At any rate, it can 19HO. Diurnal variation in photosynthetic rate of phy­ he presumed that there existed at least three dis­ toplankton in the bag experiment. Bulletin ofthe Faculty tinct types of water mass based on differences in of Eruiinecriru; Hiroshima University. 29, 101-106. the phytoplankton community as reflective of dif­ MUKAI, '1'.; TAKIMOTO, K. and YAMAMOTO, T., fering environmental regimes, occupying the vary­ 19H2. C haracterist ics of behavior of phthalic acid esters in a discharge process from river into the coastal marine ing proportions of Hiroshima Bay. regions. Memoirs of the Faculty of Engiricerini; As shown in Table 4, it was rather difficult to Hiroshima Uniucrsiiv, H, 61-68. specify individual effects and relative importance of MUKAI, 1-'.; TAKIMOTO. K.; SHIBATA, T.:

.Iournal of Coastal Research. Vol. :~, No. :~, 19H7 Spatial Het erogeneitv in Phytoplankton 279

KOBAYASHI, K.; and ABE, H., 1984. Optical proper­ Japan Journal of Water Pollution Research, 5,91-99. ties of sea water and their seasonal variations in the TAKIMOTO, K.; MUKAI, T. and MATSUMOTO, K., coastal sea. Japan Journal of Water Pollution Research; 198~L Influence of trace organic pollutants on the coast­ 7,11-19. al ecosystem n. Distribution of urea in the sea and its MUKAI. T.; TAKIMOTO, K.; SHIBATA, T. and ABE, effect on the growth of algae. Japan Journal of Water H., 198fJ. Simulation study of eutrophication in Pollution Research 6, 105-111. Hiroshima Bay. Simulation of particulate and dissolved UESHIMA, H.; HASHIMO'rO, E.; YAMASAKI, M. and matter using cyclic transformation of carbon. Water 'l'AKARADA, M., 1984a. Tidal exchange characteris­ Research 19, f) II-52£). tics of Hiroshima Hay by hydraulic model experiment I. MURPHY, ~J. and RILEY, ~J.P., 1962. A modified single Residence time under non- stratified condition. 1984 's solution method for the determination of phosphate in AutumnMeeting ofthe Oceanographical Society ofJapan natural waters. Analytica Chimu:a Acta, 27, :11-:16. (preprint), Paper 1:19. NIE, N.H.; HULL, C.H.; JENKINS, ~J.G.; STEINBREN­ UESHIMA, H.; HASHIMOTO, E.; YAMASAKI, M. and NER, K and BENT, D.H., 1975. SPSS: Statistical Pack­ TAKARADA, M., 1984 b. Tidal exchange characteris­ age for the Social Sciences, 2 nd ed. Mctlraw-Hill, New tics of Hiroshima Bay by hydraulic model experiment II. York. Residence time under stratified condition. 1984 's STRICKLAND, J.D.H. and PARSONS, T.R., 1968. A A utumn Meeting ofthe Oceanographical Society ofJapan practical handbook of seawater analysis. Bulletin ofthe (preprint), Paper 140. Fisheries Research Roard of Canada, 1(17, :~ 11 p. VILLEGAS, I. and GINER, G.D., 1973. Phytoplankton TAKAHASHI, M. and FUKAZAWA, N., IH82. A as a biological indicator of water quality. Water Re­ mechanism of" red tide" formation II. Effect of selective search, 7,479-487. nutrient stimulation on the growth of different phyto­ WILLIAMS, L.G., 1986. Possible relationships between plankton species in natural water. Marine Biology, 70, plankton-diatom species numbers and water-quality 267-27 ~i. estimates. Ec()Lo~y, 4fJ, 809-82:3. TAKIMOTO, K.; MUKAI, T.; MYO~JO, M. and ITOH, WOOl), E.P.; ARMS'rRONG, F.AJ. and RICHARDS, F.A., A., 1982. Influence of trace org-anic pollutants on the 1967. Determination of nitrate in sea water by cadmium­ coastal ecosystem I. Biodegradation of LAS (Linear alkyl­ copper reduction to nitrite. Journal ofthe Marine Biologi­ benzene sulfonate) and its effect on the growth of algae. cal Association of the United Kingdom, 47, 23<11.

D RESUMEN D Se han tornado muestras durante un periodo de tres meses de las aguas superficiales de la hahia de Hiroshima, un amplio repliegue costero sujeto a marcada eutrofizacion. Los aspectos importantes de Ia heterogeneidad ambiental in situ compren­ den (1) la comunidad de fitoplancton, que es sensible a las variociones en las condiciones am bientales, y (2) el entorno fisico y chimico como habitat para la comunidad de fitoplancton. Se han utilizado dos analisis multivariados para obtener relaciones espaciales entre estas dos heterogeneidades ambientales. El analisis de colonias basado en Ia composicion del fitoplancton indica tres masas distintas de agua que corresponden aproximadamente a las partes norte, oeste y centro-sur de la bahia. Un analisis de discriminant.e multiple de la calidad del agua indico que las diferencias espaciales en la com­ posicion del fitoplancton en la bahia eran una primera respuesf.ra de la comunidad fitoplanct6nica a las variaciones espaciales in situ del entorno fisico y quimico, represent.ado por la calidad del agua.--MiRuel A. Losada, Unioersidad de Cantabria; Santander, Spain

D ZUSAMMENFASSUNG D Die Oberflachengewasser der Hiroshima-Bucht, die schwer Ubernahrung unterliegen, wurden iiber drei Monat probiert. Wichte Aspekte dieserin situ umweltbedingten Verschiedenartigkeit schiiessen ll.a. (1) die Phytoplanktongerneinde, die empfindlich gegen Anderungen del' umweltbedingt.en Umstande: und (2) die umringende physikalische und chernische Umwelt ein, die fur Standort del' Gemeinde halten werden. U m die Raurnverhaltnisse zwischen diese zwei umwelt­ bedingten Verschiedenartigkeiten zu aufklaren, wurden zwei Vielvariabelanalysen benutzt. Haufenanalysen, die aufdem Phytoplanktongehalt basiert wurden, zeigten drei verschiedene Wassermassen, die del' nordlichen, westlichen und zentral-sudlichen Buchtgebiet.e ungefahr entsprechen. Vielunterschiedungsanalysen del' Wasserqualitat zeigten, class die Raurnverhaltnissen des Phytoplanktongehalts uberall in del' Hucht eine anfangliche Erwiderung del' Phytoplank­ tongemeinde auf in situ Raumverhaltnisse del' physikalische und chernische Urnwelt war, die durch Wasserqualitat repraseritiert wird.-Steph('n A. Murdock, CERF, Charlottesville, Viruinia, lJ8A ;?J!flj ~

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