Rev. bras. oceanogr., 47(1):29-46,1999

Assessment of plankton community and environmental conditions inSão Sebastião Channel prior to the construction of a

produced water outfall

Sônia Maria Flores Gianesella, Miryam Bertha Burda Kutner, Flávia MarisaPrado Saldanha-Corrêa & Mayza Pompeu

Instituto Oceanográfico da Universidade de São Paulo(Caixa Postal 66149, 05315-970 São Paulo, SP, Brasil)

. Abstract: Plankton community and hydrological conditions were assessed as a part of anenvironmental diagnosis in São Sebastião Channel, before the building of a submarine outfallofproduced water from the oil maritime terminal ofPETROBRÁS. Samples were collected intwenty oceanographic stations located in the oil terminal neighboring area, during thespringtime of 1991. Dissolved inorganic nutrients and chlorophyll-a concentrations observedindicate an oligo-mesotrophic environment. Phenols and sulfides were absent, BOD values,except for three sampling points, were characteristic of unpolluted environments, aIthough oiland grease were found in half of the sampled stations. Phytoplankton and zooplanktoncommunities presented high diversity and evenness indices for the entire area. Phytoplanktonwas dominated by phytoflagellàtes and zooplankton was dominated by copepods, mostlyParacalanus quasimodo. Plankton community composition was similar to that from adjacentregions under low anthropogenic influence.

. Resumo: A comunidade planctônica e condições hidrológicas foram avaliadas como parte de umdiagnóstico ambiental no Canal de São Sebastião, previamente à construção de um emissáriosubmarino de água de produção, oriunda do terminal marítimo da PETROBRÁS. As amostrasforam coletadas em vinte estações oceanográficas situadas na área adjacente ao terminalpetrolífero, durante a primavera de 1991. As concentrações de nutrientes inorgânicosdissolvidos e de clorofila-a obtidas, indicam um ambiente oligo-mesotrófico. Fenóis e sulfetosnão foram detectados e os valores de DBO, com exceção de três pontos, foram característicosde ambientes não poluídos, apesar da contaminação por óleos e graxas ter sido observada emmetade das estações amostradas. O fito e o zooplâncton apresentaram altos índices dediversidade e equitatividade para toda área estudada. O fitoplâncton foi dominado porfitoflagelados, enquanto que o zooplâncton foi dominado por copépodos, especialmenteParacalanus quasimodo. A composição da comunidade planctônica foi similar à de outrasáreas adjacentes, sob baixa pressão antropogênica.

· Descriptors: Phytoplankton, Zooplankton, Nutrients, Suspended matter, BOD, Oil and grease,Environmental diagnosis, São Sebastião Channel.

. Descritores: Fitoplâncton, Zooplâncton, Nutrientes, Material em suspensão, DBO, Óleos egraxas, Diagnóstico ambiental, Canal de São Sebastião.

Contr. no. 823 do Inst. oceanogr. da Usp.

30

Introduction

The environmental diagnosis for theassessment of anthropogenic impacts is a generalconcern and a good evaluation represents a greatchallenge. Identification of stress indicators has beensearched intensively through the last decades.According to Rapport (1992) several characteristicsshould be considered in the health assessment of an

aquatic ecosystem: biotic community structure,species diversity, food chain length and populationstability are some examples.

São Sebastião ChanneI (SSe) andsurrounding áreas have been submitted toanthropogenic impacts, especially after thebuilding of the São Sebastião Harbor and of the"Duto e Terminais Centro Sul" (DTCS), an oilmaritime terminal. DTCS will contribute withanother contamination source for SSC waters: ao

aqueous eftluent composed mainly by producedwater (a sub-product originated principally in the oil-bearing formation). In the early lifetime of an oilfield, produced water content is smaIl but itconstitutes an increasing ITactionof the productionstream with time, until it gets too large foreconomic oil production (Sommerville et aI., 1987).During the production process, water and oil becomevery intimately mixed, and oil droplets andcomponents ITom the oil and added productionchemicals wiIl disperse or dissolve into theproduction water. This may increase the toxicity ofthe produced water towards the marine environment(Str<j>mgrenet aI., 1995). After discharge into thesea, the produced water wiIl be diluted(depending on local conditions). Evaporation andbiodegradation will change the content andcomposition of its inorganic constituents(Sommerville et aI., op. cit.).

The present work was conducted prior to thebuilding of the DTCS submarine produced wateroutfaIl, in order to establish a baseline descriptionfor future monitoring. Beyond the produced water,the aqueous eftluent should contain ballast water,high salinity water (resultant ITom the crude oildesalting process) and land drainage waters ITomDTCS area. As a part of this pre-monitoringprogram, sponsored by PETROBRÁS, other studieswere carried olit related to the determination of the

potential toxicity of this eftluent through bioassaysusing: the diatom Skeletonema costatum (AidaretaI., submitted), the gastropod Costoanachissertulariarum (Souza & Tommasi, 1997) and themysid Promysis atlantica (Phan et aI., 1994). Allthese studies pointed out the high toxicity of theeftluent indicating the necessity of a pre-treatmentand controlled disposal.

Rev. bras. oceanogr., 47(1). 1999

Study area

São Sebastião Channel (SSe) lies at theNortheast coast of São Paulo State (ITom 23°4] 'S -45°] 9'W to 23°53'S - 45°30'W), delimited by theSerra do Mar s]opes and São Sebastião Island(Fig. I). This funneI shaped channe] is curved a]ongits 25 km extension with the narrowest part (2 kmwide) in the center, enlarging up to 7.2 km, at theSouthem entrance, and 5.6 km at the Northern one.Along the longitudinal axis, depths range ITomaround 20 m at the entrances up to 50 m in the innerportion. The deepest part of this longitudinal axis iscloser to the is]and margin, being called "main axis"or navigation channel (Silva, ]995). High ]andssurround SSC providing substantial wind protectionITom the open sea (Furtado, ]978). Suchcharacteristics afford optima] conditions for theestablishment of harbor activities. Indeed, SSCshelters the DTCS which is the largest brazilian oilterminal, previously named as "Terminal A]miranteBarroso (TEBAR)", in operation since 1967, andalso one of the more important brazi]ian harbors, theSão Sebastião Harbor. As a consequence, thechannel is ITequentlyexposed to the introduction ofsmall amounts of oil ITomthe routine proceduresat DTCS. In addition, severa] accidenta] oi] spillshave occurred in the area. SSC has a]so been

submitted to intense anthropogenic impacts such ascoastal land occupation, urban sewage inputs andtourist exp]oitation. In spite of these vu]nerableconditions, few studies have been carried outfocusing this area.

The ChanneI is dominated by Coasta] Water(CW) but during spring and summer, a flow of highsalinity and low temperature waters (ACAS) can bedetected in the deepest ]ayers, main]y close to theSouthem entrance which acts as a duct for the South

Atlantic Central Water (SACW) penetration.Currents in SSC are predominantly to Northeast andthey may be highly variable in space and time. Windis the main forcing agent on water circu]ation, whiletidal currents have a negligible influence (CastroFilho, 1990). Strong currents{up to 1.4.knots) are acommon feature in the main axis and sêdimentationprocesses are more predisposed to occur in thecontinental margins than in the insular side (Furtado,1978). Aromatic hydrocarbon contamination wasdetected in many points along the channe] (Weber &Bícego, 199]): Authors attribute the h igh variationlevels to the oi] inputs ITom both DTCS" and oi]tankers present in thearea during the samplingsassociated to the surface water circu]ation.. Plankton

community of the Southern part of SSC wasevaluated by Gaeta et aI. (1990) during the autumn.Phytop]ankton was largely dominated by

GIANESELLAet aI.: Plankton community in São Sebastião Channel 31

phytoflagellates followed by diatoms andzooplankton individuais (predominantly copepods)showed a wide range of feeding behavior. Theauthors pointed out no stress indicators.

Material and methods

This study was carried out during the australspring (October 1991) in the neighboring area of theDTCS, surveyed through the samplings in twenty

stations (transects A, B, C and D, Fig. I). Sampleswere taken once in each station, at three watercolumn levels (surface, mid-water and bottom),according to the station local depth (Table I).Temperature measurements were obtained "in situ"using reversing thermometers and underwater lightpenetration was estimated through Secchi diskreadings. Euphotic zone thickness (z"u) wascomputed following the equation given by Poole &Atkins (1929).

BraziJ

'tI I I

:Sio ~ State :I i I~ ~-------I JI iI II IIIII

-'.---

Q

III

~ J_~;r~g~s_I I, J, I

I

: ,.bI

--:f..-Z35ÕiS,JI,I

...

41'

48'

49

23"50'S

4J.J22WI

Fig. 1. São Sebastião Channel, at the Northern coast of São Paulo State, and theposition of the 20 oceanographic stations performed at the neighboring areaofthe DTCS oil terminal.

32

Table I. Data on the 20 oceanographic stations performedat São Sebastião Channel: position, local depth,sampling depths and euphotic wne (Zeu)thickness.

Station Lat..L§

Long..L:!1

Local depth Sampling Z eu(m) depth (m) (m)

2346'48" 45 22' 43"

2 23 46'42" 45 22' 36"

3 2346' 32" 45 21' 54"

4 2346'42" 45 21' 54"

5 2346' 36" 4521' 48"

6 2347' 06" 45 22' 48"

7 23 47' 06" 45 22' 42"

8 2347' 30" 4522' 34"

9 2347' 14" 4522' 00"

10 2347' 12" 4521' 54"

11 2348' 18" 4522' 06"

12 23 48' 09" 45 22' 30"

13 2347' 57" 4522' 42"

14 2347' 49" 4522' 54"

15 2347' 48" 4523' 07"

16 2349' 17" 4523' 02"

17 2349' 18" 4523' 21"

18 2349' 11" 4523' 37"

19 2349' 00" 4523' 51"

20 23 48' 46" 45 23' 53"

6

10

30

22

10

6

20

31

15

6

6

20

36

21

6

7

20

43

20

7

o2.5

5

O

4

O

14

28

O

10

20

O

4.59

O

2.5

5

O

714

O

15

30

O

7

14

O

36

O

2.5

5

O

9

18O

1734

O

9

18

O

2.5

5

O

36

O

9

18

O

21

42

O

9

18

O3

6

10.8

13.5

13.5

10.8

9.5

8.1.

31.0

30.0

21.6

16.2

24.3

30.0

13.5

13.5

5.4

12.0

10.8

9.5

10.8

6.7

Rev. bras. oceanogr:, 47(1), 1999

Salinity was determined from samplescollected with Nansen bottles and analyzed by theinductive method. Conductivity ratios were convertedto salinity values following UNESCO (1981).Samples for chemical and biological analyses weretaken with Van Dom bottles. Water samples werefiltered through GF/F Whatman filters, which wereused for phytoplankton pigments and suspendedmatter determinations. Filtered water was frozen for

posterior determination of nitrate, nitrite, ammonium(Aminot & Chaussepied, 1983), phosphate andsilicate (Grasshoff et aI., 1983). Total Chlorophyll-a(Chlorophyll-a + Phaeophytin-a) was determinedaccording to Lorenzen (1967) and suspended matter(total, organic and inorganic fractions) by thegravimetric method (APHA, 1985). Samples forother analyses were taken direct1y from the bottles.Total oil and grease (partition gravimetric methodafter solvent extraction), sulfide (iodometric method),phenols (4-aminoantipyrine method) andbiochemical oxygen démand (BOD) were determinedaccording to APHA (op. cit.).

Bottle samples for phytoplankton countings(Utermõhl, 1958) were fixed with neutralformaldehyde (0.4% final concentration).Microphytoplankton samples were taken byhorizontal trawls in surface waters (net of 30 11mmesh) and preserved with neutral formaldehyde (4 %final concentration). The qualitative analysis wasperformed under a phase contrast optical microscope.

A vertical trawling with a net of 200 11mmesh and 50 cm mouth collected zooplanktonsamples. The organisms were preserved with neutralformaldehyde (4% final concentration). Watervolumes passed through the net were estimated asdescribed by Boltovskoy (1981). Subsamples wereobtained using Motoda sampler (Omori & Ikeda,1984).

Diversity (H') and evenness (r) indices werecomputed according to Shannon-Weaver (1963) andPielou (1966) considering only the identifiedorganisms (at leveI of genera or species) ofphytoplankton and zooplankton communities.Indices for phytoplankton were computed based onthe sum of results obtained at the three different

. depths in each station. Zooplanktonindices werecomputed based on.Copepod counts.

Principal Component Analysis (PCA, senseLegendre & Legendre, 1983) was applied to thephysical (temperature, salinity), chemical (dissolvednutrients, oil and grease) and biological (total Chl-a,active Chl-a, BOD, suspended matter andphytoplankton density) data sets. Zooplankton datawere not included in the analysis on account of thesampling methodology. Each descriptor set wastransformed to normalized variables with zero mean

GIANESELLA et aI.: Plankton community in São Sebastião Channel

and unit variance. The analysis was done usingFITOPAC software (Shepard, 1994).

Results

Vertical distribution ofthe studied variables

in transects A, B, C, and Dare exhibited respectivelyin Figures 2, 3, 4 and 5. .

On all transects, the water column showed acontinuous thermai stratification without a defined

thermocline. Temperatures varied fi'om 25.20°C(surface) to 17.25°C (bottom waters), indicating thepresence of CW in the upper layers and waters withhigh degree of mixture with SACW below 25 mdepth. These assumptions are based on Aidar et a!.(1993) that considered the 18°C isotherm as thelimit for waters under SACW influence. Salinityranged fi'om 34.98 to 35.52 increasing downward.Dissolved nutrients exhibited increasingconcentrations with depth due to the influence ofthe nutrient rich SACW inbottom layers. Nitratewas the main inorganic nitrogen form, varying &omOto 3.2 flM in CW domain and fi'om 4.10 to 6.30flM in SACW. Ammonium average values were 0.35(I 0.23) flM in CW and 0.61 (IO.20) flM in SACWdomain. Total inorganic nitrogen (TN = N03" +NH/ + NOz")exhibited higher values in transect A,while in the superficial layers (0-15 m) of thetransects B, C and D, concentrations remained below1.0 flM. Phosphate showed similar distributionpattern in all transects with concentrations lowerthan 0.30 flM above 10 m depth, increasing up to0.,83 flM (maximum value) downwards. Thesilicate mean value in the upper layers was 1.84(IO.81) flM wheteas on bottom waters this valuewas 4.42 (I 0.52) flM. Higher silicate concentrationsin upper layers were recorded in transect D. N:Pratios showed low values (0.95 : 1 to 12.29 : 1) on alltransects, even in bottom waters. Such resultsdemonstrate that SSC waters are deficient ininorganic nitrogen forms.

Oil and grease (OG) were detected in allstations of the transect A, where the highest leveIwas obtained (6 mg r\ St. 2, surface). Surfacewaters of stations 6, 7, 14, ]7, 18 and ]9 alsoexhibited some contamination. BOD values werelower than 5 mg rI except for stations 2 and ]5(6 mg rI) and station 16 (14 mg rI). Pheno] andsulfide were not detected in the sampling points.

Zeuwas at approximately ]2 m in transect Aand 11 m in transect D (Table I). The highest depthsof Zeuwere recorded in the central stations of B andC transects (around 30 m). A significant reductionwas detected in stations 6, 15 and 20 generaIlyrelated to the higher total suspended matter (TSM)content in the water column. The TSM distribution

33

exhibited high concentrations at mid waters close tothe margins especially at the insular edge. Thisdistribution seemed to be related to the current action

in sediment suspension. TSM was comprisedbasically by inorganic material but the highest valueswere associated with the increase in the organicfi'action (OSM) that contributed with more than 80%of the bulk, in such cases. This feature is clearlyillustrated in the TSM and OSM distribution profilesin transects A to C (Figs 2 to 4).

Phytoplankton biomass (O.]6 to 6.42 mgChl-a m.3)was similar to the range obtained in otherstudies at SSC (Gianesella-Galvão et ai., 1997; Gaetaet ai., 1990) and in neighboring areas (Aidar et ai.,1993; Zillmann, 1990). Chl-a concentrations tendedto increase downward and its spatial pattern showeda close relationship to the OSM in transects A and D.A large proportion of total Chl-a was in active state,specially in the mid deep layers, suggesting the ceIlswere in a good physiological state or under a lowzooplankton grazing pressure.

The 480/665 nm ratios computed from theabsorbancies of pigment extracts in acetone 90%can be used as an index of nutritional state ofphytoplankton cells (Heath et aI., 1990). Resultslower than 2.0 indicated good conditions intransect A and below 15 m depth in the othertransects in general, while ratios higher than 2.4indicated severe nutritional depletion. Comparingthe profiles of inorganic nitrogen and 480/665 nmratio (Figs 2 to 5), the relation between low nitrogenlevels and phytoplankton cells under nutritionaldepletion can be clearly established.

Total phytoplankton density ranged from11.2 105to 67.3 105cells rI, with the highest valuesobserved close to the edges. Phytoflagellates werethe most abundant group, comprising around 70%of the total number of organisms. Diatoms werethe next most abundant group representing 22 to 27% of the total phytoplankton observed (Fig. 6). Atstations II (mid and bottom waters) and 7 (bottom)diatoms were the dominant group and they were asabundant as flagellates at the surface of stations 9and 14, mid-water ofstations 10,14 and 15, and atstation 6 (bottom).

Qualitatively, 53 phytoplanktonic taxa wereidentified: 43 diatoms, 8 dinoflageIlates, Icyanobacteria (Anabaena sp) and ] silicoflagellate(Dictyocha fibula). This excludes the phytoflageIlategroup and unidentified species. The most importantdiatom species were Leptocylindrus danicus, L.minimus, Dactyliosolen fragilissimus, Skeletonemacostatum and Pseudo-nitzschia sp. DinoflageIlateswere most abundant at station 2 and the morefi'equent genera were Cochlodinium, Gonyaulax,Gymnodinium, Prorocentrum and Protoperidinium.

34 Rev. bras. oceanogr., 47(1), 1999

Temperature'~ C)

2 3Stations

4 5

-5

~10.:::g:15o-20

-25

Inorganic Nitrogen (f..lM)Stations

1 234 5

01'-5

10.sfr15.,o

-20

-25

Oil and Grease (mg/l)Stations4 51

O32

Transect A

Salinity

2 3

Nitrate ( f..lM)Stations

234 5Stations

4 5 1O

-5

Ammonium (f..lM)Stations

12345O

-5

10.sfr15.,o

-20

-25

-5

I -10.:::~ -15--j1o

-20

-25

'-o

Total Chl-a (mg/m3)

2Stations

4 53

-5

I -10.:::~ -15o

-20

-25

-5

10.s%15.,o

-20

-25

Phytoplankton(105 cells/l) St t.a lons

2 345

Fig. 2. Vertical distribution ofthe physicaL chemical and biological variables along the transect A (stations 1 to 5).

Active Chl-a ( mg/m3)Stations

234 5

480/665 nm ratio

Phosphate (f..lM) Silicate (f..lM ) N:P RatioStations Stations Stations

1 2 3 4 5 1 2 3 4 5 1 2 3 4 501 I I I I O'---- 1"\"/

P '----2.0-5 -5 J -5

......10

-1.-='" Ê-lO

.s

i-15 3.0 !-15fr15.,o

-20 -20 . -20

-25 -25 - -25

BOD (mgll) TSM (mg/l) OSM (mg/l)Stations Stations Stations

1 2 3 4 5 1 2 3 4 5 1 2 3 4 501 I I I I 01 I I I I O

GlANESELLA et aI.: Plankton community in São Sebastião Channel 35

Temperature-\{ C)Stations

6 7 8 9 10O

Transect B

Nitrate ( J.tM)Stations6 7 8 9 10

O

Salinity7 8

Stations9 106

O

-5

-10Ê;; -15Q.Q)

o -20

-25

Ammonium (J.tM)Stations

6 7 8 9 10O

-5-5

-10Ê;; -15Q.~ -20

-25

-5

-10Ê;; -15Q.~ -20

-25

~O ~oSilicate (J.tM)

Stations6 7 8 9 10

O

-5

-30 -30

Inorganic Nitrogen (J.tM)Stations

6 7 8 9 10O

Phosphate ( J.tM)Stations

6 7 8 9 10O

-25

-30

Oil and Grease (mgll)Stations

6 7 8 9 10O

-5

~ -10g:5 -15Q.Q)

o -20

BOO (nigll)Stations

6 7 8 9 10O

-5

TSM (mg/I)Stations

6 7 8 9 10O

-25

-30

Total Chl-a (mg/m3 )Stations

6 7 8 9 10

0-p:o-5

-30

Active Chl-a (mg/m3 )Stations

6 7 8 9 10O

-5

480/665 nm ratioStations

6 7 8 9 10O

~-1r j ~-1Oi-15 2: i-15o -20 .5 o -20

~5 ~5

-30 -30 -30

N:P RatioStations

7 8 9 10

-5

-10Ê;; -15Q.Q)o -20

-25

-30

6O

OSM (mgll)Stations

7 8 9 10I A.( '- A40

Phytoplankton(105 cellslI) Stations

6 7 8 9 10O

-5

-25

-30

Fig. 3. Vertical distribution ofthe physical, chemica] and biological variables along the transect B (stations 6 to 10).

36 Rev. bras. oceanogr., 47(1). 1999

Temperature'f C)Stations

11 12 13 14 15O

-5

-10Ê~ -15.J::.

! -20-25

-30

Inorganic Nitrogen ( I-lM)Stations

11 12 13 14 15O

-5

-10

I -15.J::.

i -20CI

-25

-30

Oil and Grease (ml/l)Stations

11 12 13 14 15O

-5

-10Ê~ -15.J::.

i -20CI

-25

-30

T ransect. C

11O

-5

-10

I -15.J::.

i -20CI

-25

-30

SalinityStations

12 13 14 15 11O

-5

-10Ê~ -15.J::.

i -20CI

-25

-30

Nitrate (I-lM )Stations

12 13 14 15

Silicate (I-lM )Stations

11 12 13 14 15O

-5

-10

Ê -15

Phosphate ( I-lM)Stations

11 12 13 14 15O

-5

-10Ê~ -15.J::.

i -20CI

-25

-30

BOO (mg/l)Stations

12 13 14 15, , '---J

'-ÇI.O3.0

11O

-5

-10

I -15.J::.

i -20CI

-25

-30

TSM (mg/l)Stations

12 13 14 15 11O

-5

-10Ê~ -15.J::.

i -20CI

-25

-30

Total Chl-a ( mg/m3)Stations

11 12 13 14 15O

-5

-10Ê~ -15.J::.

i -20CI

-25

-30

0.3

11O

-5

-10

I -15.J::.

i -20CI

-25

-30

N:P RatioStations

12 13 14 15

Active Chl-a ( mg/m3 )Stations

11 12 13 14 15O

-5

-10

I -15.J::.

i -20CI

-25

-30

OSM (mg/l)Stations

12 13 14 15

Phytoplankton(1 cP cells/l) Stations

11 12 13 14 15O

-5

-10Ê~ -15.J::.

i -20CI

-25

-30

Fig. 4. Vertical distribution ofthe physical. chemical and biological variables along the transect C (stations li to 15).

GIANESELLAel ai.: Plankton community in São Sebastião Channel 37

Temperature"f C)Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20~ -25Q

-30-35-40

Transect O

SalinityStations

-19 -18 -17 -16 -20O

-5-10

Ê -15:;; -20~ -25Q

-30-35-40

Phosphate ( IlM )Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20ã.~ -25

-30-35-40

Inorganic Nitrogen ( IlM )Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20õ.~ -25

-30-35-40

Oil and Grease (mg/I)Stations

-20 -19 -18 -17 -160-1 ~.o

-5-10

Ê -15:;; -20~ -25Q

-30-35-40

-20O

-5-10

g-15:5 -20Q.~ -25

-30-35-40

BOD (mg/I)Stations

-19 -18 -17 -16I I I

14.

-20O

-5-10

Ê -155' -20c.~ -25

-30-35-40

Nitrate (IlM )Stations

-19 -18 -17 -16

Silicate ( IlM)Stations

-19 -18 -17 -16

2.

Ammonium (IlM )Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20j -25c

-30-35-40

-20O

-5-10

Ê -15:;; -20ã.~ -25

-30-35-40

N:P RatioStations

-19 -18 -17 -16

OSM (mgll)Stations

-19 -18 -17 -16-20O

-5-10

g -15:5 -20c.~ -25

-30-35-40

TSM (mg/I)Stations

-19 -18 -17 -16 -20O

-5-10

Ê -15:;; -20j -25Q

-30-35-40

Phytoplankton(105 cells/I) Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20~ -25Q

-30-35-40

30

Fig. 5. Vertical distribution ofthe physical, chemical and biological variables along the transect D (stations 16 to 20).

Total Chl-a (mg/m3 )Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20~ -25Q

-30

-35-40

Active Chl-a (mglm3 )Stations

-20 -19 -18 -17 -16O

-5-10

Ê -15:;; -20j -25Q

-30

-35

-40

480/665 nm ratioStations

-19 -18 -17 -16

38 Rev. bras. oceanogr., 47(1), 1999

8 -110 . oala. I

5a

_ DlalomaD Phylollagallalea_ Tolal

3

2

o

8 -110 .ca'a. I

b

7 -1 _ Olha.g.oupa _Dlaloma D phylollagellal.. _ Tolal

e

5

3

2

o

8 -110. cala. I

ce -( I_ OU,a. g.oupa _ Dlaloma D Phylo~lagallalea _ Tolal

5

3

2

o

Fig. 6. Total phytoplankton density (cells rI, represented by the line) and the contributionofthe phytoflagellates, diatoms and other groups (represented by columns) in the20 stations at: a) surface, b) mid water and c) bottom.

GIANESELLAet aI.: Plankton community in São Sebastião Channel 39

Microphytoplankton (considered thefraction above 20 f.lm) showed a predominance ofdiatoms and few dinoflagellates. The mostrepresentative diatom genera were the same foundfor total phytoplankton, including Proboscia alataand Hemiaulus membranaceus. Among thedinoflagellates, Ceratium furca, C. fusus andGonyaulax sp were the most frequent. Thecyanobacteria Anabaena sp was scarcely represented.

Some diatom cells with deformed valves

were observed, in about 20% of the samples, mainlythe species Eucampia comuta, Leptocylindrusdanicus, Nitzschia sp, Proboscia alata andRhizosolenia sp. These cells often seemed to be inpoor physiological conditions (Fig. 7). Such samplescarne from stations located North of the DTCS andgenerally closer to the island side and in variouswater depths: surface (St. 4, 10 and 14), mid waters(St. 1,2,3, 7, 8, 10 and 11) and in bottom waters (St.3, 7 and 9). .

Phytoplankton ecological indices arepresented in Table 2. Transect A showed the highestrichness. Diversity (H) ranged from 1.53 to 3.53 andevenness (J') ranged from 0.46 to 0.77. The highestH' and l' values were found at the stations alongthe channel main axis (St. 3, 4, 7, 8, 13, 17 and 18).Actually, if other groups of organisms, such assmall unidentified centric and pennate diatoms,coccolitophorids and phytoflagellates had beenconsidered for the determination of these indices,values would certainly be improved.

Zooplankton density ranged from 2 103orgsm-3(St. 1) to 27.68 103orgs m-3(St. 6). Low valueswere observed at transect A and in the stations

located in the main channel (St. 8, 13, 18 and 19)where currents are stronger. High biomass valueswere found at stations 6, 7, 9, 11, 15, 16 and 20.These stations are shallower and experience weakcurrent action (Fig. 8).

Species composition was similar at allstations. Copepods were the dominant organismsat 80% of stations and comprised around 50% ofthe total zooplankton. Among the 25 identifiedtaxa, Calanoida comprised 80% of copepod numberat 60% of the stations. Paracalanus quasimodowas the dominant species followed by Temorastylifera, contributing both from 51% to 82% ofthe total copepods. Ao exception to this patternwas found at station 20 where Acartia lilljeborgiand Pseudodiaptomus acutus were the mostimportant species, comprising together 68% of thetotal copepods. Paracalanus crassirostris represented11% of the copepods at station 19 whereasCentropages velificatus 7% at station 17. Lessabundant species were Clausocalanus furcatus,Ctenocalanus vanus, Ctenocalanus sp,

Nannocalanus minor,Calocalanus styliremis,Calanopia americana, inorder.

EucalanusLabidocera

a decreasing

pileatus,jluviatilis,importance

Fig. 7. Deformed va\ves observed in someRhizosolenia sp cells.

40 Rev. bras. oceanogr., 47(1), 1999

Table 2. Ecological indices computed for phytoplanktonidentified species at the 20 sampling stations inSão Sebastião Channel (spring/9l).

STATION DENSITY

(cellsl")

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

2,267,265

2,987,985

2,319,818

1,816,815

1,726,725

1,696,695

2,064,563

1,524,023

2,192,190

1,861 ,860

2,102,100

1,861,860

900,900

1,629,128

1,861,860

2,417,415

1,433,933

840,84

1,148,708

1,178,678

IIIClINESS DIVERSITY

(5) (H')

Organisms / L

30

25

20

15

10

5

o

15

19

24

22

20

16

11

19

16

10

16

11

17

10

13

16

17

17

12

9

2.15

2.84

3.53

3.09

2.91

2.80

2.64

3.02

2.49

1.53

2.39

2.29

3.00

2.37

2.19

2.13

3.02

3.06

2.41

2.40

H'MAX

(109,5)

3.91

4.25

4.58

4.46

4.32

4.00

3.46

4.25

4.00

3.32

4.00

3.46

4.09

3.32

3.70

4.00

4.09

4.09

3.58

3.17

EVENNESS

(J')

The second most abundant group wasCyclopoida (5 up to 30% of the total copepods),being Corycaeus f{iesbrechti the second mostimportant species (in terms of number andfTequency),reaching 30% of copepods at station 11.Corycaeus amazonicus and Oithona hebes exhibitedmaximum contribution around 7% of the total

copepods while Oithona plumifera and o. nana,Oncaea curta, o. media and o. venusta fulfilledaround 2.5 %.

The Suborder Harpacticoida was lessimportant in terms of number and fTequency. Itsgreatest contribution was at stations 19 and 20 with17% and 14% respectively, given mainly byEuterpina acuttfrons. Microsetella norvef{ica andClytemnestra rostrata were also present.

C1adocerans and appendicularians weremore abundant and fTequent along the channelmain axis, performing a total of 14% (St. 10) up to45% (St. 2) of total zooplankton. Echinoderms,chaetognaths, fish larvae and annelids were fTequentbut not abundant.

Ecological indices computed for Copepodare presented in Table 3. Richness values rangedfTom 6 to 15. The lowest values were found next

the DTCS (St. 11 to 13 and 20) while the highestrichness was found at stations 2 to 5 and 15.Diversity ranged fTom1.15 to 2.47. ln a general way,low diversity was found at the stations close to the oil

0.55

0.67

0.77

0.69

0.67

0.70

0.76

0.71

0.62

0.46

0.60

0.66

0.73

0.71

0.59

0.53

0.74

0.75

0.67

0.76

_ other groups, _ copepods I/I total

2 3 4 5I

6 7 8 9 101

11 12 13 14 151

16 17 18 19 20A B C D Stations

Fig. 8. Total zooplankton density (org tI) and the contribution ofthe Copepods relatedto the other groups, in the 20 stations.

GIANESELLAet ai.: Plankton community in São Sebastião Channel 41

Table 3. Ecological indices computed for the identified Copepoda at the 20 sampling stationsin São Sebastião Channel (spring/91).

terminal (stations 6, 11 and 12), Northwards (St. 8,9, 10) and at station 18. Evenness ranged iTom0.36to 0.74 (St. 19) with the lowest values detected at thesame stations of low diversity. ln such cases, thedominant species was always Paracalanusquasimodo, sometimes followed by Corycaeusgiesbrechti.

The three first components of PCA analysisexplained 64% oftotal variance. The first component(42% explanation) was positively correlated tosalinity, nutrients and chlorophyll (total and active)and negatively correlated to temperature and 480/665nm ratio (Fig. 9a). This component can beinterpreted as the SACW influence on nutrientcontent over phytoplankton biomass development.Sampling points positively projected in axis I wererelated to battom or mid water samples with highnutrient content, low temperature and low 480/665nm ratio. Such points represent the best nutritionalphytoplankton growth conditions in deeper stations,which show higher nutrient availability due to themixture between CW and SACW. Points located in

the negative side ofaxis I were generally related tosurface and mid (and sometimes battom) waters ofshallower stations that are characterized by lownutrients, low chlorophyll-a and high 480/665 nmratio indicating nutritional deficiency.

Gil and grease concentrations andphytoplankton counts defined the second component(12.11% explanation) at the positive side and totalsuspended matter (basically the organic iTaction) atthe negative side. This component can be interpreted

as the current action revolving and transportingsediments in the channel against regions of lowcurrent intensity favoring the maintenance or the lowdispersion of oil and grease spots.

The third component (9.88% total varianceexplanation) is defined by phytoplankton biomass(number of cells and Chl-a) and oil and grease (Fig.9b). ln opposition to these variables are the 480/665nm ratios and ammonium. This feature indicates that

higher phytoplankton biomass is related to goodnutritional state represented by low 480/665 nmratio. In this way, the third component seems toreflect the physiological status of the phytoplanktoncommunity. Sampling points located at the positiveside represent phytoplankton in healthy conditionwhile those in the negative one represent nutrientdeficient cells.

Discussion

SSC waters are the result of the mixingamong CW, SACW and TW, which are present invariable proportions over the continental shelf(Castro Filho, 1990; Miranda, 1982). The presenceof water with the characteristics of SACW in thechannel bottom layers is a common feature since thiswater mass reaches the channel through the deepestsouthern entrance when it floods the innercontinental shelf This phenomenon is more commonduring spring and summer due to the wind pattern(Castro Filho, op. cit.).

STATION TOTAl COPEPOD RICHNESS DIVERSITY H'MAX EVENNESSZOOPLANKTON DENSITY (S) (H') (Log2S) (J')

(ORGS L") (ORGS L")

1 2,000 1,200 8 1.81 3.00 0.60

2 5,824 2,368 12 2.43 3.58 0.68

3 3,708 1,375 13 2.10 3.70 0.57

4 4,549 1,610 15 2.18 3.91 0.56

5 4,316 1,716 13 1.98 3.70 0.54

6 27,680 18,440 11 1.45 3.46 0.42

7 10,960 5,904 11 2.06 3.46 0.60

8 4,750 2,792 11 1.64 3.46 0.47

9 13,646 9,838 11 1.25 3.46 0.36

10 9,180 7,560 9 1.15 3.17 0.36

11 12,420 8,280 6 1.29 2.58 0.50

12 8,544 5,909 9 1.46 3.17 0.46

13 2,646 1,601 7 1.95 2.81 0.70

14 5,387 3,286 11 2.11 3.46 0.61

15 10,540 6,380 14 2.11 3.81 0.56

16 11,361 7,281 10 1.93 3.32 0.58

17 8,957 5,352 12 1.83 3.58 0.51

18 2,560 1,322 12 1.31 3.58 0.37

19 5,760 3,008 10 2.47 3.32 0.74

20 13,038 8,238 9 2.02 3.17 0.64

42 Rev. bras. oceanogr., 47(1),1999

Axis 113(12.11%)

-1

-2

-3

-4

-5--4

4

Ax is 11I

t'9.88%)

-1

-2

-3-4

2'

11025 o

o OG

A31'

o

41'o

J.31' J.81'o o

J.O

J.

B

6

0131' J.8t"o

0-S 10

3"o

o

7s

o o Bs9s

ISMo19f

Fig. 9. Principal component analysis (PCA): representation of the covariables and samples inthe factorial plane I-lI (a), and in the factorial plane I-lIl (b).

151o "

17"0

-2

Axis I (42.03%)

2 4

20Mo

p~o 5"o

3

4

55o 51'

o

2Iso

4Mo

J.3...

o

o

N02I

:p 19 l'~4fO

°18...Sal °171'

NOJN04

9s .D75o'-'7m

105 14m 9m,.Q,0135O °

8s"11m010m

-2 o 2

Axis I (42.03%)

GIANESELLAet aI.: Plankton community in São Sebastião Channel 43

Despite the existence of a domesticsewage submarine outfall at Ponta do Araçá,South of the studied area (Lat. 23°49'1O"S - Long.45°24' 14"W), there was no indication ofeutrophication effects at the channel main stream,probably due to the strong currents, which allow ahigh dispersion (Soares, 1994). Nutrientconcentrations were typical for waters under CW andSACW III (sense, Aidar et ai., 1993) domain.Indeed, a great portion ofthe effluent is brought backto the Baía do Araçá (Lima, 1998) leading to a localeutrophication.

Considering that SSC is surrounded bybeaches, its waters constitute a primary contact waterthat implies that oil, grease, sulfides and phenolsshould be virtually absent and BOD values should belower than 5 mg rI (CONAMA, 1986). Resultsindicated oil and grease contamination in half ofsampled station and BOD values above theacceptable limit in three points. Contamination wasmore tTequent in surface and mid waters andespecially in transects A and D, not suggesting adirect relation to DTCS origino

Rapport (1992) refers to several symptomsthat should be considered in the assessment of anaquatic ecosystem. Alterations in biotic communitystructure favoring smaller forms; reduced speciesdiversity, increased dominance by exotic or "r"selected species; shortened food chain length;increased disease prevalence and reduced populationstability, are some examples.

Data obtained in the present work showedthat the plankton community was similar in terms ofbiomass, density and diversity to oligo-mesotrophicenvironments of the Ubatuba region (Aidar et at.,1993; Zilmmann, 1990; Vega-Pérez, 1993) and theSão Sebastião inner continental shelf (Gianesella-Galvão et ai., 1997). No significant differences inbiomass and species composition tTomthose reportedby Gaeta et aI. (1990) in the southern part of SSCwere found. .

Phytoplankton diversity (H) and evenness(r) indices were high, especially at the stationslocated in the main channel. This can be ascribed to

the variability of microenvironments, by the presenceof CW and SACW along the water column. Lowervalues of H were observed at the margins dominatedby CW and under low turbulence (Soares, 1994)which also favors low species diversity (Margalef,1967).

Abnormal diatom cells were found at thestations located to the North of the oil terminal; atthese same stations oil and grease were also detected,but it is insufficient to state that hydrocarbons or anyassociated substance could be a stress factor.However, no phytoplankton cells abnormalities were

previously reported in this region. Although thepreservation of the samples have been doneaccording to the routine method used inphytoplankton studies and the small storage time, thepossibility of those deformities be related to technicalartifacts should not be excluded. Otherwise,Gianesella-Galvão (1982) observed morphologicalalterations in S. costatum and L. danicus in the Bayof Santos (SP), concomitant to the presence ofmercury in the water. Hence, the phytoplanktonmorphology should be carefully examined in futuremonitoring in the area, considering "in vivo"observations of the cells in order to excIude the

hypothesis of technical artifacts due to preservationofthe samples and to identifYany abnormality in thecells that could be caused by environmentalcontamination.

The observed spatial differences inzooplankton abundance did not show correlationwith water masses. Copepod dominance in coastalwaters is a common feature (Bjõrnberg, 1981), asreported previously for the southern part of SSC byGaeta et aI. (1990), for São Sebastião innercontinental shelf by Gianesella-Galvão et aI. (1997)and for Ubatuba region by Vega-Pérez (1993). Themost abundant species of copepods, cIadocerans andappendicularians were the same reported by theseauthors.

In spite of the occurrence of colder waters atthe deeper stations (3, 4, 8, 13 and 18), no typicalcold waters species were found. Paracalanusquasimodo and Temora stylifera, the most tTequentspecies, are susceptible to sewage pollution(EPOPEM, 1979). Indeed, significant decrease intheir population occurred at station 20, but thestudied physical and chemical parameters could notexplain such observation.

ln the last decades, studies havedemonstrated that different zooplanktonic speciescan change their feeding behavior as a function ofthe quality and quantity of the available foad. Thereare many evidences that a great number ofomnivorous groups can display severaI degrees ofplasticity between carnivory and herbivory(Paffenhõfer, 1988; Kleppel, 1993). Considering thefeeding behavior, the zooplankton community in thestudied portion of SSC can be characterized as - (1)

Omnivorous and primarily herbivorous: Paracalanusquasimodo, P. crassirostris, Temora stylifera,Acartia lilljborgi (Tumer, 1984a, b; Tumer, 1987;Gifford & Dagg, 1988); (2) Omnivorous andprimarily camivorous: Eucalanus pileatus (Verity &Patfenhõfer, 1996); (3) Omnivorous and primarilyraptorial, feeding animaIs and large phytoplanktoncells: Corycaeus giesbrechti, C. amazonicus andCentropages velificatus (Tumer, op. cit.); (4) Filter

44 Rev. bras. oceanogr., 47(1),1999

feeders of pico and nanoplankton: cladocerans andappendicullarians (Alldredge, 1981, Bedo et ai.,1993); (5) Camivorous: Labidocera fluviatilis,Calanopia americana, and the chaetognaths,cnidarians and cirripedians (Paffenhõfer, 1988).

The low computed H' values seem to reflectthe competition among copepods species since thegreatest part of them have the same feeding behaviorand the phytoplankton biomass is not abundant. TheCopepod dominance in the majority of stations wasindicated by low l' values.

Although some fluctuations in the structureof phytoplankton and zooplankton have been shownamong the stations by the diversity and evennessindices, these parameters failed to indicate anydiscontinuity in the area that could be attributed to astress factor. These fluctuations seem to be primarilyrelated to the physical structure of the environment.In spite of the fact that the studied variables havepointed out a healthy ecosystem condition,morphological abnonnalities found in somephytoplanktonic organisms may suggest the presenceof stress factors. There may be a number of otherfactors, detectable or not, to be further considered inaddition to those we have studied. As oil and greasewere found in half of the sampled stations, thesecontaminants or any associated substance could beacting as stress agent.

Aidar et ai. (submitted) tested the effects ofthe effiuent to be discharged by DTCS into thechanneI, in Skeletonema costatum bioassays. Theyverified that this effiuent might be extremely toxic,since the ECso was obtained in the range ITom0.18to 0.30 % of effiuent concentration after 48 and 96 hrespectively. Similar results were obtained inbioassays carried out by Souza & Tommasi (1997)with the gastropod Costoanachis sertulariarum andby Phan et ai. (1994) with the mysid Promysisatlantica. These studies showed clearly the highdegree of injury that this effiuent disposal is able tocause to the system if it will not be processed in avery controlled way, and also indicate the importanceof continuous monitoring to evaluate possiblealterations induced by this anomalous source.

The identification of stress conditions in theenvironment is crucial to the establishment of a

proper system-management. Thus, the importance ofdeveloping studies on environmental diagnosisparallel to toxicological bioassays is undeniable

Conclusions

ln spite of the single sampling periodperformed for the present study do not allowinferences on the natural variability of the system,

the results here obtained, during a spring condition,indicated that the environment around the DTCSarea did not differ ITom adjacent areas under loweranthropogenic pressure. The nutrient concentrationsand phytoplankton biomass observed were in therange of coastal oligo-mesotrophic areas. Thestatistical analyses failed to indicate that oil andgrease were impacting phytoplankton community. Inaddition, the examined indices of the bioticcommunity structure showed no indication of stress,since the community displayed high diversity indicesand zooplankton community comprised individuaIsof various feeding behaviors affording many trophicinteractions.

Acknowledgments

We thank PETROBRÁS (Petróleo BrasileiroS/A) and FUNDESPA (Fundação de Estudos ePesquisas Aquáticas) for the allowance of datapublication. We also thank the valuable comments ofthe two anonymous referees.

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(Manuscript received 19 August 1998; revised15 December 1998; accepted 29 April1999)