a S c i T e c h n o l j o u r n a lResearch Article

Karthik et al., J Mar Biol Oceanogr 2012, 1:2http://dx.doi.org/10.4172/2324-8661.1000102

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Phytoplankton Abundance and Diversity in the Coastal Waters of Port Blair, South Andaman Island in Relation to Environmental VariablesKarthik R1*, Arun Kumar M1, Sai Elangovan S1, Siva Sankar R2 and Padmavati G1

AbstractThe distribution and diversity of phytoplankton was studied in the coastal waters of south Andaman Sea during Sept 2011 to Mar 2012. A total of 227 species belonging to 67 genera were recorded in this study. Diatoms made larger contribution to the total abundance (68%) followed in order by Cyanophyceae (24%) and Dinoflagellates (8%). Silicoflagellates were numerically less (0.4%). Diatoms were represented by 164 species belonging to 46 genera, Dinoflagellates were represented by 58 species belonging to 16 genera, Cyanophyceae and Silicoflagellates comprised 2 genera each. Bacteriastrum hyalinum, Coscinodiscus granii, Eucampia zoodiacus, Leptocylindrus danicus, Nitzschia closterium, Odentella sinensis, O. mobiliensis, Pleruosigma affine, Rhizosilenia alata, R. imbricata, Prorocentrum micans, Protoperidinium depressum, Asterionella glacialis, Guinardia striata, Licmophora gracilis, Pleurosigma angulatum, Skeletonema costatum and Thalassionema nitzschioides were the most prevalent diatoms and dinoflagellates encountered in the samples. The population density of phytoplankton ranged from 0.4 × 105 to 4.2 × 105 cells L-1. Higher population density and chlorophyll a was observed in Sept, Dec and Mar at St. 2 due to the periodic bloom of diatoms such as Coscinodiscus centralis (95000 cells ml-1), Rhizosolenia imbricata (19000 cells ml-1) and R. alata (9500 cells ml-1). Relatively higher species diversity (H’= 3.6) and equitability in plankton flora (J=0.9) was observed at St. 4 with lower levels of anthropogenic activity (e.g. Carbyn’s Cove, BOD=2.7mg L-1). Predominance of the red tide species (blue-green algae), Trichodesmium erythraeaeum (27000 cells ml-1) at St. 3 during March lead to an almost monospecific population was observed during the present investigation.

Keywords: Phytoplankton; Diatom bloom; Coastal waters; South Andaman sea

IntroductionPhytoplanktons are key organisms in aquatic ecosystems. They

initiate the marine food chain, by serving as food to primary consumers [1,2]. About 90% of the total production in marine ecosystem is contributed by the phytoplankters that support commercial fisheries.

*Corresponding author: Karthik R, Department of Ocean Studies and Marine Biology, Pondicherry University, Port Blair - 744 112, Andaman, India, E-mail: rkarthicas@gmail.com

Received: September 13, 2012 Accepted: December 07, 2012 Published: December 14, 2012

The effects of environmental factors on plankton dynamics has been investigated by several authors [3-5]. The influence of various factors on the seasonal growth and abundance of phytoplankton differs significantly, with physical (such as temperature and light intensity) and chemical factors (dissolved oxygen, pH, salinity, total hardness, electrical conductivity and nutrient level) as primary limiting factors reported in many regions of the world [6]. Literatures on the influence of environmental variables on phytoplankton communities in coastal waters around Andaman Islands are meagre. In view of the importance and scarcity of reports from this area, an investigation was carried out on a monthly interval during Sep 2011 to Mar 2012 in the coastal waters of south Andaman to assess the seasonal variability in phytoplankton community structure and related physicochemical water quality parameters. The present communication also documents the occurrence of periodic diatom blooms in the coastal waters of south Andaman.

Materials and MethodsPhytoplankton sampling and analysis

This phytoplankton study was conducted during Sep 2011 to Mar 2012 in two distinct areas including: (1) areas with more anthropogenic activity (i.e. fishing harbor, fish landing centre and fishing community (Stations 1 and 2); and (2) areas with lower levels of anthropogenic activity (Stations 3 and 4) (Figure 1). Physicochemical water quality parameters such as seawater temperature, salinity and dissolved oxygen were recorded at each station. Salinity (ppt) was measured with a hand held Refractometer (ATAGO). Dissolved oxygen (mg/L) was estimated by the modified Winkler’s method while phytoplankton biomass was estimated as chlorophyll a (µg/L) (90% acetone method) measured spectrophotometrically in the laboratory [7]. Nutrients [nitrate, silicate and phosphate (µmol/L)] were also measured during the study [7]. For phytoplankton studies, samples were collected in 1 liter labeled plastic containers by filtering 50 L of water, using a phytoplankton net (20 µm) and immediately preserved

Figure 1: The study area and location of the sampling sites.

Citation: Karthik R, Arun Kumar M, Sai Elangovan S, Siva Sankar R, Padmavati G (2012) Phytoplankton Abundance and Diversity in the Coastal Waters of Port Blair, South Andaman Island in Relation to Environmental Variables. J Mar Biol Oceanogr 1:2.

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with 4% formalin and fixed with Lugol’s iodine for quantitative and qualitative analysis. The samples were left to settle for 24 hrs and concentrated to 10 ml by siphoning out the supernatant. In the laboratory, for phytoplankton taxonomy studies, 1 ml sample was taken from concentrated sample by using a Sedgwick-Rafter counting chamber and examined under the plankton inverted microscope. The total numbers of phytoplankton present in a liter of samples were calculated according to the following equation:

n v 1000

NV×

= ×

Where N is the total number of phytoplankton cells per liter of water filtered, n is an average number of phytoplankton cells in 1ml of sample, v is the volume of phytoplankton concentrates, V is the volume of total water filtered.

Statistical analysis

Statistical analysis was performed by using statistical software Primer (Ver. 5). Two-way analysis of variance (ANOVA) was employed and the level of significance was used to define statistically significant differences. Biodiversity indices (species richness, diversity and equitability) were calculated in the phytoplankton population using monthly intervals between samples and cluster analysis to discern species similarities between different sampling stations.

ResultsPhysicochemical parameters

Variations in temperature, salinity and dissolved oxygen among stations and sampling dates are shown in table 1. During the study period, water temperature varied from 25-28°C. The high temperature (28°C) was recorded during Oct 2011 at all stations. Salinity ranged from 30 to 34% and it was highest during Oct and Dec at all stations. Both water temperatures and salinities were generally low during the monsoon period during Sept. Dissolved oxygen varied from 3.2 mg/l-4.5 mg/l throughout the study at all sites. Maximum values (4.5 mg/l) were recorded during Dec 2011 at Stations 1 and 4 and minimum during Sept at St. 2 (3.2 mg/l), which was due in a large part to the

occurrence of the diatom bloom of Coscinodiscus centralism. Higher dissolved oxygen and lower salinity at St. 1 and St. 3 during Sep and Nov were due in part to influx of fresh water from precipitation and seepage and runoff of fresh water from the land.

Nutrients

The concentrations of nitrate (NO3), phosphate (PO4) and silicate (SiO4) showed pronounced spatial and temporal variation during the present investigation (Table 2). The nitrate content varied between 0.1 umol l-1 in Oct and 5.61 umol l-1 in Sept. Silicate concentrations remained much higher than nitrate and phosphate levels, ranging from 3 umol l-1 in Sept to 14-15 umol l-1 in Dec and Mar. Phosphate fluctuated between 0.1 umol l-1 in Feb and 0.6 µmol l-1 in Sept. The relative amount of nitrate-silicate and nitrate-phosphate ratio was higher during periods of algal blooms.

Chlorophyll a concentrations varied from 0.01-0.16 µg l-1 (Table 3). Higher values of Chlorophyll a (0.16 µg l-1) was recorded during Sep, Dec and Mar at St. 2 due to bloom forming diatoms such as Coscinodiscus centralis, Rhizosolenia alata and Rhizosolenia imbricate followed by 0.14 µg l-1 during Mar which was due to blue-green algae Trichodesmium erythraeum at St. 3.

Population density and distribution

The overall mean phytoplankton abundance was higher (p<0.05) at St. 3 compared to other stations in the study area (Figure 2). Minimum densities were recorded at St. 4. Monthly and station wise variations of phytoplankton densities are clearly depicted in table 4. Well marked monthly variations were observed in population densities of phytoplankton. The lowest densities (215 and 261 cells/ml) were observed in the month of Nov at Stations 1 and 2, whereas the highest population density (95000 cells/ml) was observed during Sep at St. 2 due to the dense aggregation of Coscinodiscus centralis cells (95000 cells/ml) followed by high densities (27000 cells/ml) during Mar at St. 3 due to blue-green algae Trichodesmium erythraeum when temperature salinity and dissolved oxygen were recorded low and nutrients such as nitrate, silicate and phosphate were high. Population density was quite low at St. 4 during the study period.

Month IntervalsTemperature (ºC) Salinity (%) Dissolved oxygen (ml/l)

S1 S2 S3 S4 S1 S2 S3 S4 S1 S2 S3 S4Sep’11 28 25 25 27 31 32 31 30 3.6 3.2 4.2 4.4

Oct 27 28 28 28 33 34 32 32 4.0 3.5 4.3 4.3Nov 25 28 25 26 31 32 30 32 4.3 3.9 4.1 4.1Dec 26 25 27 26 33 34 32 32 4.5 3.9 3.9 4.5Jan 28 28 26 25 32 32 32 30 4.4 4.1 4.2 3.7Feb 25 26 27 25.5 32 31 30 30 4.6 4.5 3.5 4.5

Mar’12 26 26 26.7 26 31 33 31 30 4.1 4.2 3.8 3.7

Table 1: Variations in physico-chemical water quality parameters during September 2011 to March 2012 in the study area.

Month IntervalsNitrate (μmol l-1) Silicate (μmol l-1) Phosphate (μmol l-1)

S1 S2 S3 S4 S1 S2 S3 S4 S1 S2 S3 S4Sep’11 0.5 5.6 0.2 0.2 11 13 3 4 0.3 0.6 0.3 0.3

Oct 0.3 0.2 0.1 0.1 4 4 4 4 0.5 0.5 0.4 0.3Nov 0.8 0.9 0.1 0.8 4 5 5 4 0.3 0.5 0.4 0.4Dec 3.4 3.8 0.4 0.4 14 14 4 4 0.3 0.6 0.1 0.2Jan 1.0 1.1 0.8 0.9 7 6 6 6 0.3 0.4 0.2 0.3Feb 1.2 1.2 0.2 1.1 6 6 5 6 0.0 0.1 0.0 0.1

Mar’12 3.7 4.3 4.1 0.8 10 14 15 5 0.3 0.4 0.4 0.1

Table 2: Variations in nutrient concentration during September 2011 to March 2012 in the study area.

Citation: Karthik R, Arun Kumar M, Sai Elangovan S, Siva Sankar R, Padmavati G (2012) Phytoplankton Abundance and Diversity in the Coastal Waters of Port Blair, South Andaman Island in Relation to Environmental Variables. J Mar Biol Oceanogr 1:2.

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doi:http://dx.doi.org/10.4172/2324-8661.1000102

Species composition

Phytoplankton identified at all stations comprised a total of 225 species (161 Diatoms, 58 Dinoflagellates, 4 Cyanobacteria and 2 Silicoflagellates species (Table 5). Diatoms formed the most dominant taxa and contributed to the total population at almost all the stations (Figure 3). The massive bloom of Coscinodiscus centralis at St. 2 (95000 cells/ml) during Sept was found to be the most abundant species in the study area. It caused blooms with high relative abundances (99.9%) which lead to a monospecific population at some sites. Blue green algae Trichodesmium erythraeaeum was predominant at St. 3 during Mar and contributed 92% of the total population. Dinoflagellates were generally more dominant only at St. 4 and St. 1 and contributed 24% and 4% of the population, respectively. Silicoflagellates occurred in very low abundances and contributed <1% to the total population.

The diatom flora comprised of 53 centrales and 53 pennales. Between the two groups of diatoms, centrics were predominated pennates during the entire study period. Among the centrales, 4 families such as, Coscinodiscaceae, Leptocylindraceae, Chaetocerotaceae, and Rhizosoleniaceae were found floristically richer than the others while in the case of pennales, 4 families, such as Pleurosigmataceae,

Licmophoraceae, Naviculaceae and Fragilariaceae dominated the diatom community. Among diatoms Coscinodiscus centralis, C. granii, Pleurosigma affine, Leptocylindrus danicus, Bacteriastrum furcatum, B. hyalinum, Rhizosoleniaalata, R. imbricate, Guinardia steriata, G. flaccid, Chaetoceros decipiens were found to be dominant. Similarly, the dinoflagellate community was dominated by Ceratium furca, Prorocentrum micans and Protoperidinium depressum (Table 6).

Species diversity

The number of species (S) and range of diversity indices in the study area are shown in table 7. Marked seasonal variation was noticed in species diversity in the present investigation. The maximum number of species (68) was observed at stations St. 1, followed by 51 at St. 4 in Mar while minimum numbers were observed at stations 1 (15) and 3 (18) during Nov. The lowest species diversity (H’=0.01 to 0.09) and evenness (J=0.01 to 0.04) values were observed during Sept, Dec and Mar at St. 2 and during Mar at St. 3.

Two separate assemblages of species were observed (Figure 4). The bloom-forming species at Stations 2 and 3 formed one cluster and species in Stations 1 and 4 formed a separate cluster, where dinoflagellates were more dominant.

DiscussionPopulation density and chlorophyll a did not show any significant

correlation at St. 2 and St. 3 (p>0.05) whereas, chlorophyll a and nutrients discerned a positive correlation (p<0.05) at almost all the station. During the bloom period (diatoms & blue-green algae) both temperature and salinity were low and concentrations of nutrients (nitrate, silicate and phosphate) were high. This nutrient rich water could be due to the precipitation during monsoon (September), the cyclone “Thane” (Dec 2011) and the run-off of urban and domestic wastes from land into the coastal waters might that may have influenced the abundance of phytoplankton in this area. Nutrient levels, particularly of silicate and nitrate reduced to minimum levels that coincided with the decline of Coscinodiscus centralis, R. imbricate and Rhizosolenia alata cell densities. The low phytoplankton growth at Stations 1 and 3 during Nov could be due to low temperature, salinity and poor nutrient levels which were not optimal for growth. The overall mean phytoplankton abundance was higher at St. 3 and minimum at St. 4 may be due in part to the grazing pressure by zooplankton.

Month IntervalsChlorophyll a (μgl-1)

S1 S2 S3 S4Sep’11 0.5 5.6 0.2 0.2

Oct 0.3 0.2 0.1 0.1Nov 0.8 0.9 0.1 0.8Dec 3.4 3.8 0.4 0.4Jan 1.0 1.1 0.8 0.9Feb 1.2 1.2 0.2 1.1

Mar’12 3.7 4.3 4.1 0.8

Table 3: Variations in chlorophyll a concentration during September 2011 to March 2012 in the study area.

Month IntervalsPhytoplankton density (No.l-1)

S1 S2 S3 S4Sep’11 635 9512 643 552

Oct 408 450 254 278Nov 549 630 215 261Dec 8862 9633 301 302Jan 550 610 341 330Feb 663 716 412 348

Mar’12 963 1911 27111 852

Table 4: Variations in population density during September 2011 to March 2012 in the study.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

S1 S2 S3 S4

Tota

l cel

ls 1

03 .l-1

Figure 2: Mean abundance of phytoplankton during September, 2011 to January, 2012 in the study area.

Diatom 73%

Dinoflagellates 24%

Cyanophyceae 2%

Silicoflagelates 1%

S4

Diatom 94%

Dinoflagellates 4%

Cyanophyceae 1%

Silicoflagellates 1%

S1

Diatom 100%

Dinoflagellates 0% Cyanophyceae

0% Silicoflagelates 0%

Diatom 7% Dinoflagellates

1%

Cyanophyceae 92%

Silicoflagelates 0%

S3

S2

S3

Figure 3: Percentage composition of phytoplankton in the study area.

Citation: Karthik R, Arun Kumar M, Sai Elangovan S, Siva Sankar R, Padmavati G (2012) Phytoplankton Abundance and Diversity in the Coastal Waters of Port Blair, South Andaman Island in Relation to Environmental Variables. J Mar Biol Oceanogr 1:2.

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Dinophyceae (Dinoflagellates)

Alexandrium catenella Dinophysis rotundataAlexandrium minutum Dinophysis triposAlexandrium tamarense Gonyaulax conjunctaCeratium candelabrum Gonyaulax polygrammaCeratium declinatum Gonyaulax spiniferaCeratium dens Gymnodinium catenatumCeratium extensum Lingulodinium polyedrumCeratium furca Noctiluca scintillansCeratium fusus Ornithocercus magnificusCeratium horridum Oxtoxum scolopaxCeratium lineatum Peridinium leonisCeratium lunula Podolampas palmipesCeratium macroceros Prorocentrum balticumCeratium massiliense Prorocentrum limaCeratium trichoceros Prorocentrum micansCeratium tripos Prorocentrum obtusumCochlodinium polykrikoides Protoperidinium balticumCochlodinium sp Protoperidinium brevipesDinophysis acuta Protoperidinium claudicansDinophysis caudate Protoperidinium conicoidesDinophysis dens Protoperidinium conicumDinophysis nules Protoperidinium denticulatumDinophysis ovum Protoperidinium depressumProtoperidinium divergens Protoperidinium obtusumProtoperidinium excentricum Protoperidinium ovumProtoperidinium grande Protoperidinium pellucidumProtoperidinium leonis Protoperidinium pentagonumProtoperidiniumpyriforme Pyrodiniumbahamense Pyrophacushorologium Pyrophacusstinii Cyanophyceae (Blue-greens)LyngbyaspOscillatorriaspTrichodesmiumerythraeumSynechococcusspDictyochophyceae (silicoflagellates)Dictyocha fibulaDictyochastaurodon

Table 5: List of phytoplankton species recorded at each station.

The results of the present study shows almost a two fold increase in the species composition of phytoplankton taxa compared to an earlier report [8] from the oceanic region of this area. This earlier investigation [8] reported 143 phytoplankton species from Andaman and Nicobar region of the Bay of Bengal. Similarly, Siva Sankar and Padmavati [9] reported only 65 species from this region with phytoplankton levels that were low in comparison with the species number measured in this study. Geetha and Kondalarao [10] have similarly reported 249 species from coastal waters of Bay of Bengal, which is higher than this study and ascertained their oceanic preference. This kind of variations could be attributed to differences in ecological distribution in the types of organisms as well as climatic, geographic and temporal differences between these two studies.

Bacillariophyceae (Diatoms)

Amphaora salina Cymbella cistula Navicula follis

Amphiphora paludosa Cymbella sp Navicula granulate

Amphora acuta Dactyliosolen fragilissima Navicula inornata

Amphora ostrearia Dactyliosolen phuketensis Navicula lata

Amphora ovalis Diploneis crabro Navicula lawissima

Amphora plicata Ditylum brightwellii Navicula lridis

Amphora robusta Eucampia antarctica Navicula lyra

Asterionella formosa Eucampia cornuta Navicula pungens

Asterionellopsis glacialis Eucampia zoodiacus Navicula serians

Bacillaria paradoxa Guinardia blavyanus Navicula solaris

Bacillaria paxillifera Guinardia delicatula Navicula splendida

Bacteriastrum comosum Guinardia flaccida Nitrschia pungens

Bacteriastrum delicatulum Guinardia striata Nitzachia vitrea

Bacteriastrum furcatum Gyrosigma balticum Nitzschia acicularis

Bacteriastrum hyalinum Gyrosigma diminutum Nitzschia angustata

Biddulphia alternans Gyrosigma fasciola Nitzschia apiculata

Chaetoceros aequatorialis Hemialu shauckii Nitzschia closterium

Chaetoceros atlanticus Hemialus membranaceus Nitzschia frustulum

Chaetoceros coarctatus Hemialus sinensis Nitzschia gracilis

Chaetoceros constrictus Hemiaulus indicus Nitzschia longissima

Chaetoceros curvisetus Hemidiscus cuneiformis Nitzschia panduriformis

Chaetoceros decipiens Hemidiscus hardmannianus Nitzschia paradoxa

Chaetoceros didymus Leptocylindrus danicus Nitzschia rectilonga

Chaetoceros diversus Leptocylindrus minimus Nitzschia sigma

Chaetoceros eibenii Licmophora communis Nitzschia spathulata

Chaetoceros lorenzianus Licmophora ehrenbergii Odentella sinensis

Chaetoceros messanensis Licmophora gracilis Odontella mobiliensis

Chaetoceros neglectus Licmophora nebecula Pleurosigma acapense

Chaetoceros orientalis Licmophora paradoxa Pleurosigma affine

Chaetoceros peruvianus Licmophora remulus Pleurosigma spencerii

Chaetoceros pseudocurvisetus Licmopho ratincta Pleurosigma angulatum

Chaetoceros wighamii Mastogloia apiculata Pleurosigma attenuatum

Climacosphenia elongata Mastogloia erythraea Pleurosigma cuspidatum

Cocconeiss cutellum Mastogloia smithii Pleurosigma directum

Coscinodiscus asteromphalus Melosira cf.spaerica Pleurosigma distortum

Coscinodiscus centralis Melosira dubia Pleurosigma elongatum

Coscinodiscus granii Melosira nummuloides Pleurosigma fasciola

Coscinodiscus stellaris Meuniera membranacea Pleurosigma formosum

Coscinodiscus thorii Navicula crucicula Pleurosigma hippocsmpus

Cylindrotheca closterium Navicula delicatula Pleurosigma macrum

Cylindrotheca gigas Rhizosolenia polydactyla Synedra barbatula

Pleurosigma obscurum Rhizosolenia shrubsolei Synedra gallionii

Pleurosigma speciosum Rhizosolenia sigma Synedra pulchella

Proboscia alata Rhizosolienia robusta Tabellaria flocculosa

Pseudo-nitzschia australis Rhizosolienia setigera Thalasiossira anguste-lineata

Pseudo-nitzschia pungens Rhizosolienia styliformis Thalasiossira decipiens

Pseudosolenia calcar Rizosolenia calcar Thalassionem anitzschioides

Rhizosolenia alata Rizosolenia striata Thalassiosira eccentria

Rhizosolenia hebetata Schroederella delicatula Thalassiothrix frauenfeldii

Rhizosolenia bergonii Skeletonema costatum Thallasiothrix longissima

Rhizosolenia castracanei Stephanopyxis palmeriana Triceratium reticulatum

Rhizosolenia cochlea Stephanopyxis turrisRhizosolenia hyaline Striatella unipunctata Rhizosolenia imbricate Surirella ovalis Cylindrotheca gracilis Navicula elegans

Citation: Karthik R, Arun Kumar M, Sai Elangovan S, Siva Sankar R, Padmavati G (2012) Phytoplankton Abundance and Diversity in the Coastal Waters of Port Blair, South Andaman Island in Relation to Environmental Variables. J Mar Biol Oceanogr 1:2.

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doi:http://dx.doi.org/10.4172/2324-8661.1000102

Month Area Station No. of Species Dominant Species

September'11 MAA S1 257 Coscinodiscus centralisMAA S2 9500 Coscinodiscus centralis*LAA S3 173 Pleurosigma affineLAA S4 158 Leptocylindrus danicus

October MAA S1 75 Coscinodiscus graniiMAA S2 136 Coscinodiscus graniiLAA S3 65 Licmophora ehrenbergiiLAA S4 37 Licmophora ehrenbergii

November MAA S1 165 Bacteriastrum furcatumMAA S2 157 Bacteriastrum hyalinumLAA S3 36 Nitzschia sigmaLAA S4 34 Pleurosigma angulatum

December MAA S1 8700 Rhizosolenia alataMAA S2 9500 Rhizosolenia alata*LAA S3 42 Licmophora gracilisLAA S4 42 Coscinodiscus granii

January MAA S1 174 Guinardia steriataMAA S2 152 Guinardia flaccidaLAA S3 28 Nitzschia gracilisLAA S4 96 Chaetoceros decipiens

Febrauary MAA S1 147 Guinardia steriataMAA S2 249 Leptocylindrus danicusLAA S3 52 Asterionella glacialisLAA S4 25 Guinardia steriata

March'12 MAA S1 197 Rhizosolenia imbricataMAA S2 19000 Rhizosolenia imbricataLAA S3 27000 Trichodesmium erythraeum*LAA S4 87 Proboscia alata

Table 6: List of dominant species of phytoplankton within the coastal waters of South Andaman.

MAA: More Anthropogenic Activity (St. 1 and St. 2); LAA: Less Anthropogenic Activity (St. 3 and St. 4)*bloom forming diatoms and blue green algae

Moreover, phytoplankton species numbers of this region were strongly associated with its local environmental variables in this and other studies [11].

High population density during Sep, Dec and Mar might be due to the predominance of diatoms Coscinodiscus centralis, Rhizosolenia imbricate and R. alata and blue-green algae such as Trichodesmium erythraeaeum. During the study period, phytoplanktons were abundant when the coastal waters were enriched with nutrients. Nutrients, more importantly the nitrate and silicate, have emerged as the key factors controlling the phytoplankton growth in this area. The coastal waters where nutrient levels are higher sustaining a richer diatom population [12]. The low phytoplankton growth during Jan and Feb could be due to lower nutrient levels in this area. Chlorophyll a and nutrients showed a significant (p<0.05) positive correlation at Stations 2 and 3 (p<0.05), indicating the influence of nitrate and silicate on phytoplankton growth at this area. Bloom forming diatom species require silicon as a major nutrient and the ratio of nitrate and silicate influence the composition of phytoplankton as observed in this study has been reported earlier [13-15].

Predominance of diatoms in phytoplankton assemblage and dominance of centrics over pennates with respect to species number are common phenomena in coastal waters. Diatoms are larger in size as compared to other phytoplanktonic components, increasing

their rate of sinking. Thus, to overcome this problem, diatom always prefers to inhabit and dominates the phytoplankton community in shallow coastal region [16].

Bacteriastrum hyalinum, Coscinodiscus granii, Eucampia zoodiacus, Leptocylindrus danicus, Nitzschia closterium, Odentella sinensis, O. mobiliensis, Pleruosigma affine, Rhizosilenia alata, R. imbricata, Prorocentrum micans, Protoperidinium depressum, Asterionella glacialis, Guinardia striata, Licmophora gracilis, Pleurosigma angulatum, Skeletonema costatum and Thalassionema nitzschioides were common during the present observation. Similar observations have been made from different locations of east coast of India [8,15].

Devassy and Bhattathiri reported that dinoflagellates as largest group followed by diatoms from little Andaman Island but this was not observed in this study [12]. Dinoflagellates were represented by 58 species belong to 16 genera which is low compared to an earlier report from the oceanic region in this area [17] but are higher than other studies from this region [9]. These findings suggest that these organisms might not be able to withstand the fluctuations in the environmental conditions and possibly have a lower chance of survival. They are able to thrive successfully in oligotrophic tropical waters unlike diatoms [12]. Most of the dinoflagellates are mixotrophic or heterotrophic and gain their nutrition through a combination of photosynthesis and uptake of dissolved or particulate organic material or phagotrophy on ciliates [18,19]. In this study maximum population density of dinoflagellates was recorded during Mar at Stations 4 and 1 when both minimal salinity and temperature values were observed.

Further, absence of some genera of dinoflagellates viz., Pyrocycystis, Exuviaella, Achnanthes, Amphitholus, Asteromphalus, Gossleriella, Gloedinium, Fragilaria, Phalacroma, Plantoniella, Rabdosphaera, Thracosphaeraand Oxytoxum, Amphidinium, Amphisolenia, Heterolaucus, and Ceratocorys [8,17] in the present study could be due to their adoption to different depths within oceanic regions.

The blue green algal population was composed of Oscillatoria sp, Lyngbya sp and Trichodesmium erythraeum. Only one of these species, Trichodesmium erythraeum, appeared throughout the study and caused blooms with considerable cell densities 27000 cells ml-1 at St. 3 during Mar. Formation of Trichodesmium blooms as observed in this study have been reported earlier from the Arabian Sea [20] and Bay of Bengal [10].

The toxic dinoflagellates such as Alexandrium tamarense, A. catenella, Lingulodinium polyedrum, Goniaulax conjuncta, Noctiluca scintillans and Gonyaulax polygramma were observed with low cell densities. Among them, Noctiluca scintillans, Lingulodinium polyedrum, Gonyaulax polygramma and Alexandrium catenella were recorded at almost all stations during Sep and Mar.

Species diversity (H’=0.6 to 0.8) and equitability (J=0.1 to 0.2) indices showed minimum values at Stations 2 and 3 which co-occurred with bloom forming diatoms. The evenness index approached zero when a single species becomes very abundant. The diatom blooms at stations Stations 2 and 3 led to low evenness and diversity indices. There were two major clusters were observed. The bloom-forming species at Stations 2 and 3 formed one cluster. Species in Stations 1 and 4 formed a separate cluster where dinoflagellates were dominant.

Citation: Karthik R, Arun Kumar M, Sai Elangovan S, Siva Sankar R, Padmavati G (2012) Phytoplankton Abundance and Diversity in the Coastal Waters of Port Blair, South Andaman Island in Relation to Environmental Variables. J Mar Biol Oceanogr 1:2.

• Page 6 of 6 •Volume 1 • Issue 2 • 1000102

doi:http://dx.doi.org/10.4172/2324-8661.1000102

It is well recognized that the abundance of each species may be highly variable and, on the basis of its relationship with other species, this may affect the patterns of assembling or grouping are established at locations throughout the region [21].Acknowledgement

Authors are thankful to the Head of the Department, Ocean Studies and Marine Biology, Pondicherry University, Port Blair for providing facilities.

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Month IntervalsNo. of. Species Species diversity H’ Evenness

S1 S2 S3 S4 S1 S2 S3 S4 S1 S2 S3 S4Sep’11 33 27 28 29 2.49 0.01 2.8 2.84 0.71 0.04 0.84 0.84

Oct 30 22 27 21 2.83 2.45 2.51 2.58 0.83 0.79 0.76 0.76Nov 37 30 18 19 2.49 2.71 2.49 2.62 0.69 0.79 0.86 0.86Dec 15 24 30 22 0.13 0.09 2.99 2.85 0.04 0.03 0.87 0.87Jan 42 39 45 37 2.46 2.85 3.41 2.82 0.66 0.78 0.89 0.89Feb 42 37 46 42 3.21 2.76 3.3 3.32 0.86 0.76 0.86 0.86

Mar’12 68 31 29 51 3.55 0.05 0.03 3.61 0.84 0.01 0.01 0.01

Table 7: Number of phytoplankton species (S), diversity indices (H’) and equitability (J) during September 2011 to March 2012 in the study area.

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Sim

ilarit

y (%

)

Figure 4: Dendogram of the cluster analysis showing affinities of the species and formation of similar taxanomic groups.

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Author Affiliations Top1Department of Ocean Studies and Marine Biology, Pondicherry University, Andaman, India2Department of Ecology and Environmental Sciences, Pondicherry University, Puducherry, India