Karthik et al., J Mar Biol Oceanogr 2012, 1:2 http://dx.doi.org/10.4172/2324-8661.1000102 Journal of Marine Biology & Oceanography Research Article a SciTechnol journal The effects of environmental factors on plankton dynamics has been Phytoplankton Abundance investigated by several authors [3-5]. The influence of various factors on the seasonal growth and abundance of phytoplankton differs and Diversity in the Coastal significantly, with physical (such as temperature and light intensity) and chemical factors (dissolved oxygen, pH, salinity, total hardness, Waters of Port Blair, South electrical conductivity and nutrient level) as primary limiting Andaman Island in Relation to factors reported in many regions of the world [6]. Literatures on the influence of environmental variables on phytoplankton communities Environmental Variables in coastal waters around Andaman Islands are meagre. In view of the importance and scarcity of reports from this area, an investigation Karthik R1*, Arun Kumar M1, Sai Elangovan S1, Siva Sankar R2 was carried out on a monthly interval during Sep 2011 to Mar 2012 in and Padmavati G1 the coastal waters of south Andaman to assess the seasonal variability in phytoplankton community structure and related physicochemical Abstract water quality parameters. The present communication also documents the occurrence of periodic diatom blooms in the coastal The distribution and diversity of phytoplankton was studied in waters of south Andaman. the coastal waters of south Andaman Sea during Sept 2011 to Mar 2012. A total of 227 species belonging to 67 genera were Materials and Methods recorded in this study. Diatoms made larger contribution to the total abundance (68%) followed in order by Cyanophyceae (24%) Phytoplankton sampling and analysis and Dinoflagellates (8%). Silicoflagellates were numerically less (0.4%). Diatoms were represented by 164 species belonging to 46 This phytoplankton study was conducted during Sep 2011 genera, Dinoflagellates were represented by 58 species belonging to Mar 2012 in two distinct areas including: (1) areas with more to 16 genera, Cyanophyceae and Silicoflagellates comprised anthropogenic activity (i.e. fishing harbor, fish landing centre and 2 genera each. Bacteriastrum hyalinum, Coscinodiscus granii, fishing community (Stations 1 and 2); and (2) areas with lower levels of Eucampia zoodiacus, Leptocylindrus danicus, Nitzschia closterium, anthropogenic activity (Stations 3 and 4) (Figure 1). Physicochemical Odentella sinensis, O. mobiliensis, Pleruosigma affine, Rhizosilenia alata, R. imbricata, Prorocentrum micans, Protoperidinium water quality parameters such as seawater temperature, salinity and depressum, Asterionella glacialis, Guinardia striata, Licmophora dissolved oxygen were recorded at each station. Salinity (ppt) was gracilis, Pleurosigma angulatum, Skeletonema costatum and measured with a hand held Refractometer (ATAGO). Dissolved Thalassionema nitzschioides were the most prevalent diatoms oxygen (mg/L) was estimated by the modified Winkler’s method while and dinoflagellates encountered in the samples. The population phytoplankton biomass was estimated as chlorophyll a (µg/L) (90% 5 5 -1 density of phytoplankton ranged from 0.4 × 10 to 4.2 × 10 cells L . acetone method) measured spectrophotometrically in the laboratory 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 [7]. Nutrients [nitrate, silicate and phosphate (µmol/L)] were also Coscinodiscus centralis (95000 cells ml-1), Rhizosolenia imbricata measured during the study [7]. For phytoplankton studies, samples (19000 cells ml-1) and R. alata (9500 cells ml-1). Relatively higher were collected in 1 liter labeled plastic containers by filtering 50 L of species diversity (H’= 3.6) and equitability in plankton flora (J=0.9) water, using a phytoplankton net (20 µm) and immediately preserved 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 Introduction Phytoplanktons 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: [email protected] Received: September 13, 2012 Accepted: December 07, 2012 Published: Figure 1: The study area and location of the sampling sites. December 14, 2012 All articles published in Journal of Marine Biology & Oceanography are the property of SciTechnol, and is protected by International Publisher of Science, copyright laws. “Copyright © 2012, SciTechnol, All Rights Reserved. Technology and Medicine 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. doi:http://dx.doi.org/10.4172/2324-8661.1000102 with 4% formalin and fixed with Lugol’s iodine for quantitative occurrence of the diatom bloom of Coscinodiscus centralism. Higher and qualitative analysis. The samples were left to settle for 24 hrs dissolved oxygen and lower salinity at St. 1 and St. 3 during Sep and and concentrated to 10 ml by siphoning out the supernatant. In the Nov were due in part to influx of fresh water from precipitation and laboratory, for phytoplankton taxonomy studies, 1 ml sample was seepage and runoff of fresh water from the land. taken from concentrated sample by using a Sedgwick-Rafter counting Nutrients chamber and examined under the plankton inverted microscope. The total numbers of phytoplankton present in a liter of samples were The concentrations of nitrate (NO3), phosphate (PO4) and silicate calculated according to the following equation: (SiO4) showed pronounced spatial and temporal variation during the n × v present investigation (Table 2). The nitrate content varied between N = ×1000 0.1 umol l-1 in Oct and 5.61 umol l-1 in Sept. Silicate concentrations V Where N is the total number of phytoplankton cells per liter of 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 water filtered, n is an average number of phytoplankton cells in 1ml -1 -1 of sample, v is the volume of phytoplankton concentrates, V is the fluctuated between 0.1 umol l in Feb and 0.6 µmol l in Sept. The volume of total water filtered. relative amount of nitrate-silicate and nitrate-phosphate ratio was higher during periods of algal blooms. Statistical analysis Chlorophyll a concentrations varied from 0.01-0.16 µg l-1 (Table Statistical analysis was performed by using statistical software 3). Higher values of Chlorophyll a (0.16 µg l-1) was recorded during Primer (Ver. 5). Two-way analysis of variance (ANOVA) was Sep, Dec and Mar at St. 2 due to bloom forming diatoms such as employed and the level of significance was used to define statistically Coscinodiscus centralis, Rhizosolenia alata and Rhizosolenia imbricate significant differences. Biodiversity indices (species richness, diversity followed by 0.14 µg l-1 during Mar which was due to blue-green algae and equitability) were calculated in the phytoplankton population Trichodesmium erythraeum at St. 3. using monthly intervals between samples and cluster analysis to Population density and distribution discern species similarities between different sampling stations. The overall mean phytoplankton abundance was higher (p<0.05) Results at St. 3 compared to other stations in the study area (Figure 2). Physicochemical parameters Minimum densities were recorded at St. 4. Monthly and station wise variations of phytoplankton densities are clearly depicted in table Variations in temperature, salinity and dissolved oxygen among 4. Well marked monthly variations were observed in population stations and sampling dates are shown in table 1. During the study densities of phytoplankton. The lowest densities (215 and 261 cells/ period, water temperature varied from 25-28°C. The high temperature ml) were observed in the month of Nov at Stations 1 and 2, whereas (28°C) was recorded during Oct 2011 at all stations. Salinity ranged the highest population density (95000 cells/ml) was observed during from 30 to 34% and it was highest during Oct and Dec at all stations. Sep at St. 2 due to the dense aggregation of Coscinodiscus centralis cells Both water temperatures and salinities were generally low during the (95000 cells/ml) followed by high densities (27000 cells/ml) during monsoon period during Sept. Dissolved oxygen varied from 3.2 mg/l- Mar at St. 3 due to blue-green algae Trichodesmium erythraeum when 4.5 mg/l throughout the study at all sites. Maximum values (4.5 mg/l) temperature salinity and dissolved oxygen were recorded low and were recorded during Dec 2011 at Stations 1 and 4 and minimum nutrients such as nitrate, silicate and phosphate were high. Population during Sept at St. 2 (3.2 mg/l), which was due in a large part to the density was quite low at St. 4 during the study period. Table 1: Variations in physico-chemical water quality parameters during September 2011 to March 2012 in the study area. Temperature (ºC) Salinity (%) Dissolved oxygen (ml/l) Month Intervals S1 S2 S3 S4 S1 S2 S3 S4 S1 S2 S3 S4 Sep’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 4.3 Nov 25 28 25 26 31 32 30 32 4.3 3.9 4.1 4.1 Dec 26 25 27 26 33 34 32 32 4.5 3.9 3.9 4.5 Jan 28 28 26 25 32 32 32 30 4.4 4.1 4.2 3.7 Feb 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 2: Variations in nutrient concentration during September 2011 to March 2012 in the study area.