Phytoplankton composition and abundance in the coastal waters of the Datça and Bozburun Peninsulas, south-eastern Aegean Sea (Turkey) - PDF

Mediterranean Marine Science Indexed in WoS (Web of Science, ISI Thomson) and SCOPUS The journal is available on line at DOI: Research Article

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Mediterranean Marine Science Indexed in WoS (Web of Science, ISI Thomson) and SCOPUS The journal is available on line at DOI: Research Article Phytoplankton composition and abundance in the coastal waters of the Datça and Bozburun Peninsulas, south-eastern Aegean Sea (Turkey) S. TAŞ Institute of Marine Sciences and Management, Istanbul University, Müşküle Sok , Vefa-Istanbul, Turkey Corresponding author: Handling Editor: Lydia Ignatiades Received: 3 April 2013; Accepted: 28 June 2013; Published on line: 27 September 2013 Abstract A study on the abundance and composition of some groups of phytoplankton (diatoms, dinoflagellates and silicoflagellates) was carried out in the marine areas of the Datça and Bozburun Peninsulas between 2002 and Simultaneously, measured physical (salinity, temperature, secchi disc) and chemical parameters (nutrients, chlorophyll a, dissolved oxygen) were assessed together with phytoplankton data. Seawater and plankton net samples were taken from 63 stations during 6 sampling periods. A total of 132 taxa (genus, species and infraspecies level) belonging to 3 taxonomic classes were reported and a checklist of phytoplankton was prepared for this study area. Average nutrient values in surface water ranged from 0.01 to 1.19 µm for NO 3 +NO 2 N, from 0.01 to 0.69 µm for PO 4 P and from 0.50 to 5.31 µm for SiO 2 Si and chl a values were between 0.19 and 0.68 µg l 1 throughout the study area. The highest number of phytoplankton cells reached 5400 cells l 1 and dinoflagellate Prorocentrum micans reached 1500 cells l 1 while diatom Thalassionema nitzschioides reached 700 cells l 1. Dinoflagellates showed a more homogeneous distribution in a wider area than diatoms. Dinoflagellate abundance increased in areas close to the fish farms due to the amount of nutrients originating from the farms. Spatial changes in phytoplankton composition observed in this marine area revealed that phytoplankton is very sensitive to ecosystem changes. The study area could generally be defined as oligotrophic in terms of trophic status, depending on the nutrient and chl a concentrations. Moreover, very low cell abundance and the high number of species observed in this area also reflect the typical characteristics of oligotrophic waters. Keywords: Aegean Sea, Datça Bozburun, diatoms, dinoflagellates, phytoplankton. Introduction Phytoplankters are the basic food in the sea for all consumers such as zooplankton and fish. In recent years, applied aspects of phytoplankton research have become increasingly important (Zeitzschel, 1978). The life cycle of phytoplankton varies from a few hours to a few days. So, they reflect the effect of environmental, changes in a short time (Polat et al., 2005). The Aegean Sea is one of the Eastern Mediterranean basins displaying a complicated hydrographic and ecological structure due to its geographical position between the Black Sea and the Ionian and Levantine Seas (Siokou-Frangou et al., 2002; Zervakis et al., 2000). The Aegean Sea is separated by the Cyclades plateau into two subbasins, the North Aegean and the South Aegean, with significantly different hydrographic characteristics due to the influence of Black Sea waters and Levantine Sea waters, respectively (Ignatiades et al., 2002). Several studies on the temporal variations in biomass, primary production and species composition of phytoplankton communities have been carried out in the Southern Aegean (Becacos-Kontos, 1977; Ignatiades, 1976; Ignatiades et al., 1995; Gotsis- Skretas et al., 1996; Psarra et al., 2000). The results demonstrate the extremely oligotrophic status of waters (Ignatiades et al., 2002; Ignatiades, 2005). The Mediterranean is considered to be one of the least productive seas in the world. Concentrations of nutrients decrease from the west to the east of the Mediterranean Sea (Azov, 1991; Krom et al., 1991). The north-eastern Mediterranean is the most oligotrophic part of the Mediterranean Sea. Low terrestrial input, nutrient poor waters, and the hot and dry climate are responsible for very limited plankton biomass and primary production (Turley et al., 2000). Also, phosphorus is considered to be a limited nutrient in the eastern Mediterranean (Krom et al., 1991). Phytoplankton production and nutrient concentration in the eastern Mediterranean is dependent on the duration and the intensity of deep water mixing, which allows transport of nutrients from a deeper layer to the surface (Yilmaz & Tugrul, 1998). A number of studies on phytoplankton communities, dealing mainly with taxonomy, ecology and biomass distribution, have been carried out in the north-eastern Mediterranean Sea (Kideyş et al., 1989; Eker & Kideyş, 2000, Polat et al., 2000; Polat & Işik, 2002; Polat, 2002; 84 Medit. Mar. Sci., 15/1, 2014, 84-94 Polat & Piner, 2002a; Polat & Piner, 2002b; Polat et al., 2005; Eker-Develi et al., 2006; Polat, 2007; Polat & Koray, 2007; Balkis, 2009; Ozman-Say & Balkis, 2012). The Datça-Bozburun Specially Protected Area is one of thirteen specially protected areas in Turkey. The aim of this study is to investigate the taxonomic composition and abundance of the phytoplankton community in the coastal waters of the Datça and Bozburun Peninsulas, south-eastern Aegean Sea. The main environmental factors recorded during this study were also investigated and evaluated together with phytoplankton data. Materials and Methods Study area The Datça Peninsula extends in an East to West direction and is located between the Gökova Gulf in the north and the Hisarönü Gulf in the south, while the Bozburun Peninsula lies to the South of the Datça Peninsula and extends towards the Island of Rhodes in the South (Okus et al., 2007). The study area was surveyed in six cruises and during each cruise a different region was studied. Cruise names and periods are as follows; DAT1: May 2002, DAT2: September 2002, DAT3: May 2003, DAT4: June 2003, DAT5: September 2003 and DAT6: April 2004 (Fig. 1). Station codes indicate the cruise number and the sampling station within that cruise; for example DAT1/01indicates Station 1 of Cruise-1 (May 2002). The water samples were taken from 11, 11, 13, 11, 10, and 7 stations from DAT1 to DAT6, respectively. Seawater samples were collected from 63 stations between May 2002 and April 2004 and oceanographic measurements were performed during the entire study period. All the sampling stations, except for DAT6/2, were inshore and only DAT6/2 was an offshore station. Seawater analysis Water salinity and temperature measurements were recorded by a SBE Sea Logger 25 CTD probe system during the study period except in May 2003 (DAT3), when the physical data could not be measured due to a fault in the pressure sensor of the CTD probe system. A deep station in each sampling area was selected in order to draw the temperature and salinity profiles. Light transparency of water column was measured using a Secchi disc. Water samples were collected using 5 L Niskin bottles from 0.5, 5, 10 m and bottom water depending on the water depth at the sampling station. Samples for nutrients (NO 2 +NO 3 N, PO 4 P and SiO 2 Si) analysis were deep frozen at 20 C until they were analyzed. Nutrient analyses were performed by a Bran+Luebbe AA3 auto analyzer (Grasshoff et al., 1983). Chlorophyll a analyses were carried out using the acetone extraction method according to Parsons et al. (1984). Dissolved oxygen (DO) was measured according to the Winkler titration method (APHA, 1999). A suitable station representing each sampling area was selected in order to show the vertical distribution of chemical analysis. Fig. 1: Study area and sampling stations. Medit. Mar. Sci., 15/1, 2014, Phytoplankton analysis Microphytoplankton ranges between 20 and 200 µm in the classification of phytoplankton according to the scaling nomenclature of Sieburth et al. (1978). In this study, three groups belonging to this classification such as diatoms (Bacillariophyceae), dinoflagellates (Dinophyceae) and silicoflagellates (Dictyochophyceae) were analyzed and evaluated in the phytoplankton community. For the enumeration of phytoplankton, seawater samples were taken using 5 lt Niskin bottles. Water samples were immediately preserved with a neutralized formaldehyde solution at a final concentration of 0.4% (Throndsen, 1978). In the laboratory, samples were left to settle for a week according to the Utermöhl method (Utermöhl, 1958). After sample sedimentation, excess water in the upper part was removed and concentrated to 100 ml (Sukhanova, 1978). Then, these sub samples were stored in dark coloured glass bottles until microscopic examination. Enumerations were carried out using an Olympus CH 2 light microscope (10, 20 or 40 ) on a Sedgewick Rafter counting chamber (Guillard, 1978). Species identification were also carried out using a Nikon Diaphot 300 inverted microscope with camera and phase contrast equipment, and images of some species were taken for biometric measurements. Plankton net sampling was used to investigate the species richness of phytoplankton. A plankton net (0.57 m diameter, 55 μm mesh) was vertically towed from 15 m to the surface. The following references were used for the identification of species: Cupp, 1943; Delgado & Fortuna, 1991; Dodge, 1985; Drebes, 1974; Hendey, 1964; Ricard & Dorst, 1987; Hasle et al., The recent revisions of dinoflagellate species were presented according to Gómez (2005, 2012). Data analysis Total microphytoplankton, dinoflagellate and diatom abundances, number of species (S), and Shannon index of diversity (H, bits) were used as univariate descriptors. The relationship among total phytoplankton, dinoflagellate and diatom abundances, number of species, Shannon index of diversity and environmental parameters were analyzed by the Spearman rank correlation, following transformations to natural logarithms. Results Hydrobiological data The data was collected during sampling periods that typically took place in spring and autumn. Surface water temperature ranged from 16.8 o C (April 2004) to 25.4 o C (September 2002) during the study period and was higher in the sheltered bays than offshore. The increased water temperature of the upper layer leads to the formation of a seasonal thermocline from April to June. A layer of thermocline formed due to the increased temperature of surface water in May 2002 and June In September 2002, a well defined thermocline and a thicker upper layer were observed. Salinity values were measured within the range of 38.6 to 39.4 psu in the whole study area. The salinity values of the upper layer increased vertically from 0.2 to 0.4. Salinity values in the sampling area varied slightly between psu (Fig. 2). The highest secchi depth was measured as 30 m at station DAT2/4 (Sept. 2002, St.4). Secchi disc value, which was about 20 m in the study area, decreased to 9 m at station DAT1/08 (May 2002, St.8) due to the long flushing time in the inner parts of the Gulf, settlements and tourism. Secchi disc values were generally less than 20 m in the DAT3 sampling area where shipyard activities and fish farms exist. Inorganic nutrients exhibited very low concentrations in the study area, which has an oligotrophic character. Average nutrient values in surface water ranged from 0.01 to 1.19 µm for NO 3 +NO 2 N, from 0.01 to 0.69 µm for PO 4 P and from 0.50 to 5.31 µm for SiO 2 Si. Nutrient concentrations were higher in regions of increased freshwater input and also of high tourism activities. The highest P PO 4 value was measured as 0.69 µm at station DAT4/11 (June 2003, St.11) and this is 10 fold higher than the value obtained for the Aegean Sea prior to this Fig. 2: Temperature and salinity profiles in the sampling periods. 86 Medit. Mar. Sci., 15/1, 2014, 84-94 Table 1. Spearman rank correlation coefficients (rho) between environmental parameters and total microphytoplankton, dinoflagellate and diatom abundances; number of species (S), Shannon index of diversity (H ). Rho Temperature Salinity DO Chl-a NO 3 +NO 2 PO 4 SiO 2 Total phytoplankton * *** Dinoflagellate *** Diatom ** Number of species * *** Shannon index * *** *p 0.05; **p 0.01; ***p 0.001 Fig. 3: Fluctuations in chl-a, dissolved oxygen and nutrient concentrations. Medit. Mar. Sci., 15/1, 2014, study. High domestic pollution in this area could be a reason for this increase (Fig. 3). The spatial distribution of chl a showed some differences depending on physical and chemical characteristics. The average values of chl a in surface water were 0.34, 0.19, 0.68, 0.15, 0.17 and 0.22 µg l 1 for DAT1, DAT2, DAT3, DAT4, DAT5 and DAT6, respectively. Chl a concentrations were relatively higher for DAT3 than other areas depending on phytoplankton productivity, because this area is affected by tourism activities and fish farms. Throughout the sampling area, the majority of chl a values (87%) were less than 0.5 µg l 1 and 9% of the values were between 0.5 and 1µg l 1. Only 4% of the values exceeded 1 µg l 1. Vertical distribution of chl a values was almost homogeneous in the whole study area except the DAT3 region (Fig. 3). A significant positive correlation was detected between cell abundance, number of species, Shannon index values, and chl a values (Table 1). High dissolved oxygen (DO) concentrations were measured in the whole study area and showed a homogeneous distribution from surface to the bottom. DO values varied between 6.7 and 8.3 mg l 1 at the surface and between 6 and 8.7 mg l 1 in deeper waters (Fig. 3). Phytoplankton composition and abundance A total of 132 taxa (genus, species and infraspecies level) belonging to 3 taxonomic classes were observed in both plankton net and water samples, 119 of which were identified to species level (Table 1). Diatoms and dinoflagellates were two major groups in the whole study area. Diatoms were the most diverse algal group with 71 (53.7%) taxa, followed by dinoflagellates with 60 taxa (45.4%) and silicoflagellate was only one taxa. Most genera were Neoceratium (21 taxa) and Protoperidinium (14 taxa) from dinoflagellates and Chaetoceros Ehrenberg (23 taxa) from diatoms. A checklist of phytoplankton species in water and net samples are presented in Table 2. Plankton net samples show that the coastal area of Datça and Bozburun Peninsulas is rich in species composition. 86% of the reported phytoplankton species were observed in net samples (Table 2). Spatial distribution of phytoplankton composition showed some differences. The DAT1 sampling area was the most abundant in terms of species richness with 58 taxa, while DAT3 was much less abundant with 26 taxa. Diatoms were dominant in the DAT1 and DAT6 areas; dinoflagellates were dominant in the other areas in terms of the number of species. Dinoflagellates were more common and dominant than diatoms in some parts of DAT3, which means that the risk of pollution might be higher than in other areas due to the fish farms. The species encountered most frequently in net samples were Neoceratium arietinum, N. candelabrum, N. furca, N. fusus, N. massiliense, N. tripos, Lingulodinium polyedrum, Protoperidinium depressum, P. divergens and P. oceanicum from dinoflagellates; Bacteriastrum delicatulum, Detonula confervacea, Hemialus hauckii, Pseudosolenia calcar avis, Striatella unipunctata and Thalassionema nitzschioides from diatoms. Fewer species were detected in the water samples than in the net samples. Water samples comprised 54% of all phytoplankton species observed in this study, and the species encountered most frequently in water samples were Neoceratium fusus, P. micans, P. scutellum, Protoperidinium mediterraneum and S. trochoidea from dinoflagellates; H. hauckii, Streptotheca thamensis and T. nitzschioides from diatoms (Table 2). Images of light microscopy of some dinoflagellate species are given in Figure 4. Fig. 4: Light micrographs of some dinoflagellate species identified in the study area. (A) Neoceratium hexacanthum, (B) N. trichoceros, (C) N. massiliense, (D) N. pulchellum, (E) N. teres, (F) N. macroceros, (G) Ceratocorys horrida, (H) Ornithocercus magnificus (Scale bars= 100 µm), (I) O. quadratus (Scale bar= 50 µm). 88 Medit. Mar. Sci., 15/1, 2014, 84-94 Table 2. Checklist of species identified in the net and water samples and local distribution of phytoplankton in the Datça and Bozburun Peninsulas (N: Net samples, W: Water samples). Sampling area Species N W DAT1 DAT2 DAT3 DAT4 DAT5 DAT6 Bacillariophyceae Achnantes longipes C.Agardh Achnantes sp Asterionellopsis glacialis (Castracane) Round Asterolampra grevillei (Wallich) Greville Asterolampra marylandica Ehrenberg Asteromphalus flabellatus (Brébison) Greville Asteromphalus heptactis (Brébison) Ralfs Asteromphalus sp Bacteriastrum delicatulum Cleve Bacteriastrum elongatum Cleve Chaetoceros affinis Lauder Chaetoceros affinis var. willei (Gran) Hustedt Chaetoceros borealis Bailey Chaetoceros compressus Lauder Chaetoceros costatus Pavillard Chaetoceros curvisetus Cleve Chaetoceros danicus Cleve Chaetoceros decipiens Cleve Chaetoceros diadema (Ehrenberg) Gran Chaetoceros diversus Cleve Chaetoceros eibenii Grunow Chaetoceros gracilis Schütt Chaetoceros holsaticus Schütt Chaetoceros laciniosus Schütt Chaetoceros lauderi Ralfs Chaetoceros lorenzianus Grunow Chaetoceros messanensis Castracane Chaetoceros peruvianus Brightwell Chaetoceros simplex Ostenfeld Chaetoceros teres Cleve, Chaetoceros tortissimus Gra Chaetoceros wighamii Brightwell Chaetoceros sp Climacosphenia moniligera Ehrenberg Coscinodiscus sp Cylindrotheca closterium (Ehrenberg) Reimann & Lewin Dactyliosolen fragilissimus (Bergon) Hasle Dactyliosolen mediterraneus H. Peragallo Detonula confervacea (Cleve) Gran Grammatophora marina (Lyngbye) Kützing Guinardia delicatula (Cleve) Hasle Guinardia flaccida (Castacane) Peragallo Guinardia striata (Stolterfoth) Hasle _ + + Gyrosigma sp Hemiaulus hauckii Grunow ex Van Heurck Leptocylindrus danicus Cleve Licmophora abbreviata Agardh Licmophora sp Navicula sp Nitzschia longissima (Brébisson) Ralfs Nitzschia sp Odontella mobiliensis (J.W.Bailey) Grunow (continued) Medit. Mar. Sci., 15/1, 2014, (continued) Table 2. Sampling area Species N W DAT1 DAT2 DAT3 DAT4 DAT5 DAT6 Pleurosigma normanii Ralfs Pleurosigma sp Proboscia alata f. alata (Brightwell) Sundström Proboscia alata f. gracillima (Brightwell) Sundström Proboscia alata f. indica (H. Peragallo) Gran Pseudo-nitzschia delicatissima (Cleve) Heiden Pseudo-nitzschia pungens (Grunow ex P.T.Cleve) G.R.Hasle Pseudosolenia calcar-avis (Schultze) Sundström Rhabdonema adriaticum Kützing Rhizosolenia hebetata var. semispina (Hensen) Gran Rhizosolenia imbricata var. shrubsolei (Cleve) Schröder Rhizosolenia styliformis Brightwell Skeletonema costatum (Greville) Cleve Streptotheca thamensis Shrubsole Striatella unipunctata (Lyngbye) Agardh Synedra undulata (Bailey) Gregory Thalassionema nitzschioides (Grunow) Mereschkowsky Thalassiothrix frauenfeldii Grunow Thalassiothrix mediterranea Pavillard Dinophyceae Alexandrium sp Ceratocorys gourretii Paulsen Ceratocorys horrida Stein Corythodinium tesselatum (Stein)Loeblich Jr. & Loeblich III Dinophysis acuta Ehrenberg Dinophysis caudata Saville-Kent Dinophysis hastata Stein Dinophysis tripos Gourret Diplopsalis lenticula Bergh Gonyaulax grindleyi Reinecke Gonyaulax sp Gyrodinium sp Heterocapsa triquetra (Ehrenberg) Stein Lingulodinium polyedrum (Stein) Dodge Neoceratium arietinum (Cleve) F. Gómez, D. Moreira & P. López-García Neoceratium candelabrum (Ehrenb.) F. Gómez, D. Moreira & P. López-García Neoceratium carriense (Gourret) F. Gómez, D. Moreira & P. López-García Neoceratium contortum (Gourret) F. Gómez, D. Moreira & P. López-García Neoceratium declinatum (G. Karst.) F. Gómez, D. Moreira & P. López-García Neoceratium euarcuatum (Jørgen.) F. Gómez, D. Moreira & P. López-García Neoceratium furca (Ehrenberg) F. Gómez, D. Moreira & P. López-García Neoceratium fusus (E
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