___

• - - 00 (max) Bizsel et al., 2001 0.04–65.67 0.00–7.59 0.01–5.46 0.09–12.06 0.00–6.38 Kaymakçı et al., 2001 80 (max) 12 (max) 60 (max) 00 (max) Gencay and Büyükışık, 2004 0.06–40.72 0.19–24.86 0.00–25.90 0.87–17.58 0.78–48.60 0.00–3 .93/1.31 Kükrer and Aydın, 2006 0.00–40.94/5.31 0.00–21.35/3.28 0.00–28.99/2.27 0.00–31.41/3.28 0.16–54.12/10.82 0.00–66.13/4.26 Sunlu et al., 2012 0.23–22.28/3.28 54–11.7 7/4.27 0.00–3.51/0.64 0.00–5.96/2.17 99–41.94/10.80 03–30.26/12.44 This study
• Numbers written after “/” indicate average values. than NO – 3 -N over the sampling period. McCarty (1980) reported that this situation was normal and NO – 2 -N accumulates noticeably under low DO condition. Koray et al. (1992) emphasised that a large part of total nitrogen in the polluted İzmir Bay was ammonium from industrial and domestic wastes. In contrast, in our study nitrate had the largest share of total nitrogen concentration due to the WTP, which reduces ammonium inputs. Additionally, ammonium concentration is kept under control by phytoplankton over a year. In spite of this progress, the ammonium enrichment continues owing to the creeks and sediment, which have high ammonium concentrations
• (Ozkan et al., 2008). The capacity of the wastewater plant has not been sufficient for phosphate reduction according to previous studies (Kontas et al., 2004; Kucuksezgin et al., 2006; Kükrer & Aydın, 2006). Although the phosphate concentration we found was lower than the values in those studies, it is thought that the decreases in phosphate concentration are a result of phytoplankton consumption. The observed mean N:P value was lower than the assimilatory optimal (N:P = 15:1) in conformity with Redfield’s ratio N:P = 16:1 due to the reduction in nitrogen. The Eastern Mediterranean is one of the world’s poorest seas as a concept based on the impoverished phytoplankton biomass and productivity levels mainly due to phosphorus deficiency (Ignatiades et al., 2002).
• However, in İzmir Bay, as a part of the Mediterranean basin, nitrogen is a limited nutrient. Nutrient levels found in this study in the inner bay were higher than those in the other parts of the Aegean Sea (Table 6). Nutrients and light are probably more available to phytoplankton because of the smaller volume and the shallowness of the water column (Thomas et al., 2005). These structures of ST 1, ST 2, and ST 3 stimulate the increase in the phytoplankton biomass. The nanoplankton dominated the phytoplankton chlorophyll-a biomass at all stations and depths. Significant relationships were found between size fractionated phytoplankton and total chlorophyll-a.
• The contribution of size fractions to total chlorophyll-a was statistically significant at all stations. Generally, the picoplankton biomass increased from the surface to the bottom layers. This situation occurred more clearly at ST 4. The predominance of the <1 µm and <3 µm phytoplankton populations in the “low-light/nutrient rich” deep layer suggests that pico- and ultraplankton are better adapted to these depths of the photic zone than nanoplankton (Raimbault et al., 1988). The vertical profile of the picoplankton biomass has been described in many studies with some conflicting data. Some investigators reported a decrease in picoplankton chlorophyll-a abundance with depth, whereas others observed an increase towards the base of the euphotic zone that was attributed to the thermocline or nitracline depth or to cell preference for dim light (Ignatiades et al., 2002). It can be supposed that eutrophication caused microplankton to increase in İzmir Bay, but nanoplankton was the dominant fraction. Microphytoplankton have a greater density and therefore a greater tendency to sink than nanophytoplankton; as a result, their growth may be limited by light (Thomas et al., 2005). While the predominance of small autotrophic organisms seems to be a distinguishing feature of warm oligotrophic oceans where the <1 µm and phytoplankton biomass (Raimbault et al., 1988), in coastal estuarine areas they have been reported to account for about 24% of the total phytoplankton biomass, because small cells, due to their higher cell surface to volume ratios, are better competitors at low nutrient levels (Arin et al., 2005). All of these determinations explain the low picoplankton biomass in the polluted İzmir bay.
• According the results of PCA, silicate, which comes from rivers, and untreated phosphate as primary pollutants are most important nutrients for eutrophication. Although nanoplankton is the dominant size fraction in the bay, microplankton have a larger contribution in the variations of the ecosystems. Nitrogen compounds control picoplankton growth (Liebig’s minimum rule). With proximity to the estuaries, while the nutrient limiting effect is eliminated, salinity and pH gain more importance. Table Typical concentrations of essential nutrients (µM) in different parts of the Aegean Sea. o.PO 4 -P NH 4 -N NO 3 -N NO 2 -N NO 3 + NO 2 N total Si(OH) 4 -Si References Maliakos Gulf 0.00–0.68 0.00–0.20 0.00–0.88 Kormas et al., 2002 Aegean Sea (Northern and Southern) 0.01–0.05 0.29–0.89 18–2.40 Ignatiades et al., 2002 Saranikos Gulf 0.20–0.40 87–4.34 0.48–5.31 Moncheva et al., 2001 Thermaikos Gulf 0.44–0.70 0.60–4.63 0.10–4.47 Moncheva et al., 2001 İzmir Bay 0.00–5.96 0.23–22.28 54–11.77 0.00–3.51 91–41.94 This study
• Consequently, although nutrient levels were reduced after construction of the WTP, high nutrient inputs continue from small creeks and o.PO 4 -P plays a key role in eutrophication. It is understood that the WTP is necessary but inadequate to control eutrophication for semi-closed bays compassed by creeks. This situation necessitates total monitoring and assessment studies. Acknowledgements The authors would like to thank Ege University for its financial support and the anonymous reviewers for their valuable suggestions on this study. Thanks are due to Fadıl İnceoğlu, who provided assistance during the sampling. References Arin L, Estrada M, Salat J & Cruzado A (2005). Spatio-temporal variability of size fractional phytoplankton on the shelf adjacent to the Ebro river (NW Mediterranean). Continental Shelf Research 25: 1081–1095.
• Azari AM, Mohebbi F & Asem A (2011). Seasonal changes in phytoplankton community structure in relation to physicochemical factors in Bukan dam reservoir (northwest Iran).
• Turkish Journal of Botany 35: 77–84. Bizsel N & Uslu O (2000). Phosphate, nitrogen and iron enrichment in the polluted Izmir Bay, Aegean Sea. Marine Environmental Research 49: 101–122.
• Bizsel N, Benli HB & Bizsel C (2001). A synoptic study on the phosphate and phytoplankton relationship in the hypereutrophicated Izmir Bay (Aegean Sea). Turkish Journal of
• Engineering & Environmental Science 25: 89–99. Gencay HA & Büyükışık B (2004). Effects of sewage outfall on phytoplankton community structure in Izmir Bay (Aegean
• Sea). Ege University Journal of Fisheries and Aquatic Sciences 21: 107–111. Ignatiades L, Psarra S, Zervakis V, Pagou K, Souvermezoglou E, Assimakopoulou G & Gotsis-Skretas O (2002). Phytoplankton size-based dynamics in the Aegean Sea (Eastern
• Mediterranean). Journal of Marine Systems 36: 11–28. Iriarte JL, Pizarro G, Troncosa VA & Sobarzo M (2000). Primary production and biomass of size-fractionated phytoplankton off
• Antofagasta, Chile (23–24°S) during pre-El Nino and El Nino 19 Journal of Marine Systems 26: 37–51. Kaymakcı A, Sunlu U & Egemen O (2001). Assessment of nutrient pollution caused by landbased activities in Izmir Bay; Turkey.
• Options Mediterranennes Serie A/n44. Kontas A, Kucuksezgin F, Altay O & Uluturhan E (2004). Monitoring of eutrophication and nutrient limitation in the Izmir
• Bay (Turkey) before and after wastewater treatment plant. Environmental International 29: 1057–1062.
• Koray T, Büyükışık B, Parlak H & Gökpınar Ş (1992). Unicellular organisms effecting sea water quality in the bay of Izmir: red tides and other blooming. Doğa Turkish Journal of Biology 16: 135–157.
• Kormas KA, Garametsi V & Nicolaidou A (2002). Size-fractionated phytoplankton chlorophyll in an Eastern Mediterranean coastal system (Maliakos Gulf, Greece). Helgol Marine Research 56: 125–133.
• Kucuksezgin F, Kontas A, Altay O, Uluturhan E & Darılmaz E (2006). Assessment of marine pollution in Izmir Bay: nutrient, heavy metal and hydrocarbon concentrations. Environmental International 32: 41–51.
• Kükrer S & Aydın H (2006). Investigation of temporal changes of phytoplankton in Karşıyaka Yacht Port (İzmir Inner Bay) (in Turkish). Ege University Journal of Fisheries and Aquatic Sciences 23: 139–144.
• Martin DF (1972). Marine Chemistry, vol. 1, Analytical Methods. New York: Marcel Dekker Inc.
• Moncheva S, Skretas-Gotsis O, Pagov K & Krastev A (2001). Phytoplankton bloom in Black Sea and Mediterranean coastal ecosystems subjected to anthropogenic eutrophication: similarities and differences. Estuarine, Coastal and Shelf Science 53: 281–295.
• McCarthy JJ (1980). Nitrogen. In: Morris I (ed.) The Physiological Ecology of Phytoplankton. (Studies in Ecology) Vol. 7, pp. 191– 2 California: Blackwell Scientific Publications.
• Ozkan EY, Kocatas A & Buyukisik B (2008). Nutrient dynamics between sediment and overlying water in the inner part of Izmir Bay, Eastern Aegean. Environmental Monitoring and Assessment 143: 313–325.
• Raimbault P, Taupier-Letage I & Rodier M (1988). Vertical size distribution of phytoplankton in the western Mediterranean Sea during early summer. Marine Ecology Progress Series 45: 153–158.
• Solak CN, Barinova S, Ács É & Dayıoğlu H (2012). Diversity and ecology of diatoms from Felent creek (Sakarya river basin), Turkey. Turkish Journal of Botany 36: 191–203.
• Strickland JDM & Parsons TR (1972). A Practical Handbook of Sea Water Analysis Bulletin 167, Fisheries Research Board of Canada, Ottawa.
• Sunlu FS, Sunlu U, Buyukisik B, Kukrer S & Uncumusaoglu A (2012).
• Nutrient and chlorophyll a trends after wastewater treatment plant in Izmir Bay (Eastern Aegean Sea). Journal of Animal and Veterinary Advances 11: 113–123. Thomas CM, Perissinotta R & Kibirige I (2005). Phytoplankton biomass and size structure in two South African eutrophic, temporarily open/closed estuaries. Estuarine, Coastal and Shelf Science 65: 223–238.
• Wood RD 1975. Hydrobotanical Methods. London: University of Park Press.