Güllük Lagoon (Aegean Sea, Turkey) Ecosystems

Authors: ÖZDEMİR EGEMEN, ŞEVKET GÖKPINAR, MESUT ÖNEN, BAHA BÜYÜKIŞIK, BELGİN HOŞSUCU, UĞUR SUNLU, SEMRA CİRİK

Abstract: Güllük Lagoon has an area of 2500 decares with a depth of 0.5-5.0 m and is connected to Güllük Bay by a channel. In this study, samplings of phytoplankton and benthos were taken physico-chemical parameters were recorded monthly during 1993 at 5 stations. The temperature reached a minimum of 10.42°C in January and a maximum of 26.9°C in July, with a mean annual temperature of 19.53±1.511. The salinity in the lagoon ranged from 7.48 ‰ to 13.92 ‰ in January and March, respectively with a mean annual silinity of 10.65 ± 0.555. Dissolved oxygen in the sub-surface (0.25 m) water was 5.56 mg 1^{-1} in June and 9.06 mg l^{-1} in February, with an annual mean 7.31 ± 0.331. The Secchi-disk depth was 1.12 m in May and 2.40 m in October. Nutrient measurements revealed moderately high levels of ammonia (ranging from 4.39 to 29.70 µg-at l^{-1}), low nitrate (0.81 to 17.87 µg-at l^{-1}), nitrite (0.19 to 1.35 µg-at l^{-1}), phosphate (0.01 to 0.45 µg-at l^{-1}), and silicon (0.26 to 6.00 µg-at l^{-1}). Chlorophyll a distribution generally indicated that productivity was highest in May (21.49 mg l^{-1}) and lowest in September (0,77 mg l^{-1}). Melosira moniliformis was the predominant phytoplankton species. All of the stations were characterized by high species diversity. Identification of the benthic species was carried out with 60 samples collected from 5 stations in a of one year period. As result 68 benthi species belonging to 7 taxa (Nemertina, Polychaeta, Oligochaeta, Crustacea, Mollusca, Insecta, Echinodermata) were identified. The polychaetae were numerically dominated by Notomastus latericeus (3737 individuals), followed by Hediste diversicolor (1524 individuals), and Spionidae (sp) (1361 individuals). Economically important fish species in Güllük Lagoon consist of mullets (Mugil cephalus, M. capito, Chelon labrosus, Liza saliens), Sparus aurata (gilthead sea bream), Dicentrarchus labrax (sea bass), Solea solea (sole), Anguilla anguilla (eel) and Cyprinus carpio (carp), with an annuall yield varying from 10 to 69 tonnes.

Keywords: Güllük lagoon, physico-chemical parameters, planktonic and benthic organisms, fish productivity

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