Naslov
Plankton and nutrients in Lake Vlaška (Neretva River estuary, SE Adriatic Sea)

Autori
Jasprica, Nenad ; Carić, Marina ; Kršinić, Frano

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of Extended Abstracts of the Symposium Eutrophication in the coastal zone of the eastern Adriatic Sea / Wassmann, Paul ; Ćosović, Božena - Zagreb : Norwegian Research Council, 2005, 37-39

Skup
Eutrophication in the coastal zone of the eastern Adriatic Sea

Mjesto i datum
Hvar, Hrvatska, 27.04.2005. - 01.05.2005

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
plankton; nutrients; the Neretva River estuary

Sažetak
Lake Vlaška is located at the freshwater and saltwater interface, and more productive than either the freshwater lakes in upper Neretva river (Jasprica & al. 2005) or the sea bordering them (Viličić 1984).Estuarine circulation has been shown to be responsible for the distribution of hydrographic factors in Lake Vlaška. Low freshwater discharge, decreased inflow seawaters, strong vertical stratification, as well as decompositon of organic matters were the main causes responsible to hypoxia during summer-autumn period. Freshwater sources enriched Lake Vlaška with nutrients. The highest concentrations of most nutrients were observed in summer-autumn period. The autumn concentrations of nutrients could be due to the freshwater discharge which well agreed with low salinity and heavy rainfall in November-December (Croatian Meteorological and Hydrological Service, 1999-2000). This agrees with findings of Štambuk-Giljanović (2003). Generally, the summer peak of SiO4 coincided with the diatom bloom (Chaetoceros spp., Pseudo-nitzschia spp., Nitzschia longissima). The diatom community consisted mainly of taxa that are typical for summer bloom in South Adriatic coastal waters (Jasprica & Carić 2001). On the contrary, rapidly decrease of SiO4 in October well agreed with a bloom of Skeletonema costatum. This species has higher growth rate and nitrate uptake rate, and can adapt to lower salnity compared to many diatom species (Liu et al. 2005). The maximum of PO4 can be attributed by excretion of dense population of non-loricatae ciliates in August. NH4 gave the highest proportin of TIN. This could be explained by reduction of NO3 related to hypoxia in the bottom layer. In general, the microphytoplankton succession pattern of Lake Vlaška agrees with the general succession pattern suggested by Margalef (1958), and can be divided into three stages: Stage I characterized by fast-growing, small-celled diatoms ; Stage II involving the occurrence of a community of larger diatoms with lower growth rates ; and Stage III determined by the presence of large dinoflagellates with still lower rates. The most abundant dinoflagellate species Scrippsiella trochoidea is very common in moderately eutrophic waters. The study on cysts from sediments would be helpful for understanding of the population dynamics of these species. The main feature of phytoplankton assemblages is the simultaneous dominance of more than one species. The reason for this can be found in the very frequent and rapid changes in the environmental conditions of this dynamic ecosystem.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA