Seasonal variation and occurrence of algal turf community in Lake Ladik, Turkey.

The composition and seasonal variation of the algal turf of Lake Ladik were studied using samples collected from one station between June 2000 and May 2001. 50 taxa of diatoms were identified in the epiphyton. Navicula veneta, N. halophila, Nitzschia fonticola and Aulacoseira distans were particularly important on turf community. During the October month several Navicula species become progressively more important. Gomphonema lateripunctatum was particularly notable. Other diatoms were occasionally abundant, including Cymbella affinis, C. silesiaca, Navicula cryptocephala, Gomphonema olivaceum and Cyclotella ocellata. Also Navicula lanceolata and Anomoeoneis brachysira were conspicuous, owing to their large size, but were never numerically abundant. Fragilaria ulna and Nitzschia palea were found in low numbers in study area and this pointed out there has not been a remarkable abundance of algal pollution in Lake Ladik. The associations between July and August with bonds to June, January and February with bonds to April were most significant in the study period obtained by cluster analysis. Shannon diversity and evenness presented small variations during the study period. Lake Ladik presented low values of species richness particularly during summer period and highest values were recorded in April. According to canonical correspondence analysis, there was association between some Navicula and Nitzschia species with PO4-, NH3-N. Also the multivariate analysis showed, temperature as the most important factor in the distribution and abundance of diatoms on turf biomass.

Seasonal succession and diversity of phytoplankton in a eutrophic lagoon (Liman lake).

The seasonal succession, composition and diversity of phytoplankton in a eutrophic lagoon (Liman lake) were studied between January 2002 and November 2003. Samples were collected from surface water and deeper (1m depth) at stations and species diversity (Shannon-Weaver, H) and evenness were calculated. Shannon Diversty was similar at Station 1 and Station 2. Minimum and maximum diversity values (0.101 and 0.765 bits.mm-3) were recorded in June and July 2003 at Station 2. Cluster analysis and NMDS (Non metric multidimensial scaling) were applied to the phytoplankton community. The lagoon exhibits high conductivity (7211-10757 1Scm-1), mean temperature of 17.7oC, varying concentrations of dissolved oxygen (3.3-8.4 mgl–l). Light, temperature, rainfall, turbidity and salinity were expected to be the main factors affecting the seasonal succession. The seasonal succession of phytoplankton were similar at surface water and 1m depth. A total of 130 taxa belonging to Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Dinophyta, Xantophyta, Chrysophyta and Cryptophyta divisions were identified. Pseudanabaena limnetica, Kirchneriella obesa, Kirchneriella lunaris, Ankistrodesmus falcatus and Ankistrodesmus spiralis were highly represented.