The effect of environmental factors on the growth and size structure of two dominant phytoplankton species in Buyukcekmece Reservoir (Istanbul, Turkey)

The aim of this study was to investigate seasonal variability in the growth and size structure of dominant phytoplankton species in Buyukcekmece Reservoir, and to determine the environmental factors that affect morphological plasticity in those dominant species. In total, 78 taxa from 8 algal divisions were identified. Bacillariophyta and Chlorophyta were the most important divisions with respect to Species number, but cryptomonads Plagioselmis nannoplanctica (Skuja) Novarino, Lucas, and Morrall, and a Cryptomonas sp. were dominant in terms of density and biomass. P nannoplanctica was the major contributor of biomass in the reservoir. A significant difference in Plagioselmis species biovolume was observed between winter-early spring and summer. A significant negative correlation was observed between its seasonal size structure and abundance. During winter (December 2004-April 2005) nutrient values were higher than during autumn (October-Novermber 2005) and P. nannoplanctica had maximum cell size (17.5 mu m x 10 mu m; biovolume: 589.5 mu m(3)), but its abundance was very low (< 6 cells x 10(-3) l(-1)). The minimum surface:volume ratio (SA/V:87) was recorded in this period. Among the measured environmental factors, water temperature was the only parameter that had a statistically significant negative relationship (R-2:0.635; P < 0.01) with P. nannoplanctica cell size. The results indicate that seasonal changes in cryptomonad size structure were controlled by water temperature

Predicting the effects of sediment based internal nutrient loads on eutrophication in Kucukcekmece Lagoon for rehabilitation planning

In deep stratified coastal lagoons, hypoxic waters that result from phytoplankton decomposition in the stratified bottom waters are often associated with eutrophication. Decomposing biomass reaches the bottom sediments and enriches them with nutrients and organic matter. Nutrients trapped in sediments are released with time and promote excessive phytoplankton growth in the surface water. Because eutrophication in lentic ecosystems progresses in a self-fuelling cycle, outflow is the only available process for exporting excess nutrients to recover from eutrophication. Thus, rehabilitation of eutrophic coastal lagoons that have limited seawater interactions is a long term process. The importance of nutrient release from sediments on eutrophication and the delay effect of internal nutrient loading on the rehabilitation of a eutrophic coastal lagoon with limited seawater exchange were analysed in this study. An ecological model that couples the water column and the sediment diagenesis processes, was developed for water quality management purposes. Our findings indicate that the recovery of the Lagoon from eutrophication will be taken decades even in the absence of external nutrient loading. Therefore, we suggest applying rehabilitation strategies that control the nutrient fluxes from sediments for a faster recovery from heavily eutrophic conditions. Land-based nutrient sources must also be controlled because they feed water column and the bottom sediments with nutrients. (C) 2017 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. Published by Elsevier B.V. All rights reserved

Planktothrix rubescens: a perennial presence and toxicity in Lake Sapanca

Cyanobacteria are expected to adjust to new conditions better than other primary producers since they have a long history of adaptation as one of the first organisms on earth. Their ecophysiological adaptations differ widely among cyanobacterial species. As a stratified species, P. rubescens forms a population in the metalimnion during summer months in lakes with clear water and disperses in the whole water column during the period. However, after a dry season in 2006 and 2007, a prolonged surface bloom in late winter was observed in Lake Sapanca The maximum biomass of P. rubescens reached 13.9 mg L-1 in surface water in February 2007 and microcystin concentrations varied between 0.12 and 8 mu g L-1 MC-LR equiv. in the open water throughout the year. The maximum microcystin value was measured at 79 mu g L-1 when accumulations of filaments were observed on the shoreline. As P. rubescens is a shade-adapted species, lower insolation in February together with stable water conditions and lower water temperature promoted the surface bloom. In conclusion, the presence of toxic P. rubescens throughout the year with changing depths poses severe health hazards to people and also an economic burden to the water treatment facility, since the lake is used as a drinking-water reservoir

Planktothrix rubescens: a perennial presence and toxicity in Lake Sapanca

Cyanobacteria are expected to adjust to new conditions better than other primary producers since they have a long history of adaptation as one of the first organisms on earth. Their ecophysiological adaptations differ widely among cyanobacterial species. As a stratified species, P. rubescens forms a population in the metalimnion during summer months in lakes with clear water and disperses in the whole water column during the period. However, after a dry season in 2006 and 2007, a prolonged surface bloom in late winter was observed in Lake Sapanca The maximum biomass of P. rubescens reached 13.9 mg L-1 in surface water in February 2007 and microcystin concentrations varied between 0.12 and 8 mu g L-1 MC-LR equiv. in the open water throughout the year. The maximum microcystin value was measured at 79 mu g L-1 when accumulations of filaments were observed on the shoreline. As P. rubescens is a shade-adapted species, lower insolation in February together with stable water conditions and lower water temperature promoted the surface bloom. In conclusion, the presence of toxic P. rubescens throughout the year with changing depths poses severe health hazards to people and also an economic burden to the water treatment facility, since the lake is used as a drinking-water reservoir

Zooplankton Biodiversity in Reservoirs of Different Geographical Regions of Turkey: Composition and Distribution Related with Some Environmental Conditions

The zooplankton fauna and the relationship with their environmental variables were investigated on the epilimnion layer of the seven reservoirs (Demirdoven, Devegecidi, Menzelet, Sir, Omerli, Porsuk, Tahtali) of different regions (Marmara, Aegean, Mediterranean, Central Anatolia, Eastern Anatolia, Southeastern Anatolia) throughout the summer months (2015) in Turkey. According to the trophic conditions reservoirs varied between oligo-and eutrophic status. Chlorophylla concentration, measured for the estimation of primary production, was determined considerably high along the investigation period. A total of 62 zooplankton species were identified with the contribution of 44 rotifers, nine cladocerans and nine copepods. Except one reservoir, all of the others were dominated by rotifera group, and also in each study site dominant taxa were changed at species level. On the other hand common dominant taxa for all reservoirs was the rotifer Polyarthra vulgaris Carlin, 1943 with 95 % frequency. In terms of zooplankton species, most of the studied reservoirs showed less than 50% similarities, due to their different limnological conditions and different geographic locations. Reservoirs in high trophic conditions in the present study were represented by low species diversity. Water quality in the reservoirs with respect to biological data were determined as beta-mesosaprobic. The using limnological and biological indices to determine water quality were consistent. Densities of main zooplankton groups, and also frequent species of the reservoirs correlated with epilimnion layer depths and total phoshorus concentrations significantly. On the other hand rotifera variation was affected mainly by physical variables (pH, temperature, dissolved oxygen concentration, conductivity), and crustacean variations were related with total phoshorus. The comperative assessment between limnological variables and zooplankton community in this reservoirs was studied for the first time

DISTRIBUTION OF TOXIC CYANOBACTERIA AND CYANOTOXINS IN TURKISH WATERBODIES

The increase of toxic cyanobacterial blooms in aquatic ecosystems posing threat to human health has caused countries to establish monitoring strategies and set limit values in their regulations. The frequency of toxic cyanobacterial blooms increase in Turkey as a result of deterioration of water resources. In order to investigate the problems arising from cyanobacteria and cyanotoxins, the 'SIYANOTOKS' Project was carried out by the Ministry of Forestry and Water Affairs, General Directorate of Water Management in cooperation with Istanbul University Faculty of Fisheries. Within this scope, the Project has been carried out to monitor cyanobacteria and their toxins in 18 selected waterbodies: 7 natural lakes, 8 reservoirs, 1 lagoon and 2 coastal and transitional waters in Turkey. Samples were collected between May to October 2015 in monthly intervals and two samples were taken in winter 2015 and Spring 2016. Potentially toxic cyanobacteria species were detected in 14 waterbodies and blooms were observed in 57% of them. A highest concentration of Microcystin-LR eq. was 29.7 mu g/l and cylindrospermopsin was 9 mu g/l. These results showed that cyanotoxin problems are very common in Turkish surface waters and regulation in drinking and recreational waters should be implemented