Relationship of Epilithic Diatom Communities to Environmental Variables in Yedikir Dam Lake (Amasya, Turkey)

WOS: 000422959000002In order to evaluate the composition and seasonal variations of the epilithic diatoms in Yedikir Dam Lake were studied using samples collected from the stones in the barrier area between November 2004 and April 2006. The diatom communities were diverse; 88 taxa were found, belonging to the Bacillariophyta. Cymbella minuta, Cyclotella ocellata and Encyonema silesiacum have become the most abundant organisms in the epilithon. Environmental variables together with biological data obtained during the monthly routine biomonitoring of epilithic samples in the dam were analysed to understand variability of epilithic diatom communities and their relationships with environmental variables. Moreover, cluster analysis was applied to the epilithic algal communities and the seasonal variations of the samples were classified according to their similarity levels. Speciess richness and shannon diversity of the samples which were counted were measured in monthly periods. The results of the diversity analysis and the counting did not exactly match up with each other. Multivariate analyses indicated that both the regional distribution and seasonal variation of some epilithic diatoms (e.g. Cymbella spp., Nitzschia spp., Amphora delicatissima) are mainly driven by nutrient concentrations. Furthermore, epilithic diatoms are predominantly affected by geochemical characteristics including pH and total alkalinity (CaCO3) levels

New Diatom Records for Turkish Freshwater Algal Flora from Lakes Ladik (Samsun, Turkey) and Hazar (Elazig, Turkey)

WOS: 000422952500012The majority of phycological studies in Turkey focus on seasonal changes of phytoplankton and phytobenthos in lentic and lotic systems, while very few studies related to counting diatoms in sediment cores obtained as a result of paleolimnological work have been published. In this paleolimlogical study, seventeen (14+3) new diatom records for freshwater algal flora of Turkey were determined on sediment core samples at five different locations collected in July 2006 from Lakes Ladik (Samsun) and Hazar (Elazig). We recorded seventeen diatom taxa belonging to Naviculales (8), Cymbellales (2), Eunotiales (2), Bacillariales (2), Fragilariales (1), Tabellariales (1) and Aulacoseirales (1) orders from Lakes Ladik (Samsun) and Hazar (Elazig). All of the reported taxa are new records for freshwater algal flora of Turkey. General information on the morphology and taxonomy of the species are briefly described in this paper, with their illustrations

Evaluation of ecological changes in lake hazar (Elazig, Turkey) using diatom-based paleolimnological techniques

© 2020 Parlar Scientific Publications. All rights reserved.Sediment core samples (H002, H003, H005 and H006) recovered from the basin of Lake Hazar located in the South East Region of Turkey. Core sam¬ ples were collected from the four sampling stations by UWITEC corer to determine diatom flora distri¬ bution in Lake Hazar. Diatom counts and identifica¬ tions were made from the sediments sampled at 1-2 cm intervals. Total of 142 species of diatoms were recorded, most of them were pennate diatoms. Ulnaria ulna, Nitzschia gracilis, Synedra nana, and Cyclotella ocellata dominated the assemblage in the sampling points. Our objective was to investigate the environmental and ecological history of Lake Hazar, and to recover diatom microfossil profils using paleolimnological techniques

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains

Data Descriptor: A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment