Ecological assessment of Burç Reservoir's surface water (Turkey) using phytoplankton metrics and multivariate approach


Abstract: The present study aimed to elucidate relationships between phytoplankton species and stressors using multivariate approaches and assess the environmental condition of Burç Reservoir?s surface water using phytoplankton metrics from September 2018 to August 2019 according to implementations of the Water Framework Directive. Burç Reservoir had a characteristic of a warm monomictic pattern. Phytoplankton functional groups (E, F, J, LO, LM, MP , P, S1 , T, and W1 ) were found in the reservoir. A significant difference was found in total biovolume values changed from 2.28 mm3 /L in November 2018 to 0.51 mm3 /L in February 2019. The first two axes of canonical correspondence analysis explained 99.2% of relationships between stressors and phytoplankton assemblages. Explanatory factors such as electrical conductivity (EC), nitrate (NO3 -N), total nitrogen (TN), water temperature, calcium (Ca+2), precipitation, total organic carbon (TOC), ortho-phosphate (o-PO4 ), and total phosphorus (TP) significantly drove the spatiotemporal distribution of phytoplankton. Weighted average regression resulted that phytoplankton species such as Gymnodinium saginatum, Snowella lacustris, Ceratium hirundinella, and Pseudanabaena limnetica were closely associated with high TP, while Fragilaria capucina, Navicula trivialis, Cymbella aspera, Ulnaria biceps, Nitzschia palea, and Pseudopediastrum boryanum closely related to the EC. Carlson's trophic state index indicated that Burç Reservoir mainly has a eutrophic characteristic with the assessment of chlorophyll a, total phosphorus, and Secchi disk depth, while it had a eu-hypertrophic according to the OECD classification. Results of the modified PTI-phytoplankton trophic index (mean = 2.37), the Med-PTI Mediterranean phytoplankton trophic index (mean = 1.96), and the Q assemblage index (mean = 2.58) indicated a moderate ecological status of Burç Reservoir. The present study confirmed that phytoplankton assemblages are closely integrated with the environmental condition of Burç Reservoir, which could be assessed by using the PTI and Med-PTI.

Keywords: Bio-assessment, biomonitoring, canonical correspondence analysis, phytoplankton trophic index, water quality

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