Phytoplankton abundance and structural parameters of the critically endangered protected area Vaya Lake (Bulgaria)

Abstract

Vaya (Ramsar site, protected area and Natura 2000 site) is the biggest natural lake in Bulgaria and the shallowest Black Sea coastal lake, which during the last decades has undergone significant changes and was included as critically endangered in the Red List of Bulgarian Wetlands. Our studies were conducted during the summer and autumn months of three years – 2004–2006. The paper presents results on the phytoplankton abundance (numbers, biomass and carbon content) in combination with the indices of species diversity, evenness and dominance. Phytoplankton abundance was extremely high (average values of 1135 × 106 cells/L for the quantity and of 46 mg/L for the biomass) and increased in the end of the studied period (years 2005–2006), when decrease of species diversity and increase of the dominance index values were detected. The carbon content of the phytoplankton was at an average value of 9.7 mg/L and also increased from 2004 to 2006. Cyanoprokaryota dominated in the formation of the total carbon content of the phytoplankton, in its numbers (88%–97.8%), and in the biomass (62%–87.9%). All data on phytoplankton abundance and structural parameters in Vaya confirm the hypertrophic status of the lake and reflect the general negative trend in its development.

Assessment of cyanoprokaryote blooms and of cyanotoxins in Bulgaria in a 15-years period (2000-2015)

“…The contribution of the cyanoprokaryotes to the total phytoplankton biomass in different WBs and in different sampling periods ranged from 0 to 100%, with values exceeding 65-75 mg L -1 in summer periods (e.g., in the coastal lake Vaya -Stoyneva, 2003;Pavlova et al, 2006Pavlova et al, , 2007Dimitrova et al, 2014a) and reaching 95.9 mg L -1 in average for the period 2010-2014 (this study). The assessment of the average cyanoprokaryote biomass in 61 WBs from the dataset shows that in four sites (the lakes Vaya and Blato Srebarna, and the reservoirs Mandra and Tri kladentsi), its values were over WHO's (2003) threshold for medium health risk category (10 mg L -1 ) in recreational waters and in five other (the lakes Durankulashko ezero and Ezero Momin brod, and the reservoirs Asparuhov val, Chirpan and Pchelina) from the rest 57 WBs, they were over the low health risk category threshold (2 mg L -1 ), as they were re-estimated from cell numbers in biomass values by Mishke et al (2011).…”

“…4). Due to their high importance for conservation of rare and threatened species of national, European and global significance (Michev and Stoyneva, 2007;Vassilev et al, 2013), these two shallow lakes have been intensively studied before and during the analyzed period, and always have been outlined for their rich algal diversity (Michev et al, 1998;Stoyneva, 1998aStoyneva, , 1998bStoyneva, , 2003Stoyneva, , 2014Stoyneva, , 2015Georgiev, 2012;Dimitrova et al, 2014aDimitrova et al, , 2014b. However, the same authors outlined the negative trends in their development with enhanced eutrophication, cyanoprokaryote blooms (incl.…”

“…This study compiles and evaluates the currently available data on phytoplankton and relevant environmental data on Bulgarian WBs (mainly reservoirs and lakes) gathered during the period 2000-2015 (Stoyneva, 2003(Stoyneva, , 2010(Stoyneva, , 2014(Stoyneva, , 2015Beshkova and Botev, 2004;Kalchev et al, 2004;Traykov, 2005;Pavlova et al, 2006Pavlova et al, , 2013aPavlova et al, , 2014Pavlova et al, , 2015Beshkova et al, 2008aBeshkova et al, , 2008bBeshkova et al, , 2012Pavlova, 2007;Tsanev and Belkinova, 2008;Teneva et al, 2009Teneva et al, , 2010aTeneva et al, , 2010bTeneva et al, , 2011Teneva et al, , 2014Cheshmedjiev et al, 2010aCheshmedjiev et al, , 2013Stoyanov et al, 2012Stoyanov et al, , 2013Stoyanov et al, , 2016Stoyanov, 2014Stoyneva et al, 2013Belkinova et al, 2014;Dimitrova et al, 2014aDimitrova et al, , 2014bDochin andStoyneva, 2014, 2015;Dochin, 2015;Georgieva et al, 2015).…”

“…The lake Vaya is the only WB for which the total carbon content was estimated (Dimitrova et al, 2014a). Its mean value of 9.7 mg L (Traykov, 2005;Cheshmedjiev et al, 2010a;Stoyanov et al, 2012;Belkinova et al, 2014;Stoyneva, 2014) (Fig.…”

Figure 1 from: Teneva I, Belkinova D, Mladenov R, Stoyanov P, Moten D, Basheva D, Kazakov S, Dzhambazov B (2020) Phytoplankton composition with an emphasis of Cyanobacteria and their toxins as an indicator for the ecological status of Lake Vaya (Bulgaria) – part of the Via Pontica migration route. Biodiversity Data Journal 8: e57507. https://doi.org/10.3897/BDJ.8.e57507

“…Studies, related to the hydrobiological and hydrochemical parameters of Lake Vaya were performed for samples collected in the period 2004(Dimitrova et al 2014aDimitrova et al 2014b), as well as in 2017 (Agafonova 2018). HPLC analyes of water samples from Lake Vaya, collected in 2004, showed the presence of microcystin-LR .…”