Rare occurrence of nine Microcystis species (Chroococcales, Cyanobacteria) in a single lake – Lake Dojran, Macedonia

Svetislav Krstić, Boris Aleksovski and Jiří Komárek

CYANOCOST MEETING and CONFERNECE AMSTERDAM SEPTEMBER-OCTOBER 2016

Location – Lake Dojran, River Vardar and the Thessaloniki bay visible

1

sampling sites in 2015 A bit of history until 1988 Stable eutrophic system rich in biodiversity and productivity – the most productive lake for fish in SE Europe With a unique fishing tradition THE CATASTROPHY STARTS IN 1988 Almost 20 million m3 of water was removed from the lake in 1988 for the irrigation purposes. The lake level dropped immediately for 60 cm and more than 7 m in the following years

Gjesovska, 2013 THE CONSEQUENCES MASSIVE DEVELOPMENT OF Gloeotrichia natans in 1990/1991 THE CONSEQUENCES MASSIVE EXTINCTION OF BOTTOM DWELLING FAUNA 1994/95 THE CONSEQUENCES MASSIVE PROLIFERATION OF DINOFLAGELLATES (the lake turned red) 1996-98 THE CONSEQUENCES MANY CHANGES IN PHYTOPLANKTON COMPOSITION AND DOMINANCE RECORDED OVER THE YEARS

Phytoplankton composition in Lake Dojran in the last 20 years. a) 1995: Domination of Aulacoseira granulata. Occasional presence of Planktolyngbya contorta, Raphidiopsis mediterranea, Pediastrum boryanum, Microcystis sp. (poor presence) and Staurastrum sp. b) 1997: In May, a clear domination of the zooplankton. In the frame of the phytoplankton, tree species have shown co- dominance: Planktolyngbya contorta, Aulacoseira granulata and Ceratium monoceras. Poor presence of Microcystis sp. in association with Pediastrum boryanum, Ceratium hirundinella and Melosira varians. In July, a clear domination of Microcystis spp. with Aulacoseira granulata was observed. Presence of Raphidiopsis mediterranea and Planktolyngbya contorta. c). 2008: domination of Dolichospermum aff. flos-aquae. d). 2015: clear domination of Microcystis spp. (Scale bar = 50 μm) (Krstić et al., 2016)

THE MAIN REASON FOR THE CHANGES IN PHYTOPLANKTON COMMUNITIES CONSTANT AND GRADUAL DETERIORATION OF THE WATER QUALITY PARAMETERS – ACCELERATED EUTROPHICATION

Minimal values for D.O and Secchi depth and maximal values of pH, total P and total N recorded in Dojran lake for the presented years

10 9 8 7 6 5 4 3 2 1 0 D.O. (mg/L) pH Secchi depth (m) Total P (mg/L) Total N (mg/L)

1971 1974-75 2004-2005 2015

Lines and arrows depict treshold values for poor ecological status. AND THE ULTIMATE RESULT TOTAL DOMINANCE OF MICROCYSTIS SPP. IN THE LAKE WITH OBVIOUS IMPACT ON BIOTA A TOTAL OF NINE MICROCYSTIS TAXA WERE RECORDED IN PARALLEL COEXISTANCE – USUAL DOMINANCE OF a. Microcystis aeruginosa; b. M.aeruginosa and M.protocystis Microcystis botrys; c. Microcystis botrys, detail of mucilage; d. Microcystis flos-aquae; e. Microcystis ichtyoblabe, general view of colony; f. Microcystis ichtyoblabe; g-h. Microcystis novacekii; i. Microcystis protocystis; j. Microcystis smithii; k-m. Microcystis viridis; n-o. Microcystis wesenbergii. All microphotographs (except the ones on panel c. and panel e. that depict special details of mucilage and colony form) were taken under total magnification of ×345 and on colonies stained with china ink (exception are microphotographs on panel e. and panels k-l. because china ink staining masks several diacritical characters of the types – most notably the refractive margin of M. viridis that is better visible without staining). PRELIMINARY RESULTS OF MC-LR ANALYSES Dissolved MC-LR Coincidences with domination of species concentration (µg/L) Domination of zooplankton; in the frame of the phytoplankton Site 1 2.84 1st co-dominance of M.protocystis and M. aeruginosa sampling Domination of zooplankton and Sphaerocystis, low % of Site 2 1.5 (May Microcystis spp. 2015) Domination of Sphaerocystis sp., low abundance of Microcystis Site 3 0.528 spp. Co-domination of Aphanizomenon gracile, M. protocystis and M. Site 1 1.25 ichtyoblabe. Presence of the endogloeic Pseudanabaena mucicola Clear domination of M. ichtyoblabe, M. protocystis is 2nd Site 2 0.608 subdominant. All the rest are poorly present. High presence of sampling the endogloeic Pseudanabaena mucicola (July Domination of the zooplankton (because of the massive 2015) presence of the Dreissena sp. larvae), but quite rich with Site 3 1.45 Microcystis spp. M. protocystis shows dominance and M. ichtyoblabe is subdominant. High presence of the endogloeic Pseudanabaena mucicola 2010 Krstić S. Water blooms by M. aeruginosa and M.flos-aquae 270.0 (2011)

Conclusions Seasonal investigations on Lake Dojran during 2015 on presence, dominance, successions and toxin production of Microcystis spp. have enabled the following conclusions: • Lake Dojran has been confirmed as eu-hypereutrophic lake with parameters which are indicative for an increased or accelerated eutrophy over the sampling period spring- autumn; • A total of nine Microcystis taxa have been observed in co-existence (M.aeruginosa, M.botrys, M.flos-aquae, M.ichthyoblabe, M.novacekii, M.protocystis, M.smithii, M.viridis and M.wesenbergii), which have successively changed in the dominance over the investigated period. M.protocystis, M.ichthyoblabe and M.aeruginosa have been found as the most dominant species in the lake. This is the first report of presence of nine separate Microcystis taxa in a single lake, according to literature data. We report for the first time the presence of Microcystis protocystis, a pan-tropical species, in a European lake; • Elaborated results point out the necessity to change the accepted morphospecies concept into separation of Microcystis taxa as distinct species which are clearly delimited according to their constant morphological features. These might be a consequence of genetic constitution or a symbiosis with multiple heterotrophic bacteria. Nevertheless, the co- existence of all nine morphologically different species in a single lake strongly corroborates their distinctive species characters; • Toxicity analyses demand for a specific and targeted investigation, since the toxin production and presence depends on many factors, and the toxin dynamics including the highest peaks may be easily overlooked if other issues are in the focus of the performed monitoring. THANK YOU FOR YOUR KIND ATTENTION