Cvetanje cijanobakterija, prisustvo cijanotoksina i njihov uticaj na ribe u pojedinim jezerskim ekosistemima Srbije i Mađarske

Abstract

U poslednjih nekoliko decenija, usled antropogenog efekta dolazi do narušavanja kvaliteta vode i eutrofizacije mnogih slatkovodnih ekosistema. U uslovima povećane koncentracije nutrijenata u vodi dolazi do prenamnožavanja cijanobakterija koje se naziva cvetanje cijanobakterija. Cilj ovog rada je bio ispitivanje pojave cvetanja cijanobakterija, produkcije cijanotoksina i uticaja ovih toksina na ribe u odabranim ekosistemima Srbije i Mađarske. Loš kvalitet vode i povećane koncentracije azotnih i fosfatnih jedinjenja detektovani su na jezerima Ludaš, Kiš-Balaton i Fehervarčurgo, dok je voda jezera Balaton bila boljeg kvaliteta. U jezerima Ludaš, Kiš-Balaton i Fehervarčurgo je došlo do intenzivnog cvetanja cijanobakterija gde je broj ćelija po mililitru u pojedinim mesecima iznosio i po nekoliko miliona. Najdominantniji taksoni su bili predstavnici rodova Microcystis, Aphanizomenon i Dolichospermum. Mikrocistin- i saksitoksin-kodirajući geni su amplifikovani u biomasi cijanobakterija sva četiri analizirana jezera ukazujući na postojanje toksičnih sojeva cijanobakterija. Različite strukturne varijante mikrocistina su izmerene u jezerima Ludaš, Kiš-Balaton i Fehervarčurgo, dok u jezeru Balaton ovi toksini nisu detektovani. Cilindrospermopsin nije kvantifikovan ni u jednom analiziranom jezeru. Takođe, akumulacija cijanotoksina nije izmerena u tkviima riba ni jednog od analiziranih jezera. Ribe izlovljene iz jezera Ludaš i Kiš-Balaton su pokazale značajna oštećenja jetre, bubrega i škrga, dok su oštećenja ovih organa kod riba iz jezera Fehervarčurgo i Balaton bila manja. Ribe izlovljene iz jezera Kiš-Balaton tokom juna 2019. godine su takođe pokazale promene u aktivnosti enzima biotransformacije, kao i povećanu lipidnu peroksidaciju i promene u aktivnosti antioksidativnih enzima ukazujući na oksidativni stres. Podaci prikupljeni tokom izrade ove doktorske disertacije ukazuju na intenzivno cvetanje cijanobakterija na jezerima Ludaš, Kiš-Balaton i Fehervarčurgo, kao i na potencijalnu opasnost i negativne efekte na zdravnje organizama izloženih cvetanju cijanobakterija u ovim ekosistemima, te su dalji monitoring, a potencijalno i sanacija ovih jezera potrebni u budućnosti.

In the last several decades, an intense deterioration of water quality followed by subsequent eutrophication is occurring in many freshwater ecosystems due anthropogenic effects. Conditions of highened nutrient concentrations and eutrophication cause intense cyanobacterial proliferations termed cyanobacterial blooming. The aim of this study was to investigate cyanobacterial blooming, potential cyanotoxin production and their effects on fish in four select ecosystems of Serbia and Hungary. Poor water quality and higher concentrations on nitrogen and phosphorus compounds were observed in lakes Ludaš, Fehérvárcsurgó and Kis-Balaton, while the water quality of Lake Balaton was better. Intense cyanobacterial blooms occurred in these three lakes with the numbers of cyanobacterial cells/ml being several million during some months. The most numerous taxa belonged to genera Microcystis, Aphanizomenon and Dolichospermum. Microcystin- and saxitoxin-coding genes were amplified in the biomass of all four lakes indicating a presence of potentially toxin-producing strains. Different microcystin structural variants were detected in lakes Ludaš, Fehérvárcsurgó and Kis-Balaton, while these toxins were not quantified in Lake Balaton. Cylindrospermopsin was not detected in any of the analyzed lakes. Additionally, toxins were not accumulated in fish tissues in any of the analyzed lakes. Fish sampled from lakes Ludaš and Kis-Balaton displayed severe histopathological alterations of liver, kidney and gills, while these alterations were milder in fish from lakes Fehérvárcsurgó and Balaton. Fish sampled from Lake Kiš-Balaton in june of2019. displayed alterations in the activity of detoxication enzymes, as well as lipid peroxidation and alterations in the activity of antioxidant enzymes indication that these fish were under oxidative stress. Results obtained during this study demonstrate intense cyanobacterial blooming in lakes Ludaš, Fehérvárcsurgó and Kis-Balaton, as well as potential danger and negative effects that such blooming can cause in organisms that are in contact with these ecosystems. Therefore, further monitoring, and potentially sanation, of these ecosystems is imperative in the future.