Massive fish mortality and Cylindrospermopsis raciborskii bloom in Aleksandrovac Lake

Abstract

This paper presents a case study of a massive fish mortality during a Cylindrospermopsis raciborskii bloom in Aleksandrovac Lake, Serbia in mid-December 2012. According to a preliminary investigation of the samples taken on November 6 before the fish mortalities and to extended analyses of samples taken on November 15, no values of significant physicochemical parameters emerged to explain the cause(s) of the fish mortality. No industrial pollutants were apparent at this location, and results excluded the likelihood of bacterial infections. Even after freezing, the dissolved oxygen concentration in the water was sufficient for fish survival. High concentrations of chlorophyll a and phaeophytin occurred in the lake, and phytoplankton bloom samples were lethal in Artemia salina bioassays. A bloom of the cyanobacterium C. raciborskii was recorded during November. Although the A. salina bioassays indicated the presence of toxic compounds in the cyanobacterial cells, the cyanotoxins, microcystins, cylindrospermopsin and saxitoxin were not detected.

Toxic cyanobacteria and cyanotoxins in European waters – recent progress achieved through the CYANOCOST Action and challenges for further research

“…in Greece and Russia (Kormas KA, Papadimitriou T, Chernova E: personal communications). An ongoing likelihood for the role of additional (or alternative) uncharacterised or novel cyanotoxins of health significance was provided in a further, major fish-kill in Serbia in which candidate cyanotoxins (CYN, STXs, MCs) were not detected although the C. raciborskii bloom material was lethal by bioassay using Artemia salina (Svirčev et al, 2016). It is evident that the range of health hazards presented by cyanobacteria and their metabolites is only partially understood.…”

Review of 130 years of research on cyanobacteria in aquatic ecosystems in Serbia presented in a Serbian Cyanobacterial Database

“…However, the most common cyanotoxins (MCs, cylindrospermopsin, and saxitoxin) were not detected. It is possible that some other unknown or undetected toxic metabolites of this cyanobacterium were present and were a potential cause of the fish mortality in Aleksandrovac (Drobac, 2015;Svirčev et al, 2016a).…”

A comparative study of the metabolic profiles of common nuisance cyanobacteria in southern perialpine lakes

“…A preliminary attempt aimed at identifying the peptidic compounds has revealed that anabaenopeptins and cyanopeptolins were the most represented, but many other peptides are still to be structurally determined. As demonstrated by recent reports (Svirčev et al, 2016), the toxic potential of cyanobacteria can be only partially verified by current analytical techniques. Efforts to develop more comprehensive but specific methodologies are therefore still needed.…”