Relationships among cyanobacteria, zooplankton and fish in sub-bloom conditions in the Sulejow Reservoir

Abstract

The occurrence of cyanobacteria is particularly characteristic of shallow eutrophic waters, and they often form massive 'blooms' that can affect aquatic invertebrates and fish. However, even a low abundance of cyanobacteria can be hazardous to aquatic organisms, due to the production of toxic metabolites. The aim of this study was to investigate the relationship between cyanobacteria and their toxicity (biological activity) towards zooplankton and fish communities, when only low concentrations of cyanobacterial chlorophyll a (less than 20 μg L -1 ) are detected, i.e. in sub-bloom conditions. Measurements were performed in Sulejow Reservoir (Central Poland), a shallow, lowland, eutrophic reservoir, in which cyanobacterial blooms occur regularly. Fish were assessed using echo-sounding (distribution) and by gillnetting (species composition). Simultaneously, zooplankton, cyanobacteria and physicochemical characteristics were studied at 14 stations situated along hydroacoustic transects. Parameters that characterized the cyanobacteria (cyanobacterial chlorophyll a concentration, the number of 16S rRNA and the mcyA gene copies and microcystin (MC) concentration) were consistently correlated (based on a principal component analysis), and the highest values were found in the downstream region of the study area. This 'cyano-complex' was also positively correlated with oxygen concentration, pH and phosphate levels, but was negatively correlated with temperature and the concentrations of nitrates and nitrites. In Sulejow Reservoir in 2013 the biomass of large zooplankton filter feeders decreased along with increasing MC concentration and fish densities, while small filter feeders did not present such relationships with regards to fish densities. Fish abundance tended to decrease at stations with a lower abundance of cyanobacteria and with growing toxic genotype copies and MC concentration.

Relationship between fish assemblage and angler catch in the Sulejów Reservoir, central Poland, in the context of a warming climate

“…The development and spatial distribution of cyanobacteria could influence anglers in a different manner. A few studies have indicated that fish might avoid areas with high cyanobacterial concentrations (Kaczkowski et al., ; Wojtalik, Godlewska, Frankiewicz & Zalewski, ), resulting in lower fishing success or changes in catch composition, consequently influencing the satisfaction and willingness of anglers (Arlinghaus, ; Finn & Loomis, ; Post et al., ). More likely, parts of the reservoir infested by cyanobacteria might be less attractive for anglers due to aesthetic reasons, such as an unattractive smell and colour of water (Hunt et al., ; Ignatius & Haapasaari, ).…”

The effect of potentially toxic cyanobacteria on ciliates (Ciliophora)

“…Immediately after sampling, 1-l samples of water containing cyanobacteria (samplings were done at the same places and time as was done while gathering the cyanobacteria biomass), and 1-l samples of water from the Planktothrix culture were filtered through Whatman filters GF/C. For a detailed description of the method and equipment used for the analysis, see Kaczkowski et al (2017).…”