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Oceanologia
|
2009
|
tom 51
|
nr 1
139-143
In April 2001 a local bloom of the heterokont phytoflagellate Pseudochattonella farcimen (Riisberg I., 2008) (initially named Chattonella aff. verruculosa) was observed for the first time in the southern part of the Gulf of Gdańsk. The species occurred in high cell densities: the count was 11.5×106 cells dm−3 and the biomass 927.5 μgC dm−3.
This study focused on site-specific preferences of potentially harmful cyanobacterium Gloeotrichia echinulata to occur in lakes with different ecological and trophic conditions. Its pelagic growth was studied in six lakes from June to September in 1986-1988, 2000-2001 and 2009. In total, 78 samples were taken from the epilimnion (stratified lakes) or the whole water column (non-stratified lakes). Analyses of phytoplankton and environmental variables were performed according to standard methods. During summer, a distinct maximum of the Gloeotrichia growth was observed in July or August (the warmest period). Bloom events of G. echinulata occurred in lakes where the light and oxygen conditions were significantly inferior while the phosphorus content remained on a slightly elevated level. The distinct domination of this cyanobacterium (above 40% of the total phytoplankton biomass) was limited to lakes with a high, moderate or even poor ecological status, and to the meso-eutrophic or eutrophic state of lakes. However, G. echinulata occurred in a broader range of ecological and trophic conditions of lakes. The historical approach to mass occurrence of G. echinulata, with its possible contribution to phosphorus translocation from sediment to the pelagic zone, suggested its importance as an indicator of progressive ecological and trophic deterioration of lakes. This indication should be very useful for establishment of main targets in water management.
Prorocentrum minimum (Pavillard) Schiller has occurred in the Gulf of Gdańsk in low abundance for several years. However, in summer 1997 a significant increase in the numbers of cells was noted. In the same year a P. minimum bloom was recorded for the first time in one of the harbour basins in Gdynia, giving rise to a brown-red coloration of the water.
The phenomenon of cyanobacteria (blue-green algae) blooms in the Baltic and the surrounding freshwater bodies has been known for several decades.The presence of cyanobacterial toxic metabolites in the Curonian Lagoon has been investigated and demonstrated for the first time in this work (2006–07). Microcystis aeruginosa was the most common and widely distributed species in the 2006 blooms. Nodularia spumigena was present in the northern part of the Curonian Lagoon, following the intrusion of brackish water from the Baltic Sea; this is the first time that this nodularin-(NOD)-producing cyanobacterium has been recorded in the lagoon.W ith the aid of high-performance liquid chromatography (HPLC), four microcystins (MC-LR, MC-RR, MC-LY, MC-YR) and nodularin were detected in 2006.T he presence of these cyanobacterial hepatotoxic cyclic peptides was additionally confirmed by enzyme-linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PP1).Micr ocystin-LR, the most frequent of them, was present in every sample at quite high concentrations (from <0.1 to 134.2 μg dm−3).I n 2007, no cyanobacterial bloom was recorded and cyanotoxins were detected in only 4% of the investigated samples.A comparably high concentration of nodularin was detected in the northern part of the Curonian Lagoon.I n one sample dimethylated MC-RR was also detected (concentration 7.5 μg dm−3).
Cyanobacterial blooms, often observed in eutrophic water reservoirs, produce toxic metabolites known as cyanotoxins that affect animal health. There are five groups of cyanotoxins classified on the basis of their toxic action: hepatotoxins, neurotoxins, cytotoxins, dermatotoxins and irritant toxins. Microcystin (MC) is a very common and well described hepatotoxin produced by various genera, such as Microcystis, Anabaena, Planktothrix, Anabenopsis, Hapalosiphon and Nostoc. It acts as an inhibitor of serine/threonine protein phosphatase 1 (PP1) and 2A (PP2A), inducing hyperphosphorylation of cell proteins and a variety of toxic changes in hepatocytes often leading to liver insufficiency and death caused by hypovolemic shock. Since the reports on MC toxicity are on the increase this cyanotoxin should be treated as an important environmental factor affecting human and animal health. A brief overview of existing literature on the intake, mechanism of action, and hepatotoxic effects on mammalian animals is presented in this paper
In temperate zones, algae biomass may be efficiently controlled by Daphnia sp., which is the most significant grazer among filter-feeding zooplankton. Daphnia population dynamics depends mostly on the trophic state of the ecosystem, which determines both fish community structure and food quality and availability. Relatively invariable water inflow to a reservoir with small amplitudes supports balanced biotic interactions. Here, we present simulations using the DALIS model that well characterised behaviour in a temperate ecosystem under stable abiotic conditions. The model results allowed us to predict the extent to which predation by fish would disturb the dynamics of Daphnia under different food conditions. Therefore, mathematical modelling may be an important tool for establishing appropriate recovery strategies in eutrophic water bodies. Although the model in this study characterised temperate zone conditions, its application to tropical lakes, where the dynamics of zooplankton and fish are substantially different, is discussed.
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