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Grazing of the copepod Cyclops vicinus on toxic Microcystis aeruginosa : potential for controlling cyanobacterial blooms and transfer of toxins

Mohamed Z. A., Bakr A. A., Ghramh H. A.

Oceanological and Hydrobiological Studies

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2018

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Vol. 47, No. 3

296--302

EN

Grazing of zooplankton on phytoplankton may contribute to a reduction of harmful cyanobacteria in eutrophic waters. However, the feeding capacity and interaction between zooplankton and toxic cyanobacteria vary among grazer species. In this study, laboratory feeding experiments were designed to measure the grazing rate of the copepod Cyclops vicinus on Microcystis aeruginosa and the potential microcystin (MC) accumulation in the grazer. Copepods were fed a mixed diet of the edible green alga Ankistrodesmus falcatus and toxic M. aeruginosa for 10 days. The results showed that C. vicinus efficiently ingested toxic Microcystis cells with high grazing rates, varying during the feeding period (68.9–606.3 Microcystis cells animal-1 d-1) along with Microcystis cell density. Microcystis cells exhibited a remarkable induction in MC production under grazing conditions with concentrations 1.67–12.5 times higher than those in control cultures. Furthermore, C. vicinus was found to accumulate MCs in its body with concentrations increasing during the experiment (0.05–3.21 μg MC animal-1). Further in situ studies are needed to investigate the ability of Cyclops and other copepods to assimilate and detoxify MCs at environmentally relevant concentrations before deciding on the biocontrol of Microcystis blooms by copepods.

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Blooms of toxin-producing Cyanobacteria - a real threat in small dam reservoirs at the beginning of their operation

Pawlik-Skowrońska B., Toporowska M.

Oceanological and Hydrobiological Studies

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2011

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Vol. 40, No.4

30-37

EN

Large and harmful cyanobacterial blooms appeared in two newly-built artificial reservoirs shortly after being filled with water. Taxonomic composition of cyanobacterial communities was highly variable in both water bodies and fast species replacement was observed. In the first year of the operation of the smaller Konstantynów Reservoir, the mass development of Anabaena flos-aquae and Planktolyngbya limnetica (48.7 and 53.6% of the cyanobacterial abundance) occurred in summer, while in autumn the dominance of Planktothrix agardhii (99.9%, 14.95 × 106 ind. dm-3 ) was noted. The surface scum developed in summer consisted of An. flos-aquae that contained high amounts of anatoxin-a (1412.4 μg AN-a dm-3 of scum) and smaller amounts of microcystins (10 μg eq. MC-LR dm-3 of scum). In the larger Kraśnik Reservoir, Aphanizomenon flos-aquae occurred in high abundance in spring and summer, however, it was replaced created thick surface scum. Simultaneously, a hazardous increase in the total concentration of microcystins (from 13.6 to 788.5 μg eq. MC-LR dm-3 of water with scum) and anatoxin-a (from 0.03 to 43.6 μg dm-3) was observed.

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Toxin-producing blooms of the cyanobacterium Microcystis aeruginosa in rainwater ponds in Saudi Arabia

Al-Shehri A.M.

Oceanological and Hydrobiological Studies

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2010

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Vol. 39, No.4

171-187

EN

The present study describes for the first time the toxin production by Microcystis aeruginosa blooms in three rainwater ponds in Saudi Arabia. The cell density of M. aeruginosa correlated with chlorophyll-a, temperature and nutrient concentrations. Microcystis blooms produced the hepatotoxin microcystin (MCYST) with concentrations of 0.988-3.04 mg g-1 dry weight, and a toxin profile consisting mainly of MCYST-RR, -YR and -LR. MCYSTs were also detected in pond waters at levels exceeding the WHO guideline value (11.2-34.6 μg l^-1). The study suggests the monitoring of toxic cyanobacteria in such potable water sources to protect the public from potent toxins.

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Relationship between Cyanobacterial bloom composition and anatoxin-a and microcystin occurrence in the eutrophic dam reservoir (SE Poland)

Pawlik-Skowrońska B., Skowroński T., Pirszel J., Adamczyk A.

Polish Journal of Ecology

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2004

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Vol. 52, nr 4

479-490

EN

Long-lasting cyanobacterial blooms were observed over summer periods 2001-2003 in the highly eutrophic dam reservoir (Zemborzycki Reservoir near Lublin, SE Poland) loaded with nitrogen and phosphorus by the river Bystrzyca. Chloriphyll a content and water transparence reached in summer periods 2002-2003 average values 115-129 [mi]g l^-1 and 0.5 m, respectively. The blooms consisted of eight taxa of Cyanobacteria occurring in different proportions: Aphanizomenon flos-aquae, Anabaena circinalis, Anabaena spiroides, Anabaena flos-aquae, Planktothrix agardhii, Microcystis aeruginosa, Microcystis viridis, Microcystis wesenbergii. At decreased average water temperature and increased concentration of dissolved ammonium-nitrogen in summer 2003, compared with two earlier years, a replacement of dominant Aph. flos-aquae to P. agardhii was observed. The total abundance of potential microcystin producers was positively correlated with the content of these hepatotoxins in the reservoir water. First time in Poland, mass occurrence of Anabaena strains producing anatoxin-a was observed. Anatoxin-a concentration in the reservoir water was positively correlated with total abundance of 3 taxa of Anabaena. It was no such correlation with Aph. flos-aquae.