Toxic Cyanobacteria in Greek Freshwaters, 1987—2000: Occurrence, Toxicity, and Impacts in the Mediterranean Region

Abstract

In a survey in Greece from 1987 to 2000 hepatotoxic cyanobacterial blooms were observed in 9 out of 33 freshwaters. Microcystins (MCYSTs) were detected by HPLC in 7 of these lakes, and the total MCYST concentration per scum dry weight ranged from 50.3 to 1638 ± 464 μg g—1. Cyanobacterial genera (Microcystis, Anabaena, Anabaenopsis, Aphanizomenon, Cylindrospermopsis) with known toxin producing taxa were present in 31 freshwaters. From our data and a review of the literature, it would appear that Mediterranean countries are more likely 1) to have toxic cyanobacterial blooms consisting of Microcystis spp. and 2) to have higher intracellular MCYST concentrations. A case study in Lake Kastoria is used to highlight seasonal patterns of cyanobacterial and MCYST‐LR occurrence and to assess cyanotoxin risk. Cyanobacterial biovolume was high (> 11 μL L—1) throughout the year and was in excess of Guidance Level 2 (10 μL L—1) proposed by WHO for recreational waters and Alert Level 2 for drinking water. Further, surface water samples from April to November exceeded Guidance Level 3, with the potential for acute cyanobacterial poisoning. Intracellular MCYST‐LR concentrations (max 3186 μg L—1) exceeded the WHO guideline for drinking water (1 μg L—1) from September to November with a high risk of adverse health effects. Preliminary evidence indicates that in 3 lakes microcystins are accumulated in some aquatic organisms. Generally, a high risk level can be deduced from the data for the Mediterranean region.

Cyanobacterial abundance and microcystin occurrence in Mediterranean water reservoirs in Central Spain: microcystins in the Madrid area

“…The data presented in this paper demonstrate that potentially toxic cyanobacteria were present in all the reservoirs studied throughout the entire sampling period, and that they became dominant at least once a year, especially from September to November. This period in which potentially toxic cyanobacteria were abundant in the phytoplankton community is similar to those in other Mediterranean countries, such as Greece, where potentially toxic cyanobacteria usually dominate from May to December (Cook et al, 2004;and references therein), and Israel, where potentially toxic cyanobacteria appear in Kinneret Lake in summer-autumn (Zohary, 2004).…”

“…At this threshold value, five of the eight reservoirs analysed (62%) commonly showed blooms (those in this study and the Atazar reservoir; Almodovar et al, 2004;Barco et al, 2004). The prevalence of potentially toxic cyanobacterial blooms observed in this study is higher than the value found in other Mediterranean countries, such as Greece, where 27% of the waterbodies had blooms, of which 77.8% were toxic (Cook et al, 2004). This divergence could be partly explained by the fact that our study was based on high-frequency (weekly) sampling during the typical blooming period.…”

“…There have been few reports of microcystins in the Mediterranean region (Cook et al, 2004) and information about the prevalence of microcystin in Spanish reservoirs is particularly scarce (Barco et al, 2004;Quesada et al, 2004;Aboal & Puig, 2005). Our data, together with previously published data (Barco et al, 2004) obtained from another reservoir of the region, and from the Santillana reservoir (Gordo et al, 1999;Sanchis et al, 2002) indicate that potentially toxic cyanobacteria, cyanobacterial blooms and microcystins are common in the Madrid region.…”

“…The most common buoyant and potentially toxic cyanobacteria in the Madrid region were of the genera Microcystis, Aphanizomenon and Anabaena, which, together with Planktothrix, are also the dominant potentially toxic genera throughout Europe (Sivonen et al, 1990;Willen & Mattsson, 1997;Fastner et al, 1999;Cook et al, 2004). Species of these genera are known to be dominant in monomictic waterbodies with a stable water column, although Microcystis can adapt to diel fluctuations in stratification and mixing in lowlatitude lakes (Reynolds et al, 2002).…”

“…The distribution of microcystins in freshwater ecosystems at the national or regional level has been investigated in some countries, such as Germany, Portugal and Greece (Vasconcelos, 1994;Fastner et al, 1999;Cook et al, 2004). These studies yielded largely similar results indicating that typically 70% of the potentially toxic cyanobacterial blooms are microcystin producers.…”