Production of microcystins in calcareous Mediterranean streams: The Alharabe River, Segura River basin in south-east Spain

Abstract

The development of epilithic cyanobacteria communities in a Mediterranean calcareous stream in the province of Murcia (SE Spain) was studied during the course of one year in an attempt to clarify the environmental variables that influence the production of microcystins. The predominant cyanobacteria were species of Rivularia, which formed conspicuous colonies throughout the year. Seasonally, other species were abundant: Schizothrix fasciculata, Tolypothrix distorta and Phormidium splendidum. All the species collected produced microcystins to a varying degree (up to five varieties), while the benthic community as a whole produced concentrations as high as 20.45 mg m −2 . At the same time, the presence of microcystins dissolved in water was confirmed. Among environmental variables, air temperature and silicate content were positively and strongly correlated with total microcystins, while nitrite, nitrate, orthophosphate, calcium and flow were negatively correlated with them. Dissolved microcystins were negatively correlated with microcystin LR, P.A.R. and total phosphorus and positively with rainfall. The production of microcystin YR seems to be regulated by different factors from those regulating the other main varieties (microcystin LR and microcystin RR). The data obtained indicate that all the tested benthic cyanobacteria produced microcystins in this shallow calcareous stream, which may contribute to their predominance in the prevailing conditions. The accumulation of microcystins in mucilaginous colonies of other groups of algae poses new questions concerning the possible ecological function of these compounds and needs further study.

Genetic and morphological characterization of Rivularia and Calothrix (Nostocales, Cyanobacteria) from running water

“…1d-f). Similar occurrence of both types of Rivularia on rocks in calcareous springs and streams has been described previously (Whitton, 2002), and are dominant in the majority of the Spanish rivers studied (Aboal et al, 2002(Aboal et al, , 2005. However, when the rivulariacean-type strains isolated from these calcareous rivers (Table 1), where Rivularia was dominant, were cultured under laboratory conditions and examined morphologically, all of them were very similar phenotypically (Fig.…”

Morphological and molecular characterization of cyanobacteria from a Brazilian facultative wastewater stabilization pond and evaluation of microcystin production

“…Most cyanotoxin research has been conducted on planktonic cyanobacteria because of the potential for bloom forming; however, recent studies show that benthic cyanobacteria can also produce toxins (Aboal et al, 2005;Mohamed et al, 2006;Izaguirre et al, 2007;Richardson et al, 2007). Of the five cyanobacterial genera isolated from the Cajati WSP, certain strains of Nostoc (Sivonen et al, 1990), Leptolyngbya (Richardson et al, 2007), and Phormidium (Aboal et al, 2005) have been reported as microcystin producers.…”

“…Of the five cyanobacterial genera isolated from the Cajati WSP, certain strains of Nostoc (Sivonen et al, 1990), Leptolyngbya (Richardson et al, 2007), and Phormidium (Aboal et al, 2005) have been reported as microcystin producers. Furthermore, two Leptolyngbya strains (NPLJ-34 and NPLJ-35), a Synechococcus elongatus strain (NPLB-1) and a Nostoc muscorum strain (NPBR-3) isolated from Brazilian water bodies, have been reported as hepatotoxic, although the specific toxin was not identified (Azevedo & Magalhães, 2002).…”

Biology of the freshwater diatom Didymosphenia: a review

“…The lower parts of stalks sometimes have frequent epiphytic cyanobacteria, a taxonomic group which are well known to form microcystins (Codd et al, 2005). However, Aboal et al (2005) reported the presence of microcystins, especially microcystin LR, in the mucilaginous colonies of Cymbella affinis from the Alharabe R. in N-E Spain; the test samples did not include cyanobacteria, though cyanobacteria were frequent in the river and so the possibility of their microcystins being trapped in the Cymbella colonies could not be ruled out. Further studies (based on HPLC-mass spectrometry) have now indicated the presence of microcystins in two populations of D. geminata collected quite late in the growth season: Stony Gill (UK) in July 2000 and R. Puntledge (Vancouver Is) in September 2007 (M. Aboal, pers.…”