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Summary Biodiversity is declining world-wide with detrimental effects on ecosystems. However, we lack a quantitative understanding of the shape of the relationship between microbial biodiversity and ecosystem function (BEF). This limits our understanding of how microbial diversity depletion can impact key functions for human well-being, including pollutant detoxification. Three independent microcosm experiments were conducted to evaluate the direction (i.e. positive, negative or null) and the shape of the relationships between bacterial diversity and both broad (i.e. microbial respiration) and specialized (i.e. toxin degradation) functions in five Australian and two UK freshwater ecosystems using next-generation sequencing platforms. Reduced bacterial diversity, even after accounting for biomass, caused a decrease in broad (i.e. cumulative microbial respiration) and specialized (biodegradation of two important toxins) functions in all cases. Unlike the positive but decelerating BEF relationship observed most frequently in plants and animals, most evaluated functional measurements were related to bacterial diversity in a non-redundant fashion (e.g. exponentially and/or linearly). Synthesis. Our results suggest that there is a lack of functional redundancy in the relationship between bacterial diversity and ecosystem functioning; thus, the consequences of declining microbial diversity on ecosystem functioning and human welfare have likely been considerably underestimated.

The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world population of lesser flamingos Phoeniconaias minor. In this area, mysterious flamingo die-offs have occupied researchers for four decades. Recently, cyanobacterial toxins came into the fore as a possible explanation for mass mortalities because the main food source of lesser flamingos is the cyanobacterium Arthrospira fusiformis. We took weekly samples from July 2008 to November 2009 from Lakes Nakuru and Bogoria and analyzed them by high performance liquid chromatography for microcystins. Monthly, samples were cross-checked using protein phosphatase inhibition assays with lower detection limits and additionally screened for polar toxins. During our study period, three flamingo die-offs occurred at L. Bogoria and we were able to analyze tissues of 20 carcasses collected at the shoreline. No cyanotoxins were detected either in plankton samples or in flamingo tissues. Accordingly, other reasons such as food composit...

1. A sample of adult signal crayfish were taken from a pond with a hepatotoxic bloom of the benthic cyanobacterium Oscillatoria sancta. Cyanobacteria were found in the stomachs of thirty-one out of thirty-two crayfish examined. 2. To examine the effect of hepatotoxic cyanobacteria on crayfish a 14-day feeding trial was carried out with thirty-six animals. There were three treatments: (i) hepatotoxic and (ii) non-toxic Planktothrix agardhii; and (iii) crayfish pellets as a control. 3. High-performance liquid chromatography (HPLC) showed that microcystins (the toxins of P. agardhii) had accumulated in the hepatopancreas of 50% of the animals in the toxic treatment. 4. The cyanobacteria did not appear to have any negative impact on the crayfish. All crayfish survived, remained motile and ate throughout the experiment. 5. During the experiment blood samples were taken and the total number of haemocytes counted. At the end of the experiment glucose concentration and relative wet weight of the hepatopancreas were measured. No differences between crayfish fed on toxic and non-toxic P. agardhii and the controls were found. 6. The fact that microcystin accumulates in the crayfish hepatopancreas indicates that the toxin may be transferred further up the food chain.

Six microcystins were identified in a laboratory culture of the cyanobacterium (blue-green alga) Microcystis aeruginosa PCC 7813 using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) and mass spectrometry (LC-MS). The toxins were purified and further characterized by amino acid analysis and tandem mass spectrometry (MS-MS). The presence of the previously reported microcystin-LR and microcystin-LY was confirmed. Two further microcystins were characterized as microcystin-LW and microcystin-LF. Another two toxins were partially characterized and are believed to be an analog of microcystin-LR (molecular weight 1008) and microcystin-LM (molecular weight 969). Natural bloom material of M. aeruginosa collected from 2 reservoirs was found to have similar microcystin profiles using HPLC-DAD and LC-MS, indicating the widespread occurrence of these microcystin variants. In addition, the presence of 5 of the microcystins was confirmed in the rumen contents of a lamb by LC-MS and LC-MS-MS, providing the first report of microcystins identified in an animal suspected of being poisoned by cyanobacterial hepatotoxins.

Small (10 g) tilapia (Oreochromis niloticus) were exposed to pure and mixed populations of toxic and non-toxic strains of the cyanobacterium Microcystis aeruginosa (100% toxic, 50% toxic, 25% toxic, 0% toxic) at two particle concentrations (1 × 106 and 5 × 10sparticles ml−1). At both concentrations there was a progressive decrease in grazing rate as the percentage of toxic cells increased. Differences in opercular beat rates, and hence the volumes of water passed over the gills, were also recorded among treatments, opercular beat rates decreasing as the percentage of toxic cells increased. Although in all treatment groups with toxic cells present, the medium had detectable levels (>250 ng I−1) of extracellular microcystin-LR toxin present, grazing was correlated with particle-bound rather than extracellular levels.

Specific, straightforward, and rapid procedures are required for the detection, identification, and quantification of the potent low molecular weight toxins that are produced by blooms and scums of cyanobacteria (blue-green algae) in waterbodies. Use of the Microtox bioluminescence assay and the brine shrimp (Artemia salina) has been advocated for the initial screening of cyanobacterial blooms for microcystin hepatotoxins. Inhibition of bacterial luminescence in the Microtox assay and brine shrimp mortality were determined with microcystin-containing and nonmicrocystin-containing cyanobacteria. Extraction and fractionation of test samples was undertaken to select and isolate microcystincontaining fractions and reduce interference from other fractions. Maximal inhibition of bacterial luminescence in the Microtox assay occurred with fractions from Microcystis strains and an Anabaena bloom that did not contain microcystins. By contrast, the bioassay of fractions using brine shrimps correlated with the distribution of microcystin-LR in the fractionated Microcystis extracts. © 1994 by John Wiley & Sons, Inc..

The tilapia Oreochromis niloticus and the silver carp Hypophthalmichthys molitrix were exposed to toxic and non-toxic strains of the cyanobacterium Microcystis aeruginosa in order to determine if cells of the toxic strain were ingested and, if not, by what mechanism they were excluded. Enumeration of cyanobacterial particles before and after exposure to fish showed that there were no significant differences (P

A combined liquid chromatographic mass spectrometric method was developed for the analysis of microcystins (hepatotoxic cyclic heptapeptides) produced by cyanobacteria (blue-green algae). The method was used to confirm the identity of microcystins, tentatively identified by high-performance liquid chromatography using diode-array detection, in extracts from natural-bloom material and a sample of river water where hepatotoxic cyanobacteria were present. The potential of tandem mass spectrometry for obtaining structural information and providing a selective screen for these compounds was also investigated.

The incidence of cyanobacterial blooms in freshwaters, including drinking water reservoirs, has increased over the past few decades due to rising nutrient levels. Microcystins are hepatotoxins released from cyanobacteria and have been responsible for the death of humans as well as domestic and wild animals. Microcystins are chemically very stable and many processes have only limited efficacy in removing them. In this paper we review a range of water treatment methods which have been applied to removing microcystins from potable waters.

The cyanobacteria (blue-green algae) which commonly produce mass developments in fresh and saline waters are capable of producing toxins. These compounds have been responsible for the deaths of animals, birds and fish in many countries, and have been linked with several forms of human illness through skin contact and ingestion. Evidence has accumulated over the past decade that cyanobacterial toxins occur commonly in European waters which contain cyanobacterial mass growths. This paper summarizes the recent published occurrence and types of cyanobacterial toxins found in European waters with reference to poisoning incidents. Cyanobacterial blooms were particularly abundant in the warm dry summer of 1989 in the UK. The deaths of sheep and dogs and the cases of human illness that were ascribed to cyanobacterial toxins were followed by a more intensive and wider investigation into the extent of cyanobacterial toxicity in UK waters than had hitherto been undertaken. Of the cyanobacterial blooms sampled from over 90 freshwaters, approximately two-thirds were toxic (lethal) according to mouse bioassay. Short-term and long-term needs for the recognition, quantification and management of problems which can be caused by potentially toxigenic cyanobacteria in water-bodies used for recreation, aquaculture and potable supply are briefly discussed.