Article

Blooms Like It Hot.

Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC 28557, USA.
Science (Impact Factor: 31.48). 05/2008; 320(5872):57-8. DOI: 10.1126/science.1155398
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Available from: Jef Huisman, Jun 18, 2015
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    • "Among them, temperature is one of the most important factors. Cyanobacteria usually grow better at relatively high temperature compared to other phyla of phytoplankton (Paerl & Huisman 2008). This may explain why the proportion of Cyanophyta was higher in July. "
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    ABSTRACT: Lake Taihu has attracted attention worldwide because of its extensive cyanobacterial blooms in the warm season. A better understanding of nutrient controls over phytoplankton is critical if the blooms are to be controlled. In the present study, we investigated the effects of nutrient addition on the growth of phytoplankton collected from Meiliang Bay (Station 1), Lake Center (Station 2), and Xukou Bay (Station 3) in July and September 2011. Cyanophyta was dominant in all water samples. Nevertheless, we observed higher proportions of other phyla and lower concentrations of microcystin-LR in September than in July. Further, Station 3 possessed many fewer Cyanophyta, but disproportionately higher concentrations of microcystin-LR than the other two stations. The overall phytoplankton biomass decreased in the order Station 1 > Station 2 > Station 3 and July > September. More interestingly, phosphorus-induced phytoplankton growth coincided with a distinct drop in particulate organic carbon (or nitrogen) to phosphorus ratio at Stations 2 and 3. By contrast, nitrogen, applied either alone or together with phosphorus, had negligible effect on phytoplankton growth. These results suggest that phytoplankton at Stations 2 and 3 were limited by phosphorus and no nutrient limitation occurred at Station 1. Therefore, nutrient limitation in Lake Taihu may be more dynamic and sporadic than previously thought and has implications for management of phytoplankton blooms.
    Journal of Freshwater Ecology 01/2015; 30(1). DOI:10.1080/02705060.2014.960901 · 0.59 Impact Factor
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    • "In nature, positive associations are the rule and negative associations are uncommon (Schluter 1984, Bertness and Callaway 1994, Li et al. 2008). The loss of connections may cause an algal bloom, particularly if the algae are favored by some positive feedback, such as allelopathy and favorable environmental conditions (Paerl and Huisman 2008). In fact, allelopathy is a strategy TABLE 2. Putative identification of key and dominant bacterioplankton T-RFs by in silico restriction digestions of 16S rRNA sequences. "
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    ABSTRACT: Algal blooms are a worldwide phenomenon and the biological interactions that underlie their regulation are only just beginning to be understood. It is established that algal microorganisms associate with many other ubiquitous, oceanic organisms, but the interactions that lead to the dynamics of bloom formation are currently unknown. To address this gap, we used network approaches to investigate the association patterns among microeukaryotes and bacterioplankton in response to a natural Scrippsiella trochoidea bloom. This is the first study to apply network approaches to bloom dynamics. To this end, terminal restriction fragment length polymorphism analysis showed dramatic changes in community compositions of microeukaryotes and bacterioplankton over the blooming period. A variance ratio test revealed significant positive overall associations both within and between microeukaryotic and bacterioplankton communities. An association network generated from significant correlations between terminal restriction fragments (T-RFs) revealed that S. trochoidea had few connections to other microeukaryotes and bacterioplankton and was placed on the edge. This lack of connectivity allowed for the S. trochoidea sub-network to break off from the overall network. These results allowed us to propose a conceptual model for explaining how changes in microbial associations regulate the dynamics of an algal bloom. In addition, key T-RFs were screened by principle component analysis, correlation coefficients and network analysis. Dominant T-RFs were then identified through 18S and 16S rRNA gene clone libraries. Results showed that microeukaryotes clustered predominantly with Dinophyceae and Perkinsea while the majority of bacterioplankton identified were Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. The ecological roles of both were discussed in the context of these findings.This article is protected by copyright. All rights reserved.
    Journal of Phycology 11/2014; 51(1). DOI:10.1111/jpy.12259 · 2.53 Impact Factor
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    • "Anthropogenic influence on freshwater ecosystems, especially increased nutrient loading and global warming, has led to more frequently occurring cyanobacterial blooms (Dokulil and Teubner, 2000; Paerl and Huisman, 2008; O'Neil et al., 2012). Cyanobacteria in high abundances are known to have a strong impact on freshwater ecosystems; for instance by negatively affecting herbivorous zooplankton (Ghadouani et al., 2003; Wilson et al., 2006). "
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    ABSTRACT: Cyanobacterial blooms in freshwater ecosystems are a matter of high concern with respect to human health and ecosystem services. Investigations on the role of cyanobacterial secondary metabolites have largely been confined to microcystins, although cyanobacteria produce a huge variety of toxic or inhibitory secondary metabolites. Mass occurrences of toxic cyanobacteria strongly impact freshwater zooplankton communities; especially the unselective filter feeder Daphnia. Daphnids have been shown to successfully suppress bloom formation. However, the opposite situation, i.e. the suppression of Daphnia populations by cyanobacteria can be observed as well. To understand these contradictory findings the elucidation of the underlying physiological mechanisms that help daphnids to cope with cyanotoxins is crucial. We fed Daphnia magna with the cyanobacterium Microcystis aeruginosa PCC7806 for 24h and used high-resolution LCMS analytics to analyze the Microcystis cells, the Daphnia tissue and the surrounding medium in order to investigate the fate of seven investigated cyanobacterial compounds (cyanopeptolins A-C, microcyclamide 7806A and aerucyclamides B-D). For none of these bioactive compounds evidence for biotransformation or biodegradation by Daphnia were found. Instead feeding and subsequent release experiments point at the importance of transport mechanisms in Daphnia with regard to the cyanopeptolins A and C and microcyclamide 7806A. In addition we found hints for new inducible defense mechanism in Microcystis against predation by Daphnia. These putative defense mechanisms include the elevated production of toxic compounds other than microcystins, as could be demonstrated here for aerucyclamide B and D, cyanopoeptolin B and microcyclamide 7806A. Moreover, our data demonstrate the elevated active export of at least one cyanobacterial compound (microcyclamide 7806A) into the surrounding medium as a response to grazer presence, which might constitute an entirely new not yet described cyanobacterial defense mechanism.
    Aquatic toxicology (Amsterdam, Netherlands) 08/2014; 156C:96-105. DOI:10.1016/j.aquatox.2014.08.003 · 3.51 Impact Factor
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