Evolution of Protein Molecules

The rise of harmful cyanobacteria blooms: The potential roles of eutrophication and climate change

In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with a peak intensity over three times greater than any previously observed bloom. Here we show that long-term trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with meteorological conditions in spring 2011, produced record-breaking nutrient loads. An extended period of weak lake circulation then led to abnormally long residence times that incubated the bloom, and warm and quiescent conditions after bloom onset allowed algae to remain near the top of the water column and prevented flushing of nutrients from the system. We further find that all of these factors are consistent with expected future conditions. If a scientifically guided management plan to mitigate these impacts is not implemented, we can therefore expect this bloom to be a harbinger of future blooms in Lake Erie.

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Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions

Biological nitrogen fixation is an important source of fixed nitrogen for the biosphere. Microorganisms catalyse biological nitrogen fixation with the enzyme nitrogenase, which has been highly conserved through evolution. Cloning and sequencing of one of the nitrogenase structural genes, nifH, has provided a large, rapidly expanding database of sequences from diverse terrestrial and aquatic environments. Comparison of nifH phylogenies to ribosomal RNA phylogenies from cultivated microorganisms shows little conclusive evidence of lateral gene transfer. Sequence diversity far outstrips representation by cultivated representatives. The phylogeny of nitrogenase includes branches that represent phylotypic groupings based on ribosomal RNA phylogeny, but also includes paralogous clades including the alternative, non-molybdenum, non-vanadium containing nitrogenases. Only a few alternative or archaeal nitrogenase sequences have as yet been obtained from the environment. Extensive analysis of the distribution of nifH phylotypes among habitats indicates that there are characteristic patterns of nitrogen fixing microorganisms in termite guts, sediment and soil environments, estuaries and salt marshes, and oligotrophic oceans. The distribution of nitrogen-fixing microorganisms, although not entirely dictated by the nitrogen availability in the environment, is non-random and can be predicted on the basis of habitat characteristics. The ability to assay for gene expression and investigate genome arrangements provides the promise of new tools for interrogating natural populations of diazotrophs. The broad analysis of nitrogenase genes provides a basis for developing molecular assays and bioinformatics approaches for the study of nitrogen fixation in the environment.

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Nitrogenase gene diversity and microbial community structure: a cross-system comparison.

The public health, tourism, fisheries, and ecosystem impacts from harmful algal blooms (HABs) have all increased over the past few decades. This has led to heightened scientific and regulatory attention, and the development of many new technologies and approaches for research and management. This, in turn, is leading to significant paradigm shifts with regard to, e.g., our interpretation of the phytoplankton species concept (strain variation), the dogma of their apparent cosmopolitanism, the role of bacteria and zooplankton grazing in HABs, and our approaches to investigating the ecological and genetic basis for the production of toxins and allelochemicals. Increasingly, eutrophication and climate change are viewed and managed as multifactorial environmental stressors that will further challenge managers of coastal resources and those responsible for protecting human health. Here we review HAB science with an eye toward new concepts and approaches, emphasizing, where possible, the unexpected yet promising new directions that research has taken in this diverse field.

https://www.whoi.edu/fileserver.do?id=201484&pt=2&p=28251

Progress in understanding harmful algal blooms: paradigm shifts and new technologies for research, monitoring, and management.

Free-living, marine dinoflagellates are typified by a well-defined, haplontic life cycle with relatively few stages. The most unusual departure from this life cycle is one reported for the heterotrophic dinoflagellate Pfiesteria piscicida Steidinger et Burkholder. This species is alleged to have at least 24 life cycle stages including amoebae and a chrysophyte-like cyst form (Burkholder et al. 1992, Burkholder and Glasgow 1997a) not previously known in free-living marine dinoflagellates. Litaker et al. (2002) redescribed the life cycle of P. piscicida from single-cell isolates and found only life cycle stages typical of free-living marine dinoflagellates. The discrepancy between these observations and the life cycle reported in the literature prompted a rigorous study to resolve the life cycle of P. piscicida.Burkholder and Glasgow (2002) took exception to this study, arguing that Litaker et al. (2002) misunderstood the life cycle of P. piscicida and ignored recent publications. We present a rebuttal of their criticisms and suggest a simple way to resolve the discrepancies in the P. piscicida life cycle.

Reply to comment on the life cycle and toxicity of pfiesteria piscicida revisited1

Gambierdiscus and Fukuyoa dinoflagellates produce a suite of secondary metabolites, including ciguatoxins (CTXs), which bioaccumulate and are further biotransformed in fish and marine invertebrates, causing ciguatera poisoning when consumed by humans. This study is the first to compare the performance of the fluorescent receptor binding assay (fRBA), neuroblastoma cell-based assay (CBA-N2a), and liquid chromatography tandem mass spectrometry (LC-MS/MS) for the quantitative estimation of CTX contents in 30 samples, obtained from four French Polynesian strains of Gambierdiscus polynesiensis. fRBA was applied to Gambierdiscus matrix for the first time, and several parameters of the fRBA protocol were refined. Following liquid/liquid partitioning to separate CTXs from other algal compounds, the variability of CTX contents was estimated using these three methods in three independent experiments. All three assays were significantly correlated with each other, with the highest correlation coefficient (r2 = 0.841) found between fRBA and LC-MS/MS. The CBA-N2a was more sensitive than LC-MS/MS and fRBA, with all assays showing good repeatability. The combined use of fRBA and/or CBA-N2a for screening purposes and LC-MS/MS for confirmation purposes allows for efficient CTX evaluation in Gambierdiscus. These findings, which support future collaborative studies for the inter-laboratory validation of CTX detection methods, will help improve ciguatera risk assessment and management.

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Comparative Study on the Performance of Three Detection Methods for the Quantification of Pacific Ciguatoxins in French Polynesian Strains of Gambierdiscus polynesiensis

Recently, we (1) reported that, since 1982, several regions across the North Atlantic and North Pacific Oceans have experienced warming in specific seasons and locations that have significantly increased the potential cellular growth rates and bloom seasons of two harmful algae, Alexandrium fundyense and Dinophysis acuminata , and that new blooms caused by these species have emerged in these same regions. In their comment “Harmful algal blooms in the Eastern North Atlantic Ocean,” Dees et al. (2) examine the Continuous Plankton Recorder data from the North Eastern Atlantic and North Sea from 1982 to 2015 and find no relationship between Dinophysis spp. abundance and sea-surface temperature. This observation is consistent … 

[↵][1]1To whom correspondence should be addressed. Email: christopher.gobler{at}stonybrook.edu.

 [1]: #xref-corresp-1-1

R. Wayne Litaker

Papers

Reply to comment on the life cycle and toxicity of pfiesteria piscicida revisited1

Comparative Study on the Performance of Three Detection Methods for the Quantification of Pacific Ciguatoxins in French Polynesian Strains of Gambierdiscus polynesiensis

Reply to Dees et al.: Ocean warming promotes species-specific increases in the cellular growth rates of harmful algal blooms.

Water Column Structure and Circulation In The Main channel, Twin Cays, Belize

Paralytic shellfish poisoning toxins in butter clams (Saxidomus gigantea) from the Kodiak Archipelago, Alaska.