Author
G. A. Walker‐Arnott
Bio: G. A. Walker‐Arnott is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 470 citations.
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508 citations
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TL;DR: A set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera are presented and designed to minimize the effort of microscopic measurement.
Abstract: Microalgal biovolume is commonly calculated to assess the relative abundance (as biomass or carbon) of co-occurring algae varying in shape and/or size. However, a standardized set of equations for biovolume calculations from microscopically measured linear dimensions that includes the entire range of microalgal shapes is not available yet. In comparison with automated methods, the use of microscopical measurements allows high taxonomic resolution, up to the species level, and has fewer sources of error. We present a set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera. The equations are designed to minimize the effort of microscopic measurement. The similarities and differences between our proposal for standardization and previously published proposals are discussed and recommendations for quality standards given.
3,179 citations
TL;DR: The Effects of Harmful Algal Blooms on Aquatic Organisms: Vol. 10, No. 2, pp. 113-390 as mentioned in this paper was the first publication of this article.
Abstract: (2002). The Effects of Harmful Algal Blooms on Aquatic Organisms. Reviews in Fisheries Science: Vol. 10, No. 2, pp. 113-390.
1,242 citations
TL;DR: These findings not only show that cryptic genetic variants abound in sympatry, but also that they are reproductively isolated and, therefore, biologically distinct units.
425 citations
TL;DR: A critical look at how best to use CPR data, including descriptions of each CPR taxonomic entity, the idiosyncrasies associated with counting many of the taxa, the logic behind taxonomic changes in the Survey, and recommendations on choosing the spatial and temporal scale of study are taken.
349 citations
TL;DR: Gaps in knowledge include further information about the whole genome of Pseudo-nitzschia, mechanisms of DA production and decline, presence or absence of a resting stage, heterotrophic ability, impact of viruses and fungi, and a more complete description of the ecological and physiological roles of DA.
Abstract: LELONG A., HEGARET H., SOUDANT P. AND BATES S.S. 2012. Pseudo-nitzschia (Bacillariophyceae) species, domoic acid and amnesic shellfish poisoning: revisiting previous paradigms. Phycologia 51: 168-216. DOI: 10.2216/11-37 Pseudo-nitzschia is a globally distributed diatom genus, some species of which produce domoic acid (DA), the neurotoxin that causes amnesic shellfish poisoning. This toxin killed at least three humans in 1987, launching numerous studies concerning the identification, distribution, ecology and physiology of Pseudo-nitzschia spp. Since previous reviews in 1998, knowledge has been gained about the fate of DA, including its accumulation by marine animals and its degradation by light and bacteria. Molecular techniques and more precise microscopy have enabled the description of new Pseudo-nitzschia species, 15 since 2002, including ones that are cryptic and pseudo-cryptic. An increasing number of the 37 identified species, including oceanic and coastal species, have been studied in laboratory culture. The sexual reproduction of 14 species has been documented. Fourteen species have now been shown to be toxigenic, although some strains are not always toxic under the testing conditions. The biotic and abiotic factors that modify DA production are reviewed, with a focus on how new discoveries have changed our original hypotheses about control mechanisms. Recent studies confirm that silicate and phosphate limitation trigger DA production. However, stress by low concentrations of iron or high concentrations of copper are newly discovered triggers, suggesting a trace-metal chelation role for DA. Organic sources of nitrogen (urea and glutamine), as well as changes in pH, CO2, salinity and bacterial concentration, also enhance DA production. Laboratory and field studies sometimes give divergent results for conditions that are conducive to toxin production. Gaps in knowledge include further information about the whole genome of Pseudo- nitzschia (including sexual stages), mechanisms of DA production and decline, presence or absence of a resting stage, heterotrophic ability, impact of viruses and fungi, and a more complete description of the ecological and physiological roles of DA.
330 citations