Zooplankton fecal pellets, marine snow, phytodetritus and the ocean’s biological pump

https://darchive.mblwhoilibrary.org/bitstream/handle/1912/5118/1-s2.0-S1568988311001533-main.pdf

Pseudo-nitzschia physiological ecology, phylogeny, toxicity, monitoring and impacts on ecosystem health

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.

Pseudo-nitzschia (Bacillariophyceae) species, domoic acid and amnesic shellfish poisoning: revisiting previous paradigms

Coastal eutrophication caused by anthropogenic nutrient inputs is one of the greatest threats to the health of coastal estuarine and marine ecosystems worldwide. To better understand and manage this threat, we compared six contrasting coastal ecosystems that are subjected to a range of riverine inputs of freshwater (buoyancy) and nutrients to address (i) impacts of anthropogenic nutrient inputs on ecosystem services; (ii) how ecosystem traits minimize or amplify these impacts; (iii) synergies among pressures (nutrient enrichment, over fishing, coastal development, and climate-driven pressures in particular); and (iv) management of nutrient inputs to coastal ecosystems. Globally, ~ 24% of the anthropogenic N released in coastal watersheds is estimated to reach coastal ecosystems. Our comparative assessment revealed that (i) in terms of the spatial extent of habitat degradation, Chesapeake Bay ranks number one followed in rank order by the northern Gulf of Mexico, the Baltic Sea, Great Barrier Reef, East China Sea and the northern Adriatic Sea; (ii) impacts of increases in anthropogenic nutrient loading are, and will continue to be, exacerbated by synergies with other pressures including over fishing, coastal development and climate-driven increases in sea surface temperature, acidification and rainfall; and (iii) when defined in terms of quantitative ranges of primary production, trophic status is not useful for relating anthropogenic nutrient loading to impacts. While managed reductions in point source inputs from sewage treatment plants are increasingly successful, controlling inputs from diffuse sources remains a challenging problem. Thus, it is likely that the severity of coastal eutrophication will continue to increase in the absence of effectively enforced, ecosystem-based management of both point and diffuse sources of nitrogen and phosphorus. This requires sustained, integrated research and monitoring, as well as repeated assessments of nutrient loading and impacts. These must be informed and guided by ongoing collaborations among scientists, politicians, managers and the public.

/pdf/the-globalization-of-cultural-eutrophication-in-the-coastal-ecvr2wn3li.pdf

The Globalization of Cultural Eutrophication in the Coastal Ocean: Causes and Consequences

Protists have fascinated microbiologists since their discovery nearly 350 years ago. These single-celled, eukaryotic species span an incredible range of sizes, forms, and functions and, despite their generally diminutive size, constitute much of the genetic diversity within the domain Eukarya. Protists in marine ecosystems play fundamental ecological roles as primary producers, consumers, decomposers, and trophic links in aquatic food webs. Much of our knowledge regarding the diversity and ecological activities of these species has been obtained during the past half century, and only within the past few decades have hypotheses depicting the evolutionary relationships among the major clades of protists attained some degree of consensus. This recent progress is attributable to the development of genetic approaches, which have revealed an unexpectedly large diversity of protists, including cryptic species and previously undescribed clades of protists. New genetic tools now exist for identifying protistan species of interest and for reexamining long-standing debates regarding the biogeography of protists. Studies of protistan diversity provide insight regarding how species richness and community composition contribute to ecosystem function. These activities support the development of predictive models that describe how microbial communities will respond to natural or anthropogenically mediated changes in environmental conditions.

/pdf/marine-protistan-diversity-1zglt410v9.pdf

Marine protistan diversity.

The diatom Pseudo-nitzschia produces the neurotoxin domoic acid, known to cause illness and death in marine mammals and humans. Measurements of surface- and deep-water domoic acid concentrations off the coast of California suggest that this toxin is rapidly transported to depth following diatom blooms.

/pdf/rapid-downward-transport-of-the-neurotoxin-domoic-acid-in-1yx8toid81.pdf

Rapid downward transport of the neurotoxin domoic acid in coastal waters.

Harmful algal blooms dominated by the diatom Pseudo-nitzschia spp. have become a perennial but variable event within surface waters near the greater Los Angeles area. Toxic blooms during spring seasons from 2005 to 2007 varied strongly in their overall toxicity and duration. Differences in bloom dynamics were linked to differences in storm-induced river discharge following episodic rain events and coastal upwelling, both major coastal processes that led to the injection of nutrients into coastal surface waters. Heavy river runoff during early 2005, a record-rainfall year, favored a phytoplankton community mainly comprised of algal taxa other than Pseudo-nitzschia. The spring bloom during 2005 was associated with low domoic acid surface concentrations and minor contributions of (mainly) P. delicatissima to the diatom assemblage. In contrast, highly toxic P. australis-dominated blooms during spring seasons of 2006 and 2007 were linked to strong upwelling events. River discharge quotas in 2006 and 2007, in contrast to 2005, fell well below annual averages for the region. Surface toxin levels were linked to colder, more saline (i.e. upwelled) water over the 3-year study, but no such consistent relationship between domoic acid levels and other physiochemical parameters, such as macronutrient concentrations or nutrient ratios, was observed.

Coastal upwelling linked to toxic Pseudo-nitzschia australis blooms in Los Angeles coastal waters, 2005–2007

Quantitative polymerase chain reaction (qPCR) for the identification and quantification of microbes has become a common tool for the study of harmful algal blooms (HABs). We developed a qPCR method for the diatom genus Pseudo-nitzschia. Several species of this genus form toxic blooms through the production of the neurotoxin domoic acid (DA). Outbreaks of toxicity attributed to DA along the US west coast have caused sickness and death of marine mammals and seabirds through food web contamination. The method developed here quantifies Pseudo-nitzschia spp. at low abundances in natural samples, thereby, providing a method to improve our understanding of the environmental conditions leading to blooms of these species. This has been accomplished previously by techniques for identification and quantification that are slow and laborious compared to qPCR. The approach was successfully tested and validated using eight species of Pseudo-nitzschia and 33 non-target organisms and employed to follow local bloom dynamics.

/pdf/development-and-environmental-application-of-a-genus-26xwmrb3wv.pdf

Development and environmental application of a genus-specific quantitative PCR approach for Pseudo-nitzschia species

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Rapid downward transport of the neurotoxin domoic acid in coastal waters.

Coastal upwelling linked to toxic Pseudo-nitzschia australis blooms in Los Angeles coastal waters, 2005–2007

Development and environmental application of a genus-specific quantitative PCR approach for Pseudo-nitzschia species