Variability of Pseudo-nitzschia and domoic acid in the Juan de Fuca eddy region and its adjacent shelves

Abstract

The Juan de Fuca eddy is a toxic ''hot spot.'' Domoic acid (DA) was detected in the eddy during each of six cruises over a 4-yr study, although Pseudo-nitzschia abundance and toxin concentrations were highly variable. During the September 2004 eddy bloom, Pseudo-nitzschia spp. exceeded 13 3 10 6 cells L 21 , and particulate DA reached 80 nmol L 21 . Of the .10 species of Pseudo-nitzschia identified in this region, those coincident with the most toxic blooms are P. cf. pseudodelicatissima, P. cuspidata, P. multiseries, and P. australis. However, the presence of any particular species could not be used as an indicator of toxicity because of the high level of variability in intracellular DA in field assemblages. Pseudo-nitzschia cells were typically associated with blooms of other diatom taxa but also were coincident with blooms of euglenoids and dinoflagellates in the eddy region. Pseudo-nitzschia always comprised ,17% of the total carbon biomass, thereby rendering remote sensing an unsuitable means for predicting toxigenic Pseudo-nitzschia blooms in this region. Our results support the hypothesis that the Juan de Fuca eddy region and not the nearshore zone is the primary initiation site for toxic blooms of Pseudo-nitzschia affecting the Washington coast. Although particulate DA was observed near the edges of the Columbia River plume, whether toxin can be produced in situ in plume water is not resolved. No first-order predictive relationships were found for either Pseudo-nitzschia abundance or DA concentration and environmental data from all six cruises. Domoic acid (DA), produced by species of the diatom genus Pseudo-nitzschia, was first recognized as a biotoxin to humans when over 100 people became severely ill after consuming mussels harvested near Prince Edward Island, Canada, in 1987(Wright et al. 1989. Most of the known toxic events in North America since that time have occurred on the U.S. West Coast, where DA was first implicated in the illness and death of brown pelicans and Brandt's cormorants in Monterey Bay, California, in 1991(Work et al. 1993. In October 1991, about 1 month following the toxic bloom of Pseudo-nitzschia in California, DA concentrations above the regulatory limit were found in the edible parts of Pacific razor clams (Siliqua patula) and Dungeness crabs (Cancer magister) on the Washington coast (Wekell et al. 1994). In 1998, the deleterious effect of DA on the health of marine mammals, in particular, California sea lions (Zalophus californianus), was confirmed for the first time along the West Coast (Scholin et al. 2000), 1 Corresponding author (Vera.L.Trainer@noaa.gov). AcknowledgmentsWe thank the officers and crew of the R/V Wecoma, R/V Atlantis, R/V Thompson, and R/V Melville for their assistance. We thank J. Herndon for nutrient analysis; N. Tsui, B. Bill, and A. Odell for the Pseudo-nitzschia cell enumeration; K. Baugh and S. Nance for DA analyses; M. Bernhardt and M. Foy for plankton analyses; M. Auro, R. Radan, and N. Ladizinsky for pigment analyses; N. Kachel for condu...

Induction of domoic acid production in the toxic diatom Pseudo-nitzschia seriata by calanoid copepods

“…This was emphasized by Marchetti et al (2004), who in their field study concluded that environmental factors other than those studied so far (mainly related to nutrient stress) need to be examined to understand DA production in Pseudo-nitzschia species. Trainer et al (2009) supported this view by stating that, under natural conditions, macronutrients cannot be used as reliable predictors of toxicity of a Pseudo-nitzschia bloom. Our study shows that zooplankton grazing could be one of the factors controlling the toxicity of a Pseudo-nitzschia bloom in the field.…”

Climatic regulation of the neurotoxin domoic acid

“…The linkages between DA production and environmental factors such as macronutrients, trace metals, temperature, and salinity are also complex and variable (16). It is likely the case that no one single environmental variable is a strong predictor of DA (27); hence a mechanistic explanation behind cellular-level DA production and elevated DA in shellfish during warm ocean regimes is outside the scope of this study given the data we have. Even so, our findings frame future work investigating DA production by Pseudo-nitzschia in the context of conditions associated with warm regimes, for example, monitoring changes in species composition over time to investigate whether distinctive "warm" Pseudo-nitzschia assemblages indeed cooccur with copepod community shifts.…”

“…These events support the hypothesis that up-regulation of DA, and/or enhanced growth of toxigenic Pseudo-nitzschia is favored during the transition from warm to cool regimes. Warm ocean regimes potentially affect Pseudonitzschia species abundance and toxicity in an array of ways, from cellular and metabolic processes that are sensitive to elevated temperatures to larger-scale changes in phenology, water column structure, and circulation patterns (27,34). The linkages between DA production and environmental factors such as macronutrients, trace metals, temperature, and salinity are also complex and variable (16).…”

“…The closure threshold for shellfish harvesting is DA in shellfish tissue of ≥20 parts per million (ppm). Depuration of DA by razor clams can take months to a year (27)(28)(29), complicating efforts to define discrete "DA events." To aid in deconvolving events, two metrics were defined: (i) "DA event onset," or the beginning of an event, conservatively defined as the first date that DA values surpassed 20 ppm with no prior incidences of DA above 20 ppm in the previous 12 mo; and (ii) "annual DA maxima," or the maximum DA value above 20 ppm reached each year; this captures DA events that can occur during prolonged depuration and also describes when the most toxic values occur each year.…”

Effects of changing pCO2 and phosphate availability on domoic acid production and physiology of the marine harmful bloom diatom Pseudo‐nitzschia multiseries

“…DA is transferred through food-web interactions, and can affect the ecosystem over large spatial and temporal scales. DA has been detected in marine consumers ranging from copepods to mollusks, fish, and mammals (Doucette et al 2006;Caron et al 2010), and ASP toxicity events have greatly increased in both frequency and intensity over the last decade along the U.S. West Coast (Scholin et al 2000;Trainer et al 2000). In California waters, outbreaks of DA poisoning from toxic Pseudo-nitzschia spp.…”