Nitrogenous nutrients promote the growth and toxicity of Dinophysis acuminata during estuarine bloom events.

Diarrhetic Shellfish Poisoning (DSP) is a globally significant human health syndrome most commonly caused by dinoflagellates within the genus Dinophysis. While blooms of harmful algae have frequently been linked to excessive nutrient loading, Dinophysis is a mixotrophic alga whose growth is typically associated with prey availability. Consequently, field studies of Dinophysis and nutrients have been rare. Here, the temporal dynamics of Dinophysis acuminata blooms, DSP toxins, and nutrients (nitrate, ammonium, phosphate, silicate, organic compounds) were examined over four years within two New York estuaries (Meetinghouse Creek and Northport Bay). Further, changes in the abundance and toxicity of D. acuminata were assessed during a series of nutrient amendment experiments performed over a three year period. During the study, Dinophysis acuminata blooms exceeding one million cells L-1 were observed in both estuaries. Highly significant (p<0.001) forward stepwise multivariate regression models of ecosystem observations demonstrated that D. acuminata abundances were positively dependent on multiple environmental parameters including ammonium (p = 0.007) while cellular toxin content was positively dependent on ammonium (p = 0.002) but negatively dependent on nitrate (p<0.001). Nitrogen- (N) and phosphorus- (P) containing inorganic and organic nutrients significantly enhanced D. acuminata densities in nearly all (13 of 14) experiments performed. Ammonium significantly increased cell densities in 10 of 11 experiments, while glutamine significantly enhanced cellular DSP content in 4 of 5 experiments examining this compound. Nutrients may have directly or indirectly enhanced D. acuminata abundances as densities of this mixotroph during experiments were significantly correlated with multiple members of the planktonic community (phytoflagellates and Mesodinium). Collectively, this study demonstrates that nutrient loading and more specifically N-loading promotes the growth and toxicity of D. acuminata populations in coastal zones

Evaluation of Rapid, Early Warning Approaches to Track Shellfish Toxins Associated with Dinophysis and Alexandrium Blooms

Marine biotoxin-contaminated seafood has caused thousands of poisonings worldwide this century. Given these threats, there is an increasing need for improved technologies that can be easily integrated into coastal monitoring programs. This study evaluates approaches for monitoring toxins associated with recurrent toxin-producing Alexandrium and Dinophysis blooms on Long Island, NY, USA, which cause paralytic and diarrhetic shellfish poisoning (PSP and DSP), respectively. Within contrasting locations, the dynamics of pelagic Alexandrium and Dinophysis cell densities, toxins in plankton, and toxins in deployed blue mussels (Mytilus edulis) were compared with passive solid-phase adsorption toxin tracking (SPATT) samplers filled with two types of resin, HP20 and XAD-2. Multiple species of wild shellfish were also collected during Dinophysis blooms and used to compare toxin content using two different extraction techniques (single dispersive and double exhaustive) and two different toxin analysis assays (liquid chromatography/mass spectrometry and the protein phosphatase inhibition assay (PP2A)) for the measurement of DSP toxins. DSP toxins measured in the HP20 resin were significantly correlated (R2 = 0.7–0.9, p &lt; 0.001) with total DSP toxins in shellfish, but were detected more than three weeks prior to detection in deployed mussels. Both resins adsorbed measurable levels of PSP toxins, but neither quantitatively tracked Alexandrium cell densities, toxicity in plankton or toxins in shellfish. DSP extraction and toxin analysis methods did not differ significantly (p &gt; 0.05), were highly correlated (R2 = 0.98–0.99; p &lt; 0.001) and provided complete recovery of DSP toxins from standard reference materials. Blue mussels (Mytilus edulis) and ribbed mussels (Geukensia demissa) were found to accumulate DSP toxins above federal and international standards (160 ng g−1) during Dinophysis blooms while Eastern oysters (Crassostrea virginica) and soft shell clams (Mya arenaria) did not. This study demonstrated that SPATT samplers using HP20 resin coupled with PP2A technology could be used to provide early warning of DSP, but not PSP, events for shellfish management

Multiple regression of <i>Dinophysis acuminata</i> abundances and toxin content per <i>Dinophysis</i> cell on environmental variables.

<p>Both models were significant at the <i>p</i><0.001 level.</p><p>Multiple regression of <i>Dinophysis acuminata</i> abundances and toxin content per <i>Dinophysis</i> cell on environmental variables.</p

<i>Dinophysis acuminata</i> densities (cells mL^-1) at the end of nutrient amendment experiments conducted during 2008, 2010 and 2011 using water collected from Northport Bay, New York. Bars are means while error bars represent the SD of triplicate bottles.

<p>Asterisks indicate treatments that are significantly different compared to the unamended control. C = Control, N = Nitrate, P = Phosphate, U = Urea, A = Ammonium, G = Glutamine, B₁₂ = vitamin B₁₂, A+ B₁₂ = Ammonium + vitamin B₁₂, STP = high molecular weight sewage treatment plant organic matter.</p

Log <i>Dinophysis acuminata</i> densities (cells L^-1), and the inorganic nutrients, ammonium, nitrate and phosphate (μM) in Northport Bay, NY, USA during 2008–2012.

<p>Points are means while error bars represent the SD of duplicate samples.</p

Chlorophyll <i>a</i> (μg L^-1), inorganic nutrients (ammonium, nitrate, phosphate, silicate), total dissolved and organic nutrients (μM) as well as nutrient ratios over the course of <i>Dinophysis acuminata</i> blooms in Northport Bay from 2008–2012.

<p>Samples were averaged across the respective inclusive dates with standard errors indicated in parentheses.</p><p>Chlorophyll <i>a</i> (μg L^-1), inorganic nutrients (ammonium, nitrate, phosphate, silicate), total dissolved and organic nutrients (μM) as well as nutrient ratios over the course of <i>Dinophysis acuminata</i> blooms in Northport Bay from 2008–2012.</p

Okadaic acid (OA), dinophysistoxins 1 (DTX1) and total pectenotoxins (total PTX) as fg cell^-1 for nutrient amendment experiments conducted using Northport Bay bloom water during 2011.

<p>Bars are means while error bars represent the SD of triplicate bottles. Asterisks indicate treatments that are significantly different from the unamended control. Abbreviations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124148#pone.0124148.g002" target="_blank">Fig 2</a>.</p

Chlorophyll <i>a</i>, and mean nutrient concentrations and ratios at the peak of the bloom compared to before and after the peak of the bloom (when cells where present) for Northport Bay 2008–2012.

<p>Values are means with standard errors in parentheses. 2009 was excluded given the low <i>Dinophysis</i> densities. Values that are italicized are those that are significantly different from each other as determined by a t-test.</p><p>Chlorophyll <i>a</i>, and mean nutrient concentrations and ratios at the peak of the bloom compared to before and after the peak of the bloom (when cells where present) for Northport Bay 2008–2012.</p

<i>Dinophysis acuminata</i> densities (cells mL^-1) at the end of nutrient amendment experiments conducted during 2011 using water collected from Meetinghouse Creek, New York.

<p>Bars are means while error bars represent the SD of triplicate bottles. Asterisks indicate treatments that are significantly different from the unamended control. C = Control, B₁₂ = vitamin B₁₂ and B₁ = vitamin B₁.</p

Peak <i>Dinophysis acuminata</i> densities and toxin concentrations in two New York estuaries, Northport Bay and Meetinghouse Creek.

<p>n.d. = not detected.</p><p>Peak <i>Dinophysis acuminata</i> densities and toxin concentrations in two New York estuaries, Northport Bay and Meetinghouse Creek.</p