Neurotoxin in a Louisiana estuary: quantitative analysis of domoic acid in gulf menhaden (Brevoortia patronus) and qualitative modeling of links in a shark nursery

Harmful algal blooms are an increasing problem for coastal waters world-wide. The diatom genus, Pseudo-nitzschia, is of particular concern in Louisiana, due to the potential for several species to produce the neurotoxin domoic acid (DA). While trophic transfer of DA to consumers has repeatedly occurred along the California coast, little is known about trophic transfer of recently detected DA in the Gulf of Mexico. In this study, the presence of DA in gulf menhaden (Brevoortia patronus) and the potential for trophic transfer to higher order consumers was investigated. In addition, the effects of this transfer and other algal toxins that threaten Louisiana’s coastal food webs were evaluated. DA quantification in water and fish tissue samples was determined by Enzyme-Linked Immunosorbent Assay (ELISA). Food web effects of algal toxins were analyzed through the use of a qualitative modeling technique, loop analysis. The results of the toxin assay illustrated that low-levels of DA exist in both water and tissue samples, with a significant correlation between the two (n = 25, p = 0.025, significance level of 0.05). The effects of HABs on the entire food web showed the possibility of trophic cascades. This is the first documentation of a DA vector in the entire Gulf of Mexico and confirms DA contamination in food webs of coastal Louisiana. Through the use of qualitative modeling, present and future threats posed by phycotoxins to coastal food webs can be assessed, providing resource managers valuable information to aid in mitigation of their negative consequences.