Common European Harmful Algal Blooms affect the viability and innate immune responses of Mytilus edulis larvae

As the human population continues to expand, scientists and politicians are faced with a simple question: will we be able to feed ourselves in the future? Many of our food sources are at peak productivity and only in a few sectors, such as the aquaculture industry, is significant growth feasible. However, these sectors are also faced with global concerns like climate change. The rise of sea surface temperature will affect marine ecosystems in drastic ways. Among others, pathogens and harmful algae are expected to benefit from a warmer environment. As a result, both wild and cultured bivalves will become more frequently exposed to these stressors. Yet, to date, little is known on the physiological and immunological effects of harmful algae on bivalves. In this paper, we demonstrate that the most common European harmful algal blooms are able to affect the sensitive larval life stage of the blue mussel.

Scientific abstracts

Like marine diseases, harmful algal blooms (HABs) are globally increasing in frequency, severity and geographical scale. As a result, bivalves will have to face the combined threat of toxic algae and marine pathogens more frequently in the (near) future. These stressors combined may further affect the recruitment of ecologically and economically important bivalve species as HABs can affect the growth, viability and development of their larvae. To date, little is known on the specific effects of HABs on the innate immune system of bivalve larvae. This study therefore investigates whether two common harmful algae can influence the larval viability, development and immunological resilience of the blue mussel Mytilus edulis. Embryos of this model organism were exposed (48h) to five densities of Pseudo-nitzschia multiseries or Prorocentrum lima cells. In addition, the effect of six concentrations of their respective toxins: domoic acid (DA) and okadaic acid (OA) were assessed. OA was found to significantly reduce larval protein phosphatase activity (p < 0.001) and larval viability (p < 0.01) at concentrations as low as 37.8 μg.l-1. P. multiseries (1400, Plima (150 and DA (dosed five times higher than typical environmental conditions i.e. 623.2 μg.l-1) increased the phenoloxidase (PO) innate immune activity of the mussel larvae. These results suggest that the innate immune response of even the earliest life stages of bivalves is susceptible to the presence of HABs.

Full reference (link)

De Rijcke, M., Vandegehuchte, M.B., Vanden Bussche, J., Nevejan, N., Vanhaecke, L., De Schamphelaere, K.A.C., Janssen, C.R., 2015. Common European Harmful Algal Blooms affect the viability and innate immune responses of Mytilus edulis larvae. Fish and Shellfish Immunology. Accepted Manuscript