Marie-Josée Abgrall

PhD candidate (2006 -)

MS in Marine Biology, University of Central Florida, FL
BSc in Biology, Laval University, PQ

Project: "Effects of organic matter and hydrogen sulfide on habitat selection behaviour, and resuspension of larvae and post-larvae of the softshell clam Mya arenaria"

Dissolved hydrogen sulfide (H2S) is a constituent of nearly all marine sediments and its production in sediments is normally not detrimental to marine organisms. However, infaunal organisms can be exposed to higher levels as the formation of H2S in sediments is often correlated with an accumulation of organic matter. Breakdown of H2S by bacteria can lead to considerable depletion of O2 in the sediments and therefore, turn the substrata into an unsuitable habitat for larval settlement and early juvenile survival.

My PhD project is to determine how detrimental the effects of high H2S concentrations in the sediments can be for M. arenaria, a commercially important species in New Brunswick, and to determine the overall impact on the species recruitment.

The first part of this research project will look at the larval habitat selection and behaviour during substratum exploration prior to settlement, and the minimal H2S concentration and organic matter concentration needed to induce settlement and post-settlement behavioural modifications in the larvae and post-larvae.

Then, the second part will investigate the resuspension rate of larvae and post-larvae at different H2S and organic matter concentrations. Finally, the third part of this research project will look at the effect of different H2S and organic matter concentrations on the lipid content of the competent larvae and post-larvae as an indicator of the health and survival potential of the individuals.

In addition of controlled experiments conducted at the Marine Centre in Shippagan, comparative experiments measuring resuspension rates and quantifying population structure will be carried out in the field at various sites along the Northumberland Strait in New Brunswick.

This research will provide a better understanding of how sediment geochemistry affects settlement and post-settlement behaviour of shellfish, and underscore the importance of understanding the processes that affect recruitment of benthic marine invertebrates, a fundamental element of population dynamics.