The effects of water column and sediment carbonate chemistry on infaunal invertebrates in New Brunswick, Canada

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University of New Brunswick


Understanding how infaunal invertebrates are affected by the properties of overlying water and the sediment in which they live is critical for better understanding their ecology. Here, I focused on the impact of water column and sediment carbonate chemistry on infaunal invertebrates. First, in a laboratory experiment I found that semidiurnal intermittent CO2 addition provided refuge for soft-shell clam (Mya arenaria) housed within sediment. The M. arenaria in the semidiurnal CO2 treatment grew more similarly to the M. arenaria in the control water than the constant CO2 treatment, which had reduced growth. Better mimicking of natural conditions through the inclusion of variability showed that, contrary to the literature, M. arenaria may not be as negatively impacted by predicted future oceanic conditions. I completed a field experiment to investigate the impacts of altering sediment carbonate chemistry, through the addition of transplanted green algae and/or crushed shell hash, on the infaunal community of an intertidal mudflat. After one month, sediment pH was impacted by the addition of shell hash but not of algae. For the community composition, there was an interaction between shell hash and algae treatments. However, the effects of the treatments were small compared to natural small scale spatial variation. In month two, the sediment pH and community responses to the experimental treatments had disappeared. Multivariate statistical modeling indicated that sediment pH explained variation in infaunal communities in both experimental and control plots. Next, I considered which abiotic variables, in both the sediment and the water column, influenced unmanipulated infaunal invertebrate communities and bivalve species abundance in two regions in New Brunswick, Canada, one along the coast of the Bay of Fundy and one in the Southern Gulf of St. Lawrence. I found that sediment pH explained the 17% of the variation in the multivariate analysis for the Bay of Fundy while water alkalinity was included in the top models for most of the univariate modeling of biotic metrics in both regions. My research found that sediment carbonate chemistry is influential for infaunal invertebrates and, will play a role in the response of infaunal invertebrates to future oceanic conditions.