The role of filter-feeders in coastal ecosystem functioning

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Human interactions with the coastal zones of our oceans can compromise marine ecosystem health. For example, the cultivation of mussels and oysters can alter the food supplies available for other species. In addition, the man-made structures that are deployed in the ocean for this purpose constitute new habitat that can be colonized by other species such as sea squirts (tunicates). Some sea squirts are invaders that can rapidly proliferate and out-compete mussels and oysters, dominating the ecosystem, and negatively impacting the economic viability of the aquaculture sector. Assessing the overall impact of this human activity on the ecosystem relies on our understanding of the feeding behaviour of mussels, oysters and sea squirts. These so-called filter-feeders feed by straining small food particles from water, typically by passing the water over a specialized filtering structure. Despite the importance of filter-feeders in coastal ecosystems, some critical aspects of their feeding behaviour are still not clear. This proposed research program will improve our understanding of the feeding behaviour of mussels, oysters and two species of invasive sea squirts. This research will determine (1) the size and type of particles that these species can effectively retain in their filtering structures, (2) their feeding rates and behaviour under different environmental conditions, and ultimately (3) their potential impact on the ecosystem. We will achieve these goals by performing experiments in the field and under controlled conditions in the laboratory, for example, to explore the effect of a higher future ocean temperature on filter-feeder feeding rates. We will also integrate this novel information into mathematical models that could be used to predict the behaviour of these species under current and future ecosystem scenarios such as climate change or human modifications to the coastal zone. The knowledge to be gained from this research will improve our ability to make informed management decisions for Canadian coastal zones. For example, we will be able to (1) explore the impact of mussel and oyster aquaculture on the environment and consequently provide recommendations to guarantee the sustainability of this important economic activity; (2) simulate predicted climate change in the laboratory to explore the anticipated future invasive pattern of sea squirts. In summary, this program will generate fundamental scientific knowledge that can be directly applied to improving coastal zone management in Canada, and will help to promote sustainable aquaculture practices worldwide.