Ecological linkages between salt marshes and mudflats in Maritime Canada

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This grant will support our study of the ecology of salt marshes and mudflats in Maritime Canada. These are dynamic and biologically-productive habitats, valued for providing several ecosystem services (such as storing carbon, filtering pollution, creating nursery habitat for a diversity of organisms, and sheltering coasts from sea level rise or storm activity). Salt marshes are characterized by tough, salt-tolerant grasses able to grow on sediments regularly covered by tidal water. Mudflats are typically found on the seaward side of salt marshes; in the Bay of Fundy, in particular, the mudflats can be vast in extent, extending for several kilometres along the coast and being over a kilometre wide at low tide. The mudflats support an extraordinary abundance of invertebrates, and every summer they become essential feeding grounds for millions of migrating shorebirds. Our research program is dedicated to understanding the structure and inner-workings of salt marsh and mudflat ecosystems. As a long-term research strategy, our approach is to undertake a series of carefully-planned studies, with each study designed to address a specific question that will enlighten our overall understanding. With this grant support, we will undertake specific studies that will focus on the ecological connections that exist between the two neighbouring ecosystems. For instance, we will investigate how productivity levels are affected by the flow of organic matter from salt marshes to mudflats. A general feature of our studies is that we characterize the population and community dynamics of animal and plant species living in the salt marshes and mudflats, and we study multiple sites in two regions that experience very different tidal environments. The Northumberland Strait encounters only small tides, with clear water and strong seasonal changes in water temperature, while the Bay of Fundy is subject to huge tides, with turbid water and much smaller variation in water temperature year-round. The comparison of such distinctive sites in geographically close locations is a powerful research strategy for identifying ecological mechanisms and interpreting observed patterns. Studying the different tidal environments will also improve our understanding of how soft-sediment shorelines may be affected by changes in sea level or tidal amplitudes. Another aspect of our research is that we will investigate the impact of winter stresses and ice-related disturbances on the shoreline habitats. In particular, we will study the interface between the mudflat and salt marsh, to assess processes leading to the advancement or regression of the seaward marsh edge. We will consider the importance of winter ice (which seems to damage the marsh edge and leave it in a constant state of repair) and the prevalence of ribbed mussels (known to stabilize marsh edges in southern marshes, enabling grasses to more easily expand out onto the mudflat).