Long-term changes in coastal ecosystem structure and functions: understanding the effects of harvesting, habitat alteration, and climate change

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Coastal ecosystems are important structural and functional components of the ocean and provide essential services to human well-being, including seafood production, nutrient cycling, recreation and coastal protection. Yet they have been deeply transformed over historical time scales and continue to be altered by multiple human activities. In order to assess and properly manage marine resources and coastal ecosystems today and for the future, it is essential to understand the range, magnitude and consequences of long-term changes in the past. Like knowledge of a patient’s medical history greatly improves the success of diagnosis and treatment, reconstruction of historical changes provides critical context for current study and management. My research program is unique in providing this historical context while analyzing ongoing changes and their consequences at the ecosystem scale. We have made significant progress in assessing historical changes in marine populations, particularly for vertebrates such as mammals and fish. We synthesized both the extent of population declines over past centuries and recent recoveries due to increased conservation, and quantified major ecosystem consequences, such as changes in biodiversity, food-web complexity and stability. Yet while vertebrates have received increased protection and management, exploitation of marine invertebrates and plants is rapidly expanding, both in Canada and around the world, with little population assessment and largely unknown ecosystem consequences. In contrast to most fish, invertebrates and plants often play important ecosystem roles beyond predator-prey relationships, including habitat provision, water filtration and nutrient cycling. These low-trophic level species are also sensitive to increasing climate variability and nutrient loading. Over the next five years my research will therefore reconstruct long-term changes in marine invertebrates and plants, and analyze their consequences for coastal ecosystem structure, functions, and the services they provide for humans. Specifically, we will assess historical research surveys and fisheries statistics to derive long-term changes in the abundance and distribution of marine plants and invertebrates. To understand the consequences of observed changes, we will employ meta-analysis of experimental and field data to quantify the ecosystem functions and services provided by these species, including habitat provision, water filtration, detritus removal, carbon storage and nutrient cycling. As a third element, we will build food-web models from field-survey data and use coastal ecosystem models from around the world to analyze the consequences of marine plant and invertebrate harvesting on other species of commercial and conservation interest, and overall ecosystem structure and functions. Finally, we will use laboratory experiments to test the effects of climate warming and nutrient loading on habitat-building plants and their associated communities. Experimental results and global climate models will then be used as inputs in our ecosystem models to assess the broader consequences of projected climate change on marine ecosystems. Taken together, the proposed work will fill critical knowledge gaps that are important to understand past and ongoing changes in the coastal ocean, predict their broader consequences for marine ecosystems and human society, and inform an ecosystem-based approach to marine management and conservation. As such, this research will support managers and decision makers, and benefit resource users and society as a whole. It will advance our fundamental understanding in marine ecology, environmental history and ecological forecasting, and train students in an innovative, inter-disciplinary research field.