Salish Sea Marine Survival Project

42 THE IMPORTANCE OF NEARSHORE HABITATS FOR PACIFIC SALMON WHY? Nearshore marine habitats are of great ecological and economical importance. Eelgrass meadows are among the most productive and sensitive nearshore habitats, providing shelter and food to numerous species including salmon, and forage fish such as sand lance and herring. They also improve water clarity by filtering polluted runoff, reduce negative impacts of ocean acidification and protect shorelines from erosion by absorbing wave energy. Another critical role of eelgrass meadows includes miti- gation of climate change. Eelgrass absorbs carbon from the atmosphere through photosynthesis and buries it in underlying sediments, isolating it from further circulation in the carbon cycle, often for thousands of years. This sequestration process is often referred to as the production of "blue carbon". In BC, roughly 400 km 2 of salt marsh and eelgrass meadows stash away as much carbon as BC's portion of the boreal forest or the equivalent of the emissions from 200,000 cars. Eelgrass habitats are threatened by human activities and have been documented as decreasing in area and abun- dance throughout many areas of the Strait of Georgia. It is hypothesized that this decline could contribute to the poor marine survival of Coho and Chinook Salmon juveniles in recent decades. However, there is a lack of understanding of the relative threats that are causing the decrease of eelgrass beds in this region. Similarly, bull kelp habitats have been shown to provide important feeding and refuge conditions for Chinook and Coho in the Strait. They form extensive forests in rocky habitats along the subtidal zone of the coast of British Columbia. Bull kelp forest habitat has been in steady decline within many areas around the Strait of Georgia for the last several decades. The reasons for the decline, which have resulted in patchy kelp habitat in many parts of the Salish Sea, are unclear and still being studied. This phenomenon is seemingly widespread on the Pacific coast of North America. QUESTIONS ADDRESSED DATA CONCLUSIONS What is the value of nearshore habitats to juvenile salmon? What is the impact of anthropogenic stress on these habitats? How can we mitigate these impacts and allow for successful restoration? Numerous SSMSP studies have examined kelp, eelgrass and marsh habitats in the Strait of Georgia. Data include: snorkel surveys; aerial photos, drone and satellite imagery; use of stable isotopes to examine source of salmon diet; examination of otoliths to determine loss of Chinook life history variants in degraded estuaries; and genetic studies of kelp and eelgrass. Estuaries play an important role for protection and rearing of juvenile salmon, especially of smaller fry, and allow for diversity in salmon production. Estuary degradation appears related to anchorage scour, shoreline activities and alterations, and contaminants. Reproductive capacity of bull kelp is reduced at warmer temperatures.

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