| Summary: | Warming of the earth’s surface from the atmospheric greenhouse effect is altering climate processes and patterns worldwide. In the Pacific Northwest region of the U.S. and Canada, climate change is expected to result in rising sea level, stronger winter storms, warmer and wetter conditions in winter and spring, and increased water column stratification and acidification. Pacific Northwest seagrasses inhabit the intertidal and subtidal zones of energetic open shorelines and protected coastal embayments and provide valuable ecosystem services. Here we: 1) describe expected changes in the Pacific Northwest of six climate related components– temperature, storminess, precipitation and runoff, sea level rise, coastal upwelling, and ocean acidification, 2) evaluate the potential impacts of these changes on seagrasses on the outer coast and in the Salish Sea, 3) identify critical issues and data gaps, and 4) explore implications for seagrass research, restoration, resilience, and adaptation in the Pacific Northwest. A synthesis of first-order impacts suggests that there may be more negative than positive impacts of Pacific Northwest climate change on seagrasses; however, some processes will likely have disproportionate effects. For example, seagrasses such as Zostera marina benefit several-fold from increasing seawater CO2 concentrations. Indirect effects, such as algal blooms, trophic interactions, disease, and human activities could also affect seagrass resilience and adaptation in a changing climate.
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