A thorough and accessible method for eelgrass restoration site selection

Abstract

Restoration of eelgrass beds is becoming a growing need as human activities result in significant impacts to nearshore ecosystems. Eelgrass provides a wide variety of ecosystem services, including food, shelter and refugia for invertebrates and fish, feeding habitat for birds, nutrient cycling, carbon sequestration and carbon storage. It provides surface area for epiphytic algae that serve as the base of the food web for salmon and forage fish, stabilize shorelines and buffer wave energy. They also serve as excellent areas for science and education (Orth et al. 1984, Thompson 1994, Bostrom and Bonsdorff 2000, Duarte 2000, Molnar 2015). The rates at which eelgrass beds capture and store carbon can be up to 90 times that of forests (Campbell 2010) and continue for up to 40 years following restoration (Thom et al 2012). From an economic perspective, eelgrass meadows around the Lower Mainland provide $80,929 in ecosystem services per hectare per year (Molnar et al. 2012). Natural limiting factors for eelgrass growth include temperature (0° to 30°C but ideally 10° - 20° C; Phillips 1984), light availability, depth, substrate (usually mud or sand), wave action (relatively low) and salinity (20 - 32 ppt in the Salish Sea; Durance 2002). Human impacts on eelgrass include dredging and filling (Levings and Thom 1994); turbidity, smothering and anoxia from woody debris generated by forestry activities (Phillips 1984, BC/Washington Marine Science Panel 1994); pollution (BC /Washington Science Panel 1994, Beak Consultants 1975, Lyngby and Brix 1989); shading, damage and reduced circulation due to overwater structures such as docks (DFO et al. 2003); damage from boating and mooring (pers. obs.) and spread of invasive species such as Spartina sp. and the European green crab (Carcinus maenas). Coastal development pressures are likely to increase impacts on eelgrass as the climate changes, due to coastal squeeze during landward movement (Nicholls et al. 2007) and increased erosion and scouring associated with amplified wave impacts on hardened shorelines.
There is growing recognition that restoring eelgrass beds can improve habitat connectivity and resiliency, and contribute to mitigating climate change effects. With competing priorities restricting government budgets for eelgrass restoration, however, communities and non-profit organizations are playing a greater role in eelgrass restoration. It is important to identify how such efforts can be supported to maximize their success.