Soundwide eelgrass area is a metric for the overall health of native seagrass beds in greater Puget Sound. Seagrass is an important component of nearshore habitats, and is sensitive to human disturbance. Seagrass responds to changes in water quality, and can be used as indicator of eutrophication.
Long-term trend in soundwide eelgrass area (acres) in greater Puget Sound. The dark grey bar represents the 2000-2008 baseline, light grey bars are annual estimates of soundwide eelgrass area, and the dashed line shows the recovery target of a 20% increase in eelgrass area relative to the 2000-2008 baseline by 2020. Error bars are standard error.
Key Vital Sign Indicator Results
The current best estimate of eelgrass area in greater Puget Sound is approximately 56,000 acres (rolling average 2017-2019).
Soundwide eelgrass area was relatively stable between 2000 and 2019. The relative stability is reassuring and sets Puget Sound apart from many other developed areas, where substantial system-wide declines are ongoing.
While the majority of sites appear stable, the spatial pattern in site level trends suggests that eelgrass is more susceptible to declines in certain areas of greater Puget Sound. Declines are mostly centered in South Central Puget Sound and near the San Juan Islands. Eelgrass seems particularly vulnerable at the end of inlets or in protected embayments.
Likely drivers for local declines include water quality impairments, eelgrass wasting disease, high abundance of green macro-algae, and changes in river flow patterns across deltaic flats.
At this point in time, it seems unlikely that the recovery target of 20% increase in eelgrass area by 2020 will be met. Stressors that affect eelgrass in Puget Sound will likely need to be reduced to see significant soundwide gains in eelgrass area, depth distribution and overall health.