Puget Sound is home to five species of seagrass, and several hundred species of macroalgae, including over a dozen species of kelp. These plants and algae serve as critical habitat for a wide variety of organisms, including several fish species that are listed as endangered or threatened under the Federal Endangered Species Act.
Eelgrass (Zostera marina) is by far the most abundant seagrass in greater Puget Sound, growing mostly in the intertidal and shallow subtidal in muddy to sandy substrates and low to moderately high-energy environments.
The term kelp refers to a group of large brown macroalgae in the order Laminariales. These algae are found throughout greater Puget Sound, and are often the dominant vegetation in intertidal and subtidal habitats with solid substrate.
Eelgrass and kelp are both provide incredibly productive habitats and serve important ecosystem functions, including the following:
- Producing large amounts of carbon, which contribute to both local and distant food webs.
- Creating structurally complex habitat to provide refuge for marine species.
- Supporting high biodiversity and serve as important habitats for forage fish and juveniles of salmonids.
Eelgrass and kelp are sensitive to stressors such as climate change, physical disturbance, and eutrophication, and are considered important indicators of habitat condition and ecosystem health. Both eelgrass and kelp are included in the Puget Sound Partnership’s list of Vital Signs for Puget Sound recovery.
2020 Marine Vegetation Monitoring
In 2020, Snohomish County signed an agreement with the Washington State Department of Natural Resources (DNR) to conduct a comprehensive survey of marine vegetation (eelgrass, understory kelp and other macroalgae) at 10 sites along the Snohomish estuary, from Hermosa Point (North of Tulalip Bay) down to Port Gardner, using methods developed for DNR’s monitoring programs. This effort supplements existing and planned future sampling by DNR, and significantly increases the certainty in local estimates of eelgrass area and depth distribution over existing data from the DNR’s Submerged Vegetation Monitoring Program (SVMP).
Through this partnership, DNR surveyed the shoreline along the Snohomish estuary in August 2020, and produced a detailed report of their findings in December 2020. Key findings from this report include the following:
- Marine vegetation in the study area was dominated by eelgrass and green algae, which is expected for intertidal and shallow subtidal estuarine habitats dominated by sandy substrates.
- The depth distribution of marine vegetation was similar to other sites in the Saratoga Whidbey basin, but more restricted in maximum depth as compared to Central Puget Sound.
- At 6 out of the 10 sites sampled, a change in eelgrass area over time was able to be assessed. Eelgrass area has increased over time at 3 sites along the shoreline between Mission Beach and Priest Point. Eelgrass has declined in Tulalip Bay and in the center of the Snohomish delta. The declines in Tulalip Bay are part of a longer-term trend. Declines at the center of the Snohomish delta may be due to natural variability at this highly dynamic site. Both locations are a priority for future monitoring.
For more information, view the full report here: Eelgrass, kelp and other macroalgae near the Snohomish delta - Final report to Snohomish County
2021 Marine Vegetation Monitoring
In 2021, Snohomish County signed an agreement with DNR to conduct a comprehensive survey of marine vegetation (eelgrass, understory kelp and other macroalgae) at 22 sites along the shoreline of Snohomish County, between Edmonds and Everett, using methods developed for DNR’s monitoring programs. Four additional sites were surveyed for eelgrass in 2019 and 2020. This effort supplements existing and planned future sampling by DNR, and significantly increases the certainty in local estimates of eelgrass area and depth distribution over existing data from the SVMP. It also serves as a baseline for classification of other marine vegetation types.
Main findings include:
- The intertidal and shallow subtidal were colonized by a variety of marine vegetation types, which often displayed different zonation at individual sites.
- The depth distribution of marine vegetation was similar to other sites in the Central Basin of Puget Sound.
- We were able to assess change in eelgrass area at 8 out of the 26 sites in the study area. At 7 of these sites, there was no significant trend in eelgrass area over time. At one site (swh1649) there was a small increase over time between 2005 and 2019.
For more information, view the full report here: Eelgrass, kelp, and other macroalgae in South Snohomish County - Final report to Snohomish County
Kelp Monitoring Overview
Bull kelp (Nereocystis leuktean) is the largest species of brown algae native to our region. This fast-growing seaweed can grow as much as 60 feet in length in a single year and is an important part of the rocky inter tidal ecosystem. It serves as both a primary producer in the food web of Puget Sound and as shelter and habitat for fish, invertebrates, marine mammals, and birds. In addition, the intricate structure of this living habitat buffers against current and wave energy, to help protect the nearshore ecosystem.
In the Puget Sound, there have been noticeable declines in bull kelp abundance. While it is unclear what has caused these declines, potential factors include toxic pollutants from storm water, erosion, high sedimentation deposition, and overpopulation of kelp predators.
In response to concerns over bull kelp decline and as part of our nearshore conservation goals, Snohomish County MRC seeks to understand how much kelp habitat is currently available in local waters. Towards that end, all seven regional MRCs throughout the Puget Sound are continuing to gather data as part of the Northwest Straits Commission’s Regional Kelp monitoring project (2016) which contributes to an expanding regional story map and interactive Arc GIS database that tracks changes in number of kelp beds and total acres measured. MRC members recently completed our monitoring via kayak in August 2020.