Kelp beds are highly productive nearshore habitats that support commercial and sport fish, invertebrates, marine mammals and marine birds. Many factors, both natural and anthropogenic, affect the extent and composition of kelp beds. For example, elevated water temperature and intense sea urchin grazing can decimate kelp beds. El Nino events stress kelp by producing several winter storms and reducing upwelling events, which normally replenish the nutrients in the water column. Human influences on kelp beds include sewage and other runoff that decrease water quality and reduce light in the water column. Human activity can also lead to changes in substrate size, which can either increase or decrease available kelp habitat. Kelp plants can be physically damaged by boat propellers and fishing gear. Commercial harvest is not a significant factor of concern in Washington State due to a law prohibiting this practice.
The Nearshore Habitat Program surveys and monitors kelp in Puget Sound and along the open coast.
Bull Kelp Monitoring in South Puget Sound
Major concerns exist about bull kelp declines in Puget Sound. Recent research shows that bull kelp extent is limited in South Puget Sound, the southernmost inner basin in Puget Sound, and has decreased since 2013.
Long-Term Monitoring of Floating Kelp Along the Outer Coast and Strait of Juan de Fuca
The Nearshore Habitat Program has conducted annual aerial surveys of floating kelp canopy extent since 1989. Two species of canopy-forming kelp are monitored: Bull kelp (Nereocystis luetkeana) and giant kelp (Macrocystic integrifolia).
- Read the DNR blog summarizing floating kelp dynamics reserch between 1989 and 2015.
- Explore storymap of current and historical floating kelp distribution.
- Download GIS Data - Annual kelp inventories on the outer coast and Strait of Juan de Fuca from 1989 to 2014 (44.7 MB .zip file).
- Explore the kelp data interactively with the Washington Marine Spatial Planning mapping application.
- Read a recent annual monitoring report.
Recent Publications that include DNR kelp research and collaborations (most recent first)
- Recreational kelp harvest on DNR Aquatic Reserves - Kilgo et al. 2019.
- Kelp beds and their local effects on seawater chemistry, productivity, and microbial communities - Pfister et al. 2019. Ecology.
- Impacts of suspended sediment on nearshore benthic light availability following dam removal in a small mountainous river: in situ observations and statistical modeling. Glover et al. 2019. Estuaries and Coasts.
- Successional dynamics and seascape-level patterns of microbial communities on the canopy-forming kelps Nereocystis luetkeana and Macrocystis pyrifera. Weigel and Pfister. 2019. Frontiers in Microbiology.
- The dynamics of kelp forests in the Northeast Pacific Ocean and their relationship with environmental drivers. Pfister, Berry and Mumford. 2018,Journal of Ecology.
- From the predictable to the unexpected: kelp forest and benthic invertebrate community dynamics following decades of sea otter expansion. Shelton et al. 2018. Oecologia.
- Increased sediment load during a large-scale dam removal changes nearshore subtital communities. Rubin et al. 2017. PLOS ONE.
Kelp Surveys Throughout Washington State
View nearshore vegetation data in an interactive map.
Find more inventory datasets for kelp and other nearshore habitats.