Kelp Monitoring

kelpKelp 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. The Nearshore Habitat Program also facilitates the Washington State Kelp Research and Monitoring Workgroup


In May 2023, a new statewide floating kelp indicator was released to inform management and research actions. An alliance of diverse organizations completed the project, including the DNR Nearshore Habitat Program, The Samish Indian Nation, The Northwest Straits Commission and the county Marine Resource Committees, University of Washington, Sea Grant and Marine Agronomics. The indicator will be added to The Puget Sound Partnership’s Vital Signs.

Floating Kelp Forest and Nearshore Habitat Monitoring with Aerial Imagery

Starting in 2022, the DNR Nearshore Habitat Program began collecting 4-band aerial imagery of floating kelp forests and nearshore habitat across a large portion the state’s shorelines. This imagery is being analyzed to determine floating kelp bed extent and canopy area. These results are being used to inform the floating kelp forest Indicator for Washington State, as well as the recently passed Kelp Forest and Eelgrass Meadow Health and Conservation Plan (2SSB 5619).


The Nearshore Habitat Program and AQR GIS Unit have been investigating the use of UAS or “drones” for marine vegetation mapping since around 2016. In 2021, Nearshore began conducting annual UAS surveys of floating kelp forests at a series of key monitoring sites throughout Puget Sound to complement other survey methods with detailed spatial analyses of canopy distribution and trends. UAS represent a critical component of our multitiered approach to long-term kelp forest monitoring and stressor research.
  • 2024 Report - Monitoring Puget Sound Bull Kelp Forests with Multispectral UAS
  • 2021 Demonstration project with the Northwest Straits Commission using UAS and aerial imagery at volunteer monitoring sites – StoryMap and Report.

Bull Kelp Monitoring in South and Central 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 2021 (72 MB .zip file).
  • Explore the kelp data interactively.
  • Read a recent annual monitoring report.

DNR kelp research and collaborations (most recent first)

  • DNR is leading a collaborative stressor research project (2024-2027): Identifying factors associated with patterns in floating kelp loss and resilience through coordinated monitoring and research – 
  • Effects of temperature and nutrients on microscopic stages of the bull kelp (Nereocystis luetkeana, Phaeophyceae). Weigel et al. 2023.
  • Interactive effects of temperature and nitrogen on the physiology of kelps (Nereocystis luetkeana and Saccharina latissima). Fales et al. 2023.
  • Collaborative Project with the Northwest Straits Commission on data synthesis and recommendations for the MRC Volunteer Kelp Monitoring Program – report
  • Demonstration project with the Northwest Straits Commission using aerial imagery at volunteer monitoring sites – storymap and report
  • Puget Sound Kelp Conservation and Recovery Plan.
  • 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 pyriferaWeigel 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.

Historical Data Sources used in Kelp Research

Our research projects use some historical data sources that can be challenging to locate:
Phillips, R. 1962-1963.  Original field notes from shallow subtidal surveys by scuba and snorkel at sites in Puget Sound for Seattle Pacific College and University of Washington.  146 p. Full Text Available (9105 KB PDF)
Thom, R.M. and L. Hallum.1990. Long-term changes in the areal extent of tidal marshes, eelgrass meadows and kelp forests of Puget Sound.  University of Washington Wetland Ecosystem Team. Final Report to US EPA Office of Puget Sound, Region 10.  FRI-UW-9008, EPA 910/9-91-005.  June, 1990.  Seattle, WA. 116 p. Full Text Available (2618 KB PDF)
West, J.E. 2019.  Personal communication regarding observations of Nereocystis luetkeana by the Washington Department of Fish and Wildlife during rockfish surveys in South Puget Sound during the 1992 field year.  Olympia, WA  . 1p. Full Text Available.