View in Vital Signs- Functioning Habitat
- Beaches and Marine Vegetation
- Indicator
- Floating kelp bed area
- Vital Sign Indicator
- Acre (acres)
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No targets are currently set for this indicator.
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Danielle Claar
- Contributing Partners
- Last Updated
- 05/28/2026 4:28 PM
The indicator assesses long-term trends in the extent of canopy-forming kelp forests at sampling locations throughout Washington State by tracking the area of kelp beds on the water surface. Results at each location are considered in conjunction with other information to determine an overall assessment of floating kelp status within 11 sub-basins defined by oceanography.
Vital Sign Indicator Chart. The proportion of locations in each long-trend category within each sub-basin. Sub-basins are sorted geographically, from coastal sub-basins (left) to the innermost basin (right). Hood Canal is not included because there are no sampling locations there. This figure visualizes the same location results as the map, in bar chart form. (SCO - Southern Coast; NCO - Northern Coast; WST - Western Strait of Juan de Fuca; EST - Eastern Strait of Juan de Fuca; SJI - San Juan Islands; NPS - North Puget Sound; SWH - Saratoga & Whidbey Basins; ADM - Admiralty Inlet; CPS - Central Puget Sound; SPS - South Puget Sound)
Like terrestrial forests, kelp forests form extensive living structures that provide an array of valuable ecosystem goods and services. These highly productive habitats support diverse species, ranging from small invertebrates to commercially important fish. Additionally, three categories of animals listed under the Endangered Species Act (ESA) depend on kelp habitats: rockfish, salmon, and Southern Resident killer whales.
Kelp has cultural importance to Indigenous Peoples of the Pacific Northwest. It supports traditional food sources, and plays an important role in art, spirituality, and symbolism.
Concern about kelp losses is widespread, both globally and locally (summarized in Calloway et al., 2020). In recent years, studies have shown that dramatic losses predominate in some areas of Washington State while other areas appear stable. The impacts of declines on the many species that depend on kelp are not understood. In 2020, The Puget Sound Kelp Conservation and Recovery Plan (Kelp Plan) outlined a research and management framework for coordinated action to improve understanding of trends, while also implementing recovery and protection (Calloway et al. 2020). A Kelp Plan Update was updated in 2023 (Whitty and Oster, 2023) to highlight progress, needs, and next steps.
The floating kelp indicator is produced through a unique partnership of organizations that value kelp. The group has formed an alliance for ongoing work, The Kelp Forest Monitoring Alliance of Washington State (KelpForestsWA). Indicator information is tracked on the Puget Sound Partnership’s Vital Signs program and is used by Kelp Plan implementers, the Washington Kelp Forest and Eelgrass Meadow Health and Conservation Plan, the Puget Sound Marine Vegetation Implementation Strategy, and other organizations.
- There are observed declines in floating kelp bed area in many parts of Puget Sound. Thus, we consider this indicator to be "GETTING WORSE."
- Declines have been documented in Central and South Puget Sound, with total loss at a number of sites. Over a century time scale and longer, historical ecology studies indicate that floating kelp has disappeared from approximately 63-80% of the shorelines where it was observed.
- There is substantial concern that floating kelp has declined in the San Juan Islands, based on Indigenous Scientific Knowledge and other reports.
- Total loss of floating kelp has been observed along some shorelines at the entrance to Possession Sound, which leads to concern about the state of floating kelp in Saratoga and Whidbey sub-basin. However, data gaps prevent sub-basin assessment.
- In Admiralty Inlet and North Puget Sound, spatial and temporal data gaps preclude assessment. Monitoring results at a limited number of locations did not raise major concerns.
- Along the northern open coast and Strait of Juan de Fuca, floating kelp populations are stable in the long-term, though show high interannual variability. The majority of locations in these three sub-basins show no long-term trend or increases over decades. One exception is the eastern Strait of Juan de Fuca near Protection Island, where substantial losses have occurred along some shorelines.
- Although approximately one half to one third of floating kelp locations in Washington are classified as stable, the impact of multiple stressors such as climate change, heatwaves, nutrient imbalances, and urbanization warrants caution and prompt additional research.
- This is the fourth report for this indicator, and it was made possible by a unique collaboration among a diverse group of organizations and individuals, including State agencies, Tribes, community scientists, and NGOs.
- Status assessments are necessary to inform scientific and management priorities for sub-basins. Where floating kelp is stable, conservation is a priority. Where substantial declines are documented, priorities include stressor abatement and kelp restoration. In areas with insufficient data, more research and monitoring are needed. In all areas, a better understanding of stressor distribution, magnitude, and impact is needed to conserve, protect, and restore kelp forests.
- Monitoring Program
The Floating Kelp Bed Area Indicator is produced through a unique alliance of organizations that value kelp, known as The Kelp Forest Monitoring Alliance of Washington State (KelpForestsWA).
- Data Source
The Kelp Forest Monitoring Alliance of Washington State (KelpForestsWA)
The indicator assesses long-term trends in the extent of canopy-forming kelp forests at 177 sampling locations in WA State. Trends are assessed by tracking changes in the bed area of kelp floating on the water surface through a number of monitoring methods. The general approach is summarized here (See the monitoring protocols for details).
In Washington State, two kelp species form extensive buoyant canopies that float on the water surface, bull kelp (Nereocystis luetkeana) and giant kelp (Macrocystis pyrifera). Bull kelp is widespread, while giant kelp is restricted to the outer coast and the western Strait of Juan de Fuca.
The Floating Kelp Bed Area Indicator is distinct from many other Puget Sound Vital Sign Indicators because the project team represents a broad-based alliance of organizations and communities that value kelp. A core consideration throughout the development of the Floating Kelp Bed Area Indicator was to weave together multiple ways of knowing beyond quantitative scientific datasets. Two principles drive this approach. First, diverse engagement helps to ensure that conservation efforts reflect social values (Uffman-Kirsch et al., 2020). Second, projects with widespread engagement are more likely to result in positive conservation outcomes (LeFlore et al., 2021). To meaningfully understand the complex challenges that are facing floating kelps in Puget Sound, we need a holistic and inclusive approach to research. This approach is continuously being updated and improved. Current data sources include:
· Samish Indian Nation Department of Natural Resources – classification of aerial imagery, kayak surveys, and Indigenous Scientific Knowledge.
· Northwest Straits Commission – volunteer kayak surveys conducted by Marine Resources Committees.
· The Washington State Department of Natural Resources (DNR) – classification of aerial imagery and kayak surveys.
To meet the identified needs to assess trends in floating kelp, the monitoring project has been phased to quickly provide basic information to managers and scientists while also defining a framework for incremental enhancement over time.
Methods to delineate floating kelp vary slightly among groups within the monitoring alliance. Survey techniques include small boat surveys and aerial imagery collection and classification. Data collection is restricted to summer months, when floating kelp forests are at their greatest seasonal extent. To maximize kelp detection, surveys are optimally conducted during periods of low tide, slack currents, and calm weather.
The primary statewide metric is floating kelp bed area, evaluated at selected locations throughout the study area. The bed is defined as the area encompassing kelp tissues floating on the water surface, including small gaps between adjacent individuals. This metric was selected because it has the most extensive available data, temporally and spatially. The distance threshold for grouping adjacent individuals into beds varies among individual monitoring protocols, ranging from 8 to 25 m. The program also tracks other parameters at a subset of sites, including canopy area (i.e., the area of floating individuals on the water’s surface, excluding the gaps between individuals).
Long-term trends are reported by location, with two types of spatial units: “sites” are surveyed by kayak (~1 km) and “zones” are surveyed with aerial imagery (~5-10 km). The size of monitoring locations varies with the extent of shallow subtidal habitat and also with monitoring methods – generally aerial photography captures larger zones (generally 5-10 km of shoreline) while kayaks are deployed at smaller sites (see “Critical Definitions” for location definitions). For the indicator, we assess long-trends of bed area at each sampling location by integrating information from both kayak surveys at sites and aerial imagery surveys for zones.
Long-term trends are assessed at each type of location (site and zone) using simple linear regression. Regression analysis is performed over the entire data record available for a given location. Because the indicator is based on synthesis of available data, both the length and timing of data records vary among locations. At least 5 years of floating kelp bed area data is regressed against year (a p-value < 0.05 suggests a significant trend). Regression outputs are reviewed by an expert and over-ruled (i.e., changed) if the data violates statistical assumptions (e.g., linearity) or if the result fails to consider known kelp dynamics at particular locations or time periods (e.g., total loss). Generally, locations with a significant positive trend are assigned ‘increasing’, significant negative trend assigned ‘declining’, and no significant trend assigned ‘no trend’.
Results at monitored locations are considered in conjunction with other information sources to produce an overall status assessment within each of 11 sub-basins that comprehensively span Puget Sound and the open coast of Washington State. Ideally, status would be evaluated relative to a defined baseline or target. Since neither a baseline nor a target exist for floating kelp, the status categories weave together information about change over time, condition, and information completeness for each sub-basin.
Floating kelp status determination considers long-term trend data at locations (described above) along with other information sources, including Indigenous Scientific Knowledge, historic shoreline extent of kelp based on nautical charts, expert and citizen science observations, agency reports, peer-reviewed scientific literature, and other grey literature. Status assessment considers the magnitude of change, the signal-to-noise ratio, the time scale of the change, and other uncertainties or assumptions.
- Critical Definitions
Location: the smallest spatial unit for floating kelp extent trend assessment with two types:
- Sites - individually identified areas, with a general size of ~1 km of shoreline. Surveyed by kayak.
- Zones - spanning ~5-10 km of shoreline, with boundaries placed at geomorphic features such as headlands. Surveyed using aerial photography. Zones are defined for all shorelines in the southern and northern coast, western and eastern Strait of Juan de Fuca, the San Juan Islands and DNR Aquatic Reserves.
Location trend categories:
- Increasing – positive (statistically significant) change in area over time
- No trend – no statistically significant change in area over time
- Decreasing – negative (statistically significant) change in area over time
- Total loss – floating kelp was present in the data record but absent in the most recent year
- Limited data – quantitative data is available but is not sufficient to perform regression or assess long-term changes using alternative methods
- No floating kelp – all surveys show absence of floating kelp
- No data – no surveys available
Sub-basin: the largest spatial unit for status assessment, based on large-scale oceanographic features that are associated with environmental conditions. Eleven sub-basins are delineated within Washington’s waters.
Sub-basin status categories:
- Stable – no long-term change in extent over time.
- Concern of losses – data sources suggest losses, but quantitative data lack sufficient spatial or temporal detail (low signal-to-noise ratio).
- Substantial documented decline – data sources demonstrate major losses (high signal-to-noise ratio).
- Insufficient information – data sources do not provide sufficient spatial or temporal certainty to classify the sub-basin as stable, concern, or decline.
- No floating kelp – all available data sources show floating kelp has been absent historically and is currently absent.
Indigenous Scientific Knowledge: Indigenous Science is about the knowledge of the environment and knowledge of the ecosystem that Indigenous Peoples have. It is the knowledge of survival since time immemorial and includes multiple systems of knowledge(s) such as the knowledge of plants, the weather, animal behavior and patterns, birds, and water among others. (definition from Indigenous science – Canada.ca).
Total linear extent: coastline length (in km), measured at the -6.1 m MLLW isobath (i.e., 20 ft depth). Described in the WA DNR Floating Kelp Linear Extent database (user guide, publication, WebApp)
Total nearshore extent: area (in ha) between -1 and -15 m (MLLW)
Abundance and distribution of floating kelp in Washington State
A recent effort to synthesize a wide variety of floating kelp data in Washington State to a linear extent model has provided a new look at current and historical floating kelp distribution (McKenna and Claar, 2026). The linear extent dataset simplifies disparate floating kelp data formats to annual presence or absence within 1-km coastal segments, and qualifies presence/absence with coverage category, which is a categorical estimate (0-4) of proportion of subdivided line segments in which floating kelp is present. The dataset includes floating kelp survey data used in the indicator, as well as additional sources such historical records, boat-based linear extent observations, and smaller datasets not explicitly included in the indicator.
Figure 1. a Floating kelp presence based on the most recent year of data available for each line segment symbolized as present (black) or absent (grey), representing a composite of years of data b Most recent floating kelp survey year for each line segment symbolized by color (older = cooler colors, more recent = warmer colors). Line segments last surveyed by ShoreZone, between 1995-2000, shown in grey.
Analysis of the most recent survey data shows 28% percent of coastal segments in Washington State contained floating kelp (Figure 1). Kelp presence is generally higher in sub-basins closer to the Pacific Ocean and lower in sub-basins that are further inland. According to the most recent survey data, the Western Strait (WST) had the highest floating kelp presence (96%) and proportional floating kelp coverage within segments in the most recent data, where over 75% of segments had a coverage category of 4, indicating generally continuous floating kelp coverage within that subbasin (Figure 2). The Eastern Strait (EST), North Coast (NCO), and San Juan Islands (SJI) all had similar floating kelp presence in the most recent data (52–58%), but EST had proportionally higher within-segment coverage than NCO or SJI. North Puget Sound (NPS), Admiralty Inlet (ADM), Saratoga-Whidbey Basin (SWH), Central Puget Sound (CPS), and South Puget Sound (SPS) all had floating kelp present in less than 25% of segments in the most recent data and floating kelp coverage category was spread more evenly between 1 and 4.
Figure 2. Proportion of coverage category for segments within each sub-basin in most recent survey data for each segment. Kelp coverage category shown in a gradient from light grey (0) to black (4).
An interactive web app for the linear extent dataset is available here.
Temporal and Spatial Extent of Floating Kelp Monitoring Data
A total of 177 monitoring locations are included in the indicator dataset. The time span of the data record at locations varies widely (Figure 3). The most extensive temporal record exists along the Strait of Juan de Fuca and the northern Olympic coast (Northern Coast), with more than 35 years of annual fixed wing aerial monitoring. Most locations in other regions have 10 years or fewer of data. After integrating all available data sources, four (out of 11) sub-basins did not have sufficient data to complete a definitive status assessment (Admiralty Inlet, North Puget Sound, The San Juan Islands, and Saratoga/Whidbey Basin). Note that two sub-basins (Hood Canal and South Coast) do not have any documented floating kelp.
Figure 3. The number of years surveyed, and count of monitoring locations (sites or zones) included in the floating kelp indicator. Sub-basins with an asterisk (*) also have historic data comparison studies included in the indicator assessment. Hood Canal is not included, because floating kelp has not been documented in this sub-basin, nor have repeat surveys been conducted.
The spatial extent of monitoring data varies widely by sub-basin (Main Figure and Table 1). A large proportion of the shoreline within sub-basins along the coast and strait have annual monitoring data. The northern coast (NCO) and western and eastern Strait of Juan de Fuca (WST and EST) have 65-100% coverage. The San Juan Islands (SJI) have comprehensive coverage but the time span is limited and there are uncertainties due to methodology. In Central Puget Sound (CPS) and South Puget Sound (SPS), monitoring results from a limited number of locations are augmented by extensive long-term studies. In the other sub-basins, a small portion of the shoreline has monitoring data. In these areas, assessment was driven by additional data sources (noted in presentation of results).
Table 1. Number of sampling locations and approximate percent of total nearshore habitat (between -15 m and -1 m, MLLW depth) monitored for floating kelp, summarized by sub-basin. Percent of nearshore linear extent monitored is derived from McKenna and Claar, 2026.
|
Sub-basin |
Number of locations monitored |
Percent of nearshore linear extent monitored |
Percent of nearshore linear extent with floating kelp present |
Considerations |
|
Admiralty Inlet (ADM) |
2 |
1% |
22.6% |
Sampling locations span a small percentage of sub-basin and limited time period. |
|
Central Puget Sound (CPS) |
9 |
3% |
12.3% |
Sampling locations span an extremely low percentage of sub-basin and limited time period. Comprehensive studies have identified floating kelp extent and long-term changes. |
|
Eastern Strait of Juan de Fuca (EST) |
37 |
65% |
55% |
More than 30 years of annual data for majority of sub-basin. Historical study provides century-scale comparison. |
|
Hood Canal (HDC) |
0 |
0% |
0% |
No floating kelp observations known in the sub-basin (south of Lofall). |
|
North Coast (NCO) |
22 |
100% |
58.3% |
More than 30 years of annual data for majority of sub-basin. |
|
North Puget Sound (NPS) |
11 |
6% |
26.5% |
Sampling locations span a low percentage of sub-basin and limited time period. |
|
South Coast (SCO) |
15 |
44% |
0% |
No floating kelp observed along the southern portion of open coast. Data absent in embayments, but generally not potential floating kelp habitat. |
|
San Juan Islands (SJI) |
48 |
100% |
51.7% |
Comprehensive monitoring using aerial photography. However, variability in collection methods limits trend calculation at this time. |
|
South Puget Sound (SPS) |
6 |
1% |
4.6% |
Sampling locations span an extremely low percentage of sub-basin and limited time period. Comprehensive studies have identified floating kelp extent and long-term changes. |
|
Saratoga / Whidbey Basin (SWH) |
5 |
3% |
17% |
Sampling locations span a small percentage of sub-basin and limited time period. |
|
Western Strait of Juan de Fuca (WST) |
22 |
100% |
96% |
More than 30 years of annual data for majority of sub-basin. Historical study provides century-scale comparison. |
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Multiple natural and human factors known to impact kelp could be contributing to observed patterns. Floating kelps experience a natural high degree of variability in abundance on inter-annual and decadal scales. This variability is often linked to fluctuations in water temperature via large-scale climate oscillations (Pfister et al., 2018). Other stressors include water turbidity, sedimentation, algal epiphytes, water column nutrients, and grazers (Hollarsmith et al., 2022). Sea urchins are known for their ability to completely denude kelp beds in other regions; however, this phenomenon has not been observed at a large scale in Washington State. Other grazers, such as kelp crabs (Pugettia producta) and Lacuna spp. snails may exert stronger grazing pressure, especially in areas with moderate waves and currents. Observations at Squaxin Island of large numbers of kelp crabs, along with many bull kelp with missing blades suggest that kelp crabs may be a driver of bull kelp decline at this South Puget Sound site. Sea star wasting disease (SSWD) may have decreased natural predation levels on some grazers (Schultz et al., 2016; Menge et al., 2016; Rogers-Bennett and Catton, 2019; Eisaguirre et al., 2020).
A general pattern has been observed in Washington State; concern about floating kelp losses increases with distance from the coast into Puget Sound. Along this gradient, both natural and human stressors increase. However, causes of floating kelp losses are likely site specific, and vary among locations and sub-basins. At the time of this indicator release, a collaborative project is underway to better understand spatial and temporal variability in environmental conditions at 15 sites of bull kelp loss and persistence (Claar et al. 2025b). That project, funded by the Habitat Strategic Initiative Lead (HSIL), also includes floating kelp mapping and measurements of morphometrics and condition. Initial results show that bull kelp physiological performance varies widely across Washington waters, but that there is no single ‘smoking gun’ that can explain regional trends in bull kelp (Linhardt et al. in review). It is likely that different combinations of stressors are impacting bull kelp persistence at sites throughout the southern Salish Sea. However, the spatial and temporal trends observed during this project can provide clues about specific drivers of loss within regions and at individual sites. For example, water temperature, salinity, and nitrate differ between stable and declining bull kelp sites, following a natural gradient in oceanic to estuarine conditions in the southern Salish Sea (Cox et al. in review). Declining/lost sites had warmer summer temperatures than stable sites, but bull kelp does still persist at some of the warmest sites. Furthermore, this study showed that maximum temperature is only part of the story, with some locations experiencing intermittent cooling periods that likely bolster bull kelp persistence. Declining/lost sites also had lower summer nutrient availability (i.e., nitrate concentrations), but bull kelp does still persist at some low-nutrient sites. Furthermore, this study showed that tissue nitrogen is correlated with seawater nitrate concentration, suggesting that nitrogen availability appears to constrain bull kelp growth during summer months (Pfister in review). This project has provided insight into the stressors driving losses of bull kelp forests, but continued research is needed to identify, understand, and manage stressors and to protect and restore bull kelp ecosystems into the future.
Increasing water temperatures and climate change are major emerging concerns. In many regions within the northeast Pacific, including Washington State, floating kelp populations dropped around 2014 during a marine heat wave. Floating kelp recovery in Washington State was spatially complex (Claar et al., 2025a). Along the outer coast and Strait of Juan de Fuca, total floating kelp extent rebounded in 2015. In contrast, recovery was delayed until 2017 at Cherry Point in North Puget Sound. At some sites in inner basins, total losses were observed, and beds have not recovered (such a Mukilteo in Saratoga Passage and Devils Head in South Puget Sound).
Thermal stress may co-occur with or interact with other stressors, including low nutrients. In some areas of Puget Sound during recent years, elevated water temperatures and low nutrient concentrations approached thresholds associated with decreased physiological performance and reproductive success in kelps (Hurd et al., 2014; Muth et al., 2019; Berry et al., 2021; Khangaonkar et al., 2021). However, long-term data on these parameters is lacking, so spatial and temporal patterns in temperature and nutrient concentrations are not well understood.
This is the fourth iteration of the statewide assessment of floating kelp, produced with existing data in order to address pressing needs for greater understanding of status and trends. We believe that the assessment reliably identifies broad patterns in floating kelp abundance and distribution. It also creates a model for weaving together diverse information sources in a holistic approach to synthesizing floating kelp data. Future monitoring will be devoted to further developing our understanding and linking findings to research, restoration, and conservation actions. Where floating kelp is stable, conservation is a priority. Where substantial declines are documented, stressor abatement and restoration are priorities. In areas with insufficient data, more monitoring is needed. In all areas, a better understanding of stressor distribution, magnitude, and impact is needed to conserve, protect, and restore kelp forests.
The Project Team identified priorities for enhancement of the monitoring program (discussed in the monitoring program design report). Future enhancements will require additional funding, highlights include:
1. Fill gaps in ongoing monitoring through strategically expanding spatial coverage of existing kelp bed area monitoring programs and incorporating other external datasets, especially in sub-basins identified to have limited data in the status assessment. Admiralty Inlet is an area that is notable for its paucity of available data.
2. Implement methodological improvements and expand kelp parameters through upgrading monitoring methods to incorporate new technology. Also, describe a greater range of kelp parameters such as kelp morphology, physiological performance, and condition (Pfister in review, Linhardt et al. in review). Proposed expansions could be tested first at a subset of sites. For example, DNR is working to incorporate high-resolution aerial imagery for monitoring in data deficient sub-basins (Claar et al., 2026); four years are currently available, but at least one more year is needed for quantitative change analyses.
3. Integrate existing historical datasets to increase the time span of the monitoring record. Expanding the temporal baseline will increase understanding of changes over time (e.g., McKenna et al., 2025). Historical analyses in areas such as the San Juan Islands, Admiralty Inlet, and North Puget Sound would be particularly informative.
4. Enhance geographic assessment area delineation. Complete and refine zone delineations, prioritizing adding zones in areas with new incoming data. Refine the hierarchical system over time. An updated product has just been released with 1-km segments (along the -6.1 m MLLW isobath, McKenna and Claar, 2026); this product is being used to generate zones for sub-basins where they do not yet exist.
5. Expand stressor research and linkages to environmental data. Physical and biological datasets will help to inform interpretation of monitoring results (i.e., declines or increases of floating kelp area). Build upon recent work to continue collecting and integrating environmental data at key sites (Cox et al., in review). Development of a comprehensive model for the relationship between floating kelp distribution and environmental conditions in the nearshore environment within Washington would be informative for understanding past changes and predicting future dynamics.
6. Strengthen and expand relationships with coastal communities and weave together multiple ways of knowing. Continue to integrate perspectives from Tribes, contextualizing statistical results with local knowledge to inform status in each sub-basin.
7. Continue to invest in data management and analytical capacity to ensure monitoring data are efficiently quality-controlled, analyzed, shared, and applied to conservation and management decisions (Claar and McKenna, 2026). Support coordination and data-sharing for effective integration of different data streams into the indicator.
WA Floating Kelp Indicator Project website
Monitoring program design and data assessment protocols report
A Bird's-Eye View: Mapping Washington's Kelp from the Air
Partner websites:
Washington Department of Natural Resources
References:
Berry HD, Mumford TF, Christiaen B, Dowty P, Calloway M, Ferrier L, Grossman EE, VanArendonk NR (2021) Long-term changes in kelp forests in an inner basin of the Salish Sea. PLoS One 16(2):e0229703.
Calloway M, Oster D, Berry H, Mumford T, Naar N, Peabody B, Hart L, Tonnes D, Copps S, Selleck J, Allen B, Toft J (2020) Puget Sound kelp conservation and recovery plan. Prepared for NOAA-NMFS, Seattle, WA. 52 pages plus appendices. Available at: https://nwstraits.org/our-work/kelp/
Claar DC, Berry H, Christiaen B (2025a). Geographic variability of floating kelp recovery after a marine heatwave event in the Salish Sea and adjacent open coast. PLoS One 20(12):e0336574.
Claar, D., P. Dowty, R. Hansen, D. Abbott, H. Berry, T. Cowdrey, A. Cox, M. Dethier, J. Letbetter, S. Linhardt, G. McKenna and J. Selbitschka. (2025b). Synthesis of Existing Data: A Report from the 2024-2026 Kelp Resilience Project. Washington State Department of Natural Resources, Olympia WA.
Claar, D.C., McKenna G.E., Cowdrey T. (2026) Washington State Kelp Aerial Monitoring Imagery Classification Protocols, v.1. Nearshore Habitat Program, Washington State Department of Natural Resources, Olympia, WA.
Claar, D.C., and McKenna, G.E., (2026) Washington State Bull Kelp Strategic Monitoring Recommendations. Washington State Department of Natural Resources, Olympia, WA.
Cox, A.M., Linhardt, S.T., Ledbetter, J.F., Dowty, P., Claar, D.C., & Berry, H. (2026 in review). Environmental Conditions Associated with Bull Kelp Resilience and Decline. Chapter 2 in Cox, A.M. et al., 2026a, Identifying factors associated with patterns in floating kelp loss and resilience through coordinated monitoring and research. Nearshore Habitat Program, Washington State Department of Natural Resources, Olympia WA.
Eisaguirre JH, Eisaguirre JM, Davis K, Carlson PM, Gaines SD, Caselle JE (2020) Trophic redundancy and predator size class structure drive differences in kelp forest ecosystem dynamics. Ecology. 101(5):e02993.
Hollarsmith JA, Andrews K, Naar N, Starko S, Calloway M, Obaza A, Buckner E, Tonnes D, Selleck J, Therriault TW (2022) Toward a conceptual framework for managing and conserving marine habitats: A case study of kelp forests in the Salish Sea. Ecology and Evolution 12(1):e8510.
Khangaonkar T, Nugraha A, Yun SK, Premathilake L, Keister JE, Bos J (2021) Propagation of the 2014–2016 northeast Pacific marine heatwave through the Salish Sea. Frontiers in Marine Science. 2021:1836.
Krumhansl KA, Okamoto DK, Rassweiler A, Novak M, Bolton JJ, Cavanaugh KC, Connell SD, Johnson CR, Konar B, Ling SD, Micheli F (2016) Global patterns of kelp forest change over the past half-century. Proceedings of the National Academy of Sciences 113(48):13785-90.
LeFlore M, Bunn D, Sebastian P, Gaydos JK (2021) Improving the probability that small-scale science will benefit conservation. Conservation Science and Practice 4(1): e571. https://doi.org/10.1111/csp2.571.
Linhardt, S.T., Ledbetter, J.F., Berry, H., Cox, A.M., Claar, D.C., & Dowty, P. (2026 in review) Bull Kelp Responses: Sporophyte Morphometrics and Condition. Chapter 4 in Cox, A.M. et al., 2026a, Identifying factors associated with patterns in floating kelp loss and resilience through coordinated monitoring and research. Nearshore Habitat Program, Washington State Department of Natural Resources, Olympia WA.
McKenna, G., Berry, H., Claar, D., Cowdrey, T. (2025) Mapping floating kelp presence along Seattle shorelines in 1984 using historical aerial imagery. Nearshore Habitat Program, Washington State Department of Natural Resources.
McKenna, G., Claar, D. (2026) Synthesizing disparate data for a comprehensive view of floating kelp distribution in Washington State, USA. Journal of Applied Phycology. https://doi.org/10.1007/s10811-026-03829-5.
Menge BA, Cerny-Chipman EB, Johnson A, Sullivan J, Gravem S, Chan F (2016) Sea star wasting disease in the keystone predator Pisaster ochraceus in Oregon: Insights into differential population impacts, recovery, predation rate, and temperature effects from long-term research. PLoS One. 11(5):e0153994.
Muth AF, Graham MH, Lane CE, Harley CD (2019) Recruitment tolerance to increased temperature present across multiple kelp clades. Ecology 100(3):e02594.
Pfister CA, Berry HD, Mumford T. The dynamics of kelp forests in the Northeast Pacific Ocean and the relationship with environmental drivers (2018) Journal of Ecology 106(4):1520-33.
Pfister, C.A. (2026 in review) Sporophyte Performance. Chapter 5 in Cox, A.M. et al., 2026a, Identifying factors associated with patterns in floating kelp loss and resilience through coordinated monitoring and research. Nearshore Habitat Program, Washington State Department of Natural Resources, Olympia WA.
Rogers-Bennett L, Catton CA (2019) Marine heat wave and multiple stressors tip bull kelp forest to sea urchin barrens. Scientific Reports. 9(1):15050.
Schultz JA, Cloutier RN, Côté IM (2016) Evidence for a trophic cascade on rocky reefs following sea star mass mortality in British Columbia. PeerJ. 4:e1980.
Uffman-Kirsch LB, Richardson BJ, van Putten EI (2020) A new paradigm for social license as a path to marine sustainability. Frontiers in Marine Science 7: 1–6. https://www.frontiersin.org/articles/10.3389/fmars.2020.571373/full
Whitty, J., D. Oster (2023) Puget Sound Kelp Conservation and Recovery Plan: Status Update, October 2023. Northwest Straits Initiative Report. https://www.nwstraits.org/media/3483/kelp-plan-status-update_2023oct.pdf
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