Synthesizing disparate data for a comprehensive view of floating kelp distribution in Washington State, USA

Understanding the current distribution of floating kelp forests is critical for tracking changes to these ecologically, economically, and culturally important ecosystems. It also informs management efforts in response to threats from urbanization, climate change, and other environmental stressors. However, current floating kelp spatial datasets represent a diverse patchwork of surveys from varied time periods and with varied spatial resolution, making comparison and change analysis difficult. Here, we present a recent effort to integrate multiple datasets to comprehensively map kelp canopies in Washington State, USA. By synthesizing remote sensing data, in-situ boat-based surveys, and historical records to 1-km coastal line segments, we created a novel spatial dataset that describes the statewide distribution of floating kelp. Analysis of the most recent survey data shows that the proportion of floating kelp-containing shorelines is highest in the Western Strait of Juan de Fuca, followed by the North Coast, Eastern Strait of Juan de Fuca, and San Juan Islands. While a long time series of data exists in most of these areas, the San Juans have relatively few years of data. Proportional kelp presence is much lower throughout the rest of the state, including Puget Sound, and temporal data availability for these areas is similarly sparse. The dataset produced through this effort has enabled new approaches for statewide analyses and status reporting for floating kelp forests, and the synthesis methodology developed is deployable to other regions and species.