Matthew Csordas1, Jennifer McHenry1, Julia Baum1
1University of Victoria, Canada
In the temperate nearshore, kelp forests sustain biodiversity and productivity through their rapid growth and formation of complex habitat, the structure and quantity of which can vary depending on the kelp species present. However, climate change is driving the loss and reconfiguration of kelp forests in many regions including the Salish Sea, a region of high kelp diversity where large expanses of bull kelp canopy have disappeared. Despite the importance and vulnerability of kelp forest ecosystems, the factors that modulate kelp community composition and species distributions on regional scales are poorly understood. By combining newly collected occurrence records from 280 underwater remote operated vehicle surveys with 175 dive transects from Fisheries and Oceans Canada and 124 towed camera surveys from Washington Department of Natural Resources, we built ensemble species distribution models for the nine most common kelp species in the Salish Sea. Using these, we examined how environment influences kelp species distributions, finding that while some species were ubiquitous on rocky substrate throughout the region, others had more limited distributions with predictor influence and response curves often suggesting a limiting role of temperature. Our models predicted that 32% of shallow coastal waters in the Salish Sea are suitable habitat for kelp, however less than half of this contained structurally complex canopy forming or stipitate species. Post hoc analyses on stacked and aggregated model predictions identified temperature and current as the main drivers of species and morphological diversity. Our results suggest that as temperatures continue to rise under future climate change, northeast Pacific kelp forests may structurally simplify through the loss of species and morphological guilds, with potentially detrimental effects on their associated communities. However, areas of high current may continue to serve as climate refugia for highly diverse kelp forests.
Biography
Matt is a PhD candidate at the University of Victoria where he works with Blue Carbon Canada, the Kelp Rescue Initiative and a number of other local groups using underwater remote operated vehicles and spatial statistical frameworks to explore the drivers of kelp species distributions. His general research interests include the drivers of species redistribution, impacts of climate change in the ocean, nature-based climate solutions, and species distribution modeling methodologies.