Dr Kira Krumhansl1, Dr Ben Lowen1, Mr Cody Brooks1, Dr Claudio DiBacco1
1Fisheries And Oceans Canada, Dartmouth, Canada
Kelp losses on the order of 85-99% have been documented in Nova Scotia, Canada since the mid-1900s due to the synergistic effects of climate change and invasive species. In many areas, kelp forests have given way to carpets of turf comprised of up to 99% by biomass of invasive red algal species. However, luxuriant kelp beds exist in some areas, and the coast of Nova Scotia is now a complex mosaic of turf and help habitat. Environmental and biotic drivers of this habitat variability have not been well-resolved. In this study, we use 20-70 year time series of kelp abundance at data at 50 sites spanning the Atlantic Coast of Nova Scotia to identify areas of resilient kelp forests and link this to metrics of environmental variability. These metrics span basic measures of annual mean to maximum temperatures to more complex variables, including temperature variability over daily and seasonal time scales, growing degree day, and heat wave intensity and duration. With the metrics most strongly correlated to kelp loss and resilience, we develop a metric of kelp environmental sensitivity and map areas of the coast based on the level of environmental risk to kelp populations. These maps will support marine protected area planning by identifying areas that have and may retain resilient kelp populations into the future. Our study also supports a more complex understanding of the conditions under which kelp loss occurs in Nova Scotia and allows for more refined predictions of where kelp may persist into the future.
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