A trait-based assessment of the functional diversity of marine Cetacea in the Canadian Offshore Pacific Bioregion
Date
2025
Authors
Tuck, Matthew
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Abstract
The identification of biodiversity hotspots is a critical step in the protection and conservation of wildlife, and the ecosystems they depend upon. Recently, the identification of numerous highly diverse benthic seafloor and seamount habitats in the Canadian Offshore Pacific Bioregion (OPB) has prompted the establishment of large marine protected areas (MPAs) which target the protection of these sensitive benthic habitats. This region has high productivity due to eddy associated upwelling of nutrients, and contains numerous unique environments, including the continental slope, cold water seamounts, hydrothermal vents, and the open ocean. Elevated productivity supports a number of Cetacea species, which take advantage of seasonal windows of productivity. Cetaceans provide ecological functions related to nutrient transfer (e.g., the whale pump), food web processes (e.g, suppression of lower trophic levels), and the creation of unique seafloor habitats (i.e., whale falls). Despite the functional importance of these species, present conservation measures in the OPB and its associated MPAs do not legislate protections targeting the surface waters Cetacea species depend on. Here, I assess whether the OPB hosts a functionally diverse subset of the global marine Cetacea species pool through comparative analyses based on the global functional space of Cetacea spp., using seven traits related to species roles in food web processes and nutrient cycling. I also identify unique features of the species found in the OPB by comparing their trait distribution to the global Cetacea species pool. The OPB hosts 28% of the known marine Cetacea species but encompasses 70% of the global marine cetacean functional space. The functional dispersion and functional redundancy of the OPB mirrors values obtained from randomly subsampling the global species pool, indicating that the region is a representative sample of functional diversity present in the global species pool. Species using the OPB are distinguished by increased body sizes, likely due to the increased richness of large-bodied, baleen feeding Mysticeti species. The functional roles of large bodied species are fundamental for ecosystem health and stability, but are being eroded around the world as human activities continue to down-size the populations of the largest megafauna on Earth. Thus, the OPB is critical for protecting a high proportion of the global cetacean functional diversity, and the ecological roles of large cetaceans.