No clear relationships between environmentally classified ecosystems and species diversity

A more objective classification of an ‘ecosystem’ and the relationship between ecosystems and species diversity could aid in their use in conservation planning. The growing availability of environmental data with depth has allowed for more comprehensive modelling of the distribution of marine ecosystems in space, their connection to species diversity and their role in contributing to conservation management. We provide the first comparison of surface and near seabed marine ecosystems and their associated species diversity. We used long-term averages of 17 ocean variables to classify the surface and near seabed waters in the exceptionally species-rich West Pacific. A total of 12 distinct ecosystems—defined as enduring regions demarcated by ecologically relevant environmental characteristics—were identified in both surface and near seabed depths. Species assemblages differed among ecosystems. However, 6 methods of estimating species richness found neither a simple relationship between ecosystems nor clear patterns associated with latitude, depth, area or temperature, reflecting the varying latitudinal and environmental conditions prevalent in each ecosystem. Thus, while ecosystems comprise part of biodiversity, they cannot be used as a surrogate for species richness.