ARC CoE Coral Reef Studies

Steller sea lions (Eumetopias jubatus) are known to have occupied the same terrestrial haul-out and rookery sites across the North Pacific Rim for centuries, but it is not known why they choose and stay at these locations, or what defines their preferred habitat. Classifying and comparing the shoreline type of haul-outs and rookeries against sites not used by Steller sea lions showed that they preferentially locate their haul-outs and rookeries on exposed rocky shorelines and wave-cut platforms. However, no preference was found for selecting rookeries on sheltered shore types. Shoreline types used less frequently by sea lions included fine-to-medium-grained sand beaches, mixed sand and gravel beaches, gravel beaches, and sheltered rocky shores. Quantifying the shoreline types used by sea lions confirms anecdotal reports of habitat preferences and may prove useful in identifying and protecting sea lion terrestrial habitat, or in forecasting how climate change might affect the distribution of sea lions.

The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coral-associated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent
of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading
to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences
of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their
contribution to reef resilience and their conservation needs.