Current meter for larval and benthic ecology

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In this proposal, we request funds to purchase an instrument that can measure currents at different depths in the water. Metaxas's research focusses on populations of invertebrate organisms that live on the seafloor, such as sea stars, sea urchins, crabs, lobsters, and mussels, which have complex life cycles. As adults, they live and feed on the seafloor, but they produce larvae which may spend from a few hours to months in the water, being carried by currents. Larvae eventually move near the seafloor, attach to it and, following a sequence of morphological and physiological changes, turn into juveniles. These juveniles grow into reproductive adults. The number of new recruits that return to the adult populations will depend on the number of larvae that survive the period spent in the water column, migrate to the seafloor and transition successfully into juveniles. The proposed research will focus on factors that influence larval and juvenile survival, as well as the transition between these life history stages. Understanding the processes that occur at these early life history stages is important for the successful management of invertebrate species and fisheries, and the success of populations in marine protected areas. Current measurements will be used to interpret the distances and directions of larval dispersal. Scheibling's research investigates cyclical changes in kelp-bed ecosystems, arising from fluctuations in numbers of sea urchins that periodically overgraze seaweeds and create habitats with low biodiversity and productivity. In Nova Scotia, kelp beds recover when urchins in shallow water die-off due to disease. In deeper colder water, urchins are unaffected by disease and gradually migrate onshore resulting in renewed outbreaks. Scheibling's group is surveying the extent of these deep populations and relating patterns of urchin abundance to environmental factors, such as bottom currents. These deep-living urchins also can be an important larval source for shallow kelp beds, which in turn depends on water flow. Currents and oceanographic conditions will also determine the spread of the water-borne pathogen of urchins.