The relative roles of physical and biological factors in larval supply and recruitment of marine benthic invertebrates

Invertebrate organisms that live on the bottom of the ocean, such as crabs, lobsters, clams and sea urchins, have complex life cycles. As adults, they live and feed on the bottom, but they release sperm and eggs in the water column, and fertilization occurs externally. The produced embryos develop into larvae and may spend from a few hours to months in the water column, being carried around by currents. After they mature, larvae move near the bottom, attach to it and, following a sequence of morphological and physiological changes, turn into juveniles. These juveniles look and live on the bottom like young adults. Obviously, 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. Thus, understanding the processes that occur at the larval stage is important for the successful management of invertebrate nuisance species and fisheries, and development of aquacultural practices. Although, we understand the factors that affect survival of adults because of their relatively large size and the accessibility of their habitat, we know little about larval and juvenile survival. We will study factors that regulate larval and juvenile survival. We will examine how larvae respond to cues in their environment, such as water flow, temperature gradients and the presence of predators, in the laboratory. We will also study the ecology of early life history stages in two alien species in Nova Scotia. We will measure the effects of the interaction of juveniles of the alien green crab with those of native crab species on food consumption and growth rates. For a bryozoan invasive, we will measure larval supply by sampling larvae in the water and on the bottom at different sites throughout the year. We will also measure rates of colonization on algae and environmental characteristics, such as temperature and currents. In laboratory experiments, we will observe larvae grow under different temperatures and measure how larvae behave under different current flows and thermal gradients. Lastly, using new technologies, we will measure larval abundance and colonization rate after disturbance in the deep sea using the cabled observatory NEPTUNE in the NE Pacific.