Role of the early benthic phase in regulating the distribution and abundance of marine invertebrate populations.

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The abundance of benthic (i.e. bottom-dwelling) marine invertebrates, such as barnacles, snails, oysters, crabs and seastars, varies by as much as 400% over time (year to year) and space (from one location to another). These remarkable variations in abundance have negative effects on the stability of natural communities and on the availability of species that are commercially harvested, yet the causes of these variations are not understood. There is increasing evidence that these variations are at least partly caused by low (0-40%) and variable levels of survivorship through the first few days or weeks of life on the ocean bottom (i.e. the early benthic phase), when these animals are still in the larval or early juvenile forms. It is not known, however, to what extent variations in population abundance are caused by differences in survivorship through the early benthic phase. This research program, building on more than 2 decades of research by my laboratory on early benthic phase ecology, will focus on the causes and consequences of early benthic phase mortality, and will transform our understanding of the role of the early benthic phase in controlling population abundance in benthic marine invertebrates. The program will study animals living in the intertidal zone, including barnacles, snails, mussels and crabs. The first two parts of the program will directly explore the consequences of early benthic phase mortality for population abundance: the influence of early benthic phase mortality on the subsequent abundance of the cohort up to maturity, and also its effect on the ability of species to colonize new habitats. The third part of the program will determine how low energy reserves influence early benthic phase mortality, either directly by starvation or indirectly by reducing the individual's ability to tolerate and survive stressful environmental conditions. Finally, the program will establish the influence of climate-related conditions, such as elevated temperature and desiccation stress; the program will examine the effects of these conditions at the time of juvenile recruitment on subsequent cohort abundance, and also the extent to which populations of benthic invertebrates around Vancouver Island have responded to localized climate conditions by evolving distinct early benthic phase tolerance thresholds. The study will provide breakthroughs in our ability to predict population abundance and the type of habitats these species can colonize, help us understand why early benthic survivorship is so low and variable, and lead to predictions of the impacts of climate change on early survivorship and the persistence of coastal invertebrate species.