Benthic-pelagic coupling in intertidal communities: Integrating across the life cycle of filter-feeding marine invertebrates

The ocean environment can shape patterns of distribution and abundance of marine organisms with complex life cycles through its actions on both the free-living and the bottom-dwelling stages. I evaluate how the ocean environment influences benthic invertebrates over the course of their entire life cycle, because different life-stages may respond differentially to the same ocean features, and the history of one stage may have cascading influences on later stages.; I examine spatial patterns of growth and reproduction for several intertidal filter-feeders from sites spanning Point Conception, CA, a region with a gradient in upwelling intensity. Growth rates of mussels and barnacles were enhanced at southern sites where upwelling is weak, and diminished to the north where upwelling is strong and frequent. Ocean features correlated with this spatial pattern include higher temperatures and a different phytoplankton assemblage in the region of high growth. Sites south of Point Conception also had orders of magnitude greater mussel reproductive output due to enhanced fecundity at larger sizes, and more larger, reproductive animals than northern sites. Barnacle populations south of Point Conception also had higher reproductive output than northern sites, due mostly to a larger proportion of the population brooding embryos at southern sites. The geographic gradient in reproduction was much less dramatic for barnacles compared to mussels.; There was little effect of site on egg quality of mussels, however there was large variability in egg and early larval attributes among females. Early larval mortality was especially variable among females, which may contribute to small effective population sizes. A laboratory experiment manipulating the environment of larval mussels demonstrated that nutrition influenced both larval growth and development, size and lipid stores at settlement, and post-settlement performance. Early juveniles from high larval food were larger, had more lipids at settlement, and grew faster and had better survival up to several weeks post-settlement, even in the same juvenile environment. A field study monitoring size and condition of natural settling mussels and barnacles found that both are highly variable both within and among cohorts settling within weeks of each other.