Trophic Ecology of Nearshore Soft-Sediment Communities around Oʻahu, Hawaiʻi

Abstract

Coastal and nearshore marine ecosystems are increasingly under threat from anthropogenic stressors such as overfishing, nutrient enrichment, exotic species invasions and habitat degradation. The original research in this dissertation examines the independent and interactive effects of “top-down” predator reduction and “bottom-up” nutrient enrichment on tropical marine soft-sediment communities. Marine soft sediments represent the largest habitat type on Earth and serve as crucial feeding grounds for many commercially important species. This dissertation discusses changes in benthic microalgal (Chapter 2) and infaunal invertebrate communities (Chapter 3) during a series of manipulative field experiments. It features the latest stable isotope mixing methods used to examine the diets of infaunal primary consumers (Chapter 4). Lastly, this dissertation presents the results of a long-term observational study monitoring the bottom-up effects of nutrient addition and cessation from an open-ocean commercial fish farm (Chapter 5). The research described in this dissertation was conducted off Waimanalo and Ewa Beach, O‘ahu, Hawai‘i and offers valuable insights into ecological processes in other unvegetated sandy bottom systems.