Date of Award

Winter 12-3-2020

Document Type

Thesis: Open Access

Degree Name

MS Marine Science


Environmental and Ocean Sciences

Committee Chair

Drew Talley

Committee Member

Theresa Talley

Committee Member

Nathalie Reyns


Sandy beaches are high-energy impact zones that produce little to no organic material. Much of the organic matter on beaches is washed up on shore in the form of algal wrack, providing a vital source of nutrients, food, and habitat for a variety of organisms on the sandy beach. Over time wrack will decay and decompose, releasing nutrients including nitrogen and phosphorus, which are consumed by benthic microalgae and bacteria. The type of wrack and geomorphology of the beach environments affect decomposition, which in turn supports a variety of different wrack associated macrofaunal communities. Different species of algal wrack will support different species of animals, and can affect the taxonomic composition and number of species present. My research used a combination of manipulative and mensurative experiments to identify wrack associated macrofauna on a San Diego beach. I used the giant kelp species Macrocystis pyrifera to compare wrack associated macrofaunal community composition and abundance over a period of 21 days. There were higher abundances of macrofauna within the algal wrack relative to bare sand, and macrofaunal abundance increased over time in the algal wrack. Community composition within the wrack varied over time, with abundance changing by orders of magnitude. These results reinforce other findings demonstrating that algal wrack is an important primary food source and strongly influences macrofaunal communities and higher trophic levels. In the San Diego area algal wrack is an important component of the land-sea interface ecosystem.