Summary PROJECT INACTIVE

In this project, we are comparing historical photographs of sites in the southern reaches of the Southern California Bight with similar views taken in 2015-16. Mussel beds showing extensive areal covers of very large individuals in the 1960s and 1970s were greatly diminished or completely absent by modern times. Several lines of evidence indicate the collapse is driven by rising sea surface temperatures and falling ocean production. The mean size of matrix mussels diminished, suggesting reduced growth rates as a result of declining ocean productivity. The vertical range on the shore has contracted for each bed, as predicted by models with reduced mussel recruitment and growth. A 33-year time series of panorama photos of intertidal communities in Southern California show a stepping down of areal coverage, entailing steep declines coinciding with El Nino events and stasis in the intervening years. The El Nino/La Nina cycles were embedded in a long-term trend with the late 1970s marking the end of a 30+ year period of relatively cool SSTs and the beginning of the el nino events. An agency-run survey of many sites along the coast shows the effect is spreading to northward, with no indication of recovery.

Student Involvement

This project has provided training opportunities for 4 CSUMB undergraduates.

Broader Significance

This project is providing insight into the long-term effects of climatic shifts on the composition of rocky intertidal communities in Southern California and the ecosystem services that they provide. The results of this study will also provide baseline data for modeling future shifts in rocky intertidal communities resulting from climate change.