Award: DEB-2050017

This project had four major goals. First, to extend long-term datasets on physical and ecological changes occurring at multiple rocky intertidal shores to enable assessment of the impacts of environmental variability on the animals and plants living on the rocks. Second, to determine if populations of the ochre sea star Pisaster ochraceus had recovered from the massive sea star wasting disease event of 2014. Third, to inform the public about these findings, particularly sea star recovery. Fourth, to build scientific capacity by training cohorts of graduate and undergraduate students and technicians in the theory, methods, and approaches of ecological research at local to geographic spatial scales and through time. A good fraction of the undergraduates have gone on to graduate school.

Over the duration of the grant, we discovered several outcomes relevant to our goals. First, sea star recovery has been mixed, with abundances and body size patterns returning to the patterns we documented before the 2014 wasting event at about half of our study sites. Some sites even appeared to recover, then "unrecovered", reverting to the post-wasting pattern of domination by tiny juveniles rather than the pre-wasting pattern of domination by large adults. This was a consequence of a major shift in dynamics towards high input of new individuals as tiny (about 1-3 mm in diameter) sea stars. Prior to 2014, these "recruitment" events never happened and the appearance of even a few such tiny sea stars was noteworthy. This shift is ongoing, with huge inputs of sea star recruits to several of our sites each year including up to 2026. 

Second, because the sea stars are major predators of mussels and typically keep them from moving to lower shore levels, we expected that as a consequence of sea star wasting and attendant loss of most sea stars, mussels would invade the lower shore. To our surprise, this response was also mixed. At some sites, or even specific locations within a site, mussels did move down, but very slowly, often taking years longer than prior studies had observed, and in some cases not changing at all. The reason for this minimal response was at least partly due to low input of new mussels to the existing mussel populations. In the years following sea star wasting, and coincidental with the 2014-2016 marine heat wave and the 2015 El Niño, mussel colonization of the shore was sharply reduced. This shift seems likely due to negative effects of warmer than usual waters on mussel larvae while they are in the plankton. This trend persisted through the during of the just completed grant.

Third, we have succeeded in maintaining our long-term datasets, and have used these in several recent publications to assess temporal changes in the system and seek likely explanations for the changes. These data were crucial in understanding the long-term consequences outlined above for sea stars and mussels, and contributed greatly to the power of our data to gain insights into how the abiotic environment influences the biota over unusually long time spans.

Fourth, our work continues to attract graduate applicants, undergraduates eager to gain research experience, and the public through direct interactions and media interviews (television, radio, blogs). We routinely field requests for updates on sea star wasting and impacts of marine heat waves on rocky shores. 

Finally, our accomplishments during the 2021-2026 LTREB grant position us to gain keener insight into the impacts of ongoing ocean warming on an iconic marine ecosystem. Meteorologists have detected a massive north Pacific heat wave that has formed in 2026, and also forecast a major El Niño to occur in 2026-27. We are poised to assess the response of rocky shore biota to these stresses.

Last Modified: 05/30/2026
Modified by: Bruce A Menge