Award: OCE-2205604

Intellectual merit: Macroalgae at temperate latitudes are highly productive, forming the basis of food webs and providing habitat for rich ecological communities. It is thus important that we understand community structure in these key marine ecosystems which provide goods and services for many at the regional and global level. During this project we measured 30 functional traits in the field and lab for 22 core algae species in the Santa Barbara Channel and compiled a database of an additional 35 traits from the literature for all 60 species of algae. This data can then be used to predict how algae assemblages, and subsequently these crucial ecosystems will respond to global change such as stronger and more frequent storms. Experimentally, we focused on how macroalgae resist grazing by mobile invertebrates as these can impact productivity by turning kelp forests into urchin barrens. Our results were surprising in two ways and challenge the commonly held paradigm that urchins grazing on giant kelp denude these systems. Firstly, we found that other grazers eat substantially more algae than urchins, and secondly, we found that many other species of algae are grazed preferentially over Macrocystis pyrifera. Thus, we need to rethink and reframe the biological interactions that influence kelp forest dynamics. Genomes for core algae species were sequenced, more than doubling the number of available genomes for macroalgae worldwide. This will allow the exploration of how algae genomes at different geographical locales might differ, providing insight to the impact of environmental variables at the genetic level. Lastly, we curated a collection of historical maps and, along with modern remotely sensed data, were able to identify changes in kelp forest extent in Southern California over the past 100 years. Interestingly, we found that while human development had some impact on kelp loss, most decline has been bought about by large and powerful El Nio events, additionally highlighting the potential impacts of global change and how increasingly powerful and frequent storms will affect these ecosystems. Broader Impacts: During the course of this project one graduate student completed a Masters thesis, while two undergraduates completed an independent study and an REU respectively. These students were trained in all aspects of the scientific process and gained skills in the field, lab, and data analysis. All went on to present the results of their research at scientific conferences as well as write-up their findings in peer-reviewed journals. Data from these projects are also available through Data Dryad, the Environmental Data Initiative, BCO-DMO, and GenBank. Additional students helped with GIS, fieldwork, and running weekly experiments. The majority of participants were women and half were from under-represented groups. Public outreach activities involved informal events at Santa Barbara Earth Day and World Oceans Day at the Santa Barbara Museum of Natural and Sea Center. Last Modified: 04/01/2025 Submitted by: MartineWagstaff