Kelp wrack. Photo Credit: Kyle Emery
Marine scientists at UC Santa Barbara are revealing how closely linked sandy beaches and nearby ocean habitats are along the California coastline. Although land and sea are often viewed as separate systems, subtle physical and ecological interactions connect them. In particular, the size and health of offshore kelp forests play a key role in shaping the strength and complexity of food webs on adjacent beaches.
In a study published in Nature Scientific Reports, lead researcher Kyle Emery and his team examined these linkages in detail. Their findings emphasize that when ecosystems are strongly interconnected, disturbances in one area—such as kelp forests—can trigger cascading effects in neighboring environments like beaches. The research, funded by the National Science Foundation, adds to growing evidence that coastal ecosystems function as integrated systems rather than isolated units.
At first glance, sandy beaches and nearshore waters may seem unrelated due to their distinct environments and species. However, earlier studies have shown that kelp washed ashore—known as wrack—forms an important bridge between them. Because sandy beaches typically produce little of their own food at the base of the food web, this deposited kelp becomes a crucial external source of nutrients.
Emery explained that the amount of kelp reaching the shore largely depends on the supply available offshore, which varies along the coastline. Building on this idea, the study explored how differences in kelp wrack influence beach ecosystems. The researchers wanted to understand how changing kelp inputs affect beach communities and ecological processes.
A kelp forest located offshore of a Santa Barbara County beach. Photo Credit: Kyle Emery
To investigate, the team surveyed 24 beaches spanning about 100 kilometers across Santa Barbara and Ventura counties. They measured the quantity of kelp wrack arriving on shore and evaluated its ecological effects. This included tracking nutrient and carbon contributions from decomposing kelp, as well as examining the structure of beach food webs—from small invertebrates that consume kelp to predators like shorebirds. They also estimated the energy required to sustain these organisms.
The results showed that kelp wrack has strong, direct effects on beach invertebrates, both as a food source and as habitat. These impacts extend upward through the food web, influencing higher-level consumers such as birds. Greater kelp input leads to more pronounced ecological effects, while declines in kelp forests are likely to negatively impact multiple species and ecosystem functions on beaches.
Beyond demonstrating the link between ocean and shore, the study highlights the ecological importance of maintaining natural, ungroomed beaches. Many urban beaches are cleared of kelp and flattened for aesthetic purposes, but this removes a critical resource. While previous work has shown that dunes and vegetation help protect coastlines from rising sea levels, this research underscores the biological value of leaving beaches in a more natural state.
But in reality, a pristine beach is one that is biodiverse, highly functioning and has lots of kelp wrack with all the invertebrates thriving off those inputs and transferring energy up to higher trophic levels like shorebirds.
Emery noted that people often imagine an ideal Southern California beach as wide, flat, and free of debris. In reality, a healthy beach is one rich in biodiversity and ecological activity, where kelp wrack supports thriving invertebrate communities and sustains higher trophic levels such as shorebirds.
Additional contributors to the research included Jenifer E. Dugan, David M. Hubbard, Jessica R. Madden, Robert J. Miller, and J. Carter Ohlmann, all affiliated with UC Santa Barbara’s Marine Science and Earth Research Institutes.
Adapted from reporting by Sonia Fernandez, “Kelp forests connected to sandy beach food webs,” The Current, UC Santa Barbara, 2026.