Tiny shrimp-like crustaceans living beneath California beaches may be playing a surprisingly large role in reshaping the coastline. New research finds that sand hoppers can excavate as much as 110 pounds of sand per meter of shoreline each day, putting their sediment-moving activity on a scale comparable with some major coastal processes.
The creatures, known as sand hoppers (Megalorchestia spp.), spend much of their time burrowing into damp beach sand and feeding on kelp washed ashore. Despite measuring only centimeters long, their collective digging can dramatically disturb beach sediments.
“They have one of the highest rates of bioturbation of anything on the planet,” said UC Santa Barbara marine scientist David Hubbard, referring to the process in which living organisms displace and mix sediment.
The findings, published in the Journal of Geophysical Research: Earth Surface, suggest that animals living within sandy beaches deserve greater consideration when scientists examine how sediment moves through coastal environments.
Tiny Crustaceans Act as Coastal Engineers
Sandy beaches may appear relatively stable, but they are part of constantly changing sediment systems. Waves, currents and wind continually move sand along the shoreline, while rivers, streams, coastal cliffs, dunes and offshore deposits can provide additional sediment.
Researchers have extensively studied these physical processes, but the contribution of beach-dwelling animals has received less attention.
Tim Baxter, a physical geographer who conducted postdoctoral research at UC Santa Barbara and is now a research fellow at the University of Oxford, became interested in determining how much sand the abundant crustaceans actually move.
“We combined our interests and started thinking about the abundance of sand hoppers around UCSB, but also across California,” said Baxter. “That got us asking, how much are they digging? What are they contributing to the sediment system and sediment transport on these beaches?”
Sand hoppers typically burrow about 4 to 12 inches into the beach or shelter beneath washed-up seaweed. They emerge after dark to feed on kelp wrack.
Researchers Measure Overnight Excavation
To quantify their activity, researchers conducted a field experiment at Isla Vista Beach near the UC Santa Barbara campus.
Following high tide on a summer night, the team placed metal frames within the part of the beach favored by the crustaceans. Sand hoppers avoid both extremely wet and very dry sediment, instead concentrating in areas where moisture allows their burrows to remain stable.
“They don’t like saturated sand that’s like liquid—their burrows collapse immediately,” Hubbard explained. “They don’t like the powdery dry sand above the high tide line. They like the Goldilocks sweet spot in between where the burrow will stay intact because the moisture in the sand is just right.”
Unlike some animals that repeatedly use the same burrow, sand hoppers dig new ones as they seek favorable moisture conditions. That behavior means recently shifted sand can be excavated again after being moved by waves or wind.
When researchers returned the following morning, the amount of digging was immediately apparent.
“When we came back in the morning, we couldn’t even see some of the frames,” Hubbard recalled. “They were completely buried, and we were so glad we had put flags next to them just in case.”
After collecting and weighing the excavated material, the researchers calculated that sand hoppers could move as much as 110 pounds of sand per meter of shoreline per day.
“It was quite impressive and we weren’t really expecting that,” Baxter said. “I think for me that was the biggest shock.”
Burrowing Could Influence Beach Ecosystems and Erosion
The findings expand scientists’ understanding of the ecological importance of sand hoppers. The animals already occupy an important position in coastal food webs by consuming washed-up kelp and serving as prey for shorebirds and fish.
Their digging also transports organic material deeper into beach sediments.
“There’s a huge churn,” Hubbard explained. “If food like kelp or carrion gets deposited on the beach, it’s going to get buried by them, which makes it available to a different group of organisms.”
Burrows can also aerate sediment, providing oxygen that supports microbial activity. At the same time, freshly excavated sand may become more vulnerable to wind and water erosion.
“It potentially increases the roughness of the surface of beaches, which has implications for the formation of landforms such as coastal sand dunes.”
That potential influence is particularly relevant as coastal dunes are increasingly considered a nature-based tool for reducing flooding and helping shorelines withstand stronger waves, storms and rising seas.
Small Animals Operating at a Large Scale
When researchers extrapolated their measurements across roughly 15.5 miles of Southern California coastline, they found that the quantity of sand displaced could be comparable to daily sediment loads from some major Southern California rivers and to coastal processes that transport sand along beaches.
The research contributes to the growing field of biogeomorphology, which examines how organisms interact with and alter landscapes.
“I think part of that is the influence of animals on these processes is seen as quite temporary, quite localized and small,” Baxter said. “What we are trying to show in this study is that actually these activities and interactions are operating on a much larger scale and that their impacts are really worth”
The findings highlight how even some of California’s smallest coastal inhabitants can collectively influence the physical environment. By continuously excavating, mixing and redistributing beach sediment, sand hoppers may be an overlooked force in the processes that shape sandy shorelines.
Alexander Donovan writes for News Collective, covering news, politics, business, technology, sport, entertainment, and lifestyle. He focuses on clear, reliable reporting and useful information, helping readers stay informed about current events, emerging trends, and stories that matter.