Karina Nielsen loves going to the beach as much as any Californian — and may love it even more than most. That's because as a marine ecologist, she knows those long sandy stretches that look so empty are actually busy with life. "So many of the organisms are buried that it's not always apparent, especially compared to tidepools," she says.
But stand in the swash zone where surf meets sand, and you are likely to see shorebirds running back-and-forth to catch invertebrates and sand crabs digging to get away, and feel small crustaceans called isopods nipping at your toes. The sandy depths are also full of creatures from molluscs to worms. And those seaweed piles further up the beach that most of us avoid? They're alive with beach hoppers or amphipods, another kind of small crustacean. Together, all those invertebrates seen and unseen support the surfperches swimming in the surf zone and an amazing community of shorebirds, including marbled godwits, sanderlings, turnstones, whimbrels and willets, to name just a few.
Nielsen, a biology professor at Sonoma State University, applied her sandy beach expertise as part of a team that monitored this ecosystem along California's North Central Coast. The team also included co-leaders Steven Morgan of UC Davis and Jenny Dugan of UC Santa Barbara, as well as their graduate and undergraduate students. Their goal was to establish a regional baseline for the state's new network of Marine Protected Areas (MPAs). Besides serving as a benchmark for any future changes, this work characterized sandy beaches and how they are used for the first time, giving us an entirely new view of this key habitat.
The team monitored 17 beaches over two years after MPAs were established in the region, surveying beach wrack (seaweeds, seagrasses and surfgrasses deposited on the beach), key coastal life (birds, surfperch and invertebrates) and people's activities. "My favorite part was the monthly surveys," Nielsen says. "I got to leave my busy life and walk incredible beaches when it was stormy, calm, sunny or rainy. We got the pulse over the seasons."
Another highlight was the sand biodiversity surveys, which entailed taking 20-by-10 centimeter cores of sand. "We squealed with delight when we found anything new," she says. "It was a magnet for other people on the beach — they had no idea there was anything under the sand, it was great!" Altogether the team found 67 invertebrate species in the region's sandy beaches, with perhaps 20-30 of these on any given beach.
Besides surveying beaches, the team refined the citizen monitoring protocol for sand crabs and developed a new one for surfperches. "Fly fishing in the surf zone is a new niche and we had an expert who came on almost every trip," Nielsen says. "We had plenty of volunteers because they wanted to learn from him."
The team found that beaches were typically similar inside and outside of MPAs. The exception is a good one: while people and off-leash dogs can disturb shorebirds that nest, rest or feed on beaches, this type of disturbance was less common on MPA beaches.
Another key finding is that there are striking differences between long and pocket beaches, emphasizing the importance of including both beach types in long-term monitoring of this ecosystem. Long beaches are unbroken stretches of sandy shoreline that extend for a kilometer or more, while pocket beaches are shorter and are surrounded by steep or rocky cliffs.
Not surprisingly, more people visited long beaches, using them mostly for fun and relaxation. Common activities included walking, resting, socializing, beach and water sports, and play.
Another difference between the two beach types is that long beaches are rich in gulls, seabirds and shorebirds, while pocket beaches are dominated by terrestrial birds including blackbirds, crows, flycatchers and ravens. This is a new observation of how bird species are distributed between beach types.
Pocket beaches also had more wrack, and the team found that the number of fresh kelp plants washing up along the shore's edge is an excellent predictor of all the kelp wrack strewn across the entire beach. Kelp deposition peaked in November, averaging more than 2,000 plants per kilometer on pocket beaches versus fewer than 200 plants per kilometer on long beaches.
Indicators for future citizen scientist monitoring
Based on their surveys, the team concluded that long-term monitoring could be narrowed to monthly or seasonal observations (during, say, birds' fall and spring migrations) of indicators that can easily be surveyed by citizen scientists. Volunteers could walk transects to survey birds, people, dogs, and fresh kelp plants. Likewise, citizen scientists could team up with researchers to survey the sand crabs — a good predictor of total invertebrate abundance — that surfperches and shorebirds feast on.
"We have a lot of people out on beaches doing this kind of work already with Audubon, Beach Watch, and LiMPETS," Nielsen notes. "We could coordinate, refine and expand their work to help keep an eye on the ecological health of the North Central Coast's sandy beaches."
Check out the regional snapshot for more information about this and other North Central Coast baseline monitoring projects. Visit the North Central Coast MPA Baseline Monitoring Program page for updates, data, and results from this project.