Research Reveals That Wrack Rescues Rather Than Ruins Fragile Beach Ecosystems
• Seminar at City Hall Reveals That Kelp Is Key to Maintaining and Restoring Shore Ecology
BY SUZANNE GULDIMANN
Beach ecology was in the spotlight at a special seminar at Malibu City Hall last week.
"A lot of people don't think about beaches as ecosystems," Karen Martin, professor of biology at Pepperdine University, told the audience. "The traditional way to think about beaches is as playgrounds and hazards. We want to start thinking about them as ecosystems."
Martin, who 10 years ago developed the successful "Grunion Greeter" program to promote awareness and gather data on the small California fish that spawns on local beaches during spring and summer high tides, is currently involved with the non profit Beach Ecology Coalition and focused on the importance of natural, undisturbed kelp wrack in maintaining a healthy and vibrant ecosystem on Southland beaches.
"All over the world [people are] concerned about what's happening on beaches," Martin said. [Beaches are] wildlife habitat. She quoted journalist John Balzar, who wrote, "Where the sand turns wet, the greatest wilderness on the planet begins."
"There are beach wildflowers-native plants not really seen except on beaches, nowhere else in world," Martin said, adding that beaches are also nurseries for many animals, ranging from marine mammals like sea lions, to grunion, a wide variety of invertebrates, and endangered bird species, including the least tern.
"There are also reptiles-the silver sand lizard, sea turtles. We're starting to get sea turtles more and more in Malibu, visiting, not breeding, but resting on shore. [It's] critical habitat necessary for animals to complete their life cycle."
Martin explained that mechanized beach maintenance, using heavy equipment to rake the beach and remove kelp, can transform key habitat into a wasteland.
"On a completely groomed beach there are no grunion eggs left." Martin described the look as a "Zen garden."
"When you groom like that, yes, you may have nice clean beach but you lose something that can't be replaced," she said.
According to Martin, the area where grunion deposit their eggs in the sand "is not as easily demarcated as some people would like, it's in between the highest tide line and mean tide line."
Her grunion research has led to modifications in beach grooming on several Southern California beaches. "It's maintenance modification to avoid impacts to California grunion nests," she said. "It's not a loss of grooming or an end of grooming but a change to how grooming is done.
"Here in Malibu they do modify their grooming practice. We've had really good cooperation with LA County Beaches and Harbors. " According to Martin, county beaches are left ungroomed from the middle of March until the middle of August to accommodate the grunion.
"Kelp doesn't help the grunion but it does have other benefits for a lot of different animals," Martin said.
Martin also discussed "coastal squeeze," a term for beach development or coastal armoring that leaves little room for natural sand. "Armoring of the coast is a very big issue, especially in California," Martin said. "Sand replenishment is poorly understood and understudied. It can change biology of beach for a while. That's a concern.
"How can we assess what is a healthy beach? Lot of things are monitored on sandy beach but nothing to look at the big picture. Beach report cards are looking mostly at bacteria that can harm humans, not the environment," she said
The second guest speaker at the city-sponsored event was Jenifer Dugan, a professor of biology at UCSB who has studied kelp for seven years.
"[Kelp is a] food source for many species, they starve without it," Dugan said. "Fresh kelp is immediately colonized by a variety of organisms. Grooming or raking actually transforms beaches from vital habitat into barren stretches of sand. It's the same way leaf litter is important to a forest."
"We need to not only value beaches as places were humans can enjoy but as places that support wildlife that can live no where else," Dugan said. "Beaches are becoming more and more critical as habitat for shorebirds."
Dugan explained that beaches are increasingly providing habitat for birds that previously depended on California's ever shrinking wetlands.
"Beaches also function like giant sand filters," Dugan said. "Water is pumped in twice a day into the sand lens and filtered, there are all kinds of bacteria that break down material, as it breaks down [it is] actually providing nutrients. There is connectivity between beaches an other ecosystems."
Dugan said that California's beaches have some of the highest density of biomass and number of beach invertebrate species in the world. "You can't belittled how rich these beaches are," she said.
Dugan discussed how macrophyte wrack—on Malibu beaches comprised primarily of giant kelp—is consumed by isopods, kelp flies and beetles, which in turn provide prey for shorebirds
"If you change what happens to the kelp, you change what happens to the animals that depend on the kelp. [There is an] important need for kelp to be there, and go through natural succession. The level of animals is drastically lower on groomed beaches. Species richness on groomed beaches is very low."
Dugan conducted an experiment in Santa Barbara that involved removing wrack by hand on sections of beach. She found that the more wrack her team removed, the fewer invertebrates were present. "Even on a 25-meter-wide plot the shorebirds and invertebrates didn't use it, I think they moved over to the other [control] plots. Dugan said the invertebrates and shorebirds came back after the project ended.
She described groomed beaches as "plowed, transformed, really unnatural."
"They should be dunes," Dugan said. "At Broad Beach and Zuma the vegetation, given its druthers, actually comes way out [onto the beach]. We've lost a whole vegetated zone. It's a very large impact. Underestimated, especially if you want to have sand stay on your beaches. Dunes store sand. Wrack encourages sand to collect and form mini dunes."
Dugan also stated that coastal armoring has a serious impact on biodiversity. "With coastal armoring we lose those dry and damp upper zones as coast retreats. The high tide line is on the wall instead of on the beach. There's a huge decline in wrack accumulating, and species decline, even gulls and sea birds.
"One thing [you can be] proud of in Malibu is all of the ungroomed beaches," Dugan said.
More information on Karen Martin's research and the Beach Ecology Coalition is available at: www.beachecologycoalition.org
Information on Jenifer Dugan's research is online at http://sbc.lternet.edu/external/Outreach/Beach_Resources/SeaGrant-Dugan_LA.pdf
The City of Malibu also has a section on beach ecology on its official website: http://www.malibucity.org/index.cfm/fuseaction/detail/navid/88/cid/19421/