On vacation, learning to love seaweed
Monday, September 28, 2009 at 6:14 PM
Deborah Shapley in Dugan, Griggs, Reed, beaches, birds, fishing, kelp, sea level rise, seaweed

August 2009

Tassels of brackish, dark seaweed stretch ahead of me, baking in the summer sun. I’m tempted to look up across Goleta Bay’s dark waters to the dusty blue of the Santa Barbara Channel. But I keep my eyes down to pick my way through the detritus of shells, stones, and insects, as my city feet are tend er.  It’s a lovely afternoon. The temperature is 68° F (20° C). The breeze wafts coolly from the sea. I think: Life’s a beach.

This beach is alive, actually. The dark mounds are mainly heaps of giant kelp. Explaining kelp’s importance as she leads me among the piles is Jenifer E. Dugan, a sandy beach scientist who is an Associate Research Biologist at the Marine Science Institute of the University of California at Santa Barbara. The roofs of the university buildings peek at us over the 40-foot high bluff.

Jenifer E. Dugan points out "wrack". (Author photo)This beach has always been natural, Dugan says. Giant kelp (Macrocystis pyrifera) is a vital undersea resource that grows plentifully off this shore and other parts of the channel, forming underwater forests. (For my lesson about kelp in the sea, which involved shivering eighth-graders and a shark embryo, read on.) Kelp attach to the rocky sea floor and grow to the surface where they can form extensive floating canopies that soak up light, like a forest on land. When currents yank them free or urchins gnaw them, they can get washed onshore. 

“Kelp forests are crucial elements of coastal ecosystems in California, because of the diversity of marine species they support when living in near shore ocean water. But on the beach, stranded kelp support a completely different ecosystem,“ Dugan is saying.

Baking on the beach, kelp helps thousands of shore critters to thrive–from tiny amphipods (are those the ones tickling my feet?) up the food chain to migrating shorebirds.

Look here, Jenny says. She points to the imprint left by kelp’s big leaf-like blades* on the sand flattened by the run-out of the tide. The stalk, or stipe, is still there, as are the pod-like floats filled with gas that once held the kelp upright in the water. Entwined with black surf grass, the whole is a gnarled, rumpled pile swarming with small insects and crustaceans feeding on the shrinking remains.

(*Kelp are not plants but part of the kingdom Chromista or algae, specifically brown algae. So instead of “leaves” they have “blades;” instead of “stalks” they have “stipes,” and so on.)

Scientists and conservationists want the kelp and other seaweed to remain as swarming piles to provide food for the higher food chain.  

Dugan and UCSB colleague David M. Hubbard have studied the role of this detritus on many local beaches. (1) On a similar kelp-strewn beach just to the west of the one we walked on, they counted the shorebirds’ numbers and types and biomass three times every ten days, at the same time of day, in fair weather and foul, from 1995 to 2001. These counts continue today.

You would think that shorebird abundance would correlate most with beach size.  And the beach’s area changed dramatically: it could be less than one hectare at high tide in winter yet grow to ten hectares at low tide in summer.  Yet the scientists found the number of shorebirds there did not change predictably with beach size.

Hubbard and Dugan counted 97,750 shorebirds of 26 species during the first 6 years, a huge number for any sandy beach anywhere. This beach also has been measured as receiving more than half a ton of kelp per yard (500 kilograms per meter of shoreline per year.  The abundant kelp and seaweed, known as wrack, and its swarming feeders help to explain the abundance of birds. 

Snowy Plover chick on Santa Barbara beach. (Photo: Callie Bowdish)Shorebird populations are declining in North America. (2) Some Pacific coast species, such as the Western Snowy Plover, are listed as threatened under the Endangered Species Act.  Sanderling and Western Sandpiper are on the Audubon watch list. (2)  So this study and others validate why natural beach detritus is crucial–however offensive to us at first. 

Lesson 1: Don’t clean up the beach

You knew there would be a moral for summertime beach goers from your correspondent touring the gorgeous beaches of Santa Barbara in midsummer—strictly for work.

 First, if you want to help reverse the diminishing numbers and types of birds on the coast, stop raking seaweed off the beach. About one-third of California’s 1,100-mile coast (1,610 km) is beach; almost all is in southern part of the state. Experts say a huge amount of the original natural beach has vanished as so-called civilization has advanced there.

“Grooming,” or raking the sand to remove seaweed, hurts birds and the seaside ecosystem. More groomed beaches may be good for tourism and local real estate. But—ahem—birds and natural ecosystems have value, too.

In a study of bird abundance on groomed versus natural beaches, Dugan and others at UCSB found far fewer numbers and types of birds, including the threatened plovers, on groomed beaches. (3)

I was beginning to see that what most people call good beaches as sugary wastes spread by humans so that other humans—so-called beach lovers—can run around them in neon panties.

You can view this celluloid ideal in the YouTube video "Life's a Beach", for example.  Frame after frame shows blank expanses of sand and water and a few (underweight) people. Not a hunk of seaweed nor trash nor a bottle.

The beach-as-photo-backdrop seems boring compared to the diversity and sensual surprise of the natural beach on Goleta Bay. On a natural beach, one sees a variety of birds. To make space for sandcastles, kids rake the kelp piles aside, and in doing so learn about little bugs and crustaceans.

It’s okay to let seaweed grow in the shallows. When I’ve swum off the New England coast, the seaweed lets me paddle it aside. It’s tingly when one’s feet touch slippery patches of it on the bottom.

Lesson 2: Down with seawalls

Natural beach ecosystems  are also clobbered by seawalls. Dugan explains.  that beach ecosystems are retained when bounded by natural cliffs like the bluff above us—although its messy slope, clinging plants and ragged tassel of shrubs would not pass muster in The Hamptons.

Seawalls cut off the transfiguration of stranded kelp into wrack that supports the onshore food chain. A 2005 study compared “armored” sections of beach with adjacent ones of the same length having natural bluffs, like the one here. (4) The study found that beaches and rocks in front of seawalls were washed away by waves coming inshore and by waves washing back from the walls.

The armored beaches averaged 13 to 49 feet (4 to 15 meters) wide, whereas, in the same months, the adjoining natural beaches were twice as wide. Under the walls, water and waves washed away wrack, seaweed and driftwood, leaving less prey for birds. There was less vegetation.  Beach-dependent fish were fewer.

No surprise that there were 4.3 times as many shorebirds and four times the number of gulls on the natural beach than on the remains of beach under the walls.

McMansion builders, towns and counties have added seawalls to California’s coasts.  A 1998 study by Gary B. Griggs at UC Santa Cruz found that 10 percent of California’s coast had been armored with rock, concrete and wood barriers during the previous century. The extent of the armoring increased by 400 percent between 1971 and 1992.  (5)

 Walls have come down in Washington State. The builders of Olympic Sculpture Park in Seattle pulled one down to create a natural shore and salmon habitat. (6) An old  seawall is being removed along the edge of Seahurst Park on Puget Sound for similar reasons.

Griggs predicts more seawalls will be built off the coast of California as sea level rises and as coastal storms get more severe. Meanwhile, Dugan and her colleagues are counting the ecological cost.  

 Kelp lead rich lives

Stranded kelp’s crucial role in beach ecosystems is little known compared to the value of kelp forests in the sea.

Kelp forests along the world’s coasts play host to astonishingly rich ecosystems, much as coral reefs do. (7) Off this part of California, kelp host some 600 discrete species, including the bright orange garibaldi fish, sea urchins and abalone.

Undersea kelp forest (Photo SBC staff, SBLTER)Californians have exploited kelp a long time. The forests were harvested for potash and acetone for explosives in World War One. (8) Since, they’ve provided material for fertilizer, food additives, and pharmaceuticals. Kelp is critical for the state’s hatchery-raised shellfish industry.

Dugan introduced me to Scott Simon, whose domain is a building full of tanks of sea plants and animals and a very wet floor, near the beach. The place is the REEF or Research Experience and Education Facility and it is the outreach center for the Marine Science Institute. When I arrived, Simon was finishing a five-day class for rising eighth grade girls from Tech Trek, a math-science camp that aims to whet girls’ appetite for science. The students spoke happily about what they had learned, while shuddering in beach towels. Apparently Simon’s class included undersea experiential research.

Simon admitted that kelp forests here can decline sharply during big El Ninos such as the one in 1997-1998. But the forests also regenerate fast, as kelp live just 3 to 4 years. The waters here have a huge variety of conditions that encourage a very diverse mix of species in the kelp forests. How changing conditions in the ocean and on land influence these kelp beds is the focus of the Santa Barbara Coastal LTER Project  funded by the National Science Foundation and based at the Marine Science Institute.

Dan Reed, the director of the long-term study, later confirmed that kelp’s abundance has fluctuated greatly due to human and natural causes.  “In fact the amount of kelp in California this past year was as much as it has been at any time in the last 10 to 20 years,” he said in an email. (9) Reports of a huge decline off California are often made in reference to “a survey done in 1911-1912 by row boat which showed very large kelp beds along much of the coast.”

"Modern aerial surveys of much of the California coast, done at least once per year since the mid-1960s, do not show a unidirectional downward trend in kelp abundance,“ Reed said.

Kelp forests are important, whether they’re shrinking or growing.  During my tour of the REEF, Simon, the teacher, finished this thought:

“Do we only care about a resource once we know it’s endangered?”

Among the wonders in his tanks, I noticed a shark circling. It was an adult swell shark (Cephaloscyllium ventroiosum).  Simon explained that they lay their eggs amid the kelp blades. The embryo sacs have tendrils that wrap like vines around the blades, so a sac hangs safely while the tiny shark grows inside. 

Below is Dugan with the students, Simon holding a sea urchin, and a swell shark embryo in its sac.

Deborah Shapley - August 2009

NOTES

(1) David M. Hubbard and Jenifer E. Dugan, Shorebird use of an exposed sandy beach in southern California. Estuarine, Coastal and Shelf Science 58S, 2003, pp. 41–54.  Available at www.sciencedirect.com.

(2) Morrison, R. I. G., Gill, R. E. Harrington, B. A., Skagen, S., Page, G. W., Gratto-Trevor, C. L., & Haig, S. M. (2001). Estimates of shorebird populations in North America (64 pp.). Occasional paper 104. At /www.mesc.usgs.gov/Products/Publications/pub_abstract.asp?PubID=946 . Viewed Sept 9. See generally  http://ca.audubon.org  and US Fish and Wildlife Service, “The State of the Birds.”  

(3) Dugan, J. E., D. M. Hubbard, Michael McCrary, Mark. Pierson. 2003.  The response of macrofauna communities and shorebirds to macrophyte wrack subsidies on exposed sandy beaches of southern California. Estuarine. Coastal and Shelf Science 58S:  133-148. Available at www.sciencedirect.com.

(4) Jenifer E. Dugan and David M. Hubbard. “Ecological Responses to Coastal Armoring on Exposed Sandy Beaches.” Shore & Beach Vol. 74 No 1,Winter 2006, pp. 10-16.

(5) Griggs, Gary B., email 09/16/2009. Griggs, G.B., "California’s Rereating Shoreline: What Next?" Proceedings of California and the World Ocean Conference, October 2002. Santa Barbara, California, American Society of Civil Engineers, 2005, pp. 560-573.

(6) Seattle seawall at  http://www.seattleartmuseum.org/visit/OSP/AboutOSP/green.asp

 (7) “Giant Kelp” in California’s Living Marine Resources: A Status Report, California Department of Fish and Game, December, 2001.

 (8) W.L. Scofield, “History of Kelp Harvesting in California.” California Dept. of Fish and Game Bulletin, Vol. 45, No. 3, July, 1959.

http://www.archive.org/stream/californiafishga45_3cali/californiafishga45_3cali_djvu.txt

(8) Dan Reed email, 09/24/2009.

 Deborah Shapley   August 2009.

 
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