Wednesday, November 28, 2007
Fishermen and windsurfers call it weed, but eelgrass (species name Zostera marina) is actually not a simple, algal seaweed. It's a seagrass, an evolutionary descendent of complex land plants with real leaves and roots. Eelgrass' roots let it live on soft sand and mud, creating a structural habitat where there would otherwise be nothing. The species Zostera marina is widespread in the Northern Hemisphere but is at its Southern limit in Virginia and struggles during our hot summers. In other parts of its range, like the clear waters of California's Channel islands, it grows deep down where you have to scuba dive to get to it. I showed this picture in a talk I gave at the Western Society of Naturalists meeting, not knowing who the random diver was. It turned out to be a guy in the audience!
In the cool, damp Pacific Northwest, eelgrass can survive being exposed to the air at low tide. I remember seeing eelgrass on the sand flats when I was a kid digging for razor clams in Birch Bay, Washington.
In Chesapeake Bay, eelgrass is confined to the narrow area just below the low-tide line. Here, Matt Whalen from the Virginia Institute of Marine Science is pushing a net to catch crabs and stuff living in the grass.
The diagram below shows why eelgrass can only inhabit a narrow depth range in the current Chesapeake Bay.
Basically, the water is too murky for eelgrass to grow down deep, and it's too hot for it to grow really shallow. It wasn't always like that, though. Before the middle 20th century the water was clearer and eelgrass was able to grow down deeper, covering a much greater portion of the Bay.
What makes the water murky? It's a couple different things. Algae in the water (aka phytoplankton) turn it greenish and block out much of the light. Dirt in the water (aka suspended sediment) makes it a muddy brown and blocks out still more light. As a final insult, algae called "epiphytes" grow directly on top of the eelgrass and steal whatever light is left.
Human activities on land can result in more algae and dirt in the water. Sewage and runoff muddy the water directly with the sediment they contain, but also make the water murky indirectly by fertilizing algae. When algae run wild from exessive fertilization, it's called "eutrophication". Besides making the water murky for seagrass, eutrophication is responsible for "Dead Zones" where rotting algae remove all the oxygen from the water and make it uninhabitable for fish and crabs.
On top of that, the effects of global warming on eelgrass are already starting to be felt. There is always a bit of a decline in eelgrass during the hottest part of the summer, but in 2005 it really got hammered by an unprecedented number of days of water temperatures over 30 degrees celsius. The data below are from monitoring that VIMS does at Goodwin Islands, a nearby nature reserve that used to be surrouned by eelgrass beds, but now has just a few bits left (dark coves on the Southeast side). The red box highlights where the hot summer knocked out eelgrass. Though it came back in 2006 at Goodwin Islands, other spots in the Bay still haven't recovered.
I've been concentrating on the bad news, but there are some hopeful things I should mention. For example, some animals in the bay might be able to help eelgrass recover. Oysters are filter feeders that clean and clarify the water. They used to be so abundant in the bay that they formed massive reefs, and their collective filtration significantly improved water quality. If we could bring them back to that level, they would reduce the impact of the excess sediment and nutrients that human society dumps into the water.
Another group of animals is important as well; the little bug-like things that eat epiphytes, the algae that grow on top of eelgrass blades. Some recent experiments have shown that these bugs are just as important to the health of eelgrass as is clean water.
That brings up an interesting question- what controls the abundance of the algae-eater bugs? We know that they're connected to other animals in the bay through the food-chain, so it's possible that changing the abundance of big fish could indirectly affect the abundance of algae-eaters, with serious consequences for eelgrass.
With all these different things affecting eelgrass, what should we do to save it? Well, I think we should try a diversified strategy. On land we should try to limit urban sprawl and preserve as many forests and wetlands as possible to keep dirt and excess nutrients from entering the bay. We can advocate for better farming practices so farms don't release as much fertilizer and sediment, and we can eat less meat so we don't need as much farmland in total. It will also help to have more trees and natural vegetation around houses, roadsides, and streams. In the water, we should make protecting and restoring oysters a number 1 priority, even if that means stopping all oyster harvesting and shifting to oyster aquaculture to provide oysters for eating. As for the algae-eating bugs, we need to learn more about the Chesapeake Bay food chain to find out the best way to protect them. Last but not least, we need to stop and reverse global warming. That means conserving energy, driving less, recycling, and voting smart. If we do all this, the future Chesapeake Bay may regain the eelgrass beds and oyster reefs of it's pre-20th century glory. :)
Tuesday, November 27, 2007
Thursday, November 22, 2007
All through the day I've been reflecting on past Thanksgivings and some of the nice memories I have accumulated...
The first one that I remember was ages ago in deep, dark Olympia, Washington. We had friends visiting from Seattle. I can't recall exactly who was there, but they were from what we call the "playgroup"; a close-knit network of 6 or 7 liberal yuppie families who bonded when they all had babies around the same time. The playgroup stayed together and became like an extended family as the kids grew up. Anyway, that Thanksgiving there was a rare, early snowstorm and the power went out at our house. I remember my folks cooking stuff on the woodstove, and us eating by candlelight while the snow piled up outside. It was a really cozy, nice feeling.
Other Thanksgivings growing up also tended to involve the playgroup, and/or our only relatives in the area; my Aunt Laura Jean and Uncle Craig in Seattle. Sometimes we'd go to Seattle, sometimes they would come down to Olympia. It was always an adventure to see the special friends and relatives who I didn't usually get to hang out with. The kids' table, always in a basement or a backroom, tended to get pretty rowdy at those reunions.
One of the coolest Thanksgiving traditions that was developed when I was a kid was the post-Thanksgiving, extended-overnight trip to the Winstead's beach cabin on Hood Canal. Nadia Winstead was close to my age, but since I was kind of immature and shy around girls, I usually hung out with Alex, who was a couple years younger than me. We went around like brothers, exploring the beach, the logging roads, and the Dosewallips River delta (picture), where pink salmon would run, seals would splash, elk would graze, and eagles would swoop. When I learned to scuba dive in highschool I would dive with my dad off the Winstead's beach and collect a bunch of dungenese and red rock crabs in a bag. The water was equally cold all year so it was no worse diving in November.
At college in Texas I never made it home for Thanksgiving. But when I was a freshman I saved my money from working the library desk to fly out and visit my long-distance infatuation in Charlottesville, Virginia. Needless to say it was a giddy, exciting time. I remember walking blissfully with so and so around the UVA campus and being impressed with a massive ginkgo tree, whose perfect, yellow leaves had carpeted acres of lawn.
The year after that was not my favorite Thanksgiving. I hung out with some people who I didn't know well at the dormitory advisor's house on campus. Oh, well. The weirdest Thanksgiving ever was the next year when I went to my roommate's friends' house in the suburbs of Houston. It was a giant McMansion with enormous pickup trucks and SUVs in the driveway and a pool in the backyard with a fake rock waterfall that had red lights in it so it looked like a volcano. The woman of the house had frozen, news-anchor hair and big, gold earings, and she wore a tight, zebra-striped shirt. The man of the house, who had made his fortune marketing life rafts for oil rigs, was recovering from a multiple mole-removal operation, and his bald head was covered in band-aids. We deep-fried two huge turkeys, even though there weren't enough people there to eat even one. The giant TV stayed on during dinner.
The furthest from home I ever was on Thanksgiving was senior year of college studying tropical biology in Costa Rica. We must not have made a big deal of the holiday there, because I don't remember at all what we did. We probably ate black beans and rice and fried bananas because that's pretty much all we ever ate for every meal.
In grad school I started a new Thanksgiving tradition of driving down to South Carolina to see my Grandmama and Aunt Mary Garland. (I feel bad that I didn't make it down this year, but I'll be seeing my SC loved ones for Christmas in a couple weeks.) One time I brought Russ with me, and my relatives loved him so much that I had to step-up my good-grandson charm to make sure they wouldn't trade me in for him. When my folks built their beach house in Edisto Island I started bringing my windsurfs down with me to enjoy some slightly-warmer-than-Virginia fall sailing. The first time I ever sailed a shortboard in the ocean was at Edisto in Thanksgiving 2003. Out away from shore I saw northern gannett flying.
And all that brings me back to here. I'm lucky to have had 28 Thanksgivings full of family, friends, and cool nature experiences. That's a lot to be thankful for.
Monday, November 19, 2007
Here's an example.
And here are yet more ridiculous covers (link).
Monday, November 12, 2007
Any type of nature research is welcome at WSN, but the meeting has a strong, de facto bias towards marine biology. Likewise, studies from all over the world are welcome, but most presenters come from California, Oregon, Washington, Alaska, or Hawaii. There were a few folks from the East Coast there, but Matt Whalen (pictured) and I were the only reprentatives from VIMS**.
Matt came to give a poster presentation (picture) and to check out grad schools, and I came to to give a talk and check out post-docs. So we were on, like, parallel missions. To convey the gist of what kind of science we were talking about, here are the titles and abstracts our presentations:
DIAGNOSING A DECLINING ECOSYSTEM: SURVIVAL OF THE LAST CHESAPEAKE BAY EELGRASS BEDS DEPENDS ON A TENUOUS BALANCE OF BIOTIC AND ABIOTIC FORCES. By James G. Douglass and J. Emmett Duffy. "Burgeoning nutrient and sediment inputs from development, in concert with diminution of filter-feeding oysters, have severely reduced water quality in Chesapeake Bay. Apparently in response, formerly extensive eelgrass (Zostera marina) beds have shrunken to low levels. The remnant beds may now be vulnerable to other negative influences, including climate change and food web alteration. We examine eight years of field monitoring data from a surviving eelgrass bed to determine if the dynamics of the community are consistent with hypothesized modes of top-down and bottom-up control. We show evidence of top-down control of invertebrate grazers by predators, which could link eelgrass health with fisheries activity. However, we also find that every part of the biological community in the eelgrass bed has close, direct links with seasonal and interannual changed in the abiotic environment, suggesting that climate change could have an even stronger influence on the ultimate persistence or extirpation of eelgrass in Chesapeake Bay."
MANGLED MUTALISM: INTERPRETING DIRECT CONSUMPTION OF EELGRASS BY MESOGRAZERS IN CHESAPEAKE BAY. By Matt A. Whalen, James G. Douglass, and J. Emmett Duffy. "Eelgrass (Zostera marina) provides structural habitat for taxa ranging from small fouling organisms to economically important crabs and fish. However, eelgrass beds in the Chesapeake Bay are declining, along with the important ecosystem services they provide. Mesograzers, small crustaceans that consume epiphytes, are believed to be critical to eelgrass health by preventing algal overgrowth. Despite the putative benefit of mesograzers to eelgrass, evidence from both field monitoring and mesocosm experiments suggests that, under some conditions, mesograzers harm eelgrass by grazing directly on shoots. We examine the effect of season and the abundance of particular mesograzer species on the degree of direct grazing on eelgrass, and evaluate the potential relationship between overgrazing and eelgrass dieback events."
Matt and I were helped by our friend Lindsey who used to work at VIMS and who is now a grad student at UC Santa Barbara. Lindsey selflessly shouldered the challenging role of coordinating our professional connections, as well as our local transportation and entertainment.
I have to say, marine biology may not be the most lucrative vocation, but darn if we scientists don't know how to have a good time. Three straight days of lectures and presentations sounds boring, but being surrounded by hundreds of sparkling, soulful people who really care about this blue planet made it wonderful. Also, there were some mind-altering substances involved; Sierra Nevada Pale Ale, Starbucks Coffee, and fast food from the In-N-Out Burger across the street. My pal Pablo Munguia somehow found time between the meetings to create a mini-documentary dramatizing his labmates' search for a west-coast starfish called Pisaster (below).
Oh... and as a bonus while I was in California I got to catch up with Joachim Pfieffer, a Virginia windsurfing buddy who just happened to be on an extended business trip in Santa Barbara. I love those small-world moments.
**Not counting VIMS alumnus and uncanny Will Farrell look-alike Dr. Kevin Hovel, now ensconced at San Diego State University. Who is who?
Saturday, November 3, 2007
Noel as a Nor'Easter-