This week, green crab monitoring was in full swing. We sampled across five different sites throughout the South Slough, setting 12 crab traps at each site. Everything went pretty smoothly—except for getting stuck to the mud up to our thighs at one point. We had been warned about the mud here, but we were not quite ready for what that could actually entail. As I walked toward the small stream of water still remaining at low tide, my boots started sinking more and more into the mud until I was up to my thigh. Another intern came over to help, and then she got stuck too. We were eventually able to get our feet out of our boots and army-crawl out, and then had to dig our boots out as well. My entire lower body and arms were covered in thick, sulfurous mud. I wish I had pictures, but we were too covered in mud to touch our phones. It was all worth it, though; so far, we’ve caught green crabs at every site, for a total of about 40 crabs across all sites. In the other side of Coos Bay, they have been even more abundant this year. Another researcher caught over 100 green crabs within one day. As we continue to re-sample sites throughout the next few weeks, we will be able to more accurately compare their abundance to previous years and provide a more complete assessment of the population trend.

Because green crabs will be a majority of my time here and I will be writing about them frequently, I thought I would take a digression and also write about an eelgrass research project that I assisted on this week. Eelgrass (Zostera marina) is a seagrass that can form dense beds along bays and estuaries. These beds provide important habitat and nurseries for many shellfish and fish and provide feeding ground for birds and other wildlife. Eelgrass has been declining throughout the United States, with various natural and anthropogenic causes: nutrient runoff, invasive competitors, shellfish harvesting practices, rising temperatures and sea levels, and eelgrass wasting disease.

Researchers from Oregon State University are conducting a multi-year study on eelgrass decline along the Oregon coast, including sites in Coos Bay. We took a boat out to two sites with dense eelgrass beds. We then navigated to approximately 40 randomly selected GPS coordinates throughout the site. At each GPS point, we counted the number of eelgrass shoots within a .25x.25 m square (called a quadrat) and collected a single eelgrass shoot and all of the algae present within the quadrat. These samples of eelgrass and algae will be processed later for various measurements, including quantifying the biomass and the number of epizoa (animals living on the surface of the eelgrass). Even just spending a few hours in the eelgrass beds offers a glimpse of how much life they can support. We saw baby starfish smaller than a pinky nail clinging to eelgrass, countless shellfish and crabs, and birds such as gulls, cormorants, and even a few Great Blue Heron out on the eelgrass beds at low tide, searching for food. It was a beautiful place to spend some time doing research.

The eelgrass bed site (called Clam Island) that we sampled at low tide. At low tide, the eelgrass is matted down as the water recedes. But as the tide rises, the water will allow the eelgrass to lift up, and it will more resemble a forest of grass.

Another intern and I counting eelgrass shoots at one GPS coordinate at Clam Island. The white square is called a quadrat: at each GPS coordinate, the number of eelgrass shoots within the quadrat were counted and algae and eelgrass from within the quadrat were collected.

Me standing at the edge of Clam Island where the water is starting to come back in as the tide rises. (My eyes are open this time!).

More information about eelgrass:

http://www.habitat.noaa.gov/abouthabitat/eelgrass.html