Dr. Sylvia Yamada, the expert on European green crabs on the west coast, was the guest speaker at OIMB’s Bioinvasions class on Sunday. Sebastian and I were able to sit in on her lecture and the trapping demonstration that followed. She'd set traps down at the boat basin, a location we had sampled just the week before. Interestingly, both samplings of green crabs (from Sylvia's demonstration and from our monthly monitoring) had these weird gelatinous growths along their claws and walking legs. Shon and Sylvia both mentioned not being sure what the growths were so we set the bumpy crabs aside in our sea-water tables until we could bring them over to Dr. Richard Emlet's lab later on in the week. Richard helped us ID the growths as a Bryozoan in the Alcyonidium genus. Looking at the jelly-like bumps under a microscope, we could see that the growths were actually entire colonies of an invertebrate species that was encasing the crab’s leg. Bryozoans are commonly referred to as moss animals and these gelatinous bumps lived up to the name. When we submerged one of the crab legs in water and watched again under the microscope, the smooth bumps took on a fuzzy, moss-like texture as their tubular bodies re-emerged and began filter feeding. By the end of our time in the lab with Richard, he had pointed out two different species of bryozoa as well as the species of barnacle that had grown on the crab’s carapace, all of them using the hard outer shell as a host site… It was beautiful. I think I’ve gotten the research bug here. When I arrived at OIMB I really wasn’t sure whether I wanted to go into natural resource management or focus more on research but the more time I spend collecting data out the field and working in the labs, the more excited and invested I become in the species I’m studying.
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Hello Low-low tides, your presence in the bay means we’re back in the field so I love you very much. Fieldwork is my favorite, it's a mix of appreciation, wonder, and constant problem-solving. Aside from maintaining the traps for green crab monitoring while out in the field, I try and sneak in some time to look under rocks, learn the names of new plants, get stuck in the mud and ask questions about tube worms, tidal patterns, the strength of tuna blood for scent dispersal in tidal waters, and so on. I've been working alongside Shon and Sebastian this week, doing our monthly monitoring of the invasive European green crabs (Carcinus maenas) at our regular ten survey sites. The traps we set out caught some native species including Oregon shore crabs (Hemi nudis), Dungeness crab (Metacarcinus magiste), and sculpin, but the majority of our catch was the green crab. Thursday’s catch had the largest (worst) numbers for green crab abundance this year with one of our sampling sites reaching a whopping 92 green crabs in just six nets… that's a lot. The good news is that most of the European green crabs (EGC) we are catching seem to be adults. This means it may be a low year for recruitment (the new population added via reproduction, immigration, or emigration). A low year of recruitment isn't necessarily a sign that the EGC population in Coos Bay is dying out since most of our largest recruitment events are tied to El Nino years, but it is a good sign for our local crab fisheries and eelgrass restoration projects for the moment. Speaking of Eelgrass... On Friday, I assisted in some eelgrass monitoring with Ali Helms and her REU intern, Chloe. There was a big die-off of eelgrass a few years back so restoration efforts have been underway to re-establish the lost beds throughout the bay. Eelgrass is finicky, the loss of rooted eelgrass plants in the sediment means that the feedback loop that results in good sediment for eelgrass seed germination is also gone, making restoration efforts tricky. Because eelgrass is a key habitat plant for juvenile Dungeness crabs, efforts continue, and from what I was able to see, transplanted eelgrass from healthier beds have been showing signs of success!
It’s been a good and busy week. I’ll be spending my Saturday vegging out so I'll be rested for Sunday’s Slough-a-thon! I’m the kayaking leg of a relay team with Shon and Sebastian (Team name: Lean Mean Green (Crab) Team)! Wish us luck! This past Monday was a holiday so I took the three-day weekend to drive up to Portland and spend some time with my partner and 2 cats whom I’ve missed very very much. It was lovely. A weekend full of cooking good food, sleeping in late, and enjoying the warmer weather. I was back at work Tuesday morning where I’ve since been workshopping my research project and preparing everything for the upcoming weeks of good low tides. After a couple brainstorming sessions with Shon (my REU mentor), I’ve refined my original goal. I'm no longer looking at the relationship between European green crab (EGC) abundance and associated habitat (i.e. salinity, water depth, and percent distribution of protective cover, rooted vegetation, and open mudflats across the survey sites). Instead I'll be focusing on distribution trends of the European green crab (EGC) within a single habitat factor (tidal zone depths). In the previous green crab samplings along the 0-foot tide waterline, we’ve noticed higher rates of adult male crabs captured in the traps than any other age group or sex. Some possible factors influencing this could be that females are deterred from entering the Fukui traps after seeing trapped males, or that recruits (first year age group) are too small to be successfully sampled using the Fukui traps. Another factor, and one I’ll be looking into, is whether recruit and female EGC are captured less in our 0-foot lowtide sampling because they inhabit different depths of the intertidal zone than their adult male counterparts. In order to determine if there are significant distibution trends in age and sex of the European green crab along tidal zone depths, I’ll be surveying three distinct tidal regions (subtidal, 0-foot tide, and high intertidal) across 9 sites in Coos Bay. Overall, it was a computer-heavy week with a lot of time spent scouring ArcMap and Google Earth for potential survey sites, planning out sampling methods, reading up on previous studies, etc. All of this screen time made our weekend boat trip with Richard and Newt (OIMB boat Captain) a welcomed brain break. The trip started eventfully with a near collision but once we made it out into the open ocean, it was blissfully calm waters and abosultely gorgeous. The trip was set up to give us experience using a trawling net to collect marine life samples from the sea floor. Trawling is when you drag a hard-mouthed net along the rocky ocean bottom for about 10 to 15 minutes then pull up the net and see what your catch is. It's a pretty destructive method of sampling, ripping up a lot of habitat in order to catch species that tend to stick to the ocean floor like corals, sea stars, nudibranchs (sea slugs), and whelks (predatory sea snails). The ethics of trawling for the experience of trawling seems questionable, but the species we were able to observe were pretty mind-blowing. It was a mixed bag of feelings and I was happy to learn that some of the species we brought back were scooped up by the Charleston Marine Life Center (local educational aquarium) for display. All in all, it was a really good week and I'm excited to get started on my own fieldwork now that I've worked out most of the bugs in my research methodology. The days are flying by, I can't believe it's been a week since we were all camping out at Cape Arago. We spent two nights at the cape with Nicole (Ph.D. student and REU guardian angel) and her partner, Tommy, who kept us well fed all weekend while we hiked around and hung out at the beach. The Oregon coast is an absolute wonder and between seeing a gray whale feeding along the kelp beds offshore and getting to eat copious amounts of s’mores by the fire each night, I was fully blissed out. Since then, Shon, Sebastian, and I have finished our tea-bag decomposition work by kayaking up into South Slough Estuary to access two remote salt marsh sites. At each of these decomposition study sites we surveyed plant species and buried triplicate tea-bag samples into the wet soils. Shon will return in the fall to dig the tea back up, dry, and re-weigh it. Any loss of mass from its original weight is a sign of decomposition and used to monitor carbon sequestration and nutrient cycling within the marsh. We mapped out our kayak route on Google Earth the following day - I’m very proud to say I made it the whole five mile trek up the waterways despite some gnarly head winds. On Wednesday we drove up the coast to setup new green crab sampling sites in the estuaries of both the Umpqua and Siuslaw rivers. These northern sampling sites will be maintained by two local volunteers that I had the pleasure of working/chatting with (One of whom was a retired entomologist/ecologist and the other a retired natural resource manager). I am happy to report that there were no green crabs collected in the traps at the Umpqua site. Siuslaw's traps brought in the BIGGEST green crab we’ve recorded yet. An absolute beaut and brute weighing in at 263.1g. Aside from all of the field excursions, I’ve been working out the details for my personal project. I plan to integrate habitat surveys into each of the 35 anticipated green crab sampling sites this summer. These surveys will be used to determine if abundance of the European green crab, Carcinus maenas, in Coos Bay can be predicted by habitat. And if so, what types of habitat provide the greatest risk of high abundance rates of the invasive species. If I can determine what habitat/s are most associated with high abundance of green crab, we can focus our mitigation efforts to high risk areas as a means of slowing their establishment within the bay. This in hand with Sebastian’s biotoxin testing would also be helpful information to share for recreational crabbing in the area. |
AuthorHello! My name is Colleen Walker. I'm a New Yorker now living in Oregon where I am pursuing an AS in Biology at Clackamas Community College. This summer I'll be studying the European green crab alongside Dr. Shon Schooler at the South Slough National Estuary Research Reserve. Archives
August 2022
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