Welcome back! It seems like each week is so long and full of things to do, but when I sit down to write my blog posts, time has just flown by. Last Saturday we got to visit the Hatfield Marine Science Center and the Newport aquarium. The aquarium was fantastic, and we saw octopus, seal, sea lion, and sea otter feedings. On Sunday a big group of interns and students spent a relaxing day in the dunes at Hall Lake. Somehow it was already Monday once again, and time to go back to work. I visited a couple new sites to trap at, Kentuck Slough and Day Creek. When collection time came on Tuesday, I got to take a group of high school students in the South Slough camp with me. They were a big help counting crabs, and I hope they learned a little something too! With new crabs, I continued to switch out trials for my personal research experiment, which means I have now been able to complete around 40 trials. I am still not quite satisfied, because a low percentage of trials end in a successful predation event. I am planning to try a new method when I switch out trials for next week to see if feeding the red rock crabs will actually promote predation. Currently I have been bringing them in and starving them before beginning a trial, under the presumption that the hungrier they are, the more likely to seek food. But I have observed that some crabs appear to be less aggressive, and therefore may be weak with hunger and unable to predate on the available prey in the containers. It is taking a little longer to collect all the data I need, but that's the usual way with research! At the end of the week, Silvia Yamada came to visit OIMB. Yamada has documented the green crab invasion of Oregon and Washington and was one of the first to begin monitoring the populations, starting the same dataset in 1998 which I am contributing to with my collections this summer. Yamada has written or collaborated on most of the papers I have read about green crabs, and so it was a pretty cool experience to meet her and go in the field with her. She is starting a new experiment with lined shore crabs and snails, which I was able to help set up and will collect data from when Yamada leaves.
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Although the picture below isn’t great quality, it’s great news for my experiment! In the center of the container are the remains of a Dungeness crab, killed and eaten by the red rock in the bottom of the picture. This represents a successful trial! This week I am hoping to set up a camera to catch the act of predation. Because in previous literature, experiments with crabs of the same size class have not yielded predation, I am currently using the assumption that the red rock is initiating and successfully carrying out the predation. From personal observation I think this is reasonable. I have watched the containers for a fair amount over the past two weeks and have only seen red rocks initiating fights with either the green crab or the Dungeness crab. I would like to get it on video though to confirm, and I am also curious if there is any possibility in the small crab that is not under attack joining the red rock in the battle or at least sharing in the food source. Most of the crab behavior appears to be nocturnal, as there is not much activity during the day, and I usually visit the containers in the morning and find evidence of predation. As we finish up week 5 and are more than halfway through the program, I am starting to realize more and more that I don’t want this internship to come to an end. In terms of research experience, I have learned so much about field work and experimental design. But in terms of friendship, I have gained so much more than I ever thought. Evenings and weekends have been well spent with the other interns and UO students exploring around the charleston and Coos Bay area. Below are some pictures from various adventures!
This week I have continued working on my predation experiment. I have been trapping most days, and although I am getting high numbers of both Dungeness and green crabs (which is why I chose these sites in particular), it is difficult to find crabs that fit into my small size class. I will be trapping at a variety of sites next week, and am predicting that sites further up the estuary will have smaller crabs because these locations may provide more nursery grounds for small adult crabs. Most red rock crabs that I catch are in the appropriate large size class. I have also been able to catch more red rocks the same way most people fish recreationally: by throwing crab rings off of the dock! This targets red rock crabs, who tend to prefer sub-tidal areas, while the Dungeness and green crabs usually follow the tide in. The main reason I need smaller Dungeness and green crabs is because a lot of my trials have no outcome. Many of my trials have gone on for 7 days and no predation has occurred. Either the red rock is not hungry, or it may be reluctant to attack a crab that is smaller but still decent sized, especially in the presence of another crab that could also pose a threat during a predation attempt.
Green crabs can easily be identified by the 5 points along the top of their carapace on either side of their eyes. By looking at the distinct carapace, one can avoid confusion with color, because green crabs aren't always green! The crab below is also a green crab, although she appears to be more yellow/orange. The coloration could be a result of location and camouflage attempts, or more likely means that the crab is almost ready to molt as the shells often begins a light green and will then darken to yellow, orange, and then red. The crab on the left is a right-handed male, while the crab on the right is a female who is missing the first three chela or legs on her right side. I can tell the sex of each crab based on “apron” at the base of the abdomen. Males have a much narrower and pointed apron, while females have a wider, rounded apron.
My South Slough REU partner Sofia Suesue and I started off our week by participating in South Slough’s annual “Slough-a-thon.” Anyone affiliated with South Slough could participate in a bike/run/paddle event. Sofia and I did the running portion, and got to run a 5k through the beautiful trails of South Slough reserve! Last week, I had a really fun time helping Sofia with her research project, which involves mapping an endangered plant species known as Chloropyron maritimus ssp. palustre, or Bird's Beak. This plant grows in salt marsh areas found on the banks of the estuary. We went to a site called Distant Water fleet on Friday, and were pleasantly surprised at how abundant the plant was at this location. Sofia is mapping areas of the plant and noting soil type, salinity, and other plants found with Bird's Beak, all factors that might dictate where the plant grows and how limited its distribution is. But the most exciting part of my week has been making progress on my personal research project! I have decided to look at interspecies predation between the three common crab species found in South Slough. One of the main limiting factors of green crab distribution on the Oregon Coast is proposed to be competition and direct predation from the established native populations of crabs that tend to grow much bigger than Carcinus maenas. Right now, green crabs are mainly found in the middle and upper Coos Bay estuary. But the lower estuary is thought to be a more favorable habitat for crabs, due to higher salinity and lower water temperatures. The native red rock crab, Cancer productus, is only found in the lower estuary, as this species is less tolerant of physical factors than the green crab and thus requires the more favorable habitat. Right now, it appears that C. productus is able to dominate the lower estuary and limit green crab distribution, because the abundance of C. productus, is negatively correlated with abundance of C. maenas in the lower Coos Bay estuary (unpublished data). Basically, in the lower estuary where there are more red rock crabs, there are less green crabs. A study has found that C. productus is much more likely to conduct direct predation on small and medium sized green crabs than on small and medium sized crabs of their own species (Hunt & Yamada, 2002). This reinforces the fact that the inverse population distributions is caused by predation from C. productus on C. maenas in the lower estuary. After learning about this, I started to wonder if the green crab will ever be able to spread to the lower estuary. I have decided to conduct a continuation of the previously mentioned study, to see if C. productus still prefers direct predation of small C. maenas when another native species, the Dungeness crab (Metacarcinus magister) is also present, or if the Dungeness provide equally favorable or more favorable prey. Depending on the preference of C. productus, this could allow a possible opportunity for the population of C. maenas to continue to increase and become established at sites where the three species overlap, if C. productus is more likely to predate on available M. magister instead of the green crab. I have been collecting crab species all week and have been able to set up my initial trials of the predation experiment.
Welcome back! As an intern with the South Slough National Estuarine Research Reserve (SSNER), I have a slightly different experience than many of my fellow interns working in OIMB labs. A lot of my time is spent working in the field (which I'm always excited about) and helping with various projects that inform researchers about changes in the reserve and possible management options. I have enjoyed learning about the different aspects involved in a research reserve, and the behind the scenes for planning, management, coordination, and outreach. One of my favorite things is that South Slough has so many different projects focused on a wide variety of things that are important to the estuary. There are projects studying invasive species, like the green crab monitoring project that I will be contributing to, and there are other projects studying endangered species, species richness and abundance, monitoring various conditions in the estuary, and more. Many teams of researchers and interns go out each day. Last week I got to visit a site that is experimenting for effective restoration of the endangered species of Western Lily. This week, I assisted with a project filtering water to collect environmental DNA that can then be used to assess the species richness of fish found in the estuary. It has been nice to be out on the water so much; the Slough and its surroundings are stunning. I also look forward to seeing the sand bar with sunbathing harbor seals! Every project is also very relevant to the estuary and possibly even to other reserves around the country. I like knowing that the projects I'm helping with will discover new information that can have very real-impacts. As we were discussing in a professional development session this week, it is sometimes said that science answers questions, it doesn't solve problems. I think that the reserve does a great job of applying the science to do both. In addition to gaining experience and being able to help with ongoing projects, I have also started developing my own research project. Although I like being out in the field, I thought it may be difficult to develop a controlled experiment that I could monitor closely in such a short amount of time. Instead, I have opted instead to conduct an experiment in the lab. I have been reading a lot of literature on green crabs and have started to formulate questions based on areas where recent experiments could be extended. Stay tuned for next week’s post when I will hopefully have the first trials up and running and will explain what I’m studying!
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AuthorHi! My name is Renee and I am a rising junior at Muhlenberg College in Pennsylvania. I am a double major, studying Biology and Dance. I am so excited to be a part of the Oregon Institute of Marine Biology’s summer REU program and to work with Shon Schooler and the South Slough National Estuarine Research Reserve. Archives
August 2019
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