Tropical Marine Ecology
This advanced course was last offered in the fall of 2011. The field component of Tropical Marine Biology in 2011 took place in Belize at South Water Caye during the second and third week of winter break. The course was co-taught by Chris Petersen and Helen Hess
Tropical Marine Ecology has always had student field ecology projects as a part of the course, although the types of projects vary in each reincarnation of the course. In 1998, the first year it was taught, the focus was on individual or paired student projects. In 2001, more time was spent on the class project on cleaning, that was an outgrowth of some of the individual student work in 1998. In 2005, because the projects were for any of three courses, some projects were more focused on marine ecology, while others emphasized marine policy or conservation. In 2011, the class broke up into 3-5 small group projects with two to four students per project, using South Water Caye in Belize as a base for fieldwork. We spent 10 days at the field station over winter break, after having class meetings fall term. Right now there are no scheduled plans for this class in the immediate future.
For an idea of some of the projects that have been done in the past in this class:
The 2005 class projects can be found at the Integrated Marine Studies in Tobago Website.
1998 and 2001 class projects – (Akumal, Mexico)
Several of the projects, mostly from 1998, are briefly summarized below along with the students of did the work. In 2001 independent projects varied widely, and in this class we decided that students would be limited to giving oral presentations of their work, so we do not have hardcopies of papers to post on the web. The projects were quite diverse, including cleaning behavior of small juvenile fish, both distribution and morphology of sea fans as well as another project on predation on sea fans, habitat use by bluehead wrasse, juvenile parrotfish behavior, goby territoriality, the behavior of grunts, and the impacts of tourism on coral reefs. The main class project was a
1998 Class project – Assessing reef fish diversity.
Coral abundance and diversity has been monitored at Akumal for several years, but no baseline data exists for other groups of organisms. As part of the 1988 tropical marine ecology class the students and instructors collected baseline data on fish diversity. We collected data in three different habitats, seagrass, reef rubble, and developed backreef enviornments. Belt transects (20 by 2 meters) were used to collect data on smaller sedentary species, while five-minute scans within a 5-meter radius of a stationary snorkeler was used to assess larger, more mobile species. These data are being shared with CEA (Centro Ecologico Akumal), a non-profit center of research and outreach in Akumal. Helen Hess and Chris Petersen, instructors.
The basic method of using strip transects to count fish on a reef was explored. Using permanent transects, this study investigated the effects of strip width, observer experience, and number of times a transect was swum to generate a count. The results of this study showed that it took na?ve observers several days of rather intensive work before they were able to successfully census a wide range of cryptic species, especially gobies and blennies, which might often be underrepresented in Rapid Ecological Assessments using groups for short, intensive time periods.
Cleaning fishes and their hosts were examined on patch reefs. Juvenile bluehead wrasses comprise a disproportionate fraction of the cleaners on the reefs examined (although the cleaner pictured below is a Spanish hogfish juvenile). For fishes that act as hosts (fishes that are cleaned), adult surgeonfishes only make up 1% of the fish population but they make up 61% of the fishes cleaned in the backreef of Akumal. Grunts are also found at cleaner stations much more often that you would expect given their abundance.
Cleaning and its relationship to injuries. Nicole Cabana
Fish are hypothesized to use cleaning stations as places not only to remove parasites, but to have wounds cleaned and to speed healing. In this study surgeonfish with wounds were found in higher numbers at cleaning stations than in the general population. Surgeonfish with wounds or body discolorations, as well as other species like this striped parrotfish, were found to go to cleaning stations at much higher rates than predicted based on their proportion in the population.
Juvenile fish densities were measured using transects in seven habitat types. Rocky rubble, and mangrove habitats had the highest juvenile densities, with the actual reef substantially lower, but the large area of rocky shoreline led this habitat to have the highest potential pool of recruits for local coral reefs.
Patterns of daily migration of grunts from their daytime hiding places on reefs to their nighttime foraging sites over turtle grass beds were examined. Routes were consistent from night to night, as was the timing of leaving the reef. Larger fish were the first to leave the reef in the evening. In the presence of a threat, a snorkeler blocking the preferred route, departure times shifted slightly later, and only the largest size class left the reef during the first of three time periods monitored.
Rates of aggression by territorial damselfishes toward naturally occurring fishes of other species were measured. The quality of algae in territories is known to increase during the day, and it was hypothesized that fishes would be more active defenders of their food and eat more food later in the day. Bite rates and chase rates both increased during the course of the day, being highest in the late afternoon.
Territory defense by damselfish. Ozlem Uz & Sarah Bevins
The introduction of a competitor into the territories of longfin damselfish evokes a response from the resident fish. This project compared the intensity of responses to four species of sea urchins by damselfish. For each urchin species, 10 replicate introductions into a different damselfish territiory were made. The two larger urchin species resulted in higher bite rates on the urchin, while the two smaller species were picked up by the fish and carried beyond the territory boundaries
The effects of patch reef area and reef depth on the number of resident fish species was explored on 16 patch reefs. Fish abundance increased with increasing reef size, up to an asymptote of 27 species on reefs larger than 90 square meters. Although overall species numbers did not change with depth, juveniles were a higher proportion of the fish population on shallower reefs.