|Edmunds, Peter J.||California State University Northridge (CSU-Northridge)||Principal Investigator|
|Brown, Darren J||California State University Northridge (CSU-Northridge)||Student|
|Copley, Nancy||Woods Hole Oceanographic Institution (WHOI BCO-DMO)||BCO-DMO Data Manager|
The study was conducted in St. John within the Virgin Islands National Park (VINP). The majority of our analyses focused on the shallow fringing reefs of Great Lameshur Bay and was completed in 2010 and 2011. Surveys in July and August 2010 focused on the natural history of the association by evaluating Millepora spp. for colony size and population density of C. tibicen. Surveys were repeated between June 2011 and August 2011 and expanded to the north and east shores of St. John to test the generality of the observations initially made in 2010. In 2011, manipulative experiments were conducted to test the functional basis of the Millepora-Calcinus association and evaluate whether it could be described as a commensalism.
These data were published in Brown D, Edmunds PJ. (2013)
Original submitted excel file in data file section.
Abundance of Calcinus tibicen on Millepora spp.: Surveys in 2010 were performed during the day at Tektite and Yawzi Point in Great Lameshur Bay. At each site, 25-m transects were placed parallel to the 2-6 m depth contour and Millepora spp. colonies within 1 m of either side of the transect were censused for size and abundance of C. tibicen. The benthos was also searched for C. tibicen to determine the extent to which they occurred on surfaces other than Millepora spp. Millepora spp. was scored for size and presence of C. tibicen. The sizes of C. tibicen were estimated indirectly through the sizes of the gastropod shells they occupy.
Nocturnal surveys: Surveys were completed at night in 2011 to test the possibility that C. tibicen leave Millepora spp. after dark. This portion of the study was motivated by the strong likelihood that C. tibicen is an omnivorous detritivore and, therefore, eventually would have to leave their Millepora spp. to forage. Presumably, this behavior might best be accomplished at night when they could escape visual fish predators.
Site fidelity: Hermit crabs were collected and grouped by the colony from which they were collected, and their Millepora spp. colonies marked so that tagged crabs could be returned to the same colony. Site fidelity was expressed as the percentage of tagged hermit crabs remaining on each colony over the census period. Results table.
Behavioral response: To evaluate the capacity for C. tibicen to find Millepora spp., two experiments were conducted. First, a displacement experiment was conducted in 2010 and 2011, in which C. tibicen were removed from Millepora spp. colonies during the day, placed on adjacent algal turf, and observed for 5 min to determine whether they returned to the same Millepora spp. Second, a laboratory experiment was conducted in 2011 in which C. tibicen were placed in a Y-maze and presented with a choice of Millepora spp. versus seawater.
Results of Y-Maze Choice:
Predator avoidance: To gain insight into the mechanistic basis of the Millepora- Calcinus association, a tethering experiment was conducted in which the losses of secured C. tibicen were determined on Millepora spp. versus sand/algal turf.
(Octet Stream, 240.00 KB)
Original excel file for dataset 523358, 523441, 523481, 523451. This file has been reworked and put into the BCO-DMO system for improved interoperability.
|distance_removed||the distance the crab was removed and placed in front of the Millepora colony||cm|
|crab_move_rank||response of the crab after removal: 1 = return to original Millepora colony 2 = crab stayed where it was placed 3 = crab moved away from original Millepora colony 4 = crab moved toward an adjacent Millepora colony||unitless|
Virgin Islands National Park
|Start Date|| |
|End Date|| |
Studies of corals and hermit crabs
Long Term Research in Environmental Biology (LTREB) in US Virgin Islands:
From the NSF award abstract:
In an era of growing human pressures on natural resources, there is a critical need to understand how major ecosystems will respond, the extent to which resource management can lessen the implications of these responses, and the likely state of these ecosystems in the future. Time-series analyses of community structure provide a vital tool in meeting these needs and promise a profound understanding of community change. This study focuses on coral reef ecosystems; an existing time-series analysis of the coral community structure on the reefs of St. John, US Virgin Islands, will be expanded to 27 years of continuous data in annual increments. Expansion of the core time-series data will be used to address five questions: (1) To what extent is the ecology at a small spatial scale (1-2 km) representative of regional scale events (10's of km)? (2) What are the effects of declining coral cover in modifying the genetic population structure of the coral host and its algal symbionts? (3) What are the roles of pre- versus post-settlement events in determining the population dynamics of small corals? (4) What role do physical forcing agents (other than temperature) play in driving the population dynamics of juvenile corals? and (5) How are populations of other, non-coral invertebrates responding to decadal-scale declines in coral cover? Ecological methods identical to those used over the last two decades will be supplemented by molecular genetic tools to understand the extent to which declining coral cover is affecting the genetic diversity of the corals remaining. An information management program will be implemented to create broad access by the scientific community to the entire data set.
The importance of this study lies in the extreme longevity of the data describing coral reefs in a unique ecological context, and the immense potential that these data possess for understanding both the patterns of comprehensive community change (i.e., involving corals, other invertebrates, and genetic diversity), and the processes driving them. Importantly, as this project is closely integrated with resource management within the VI National Park, as well as larger efforts to study coral reefs in the US through the NSF Moorea Coral Reef LTER, it has a strong potential to have scientific and management implications that extend further than the location of the study.
|NSF Division of Environmental Biology (NSF DEB)|
|NSF Division of Environmental Biology (NSF DEB)|