Sea Grant Final Report: Executive Summary Plus Narrative Project Title: Symbiont diversity and population dynamics of coral reef sea anemones Date: 22 November 2010 Project Number: R-101-1-08 Investigators and affiliations: PRINCIPAL INVESTIGATOR: Nanette E. Chadwick, Auburn University (AU) CO-PRINCIPAL INVESTIGATOR: Stephen G. Ratchford, University of the Virgin Islands (UVI) Dates Covered: February 1, 2008 to October 31, 2010 A. Executive Summary of Impacts and Contributions 1. Objectives: Objective 1: Determine the abundance and diversity of crustacean macrosymbionts and the population dynamics of corkscrew sea anemones Bartholomea annulata on Caribbean coral reefs. We completely met this objective, by conducting quarterly censes of mapped anemones at 2 coral reef sites on St. Thomas, USVI, over 2 years. These revealed that the anemone populations are stable among years, but experience rapid turnover of individuals, with most anemone mortality occurring within 1-2 years. Small individuals contribute the most to population growth, and the anemones rely on high rates of juvenile recruitment for maintenance of stable populations. These anemones support a high biodiversity of crustacean associates, including 1 facultative and 5 obligate species, which remain fairly stable in overall abundance among years in unfished populations. The crustacean assemblage on individual anemones varies widely among quarterly censes, indicating high shrimp mobility and population turnover. Objective 2: Train a graduate student at AU and undergraduate students at UVI in methods for interannual modeling of sea anemone population dynamics and determination of the diversity patterns of crustacean symbionts. We completely met this objective, by training 3 M.Sc. students and 1 Ph.D. student at AU, of which this Sea Grant research was the core of their thesis projects (2 graduate theses completed, 2 in progress). We also trained 4 undergraduate students in research projects at UVI. Objective 3: Educate youth in the Virgin Islands concerning the ecological importance of this and other symbioses on coral reefs, through the development of educational materials and a hands-on program. We completely met this objective, by developing an educational activity book on Coral Reef Symbiosis, printing 1,700 copies, distributing them to elementary schools and environmental organizations throughout St. Thoma, and posting an electronic copy on the internet for public use. We also conducted 2 hands-on programs for a total of 45 high school students and 7 teachers on coral reefs surrounding St. Thomas. Their responses on program evaluations indicated substantial improvement in their marine environmental awareness. 2. Advancement of the Field: This is the first in-depth description of population dynamics of a coral reef sea anemone, revealing that some reef anemones are short-lived. Their rapid population turnover is in sharp contrast to demographic patterns in reef-building corals, which have lifespans of decades to hundreds of years. These findings advance the field of demographic studies on coral reefs, by showing that anemones can be much more dynamic than their close relatives the stony corals, and as such, are expected to recover much more rapidly from disturbances. A reciprocal field transplant experiment between our 2 field sites indicated that these anemones are extremely plastic in the expression of life history traits, also a first for tropical anemones, and similar to the known strong effect of environment on the expression of traits in stony corals. The crustacean associates of these Caribbean anemones are as biodiverse as those associated with Indo-Pacific anemones, which is surprising given the relatively low biodiversity of most coral reef organisms in the Caribbean compared with the Indo-Pacific region. These results indicate that obligate symbiosis with sea anemones is an important driver of crustacean coevolution and biodiversity on Caribbean coral reefs. Because these anemones host obligate cleanershrimps that are major cleaners of parasites from reef fishes, they also can drive patterns of fish biodiversity on Caribbean reefs. The results of our field experiments, which go beyond the original
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