No description available.

Increased pressure from natural and anthropogenic disturbances on coral reef ecosystems elevates the importance of an ecological assessment prior to further degradation. Diego Garcia, in the Chagos Archipelago, poses an interesting study site as its reefs, while existing in an environment that is increasingly degraded and threatened, are considered the most diverse in the Indian Ocean. With the utilization of both digital photograph transect assessment of benthic habitat composition and the development of a bathymetric digital elevation model (DEM), the reef conditions at the study site were surveyed in order to describe the coarse features of community structure. The coral community structure in northern Diego Garcia is largely driven by the fecundity of the dominant coral species present in the system as a wide variability in the coral reef ecosystem environment encourages a wide variability in coral cover. Acropora spp. at the sites in northern Diego Garcia gained their competitive advantage over the other genera with successive successful reproductive and recruitment events through initial investment in growth to a highly fecund and more stable size. Additional fieldwork may further sharpen predictions on acroporid dominance for the area but through this study, a greater comprehension of the physical environment as well as the major control on the nature of the northern Diego Garcia reef development has been recognized.

The Strait of Florida is a crescent – shaped channel, 180 km long that separates Florida from the Bahama Platform and Cuba and connects the Gulf of Mexico with the Atlantic Ocean. The Strait was investigated by four major dredging and trawling efforts: the U.S. Coast and Geodetic Survey Steamer Blake in the 1870s; the U.S. Fish Commission Steamer Albatross in the 1880’s; the Woods Hole Oceanographic Institute’s R/V Atlantis in 1938 and 1939, and the University of Miami’s R/V Gerda and Pillsbury from 1962 to 1971. This study uses multivariate statistics to analyze qualitative published and museum records of dredged and trawled material to determine patterns of benthic fish and invertebrate distributions in the Strait of Florida and to recognize possible assemblages and associations among these organisms. Distributional information was correlated with mean bottom hydrodynamic and physicochemical data (water velocity, salinity and temperature) and depth to develop hypotheses about environmental controls of distributional patterns. Results reveal definite zonation patterns among selected invertebrate species in the Strait of Florida.

This thesis describes an investigation of the possibilities of using non-biogenic caloric sources in animal diets. The synthetic materials are intended to temporarily extend normal food supplies for domestic animals and humans in the event of an agricultural disruption, such as a poor harvest occasioned by unfavorable weather. A number of non-biogenic sources were considered on the basis of their industrial availability and existence in known biochemical pathways of' mammalian intermediary metabolism. Acetic and propionic acid esters and salts were chosen for the study. Survival rates and weight gain of mice receiving normal and starvation diets were used to indicate the metabolic utilization of acetylated and propionylated oats. Uptake of carbon 14 was used as an index of utilization of 14C labeled acetate. Acetate supplemented minima1 diets slightly prolonged survival. The average weight changes for the control and experimental animals, in both minimal and experimental diets, were not substantially different. The 14C tracer experiments revealed that a significant amount of exogenous acetate is oxidized, with a large portion also entering substrate pools.

A comprehensive physical and dynamical picture of the Pacific Equatorial Countercurrent is presented. This is the first known attempt; to analyze an ocean current system on the basis of the totality of hydrographic and wind stress data available. The Equatorial Countercurrent transport is a maximum at its beginning near the western boundary and decreases nearly linearly to end with zero at the eastern boundary. Zonal geostrophic flow is substantiated. The source of the Fquatorial Countercurrent is the westward flow of the North Equatorial Current and South Equatorial Current. Sverdrup's theory of wind-driven ocean circulation is not valid for the Pacific Equatorial Countercurrent, as shown by use of recent wind-stress tables and by evaluation of the steady state equations of motion. Nonlinear acceleration terms need to be included for a solution of this system of flow.

Chapter 1 The brittle star Ophiothrix suensonii is a coral reef invertebrate with high dispersal potential (up to 49 days larval duration in culture). Here I utilize COI sequence data from 264 individuals collected from 10 locations throughout the Florida reef tract and Caribbean to investigate dispersal dynamics and demographic history. Locations separated by up to 1,700km lacked genetic differentiation, confirming ability for long-range dispersal. However, significant differentiation was detected among other regions. Honduras showed the greatest subdivision, suggesting that this region may need independent management, and the circulation of the Mesoamerican gyre within the Gulf of Honduras could be a significant factor responsible for this subdivision. Demographic analyses provide strong evidence for an expansion of population size and range, possibly out of Florida, through the Caribbean, and into Honduras, which commenced in the mid-Pleistocene. However, the presence of a clade of rare haplotypes (likely a cryptic species), which split much earlier (late Pliocene), indicates that O. suensonii persisted long before its recent expansion, suggesting a cyclic history of population contraction and expansion. Finally, patterns of gene flow are not concordant with contemporary surface currents; rather, they reflect historical movements possibly linked with changes in circulation during periods of Pleistocene climate change. Chapter 2 Although over half of all known elasmobranchs are batoids, with many species exploited and several of conservation concern, little is known of their population genetic structure and microevolutionary history. Here I utilized sequence variation in 648bp of the mitochondrial control region to study the phylogeography and microevolution of the southern stingray (Dasyatis americana) throughout the Carolinas, Florida, and the Caribbean. Out of 267 individuals sampled from eight locations, 67 haplotypes were identified with AMOVA results revealing high overall population structure (ST = 0.59; P = 0.0000). However, phylogenetic and statistical parsimony analyses described three lineages that were sufficiently divergent to suggest cryptic speciation. The geographic distribution of haplotypes from these lineages described a complex phylogeographic pattern, which despite some degree of geographic partitioning among the following regions: (i) USA and Belize, (ii) Bahamas and the West Indies, and (iii) Grand Cayman Island, showed many haplotypes from divergent lineages to be sympatric at the same sampling site. The Grand Cayman population showed high genetic partitioning and despite evidence for recent migration, this population should be a conservation concern as the immigrants possessed highly divergent haplotypes and could therefore be reproductively incompatible with individuals of the resident population. Chapter 3 Sponges are one of the dominant fauna on Florida and Caribbean reefs, with species diversity often exceeding that of scleractinian corals. Despite their importance as structural components and habitat providers on reefs, their dispersal dynamics are little understood. I utilized ten microsatellite markers to study the population structure and dispersal patterns of the giant barrel sponge (Xestospongia muta), a widespread species throughout Florida and the Caribbean. F-statistics, exact tests of population differentiation, and Bayesian multilocus genotype analyses revealed high levels of overall genetic partitioning (FST = 0.12, P = 0.001) and grouped 375 individuals from the Bahamas, Honduras, US Virgin Islands, Key Largo, and the remainder of the Florida reef tract into five genetic clusters (K = 5). Assignment tests showed dispersal over ecological time scales to be limited to relatively short distances, as the only migration among populations detected was within the Florida reef tract. Consequently, populations are largely self-recruiting representing distinct management units. A combination of levels of genetic differentiation, genetic distance, and assignment tests support the important role of the Caribbean and Florida currents in shaping patterns of contemporary and historical gene flow. Chapter 4 The spotted eagle ray (Aetobatus narinari), a large coral-reef associated batoid of conservation concern, is currently described as a single, circumglobally distributed species. However, geographic differences in its morphology and parasite diversity have raised unconfirmed suspicions that A. narinari may constitute a species complex. I used 1570bp of mitochondrial and nuclear sequence data (cytochrome b, COI, and ITS2) to assess the validity of A. narinari as a single cosmopolitan species and infer its evolutionary history. Specimens from four major geographic regions were examined: the Central Western Atlantic, Eastern Pacific, Western Pacific and Central Pacific. Phylogenies described three distinct, reciprocally monophyletic lineages with no genetic exchange among regions. Based on combined genealogical concordance and genetic distance criteria, I recommend that the Western/Central Pacific lineage be recognized as a distinct species from lineages in the Central Western Atlantic and Eastern Pacific. The latter two lineages, separated by the Isthmus of Panama, are proposed as subspecies. Dramatically higher nucleotide diversity and sequence divergence coupled with a basal position in multiple phylogenetic analyses support an Indo-West Pacific origin for the A. narinari species complex, with subsequent westerly dispersal around the southern tip of Africa into the Atlantic and then into the Eastern Pacific. Chapter 5 Numerous marine species with seemingly wide geographic ranges have been delineated using molecular and biochemical techniques into cryptic complexes whose component species are distributed over far smaller areas. Accordingly, if cryptic species are a common feature of coral reefs, conservation measures will need to encompass all regions of endemism. I analyzed 414bp of the mitochondrial COI gene from two brooding amphipod species (Leucothoe ashleyae and Leucothoe kensleyi) commensal inside the branching vase sponge Callyspongia vaginalis, sampled throughout Florida and the Caribbean. The level of intraspecific divergence was among the highest reported for any marine crustacean (12.4 – 26.0% uncorrected) and exceeds that of congeners from nine diverse amphipod families. Our findings reveal multiple cryptic species endemic to Caribbean islands that suffer from depressed levels of genetic diversity when compared to mainland Florida. Molecular clock calibration suggests that morphology has remained in stasis for at least 9 million years, and it is proposed that stabilizing selection within a homogeneous sponge environment is responsible. Although lineages have been reproductively isolated since the late Miocene, secondary contact has occurred with cryptic species co-occurring within the same host, compounding the levels of species diversity missed under the morphospecies concept.

The effect of demersal reef fish on the gorgonians Pterogorgia anceps and Plexaurella grisea was determined under controlled conditions. Demersal reef fish cause significant changes in Pterogorgia anceps zooxanthellae concentration (cells cm-3), bulk density (g cm-3), and spicule concentration (g cm-3). Growth rates as measured by changes in planar area (cm2) are not significantly affected. No significant differences were found among any of the parameters measured for Plexaurella grisea; however, trends in the data were similar to those of P. anceps.

The purpose of this study was to determine the distributions and abundances of microzooplankton across a front in the Irish Sea, and to test the hypothesis that the structure which develops within the microzooplankton community is the result of the interactions within the communities. Eight sites were sampled on May 1-2, 1989 along a transect from Liverpool Bay, England to Dundalk Bay, Ireland. The transect crossed both the Liverpool Bay and western Irish Sea fronts; sites were positioned with respect to water type (e.g., coastal, thermally mixed, thermally stratified) . Five sites were sampled by double Longhurst-Hardy Plankton Recorder (LHPR) to determine micro- and macrozooplankton distributions and to identify relationships between these distributions and hydrodynamic and biotic forcing. Microzooplankton samples were microscopically enumerated, and the abundance data processed by Correspondence Analysis to determine interrelationships among the taxa. Variability in depth-averaged microzooplankton distributions along the transect can be explained largely by the hydrodynamic processes associated with the thermal and density structure of the region. The microzooplankton in the coastal and central channel waters were distinct; the Liverpool Bay and western Irish Sea front apparently act as boundaries between microzooplankton assemblages. The vertical distributions of the microzooplankton at each site appear to be affected by biological interactions between taxa (e.g ., predation). Correspondence Analysis also identified a sub-surface microzooplankton assemblage off the north coast of Anglesey not associated with strong temperature or density gradients, but which was taxonomically distinct from microzooplankton assemblages at the other locations. A similarity between the microzooplankton assemblages in the surface stratified waters of the western Irish Sea front and the Irish coast (48 km west) was also detected. This suggests the possibility that microzooplankton along the Irish coast have been advected offshore in the coastal waters.

Pacific white shrimp, Penaeus vannamei, was paired with blue tilapia, Sarotherodon aureus in three 42-day growth trials conducted in outdoor tanks, from May 23 to October 11, 1993. Each tank had a surface area of 5m2 and water depth of 80 cm. Two tanks contained 100 shrimp (20/m2) in monoculture and 2 tanks contained 100 shrimp in polyculture with 3 tilapia (0.6/m2). All tanks were given the same amount of feed. Water quality was monitored throughout and no significant difference was found between the two treatments. The tilapia did not significantly reduce the production of marine shrimp when the shrimp were stocked at a mean weight of 9.27 g (S.D. = 2.47). Although some decrease in shrimp growth was noted, the tilapia production made up this difference at no extra cost. Extrapolation of production results to one hectare showed production of 3,132 kglha of shrimp in monoculture, compared with 2,812 kglha of shrimp plus 473 kglha of tilapia in polyculture, for a combined total of 3,285 kg/ha. It was also determined that tank culture of marine shrimp and tilapia, whether in monoculture or polyculture, may be practiced with good results in the emerging field of "backyard aquaculture."

Chaetoceros muelleri, Isochrysis sp. and Nannochloropsis salina are commonly used to raise larval Pacific white shrimp, Litopenaeus vannamei. With the demand for shrimp increasing each year, it becomes more important to find more ways of raising shrimp on farms and thus lowering the pressure on wild stocks. The traditional larval feeding regimes consist of algal and animal food sources. The accepted animal food source is Artemia nauplii. Unfortunately, the use of Artemia is costly and increases the amount of bacterial pathogens found in shrimp. In addition, because Artemia cysts often become unavailable, it may become necessary to rely solely on algae cultures for shrimp larvae survival. Therefore, as the cost of Artemia increases and the availability decreases, it is important to explore new and more effective measures to raise popular mariculture species without the use of Artemia. In this research, Litopenaeus vannamei larvae were grown entirely on single or multiple species of phytoplankton without the use of an animal food source. Surprisingly, the industry's accepted Isochrysis sp. (single culture) was not as productive as Chaetoceros muelleri (single culture). Mixed cultures of Chaetoceros muelleri and Isochrysis sp. produced the highest percentage of shrimp larvae surviving and entering the post-larval stages. Although the survival rates of larvae grown to postlarvae was lower and the total growout period for larvae grown to postlarval was increased to sixteen days when the Artemia was removed from the larvae's diet, there were several advantages. First, it is not necessary to add antibiotics in order to assure high production rates by suppressing Artemia-introduced pathogenic bacteria. Secondly, it eliminates the competition between the Artemia and shrimp nauplii for available phytoplankton. Thirdly, by eliminating the need for Artemia cysts to enter an aquaculture farm, it allows for zero-exchange farms to exist by having all feeds for nauplii to be grown on-site. Lastly, it reduces the pressure to farm large amounts of Artemia if the industry accepts protocols that do not require Artemia cysts.