Accurate forecasts of future regional temperature and rainfall patterns in many regions largely depend on characterizing anthropogenic trends in tropical Pacific climate. However, strong interannual to decadal-scale tropical Pacific climate variability, combined with sparse spatial and temporal coverage of instrumental climate datasets in this region, have obscured potential anthropogenic climate signals in the tropical Pacific. In this dissertation, I present sea-surface temperature (SST) and salinity proxy records that span over the 20th century using living corals from several islands in the central tropical Pacific. I reconstruct the SST proxy records via coral Sr/Ca, that are combined with coral oxygen isotopic (d18O) records to quantify changes in seawater d18O (hereafter d18Osw) as a proxy for salinity. Chapter 2 investigates the spatial and temporal character of SST and d18Osw-based salinity trends in the central tropical Pacific from 1972-1998, as revealed by corals from Palmyra (6ºN, 162ºW), Fanning (4ºN, 159ºW) and Christmas (2ºN, 157ºW) Islands. The late 20th century SST proxy records exhibit warming trends that are larger towards the equator, in line with a weakening of equatorial Pacific upwelling over this period. Freshening trends revealed by the salinity proxy records are larger at those sites most affected by the Inter-Tropical Convergence Zone (ITCZ), suggesting a strengthening and/or an equatorward shift of the ITCZ. Taken together, the late 20th century SST and salinity proxy records document warming and freshening trends that are consistent with a trend towards a weakened tropical Pacific zonal SST gradient under continued anthropogenic forcing. Chapter 3 characterizes the signatures of natural and anthropogenic variability in central tropical Pacific SST and d18Osw-based salinity over the course of 20th century using century-long coral proxy records from Palmyra. On interannual timescales, the SST proxy record from Palmyra tracks El Niño-Southern Oscillation (ENSO) variability. The salinity proxy record tracks eastern Pacific-centered ENSO events but is poorly correlated to central Pacific-centered ENSO events - the result of profound differences in precipitation and ocean advection that occur during the two types of ENSO. On decadal timescales, the coral SST proxy record is significantly correlated to the North Pacific Gyre Oscillation (NPGO), suggesting that strong dynamical links exist between the central tropical Pacific and the North Pacific. The salinity proxy record is significantly correlated to the Pacific Decadal Oscillation (PDO), but poorly correlated to the NPGO, suggesting that, as was the case with ENSO, these two modes of Pacific decadal climate variability have unique impacts on equatorial precipitation and ocean advection. However, the most striking feature of the salinity proxy record is a prominent late 20th century freshening trend that is likely related to anthropogenic climate change. Taken together, the coral data provide key constraints on tropical Pacific climate trends, and when used in combination with model simulations of 21st century climate, can be used to improve projections of regional climate in areas affected by tropical Pacific climate variability.

Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Mar. 11, 2010). Includes bibliographical references.

Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009. / Committee Chair: Weiss, Howard; Committee Member: Cvitanovic , Predrag; Committee Member: Goldman, Daniel; Committee Member: Schatz, Michael; Committee Member: Wiesenfeld, Kurt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Lophelia pertusa is a cosmopolitan cold-water coral, often found in aphotic waters (>200m). Aggregations of L. pertusa (reefs) provide important habitat to many invertebrate and fish species and act as biodiversity hotspots in the deep sea. The health and diversity of these reefs is of vital importance to deep-sea ecosystems, and the microbial consortia associated with L. pertusa form the most basic ecological level. Deciphering the diversity and function of these microbes provides insight into the roles they play in maintaining reef health. This dissertation takes microbiological techniques that are used in shallow-water coral microbial research and applies them to L. pertusa. A flaw in a primer set, which is commonly used in the molecular genetics method Polymerase Chain Reaction (PCR) to obtain data on coral-associated microbes, is discussed and an alternative approach is presented. In addition, two culture-based studies are employed to catalogue diversity and explore functional differences in strains of both bacteria and fungi. The cultured bacteria were tested for resistance against six antibiotics that affect a variety of cellular targets to elucidate strain level differences. The first cultured fungi ever described from L. pertusa were identified by molecular techniques and assayed using Biolog plates to test their metabolic capabilities. Preliminary data analysis on metagenomic libraries of the microbial-size fraction of L. pertusa is presented and discussed in the context of microbial diversity and function, bridging the gap between culture-based work on function and culture-independent work on diversity.

The variability of water-column absorption due to colored dissolved organic matter (CDOM) and phytoplankton in coral reef regions is the focus of this study. Hydrographic and CDOM absorption measurements made on the Bahamas Banks and in Exuma Sound during the spring of 1999 and 2000 showed that values of salinity and CDOM absorption at 440nm were higher on the banks (37.18 psu, 0.06 m^-1), compared to Exuma Sound (37.04 psu, 0.03 m^-1). Spatial patterns of CDOM absorption in Exuma Sound revealed that plumes of CDOM-rich water flow into Exuma Sound from the surrounding banks. To examine absorption variability in reef regions throughout the world, a thirteen-year time series of satellite-derived estimates of water-column absorption due to CDOM and phytoplankton were created from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) data. Time series data extracted adjacent to coral reef regions showed that variability in absorption depends on oceanographic conditions such as circulation patterns and winds as well as proximity to sources of light-absorbing materials that enter the water column, such as from terrestrial runoff. Waters near reef regions are generally clear, exhibiting a lower "baseline" level of CDOM absorption of approximately 0.01 m^-1 at 443nm. The main differences between regions lie in the periods during the year when increased levels of absorption are observed, which can be triggered by inputs of terrestrially-derived material, as in the Great Barrier Reef lagoon, or wind-driven upwelling as in the Andaman Sea and eastern Pacific Ocean near Panama. The lowest CDOM absorption levels found were approximately 0.003 m^-1 at 443nm near the islands of Palau and Yap, which are removed from sources of colored materials. The highest absorption levels near reefs were associated with wind-driven upwelling during the northeast monsoon on the Andaman coast of Thailand where values of CDOM absorption at 443nm reached 0.7 m^-1. Simulations of the underwater light field based on satellite-derived absorption values revealed that changes in absorption have a strong influence on light levels to which corals are exposed, particularly in the ultraviolet region of the spectrum, where CDOM is the primary absorber of light. Episodes of coral bleaching during 1998 and 2002 were found to be associated with elevated seawater temperatures as well as decreased levels of CDOM absorption, indicating that corals were exposed to light stress along with thermal stress during periods of bleaching.

Coral habitats span the range from tropical to polar, extremely shallow to thousands of meters deep. The differences in light and temperature experienced in these varied habitats likely affect the metabolic rates of the corals residing there. The metabolism of three coral species from different habitats have been examined to elucidate the effects of these environmental parameters on metabolism, an under-studied aspect of coral biology. For all three species, measurements of oxygen uptake, ammonium excretion, and activity of the enzymes lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and citrate synthase (CS) were used to characterize their metabolism. Off Florida's Gulf coast, Cladocora arbuscula is known to be one of the species least damaged by bleaching events and is one of the quickest to recover, making it an ideal candidate for studying the effects of symbionts. The first set of experiments was designed to reveal the effect of disrupting the coral-algal symbiosis between this subtropical shallow-water coral and its dinoflagellate symbiont, Symbiodinium. The metabolic effects were described for "normal" C. arbuscula and those "bleached" by being held in total darkness for 4 months. Normal C. arbuscula had a relatively low rate of oxygen consumption at 21°C, averaging 2.43±0.65 µmol O2 gwm-1 h-1 (±S.E.), using tissue wet mass, while the bleached colonies had an average rate of 2.46±0.49 µmol O2 gwm-1 h-1. Ammonium excretion averaged 0.07±0.02 and 0.10±0.03 µmol NH4+ gwm-1 h-1 (±S.E.) for normal and bleached C. arbuscula, respectively. The activity values of the metabolic enzymes citrate synthase (CS) fell within the normal range expected for a cnidarian, averaging around 0.09±0.02 activity units (U) gwm-1 for both treatments, indicating normal aerobic ability. MDH was extremely high for the normal corals, compared to other cnidarians, averaging 2.5±0.4 U gwm-1, and a bit lower for the bleached corals, averaging 1.2±0.3 U gwm-1, indicating high MDH activity during both normoxia and hypoxia. LDH activity, also high, averaged 1.3±0.2 U gwm-1 for both treatments, indicating anaerobic competence. These experiments show that C. arbuscula is adept at maintaining almost completely normal metabolic function when bleached, although the corals quickly become re-inoculated with symbionts upon return to normal light conditions in a tank with normal corals. The second set of experiments served to characterize the metabolism of Lophelia pertusa, an azooxanthellate cold-water coral that thrives in water depths between 36 and 3383 m. L. pertusa is rather stenothermal, commonly found between 6-8°C, but in the Gulf of Mexico can be subjected to warm water incursions. This makes it an ideal candidate for the examination of the effects of temperature. L. pertusa exhibited a respiration rate of 1.14 µmol O2 gwm-1 h-1 at the control temperature of 8°C. Calculating the Q10 for bringing L. pertusa up to the environmental temperature of C. arbuscula results in a value of 1.8. The 11°C treatment group exhibited an 11% increase in respiration, while at 13°C, the corals showed a 23% rise from normal. The 5°C group showed a 32% decrease in respiration. The activity values of the metabolic enzyme citrate synthase (CS) fell into the normal range expected for a cnidarian, averaging 0.15, 0.20, 0.10, and 0.18 activity units (U) gwm-1 for the 8°C, 11°C, 13°C, and 5°C treatments, respectively. Malate dehydrogenase (MDH) values were unexpectedly high, averaging 2.05, 1.48, 1.48, and 1.82U gwm-1 for the 8°C, 11°C, 13°C, and 5°C treatments, respectively. Lactate dehydrogenase (LDH) was undetectable in this species, suggesting it has a different terminal glycolytic enzyme. Nonetheless, the other two enzymes indicate metabolic competence in both normoxic and hypoxic conditions. L. pertusa is adaptable to temperatures within its range, although its respiration rate is lower than that of tropical corals. The third set of experiments characterized the metabolism of the endemic Antarctic coral Flabellum impensum, one of the world's largest solitary corals. It resides at roughly the same depths as L. pertusa, but the water temperature in its habitat never strays far from 0°C. F. impensum had a low rate of oxygen consumption at 0°C, averaging 0.31 µmol O2 g-1 h-1, calculated using tissue wet mass. Calculating a Q10 for this species at C. arbuscula's habitat temperature results in a value of 2.7. Ammonium excretion averaged 4.21 nmol NH4+ gwm-1 h-1. The activity values of the metabolic enzymes citrate synthase (CS), malate dehydrogenase (MDH), and lactate dehydrogenase (LDH) fell within the normal range expected for a cnidarian, averaging 0.13, 1.01, and 0.42 activity units (U) gwm-1, respectively. A count of the skeletal growth bands on the calyx suggests that this species has a linear extension rate of approximately 1 mm per year. F. impensum is a long-lived, slow-growing coral, with a low metabolic rate.

Acropora cervicornis was once one of the dominant reef building corals of the Caribbean, Florida Keys, and Dry Tortugas (DRTO), but since the 1970’s populations have been decimated throughout their geographic range. Recently, a repopulation was documented through detailed benthic surveys conducted by the U.S. Geological Survey at three locations (Pulaski Shoal, East Key, and Loggerhead Key) within DRTO. Benthic surveys using the U.S Geological Survey’s Along-Track Reef Imaging System (ATRIS) revealed hundreds of previously undocumented colonies. These discoveries have provided a unique data-set, allowing a comparison between the historical (1883, 1976) and contemporary distributions (2009, 2011) of A. cervicornis. Kernel density estimates were used to analyze shifts in high density areas and non-parametric multivariate analysis of variance tests were used to analyze differences between years in location and extent of the distribution. The results from the KDEs indicated high density areas have shifted among year’s at all three study areas. The comparison of the location and extent of the historical and modern A. cervicornis distributions revealed similarities and differences among years that varied among the study areas. This information is important to the management of this species because it provides vital information on the extent and location of the current distribution relative to historical levels. This study also provides documentation of the population dynamics and ecosystem changes over large time scales within the DRTO region. The above mentioned dataset was also used in a second study to quantify 1) variations in density among factors such as location (study area), suitable habitat type, and water depth, 2) overall spatial population patterns, and 3) spatial patterns in A. cervicornis density. Results indicated population structure was significantly clustered (P = 0.001) at Pulaski Shoal and Loggerhead Key with areas containing hotspots or significantly higher density (P < 0.05). Although significant hotspots existed, density did not significantly differ among suitable habitat types. Compared to all other factors, water depth had the largest effect on the variation in mean density of A. cervicornis. These findings are vital to understanding the recovery of this species in terms of current habitat and depth associations.

Understanding the factors influencing species ranges and dispersal are becoming increasingly important as climate change alters species distributions worldwide. If species are to persist, life-history strategies must rapidly evolve to accommodate shifting environments. This dissertation assesses the factors modulating dispersal in corals. First, I examined if there were any systematic differences in settlement between Indo-Pacific and Caribbean coral larvae that might explain Caribbean recruitment failures. No differences were observed, however I detected significant divergences in settlement cue preferences among coral species across both the Caribbean (Diploria strigosa, and Montastraea franksi) and the Indo-Pacific (Acropora tenuis, A. millepora, and Favia lizardensis), even for coral larvae from the same reef. Secondly, I established the extent of coral dispersal between remote reefs. I evaluated the genetic diversity and divergence across Micronesia for two coral species and investigated if these islands served as a connectivity corridor between the Indo-West-Pacific (Coral Triangle) and the Central Pacific. I found isolation-by-distance patterns whose strength depended on species, suggesting these corals are not panmictic across their ranges and that island stepping-stones facilitate gene flow to remote Pacific reefs. Next, I investigated genetic structure of symbionts in these same corals, to see if horizontally transmitted symbionts are less dispersive than their coral hosts. Symbiont genetic divergence between islands was an order of magnitude larger than host divergence and both host species and environment modulated symbiont composition. These results suggest that symbiont populations are host-specific and associating with local symbionts might be a mechanism for broadly dispersing corals to adapt locally. Lastly, I estimated heritable variation in dispersal-related traits in coral larvae. I observed strong heritable variation in gene expression, as well as parental effects on two phenotypic traits, settlement and fluorescence. I observed that patterns of differential expression in three-day-old larvae predicted variation in settlement and fluorescence two days later. Correlations between proteoglycan expression and settlement suggest that the larval extracellular matrix plays a role in settlement. Down-regulation of ribosomal proteins and differential expression of oxidative stress genes correlated with increasing fluorescence, possibly indicating reduced growth and increased stress. Overall, this dissertation contributes to our knowledge of factors affecting coral dispersal and the potential for evolution of dispersal-related traits. / text

The tropical Indo-Pacific is the location of highest global foraminiferal biodiversity. However, the shallow-water hydrothermal system in Tutum Bay at Ambitle Island, Papua New Guinea, possesses some of the world's highest naturally-occurring [As]. Foraminifers were collected in this intriguing system in 2003 and 2005 as part of a larger project to examine the possible effects of As and other hydrothermal factors on benthic communities. Despite the high ambient [As], a diverse foraminiferal fauna was observed. Foraminferal communities were examined from surface sediment and from material adhered to rubble at locations from 1-300m from venting and from reference sites, at depths from 1-28m. From this material, 159 species were identified representing 107 genera, 55 families, 30 superfamilies, and 10 orders. Species abundances exhibit a logarithmic series distribution, with two species comprising 40%, twelve species comprising two-thirds, and 20 species comprising 80% of all identified specimens. All other species individually contributed <1% to the total community. Foraminiferal abundance and diversity were analyzed across the hydrothermal field; both increase with decreasing hydrothermal influence: decreasing sediment and pore water [As] and temperature, and increasing pH and salinity. A thorough taxonomic reference of the region was compiled, consulting appropriate original descriptions, and is herein presented, and initial steps in creating an online database of all Recent foraminifers is described. Scanning electron micrographs of the most common taxa are provided. Laboratory experiments assessed the effects of [As³?] and [As5?] on growth of Amphistegina gibbosa. Exposure to As³? and As5? at concentrations of 0- 1000µg/kg showed that As³? is approximately 2.2 times more toxic than As5?, that [As³?] of 600- 1000µg/kg is sufficient to kill or severly impair specimens on approximately two-week timescales, and that [As5?] of 1000µg/kg or [As³?] of 200µg/kg are sufficient to retard the growth of A. gibbosa on approximately four-week timescales. Over timescales of several months, cultures with extremely low [As] (2µg/kg As5? and 0µg/kg As), showed growth rates not significantly greater than high-[As] treatments, possibly due to antimicrobial/parasiticidal properties of low [As]. Foraminifers displayed an exponentially-decaying functional relationship to [As], halving their rate of growth with every 300µg/kg increase in [As³?] or 600µg/kg increase in [As5?]. Measurements of foraminiferal whole-specimen [As] via SEM-EDX, AFS, and ICP-MS revealed high [As] of ~20mg/kg for specimens near hydrothermal venting declining to background values of ~2mg/kg for distal and non-hydrothermal reference species. Laboratory-exposed specimens contain [As] of ~6mg/kg indicating an As adsorption rate of ~0.25mg/kg/wk. The major portion of foraminiferal As likely occurs in a reduced-toxicity organoarsenical form, such as arsenobetaine.

Core samples were collected in September 1995 from live coral heads of Montastraea annularis at Bird Key reef in the Dry Tortugas, Florida (24 degrees 55 minutes N, 82 degrees 92 minutes W). Four 4 mm-thick coral slabs from two cores were continuously sampled at 12 samples per year (0.025 cm per sample for Core 31, 0.023 cm per sample for Core 35). Visual inspection of X-radiographs indicates an average skeletal extension rate of about 3 mm per year in Bird Key corals. The goal of this study was to perform a replication test in Montastraea annularis by using elemental and stable isotopes from four coral slabs from two different coral heads to address the following questions: 1) how well do geochemical signals replicate within a single coral head, 2) how well do geochemical signals replicate from two different cores from the same coral head, 3) how well do geochemical signals replicate from two coral heads from the same general area, and 4) do growth effects influence the geochemistry of slow-growing corals at the Dry Tortugas? Geochemical variations versus depth and time of all coral records show strong seasonal cyclicity. Variations in d18O in the suite of Bird Key coral records replicate the best; d13C and Sr/Ca variations replicate less well. For example, differences in the mean Sr/Ca record from two different coral heads are large (0.179 mmol/mol for BK31B-BK35CC; 0.196 mmol/mol for BK31C-BK35CC; ~4 degrees C) and nearly 4 times greater than analytical precision. Therefore, caution must be exercised in interpreting Sr/Ca-SST records in Montastraea annularis. Mean differences in coral d18O for all records, on the other hand, are within analytical precision and translate to temperature differences of less than 0.5 degrees C. Robust d18O values among cores that co-vary with a significant level of agreement further point to this proxy being more reliable than Sr/Ca. Because of its skeletal complexity, drilling difficulty, and large bio-geological error for Sr/Ca, Montastraea annularis seems poorly suited for coral-based Sr/Ca-SST studies. However, the species must be studied to understand tropical Atlantic interannual-decadal scale variability, so further assessment is warranted.