We have coupled a 3-dimensional physical planetary geostrophic ocean general circulation model to different biological models to investigate the interaction between physical and biological processes. A 1-dimensional particle cycle model with two particle size classes has been developed and coupled to the physical model as well. / The ocean model (Zhang et al., 1992) is based on the planetary geostrophic equations in spherical coordinates. The model equations include the full prognostic temperature and salinity equations. The momentum equations are diagnostic and include geostrophic balance, and a linear friction term in order to provide a western boundary current. The wind stress is applied at the top level of the model. The temperature and salinity distributions used in the surface boundary restoring condition are taken from climatological data. The model domain consists of a flat-bottomed box of 60$ sp circ$ longitude extending between 5$ sp circ$N and 65$ sp circ$N. The horizontal resolution is 2.3$ sp circ$ in both latitude and longitude with 14 levels in the vertical. / The physical model is first coupled to a biological model where new production is given by a restoring condition of surface nitrate towards its observed concentration. The coupled model is used to examine Martin et al.'s (1987) hypothesis that lateral transport and decomposition of slow or non-sinking organic matter can cause a non-local balance between the remineralization rate and the overlying new production rate in open ocean regions. The role of the Gulf Stream in nutrient transport is examined. The model results agree well with the North Atlantic nutrient transport calculated from observed nutrients and hydrographic data. The model results suggest that the thermohaline overturning circulation and the Gulf Stream horizontal recirculation play an important role in the North Atlantic nutrient distribution. / The physical model is then tested in the seasonal mode, and coupled with a biological model which is based on nitrate limiting the rate of new production. The model simulated seasonal oxygen cycle agrees well with the results of observational studies and 1-dimensional model simulations. The oxygen utilization rate below the euphotic zone provides a useful estimate of new production. / A 1-dimensional time dependent particle cycling model with two particle size classes based on Clegg and Whitfield (1990) is then developed. The simulated total organic carbon concentration and large particle flux are consistent with observations and other 1-dimensional model simulations. The downward transport of organic carbon is mainly accomplished by the fast sinking large particles, which comprise a small fraction of the total particulate mass. The steady state version of the particle model is also coupled with the 3-dimensional physical model. The magnitudes of simulated organic carbon flux and total organic matter concentration are comparable with observations.

No description available.

Hydrothermal vent ecosystems are defined by steep thermal and chemical gradients. Chemosynthetic microorganisms are the primary producers in these systems, utilizing the available chemical energy to support substantial animal biomass. The variety of chemical substrates provided by hydrothermal fluid and surrounding seawater enables a metabolically diverse community of microbes. However, our understanding of how abiotic factors such as temperature, geochemistry, and mineral substrate influence the activity of these microbes is limited. The overarching goal of this dissertation is to examine the influence of these abiotic factors on free-living microbial community composition, structure, and function. In this work I first examined the influence of temperature on primary productivity by using radio isotopic tracer studies to measure rates of carbon fixation by epi- and endolithic microbial communities from vent chimney sulfides. I show evidence that these communities fix more carbon at low temperatures, underscoring the importance of low temperature habitats in these environments commonly characterized by high temperature. I then utilized in situ RNA preservation to examine community-wide microbial activity in low temperature vent fluids throughout a vent field. These data show two distinct activity profiles that cross-cut canonical habitat descriptions, and highlight the importance of the intra-field waters among the discrete vents as regions of high primary productivity bearing similarity in microbial activity to plumes emanating from high temperature chimneys. Finally, I designed novel colonization devices to examine the influence of mineral substrate on microbial community composition, structure, and succession. Mineralogy influenced certain taxa. I also identified potential early and late successional taxa. The combination of metabolic rate measurements, metatranscriptomics, and colonization experiments presented here, all with co-registered geochemistry, underscore the substantial heterogeneity of these systems and offer insights into the relative strengths of the abiotic forces that help to govern these ecosystems. / Biology, Organismic and Evolutionary

In the context of declining populations of freshwater eels in Europe and North America and inspired by observations of Japanese eel spawning near seamounts, this study explored a possible spatial relationship between spawning American and European eels (Anguilla rostrata and A. anguilla) and geophysical features in the Sargasso Sea. A spatial analysis of positive and null catch sampling data from 1863 to 2007 found observations of young eel larvae significantly clustered over magnetic anomalies with higher than average intensities. These larval clusters occurred above the southwest Bermuda Rise and in the vicinity of the Vema Gap, a constricted abyssal channel connecting the Nares and Hatteras Abyssal Plains and directing flow of the abyssal bottom current. In this area, newly hatched larvae were positioned on either side, but not within, a 170 km wide high-magnetic gradient band located on the M0 anomaly. This gradient separated the centers of the distributions of the two species when they were ≤ 5 mm in length. Standard deviations of directional trends indicated probabilities in dispersal patterns, highlighting a potential tool for modeling larval distributions. Like other species undergoing oceanic migrations, eels have demonstrated a magnetic sensory ability and may rely on magnetic cues for navigation. The geomagnetism of the ocean floor, which attenuates at a cubic rate with distance, may provide a clue to eel migratory routes and depth preferences or play a role in larval dispersal, metamorphosis and recruitment. Spatial analyses open new opportunities to study anguillid distributions in relation to geomagnetic and oceanographic features.

Attempts to use stable isotope carbon (delta13C) and nitrogen (delta15N) ratios to construct trophic positions and track mercury biomagnification in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman illustrated some potential differences in this environment compared to the aquatic ecosystem of the northern hemisphere. Due to the large difference in delta13C values (3.4‰) between zooplankton planktivorous fish species (S. crumenophthalmus, S. longiceps and R. kanagurta), zooplankton would seem to not be the primary diet of these fish species as commonly described in literature. Total mercury (T-Hg) concentrations of zooplankton were very low (range 0.010 to 0.037 mug·g-1, N = 27) with a mean methyl mercury (MeHg) of 0.001 mug·g-1 (range 1-19%, N = 5). The lowest T-Hg (0.003 mug·g-1) was found in planktivore (S. longiceps) and the highest was 0.760 mug·g -1 in predator shark (R. acutus) with average MeHg for all fish of 72% (range: 33-100%, N = 150). Using 15 N as indicator of trophic position, neither total mercury (T-Hg) nor methyl mercury (MeHg) were found to biomagnify. Regression slopes were 0.08 and 0.05 for T-Hg and MeHg respectively as a function of delta15 N. This indicates that biomagnification was lower in this tropical ocean compared to that found in freshwater and marine ecosystems of the arctic and temperate zones. Methyl mercury levels in the fish species commonly consumed are low and intake calculations showed that individuals can safely consume fish.

No description available.

No description available.

Marine sediments were assayed for their concentration of Vibrio spp. and Aeromonas hydrophila over 1 year. During this time period of ten of the currently known pathogenic Vibrio spp. were identified to occur in the marine sediments of Apalachicola Bay. A temporal variation was observed in which A.hydrophila, and to a lesser degree V.fluvialis, were found in the winter months, V.parahaemolyticus and V.vulnificus predominated the spring and summer, with non 0-1 V.cholerae and V.alginolyticus detected in the late summer and fall. These organisms were found in greatest numbers in the top 5 cm of sediment, but were detected down to 15 cm. Epidemiological data revealed a predominance of non 0-1 V.cholerae infections at the time the organisms were observed to flourish in the sediments. / A membrane filter method (the FAST method) has been developed to enumerate pathogenic vibrios extracted from sediments. Aliquots of sediments which were blended in a Waring Blender were collected on a black Nuclepore (0.2 $\mu$m pore) filters and heat fixed. Filters were treated to reduce the non-specific fluorescence of background sediment and allowed to dry. Antibody positive Vibrio cholerae non 0-1 cells appeared as cells surrounded by a fluorescent green halo or band. Detrital and other sediment particles appeared as pale green or could not be seen at all. The FAST procedure can be easily adapted for any pathogenic vibrio for which a specific antibody is available. / In the absence of a species-specific antibody, laboratories rely on conventional biochemical identification methods for genus and species identification. Apalachicola Bay waters and oysters were tested for the presence of Vibrio vulnificus, the most virulent of the pathogenic vibrios, during the time of greatest public health concern. Conventional biochemical identification methods were compared to serological and gene probe analysis for sensitivity in predicting the illness patterns of the same time period. Oyster analyses appear to correlate more closely to the epidemiological data than water analyses. The biochemical identification methods appear to the most conservative for the protection of public health. More critical identification using the serological and gene probe methods appears to be the methods of choice for the regulatory community. / Source: Dissertation Abstracts International, Volume: 51-12, Section: B, page: 5745. / Major Professor: Paul A. LaRock. / Thesis (Ph.D.)--The Florida State University, 1990.

<p>Increased pressure has been placed on researchers to focus on processes at an ecosystem level. However, ecological processes operate at multiple scales from an individual predator up to ocean basin migrations, and research across these scales is extremely difficult. More accurate and detailed understanding of prey distributions relative to physical and biological features can greatly aid in understanding top predator distributions and ultimately ecosystem functioning. High resolution acoustic data is a critical tool that can be used to investigate food web linkages at many spatial scales. At a broad scale, migratory top predators are often modeled relative to oceanographic structure as a proxy for the distribution of their prey. At a fine scale, combining novel technologies including fisheries acoustics, real time oceanographic sensors, and digital tags allows examination of decisions made by an individual foraging whale. In the Gulf of Mexico, fish distributions at fine scales (both horizontal and vertical) were examined relative to hypoxic bottom waters to understand potential ecosystem effects. Forage fish distribution (sand lance, Ammodytes spp.) were measured relative to physical features and oceanographic processes up to the decision making of a top predator, the humpback whale (Megaptera novaeangliae). The effect of geostrophic currents and environmental regimes on the deep scattering layers of the central tropical pacific were examined relative to sightings of marine mammals in the area. Analyses across trophic levels and at multiple scales is an important step towards understanding community ecology and ecosystem processes in pelagic systems.</p> / Dissertation

I conducted a management assessment for the conservation of benthic resources harvested by small-scale hookah divers in the northern Gulf of California (NG), Mexico, and analyzed the reproductive ecology of the black murex snail. Open access to the fisheries, combined with national and international market pressure, fishing methods, and the timing of fishing activities have caused an evident decline in production, the use of new fishing zones, and a shift of fishing effort towards deeper areas. However, the organization of the diving sector and its initiatives to establish forms of regulation provide an opportunity to alleviate this situation. I conclude that comanagement has the potential to be an effective management system for the benthic resources of the NG, a system that could be facilitated by the sedentary and semisedentary nature of these resources. An informal type of co-management arena is already in place with the possibility of being formalized and solidified.