233 research outputs found
Enhanced understanding of ectoparasite–host trophic linkages on coral reefs through stable isotope analysis
No full textAbstractParasitism, although the most common type of ecological interaction, is usually ignored in food web models and studies of trophic connectivity. Stable isotope analysis is widely used in assessing the flow of energy in ecological communities and thus is a potentially valuable tool in understanding the cryptic trophic relationships mediated by parasites. In an effort to assess the utility of stable isotope analysis in understanding the role of parasites in complex coral-reef trophic systems, we performed stable isotope analysis on three common Caribbean reef fish hosts and two kinds of ectoparasitic isopods: temporarily parasitic gnathiids (Gnathia marleyi) and permanently parasitic cymothoids (Anilocra). To further track the transfer of fish-derived carbon (energy) from parasites to parasite consumers, gnathiids from host fish were also fed to captive Pederson shrimp (Ancylomenes pedersoni) for at least 1 month. Parasitic isopods had δ13C and δ15N values similar to their host, comparable with results from the small number of other host–parasite studies that have employed stable isotopes. Adult gnathiids were enriched in 15N and depleted in 13C relative to juvenile gnathiids, providing insights into the potential isotopic fractionation associated with blood-meal assimilation and subsequent metamorphosis. Gnathiid-fed Pedersen shrimp also had δ13C values consistent with their food source and enriched in 15N as predicted due to trophic fractionation. These results further indicate that stable isotopes can be an effective tool in deciphering cryptic feeding relationships involving parasites and their consumers, and the role of parasites and cleaners in carbon transfer in coral-reef ecosystems specifically
Aliens in paradise: a comparative assessment of introduced and native mangrove benthic community composition, food-web structure, and litter-fall production
No full textPh.D
Exploring US Mid-Atlantic Margin methane seeps : IMMeRSS, May 2017
No full textAuthor Posting. © The Oceanography Society, 2018. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 31, no. 1, supplement (2018): 93
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Effects of Oil on the Deep Gulf of Mexico Benthos
No full textA dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR of PHILOSOPHY in MARINE BIOLOGY from Texas A&M University – Corpus Christi in Corpus Christi, Texas.The deep sea ( > 200 m) is the largest habitat on Earth. However, the deep sea ecosystem is poorly understood relative to most other habitats due to the difficultly in accessing it. As human activities increase in the deep sea, the need to understand processes occurring in the deep and impacts on these processes by human activities also increases. This study examines the importance of the deep sea to humans as well as the impacts of oil on deep-sea communities.
Approximately 5 million barrels of oil were released during the Deepwater Horizon spill, much of which remained in the deep sea. Shortly after the spill ended, benthic diversity and abundance were lower near the Deepwater Horizon wellhead compared to deep-sea areas not affected by the spill. Diversity increased with increasing distance from the wellhead while abundances peaked at intermediate distances suggesting a toxicity vs. enrichment effect. There were also several benthic taxa identified as potential indicators of oil-contaminated and uncontaminated areas.
Oil is released from the seafloor via natural seepage as well. Benthic abundance and diversity differed among different types of seep communities (microbial mats, tubeworms, and soft-bottom seeps), between seep and non-seep areas, and between seep and spill areas. Unlike communities impacted by the DWH spill, there did not appear to be taxa specifically associated with natural seepage. In fact, high variability in community structure appeared to be the best indicator of natural seepage, with specific seep communities not only different from background and spill communities, but also different from other seep communities.
Oil that enters the oceans does not remain there indefinitely. Oil released by both natural and anthropogenic processes is removed from the marine environment naturally by burial in the seafloor, degradation by bacteria, and dilution in the water column. The removal of oil by the environment is an example of an ecosystem service termed waste regulation. Waste regulation was examined in the context of the Deepwater Horizon spill by calculating the monetary value of the natural removal of oil spilled. Estimations of fates of the DWH oil as well as cleanup costs were examined. It was estimated that 10’s of billions of dollars were saved from offshore waste regulation following the spill.
This dissertation concludes that the differences among communities at natural seeps, areas impacted by the spill, and areas not impacted by oil were numerous. Benthic communities associated with deep oil spills were defined, allowing for the future assessment of damages caused by deep-sea spills. Communities associated with natural seepage were different from other habitats as well as other seep communities, emphasizing the unique nature of each seep location in the Gulf of Mexico. Valuation of deep-sea services will provide monetary costs for destructive practices in the deep sea. Knowledge of deep-sea services is also important to communicate to the public to ensure these services will be protected. This dissertation provides information on the effects of the first deep-sea oil release on benthic communities, differences between impacts of natural and anthropogenic oil required to assess spill damages, a unique comparison of several different seep communities throughout the Gulf of Mexico, as well as an initial, partial value of waste regulation provided by the deep-sea environment. The work performed can help guide future policies concerning deep-sea drilling and assist in the identification and protection of unique habitats in the deep sea. Communication of deep-sea benefits can provide the public with motivation to care about the fate of the deep sea, which is far beyond the reach of most people.Life SciencesCollege of Science and Engineerin
Deep-sea coral biogeography and community structure in tropical seamount environments
No full textAs the largest and most poorly environment on Earth, the deep-sea is facing global threats from climate change and anthropogenic disturbance further compounded by the lack of critical baseline data on seafloor species composition and community structure. Many data-deficient regions include those in geographically-isolated offshore environments, like low-latitude seamounts, where sampling and surveys have been limited, resulting in critical knowledge gaps that do not allow for effective conservation measures to be realized. This work seeks to characterize the coral fauna of tropical seamount environments greater than 150 m depth and understand the environmental controls on species distribution and community assembly for long-lived, ecologically-important species, primarily from the Octocorallia, Antipatharia, Stylasteridae, and Scleractinia. Methodologies for accomplishing this research have included analysis of remotely operated vehicle (ROV) video surveys and identification of collected voucher specimens to understand biogeographic patterns within coral communities on seamounts and other rugged seafloor features in 3 different regions: the tropical western Atlantic (Anegada Passage), the equatorial central Pacific (Phoenix Islands), and the tropical eastern Pacific (Costa Rica). These regions represent vastly different oceanographic regimes in terms of biological productivity and water column structure resulting in differential effects on deep-sea coral communities. Evidence from these three regions has shown significant effects of the role that oceanic water masses have on structuring deep-water coral biodiversity and suggests that these features, along with other abiotic environmental variables, are important indicators for understanding species distribution patterns, community structure, and global biogeographic patterns. More broadly, the results of this work have demonstrated the capabilities of exploratory ROV surveys, across multiple platforms, to add practical knowledge to coral species inventories and identify bathyal biogeographic patterns in remote regions of the deep sea. The results of this work, serving as baseline coral biodiversity surveys for each area, are also germane to evaluating the effects of human-mediated disturbance and global climate change in the deep ocean. These disturbances also include ocean acidification, ocean deoxygenation, deep-sea mining, and bottom-contact fishing, all of which have been identified as threats to the seamount benthos.Biolog
The ecology of deep-sea chemosynthetic habitats, from populations to metacommunities
No full textChemosynthetic ecosystems are habitats whose food webs rely on chemosynthesis, a process by which bacteria fix carbon using energy from chemicals, rather than sunlight-driven photosynthesis for primary production, and they are found all over the world on the ocean floor. Although these deep-sea habitats are remote, they are increasingly being impacted by human activities such as oil and gas exploration and the imminent threat of deep-sea mining. My dissertation examines deep-sea chemosynthetic ecosystems at several ecological scales to answer basic biology questions and lay a foundation for future researchers studying these habitats. There are two major varieties of chemosynthetic ecosystems, hydrothermal vents and cold seeps, and my dissertation studies both. My first chapter begins at cold seeps and at the population level by modeling the population dynamics and lifespan of a single species of tubeworm, Escarpia laminata, found in the Gulf of Mexico. I found that this tubeworm, a foundation species that forms biogenic habitat for other seep animals, can reach ages over 300 years old, making it one of the longest-lived animals known to science. According to longevity theory, its extreme lifespan is made possible by the stable seep environment and lack of extrinsic mortality threats such as predation. My second chapter expands the scope of my research from this single species to the entire cold seep community and surrounding deep-sea animals common to the Gulf of Mexico. The chemicals released at cold seeps are necessary for chemosynthesis but toxic to non-adapted species such as cold-water corals. Community studies in this area have previously shown that seeps shape community assembly through niche processes. Using fine-scale water chemistry samples and photographic mapping of the seafloor, I found that depressed dissolved oxygen levels and the presence of hydrogen sulfide from seepage affect foundation taxa distributions, but the concentrations of hydrocarbons released from these seeps did not predict the distributions of corals or seep species. In my third chapter I examine seep community assembly drivers in the Costa Rica Margin and compare the macrofaunal composition at the family level to both hydrothermal vents and methane seeps around the world. The Costa Rica seep communities have not previously been described, and I found that depth was the primary driver behind community composition in this region. Although this margin is also home to a hybrid “hydrothermal seep” feature, this localized habitat did not have any discernible influence on the community samples analyzed. When vent and seep communities worldwide were compared at the family-level, geographic region was the greatest determinant of community similarity, accounting for more variation than depth and habitat type. Hydrothermal vent and methane seeps are two chemosynthetic ecosystems are created through completely different geological processes, leading to extremely different habitat conditions and distinct sets of related species. However, at the broadest spatial scale and family-level taxonomic resolution, neutral processes and dispersal limitation are the primary drivers behind community structure, moreso than whether the habitat is a seep or a vent. At more local spatial scales, the abiotic environment of seeps still has a significant influence on the ecology of deep-sea organisms. The millennial scale persistence of seeps in the Gulf of Mexico shapes the life history of vestimentiferan tubeworms, and the sulfide and oxygen concentrations at those seeps determine seep and non-seep species’ distributions across the deep seafloor.Biolog
Quantifying the sphere of influence: ecology and trophic dynamics of methane seep communities along the Pacific Costa Rican Margin
No full textChemosynthetic ecosystems in the deep sea hold vast amounts of untapped energy that until recent decades have been largely unobtainable. With the growing demand for resources and constant advancements in technology, these ecosystems and the diverse communities that inhabit them now face increasing pressure from anthropogenic exploitation activities. Thus, employing effective management and conservation strategies to avoid devastating these long-lived communities is imperative. However, effective protection hinges on a thorough understanding of these ecosystems. Here, I present a number of studies conducted on methane seeps along the Pacific Costa Rican Margin (CRM), exploring various ecological dynamics and highlighting the unique biodiversity thriving there. These studies aim to address gaps in our knowledge regarding the “sphere of influence” surrounding chemosynthetic methane seeps, providing insights into the flow of energy within these ecosystems, their spatial dynamics and how they interact with background deep-sea habitats. In Chapter 2, I employ a novel seascape approach using systematic surveys of several actively seeping areas to characterize the seep communities and delineate distinct seep zones, testing for inter- and intraspecific differences in community structure. Our results reveal nuanced patterns in α and β diversity between sites and across different zones, driven largely by depth. Additionally, I identify transitional zones extending the spatial extent of the seeps by up to 300 meters, emphasizing the “sphere of influence” surrounding these ecosystems.Biolog
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