Browsing by Subject "Biology, Oceanography"

Reactive oxygen species (ROS) are produced endogenously in all aerobes and are induced by environmental stressors. ROS oxidize and disable essential cellular components such as DNA, proteins, and lipid membranes. Exposure to metals, polycyclic aromatic hydrocarbons (PAHs), and some pesticides can induce oxidative stress in marine invertebrates. All aerobic organisms have a network of antioxidants and enzymes to quench ROS and prevent oxidative damage. This dissertation examines antioxidant and oxidative stress biomarkers in endemic molluscs and crabs from two natural extreme environments: deep-sea hydrothermal vents in the Lau and North Fiji Basin, and cold seeps in the Gulf of Mexico. In addition, the acute toxicity and sub-lethal effects of four insecticides and an herbicide are examined in the estuarine blue crab, Callinectes sapidus. Blue crabs are North Carolina's most important fishery species and are frequently found in agricultural drainage ditches, an example of an anthropogenic extreme environment.

Total glutathione, catalase, superoxide dismutase, and lipid peroxidation levels were of the same respective order of magnitude in the two vent gastropods, Alviniconcha sp. and Ifremeria nautilei, and vent mussel, Bathymodiolus brevior. These biomarkers activities were similar to those from previous reports on Mid-Atlantic Ridge mussels, except for ~100-fold higher lipid peroxidation levels among Lau molluscs. Principal component analysis (PCA) of mollusc tissue-specific biomarker levels grouped individuals by species rather than by site.

Biomarker levels in the seep mussels Bathymodiolus childressi, B. brooksi, and B. heckerae were similar across species except for elevated foot and gill cytosolic SOD in mussels from MC-640 compared to those from AC-645. PCA of seep mussel biomarker levels differentiated by species with B. childressi isolated from B. brooksi and B. heckerae. The addition of B. brevior biomarker data to the PCA showed them grouping around B. brooksi and B. heckerae. Bathymodiolus childressi is ancestral to the other species and contains only methanotrophic endosymbionts. Whether symbionts play a role in alleviating possible toxic conditions remains unknown.

Pesticides were acutely toxic to blue crabs in the order of Lambda-cyhalothrin > imidacloprid ≈ aldicarb > acephate ≈ Roundup® (glyphosate). Megalopae were almost always more sensitive to pesticides than early stage juveniles. Commercial formations of pesticides generally showed similar toxicity to active ingredients alone. Exposure to LC₂₀ levels of acephate, aldicarb, imidacloprid and Roundup significantly increased the frequency of juvenile mortality after molting. There was no significant change in total glutathione or lipid peroxidation of exposed megalopae. Lambda-cyhalothrin-, imidacloprid-, and aldicarb-based products have the potential to cause acute toxicity and molting-related mortality in shallow creeks and ditches.

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.

No corner of the world's oceans is untouched by humans. Yet in marine science, management, and conservation, oceans are consistently treated as 'unpeopled', that is, human systems are divorced systematically from ecological systems, and assumptions of human/environmental relationships are oversimplified. This dissertation aims to contribute to interdisciplinary, or 'peopled', approaches to marine sciences and management by integrating biophysical and social sciences, specifically historical ecology and resilience thinking on social-ecological systems. Herein, I examine this theoretically (Chapter 2) and empirically by investigating the coral reefs of Hawaii Island's Kona Coast historically, through the oral histories of 'ocean experts', diverse locally-living people from diverse knowledge systems. I investigate human, biophysical, and social-ecological aspects of 'ecological change.'

Chapter 3 demonstrates that currently there are six expert ocean knowledge systems surrounding Kona's reefs: Native Hawaiians, dive shop operators, tropical aquarium collectors, shoreline fishers, scientists, and conservationists. These are distinct in what experts know about Kona's reefs, and how they know it. The giving and taking of authority between ocean experts, and among people and marine management, influences the condition of the biophysical, social, and management dimensions of Kona's reef systems.

Chapter 4 examines the biophysical dimensions of change, specifically the historic abundance and distribution of 271 coral reef species. Ocean expert's observations of ecological change are surprisingly consistent, regardless of perspective. Historically, species tend to follow one of eight trends in abundance and distribution, grouping into what I term 'social-ecological guilds'. Analyzing these data with Western scientific frameworks (e.g., trends in apex predators, herbivores, corallivores) proved inappropriate, compared to qualitative approaches. Engaging a multiplicity of perspectives reveals historical ecology broader and richer than from any one knowledge system alone.

Chapter 5 identifies coupled aspects of marine social-ecological systems, or what I call 'keystone social-ecological features'. I examine 8 features in detail and show how they are central to understanding 'sea change' through such diverse perspectives. Comparing expert's perceptions and responses to ecological through keystone features, I show that 'change' differs based on sociopolitical, economic, etc. perspective. Understanding relationships between and among people, the ecosystem, and marine management institutions is critical for improved ocean management.