The aim of this study was to investigate spatial changes in the trophic and energy pathways of the benthic community in the shallow shelf waters of the sub-Antarctic Prince Edward Islands (PEI). A combination of stable isotope and fatty acid analyses were used to provide a time-integrated view of the assimilated feeding history of selected components of the PEI benthic community. This study forms part of the larger project entitled “Variability in the Southern Ocean ecosystems” and is a contribution to the South African National Antarctic Programme (SANAP). During austral autumn 2009, benthic specimens were collected from 10 stations (from depths of 70 to 295 m) in different regions around the PEI: inter-island shelf (upstream, between and downstream of the islands) and nearshore. Historical data were combined with new data collected during 2009 to assess the long-term trends in the feeding ecology of the benthos in the region of the islands. The stable isotope and fatty acid signatures of the benthic suspension- and deposit-feeding organisms generated during this study suggested that these two communities incorporated both phytoplankton and kelp in their diets. Stable isotope, and to a lesser extent fatty acid signatures, indicated that kelp contributed more to the diets of those organisms in close proximity to the kelp beds (nearshore stations) than those from the inter-island region. Overall, however, pelagic phytoplankton was the dominant food source in the diets of all organisms, even for those living near the kelp beds. Notable exceptions were the sponges and bryozoans, in which kelp and phytoplankton contributed similar proportions to their diets, most likely resulting from a size restricted feeding mode. There were, therefore, no distinct spatial differences in the importance of the various food sources. However, fatty acid compositional data indicated increased food quality between and within the lee of the islands compared to upstream. The organisms collected upstream of the PEI had substantially lower quantities of total fatty acids (TFAs) than organisms of the same species collected from nearshore, open shelf or downstream stations. The increased food quality between and within the lee of the islands was likely a result of the “island mass effect”, which reflects increased phytoplankton concentrations at the PEI. The fatty acid profiles of hyperbenthic shrimp Nauticaris marionis, a key species in the PEI ecosystem, revealed no distinct ontogenetic or spatial patterns. This result is in contrast to the stable isotope analyses, which detected both spatial and ontogenetic differences in the diet of the shrimp. Nearshore shrimp were more ₁₃C-enriched than those from the inter-island region, suggesting increased kelp entering the food web within these regions. In addition, the shrimps demonstrated enrichment in δ₁₃C and δ₁₅N signatures with an increase in size, resulting in a relatively distinct separation of size classes, thus reflecting niche separation through their diets. The fatty acid profiles revealed that the shrimp all contained large proportions of polyunsaturated fatty acids (PUFAs) and essential fatty acids (EFAs), indicating that the quality of food consumed was similar among size class and region despite the niche separation and variation in carbon sources utilised. In addition, diatom and dinoflagellate fatty acids (20:5ω3 and 22:6ω3, respectively) occurred in the highest proportions in N. marionis, highlighting the importance of phytoplankton (indirectly) in their diet. These results represent strong evidence that phytoplankton is an importance food source in the PEI ecosystem. The temporal investigation of isotope signatures in the benthos at the PEI indicated that N. marionis demonstrated an overall depletion in δ₁₃C signatures over the period of 1984 to 2009 (nearshore: -2.55 ‰, inter-island: -2.32 ‰). Overall, the benthic community showed similar depletions in δ13C signatures (from -1.96 to -4.70 ‰), suggesting that shifts have occurred in the carbon signatures at the base of the food web. The depletion in δ₁₃C signatures of the benthos at the PEI most likely reflects increased contributions of smaller slow growing phytoplankton cells (more depleted signatures than large fast growing cells) in the diets of these organisms over time. These diet shifts, in turn, suggest a decrease in productivity has occurred at the islands, likely due to a decreased frequency and intensity of the “island mass effect”. Decreased phytoplankton productivity at the PEI likely results from the southward shift in the average position of the sub-Antarctic Front (SAF), most likely in response to climate change, which in turn promotes flow-through conditions rather than retention at the PEI.

The objective of this research was to improve our understanding of how changes in the environment affect ecological processes. Change detection is often confounded by the large variation found in ecological data due to the difficulty of finding replicates in nature. Intertidal communities were chosen for studies of biophysical interactions because the physical gradients are very strong, thus creating complex systems within spatial scales that are easily sampled. The selection of replicate beach habitats was the first step in designing a sampling protocol for comparative analyses of nearshore community structure. A high resolution shoreline partitioning model was developed to quantify the physical attributes of homogeneous shoreline segments and to statistically cluster replicate segments. This model was applied at 3 locations in Washington State. A portion of the south shore of San Juan Island was partitioned and the physical attributes quantified. Three groups of rocky segments differing only in slope angle were selected for biological sampling. The objective was to test the fidelity of macroalgal and invertebrate populations to replicate bedrock shore segments. The results showed that community structure and population abundances were more similar within groups of replicate segments (similar slopes) than among groups (different slopes). In South Puget Sound, community structure was compared to test for a deterministic organization of communities among replicate soft sediment beaches in an estuary. The results showed that replicate beach segments support similar communities, that communities become less similar as the distance between replicates increases, and that replicates within or among nearshore cells with similar temperature and salinity support communities that are more similar than replicates among cells with different water properties regardless of distance. On the outer Olympic coast, community comparisons were made among 9 sand beaches over a shoreline distance of 250 km. The results show that these communities are similar within segments and within nearshore cells, but because of population abundance fluctuations, the communities were different among cells and among years. This study shows that processes determining patterns in nearshore habitats can be quantified, which is a significant contribution to studies of habitat distribution and the siting of marine preserves. / Graduation date: 2000

This study examined the foraminifera and the ecologic conditions of the benthic environment of the Oregon shelf and the uppermost slope (75-550 m depth) between 143°45' N and 144°40' N. Seasonal collections monitored the near-bottom marine environment and the sedimentary substrate at 16 stations. The foraminiferal benthic fauna was examined from eight seasonal stations and two additional stations. Use of a multiple corer provided randomly selected subsarnples of the sediment for ecologic and faunal analyses. Use of water bottles that triggered upon bottom impact provided measurements of the water as close to the bottom as 0. 6 m. Computerized data processing and statistical analyses aided the ecologic and faunal evaluations. The environmental study showed the existence of considerable variation in the hydrography of near-bottom waters, especially between summer and winter (upwelling and non-upwelling) collections at the same station. Upwelling conditions directly affect the benthic Redacted for Privacy environment. In addition, the water at any one place, at least dciring upwelling, was so well mixed that vertical stratification did not exist between 0.6 and 5.0 m off the bottom. Statistically significant sea-. sorial variations in surface sediments at the same station were not observed. The living benthic foraminiferal fauna exhibited considerable within-station variation both in species composition and in specimen size of selected species. The percent abundance of individual dominant species varied in adjacent cores (subsamples) by amounts up to 46%. Living specimens of a single species were found that were three times as large as the smallest living specimen from the same sample, yet there was no evidence of a multimodal size distribution resulting from age classes. The author suggests that the dominant species are aggregated and that the aggregations are colonies of asexually produced siblings. Lack of fit of species-frequency curves to the lognormal distribution indicated that relatively few species are fit to reproduce in a particular environment; most juvenile specimens that enter a particular environment belong to species that will not thrive there and either die or simply maintain growth with little chance of reproductive success. The existence of colonial aggregations of individuals is considered to provide the best explanation of the observed variations between adjacent samples. However, the observed variations could be due to sampling error or to substrate microheterogeneity. A possible natural community of 15 dominant species has been determined for those species that form a consistent part of each other's biologic environment. The community crossed the depth and substrate boundaries upon which the stations were selected and appeared to be a general community for the Oregon outer shelf. The limits of the community appear to be determined mostly by water depth, with approximate boundaries at 75-100 m and somewhere between 200-500 m. Regression analyses to determine the ecologic control on the foraminiferal fauna did not indicate a close correspondence between faunal parameters and environmental variables. Regression analyses to determine the ecologic control on mdividual species indicated that most species depended upon a set of two to four environmental variables rather than upon one single limiting factor. The set for each species was different. Temperature. phosphate concentration and oxygen concentrations were common hydrographic members of sets; percent silt, percent sand, percent clay, organic carbon content and organic nitrogen were common sedimentary members of sets. / Graduation date: 1972

Thesis (M.S.) in Marine Biology--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 62-72).

No description available.

Benthic uptake of mercury (Hg) governs bioavailability to fish yet there are still large gaps in our knowledge of what mediates this process. Without this information it is difficult to ascertain where Hg accumulation in the foodweb will be greatest. In the St. Lawrence River Area of Concern (AOC) at Cornwall, one contaminated zone (Zone 1) shows elevated Hg in yellow perch (Perca flavescens) and their prey items compared to those from other zones in the AOC. Greater availability of Hg to benthos due to unique physical features (large deposition of woodfibre deposits) of Zone 1 is hypothesized to account for this observation. In this study, amphipods (Gammarus fasciatus) and (Echinogammarus ischnus) were collected in Zone 1 using artificial substrates between June-September 2007, and Hg concentrations compared to those obtained in sediments and porewaters of surficial sediments, as well as methane gas evasion rates. Methylmercury (MeHg) concentrations in amphipods were significantly related to porewater total Hg (THg) and MeHg concentrations. No parallel relationship was found for sediment Hg concentrations or methane bubbling rates from sediments. Spatial and temporal trends in Hg bioavailability were evident from significant relationships with water column depth and temperature. Water column depth was associated with higher MeHg concentrations in amphipods and porewaters. Concentrations of porewater MeHg were above the detection limit in all of the June samples, the month which also coincided with highest amphipod MeHg concentrations. Finally, sediment organic matter may be influencing patterns of MeHg availability in Zone 1, and displayed a negative relationship to amphipod MeHg. Although bubbling from contaminated sediments did not directly correlate with amphipod Hg uptake, future studies should look at the influence of bubbling on the redistribution of contaminated sediment particles within the zone. / Thesis (Master, Biology) -- Queen's University, 2008-12-30 23:34:20.287

No description available.

No description available.

Although the deep seafloor represents the largest biome on the planet, its benthos has remained understudied because of logistical difficulties and the cost of access. Long-term, time-series information is needed to understand the small-scale and inter-annual variations required to build predictive models of ecological processes. In this thesis, we employed three newly developed observatory systems, which coupled in situ imagery with environmental data to examine ecological processes in three deep-sea benthic habitats: 1) Megabenthic surface bioturbation on the upper continental slope (400m depth) near Barkley Canyon, off Vancouver Island, 2) Thermal response in polynoid taxa at Main Endeavour Hydrothermal Vent Field (2,100m depth) on the Juan de Fuca Ridge and 3) Behavioural rhythms and bacterial mat growth in Saanich Inlet (100m), a fjord in southern Vancouver Island. To ensure that the imagery collected was useful for quantitative hypothesis testing by a single observer, we employed a step-wise methodological approach, taking advantage of previously acquired knowledge and, in two cases, the interactive nature of cabled observatories, to tailor the sampling frequency to the variables of interest. The application of a diverse array of image analysis techniques and statistical models, easily extendable to other systems, was also demonstrated. The results obtained while conducting the protocol optimization phase described organism and community level responses to environmental variations. Using a remotely operated camera connected to the NEPTUNE Canada cabled observatory, we estimated that total surface sediment turnover by sea urchins and flatfish, the two most important megafaunal contributors, within the field of view required 93 to 125 days in the absence of phytodetrital accumulations. When employing a camera-temperature array system, the most frequently observed mobile megafaunal species, two polynoid taxa, were not found to exploit the recorded temperature gradients suggesting that they employed a thermoconforming strategy to cope with thermal variability. In the aphotic, mostly hypoxic benthos of Saanich Inlet, strong behavioural entrainment, neither diel nor tidal, was not observed. However, significant changes in species composition and bacterial mat substratum coverage were observed following intrusion of oxygenated waters, a yearly event resulting from specific bathymetric features and oceanographic dynamics of this fjord. A Bayesian approach to data modeling was found to be particularly well suited to protocol optimization purposes as complex models could be more easily and intuitively implemented. The further application of our multi-disciplinary step-wise approach will reduce the time required to approach new ecological questions and improve integration of studies carried in different locations. By carefully choosing ecosystem functions which can be used as indicators of change, the current baseline state of the system can be described. Informed long-term monitoring initiatives can then be implemented in order to quantify global ocean responses to anthropogenic factors such as climate change, resource extraction or eutrophication. / Graduate

Graduation date: 1984