Papers by Thomas Sawyer Hopkins
Polar Biology, 1994
Water level, ash content, proximate (protein, lipid, carbohydrate and chitin) and elemental (carb... more Water level, ash content, proximate (protein, lipid, carbohydrate and chitin) and elemental (carbon and nitrogen) composition were analyzed in twentythree species of Antarctic zooplankton collected during the austral fall (1986) and winter (1988) from the Scotia/Weddell Sea region. Extremes in water level, ash content and organic components were typified by copepods and gelatinous forms. Ostracods and polychaetes were generally similar in composition to copepods, being only slightly higher in water level and ash content. Chaetognaths exhibited a composition intermediate in character with some components similar in value to that shown by crustaceans (i.e. protein) while other components were more in the range of values seen in gelatinous forms (i.e. water level and ash content). Protein was the major proximate component and measured values (as % AFDW) were fairly uniform among non-gelatinous species (x = 33.9 _+ 6.9). Lipid levels were variable, with high values (>30% AFDW) only found for the copepods Calanoides acutus, Calanus propinquus and Euchaeta antarctica. Carbohydrate values were low in all species examined. Chitin was measured in crustacean species only. With the exception of C. acutus (x = 2.5% AFDW chitin), values were similar among species with mean values being slightly higher in fall (x = 11.8 _ 2.5) than in winter (x-6.7 + 1.8). Among non-gelatinous species, the ratio of carbon to nitrogen was positively correlated with the lipid to protein ratio, underscoring the compositional association between elemental and proximate components in these groups. In gelatinous species, the relationship between carbon:nitrogen and lipid:protein was inconsistent and less pronounced. Caloric content
Journal of Marine Systems, 1999
Journal of Geophysical Research, 1995
Nutrient and oxygen distributions were measured during a hydrographic survey of the Northeast Wat... more Nutrient and oxygen distributions were measured during a hydrographic survey of the Northeast Water Polynya off the northeast coast of Greenland (77-81 °N, 6-l7°W) during July-August 1992 and were interpreted in the context of satellite imagery of the region. Satellite imagery revealed a convoluted plume of cold water flowing along isobaths from underneath fast ice in the southwestern portion of the polynya toward the northeast. This plume carried relatively high nutrient and low oxygen inventories. Nitrate to phosphate ratios were low in the polar water, consistent with an ultimate source of this water mass in the Pacific sector of the Arctic Ocean. It is hypothesized that the low N :P Arctic outflow might be the cause of nitrate limitation along the east coast of America as far as Cape Hatteras. Gradients of both nutrients and oxygen inventories in the euphotic zone were observed along and across the axis of mean flow within the polynya and are shown to be due to net production of organic matter. On the basis of these spatial gradients of nitrate and oxygen, an assumed along-axis current velocity of 10 cm s-1 , and the observed relationships of biologically removed inorganic carbon with nitrate and oxygen, the net organic matter production was estimated to be 40-60 mmol(C) m-2 d-1 • This represents the organic carbon available for export from the polynya euphotic zone. Nutrient-deficient and oxygen-rich waters were observed merging with the southward flowing East Greenland Current, suggestive of possible export, however, the ultimate fate of organic carbon produced within the polynya requires further study.
Continental Shelf Research, 1986
Chemistry and Ecology, 2004
ABSTRACT This work reports on the temporal variability of the deep-chlorophyll a maximum (DCM) in... more ABSTRACT This work reports on the temporal variability of the deep-chlorophyll a maximum (DCM) in a Mediterranean coastal environment. In contrast to a supply through vertical diffusion normally found offshelf, in the study area the nutrients were supplied laterally through intermittent, pycnoclinal intrusions over the shelf by the enriched Messina Mixed Water mass. A 48 h time series revealed a strong variability in the nutrient concentrations and size-fractioned chlorophyll a distributions. This variability appeared to be less correlated with the diurnal biological cycle and more correlated with the availability of newly advected nutrients. The observations also demonstrated that the planktonic community of DCM remains vertically non-homogenous when exposed to strong vertical shears caused by deformations in the depth of the pycnocline. For this shelf situation, assumptions regarding the distribution of the DCM, e.g., steady state, vertical or horizontal coherence, were all counterindicated.
Marine Geology, 1985
... PART I: SHOREFACE DYNAMICS DONALD JP SWIFT~, ALAN WILLIAM NIEDERODA2 , CHISTOPHER E. VINCENT3... more ... PART I: SHOREFACE DYNAMICS DONALD JP SWIFT~, ALAN WILLIAM NIEDERODA2 , CHISTOPHER E. VINCENT3 and TOM SAWYER HOPKINS4 ~Exploralion ... we know that the shoreface slope decreases with decreasing grain size (Langford-Smith and Thom, 1969; Wright ...
ABSTRACT In late summer, production and utilization of carbon in the stratified water of the Midd... more ABSTRACT In late summer, production and utilization of carbon in the stratified water of the Middle Atlantic Bight appears to approach steady-state conditions. In the euphotic zone there is a paniculate organic carbon (POC) pool of ̃6000 mg Cm -2. Primary production adds ̃350 mg C m -2 d -1, while zooplankton ingestion removes ̃450 mg C m -2 d -1, of which ̃135 mg C m -2 d -1 are returned to the POC pool as feces. Sinking of POC averages ̃240 mg C m -2 d -1. Thus, there is a net loss from the euphotic zone of ̃200 mg C m -2 d -1, which represents a removal rate from the POC pool of ̃3%d -1. However, sinking losses of phytoplankton carbon from the POC pool were small (̃12 mg C m -2 d -1), which suggests that most of the primary production enters the pelagic food chain. This is in sharp contrast to the conditions in early spring, when the POC pool increases substantially, and the main loss is sinking rather than heterotrophic consumption.
A description of the seasonal cycle and interannual behavior of the Northeast Water (NEW) Polynya... more A description of the seasonal cycle and interannual behavior of the Northeast Water (NEW) Polynya based upon a series of daily total ice concentrations derived from passive microwave satellite observations (1978–1994) is presented. The integrated ice-free areal extent within the region extending from 76 to 82°N and from the coast of northeast Greenland to the shelf break is used as
Nutrient and oxygen distributions were measured during a hydrographic survey of the Northeast Wat... more Nutrient and oxygen distributions were measured during a hydrographic survey of the Northeast Water Polynya off the northeast coast of Greenland (77-81 °N, 6-l7°W) during July-August 1992 and were interpreted in the context of satellite imagery of the region. Satellite imagery revealed a convoluted plume of cold water flowing along isobaths from underneath fast ice in the southwestern portion of the polynya toward the northeast. This plume carried relatively high nutrient and low oxygen inventories. Nitrate to phosphate ratios were low in the polar water, consistent with an ultimate source of this water mass in the Pacific sector of the Arctic Ocean. It is hypothesized that the low N :P Arctic outflow might be the cause of nitrate limitation along the east coast of America as far as Cape Hatteras. Gradients of both nutrients and oxygen inventories in the euphotic zone were observed along and across the axis of mean flow within the polynya and are shown to be due to net production of organic matter. On the basis of these spatial gradients of nitrate and oxygen, an assumed along-axis current velocity of 10 cm s-1 , and the observed relationships of biologically removed inorganic carbon with nitrate and oxygen, the net organic matter production was estimated to be 40-60 mmol(C) m-2 d-1 • This represents the organic carbon available for export from the polynya euphotic zone. Nutrient-deficient and oxygen-rich waters were observed merging with the southward flowing East Greenland Current, suggestive of possible export, however, the ultimate fate of organic carbon produced within the polynya requires further study.
The Journal of the Oklahoma State Medical Association, May 1, 2008
The purpose of this article is to provide the Oklahoma medical community with educational materia... more The purpose of this article is to provide the Oklahoma medical community with educational material regarding the assertive community treatment paradigm for the treatment of people with severe mental illnesses and to make the community aware that this is a resource available in several areas of the state. The concept, historical background, benefits, and cost effectiveness of assertive community treatment are discussed. The authors also seek to underscore the need for these programs in order to provide optimal care for the most severely ill psychiatric patients.
The level of degradation in coastal ecosystems has generated a new urgency to redirect the scienc... more The level of degradation in coastal ecosystems has generated a new urgency to redirect the science of assessing these systems in order that their economic value can assist in their conservation. This new challenge will combine the concept of biocomplexity and the methodology of the systems approach. Accordingly, biocomplexity suggests that changes in the structure and function of an ecosystem result from the interactions between sub-components of the system. Systems theory maintains that an understanding of a system’s response requires a simultaneous accounting of all significant internal and external interactions. A conceptual model of the circulation and nitrogen processing is used as a mechanism to illustrate how this combined approach might be applied to the Northern Adriatic ecosystem and its response to changes to its exogenous inputs. In part this involves the identification of the control points and interactions that determine the mass and information fluxes within the syste...
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Papers by Thomas Sawyer Hopkins