Biology and medicine


Photochemical and optical properties of antarctic waters in response to changing UV-B fluxes. David Kieber, State University of New York, College of Environmental Science and Forestry; and Kenneth Mopper, Washington State University. The decrease in stratospheric ozone over the Antarctic results in an increase in the UV-B flux in the ocean surface waters where photosynthesis occurs (the euphotic zone). The increase leads to cellular damage to aquatic organisms, as documented by photo-inhibition, and decreased productivity. Cellular damage can occur either intracellularly or externally at the cell surface from biomolecular reactions with externally-generated reactive transient compounds. The extent of this extracellular damage will depend on the photochemistry of the seawater surrounding the cell. Until recently, nothing was known about the type of photochemical processes, rates, and steady state concentrations of transients in Antarctic waters. Our objective is to determine the dependence of UV-B and UV-A fluxes on photochemical production rates of formaldehyde, hydrogen peroxide, pyruvate, and the OH radical in antarctic coastal waters. We will collect and filter 40 liters of sea water. Aliquots of this water will be placed in quartz tubes and irradiated in a surface water bath each day. Using radiometers and spectral irradiance data available hourly at Palmer Station, we will measure the total daily UV-B and UV-A light fluxes. This experiment will be repeated for 2 - 3 separate 40-liter water samples. Concurrent with this long-term experiment, we will collect, filter, and irradiate coastal sea water daily to assess the variability in surface water photoproduction rates as a function of nitrate and nitrite levels (for the OH radical), DOC concentrations and the optical properties (absorbance and fluorescence) of these waters. Additionally we will collaborate with researchers from the Smithsonian's Environmental Research Center (S-010) to determine action spectra for phytoplankton photoinhibition and photoproduction of reactive oxygen species (the OH radical and hydrogen peroxide) in the same water samples and under the same light conditions. With these data we will be able to construct models of photochemical production rates in surface waters and at various depths and to predict the impact of varying levels of UV-B on the photoproduction and steady-state concentration of several key reactive transient compounds in the upper water column. (S-002)

Impacts of climate change on antarctic vascular plants: Warming and ultraviolet-B radiation. Thomas Day, Arizona State University. Evidence is strong that the climate of the Antarctic Peninsula has changed appreciably in this century. Weather records indicate that mean summer air temperatures have risen more than 10°C over the past 45 years at some peninsula locations. In addition to this warming trend, springtime ozone depletion events have resulted in well-documented increases in ultraviolet-B (UV-B) radiation levels. These rapid changes in regional climate provide a unique opportunity to assess the impacts of climate change on vascular plants.

Although the presence of only two native vascular plant species (Deschampsia antarctica and Colobanthus quitensis) and their sparse distribution in Antarctica attest to the severe conditions for plant survival, there are already indications that climate changes are exerting a strong influence on these species. Regional warming appears to be leading to rapid increases in populations of these species, based on censuses taken along the peninsula. The influence of enhanced UV-B levels on these species is less clear.

An experiment has been initiated in which temperature and UV radiation levels are manipulated around naturally growing Deschampsia and Colobanthus plants on the Antarctic Peninsula to assess their responses to these factors. Assessment involves examining changes in photosynthesis, growth, and reproduction of these plants following warming or exclusion of different UV components.

During the first field season, growth significantly improved under warming treatments. Exclusion of UV did not have any significant effects, although conclusions from this short-term assessment would be premature. Field manipulations will be continued and expanded in the current assessment of plant responses in four key areas: photosynthesis, general thermal adaptations, reproduction, and soils. These areas are critical to understanding plant responses to climate change in Antarctica. (S-003)

Role of antifreeze proteins in freezing avoidance in antarctic fishes: Ecological and organismal physiology, structure-function and mechanism, genetics, and evolution. Arthur DeVries, University of Illinois. Ongoing and new studies of the role of antifreeze glycopeptides (AFGPs) and peptides (AFPs) in freezing avoidance of antarctic fishes in five specific areas constitute this project:

The extent of exogenous and endogenous ice will be determined for McMurdo area fishes, which experience the coldest and most ice-laden waters of the antarctic region. Similar experiments will be conducted for the less severe marine environment of the Antarctic Peninsula. These studies will correlate freezing extremes with circulating levels of AFGPs in the fishes associated with these two environments. (S-005)

Metabolic physiology during embryonic and larval development of antarctic echinoderms. Donal T. Manahan, University of Southern California. Feeding larvae of benthic marine invertebrates in the cold waters of McMurdo Sound are present in the water column for many months before the phytoplankton bloom, but scientists currently do not understand how these feeding larvae survive long periods under starvation conditions. Knowing the physiological mechanisms of this process is important for understanding the ecology of larvae from antarctic regions. For example, the results from recent studies of antarctic echinoderm larvae do not support the suggestion that feeding larvae use other food sources (bacteria or dissolved organic material) to survive this period of negligible phytoplankton abundance. Physiological data, however, suggest a possible survival strategy­potential larval life spans can be extended for about 1 year in the complete absence of food. Such life spans (without food) for feeding larval forms are unique to antarctic larvae. Our research focuses on the metabolism of this process in antarctic echinoderm larvae. We will test the hypothesis that the metabolic cost of development will be lower in antarctic echinoderms than for the same "unit of differentiation" (fertilized egg to feeding larval form) in comparable temperate larvae. Because such data on temperate larvae already exist, our investigation of antarctic larvae will enable us to compare stage-specific developmental metabolism rates. To obtain these metabolic data, we will use a novel technique called "coulometric respirometry," which permits continuous measurements of metabolic rate during development. In addition, we will examine the biochemistry of development to determine the mechanism(s) of low metabolism in antarctic larvae. Using data from these, we will test long-standing hypotheses on cellular mechanisms of low metabolism as these apply to invertebrate development in antarctic environments. The results from our research may also have implications for larvae developing under limited food conditions in other cold environments, such as the deep sea. (S-006)

Ultraviolet photobiology of planktonic development stages of antarctic benthic invertebrates. Deneb Karentz, University of San Francisco. Recently documented global decreases in stratospheric ozone have brought attention to the potential ecological consequences of increased ultraviolet-B (UV-B) radiation in marine communities. Even without ozone depletion, UV-B radiation penetration of ocean surface waters represents a biological hazard to many marine organisms. The most extensive destruction of ozone has been occurring over Antarctica and the southern oceans, where over 50 percent depletion is recorded each spring.

A major obstacle in assessing UV effects is that little is known about the UV photobiology of individual species. In the Antarctic, some of the ecologically dominant benthic invertebrate species occupy intertidal and shallow subtidal depths where researchers have already documented biological effects of UV-B. Because, for many of these species, their planktonic development and spawning season coincide with the period when ozone depletion is occurring, their microscopic embryos and larvae are exposed to increasingly higher levels of UV-B. Presently, no information is available on the potential short- or long-term effects of increased UV-B levels on populations of antarctic benthic invertebrates.

Our research focuses on the UV photobiology of three important antarctic invertebrate species­the limpet Nacella concinna, the sea urchin Sterechinus neumayeri, and the sea star Odontaster validus­which inhabit intertidal and subtidal areas in the region of Palmer Station, Anvers Island, Antarctic Peninsula. The adults of these species are dominant members of antarctic intertidal and shallow subtidal benthic communities, and their embryos and larvae develop for months in surface waters from late austral winter through summer. To evaluate the impact of ambient UV-B on early stages (gametes, embryos, and larvae) in the life histories of these species, we will examine potential UV exposure levels; assess differential sensitivities; identify molecular, chromosomal, and morphological UV-B induced damage; and evaluate potential protection and recovery from UV-B exposure. Because these species have taxonomic equivalents at both temperate and tropical latitudes, our study will provide important biological parameters for increasing scientific knowledge about UV effects on both local and global scales. (S-007)

Polar T3 Syndrome: Metabolic and cognitive manifestations and their hormonal regulation and impact upon performance. H.L. Reed, Kathleen R. Kowalski, Kenneth D. Burman, and John Thomas, H.M. Jackson Foundation for Military Medicine. People who live and work in Antarctica for longer than 4 to 5 months develop a characteristic constellation of symptoms and hormonal changes called the "Polar T3 Syndrome." Earlier researchers have described these people as having a 40 percent increase in energy requirement; frequent mood disorders; doubling of the production, use, and tissue stores of triiodothyronine (T3), the most active thyroid hormone; a decline in central nervous system thyroxine (T4); and acquisition of physiologic cold adaptation.

To improve science's understanding of this syndrome, a team of experienced polar physiologists, endocrinologists, and psychologists will use a multidisciplinary approach to study these apparent discordant and compartmentalized tissue responses over 4 years. The possible cognitive and metabolic changes in performance related to declines in central nervous system T4 and elevations in skeletal muscle T3 content will be studied. Placebo-controlled T4 replacement directed at the central nervous system deficit will be carried out and measured with cognitive instruments.

The team will evaluate T3 content in the cardiovascular system by using submaximal exercise testing to differentiate resting from activity-mediated, energy-use contributions by the skeletal muscles. Additionally, tissue samples of skeletal muscle will provide information regarding the genetic coding for T3 responsive proteins and, thus, will permit more accurate characterization of the thyroid status of these muscles. We will use moderate energy restriction along with T4 supplementation to study the dependence of T3 production, distribution, and tissue stores upon both pituitary generation of thyrotropin and energy intake and will analyze each subject's baseline, determined in the predeployment situation of California and compared with periods and standardized measures obtained during the antarctic summer and winter.

We believe that a correction of the low T4 state in the central nervous system can be managed with T4 supplementation without dramatically changing energy requirements, as suggested by researchers previously conducting human studies using cold-air chamber experiments. If this thesis is correct, characteristic declines in mood and memory during winter seasons in circumpolar regions may be attenuated by T4 supplementation without affecting energy metabolism disadvantageously. Our project also expands information regarding the ultimate regulation and maintenance of the increased T3 production, a central determinant of the Polar T3 Syndrome. (S-008)

Possible linkages between ecosystem measures and the demographics of a Weddell seal population. Donald Siniff, University of Minnesota. The Weddell seal, an important upper-trophic-level species, has been the focus of long-term studies because this species congregates near antarctic support facilities. The most extensive investigations have involved the Weddell seal population near McMurdo Station where research and monitoring efforts began in the early 1960s and have continued to the present. The objectives of our project are

In support of these objectives, we will carry out mark-and-recapture surveys that are necessary to obtain all the estimates required for current capture-recapture models. (S-009)

New approaches to measuring and understanding the effects of ultraviolet radiation on photosynthesis by antarctic phytoplankton. Patrick Neale, Smithsonian Institution. Increases in ultraviolet-B radiation (UV-B, 280-320 nanometers) associated with the antarctic ozone hole have been shown to inhibit the photosynthesis of phytoplankton, but the overall effect on water column production is still a matter of debate and continued investigation. Investigations have also revealed that even at "normal" levels of antarctic stratospheric ozone, UV-B and UV-A (320-400 nanometers) appear to have strong effects on water column production. The role of UV in the ecology of phytoplankton primary production has probably been under appreciated in the past and could be particularly important to the estimation of primary production in the presence of vertical mixing. This research focuses on quantifying UV effects on photosynthesis of antarctic phytoplankton by defining biological weighting functions for UV-inhibition.

New theoretical and experimental approaches will be used to investigate UV responses in both the open waters of the Weddell-Scotia confluence and coastal waters near Palmer Station. In particular, measurements will be made of the kinetics of UV inhibition and recovery on time scales ranging from minutes to days. Variability in biological weighting functions will be calculated for pelagic and coastal phytoplankton in the southern oceans. The results will

The role and regulation of chloride cells in antarctic fish. David Petrel, Creighton University. Antarctic fish have the highest serum osmolarity of any sea water teleost. Maintenance of fluid balance is crucial for survival. Upon warm acclima tion from -1.5 to 4C, the fish lose 20 percent of their serum osmolarity through extrusion of sodium chloride (NaCl) across the gill. NaCl extrusion in fish is primarily performed by chloride-secreting cells located on the gill arches and gill opercula. The driving force for NaCl transport is the sodium/potassium-ATPase. To date, no information is available concerning the role and regulation of the elevated serum osmolarity in antarctic fish. Questions that arise include these:

The chloride cell physiology and regulation in antarctic fish will be compared with a New Zealand fish that is eurythermal. The goals of the proposed research are to determine the plasticity of antarctic and New Zealand fish gill function at the physiological level (through studies of ion transport activity) and molecular level (through studies of the sodium/potassium-ATPase enzyme). Specifically, this research will

The results of this research will, for the first time, describe in detail the underlying mechanism(s) mediating the enhanced hypo-osmoregulation observed in antarctic fish and will allow the comparison of these results to those observed in a eurythermal New Zealand fish. (S-012)

Weddell seal foraging: Behavioral and energetic strategies for hunting beneath the antarctic fast ice. Randall Davis, Texas A&M University at Galveston. To forage efficiently beneath the extensive, unbroken fast ice along the antarctic coast, Weddell seals (Leptonychotes weddellii) have adapted to an environment that is very challenging for an air-breathing predator. These adaptations enable Weddell seals to hunt for prey at depth while holding their breath for 20 minutes or longer. This feat is analogous to a lion or other large terrestrial predator holding its breath while it locates, pursues, and captures prey. In addition, Weddell seals must return to the same hole at the end of a dive or know the location of other breathing holes. Failure to locate a breathing hole will result in a seal's death by drowning.

This study will investigate the behavioral and energetic adaptations that enable Weddell seals to forage in the antarctic fast-ice environment. To achieve this goal, the underwater behavior, locomotor performance (swimming velocity, stroke frequency and amplitude, and three-dimensional movements), and energy metabolism of Weddell seals will be measured during foraging dives. Hypotheses on general foraging strategies, searching behavior, searching mechanics, modes of swimming, metabolic costs of foraging, and foraging efficiency for different environmental conditions and prey type will be tested. Until now, it has not been possible to investigate the foraging behavior of marine mammals in detail. To accomplish this study, a small video system and data logger will be attached to the seals' backs, and oxygen consumption will be measured during voluntary dives from an isolated ice hole in McMurdo Sound, Antarctica.

Observing the foraging behavior and prey of marine mammals is a major means to advance studies of their foraging ecology. The Weddell seal may be the single best species in which to study the foraging behavior and energetics of deep-diving pinnipeds because

Population structure of key antarctic fish and invertebrate resource species. Patrick M Gaffney, University of Delaware. Characterizing the population structure of important antarctic species is essential to an improved understanding of antarctic ecology and the successful management of this ecosystem. The British Antarctic Survey (BAS) has initiated a collaborative international effort (Project Gene Flow) aimed at delineating population structure in several key species (fish, squid, and krill). A 1-month cruise in the Scotia Sea to obtain biological specimens and oceanographic data represents a unique opportunity to apply both established and novel molecular techniques to an important problem in antarctic resource management. Four commercially and/or ecologically important species will be the primary targets of the research: mackerel icefish, Patagonian toothfish, antarctic krill, and the seven star flying squid. A variety of molecular genetic techniques, including some that are well-established and others that are novel but extremely promising, will be applied to delineate genetic population structure in these species. This research will provide information on whether separate "stocks" or genetically different populations of these species exist in antarctic waters. This information will be useful in the management of these species. (S-018)

Long-Term Ecological Research on the antarctic marine ecosystem: An ice dominated environment. Maria Vernet, Scripps Institution of Oceanography; Eileen Hofmann, Old Dominion University; Langdon Quetin and Raymond C. Smith, University of California at Santa Barbara; William R. Fraser, Montana State University; David M. Karl, University of Hawaii. The central hypothesis of the Palmer Long-Term Ecological Research (LTER) project is that the annual advance and retreat of sea ice is a major physical determinant of spatial and temporal changes in the structure and function of the antarctic marine ecosystem. Evidence shows that this dynamic variability of sea ice has an important, perhaps major, impact on all levels of the food web, from total annual primary production to breeding success in apex predators. For example, variability in sea ice may affect prey and predators directly (e.g., access to open water or preferred habitats) or indirectly (e.g., food availability, which in turn may be affected by the variability in sea ice). We hypothesize that sea ice is a major factor regulating

The magnitude and timing of sea ice may have different consequences for different key species, and it is still unclear what the ramifications would be for the whole antarctic ecosystem. For example, high levels of survivorship and reproductive success of Adélie penguins appear to depend on high levels of availability of antarctic krill, which in turn appear to be correlated with greater ice coverage. On the other hand, high levels of breeding success of south polar skuas appear to be determined by the availability of antarctic silverfish, which in turn appear to be associated with lesser ice coverage. Thus, the overall objectives of the Palmer LTER project are

A key challenge for the Palmer LTER project is to characterize and understand the link between the different spatial and temporal scales of the various physical and biological components of the antarctic ecosystem. (S-016, S-021, S-028, S-032, S-035, and S-046)

The chemical ecology of shallow-water antarctic marine invertebrates. Bill J. Baker, Florida Institute of Technology. Our research is a continuation of an interdisciplinary approach to chemical ecology. The objectives are to characterize and quantify chemically mediated ecological relationships among antarctic benthic invertebrates. During two field seasons, we will investigate several specific objectives. We will evaluate the chemical defenses in adult antarctic marine invertebrates and also early life history stages. Investigators will evaluate lecithotrophic eggs, embryos, and larvae for bioactivity. This is particularly relevant because many antarctic invertebrates broadcast conspicuous lecithotrophic embryos and larvae, which require 2 to 6 months to develop. Because biologists have observed that colored sponges use their pigments as defensive agents, we will investigate the functional role of this coloring in sponges and in other colored invertebrates. Furthermore, bioactive metabolite concentration and sequestration will be investigated in invertebrates from which researchers have isolated secondary metabolites. Finally, we will continue to work on isolating and characterizing bioactive compounds from invertebrates to evaluate their functional role. Two significant aspects of this research are the use of ecologically relevant bioassays to guide the isolation of the active chemical agents while working on-site at McMurdo Station and, subsequently, the characterization of those metabolites at our home institutions. In summary, our research program will contribute significantly to the understanding of the nature and role of bioactive agents in the ecology of the antarctic marine benthos. (S-022)

Factors regulating population size and colony distribution of Adélie penguins in the Ross Sea. David Ainley, Point Reyes Bird Observatory. As part of this collaborative project, we will investigate the demographic mechanisms responsible for dramatic growth in existing Adélie penguin (Pygoscelis adeliae) colonies and will identify new ones in the Ross Sea region. We will also study the possibility that the growth of these colonies is related to documented climate change in the region by

This will be the first empirical a priori study to consider the geographic structuring of a seabird population. Results will increase scientific understanding of population regulation and patterns of dispersion and of the effects of climate change­mediated through changes in sea-ice cover­on penguin populations. In addition, results will provide a context in which to interpret conflicting data on penguin population trends from existing programs that use Adélie penguins as an indicator species for point source anthropogenic impacts on antarctic resources (e.g., fishery catches, disturbance by tourism). Our 7-year research effort includes intensive field study conducted at three Ross Island penguin colonies. As part of the study, we will quantify reproductive effort and success, food availability (access to food), diet quality, habitat use, and immigration/emigration relative to colony size and environmental conditions (i.e., pack-ice cover). Our methods bring together several well-established techniques that have been successfully but infrequently used in antarctic biology:

Our research builds on the efforts of Landcare Research New Zealand (LCRNZ), which conducted two preliminary field seasons and is independently funded; LCRNZ activities include the testing of new equipment. LCRNZ will continue its efforts and collaborate with us throughout the project. Researchers from the University of California at Santa Cruz, University of Wisconsin, and Avid, Inc., will work with those from H.T. Harvey and Associates and LCRNZ to accomplish project goals. (S-031)

Penguin-krill-ice interactions: The impact of environmental variability on penguin demography. Wayne Trivelpiece, Montana State University. This study will focus on populations of Adélie, gentoo, and chinstrap penguins at Admiralty Bay, King George Island. These populations have exhibited fluctuations in abundance that have been related to long-term changes in environmental conditions, in particular sea-ice coverage and its possible effects on prey (krill) availability.

This research will test the following five hypotheses relating penguin demography to environmental variability via its effect on krill recruitment in the antarctic marine ecosystem.

The Pygoscelis species are the major predators of krill (Euphausia superba) in the Antarctic Peninsula region and are key species used to monitor the potential impacts of fishery activities in this area. To understand the structure and function of the antarctic marine ecosystem thoroughly, it is imperative to determine the impact of environmental variation on the structure and regulation of upper trophic level predators such as the Pygoscelis penguins. (S-040)

McMurdo Dry Valleys: A cold desert ecosystem. Robert A. Wharton, Jr., University of Nevada, Desert Research Institute; Andrew Fountain, U.S. Geological Survey; Diana Freckman, Colorado State University; W. Berry Lyons, University of Alabama; John Priscu, Montana State University. The McMurdo Dry Valleys, located on the western coast of McMurdo Sound, form the largest ice-free area (approximately 4,800 square kilometers) on the antarctic continent. This area was selected as a study site in the National Science Foundation's Long-Term Ecological Research (LTER) program. The dry valleys are among the most extreme deserts in the world­far colder and drier than any of the other LTER sites. The perennially ice-covered lakes, ephemeral streams, and extensive areas of exposed soil within the valleys are subject to low temperatures, limited precipitation, and salt accumulation. The biotic systems in the McMurdo Dry Valleys are composed of only microbial populations, microinvertebrates, mosses, and lichens. Nonetheless, complex trophic interactions and biogeochemical nutrient cycles exist in the lakes, streams, and soils. Solar energy produces glacial melt water in the austral summer, and in turn, this melt water exerts a primary influence on the soils, streams, and lakes by replenishing water and nutrients to these ecosystems. All ecosystems are shaped to varying degrees by climate and material transport, but nowhere is this more apparent than in the McMurdo Dry Valleys. The overall objectives of the McMurdo Dry Valleys LTER are to understand the influence of physical and biological constraints on the structure and function of dry valley ecosystems and to understand the modifying effects of material transport on these ecosystems. These objectives will be accomplished through a program of systematic environmental data collection, long-term experiments, and model development.

During the 1997-1998 field season, the following studies will be conducted in the McMurdo Dry Valleys as part of the LTER project:

Our efforts will focus on integrating the biological processes in and material transport between the lakes, streams, and terrestrial ecosystems in the dry valley landscape. This season, several experiments will focus increased attention on community structure and function within benthic microbial mats of the dry valleys lakes. Because experimental setup and sampling of lake sediments and microbial mats requires scuba diving, an additional goal this season is to evaluate quantitatively the potential impact of diving activities on lake systems. (S-042)

Buoyancy and morphological studies of antarctic notothenioid fishes. Joseph T. Eastman, Ohio University. Notothenioids, antarctic fishes of the perciform suborder Notothenioidei, are the dominant fishes by number and biomass in all inner shelf areas of the southern oceans. An evolutionary novelty-the only known example of a fish species flock-notothenioids, which are derived from a benthic stock lacking swim bladders, have diversified into most water-column habitats. They display a wide scope of organismal diversification in an ecosystem historically underused by non-notothenioid fishes and are a striking example of the nature of antarctic marine biodiversity. The primary objectives of our project, which centers on evaluating organismal diversification in these antarctic fishes, are

We are also interested in elucidating the morphological basis for evolutionary changes in buoyancy and are hopeful that our study will provide insight into how notothenioids diversified to occupy a variety of water-column habitats in the southern oceans. (S-048)

Ecological studies of sea-ice communities in the Ross Sea, Antarctica. David Garrison, University of California at Santa Cruz. Coastal sea ice forms an extensive habitat in the southern oceans. Reports dating from the earliest explorations of Antarctica have described high concentrations of algae associated with sea-ice, suggesting that the ice must be an important site of production and biological activity. The magnitude and importance of ice-based production is difficult to estimate largely because the spatial and temporal distributions of ice communities have been examined in only a few regions, and the processes controlling production and community development in ice are still understood only superficially. This study will examine sea-ice communities in the Ross Sea region of Antarctica in conjunction with studies of ice physics and remote sensing. The specific objectives of the study are