Photochemical and optical properties of antarctic waters in response to changing UV-B fluxes. 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.

Impacts of climate change on antarctic vascular plants: Warming and ultraviolet-B radiation. 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.

Role of antifreeze proteins in freezing avoidance in antarctic fishes: Ecological and organismal physiology, structure-function and mechanism, genetics, and evolution. 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 relationship of the severity of environment and association of ice in fish,
• the uptake of endogenous ice and its fate,
• structure-function of antifreeze proteins includ-ing the molecular mechanism of AP adsorption and inhibition of ice growth,
• structures and organizations of AP genes and gene families and their relationship to protein characteristics and gene evolution, and
• tissue specificity of AFGP expression.

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.

Metabolic physiology during embryonic and larval development of antarctic echinoderms. 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.

Ultraviolet photobiology of planktonic development stages of antarctic benthic invertebrates. 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.

Polar T³ Syndrome: Metabolic and cognitive manifestations and their hormonal regulation and impact upon performance. 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.

Possible linkages between ecosystem measures and the demographics of a Weddell seal population. 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

• to continue the long-term tagging studies by completing the fieldwork necessary to tag all pups born into the McMurdo Sound population and to replace tags on previously tagged individuals so they will not be lost from the tagged population
• to update estimates of population parameters annually and to continue the analyses and tests of hypotheses associated with this database
• to collect blood samples for DNA analysis, in support of anticipated future genetic work
• to attach radio transmitters to adult males to study breeding activity
• to study Weddell seal foraging ecology with scientists from Hubbs Marine Research Institute.

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.

New approaches to measuring and understanding the effects of ultraviolet radiation on photosynthesis by antarctic phytoplankton. 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

• provide absolute estimates of photosynthesis under in situ, as well as under altered, UV irradiance;
• broaden the range of assemblages for which biological weighting functions have been determined; and
• clarify how kinetics of inhibition and recovery should be represented in mixed-layer models.

The role and regulation of chloride cells in antarctic fish. 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:

• What role does the chloride cell play in mediating salt extrusion?
• Which hormones regulate chloride cell activity?

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

• determine the gill extrusion mechanisms underlying the increase in gill sodium/ potassium-ATPase activity upon warm acclima-tion in antarctic fish and
• determine the hormonal regulation of the gill extrusion mechanisms.

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.

Tourism in Antarctica has steadily increased since the late 1960's. Despite rising concern that human activity may adversely affect wildlife populations, studies designed to address this issue have been lacking. Our objectives are to incorporate a human-impact study within the scope of work currently underway at Palmer Station as a part of two ecosystem-level research programs focused on the Marine system (See project S-035). Specifically, we want to test the hypothesis that the variability inherent in the breeding biology of Adelie Penguins is due in part to the terrestrial breeding habitat. Human Activity (tourism and research) will thus be treated as a component in a matrix designed to examine how variability in this habitat affects penguin breeding biology. By coupling these results with those obtained as part of our research focused on the marine system, we expect to obtain the prerequisite data necessary to more clearly understand how human activity may affect wildlife populations relative to the effects imposed by natural variability in other environmental components.

The researchers will travel daily from Palmer Station to the local islands via Zodiac boat to study the breeding biology of Adelie Penguins. Field studies will mainly consist of observations; however, team members will weigh chicks, count eggs laid and hatched, and monitor chick growth.

Torgesen Island will be divided into two sections: one allowing tourist visits and the other not allowing visits. During the tourist season, the researchers will monitor tourist visitation patterns and thus compare penguin breeding behavior and success between colonies visited and those not visited.

(LTER)

S-042W,  S-042P,  S-042L,  S-042M,  S-042Fr,  S-042Fo

The McMurdo Dry Valleys are located on the western coast of McMurdo Sound (77-80'S 162-85'E) and form the largest ice-free area (Approximately 4,800 square kilometers) on the antarctic continent. This area was recently selected as a study site within the National Science Foundation's Long-Term Ecological Research (LTER) program. The dry valleys are among the most extreme deserts in the world, far 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 biological 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 meltwater in the austral summer, and in turn, this meltwater 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 on these ecosystems. These objectives will be accomplished through a program of systematic environmental data collection, long-term experiments, and model development.

During the 1996-1997 field season, the following studies will be conducted within the McMurdo Dry valleys as part of the LTER project:

• glacier mass balance, melt, and energy balance
• chemistry of streams, lakes, and glaciers
• flow, sediment transport and productivity of streams
• lake pelagic and benthic productivity--microbial foodwebs
• soil productivity
• aeolian transport processes
• meteorological data collection

Efforts will focus on the integration of the biological processes within and material transport between the lakes, streams, and terrestrial ecosystems in the dry valley landscape. This season,. several experiments will focus on increased attention on community structure and function within benthic microbial mats of the dry valley lakes. Experimental setup and sampling of lake sediments and microbial mats requires SCUBA diving, and an additional goal this season is to quantitatively evaluate the potential impact of diving activities on lake systems.

(LTER)

The McMurdo Dry Valleys LTER field team (composed of six subgroups listed below) will base operations at the Lake Hoare camp from October 1996 through late January 1997. The team members will collect samples and conduct experiments on the glaciers, streams, soils, and lakes in the Taylor Valley. They will travel via helicopter to study within the Dry Valleys, as well as to and from McMurdo Station for CSEC (Crary Science and Engineering Center) work. At the CSEC, team members will use cold rooms and freezer space for sample storage and conduct chemical analysis and biological studies in the laboratories.

The team members will (1) study biogeochemistry of benthic mats in Taylor Valley lakes using SCUBA diving. (2) maintain and upgrade meteorological stations and submerged environmental stations within Taylor and Wright Valleys, and (3) depoly a meteorological station at Lake Vida.

The team members will measure the biological, chemical, and physical properties of Dry Valley lakes, with special emphasis on parameters relevant to modeling the Taylor Valley ecosystem. Lake ice cores will be recovered this season from the Dry Valley lakes for ice biota and physical and chemical properties of the ice. Analysis within the CSEC will include radiotrace investigations into biochemical pathways of lake microbiota.

The team members will operate a stream gauging network, study ecology of the Von Guerrard Stream and the relict channel, and study microzooplankton in the Dry Valley lakes. Water samples will be processed in the CSEC and shipped to the home institution for further analysis.

The team members will monitor the inorganic geochemistry of waters collected from the glaciers, streams, and Dry Valley lakes. They will collect snow and ice samples from the glaciers in the Taylor Valley: Taylor, Suess, Huges, and Rhone Glaciers. These samples will be used for chemical and isotopic analysis to characterize sources of melt water to the streams and lakes in the Taylor Valley. They will also collect lake water samples for determination of dissolved CO2. The researchers will continue to work with the other co-PIs involved with the LTER lake and stream sampling program in the Taylor Valley. Team members will conduct chemical analysis at the CSEC and send samples to the home institutions for further studies.

The Soil ecology group of the LTER will continue a a long-term experiment that was established in 1993-1994, This will involve the sampling and retreating of the two soil warming plots for nematodes on the south shores of Lake Joare, which are examining the response of soil biota to soil warming, energy (one experimnent using sucrose and mannitol additions, one using additions of algae from the nearby lake), and water supplimentation. Soil temperatures will be monitored at all LTER sites with data loggers, and soil samples will be returned to McMurdo Station for soil analysis and biotic extractions. Some soil samples will be set up in growth chambers at the CSEC for experimental manipulation throughout the season.

The team members will measure the mass balance of the glaciers in the Taylor Valley. They will make measurements and calculatons of the evaporation/ sublimation and meltwater flux of the glaciers. They will also use GPS to measure the movement of the glaciers. Safety guids will assist team members on the glacier work.