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Antarctic Biology and Medicine
Antarctica is a place like no other: as an intriguing habitat, a scientist's dream; a land where water is scarce truly a desert despite containing more than two-thirds of the world's freshwater supply trapped in the ice. Though it borders the world's major oceans, the Southern Ocean system is unique in the world, a sea where average temperatures don't reach 2ºC in summer, where even the water itself is so unique that it can be identified thousands of miles away in currents that originated here. As the Earth makes its elliptical journey around the sun each year tilted on its rotational axis the sun "sets" in April, not to be seen again until September. And the ice unimaginable, incomparable vastness of ice in a dozen different varieties, at times and in places several thousand meters thick, two major ice sheets (the East larger than most countries), changing dynamically all the time.
Adaptations and behavior developed in response to these extreme conditions provide insight into the intricacies (as well as the fundamental processes) of evolution. These extremes have also driven the development of ecosystems simple enough to reveal wonderfully clear pieces of the web of life on Earth. Support is focused on the following areas:
Marine ecosystem dynamics: Among the research topics are understanding the natural variability of marine ecosystems; correlating the structure and function of the marginal ice-zone ecosystem with oceanic and atmospheric processes; exploring the sources of nutrition and their influence on prey and on primary production; and the role of marine phytoplankton in carbon dioxide cycling.
Terrestrial and limnetic ecosystems: Organisms in ice-free areas and in perennially ice-covered lakes show remarkable adaptations to extreme environments. Relatively few species thrive here, which facilitates the study of ecosystem dynamics and the interpretation of experiments, although much more remains to be learned about adaptive mechanisms and evolutionary processes.
Population biology and physiological ecology: At the next level, looking at relationships among organisms, studies have focused on the variability and dynamics of populations of krill and other zooplankton; ecological relationships among and between fish species, marine mammals, and birds have also been the object of much research, with many issues still to be further explored. As organized programs of antarctic science enter their fifth decade (some even longer), data sets and ongoing observations are elucidating manmade as well as natural changes.
Adaptation: Antarctic extremes present a fundamental research opportunity; topics include low-temperature photosynthesis and respiration, enzymatic adaptations and adaptive physiology such as the development in fish of antifreeze compounds and modifications to the circulatory system in seals; also continuing interest in the response of (and impacts upon) organisms to increased UV-B radiation from the ozone hole.
Human behavior and medical research: Antarctica's extreme climate and terrain impose a quite spartan and unconventional existence upon scientists and others who live and work there. As people are subjected to social, psychological, and physiological stresses (exacerbated during the winter isolation) research opportunities arise. Studies focus on epidemiology, thermal regulation, immune system function, individual behavior, and group dynamics.
Life in Extreme Environments (LEXEN): Biology and ecology of South
Pole snow microbes.
Scientists have always portrayed Antarctica's interior ice sheets as a region extremely hostile to life. As arid as the world's severest desert, the heart of the continent has no water (H2O as a liquid), relentlessly low temperatures and long periods with minimal solar energy (darkness) all conditions that undermine the viability of indigenous organisms. Move toward the fringes of the continent where these conditions moderate somewhat, and this picture begins to change, with numerous species of plants, protozoa, and bacteria.
In snow samples collected in January 1997 near the Amundsen-Scott South Pole Station, however, scientists have found microbes that contain two of the basics of biological life: DNA and pigments that result from photosynthesis. The snow was flown immediately to the Crary Laboratory at McMurdo Station, melted and examined by epifluorescent microscope. Based on their shape and fluorescence signatures, the particles appear to be cyanobacteria. Subsequent analysis using fluorescent DNA stains and scanning electron microscopy confirmed the presence of DNA-containing microbes with this same shape.
Formerly known as blue-green algae, cyanobacteria are now considered to be Monera: Ancient, often unicellular organisms that lack cell nuclei but which are basic to the carbon and nitrogen cycles, as many of them have photosynthetic properties.
Are these microbes indigenous to the antarctic interior? What can be learned about their biology and ecology? These questions will drive this research project, since the discovery of organisms capable of surviving in Antarctica's interior should provide us with new insight into how life forms can adapt to conditions previously believed incapable of supporting life. The biomolecules and metabolism of these creatures must be unique, and could prove valuable for molecular engineering research. (BO-004-O)
Role of antifreeze proteins in freezing avoidance in antarctic fishes:
Ecological and organismal physiology, structure-function and mechanism,
genetics, and evolution.
Despite temperatures that can dip below 0ºC, antarctic waters provide a life-sustaining environment for a number of fishes. Thus a basic question: Why don't these fish freeze when they take this water in through their gills? One primary reason seems to be the presence of biological molecules that work like antifreeze in an engine, so-called antifreeze glycopeptides (AFGPs) and antifreeze peptides (AFPs). By devising experiments that distinguish a number of factors, this project probes some interesting questions about how these fishes may have developed such systems.
How much ice and as an adaptative response, how much "antifreeze" is found in fish from more and less severe environments? Researchers will examine how much exogenous (imported into the body) and endogenous (manufactured inside the body) ice is found in fishes from two distinct environments. The McMurdo area fishes live in the coldest and most ice-laden waters of the antarctic region, while those living near the Antarctic Peninsula face a less severe marine environment. Studies will correlate the freezing extremes and compare the circulating levels of AFGPs in the fishes found in these two environments.
Other ongoing and new experiments will look for answers to a number of interesting and related questions: How does the fish organism respond to ice created inside the body? The antifreeze proteins: How do they function, what is their structure, how do their molecules actually adhere to the potential ice to inhibit its growth? What about the genes that code for these proteins: What is their structure; how are they organized; how might they have evolved? In what tissues in the fish's body is the AFGP gene expressed? (BO-005-M)
Use of a long-term database and molecular genetic techniques to examine
the behavioral ecology and dynamics of Weddell seal (Leptonychotes weddellii)
The Weddell seal (Leptonychotes weddellii) is found in regions of pack ice or fast ice close to the antarctic continent. These seals are relatively long-lived, and the waters of McMurdo Sound have provided a continuous environment in which to study their survival and aquatic reproductive patterns. A series of long-term population studies, ongoing since the mid-1960s, have generated a rare and valuable set of data.
Recently developed molecular biology techniques, however, permit scientists to examine the DNA of individual seals as well as groups, and to gain insight into their genetic histories, breeding systems and reproductive fitness. Breeding males behave characteristically; looking at this behavioral ecology and their mating systems through the lens of their DNA can project backwards in time and correlate their reproductive success and the effective size of their populations.
Using and building on the long-term data set, the study will also examine how hypotheses can be tested and parameters can be estimated, in producing models and studies of population demographics. The population dynamics of the Weddell seal will also be explored though the lens of immigration and emigration into and out of the group.
As the southernmost breeding mammal in the world, the Weddell seal exemplifies the ability to adapt to environmental extremes. Understanding the mating strategies these seals employ should contribute to a deeper understanding of the evolution and population dynamics of the Pinnipedia (a suborder of aquatic, carnivorous mammals, including all the seals and walruses), as well as how marine mammals (more generally) compete. (BO-009-O)
Weddell seal foraging: Behavioral and energetic strategies for hunting
beneath the antarctic fast ice.
Weddell seals, as carnivorous mammals, hunt underwater but breathe air. To thrive in their aquatic environment, they have developed some remarkable adaptations. Foraging efficiently deep beneath the extensive, unbroken fast-ice along the antarctic coast requires that they hold their breath for 20 minutes or longer (a feat comparable to a lion or other large terrestrial predator holding its breath while it locates, pursues, and captures its prey). Then at the end of a dive, to avoid drowning, the seals must either return to the same hole or know the location of other breathing holes.
What enables Weddell seals to live this remarkable life? Until now, detailed investigation of the foraging behavior of marine mammals has not been feasible. Working from an isolated ice hole in McMurdo Sound, Antarctica, this study will employ a small video system and data logger (attached to the seals' backs) to analyze their behavior and measure their consumption of oxygen during voluntary dives. We will measure the underwater behavior, locomotor performance (swimming velocity, stroke frequency and amplitude, and three-dimensional movements), and energy metabolism of Weddell seals during their foraging dives. We will test hypotheses on: General foraging strategies; the general behavior of "searching," as well as the mechanics; modes of swimming; the metabolic price of foraging; and how foraging efficiency varies, under different environmental conditions, and in pursuit of different types of prey.
Effective inquiry into foraging ecology in marine mammals requires these sorts of pioneering studies, focused on type of prey, energetics, and foraging behavior. Of all of the deep-diving Pinnipedae (other species of seal and also of walruses), the Weddell seal may provide the best opportunity to advance knowledge of foraging ecology; because: We have data on their diving ability; the isolated-ice-hole protocol in McMurdo Sound enables recorders to be attached and recovered reliably; and, when placed in the isolated ice hole, the seals make daily foraging dives. (BO-017-O)
The chemical ecology of shallow-water marine macroalgae and invertebrates
on the Antarctic Peninsula.
In a number of plant species, evolution has adapted the basic strategy of developing chemical substances designed to defend the organism. One general group of these substances are classified as defensive secondary metabolites. This project will probe three "cost/benefit" ideas that are often woven into viable theories on the evolution of chemical defenses.
First, the Resource Availability Model of chemical defense. The proposed research will examine whether macroalgae grown under carbon limitation (reduced light) will produce quantitatively higher levels of defensive compounds than will those grown in an optimal light environment; also whether antarctic macroalgae found in the nutrient-rich peninsula region are likely to develop chemical defenses that include nitrogen compounds.
Second, the Optimal Defense Theory in macroalgae and invertebrates. The proposed research will determine the extent to which chemical defenses are more abundant in tissues with a high energy content, such as reproductive tissue and offspring (larvae); also whether larvae relying on lecithin for nutrition have a higher incidence of chemical defense than do larvae relying on plankton.
Finally, using previous work in the Ross Sea as a starting point, the investigation will map how chemical defenses may vary across different areas; if they do vary, we will seek out possible underlying evolutionary factors.
The program should advance our understanding of the evolution of chemical defenses in general, as well as the nature and role of bioactive agents in the specific ecology of antarctic marine benthos (organisms living at the bottom of, or in very deep, marine environments). (BO-022-O)
The biogeochemistry of dimethylsulfide (DMS) and related compounds
in a chemically stratified antarctic lake.
The Earth's atmospheric cycle involves continuous transport of basic elements, one of which is sulfur. Dimethylsulfide (DMS) is the dominant volatile sulfur compound emitted from the ocean and may represent up to 90 percent of the sea-to-air biogenic sulfur flux. When these volatile sulfur molecules oxidize in the atmosphere, condensation nuclei can be released which, scientists hypothesize, may directly counteract the warming effects of anthropogenically produced CO2. Aquatic systems in particular the waters of the south polar regions thus play a crucial role in one of the planet's basic transactions. Yet both the sources and the sinks of DMS and associated sulfonium compounds have yet to be fully identified and understood.
This research will examine the biogeochemistry of water column and sedimentary DMS/DMSP (dimethylsulfoniopropionate), and the role of associated compounds (e.g., dimethylsulfoxide, dimethylated polysulfides) in Lake Bonney. A relatively simple aquatic system, Lake Bonney provides a highly tractable environment for investigating the microbially mediated cycling of biogenic sulfur because there is no turbulence, no grazers and little atmospheric exchange.
Preliminary data suggest that maximum levels of DMS precursors may be found in the deep-chlorophyll layer of the lake, a zone dominated by cryptophyte algae. In addition, DMS concentrations deep in the lake, where there is very little light (i.e., in the aphotic waters), are among the highest recorded in a natural aquatic system. These observations indicate that precursors produced by trophogenic zone phytoplankton sink to the aphotic waters and sediments, where microbes decompose them to DMS and other sulfur compounds. The proposed research will define the sources and sinks of DMS and associated compounds, and establish how they function in the overall ecosystem. We hope to develop a model describing the biogeochemical transformations of organo-sulfur compounds in Lake Bonney. (BO-025-O)
Factors regulating population size and colony distribution of Adιlie
penguins in the Ross Sea.
Over the past few decades, the Adιlie penguin (Pygoscelis adeliae) colonies in the Ross Sea region have grown dramatically in size. What demographic mechanisms might account for this change? This collaborative project will investigate (in particular) the possible effects of documented changes in the region's climate. We will look at the nesting habitat as a function of access to food, and hope to distinguish the relative importance of the key resources that constrain the growth of colonies. A number of behavioral and demographic mechanisms may influence a colony's growth, relative to its initial size and distribution pattern for example, a phenomenon known as philopatry: The interrelationship between the balance achieved by immigration/emigration and consequent breeding effort and success.
As the first empirical study to consider the geographic structuring of a seabird population, we expect our results to increase understanding of how populations regulate themselves, and the patterns they follow when they disperse. We also hope to elucidate the effects of climate change, mediated through changes in sea-ice cover, on penguin populations. The results should also provide a context in which to interpret conflicting data on penguin population trends from existing programs; in particular, Adιlie penguins have been studied as an indicator of such anthropogenic impacts on antarctic resources as fishery catches and disturbances created by tourism.
Our 5 years of research include intensive field study of three Ross Island penguin colonies. We 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). We employ several well-established techniques that have been successfully (but infrequently) used in antarctic biological research:
Aerial photography: to evaluate the availability of nesting habitat,
Microwave images of sea-ice concentration: to assess availability of feeding habitat,
Analysis of stable isotopes: to evaluate food quality,
Radio telemetry: to assess overlap in colony feeding areas, and
Automatic systems: to log aspects of reproductive effort.
Landcare Research New Zealand (LCRNZ) has conducted two preliminary field seasons, including the testing of new equipment. This project will build on their results, and they will collaborate with us throughout the lifetime of the project. The LCRNZ work is independently funded. Researchers from the University of California-Santa Cruz, the University of Wisconsin, and Beigel Technology, will collaborate with those from H.T. Harvey and Associates and LCRNZ to accomplish the project's goals. (BO-031-O)
Penguin/krill/ice interactions: The impact of environmental variability
on penguin demography.
As the environment fluctuates, there are direct effects on the structure and function of antarctic marine ecosystems. Three examples are the Adιlie, gentoo, and chinstrap penguins of the antarctic, whose changing numbers have been related to long-term changes in environmental conditions, in particular the possible effects of sea-ice coverage on the availability of prey (krill). We will explore the demographics of colonies of those three species living in Admiralty Bay, King George Island, to test five hypotheses:
The structure of the krill population is strongly affected by the extent of pack- ice, and its consequent impact on female fecundity and the survival of larvae.
Recruitment of penguins to their respective populations is affected by the extent of pack-ice cover during the winter prior to the breeding season.
The survival of penguin fledglings is correlated to the extent of pack ice cover during the winter following the breeding season.
Adιlie penguins return to the pack-ice habitat during their first two-week-long foraging trips following clutch competition to recover from prolonged fasting of the courtship period.
Accessible pack ice in the early breeding season has led to the evolution of discrete population centers of Adιlies from the Bellingshausen, Weddell, and Ross Sea populations.
The Pygoscelis species of penguins are the major upper trophic level predators of krill (Euphausia superba) in the Antarctic Peninsula region. In trying to assess the potential impacts of fishery activities in this area, it is imperative to first determine the distinct impact of a changing environment. (BO-040-O)
Microbial mediation of trace metal cycling in four stratified antarctic
Aquatic environments often stratify; that is, boundaries at different depths indicate changes in the composition of the water. One of the basic processes in nature is reduction by oxidation (redox), and redox boundaries can be found at specific water depths where microbes are implicated in the cycle and fate of a large suite of chemical elements.
The proposed research will examine the role of microbial influences on metal cycling in four stratified lakes in the McMurdo Dry Valleys: Lakes Fryxell, Hoare, Joyce and Miers. These lakes are characterized by unusually stable redox transition zones, and are also especially amenable to a finely spaced sampling regime. Collectively, they represent a broad range of water chemistries.
The proposed research will test two hypotheses:
In stratified water columns there should be a clear spatial difference between the onset of manganese reduction and the onset of iron reduction. Heavy metals and rare-earth elements will be seen to undergo co-cycling with manganese (Ma) rather than with iron.
In all four lakes, Ma reduction will be associated with the presence of carnobacteria or other Ma-reducing organisms.
Dissolved and particulate metal profiles will be examined at depths from the ice-water interface at the top all the way down to the sediments. Profiles will be correlated with microbial Ma-reduction assays, and with the presence of Ma reducers; these can be detected by screening with Mn-oxide overlay agar plates and nucleic acid hybridizations that function as probes for known manganese reducers. The research will include significant involvement of undergraduates. (BO-041-O)
Shell morphogenesis in giant agglutinated foraminifera.
A dominant member of the cold, deep-sea sediments ecosystem is a group of giant protozoa, the agglutinated foraminifera, also known as forams. For protection, these single-celled organisms encase themselves in architecturally elegant shells that they construct by collecting, sorting, and cementing together sediment grains. The unique occurrence of these giant cells (greater than 1 millimeter in size) in the shallow waters of McMurdo Sound, Antarctica, allows for the study of the cellular and molecular aspects of shell construction.
In our project, we will use novel light-microscopic methods to examine how agglutinated forams secrete and sculpt the adhesive matrix that binds sediment particulate in their shells. Comparative time-lapse photography of different foram species constructing shells will identify key steps in the processes that lead to the various shell morphologies. Peptide sequence analyses of the elastic proteins of the shells will provide valuable insight into the chemical nature of foram bioadhesives. From a practical standpoint, these cements may have important biotechnological and medical applications.
We will also continue a study of the effects of collection activities, as well as natural physical disturbances, in this unique environment. The interdisciplinary research conducted for this project has implications for a number of fields, including cellular development, evolution, paleontology, marine products chemistry, and ecosystem management. (BO-043-O)
Microbial life within the extreme environment posed by permanent antarctic
How does microbial life adapt to environmental extremes, such as those found in Antarctica? One strategy is by association with sediment aggregates, sites where physical, chemical, and biological interactions promote microbial growth under extreme conditions inherent to the ice environment. The 3-to-20-meter-thick permanent ice covers on the lakes of the McMurdo Dry Valleys, Antarctica, contain viable microbial cells in association with just such sediment aggregates. Specifically, certain ice aggregates (within the permanent ice covers on the lakes in the Taylor Valley) have been tentatively characterized in previous studies.
This interdisciplinary research program will use this background and context to explore specific processes that allow for:
the creation of liquid water (the essential element for life) in the permanent ice,
the survival and structuring of microbial populations subjected to freezing and thawing,
the production of substances that alter the physical attributes of the ice-crystal habitat, and
the nutrient supply to the microbial populations, which is essential for survival and whch largely determines net microbial growth and the accumulation of biomass.
Research on microbes in permanent ice provides information on the ecology of microbes in ice ecosystems and promises to have biotechnological implications. Furthermore, since water ice has been detected within and beyond our own solar system, these studies could provide insights into the conditions that might support extra- terrestrial life. (BO-044-O)
Influence of seasonal ice cover on pelagic and benthic communities:
Long time-series studies.
The annual expansion and contraction of ice cover in the Southern Ocean the largest seasonal process in the world ocean causes primary biomass production to fluctuate extensively, and has a strong impact on both pelagic (open, upper sea) and benthic (deeper, at the bottom) communities of fauna. This study at Port Foster, Deception Island, will take advantage of a region that has seasonal ice cover and which supports a pelagic and benthic fauna that are representative of the antarctic coastal zone.
The study of the water column and seafloor will be structured as a long time-series, employing long-term, autonomous monitoring and sampling systems that were developed especially for use in Antarctica. We will deploy a bottom-moored, upward-looking acoustic instrument on the seafloor for 12 months to monitor the vertical distribution, abundance, and biomass of acoustically detectable macrozooplankton and micronekton in the water column. Collections will be made over this period using newly developed, vertically profiling pump sampling. Simultaneously, a time-lapse camera system will be moored on the seafloor to monitor the spatial distribution, sizes, and movements of the epibenthic megafauna component of the benthic community.
This deployment of instruments will allow us to focus on the effect of the seasonal sea-ice cycle on the distribution, abundance, and biomass of the macrozooplankton and micronekton in the water column. Similar questions about the deeper-dwelling epibenthic megafauna will focus on distribution, size, abundance, and movements. Results from this study should provide a valuable foundation database to evaluate the pelagic and benthic community responses to seasonal variability in the Southern Ocean. (BO-050-O)
Biodiversity and biogeochemistry of antarctic photosynthetic bacteria.
Environments classified as "cold" (average temperature 52ºC or lower) comprise more than 90% of the earth's biosphere, yet relatively little is known about about the diversity and ecological activities of cold-adapted microorganisms photosynthetic microorganisms, in particular. This research will explore the biodiversity of cold-adapted anoxygenic photosynthetic bacteria that are found in permanently cold antarctic habitats. The research takes a phased approach to biodiversity: Beginning with the enrichment and isolation of cultures of antarctic photosynthetic bacteria; then characterization in the laboratory of their major physiological, biochemical, and genetic features; finally, in situ study of biogeochemical reactions carried out in natural populations of these organisms.
Readily cultivable species of cold-adapted photosynthetic bacteria will be isolated in pure culture. The isolation methods to be used are not the classical ones of liquid enrichment but instead employ extincting dilution this will ensure that rare as well as abundant cultivable species are obtained. Variations in the enrichment approach will be used to isolate those cold-adapted species with particularly well developed and/or specialized metabolisms. Examples are those capable of autotrophic carbon dioxide fixation, nitrogen fixation and the photocatabolism of aromatic compounds. Field research will include isolation of new cultures from stratified antarctic lakes in the McMurdo Dry Valleys. A series of enrichment cultures established at different temperatures and growth rate measurements will yield isolates that possess the ability to grow over a range of temperatures. The Isolates will be phylogenetically characterized by 16s rRNA sequencing. This will permit us to determine which species are merely psychrotrophic (cold-tolerant) and which are actually psychrophilic (cold-loving).
The results of the research should fortify the knowledge of photosynthetic diversity. We anticipate identifying novel organisms for agricultural and biotechnological use, and for the study of photosynthesis and related processes at low temperatures. Finally, we expect to broaden the diversity of known psychrophilic and psychrotrophic prokaryotes, and thus provide more data for the study of exobiology (the study of life beyond the planet). (BO-195-O)
Diving biology of emperor penguins.
Because the emperor penguin (Aptenoidytes forsteri) lives within the pack ice zone of Antarctica, its advanced ability to dive has been the subject of interest for many years. Emperor penguins routinely hunt for food for between 2 and 10 minutes, at depths ranging from 50 to 500 meters. These birds have reached a measured depth of nearly 550 meters. The longest dives are not the deepest, however; the recorded longest of twenty-two minutes was nowhere near that record depth.
This project will examine the diving physiology and behavior of emperor penguins in the Ross Sea region of Antarctica. We hope to elucidate both the physiological and behavioral mechanisms underlying the breath-holding capacity of these diving birds; also to understand how these physiological limits may affect the natural diving behavior and ecology of the penguins; and further, to use the unique adaptation of diving birds to explore how organs and tissue tolerate oxygen deprivation.
The emperor penguin provides an excellent model to investigate the physiology and behavior of diving birds and mammals; in this case, thermoregulation, underwater behavior and the homoeostatic regulation of myoglobin. We will focus on the role of decreased body temperature in extending the duration of aerobic metabolism during diving. The presence of a small camera will permit us to examine their behavior during their dives, and to correlate changes in core and muscle temperature with which prey they ingest as well as with their wing stroke frequency. At the molecular biology level, we will use the high myoglobin concentration in emperors and the large increases in myoglobin concentration during chick development to examine transcriptional control of the myoglobin gene. (BO-197-O)
Ultraviolet-radiation-induced DNA damage in bacterioplankton in the
Strong evidence now shows that ultraviolet (UV) radiation is increasing periodically over certain locations in Antarctica and the Southern Ocean a result of ozone depletion. When ozone concentrations are diluted, the stratosphere is able to adsorb less UV radiation, permitting more of it to reach the Earth's surface. Although research on the impact of increased UV radiation due to ozone depletion has focused primarily on phytoplankton, a smaller effort is being directed to the impacts on other food sources.
During this collaborative project, we will explore the effects of UV radiation upon bacterioplankton. This involves the interactions between bacterioplankton and photochemical processes, as well as interactions with higher trophic groups such as phytoplankton and zooplankton. Several specific parameters will be explored:
whether bacterial phytoplankton-coupling modifies bacterial response to UV radiation,
how seasonal changes in UV radiation affect bacterial community dynamics, and
how chemical photoproducts affect bacterial production.
We hope to elucidate the molecular determinants of changes in productivity, and also the molecular and physiological responses to changing UV radiation. The ultimate benefit would be a greater understanding of the potential impact that changes in UV radiation can have on marine microbial communities. (BO-200-O)
The role of oceanographic features and prey distribution on foraging
energetics and reproductive success.
The Southern Ocean enjoys a high seasonal productivity, in both coastal and pelagic environments. But observations over the last several decades show that behind this general productivity lies much variation during the year, and from year to year. Thus the prey available to vertebrate predators can vary significantly over time, and from place to place.
Since the late 1980s, scientists have recorded this spatial and temporal variability for the northern South Shetland Islands region of the Antarctic Peninsula. The antarctic fur seal [Arctocephalus gazella], a subpolar migratory otariid with a short lactation period, is an increasingly dominant marine predator of the South Shetlands region. Its life-history pattern is characterized by foraging trips alternating with short visits to provide for a single offspring; this pattern allows scientists to measure both maternal investment and the distribution/abundance of prey, on the same temporal and spatial scales.
This project will quantify the foraging costs and maternal investment associated with different strategies observed in populations of South Shetland antarctic fur seals. Using state-of-the-art techniques, we will determine the costs and benefits of different foraging patterns correlated to: Energy expenditure, food intake, dive depth, dive duration, time of day, dive frequency, swim speed, and foraging location. These measurements will coincide with small- and large-scale oceanographic surveys to be conducted by the National Oceanic and Atmospheric Administration's Antarctic Marine Living Resources program, which also contributes to the support of this project.
The research will provide scientists a clearer picture of the life of a free-ranging marine vertebrate predator. The data should reveal patterns linking the biological characteristics of the prey (composition, distribution, and abundance) and the physical characteristics of the foraging environment with foraging success, maternal investment, and reproductive success. (BO-267-O)
Surface UV irradiance and PAR variability over Antarctica.
Since discovery of the antarctic ozone hole in the early 1980s, concerns have grown about whether the consequent increase in ultraviolet (UV) radiation reaching the Earth's surface has a negative impact on the Southern Ocean ecosystem. While subsequent photobiology research has shown there are negative effects on photoplankton, zooplankton and fish larvae from the increased UV radiation, it is difficult to extrapolate localized studies to a broad spatial scale.
One way to extend the results of photobiology point-measurement to large spatial scales is by applying PAR (photosynthetically active radiation) mapping techniques to the UV radiation data gained by satellites. The mapping algorithm developed to date uses specific satellite images of cloud and ozone distribution to estimate UV and PAR irradiance levels over large areas of the Earth's surface. This work is underway, thanks to prior research support; the goal of the current project is to improve performance of the UV and PAR mapping algorithm. Since a significant fraction of overall biological productivity occurs in waters near the coast, we will focus special attention on improving the performance of the mapping technique in those regions.
Simulations made with Monte Carlo radiative transfer models suggest that these coastal regions are subject to significantly greater UV surface irradiance. The field study will deploy a newly modified surface radiometer with spectral sensors; this device optimizes retrieval of cloud optical depth and surface albedo. This superior system should significantly enhance our ability to test the accuracy of PAR, the mapping algorithm.
We will also investigate how the new AVHRR-3A satellite sensor might be used to improve the algorithm. It appears that information from this new sensor could be useful for obtaining more frequent and accurate surface albedo maps, information vital to the mapping algorithm.
We expect the development of these new approaches to interpreting satellite and surface measurements to provide information critical for interpreting the impact of ozone reduction on the biological communities in Antarctica. (BO-279-O)
Planktonic invertebrate larvae and biogeography of Antarctica.
Because continental drift has isolated antarctic ecosystems since the Early Oligocene (about 40 million years ago), most invertebrate fauna commonly found there are native only to that region. Despite this extensive isolation, however, some benthic groups consist of significant proportions of non-native species from 20 to more than 50 percent. To account for such species, scientists have proposed that intermittent reciprocal exchange must occur between populations resident on South America and Antarctica.
One hypothesis is that geographical distribution could be maintained and genetic exchange accomplished through the passive dispersal of planktonic larvae. This project is targeted at this hypothesis; our objective is to show that this dispersal actually occurs. We must demonstrate two facts:
larvae of sublittoral species actually can be found across the Drake Passage; further, that these do belong to species that can be found in south american and antarctic faunas, and
a hydrographic mechanism exists that can explain how passive transport of larvae occurs between the two continents.
To address these two requirements we will make transects of plankton samples across the Drake Passage and examine the possibility of cross-frontal exchange of larvae at the subantarctic and polar fronts of the Antarctic Circumpolar Current; we will also explore the possible transport of larvae in mesoscale rings. Our results should demonstrate that other species may be profitably examined using molecular techniques that compare individuals from bottom populations of South America and Antarctica. (BO-281-O)
McMurdo Station biology course; Integrative biology and adaptation
of antarctic marine organisms.
This international, advanced-level, graduate training course will be organized and taught in Antarctica for one month during the austral summer of 1999-2000. The course introduces students to the diversity of biological organisms in antarctic regions, and allows them to study unique aspects of biology that permit life in such extreme environments.
Long-standing questions in evolution and ecology (such as cold adaptation and food limitation) about the biology of antarctic organisms are examined through physiological experiments with organisms, studies of isolated cells and tissues, experiments on protein structure and function, and molecular analysis of genetics systems. Lectures emphasize physiological, biochemical, and molecular biological approaches to understanding the ecology and biological adaptations of antarctic organisms.
Student research projects follow these interwoven themes. The students should gain a rigorous understanding of the power as well as the limitations of physiological, biochemical, and molecular biological methods that are currently being used to answer research questions in environmental science and the biology of adaptation.
The course will be held in the Crary Science and Engineering Center at McMurdo Station, Antarctica. This modern research facility provides state-of-the-art laboratory facilities a short distance from the marine and freshwater environments where biological observations are made and material is collected. The course will be taught in four modules:
Biological diversity of antarctic organisms: Evolution and molecular phylogeny;
Ultraviolet radiation: Effects on antarctic organisms;
Invertebrates: Physiology, energy metabolism, and development; and
Fish: Biochemical adaptations.
By attracting an extremely competitive group of young scientists, this course introduces new researchers to Antarctica and teaches students the modern research methods currently being deployed to study mechanisms that are unique to biology in Antarctica. (BO-301-O)
Bentho-pelagic coupling on the west Antarctic Peninsula shelf: The
impact and fate of bloom material at the seafloor.
Primary production in antarctic coastal waters is highly seasonal; each spring/summer, an intense pulse of biogenic particles is delivered to the floor of the continental shelf. This seasonal pulse may have major ramifications for carbon cycling, benthic (seafloor) ecology and the nature of material buried on the west Antarctic Peninsula (WAP) shelf. This project brings several disciplines together in an effort to evaluate the bloom material its fate, accumulation on the seafloor, and impact on the benthic community.
We will work along a transect of three stations crossing the antarctic shelf in the Palmer Long Term Ecological Research study area. During five cruises throughout the 1999-2000 research season, we will test the following hypotheses:
A substantial proportion of spring/summer export production is deposited on the WAP shelf as phytodetritus or fecal pellets.
The deposited bloom production is a source of labile particulate organic carbon (POC) for bottom-dwelling organisms (benthos) for an extended period of time (i.e., months).
Large amounts of labile bloom POC are rapidly subducted into the sediment column by the deposit-feeding and caching activities of benthos.
Macrobenthic detritivores undergo rapid increase in numbers and biomass following the spring/summer POC pulse.
To test these hypotheses, we will evaluate seabed deposition and POC lability, patterns of POC mixing into sediments, seasonal variations in macrofaunal and megafaunal abundance, biomass and reproductive condition, and rates of POC and silica mineralization and accumulation in the seabed. We will contrast the fluxes of biogenic materials and radionuclides (into midwater particle traps) with seabed deposition and burial rates; this data should permit us to establish water-column and seabed preservation efficiencies for these materials.
A better understanding of the spring/ summer production pulse on the WAP shelf should enhance our understanding of the impact of such fluctuations on seafloor communities, as well as carbon cycling in Antarctic coastal systems. (BO-303-O and BO-313-O)
Control of denitrification in a permanently ice-covered antarctic
lake: Potential for a regulation by bioactive metals.
Denitrification driven by bacteria is the process by which nitrogen is lost from ecosystems, and thus its rate and regulation may directly affect both primary biological production and carbon cycling, over both short and long time scales. This research investigates a natural experimental system to be found in permanently ice-covered Lake Bonney in the Taylor Valley of East Antarctica to ask: What is the role of bioactive metals in regulating denitrification?
Lake Bonney has two distinct lobes, but in only one does denitrification occur. Previous study has ruled out most of the obvious biological and chemical variables which usually influence denitrification that might account for the difference between the two lobes. Denitrifiying bacteria are present in both lobes of the lake, where tests of both temperature and salinity reveal conditions they can thrive. Thus a paradox presents itself: Despite apparently favorable conditions, what is inhibiting denitrification in one lobe and not the other?
Our study entails a combination of culture experiments and field work to examine this paradox:
experimenting with the denitrifying isolates to determine metal tolerances and requirements for growth,
measuring metal concentrations and metal speciation in surface transects and depth profiles, and
probing how denitrifying bacteria respond to alterations in the availability of certain metals.
By elucidating the relationship between microbial activity and metal distributions in Lake Bonney, we hope to add to scientific knowledge about the cycling of elements in other aquatic systems. We also expect to develop insights useful for evaluating the proposed use of paleo-denitrification indicators for past climate-reconstructions. Finally this research may shed light on the potential significance of the global marine denitrification/nitrogen fixation ratio to atmospheric carbon dioxide levels. (BO-310-O)
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