Osmund Holm-Hansen - US grants

The flux of ultraviolet-B radiation (UV-B, 280-320 nm) at sea level in the Antarctic may be increasing due to decreases in stratospheric ozone levels. Previous studies have shown that marine phytoplankton in the upper portion of the water column are inhibited by natural UV radiation, and hence further progressive increases in the flux of UV may have damaging effects on the food web in Antarctic waters. Holm-Hansen proposes to measure the flux of natural UV in the euphotic zone with a multi-channel spectral radiometer and document its effect(s) on marine phytoplankton. Analysis of absorption by particulate and dissolved components will enable assessment of the role of phytoplankton and detrital pigments in the attenuation of UV radiation. Marine in situ studies will examine both short-term effects of UV based on rates of radiocarbon incorporation and long-term effects based on phytoplankton growth rates. In addition to marine in situ studies, controlled experiments using artificial light sources will be conducted to evaluate the effect of known UV doses on isolated phytoplankton cultures as well as the differential sensitivities of species in natural water samples. Photoadaptational responses involving synthesis of UV absorbing pigments and their role in protection and/or photosynthesis will be analyzed using HPLC, and particulate absorption and fluorescence spectroscopy. These studies of the dynamic response of phytoplankton to increasing dose-levels of UV will be important for understanding the biological consequences of reduced ozone/enhanced UV-B levels in the Antarctic and, through modeling efforts, will be of value in predicting UV effects elsewhere in the world's oceans.

Historical data and observations from studies of the coastal Antarctic Peninsula region provide detailed documentation of massive phytoplankton blooms which develop within the Gerlache Strait and the southwest portion of the Bransfield Strait. Hydrographic data indicate that the flow field is relatively quiescent in the region of bloom formation. The objectives of the proposed work are to understand the temporal detail regarding the mechanisms leading to formation and decline of these blooms. This component of the RACER (Research on Antarctic Coastal Ecosystem Rates) program will utilize an interdisciplinary approach to resolve the phytoplankton response to physical forcing. The emphasis will be on high temporal resolution of meteorological forcing of turbulent mixing within the upper water column, and the response of the phytoplankton. This will be accomplished with a permanent meteorological station on an island adjacent to the primary station and rapid profiling of physical- optical-biological properties. Detailed studies of phytoplankton rate processes including carbon and nitrogen isotope uptake studies, growth rates determined by radio-carbon labelling of chlorophyll a, and kinetics of photoadaptation will be carried out. The photoadaptive status of the phytoplankton crop will be determined from optical, biochemical, and photosynthetic parameters. This information is essential for an understanding of the underlying mechanisms of bloom formation. Such an understanding is required for development of mechanistic models which are capable of predicting seasonal progression and interannual variability forced by the physical environment.

This proposal on "Evaluation of Critical Depth Hypothesis for Phytoplankton in Polar Waters" between Dr. Osmund Holm-Hansen of the Institute of Marine Resources, Scripps Institute of Oceanography, University of California at San Diego, and Dr. Egil Sakshaug of the Biological Station, University of Trondheim, Norway, is sponsored by NSF. Dr. Holm-Hansen proposes to spend two months primarily analyzing data he and Dr. Sakshaug have acquired in numerous cruises in both polar regions during the past seven years, as well as data both have produced in the laboratory which is essential to interpreting their field data. Their computerized data bases consist of simultaneously acquired information on physical-biological-optical characteristics in vertical profiles in the upper 200 m of the water column. The investigators wish to model the dynamic interaction between growth and physiology of the phytoplankton and the mean irradiance to which the cells are exposed as influenced by vertical mixing processes. They shall interpret data within the general framework of the Critical Depth hypothesis first described by Sverdrup in 1953, expecting that their large data base should provide a more realistic formulation of this concept.

This award supports the participation of Dr. Osmund Holm-Hansen of Scripps Institution of Oceanography and several other U.S. marine scientists in an international workshop on Polar Marine Ecology to be held in Trondheim, Norway. The workshop has been designed specifically to bring together the scientists who were actively involved in the "Norwegian Research Program for Marine Arctic Ecology" (PRO MARE). The convener of the workshop and director of the subject research program is Professor Egil Sakshaug of the University of Trondheim. PRO MARE was an intensive five year ecological study of the Barents Sea sponsored by Norway, which invited many investigators from other countries (primarily the U.S.) to participate in the multidisciplinary research cruises. The emphasis of the research was to quantify the processes affecting food web dynamics, and evaluate how these rates are affected by physical, chemical and optical parameters. The workshop offers an opportunity to discuss and begin to synthesize the broad range of data acquired during PRO MARE into an ecosystem analysis of the Barents Sea, as well as examining their relevance to general polar oceanography. The Barents Sea has some oceanographic features which make it an excellent "model" system to study biological problems which have world wide significance. These include the development and importance of frontal systems for enhanced primary production, the relationship between phytoplankton productivity and depth of vertical mixing as influenced by meteorological conditions, and the biological and physical importance of the melting of the annual sea ice. All six U.S. researchers whose travel will be supported by this grant have had much personal involvement with the PRO MARE program; they will have much to contribute and learn during the multidisciplinary discussions.

Decreased concentrations of ozone in the stratosphere over Antarctica have resulted in increased levels of ultraviolet radiation in the UV-B portion of the spectrum incident at the earth's surface beneath the 'ozone hole'. There is now world-wide concern that this enhanced flux of UV radiation may cause serious harm to the marine ecosystem in the Southern Ocean. This project, which includes field and laboratory studies, will help to determine the effects of enhanced levels of UV-B radiation on phytoplankton, and to relate such effects to overlying ozone concentrations. UV levels determined from the NSF-Operated UV- Spectroradiometer at Palmer Station will be directly applicable to the interpretation of observed biological effects. Primary attention will be given to the effects of UV-B radiation on photosynthetic rates, on damage to DNA with resulting loss of cell viability, and on the rates and extent to which phytoplankton can minimize cellular UV damage by production of specialized protective pigments. Differential sensitivity to UV-B of dominant phytoplankton species or groups will also be determined, as such differences might have important consequences on the structure of the food web in antarctic waters. As the project's activity will cover the period from September through December, the resulting data set should encompass the period of maximal development of the ozone hole, as well as the time of the summer solstice. This project is important because it will elaborate previous findings and address in detail the extent and the nature of ultraviolet damage to phytoplankton, as well as evaluate the kinds of defenses cells can muster against it.

9321736 Holm-Hansen The effects of increased ultraviolet (UV) irradiance on planktonic ecosystems have been studied in some detail for Antarctic waters but comparable studies have not been carried out at high northern latitudes. Recent evidence has documented a thinning of ozone over Arctic seas, suggesting the potential for similar UV effects in northern waters. In this proposal we will determine the effects of present-day ultraviolet radiation, as well as the potential effects of increased UV irradiance, on phytoplankton and ichthyoplankton in high Arctic latitudes. Studies of Arctic phytoplankton, to be conducted in Norway, will focus on (i) the effects of UV radiation on photosynthetic rates and the effect on overall rates of primary production, (ii) the extent to which cells can decrease their sensitivity of UV radiation by synthesis of UV-absorbing compounds, (iii) species- specific differences in UV resistance, and (iv) DNA repair capacities which are unknown for northern plankton communites. Studies of UV damage to ichthyoplankton have not been conducted at either pole. Recently developed methods allow us to measure the amount of UV induced DNA damage in individual free-living eggs and larvae. The results of these studies, done at temperate latitudes, have shown that the diel cycle of damage and repair, the pre-exposure conditions, and interspecific differences greatly effect the susceptablility to UV damage. The present study will be the first attempt to measure the impact of UV on early life-stages of important polar fisheries species. The proposal brings together the investigators' skills in measuring UV damage together with the unique location, collaborators and technical capabilities of the laboratories in Tromso, Norway.

9503643 Holm-Hansen This U.S.-Argentina Cooperative Science Program award supports travel expenses and some expendable research supplies related to the visits of Drs. O. Holm- Hansen, E. Helbling and V. Villafane, Scripps Institute of Oceanography, La Jolla, CA to Ushuaia, Argentina. The objective of the research is to determine the impact of the UVR on sub-Antarctic plankton and to gain some insight into the possible ecological impact of enhanced UV-B radiation on these organisms. The Argentine counterpart is Dr. L. Orce, CIB, CONICET, Argentina Seasonal ozone concentrations in the stratosphere over Antarctica have been progressively decreasing during September-November of each year for the past decade, with the result that the fluence of the shorter UV-B wavelengths (280-320 nm) is greatly enhanced. The biological impact of this increased ultraviolet radiation (UVR) has been studied intensively in the Antarctic, but little work has been devoted to this problem at lower latitudes, such as the southern regions of South America. Although ozone depletion is greatest at very high latitudes, increased UVR may pose significant problems for plant and animal life in the southern regions of Argentina, due to the ozone hole actually extending over the South American continent, and also to the fact that low-ozone air flows from the Antarctic north over South America. The marine environment at Ushuaia represents a prime locality for studying the biological impact of increased UVR on the marine food chain leading up to harvestable marine resources. These cooperative UVR studies incorporate into one integrated field program the biochemical expertise provided by Dr. Orce and his colleagues in Argentina, with the oceanographic and experimental experience with UVR provided by the U.S. investigators. The studies are specifically designed to assess the effect of increased UVR on the viability and metabolism of marine phytoplankton, with emphasis being p laced on rates of primary production, which constitutes the base of the marine food web. The laboratory and field facilities for such studies are excellent at Ushuaia. An essential component of the work is the availability of recording UV- spectroradiometers and profiling spectroradiometers which can be lowered to a 100m depth, installed by Dr. Orce under an Interamerican Development Bank (IDB)-CONICET grant. ***

9530255 Holm-Hansen This Phase I proposal focuses on the potential biological impacts of increased solar ultraviolet radiation (UVR) on both terrestrial and aquatic ecosystems in the southern regions of Argentina and Chile. During three workshops, this Phase I proposal has as its objective to work with research personnel in Argentina and Chile to develop a framework of cooperation between researchers from these countries and those from the United States in order to plan a research program that will be both scientifically productive and also meaningful to social interests in South America. It is recognized that a meaningful biological study of the UV impacts related to ozone depletion should involve expertise from many disciplines and backgrounds. In particular, it is important to involve expertise related to measurement of ozone and spectral UVR, experimental biologists with expertise in terrestrial and aquatic ecosystems, personnel who are knowledgeable regarding important regional resources that should be investigated in regard to UVR sensitivity, and modeling expertise to integrate the physical-biological data resulting from the field research. This proposal draws upon the scientific and environmental expertise from Argentina, Chile, and the United States to develop a dynamic research program that gives regional concerns a high priority. The research is organized in regions of Argentina and Chile because incident UVR will increase with decreasing latitude, but the maximum change in enhanced UV-B radiation will be at the higher latitudes. The consequences of such opposite trends in incident radiation with changes in latitude will thus impose very different radiation regimes in different regions of Argentina and Chile. The regions mentioned above are different in regard to the terrestrial and aquatic resources which are of importance to the local inhabitants and to the economy of the countries. %%% This Phase I proposal focuses on the potential biological impacts of increased solar ultraviolet radiation (UVR) on both terrestrial and aquatic ecosystems in the southern regions of Argentina and Chile. During three workshops, this Phase I proposal has as its objective to work with research personnel in Argentina and Chile to develop a framework of cooperation between researchers from these countries and those from the United States in order to plan a research program that will be both scientifically productive and also meaningful to social interests in South America. This proposal focuses on the potential significance of increased UV-B radiation in those regions of South America where the impact will be of importance for social interests, which will include agricultural crops, alterations in aquatic primary production with resultant effects of harvestable aquatic resources, and other aspects of the terrestrial ecosystems which may be of importance to the economies of the region. Although Antarctic regions are experiencing the greatest change of solar regimes, the above social concerns are not very relevant to the Antarctic continent. The southern portion of South America, however, with its close proximity to the seasonal ozone hole and its many inhabitants and abundant terrestrial and aquatic resources, would appear to be the area of greatest potential harm by increasing depletion of stratospheric ozone. It is for this reason that this proposal is mainly concerned with the area of Patagonia, but research will also be conducted in tropical areas so as to compare subantarctic and temperate species with tropical species. As the research of this proposal will focus on components of the terrestrial and aquatic ecosystems which represent important economic resources, the findings will have direct relevance to regional and national interests and economies. The incorporation of student education and training and international cooperation will benefit both individuals and the institutional framework of science in various Member States of the IAI participating in this program. This proposal assembles a team of scientists from the following countries: Argentina, Chile, and the United States. These countries are Member States of the IAI, an initiative to stimulate cooperative research on global change issues among the scientific institutions of the Americas. The National Science Foundation is the designated U.S. Government agency to carry our the Unites States responsibilities within the IAI. ***

9907692
Holm-Hansen

Recent data shows that ozone concentrations in the stratosphere over the Northern Hemisphere during the spring period (March-May) are decreasing each succeeding year, continuing the decline that has been documented during the past decade. The magnitude of the depletion in atmospheric ozone is maximal at the higher latitudes in the Arctic, with progressively less depletion at lower latitudes. Depletion of this protective layer of ozone results in enhancing UV-B radiation (280-320 nm), with the influence of these shorter UV wavelengths incident upon the earth increasing exponentially with progressive loss of ozone. As the photons in the UV-B spectral region are highly energetic and their wavelengths overlap the absorption spectrum of many important cellular components (e.g., DNA), this enhanced UV-B radiation resulting from ozone depletion represents a significant threat to any living organism which is exposed to solar radiation. In this proposal we are concerned with the impact of solar UVR on Arctic marine phytoplankton, which constitute the base of the entire food web in the marine ecosystem.

The project will be based at the Marine Biological Station of the University of Tromso, Norway, which is located at approximately 70 N and hence represents a high-latitude Arctic environment, but will also include ship-board studies in the Lofoten Islands and close to the ice edge in the northern Barents Sea. All experimental work will use either natural phytoplankton assemblages or unialgal phytoplankton cultures of ecologically relevant species in the Arctic food web. Both in situ incubations and temperature-controlled incubators with appropriate optical filters will be used to determine the impact of enhanced UV-B radiation (when column ozone values are low), 'normal' UV-B radiation, and UV-A radiation (320-400 nm) on structural damage to the genetic material in cells (DNA), on the loss of primary production, and on possible changes in species composition of the phytoplankton assemblages. Ancillary data will include the relationship between the magnitude of UV-induced cellular damage and the influence and total dose of UVR experienced by cells. Specific experiments will also determine whether or not the UV-induced cellular damage is reversible in time, and also the extent to which cells can mitigate the adverse effects of solar UVR by synthesis of UV-screening compounds. These studies will be supported by simultaneous measurements of relevant environmental factors, including incident spectral UVR and visible solar radiation with depth in the water column, and stability of the upper water column.

The studies will be done in cooperation with personnel from the University of Tromso, who are also engaged in long-term monitoring of incident solar UVR in northern Norway. Students from both the USA and Norway will be active participants in the field work and in analysis of the data. The results from this cooperative project should provide a good data base to better our understanding of the possible impact of enhanced solar UVR on the floristic composition of the natural phytoplankton assemblages as well as on the rate of primary production. Such data will be important inputs to future modeling efforts to estimate the impact of progressive depletion of atmospheric ozone over the Arctic on the food resources available to higher trophic levels. As important fishery resources are located throughout the Arctic regions, such knowledge is also of importance in regard to economic and societal concerns.

The Shackleton Fracture Zone (SFZ) in the Drake Passage defines a boundary between low and high phytoplankton waters. West of Drake Passage, Southern Ocean waters south of the Polar Front and north of the Antarctic continent shelf have very low satellite-derived surface chlorophyll concentrations. Chlorophyll and mesoscale eddy kinetic energy are higher east of SFZ compared to values west of the ridge. In situ data from a 10-year survey of the region as part of the National Marine Fisheries Service's Antarctic Marine Living Resources program confirm the existence of a strong hydrographic and chlorophyll gradient in the region. An interdisciplinary team of scientists hypothesizes that bathymetry, including the 2000 m deep SFZ, influences mesoscale circulation and transport of iron leading to the observed phytoplankton patterns. To address this
hypothesis, the team proposes to examine phytoplankton and bacterial physiological states (including responses to iron enrichment) and structure of the plankton communities from virus to zooplankton, the concentration and distribution of Fe, Mn, and Al, and mesoscale flow patterns near the SFZ. Relationships between iron concentrations and phytoplankton characteristics will be examined in the context of the mesoscale transport of trace nutrients to determine how much of the observed variability in phytoplankton biomass can be attributed to iron supply, and to determine the most important sources of iron to pelagic waters east of the Drake Passage. The goal is to better understand how plankton productivity and community structure in the Southern Ocean are affected by the coupling between bathymetry, mesoscale circulation, and limiting nutrient distributions.
The research program includes rapid surface surveys of chemical, plankton, and hydrographic properties complemented by a mesoscale station grid for vertical profiles, water sampling, and bottle incubation enrichment experiments. Distributions of manganese and aluminum will be determined to help distinguish aeolian, continental shelf and upwelling sources of iron. The physiological state of the phytoplankton will be monitored by active fluorescence methods sensitive to the effects of iron limitation. Mass concentrations of pigment, carbon and nitrogen will be obtained by analysis of filtered samples, cell size distributions by flow cytometry, and species identification by microscopy. Primary production and photosynthesis parameters (absorption, quantum yields, variable fluorescence) will be measured on depth profiles, during surface surveys and on bulk samples from enrichment experiments. Viruses and bacteria will be examined for abundances, and bacterial production will be assessed in terms of whether it is limited by either iron or organic carbon sources. The proposed work will improve our understanding of processes controlling distributions of iron and the response of plankton communities in the Southern Ocean. This proposal also includes an outreach component comprised of Research Experiences for Undergraduates (REU), Teachers Experiencing the Antarctic and Arctic (TEA), and the creation of an educational website and K-12 curricular modules based on the project.

The Shackleton Fracture Zone (SFZ) in Drake Passage of the Southern Ocean defines a boundary between low and high phytoplankton waters. Low chlorophyll water flowing through the southern Drake Passage emerges as high chlorophyll water to the east, and recent evidence indicates that the Southern Antarctic Circumpolar Current Front (SACCF) is steered south of the SFZ onto the Antarctic Peninsula shelf where mixing between the water types occurs. The mixed water is then advected off-shelf with elevated iron and phytoplankton biomass. The SFZ is therefore an ideal natural laboratory to improve the understanding of plankton community responses to natural iron fertilization, and how these processes influence export of organic carbon to the ocean interior. The bathymetry of the region is hypothesized to influence mesoscale circulation and transport of iron, leading to the observed patterns in phytoplankton biomass. The position of the Antarctic Circumpolar Current (ACC) is further hypothesized to influence the magnitude of the flow of ACC water onto the peninsula shelf, mediating the amount of iron transported into the Scotia Sea. To address these hypotheses, a research cruise will be conducted near the SFZ and to the east in the southern Scotia Sea. A mesoscale station grid for vertical profiles, water sampling, and bottle incubation enrichment experiments will complement rapid surface surveys of chemical, plankton, and hydrographic properties. Distributions of manganese, aluminum and radium isotopes will be determined to trace iron sources and estimate mixing rates. Phytoplankton and bacterial physiological states (including responses to iron enrichment) and the structure of the plankton communities will be studied. The primary goal is to better understand how plankton productivity, community structure and export production in the Southern Ocean are affected by the coupling between bathymetry, mesoscale circulation, and distributions of limiting nutrients. The proposed work represents an interdisciplinary approach to address the fundamental physical, chemical and biological processes that contribute to the abrupt transition in chl-a which occurs near the SFZ. Given recent indications that the Southern Ocean is warming, it is important to advance the understanding of conditions that regulate the present ecosystem structure in order to predict the effects of climate variability. This project will promote training and learning across a broad spectrum of groups. Funds are included to support postdocs, graduate students, and undergraduates. In addition, this project will contribute to the development of content for the Polar Science Station website, which has been a resource since 2001 for instructors and students in adult education, home schooling, tribal schools, corrections education, family literacy programs, and the general public.

The ocean plays a critical role in sequestering CO2 by exporting fixed carbon to the deep ocean through the biological pump. There is a pressing need to understand the systematics of carbon export in the Southern Ocean in the context of global warming because of the sensitivity of this region to climate change, already manifested as significant temperature increases. Numerous studies have indicated that Fe supply is a primary control on phytoplankton biomass and productivity in the Southern Ocean. The results from previous cruises in Feb-Mar 2004 and Jul-Aug 2006 have revealed the major natural Fe fertilization from Fe-rich shelf waters to the Fe-limited high nutrient low chlorophyll (HNLC) Antarctic Circumpolar Current Surface Water (ASW) in the southern Drake Passage, producing a series of phytoplankton blooms. Remaining questions include: How is natural Fe transported to the euphotic zone through small-meso-large scale horizontal-vertical transport and mixing in different HNLC ACC areas? How does plankton community structure evolve in response to a natural Fe addition, how does Fe speciation respond to biogeochemical processes, and how is Fe recycled to determine the longevity of phytoplankton blooms? How does the export of POC evolve as a function of upwelling-mixing, Fe addition-recycling and bacteria-plankton structure? This synthesis proposal will address these fundamental questions using a unique dataset combining multiyear physical, Fe and biogeochemical data collected between 2004 and 2006 from 2 NSF-funded Fe fertilization experiment cruises and 3 Antarctic Marine Living Resource (AMLR) cruises in the southern Drake Passage and southwestern Scotia Sea through collaboration with scientists in the AMLR program and US Southern Ocean GLOBEC projects. All investigators involved in this study are engaged in graduate and undergraduate instruction, and mentoring of postdoctoral researchers. Each P.I. will incorporate key elements of the proposed syntheses in our lectures, problem sets and group projects. The project includes support to convene a 4-5 day international workshop on natural Fe fertilization at Woods Hole Oceanographic Institution. The workshop will include scientists from United Kingdom, France and Germany who have conducted natural Fe fertilization experiments, and Korea and China who are planning to conduct natural Fe fertilization experiments. The participation of graduate students and postdoctoral scholars will be especially encouraged. The results will be published in a Deep-Sea Research II special issue.