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 Principal Investigator • Marsh Youngbluth, Ph.D. • youngbluth@hboi.edu  Research Background - Jellyfish are highly efficient competitors and voracious predators. When numerous, these gelatinous animals can change the integrity of plankton communities. In addition, swarms of soft-bodied zooplankton are known to fowl fishing trawls, damage salmon farming, and clog seawater inlets of electrical power stations. There is a growing awareness that invasions of soft-bodied zooplankton can be as ecologically damaging as oil spills. For example, the collapse of the Black Sea fisheries, worth 250 million USD per year, has been directly attributed to a shallow-water ctenophore, Mnemiopsis leidyi. This comb jelly was introduced into the Black Sea from ballast water about a decade ago and has constituted up to 95% of the zooplankton biomass in that biotope. The degree to which gelatinous zooplankton can be regulatory components of marine food webs is difficult to assess. Their bodies are fragile and easily damaged by traditional sampling with plankton nets. Consequently, reports on their natural history as well as quantitative accounts of the abundance, feeding, and metabolism of these animals are rare, especially for mesopelagic species. The application of submersible technology in deep water environments provides opportunities to optimize where, when, and how to conduct critical ecological studies. With regard to midwater gelatinous species, this in situ approach to field work provides unambiguous information about their distribution and behavior in relation to physical and chemical variables. Such data serve as a basis for conducting meaningful experiments in the natural environment. Alternatively, undersea vehicles can be used to collect delicate individuals for investigations in shipboard and shore-based laboratories.  Research supported in part by a Guest Scientist fellowship awarded by the University of Bergen and a grant from the Division of International Programs, National Science Foundation (INT-9903467). (January 1999-December 2002) Overview: The deep fjords of Norway, particularly those with shallow sills, are ideal marine environments for studies various midwater fauna. The normally calm sea states allow access to deep (up to 1200 m) environments throughout the year, and therefore facilitate investigations of processes that influence zooplankton abundance and recruitment over diel and seasonal scales. Physical exchange of water is restricted primarily to the layer above the sill depth, and consequently, the animal communities that live in deep fjord basins tend to remain undisturbed by advective forces for prolonged periods.  Recent studies of the mesopelagic coronate scyphomedusa Periphylla periphylla have been in conducted Lurefjorden, 50 km north of Bergen. Here, the standing stock of this jellyfish is three or more orders of magnitude higher than in the open ocean and this single species, over the span of about two decades, has become the top predator. This condition may eventually provide insight about how physical and biological factors can interact to maintain such a situation. Since jellyfishes in contrast to fishes are considered as useless production for the human population, such knowledge is of more than purely academic interest. The use of a remotely operated vehicle (ROV) and an underwater video profiler have allowed detailed studies, both at the population and the individual levels. Associated Publications:
Research supported by a grant from the Biological Oceanography Program, National Science Foundation (OCE 0086229) - Development Of In Situ Techniques For Quantifying Rates For Feeding, House Production And House Flux Of Appendicularians(January 2001-December 2001) Overview: The importance of soft-bodied zooplankton to particle dynamics represents an understudied component of marine food webs. This project is significant because it directly addresses the cycling of organic matter in the ocean in terms of sources, transformations, and exports. Novel in situ, submersible-based tools and techniques will be tested to develop a basis for more detailed, long-term investigations of the ecological  roles that relatively large appendicularians and their houses (up to 30 cm diameter) play. These species are poorly known but ubiquitous in water column environments on a global scale and are often numerous. Consequently, they are tractable targets for in situ documentation of various rates, i.e., feeding, house production, and house flux. The small, but compelling amount of field information about such omnivorous, non-selective filter-feeders suggests that they must have a central role the flux of material throughout the water column, especially in particle-rich layers. First, appendicularians are capable of rapid generation times. Second, most species are capable of high grazing rates on a wide spectrum of particles, i.e., microbial phytoplankton, bacteria and detritus. Whether the export or recycling of biogenic carbon from the particle-laden appendicularian houses is slow or rapid depends on several factors. For example, it is likely that particle loading on houses in the epipelagic and epibenthic zones will vary in relation to surface production and resuspension, respectively. Rate determinations (i.e., particle selection, feeding rates, house-fecal pellet production, and house-fecal pellet sinking rates) will also vary with species, particle selection and house age. Hence, reliable field methods are essential for understanding how behavioral and environmental parameters interact to influence the fate of particulate matter.  This project is exploratory and addresses in situ approaches that can quantify various rate processes. Such data, when combined with future documentation of the vertical distribution, relative abundance, chemical composition, and particle loads of appendicularians and the houses they produce, are likely to substantively broaden the understanding of how pelagic food webs work. Investigations will be focused on two relatively narrow depth intervals (i.e., subsurface chlorophyll maximum zone and benthic boundary layer) where midwater appendicularians are known to aggregate. Sampling at interfaces is important because these areas represent a crucial but often unrecognized aspect of biological oceanography, i.e., pelagic animals are often numerous in thin (cm to m thick) layers coincident with predictable physical and chemical boundaries in pelagic environments. In this context, inferences about population energetics and particle flux will not be limited by ignorance of "how many" animals there are nor by "how fast" they feed. Research supported by a grant from the Biological Oceanography Program, National Science Foundation (OCE 0002493) Ü Predation by the physonect siphonophore Nanomia cara (January 2001-December 2003) Overview: Reliable predictions about the structure and function of pelagic food webs should be based on a balance of observational and experimental studies of key species. Regulation of prey populations by predators, for example, results from the interplay of biological processes that operate on various temporal and spatial scales. The impact of midwater gelatinous predators, in particular, is virtually unknown, principally because reliable assessments of their distribution, abundance, and trophic interactions are difficult to obtain.  Colonies of the physonect siphonophore Nanomia cara constitute a persistent group of carnivores that inhabit mesopelagic depth along the Atlantic Coast from Cape Hatteras to the Gulf of Maine. Previous SCUBA and submersible-based observations in the Gulf of Maine have indicated that relatively high densities of relatively large colonies can be distributed throughout the upper 200 m. It's not surprising that year to year variations in abundance occur, but no rigorous assessments of factors underlying the three-order magnitude range in population fluctuations have ever been published. This project will be conducted for 3 consecutive years to document interannual, albeit short-term (spring and fall cruises), spatial and temporal variability of foraging by N. cara. Some important questions are: Does N. cara alter prey selection and prey consumption in relation to prey density and prey distribution; Are these siphonophores selective or opportunistic predators; Does N. cara always migrate to feed in shallow water? The focused, quantitative approach of this project will define the predatory role of a deep-living, but migratory physonect siphonophore. The overall design of this study (i.e., sampling in late summer seasons during three consecutive years and sampling in late spring in years 2 and 3) will be sufficiently rigorous to allow predictions  about predation rates in WB and in contiguous offshore shelf/slope regimes. That is, interannual variability in the abundance of colonies, the abundance and diversity of prey, and environmental processes (e.g., stratification and circulation) will provide a range of data suitable for defining the feeding habits of Nanomia cara. Of particular interest is colony predation on the over-wintering phase of Calanus finmarchicus. Comparisons of predator and prey abundance will allow estimates of feeding potential for different sectors of the water column on temporal scales. That is, colonies may alter their diel cycle of vertical migration and feed within depth intervals where diapausing copepods are concentrated, e.g., in Wilkinson Basin and Oceanographer Canyon. Alternatively, colonies may adopt a regimen of continuous feeding and disperse throughout the water column, e.g., in the frontal zone over Georges Bank. Knowledge of all these in situ relationships, rather than integrated determinations for the water column, should contribute significantly to predictive models for predator-prey dynamics, especially if copepod populations are predator-controlled and not food-limited. This study will complement GLOBEC projects that have focused on predation of copepods in the study area, e.g., investigations of pelagic hydroids, medusae, ctenophores, euphausiids, hyperiid amphipods, decapod shrimp, and chaetognaths, as well as vertebrate predators, primarily herring and mackerel. Collaboration with other scientists will be undertaken to the fullest extent possible. CURRICULUM VITAE DR. MARSH J. YOUNGBLUTH Harbor Branch Oceanographic Institution 5600 U.S. 1, North, Fort Pierce, Florida 34946 USA Tel - 772/465-2400, ext. 319, Fax - 772/468-0757, email: youngbluth@hboi.edu RESEARCH EXPERIENCE: Biological Oceanography, Emphasis on Biodiversity and Ecology of Midwater Zooplankton Particle Transport and Transformation in Mesopelagic Regimes EDUCATION: Ph.D. (Biology, 1972) Stanford University M.S. (Zoology, 1966) University of Hawaii B.S. (Biology, 1963) Portland State University PROFESSIONAL EXPERIENCE: Research Senior Scientist (1979-1992, 1994-2001), Associate Scientist (1975-1978): Principal Investigator for Water Column Ecology Department, HBOI, Fort Pierce, Florida Visiting Scientist: University of Bergen (1998, 1999, 2000, 2002); Japanese Society for Promotion of Science (1997); National Center for Scientific Research (CNRS), Station Zoologique, France (1988, 1990, 1991, 1992, 2000) Chief Scientist (1969-1999): Conducted oceanographic research on HBOI, NOAA, UNOLS and Norwegian vessels in Atlantic and Pacific Oceans as well as Caribbean and Mediterranean Seas Research Scientist (1973-1975): Principal Investigator for coastal zooplankton research at the Atomic Energy Commission Nuclear Center/University of Puerto Rico, Mayaguez Laboratory Manager, Micronesia (1966): Manager of field station established for atoll research projects (Atomic Energy Commission, Enewetak, Marshall Islands) Administration Program Director (1995-1997), Biological Oceanography, National Science Foundation, IPA Appointment, Arlington, Virginia Program Manager (1992-1993), National Undersea Research Program, National Oceanic and Atmospheric Administration, Silver Spring, Maryland Division Director (1982-1985), Marine Sciences, Harbor Branch Oceanographic Institution Chief Administrative Officer (1977-1989) Postdoctoral Program, Harbor Branch Institution RECENT ADVISORY ACTIVITIES: (May 2002) International Workshop on Exploration of the Seas, Paris, France (January 2002) MAR-ECO Workshop on Census of Marine Life, Bremerhaven, Germany (July 2001): NOAA Arctic Expedition Planning Workshop for Ocean Exploration Program, Washington DC (October 1999): NSF/ONR Workshop on Developing Submergence Science for the Next Decade, Washington DC (May 1999): Panel Review for ONR/NSF/National Oceanographic Partnership Program, Washington DC (November 1998): Panel Review for NOAA/National Undersea Research Center, University of Connecticut, Avery Point SPONSORED RESEARCH: National Science Foundation, National Oceanic and Atmospheric Administration, Norwegian Research Council, Ministre de la Recherche et de la Technologie, North Atlantic Treaty Association, National Geographic Society, Link Foundation SELECTED PUBLICATIONS:
*denotes published abstracts and miscellaneous papers. Details about topics available on request.
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