314 research outputs found
Advancing science from plankton to whalesâCelebrating the contributions of James J. McCarthy
Hailing from Sweet Home, Oregon, where his father introduced him to the fascinations of pondwater (McCarthy 2018), Jim McCarthy graduated from Gonzaga University, and in the late 1960s joined the Food Chain Research Group at the Scripps Institution of Oceanography, where he received his doctorate in 1971. The Food Chain Research Group, which was becoming recognized as the premier research group on plankton, was at that time directed by such distinguished scientists as John Strickland and Dick Eppley, among others. The goal of the Food Chain Group was to understand plankton dynamics and trophodynamics, âto a degree that will enable man to exercise satisfactory control of the environment and make useful predictionsâ (Institute of Marine Resources annual report, 1968, cited in Shor 1978:143) and âto predict the formation and transfer of nutrients through the full cycle of life in the oceanâ (Shor 1978:140). It was there that Jim became immersed in all aspects of nutrients, plankton, and the marine food web
Harmful algal blooms and eutrophication : examining linkages from selected coastal regions of the United States
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Harmful Algae 8 (2008): 39-53, doi:10.1016/j.hal.2008.08.017.Coastal waters of the United States (U.S.) are subject to many of the major harmful algal
bloom (HAB) poisoning syndromes and impacts. These include paralytic shellfish poisoning
(PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), ciguatera
fish poisoning (CFP) and various other HAB phenomena such as fish kills, loss of submerged
vegetation, shellfish mortalities, and widespread marine mammal mortalities. Here, the
occurrences of selected HABs in a selected set of regions are described in terms of their
relationship to eutrophication, illustrating a range of responses. Evidence suggestive of
changes in the frequency, extent or magnitude of HABs in these areas is explored in the
context of the nutrient sources underlying those blooms, both natural and anthropogenic. In
some regions of the U.S., the linkages between HABs and eutrophication are clear and well
documented, whereas in others, information is limited, thereby highlighting important areas
for further research.Support was provided through the Woods Hole Center for Oceans
and Human Health (to DMA), National Science Foundation (NSF) grants OCE-9808173 and
OCE-0430724 (to DMA), OCE-0234587 (to WPC), OCE04-32479 (to MLP), OCE-0138544
(to RMK), OCE-9981617 (to PMG); National Institute of Environmental Health Sciences
(NIEHS) grants P50ES012742-01 (to DMA) and P50ES012740 (to MLP); NOAA Grants
NA96OP0099 (to DMA), NA16OP1450 (to VLT), NA96P00084 (to GAV and CAH),
NA160C2936 and NA108H-C (to RMK), NA860P0493 and NA04NOS4780241 (to PMG),
NA04NOS4780239-02 (to RMK), NA06NOS4780245 (to DWT). Support was also provided from the West Coast Center for Oceans and Human Health (to VLT and WPC), USEPA
Grant CR826792-01-0 (to GAV and CAH), and the State of Florida Grant S7701617826 (to
GAV and CAH)
Ammonium regeneration: Its contribution to phytoplankton nitrogen requirements in a eutrophic environment
Ammonium regeneration, nutrient uptake, bacterial activity and primary production were measured from March to August 1980 in Bedford Basin, Nova Scotia, Canada, a eutrophic environment. Rates of regeneration and nutrient uptake were determined using 15N isotope dilution and tracer methodology. Although primary production, nutrient uptake and ammonium regeneration were significantly intercorrelated, no relationship was detected between these parameters and heterotrophic activity. The average contribution of ammonium to total nitrogen (ammonium+nitrate) uptake was similar in the spring and in the summer (approximately 60%). On a seasonal average basis, 36% of the phytoplankton ammonium uptake could be supplied by rapid remineralization processes. In spite of the high average contribution of NH4 regeneration to phytoplankton ammonia uptake, there is indirect evidence suggesting that other NH4 sources may occasionally be important
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Laser-plasma weapons-effects-simulation progress report
The present goal of the Laser-Plasma Weapons-Effects-Simulation Program is the study of the conversion of laser radiation to x-radiation. The purpose is ultimately to make an intense pulsed source of x-rays to be useful in simulation programs. The requirement of a large conversion efficiency (from Laser to x-radiation) is important in order to minimize the energy requirements, size, and expense of the laser system
Phylogenetic relationships of cone snails endemic to Cabo Verde based on mitochondrial genomes
Background: Due to their great species and ecological diversity as well as their capacity to produce hundreds of different toxins, cone snails are of interest to evolutionary biologists, pharmacologists and amateur naturalists alike. Taxonomic identification of cone snails still relies mostly on the shape, color, and banding patterns of the shell. However, these phenotypic traits are prone to homoplasy. Therefore, the consistent use of genetic data for species delimitation and phylogenetic inference in this apparently hyperdiverse group is largely wanting. Here, we reconstruct the phylogeny of the cones endemic to Cabo Verde archipelago, a well-known radiation of the group, using mitochondrial (mt) genomes. Results: The reconstructed phylogeny grouped the analyzed species into two main clades, one including Kalloconus from West Africa sister to Trovaoconus from Cabo Verde and the other with a paraphyletic Lautoconus due to the sister group relationship of Africonus from Cabo Verde and Lautoconus ventricosus from Mediterranean Sea and neighboring Atlantic Ocean to the exclusion of Lautoconus endemic to Senegal (plus Lautoconus guanche from Mauritania, Morocco, and Canary Islands). Within Trovaoconus, up to three main lineages could be distinguished. The clade of Africonus included four main lineages (named I to IV), each further subdivided into two monophyletic groups. The reconstructed phylogeny allowed inferring the evolution of the radula in the studied lineages as well as biogeographic patterns. The number of cone species endemic to Cabo Verde was revised under the light of sequence divergence data and the inferred phylogenetic relationships. Conclusions: The sequence divergence between continental members of the genus Kalloconus and island endemics ascribed to the genus Trovaoconus is low, prompting for synonymization of the latter. The genus Lautoconus is paraphyletic. Lautoconus ventricosus is the closest living sister group of genus Africonus. Diversification of Africonus was in allopatry due to the direct development nature of their larvae and mainly triggered by eustatic sea level changes during the Miocene-Pliocene. Our study confirms the diversity of cone endemic to Cabo Verde but significantly reduces the number of valid species. Applying a sequence divergence threshold, the number of valid species within the sampled Africonus is reduced to half.Spanish Ministry of Science and Innovation [CGL2013-45211-C2-2-P, CGL2016-75255-C2-1-P, BES-2011-051469, BES-2014-069575, Doctorado Nacional-567]info:eu-repo/semantics/publishedVersio
Barnegat Bay-Little Egg Harbor Estuary : case study of a highly eutrophic coastal bay system
Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 17 (2007): S3âS16, doi:10.1890/05-0800.1.The Barnegat Bay-Little Egg Harbor Estuary is classified here as a highly eutrophic estuary based on application of NOAAâs National Estuarine Eutrophication Assessment model. Because it is shallow, poorly flushed, and bordered by highly developed watershed areas, the estuary is particularly susceptible to the effects of nutrient loading. Most of this load (~50%) is from surface water inflow, but substantial fractions also originate from atmospheric deposition (~39%), and direct groundwater discharges (~11%). No point source inputs of nutrients exist in the Barnegat Bay watershed. Since 1980, all treated wastewater from the Ocean County Utilities Authority's regional wastewater treatment system has been discharged 1.6 km offshore in the Atlantic Ocean. Eutrophy causes problems in this system, including excessive micro- and macroalgal growth, harmful algal blooms (HABs), altered benthic invertebrate communities, impacted harvestable fisheries, and loss of essential habitat (i.e., seagrass and shellfish beds). Similar problems are evident in other shallow lagoonal estuaries of the Mid-Atlantic and South Atlantic regions. To effectively address nutrient enrichment problems in the Barnegat Bay-Little Egg Harbor Estuary, it is important to determine the nutrient loading levels that produce observable impacts in the system. It is also vital to continually monitor and assess priority indicators of water quality change and estuarine health. In addition, the application of a new generation of innovative models using web-based tools (e.g., NLOAD) will enable researchers and decision-makers to more successfully manage nutrient loads from the watershed. Finally, the implementation of stormwater retrofit projects should have beneficial effects on the system.Financial support of the Barnegat Bay National Estuary Program and Jacques Cousteau National Estuarine Research Reserve is gratefully acknowledged
Primary, new and export production in the NW Pacific subarctic gyre during the vertigo K2 experiments
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1594-1604, doi:10.1016/j.dsr2.2008.04.013.This paper presents results on tracer experiments using 13C and 15N to
estimate uptake rates of dissolved inorganic carbon (DIC) and nitrogen (DIN).
Experiments were carried out at station K2 (47°N, 161°E) in the NW Pacific subarctic
gyre during July-August 2005. Our goal was to investigate relationships between new
and export production. New production was inferred from the tracer experiments using
the f ratio concept (0-50m); while export production was assessed with neutrally
buoyant sediment traps (NBSTs) and the e ratio concept (at 150m). During trap
deployments, K2 was characterized both by changes in primary production (523 to 404
mg C m-2 d-1), new production (119 to 67 mg C m-2 d-1), export production (68 to 24 mg
C m-2 d-1) and phytoplankton composition (high to low proportion of diatoms). The data
indicate that 17 to 23% of primary production is exportable to deeper layers (f ratio) but only 6 to 13% collected as a sinking particle flux at 150m (e ratio). Accordingly, > 80%
of the carbon fixed by phytoplankton would be mineralized in the upper 50m (1 â f),
while < 11% would be within 50-150m (f â e). DIN uptake flux amounted to 0.5 mM m-2
h-1, which was equivalent to about 95% particulate nitrogen (PN) remineralized and/or
grazed within the upper 150 m. Most of the shallow PN remineralization occurred just
above the depth of the deep chlorophyll maximum (DCM), where a net ammonium
production was measured. Below the DCM, while nitrate uptake rates became negligible
because of light limitation, ammonium uptake did continue to be significant. The uptake
of ammonium by heterotrophic bacteria was estimated to be 14-17% of the DIN
assimilation. Less clear are the consequences of this uptake on the phytoplankton
community and biogeochemical processes, e.g. new production. It was suggested that
competition for ammonium could select for small cells and may force large diatoms to
use nitrate. This implies that under Fe stress as observed here, ammonium uptake is
preferred and new production progressively suppressed despite the surplus of nitrate.This research was supported by the Research Foundation Flanders through grant
G.0021.04 and Vrije Universiteit Brussel via grant GOA 22, as well as the US National
Science Foundation programs in Chemical and Biological Oceanography
Ecological and morphological features of Amyloodinium ocellatum occurrences in cultivated gilthead seabream Sparus aurata L.; A case study
Understanding the patterns of occurrence of the ectoparasite Amyloodinium ocellatum and the conditions that result in its maintenance at non-dangerous levels for gilthead seabream Sparus aurata could be very useful, since outbreaks of heavy infestation by this parasitic dinoflagellate can cause severe mortality in temperate aquaculture. We have evaluated the interactions between A. ocellatum and related environmental variables for the first time. Biotic and abiotic parameters of water quality in production ponds from a temperate aquaculture (Sado Estuary, Portugal) were monitored and subsequently analysed. Dissolved oxygen, water temperature, pH, phytoplankton biomass and salinity were closely related to A. ocellatum occurrences; dissolved oxygen, water temperature, pH and phytoplankton biomass had significant negative relationships with A. ocellatum trophonts, while salinity had a significant positive relationship with A. ocellatum trophonts in fish gills. Phytoplankton biomass was significantly correlated with increases of dissolved oxygen in production ponds. An increase of rate of water renewal increased salinity, due to persistence of low water levels in production ponds during the water renewal procedure. Salinity negatively affected phytoplankton biomass and consequently the level of dissolved oxygen, raising the probability of A. ocellatum occurrences. Fish biomass in production ponds was correlated with the average and the maximum number of trophonts found in fish gills, highlighting the importance of defining stocking levels and production values in ponds. The present results help to improve understanding of the interactions between biotic and abiotic variables, fish farm management practices and parasite incidence in temperate terrestrial pond aquaculture.
A morphological feature of the A. ocellatum tomonts cells in division phase, collected from the most infected fish gills, is discussed. We also give a description and illustration of the phases of the A. ocellatum life cycle
Iron and phosphorus co-limit nitrogen fixation in the eastern tropical North Atlantic
The role of iron in enhancing phytoplankton productivity in high nutrient, low chlorophyll oceanic regions was demonstrated first through iron-addition bioassay experiments1 and subsequently confirmed by large-scale iron fertilization experiments2. Iron supply has been hypothesized to limit nitrogen fixation and hence oceanic primary productivity on geological timescales3, providing an alternative to phosphorus as the ultimate limiting nutrient4. Oceanographic observations have been interpreted both to confirm and refute this hypothesis5, 6, but direct experimental evidence is lacking7. We conducted experiments to test this hypothesis during the Meteor 55 cruise to the tropical North Atlantic. This region is rich in diazotrophs8 and strongly impacted by Saharan dust input9. Here we show that community primary productivity was nitrogen-limited, and that nitrogen fixation was co-limited by iron and phosphorus. Saharan dust addition stimulated nitrogen fixation, presumably by supplying both iron and phosphorus10, 11. Our results support the hypothesis that aeolian mineral dust deposition promotes nitrogen fixation in the eastern tropical North Atlantic
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