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  • 1
    Electronic Resource
    Electronic Resource
    Spring bloom sedimentation in a subarctic ecosystem (1992)
    Springer
    Marine biology 114 (1992), S. 131-138 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 5-yr study (1985 to 1989) of spring bloom sedimentation in Auke Bay, Alaska, indicates that the sinking response of diatoms to ambient nutrients influences both species succession during the spring bloom and the subsequent sedimentation of new production. Diatoms from the genera Thalassiosira, Chaetoceros and Skeletonema formed the bulk of the spring bloom each year. Growth of Thalassiosira spp. consistently initiated the primary bloom, while Skeletonema costatum tended to grow later in, or after, the primary bloom. We postulate that this successional pattern is driven by interspecific nutrient competition. Overall, sedimentation flux of the dominant species of bloom diatoms was correlated with surface concentrations of cells integrated over the bloom period. In fact, different linear relationships existed when Thalassiosira and Chaetoceros spp. were considered separately, but not for Skeletonema sp., indicating that marked differences exist between the sedimentation tendencies of these genera. The observed inter-generic differences are explicable by the different overall sinking rates, as well as different nutrient-sensitivities of the sinking rates of each genus. Thalassiosira spp., the fastestsinking and most nutrient-sensitive species, contributed up to 10 x more carbon to the benthos in all years of the study, reaching a maximum of 11.1 gCm-2 over a single spring bloom event in 1988. This study indicates that the tendency to sink to the benthos during and/or after a bloom is highly dependent on species-specific cell physiology, and supports the idea that it is the fast-sinking, nutrient-sensitive diatoms, such as Thalassiosira species, that constitute the major source of vertical carbon flux in this embayment and other such coastal ecosystems during the spring bloom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350862
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  • 2
    Electronic Resource
    Electronic Resource
    Spring bloom sedimentation in a subarctic ecosystem (1992)
    Springer
    Marine biology 114 (1992), S. 119-129 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Results from a 5-yr study (1985 to 1989) in Auke Bay, Alaska show that termination of the spring bloom consistently occurred at limiting nitrate concentrations. Following nutrient exhaustion, phytoplankton sinking rates increased and displayed greater temporal variability. Threshold nitrate concentrations, approximating Ks values of the species present, were found to signal initiation of increased sedimentation. For Thalassiosira aestivalis, the threshold was ∼2 μmol l-1, while for Skeletonema costatum the threshold was ∼1 μmol l-1, suggesting genus-specific differences in sinking-rate sensitivity to nitrate exhaustion. Overall, sinking rates of the three principal genera ranked (high to low) Thalassiosira spp.〉 S. costatum〉Chaetoceros spp., while the nitrate sensitivities of the sinking rates of the genera ranked (high to low) Thalassiosira spp.〉 Chaetoceros spp.〉 S. costatum. Thalassiosira spp. showed the most consistent sinking rate increases following nutrient impoverishment. During a bloom dominated by T. aestivalis, a decrease of cell sinking rate with depth coincided with a decrease in short-term nutrient stress as measured by intracellular nitrate pools. In addition, no correlation was found between chain length or aggregate formation and sinking rate for this species. Though we measured only small-scale cell-cell adhesion, not larger-scale marine snow formation, this supports the notion that the sinking rates of Thalassiosira spp. were controlled primarily by cell physiology. For S. costatum, however, shorter chains sank faster. The sinking behavior of the species studied here figures prominently in their pelagic ecology and in the carbon flux of coastal ecosystems, both of which are driven by short-term variability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350861
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  • 3
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    Small-scale vertical and horizontal variability of physico-biogeochemical properties across the Equatorial Undercurrent in the Atlantic Ocean (2019)
    In:  EPIC3ASLO 2019 Aquatic Sciences Meeting, San Juan, Puerto Rico, 2019-02-23-2019-03-02
    Details
    Publication Date: 2019-03-08
    Description: In May 2018 we towed a new vertical undulator across the equator from 2°S to 2°N along 25°W in the central Atlantic Ocean. Towing the vehicle along a sawtooth path between 5 and 300 m depth a horizontal resolution (wavelength) of 2.5 km was achieved. The vehicle was instrumented in order to bring together marine physics, chemistry and biology. The oceanographic measurements comprised the variables of state (temperature, salinity, pressure, density), and currents as well as solar irradiance. The chemical data collected were dissolved oxygen, nitrate, pH and (indirectly) particulate organic carbon. Biological information on phytoplankton concentration and composition was obtained from fluorometry and hyperspectral radiometry. The major hydrographic feature crossed was the Equatorial Undercurrent (EUC) between roughly 1.8°S and 1.5°N in the depth range 50 to 250 m flowing mainly ENE with maximum velocities of 1 m/s, whereas the slow flow of the nitrate-deplete surface layer was westward. The chlorophyll (phytoplankton) was found concentrated subsurface in the depth range 60 to 90 m on top of the nitracline and within the vertical shear zone of the upper EUC. Horizontally the deep Chl maximum displayed patchiness at scales down to the resolution achieved, hypothetically stimulated by the variable shear-driven vertical supply of nitrate. Below the euphotic zone and both at the southern and northern flank of the EUC patches of increased oxygen concentration were found, which correlate with decreased nitrate concentration and elevated pH.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    High-resolution physical-biogeochemical structure of a filament and an eddy of upwelled water off Northwest Africa (2019)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Ocean Science, COPERNICUS GESELLSCHAFT MBH, ISSN: 1812-0784
    Details
    Publication Date: 2020-02-14
    Description: Nutrient rich water upwells offshore of Northwest Africa and is subsequently advected westwards. There it forms eddies and filaments with a rich spatial structure of physical and biological/biogeochemical properties. Here we present a high resolution (2.5 km) section through upwelling filaments and an eddy obtained in May 2018 with a Triaxus towed vehicle equipped with various oceanographic sensors. Physical processes at the mesoscale and submesoscale such as symmetric instability, trapping of fluid in eddies, and subduction of low potential vorticity (which we use as a water mass tracer) water can explain the observed distribution of biological production and export. We found a nitrate excess (higher nitrate concentrations than would be expected from oxygen values if only influenced by production and remineralization processes) core of an anti-cyclonic mode water eddy. We also found a high nitrate concentration region of ~5 km width in the mixed layer where symmetric instability appears to have injected nutrients from below into the euphotic zone. A similar region a little further south had high chlorophyll-a concentrations suggesting that nutrients had been injected there a few days earlier. Considering that such interactions of physics and biology are ubiquitous in the world's upwelling regions, we assume that they have strong influences on the productivity of such systems and their role in CO2 uptake. The intricate interplay of different parameters at kilometer scale needs to be taken into account when interpreting single profile and/or bottle data in dynamically active regions of the ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Globally Consistent Quantitative Observations of Planktonic Ecosystems (2019)
    In:  EPIC3Frontiers in Marine Science, 6(196)
    Details
    Publication Date: 2020-02-14
    Description: In this paper we review the technologies available to make globally quantitative observations of particles in general—and plankton in particular—in the world oceans, and for sizes varying from sub-microns to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is critical to improve understanding of the processes that control abundances, distributions and composition of plankton, provide data necessary to constrain and improve ecosystem and biogeochemical models, and forecast changes in marine ecosystems in light of climate change. In this paper we begin by providing the motivation for plankton observations, quantification and diversity qualification on a global scale. We then expand on the state-of-the-art, detailing a variety of relevant and (mostly) mature technologies and measurements, including bulk measurements of plankton, pigment composition, uses of genomic, optical and acoustical methods as well as analysis using particle counters, flow cytometers and quantitative imaging devices. We follow by highlighting the requirements necessary for a plankton observing system, the approach to achieve it and associated challenges. We conclude with ranked action-item recommendations for the next 10 years to move toward our vision of a holistic ocean-wide plankton observing system. Particularly, we suggest to begin with a demonstration project on a GO-SHIP line and/or a long-term observation site and expand from there, ensuring that issues associated with methods, observation tools, data analysis, quality assessment and curation are addressed early in the implementation. Global coordination is key for the success of this vision and will bring new insights on processes associated with nutrient regeneration, ocean production, fisheries and carbon sequestration.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Biogeochemistry of the Southeastern Indian Ocean (2016)
    In:  EPIC3Ocean Carbon and Biogeochemstry Summer Workshop, Woods Hole, MA, USA, 2016-07-25-2016-07-27
    Details
    Publication Date: 2017-01-20
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
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    Phyllosomata associated with large gelatinous zooplankton: hitching rides and stealing bites (2014)
    In:  EPIC3ICES Journal of Marine Science: Journal du Conseil, 72(suppl), pp. i124-i127, ISSN: 1054-3139
    Details
    Publication Date: 2017-01-20
    Description: During a zooplankton survey 350 km off the coast of Western Australia, we captured a large and robust zooid of a salp (Thetys vagina), to which six late stage larvae (phyllosomata) of the western rock lobster (Panulirus cygnus) were attached. High-throughput sequencing analyses of DNA extracts from midgut glands of the larvae confirmed that each phyllosoma had consumed mainly salp tissue ( x 1⁄4 64.5% + 15.9 of DNA reads). These results resolve long-standing conjecture whether spiny lobster phyllosomata attach to large gelatinous hosts to feed on them.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 8
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    Condition of larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic eddies of the Leeuwin Current off Western Australia (2015)
    In:  EPIC3Marine and Freshwater Research, 66(12), pp. 1158, ISSN: 1323-1650
    Details
    Publication Date: 2017-01-20
    Description: Changes in the offshore oceanographic processes are suspected to be the cause of a recent dramatic decline in the settlement of post-larvae of the Western Australian spiny lobster (Panulirus cygnus), which has greatly reduced the productivity from the world’s second-largest spiny lobster fishery. The present study assessed whether there are differences in the nutritional condition of the larvae of P. cygnus sampled from two pairs of cyclonic eddies (CEs) and anticyclonic eddies (AEs). Morphometric and biochemical analyses were undertaken on the mid–late-stage larvae (VI, VII, VIII) sampled offshore from two pairs of adjacent counter-rotating mesoscale eddies in the Leeuwin Current off Western Australia. The results showed that larvae captured from CEs had greater average total dry mass (P , 0.001) than those from AEs. Stage VIII larvae from CEs contained more protein (P , 0.008) (38.5% ` 5.4 s.e.) and lipid (P , 0.005) (67.2% ` 12.1) than did those from AEs. The possible causes for these differences are uncertain but may be related to differences in water temperatures in CEs v. AEs influencing the ability of phyllosomas to accumulate nutritional reserves.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Reduction of the Powerful Greenhouse Gas N2O in the South-Eastern Indian Ocean (2016)
    In:  EPIC3PLOS ONE, 11(1), pp. e0145996, ISSN: 1932-6203
    Details
    Publication Date: 2017-01-20
    Description: Nitrous oxide (N2O) is a powerful greenhouse gas and a key catalyst of stratospheric ozone depletion. Yet, little data exist about the sink and source terms of the production and reduc- tion of N2O outside the well-known oxygen minimum zones (OMZ). Here we show the pres- ence of functional marker genes for the reduction of N2O in the last step of the denitrification process (nitrous oxide reductase genes; nosZ) in oxygenated surface waters (180–250 O2 μmol.kg-1) in the south-eastern Indian Ocean. Overall copy numbers indicated that nosZ genes represented a significant proportion of the microbial community, which is unexpected in these oxygenated waters. Our data show strong temperature sensitivity for nosZ genes and reaction rates along a vast latitudinal gradient (32°S-12°S). These data suggest a large N2O sink in the warmer Tropical waters of the south-eastern Indian Ocean. Clone sequenc- ing from PCR products revealed that most denitrification genes belonged to Rhodobactera- ceae. Our work highlights the need to investigate the feedback and tight linkages between nitrification and denitrification (both sources of N2O, but the latter also a source of bioavail- able N losses) in the understudied yet strategic Indian Ocean and other oligotrophic systems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    A database of marine phytoplankton abundance, biomass and species composition in Australian waters (2016)
    In:  EPIC3Scientific Data, 3, pp. 160043, ISSN: 2052-4463
    Details
    Publication Date: 2017-01-20
    Description: There have been many individual phytoplankton datasets collected across Australia since the mid 1900s, but most are unavailable to the research community. We have searched archives, contacted researchers, and scanned the primary and grey literature to collate 3,621,847 records of marine phytoplankton species from Australian waters from 1844 to the present. Many of these are small datasets collected for local questions, but combined they provide over 170 years of data on phytoplankton communities in Australian waters. Units and taxonomy have been standardised, obviously erroneous data removed, and all metadata included. We have lodged this dataset with the Australian Ocean Data Network (http://portal.aodn.org.au/) allowing public access. The Australian Phytoplankton Database will be invaluable for global change studies, as it allows analysis of ecological indicators of climate change and eutrophication (e.g., changes in distribution; diatom:dinoflagellate ratios). In addition, the standardised conversion of abundance records to biomass provides modellers with quantifiable data to initialise and validate ecosystem models of lower marine trophic levels.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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