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  • Articles  (62)
  • 2000-2004  (61)
  • 1985-1989  (1)
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  • 11
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    A stable isotope approach to the eastern Weddell Sea trophic web: focus on benthic amphipods (2002)
    In:  EPIC3Polar biology, 25, pp. 280-287
    Details
    Publication Date: 2019-07-16
    Description: Stable isotope (13C/12C and 15N/14N) analyses were performed on 90 species belonging to different benthic communities sampled in the eastern Weddell Sea. The study focused on eight amphipod species whose isotopic composition was compared to their previously described respective gut contents. Amphipod stable isotope ratios correspond fairly accurately to the trophic classification based on gut contents and attest to their wide spectrum of feeding types. Since the fundamental difference between the isotope and the gut content approaches to diet studies is the time scale each method addresses, this coincidence indicates that there would be no significant changes in feeding strategies over time. Three levels of the food web are covered by the eight species and, instead of belonging strictly to one trophic category, amphipods display a continuum of values from the suspension-feeder to scavengers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 12
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    The reproductive cycle of Eurhomalea exalbida (Chemnitz, 1795) (Bivalvia: Veneridae) in Ushuaia Bay (54°50′ S), Beagle Channel (Argentina) (2002)
    In:  EPIC3Invertebrate reproduction & development, 42(1), pp. 61-68
    Details
    Publication Date: 2019-07-16
    Description: The reproductive cycle of Eurhomalea exalbida (Chemnitz, 1795) in Ushuaia Bay, Beagle Channel, was studied from October 1998 to December 1999. Clams were collected monthly by SCUBA diving at 3 to 5 m water depth. The degree of sexual maturity was determined histologically (n=318). The sex ratio was 1:1 (Chi-squared p 〉 0.05). First sexual maturity occurred at 39 mm shell heigth in males and 40 mm in females (i.e. 4 years of age).Five distinct histological stages of sexual maturity could be established in males: (1) Early Active, (2) Late Active, (3) Ripe, (4) Partially Spawned and (5) Spent. Females had oocytes ranging from small and immature to large and developed in their ovaries throughout the year, hence we could not classify reproductive stages based on a qualitative histological scale of sexual maturity. Therefore, quantitative measures using an image analyzer were used. In males a high percentage of ripe individuals were present between January and August. The percentage of early active and partially spawned individuals was highest in November 1998 (70%) and 1999 (60%). In females, the mean number of developed oocytes per gonadal area, the mean diameter (minor axis) of oocytes, and the percentage of gonadal area occupied by oocytes were lowest in November, indicating a spawning peak. These results indicate synchronous gonadal development and spawning in males and females. The more intensive spawning activity in November coincides with the higher biomass and production of phytoplankton in spring.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 13
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    Age and productivity of the Antarctic scallop, Adamussium colbecki, in Terra Nova Bay (Ross Sea, Antarctica) (2003)
    In:  EPIC3Journal of experimental marine biology and ecology, 288, pp. 239-256, ISSN: 0022-0981
    Details
    Publication Date: 2019-07-16
    Description: Body size, geographical distribution and biomass make Adamussium colbecki (Smith 1902) one of the most important bivalve species in the Antarctic. Based on samples collected in austral summer 1999/2000 in Terra Nova Bay, the annual formation of shell growth bands visible on x-ray photographs was verified by stable isotope analyzis. A general von Bertalanffy growth function was fitted to size-at-age data of 25 individuals (H*= 108.86 mm, K= 0.114 y-1, t0= -0.367, D= 1.284). Maximum age of A. colbecki is likely to be more than 18 years. Somatic production calculated from mass-specific growth rates was 235 kJ m-2 y-1. Gonadal productivity estimated by an average value for reproductive output of pectinids amounted to 59 kJ m-2 y-1. Annual somatic and gonad production-to-biomass ratios (P/B) were 0.199 and 0.043, respectively. According to its consumption and production A. colbecki is likely to play a significant role in the trophic web of Terra Nova Bay.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 14
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    Comparing production-biomass ratios of benthos and suprabenthos in macrofaunal marine crustaceans (2002)
    In:  EPIC3Canadian journal of fisheries and aquatic sciences, 59, pp. 1616-1625
    Details
    Publication Date: 2019-07-16
    Description: Using available data from the literature, we compared the productionbiomass ratios (P/B) between the suprabenthic (= hyperbenthic) and the benthic (infaunaepifauna) species within the group of the macrofaunal marine crustaceans. This data set consists of 91 P/B estimates (26 for suprabenthos and 65 for infaunaepifauna) for 49 different species. Suprabenthic crustacean P/B was significantly higher than P/B of benthic crustacean (post-hoc Scheffé test; one-way analysis of covariance, ANCOVA; p 〈 103) and also of other (noncrustacean) benthic invertebrate (p 〈 104). Predictive multilinear regression (MLR) analysis for macrofaunal marine crustaceans showed P/B to depend significantly on mean annual temperature (T) and mean individual weight (W) (R2 = 0.367). Adding the variable swimming capacity increased goodness-of-fit to R2 = 0.528. The higher P/B of suprabenthic (= swimming) macrofauna in comparison with that of the benthic compartment seems to be related to the most apparent feature of the suprabenthos, its swimming capacity. The high P/Bs reported for suprabenthic species indicate how a nontrivial part of benthic production can be ignored if suprabenthos is not well sampled, therefore biasing the models of energy flow generated for trophic webs.
    Repository Name: EPIC Alfred Wegener Institut
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  • 15
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    Performance comparison between regression and neural network models for forecasting Pacific sardine (Sardinops caeruleus) biomass (2000)
    In:  EPIC3Lek, S., Huégan, J.-F. (eds). Artificial neural networks - application to ecology and evolution. Springer, Berlin, pp. 157-164, ISBN: 3-540-66921-3
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 16
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    Reproduction and recruitment patterns of the surf clam Donax serra (Bivalvia, Donacidae) on two Namibian sandy beaches (2001)
    In:  EPIC3A decade of Namibian fisheries science / Ed. by A. I. L. Payne ... (South African journal of marine science / Republic of South Africa, Department of Environment Affairs, Sea Fisheries Research Institute ; 23.2001), pp. 53-60, ISSN: 0257-7615
    Details
    Publication Date: 2019-07-16
    Description: Reproduction and recruitment of the surf clam Donax serra on two Namibian beaches were studied over a period of two years. Histological examination of the gonads indi-cated a discontinous annual reproductive cycle, related to monthly mean sea surface temperatures. The spawning season lasted from August/September until February but juveniles (2-6 mm anterior-posterior shell length) were only present for three months in the intertidal zone. The condition index indicates that the species spawns during autumn and summer, but histological validation is needed. The period when juveniles are abun-dant is decoupled from the spawning period and therefore cannot be predicted clearly, even if the spawning time is known. Starvation, hydrodynamic processes, chemical parameters and different release times during the spawning period are thought to cause the differences in settlement time and in recruitment strength between locations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 17
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    Population dynamics in benthic invertebrates. A virtual handbook (2001)
    In:  EPIC3http://www.awi-bremerhaven.de/Benthic/Ecosystem/FoodWeb/Handbook/main.html. Alfred Wegener Institute for Polar and Marine Research, Germany
    Details
    Publication Date: 2014-04-15
    Description: This book is a compilation of the state-ot-the-art tools for the analysis of population dynamics (growth, mortality, production, consumption, assimilation, respiration) in benthic invertebrates. It is an attempt to systemise our present knowledge and to pass it on to the next generation of scientists. The handbook deals with- the models used to describe population processes,- the analytical tools used to apply these models to data, and- the data required for using these tools.Most of the models introduced here are quite simple, and surely well known to many readers. Rather basic calculation tools and mathematical abilities are required. Anybody who can handle spread sheets and linear regression will be fine with most tools.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Book , peerRev
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  • 18
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    Survivorship of juvenile surf clams Donax serra (Bivalvia, Donacidae) exposed to severe hypoxia and hydrogen sulphide (2002)
    In:  EPIC3Journal of experimental marine biology and ecology, 271(1), pp. 9-23
    Details
    Publication Date: 2019-07-16
    Description: Toxic "sulphide eruptions" sporadically occur in the highly productive inshore regions of the central Namibian Benguela upwelling system. The surf clam Donax serra (Röding, 1798) dominates the intertidal and upper subtidal of large exposed sandy beaches of southern Africa and its recruitment seems to be affected by sulphide events. The reaction of juvenile surf clams to low oxygen concentrations and sulphide occurrence (0.1 mmol l-1) was examined by in vitro exposure experiments in a gas-tight continuous flow system. After 2 h of hypoxic- and hypoxic-sulphidic conditions clams moved to the sediment surface, aiding their passive transport to areas with more favourable conditions. The clams showed a high sulphide detoxification capacity by oxidising the penetrating hydrogen sulphide to non-toxic thiosulphate. Moreover, juvenile D. serra switched to anaerobic energy production, indicated by the significant accumulation of succinate and, to some extent, alanine. Test animals were not able to reduce their energy requirements enough to withstand long periods of exposure, leading to a median survival time (LT50) of 80 h under hypoxic sulphide incubation. In conclusion, natural "sulphide eruptions", especially those with a large spatial and temporal extension, have to be considered as an important factor for D. serra recruitment failures. Hydrogen sulphide is assumed to be a potential community structuring factor.
    Repository Name: EPIC Alfred Wegener Institut
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  • 19
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    Growth and production of the venerid bivalve Eurhomalea exalbida in the Beagle Channel, Tierra del Fuego (2002)
    ELSEVIER SCIENCE BV
    In:  EPIC3Journal of Sea Research, ELSEVIER SCIENCE BV, 48, pp. 209-216, ISSN: 1385-1101
    Details
    Publication Date: 2019-07-16
    Description: Growth, mortality and productivity of the hard clam E. exalbida from Ushuaia Bay, Beagle Channel were investigated. The parameters of the von Bertalanffy growth function were estimated to be H = 73.98 mm, K = 0.180 y 1, t0 = 0.147 y. Maximum individual production amounted to 2.742 g shell free wet mass (SFWM) at 49.5 mm shell height. Animals between 40 mm and 70 mm shell height contribute most to overall population somatic production P of 133.89 g SFWM m-2 y-1. Mean annual biomass B amounted to 1122.69 g SFWM m-2 y-1. Annual P/B ratio and mortality rate Z were estimated to 0.119 y-1 and 0.141 y-1, respectively. Slow growth and low turnover makes this population less suitable for sustainable commercial exploitation.
    Repository Name: EPIC Alfred Wegener Institut
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  • 20
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    Saving by freezing? Scallops in cold and temperate waters (2001)
    In:  EPIC3Abstracts, World Congress of Malacology 2001, Vienna, Austria, 154 p.
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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