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Food web interactions at the Belgian Continental Shelf

By Travis Greene,2014-04-16 21:17
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Food web interactions at the Belgian Continental Shelf

    Diensten van de Eerste Minister

    Federale diensten voor wetenschappelijke, technische en culturele aangelegenheden

Tweede plan voor wetenschappelijke ondersteuning van

    een beleid gericht op duurzame ontwikkeling

Deel II: "Global change, Ecosystemen en Biodiversiteit"

    Netwerkovereenkomst EV/02/25A

    HOGERE TROFISCHE NIVEAUS IN DE ZUIDELIJKE NOORDZEE

    “TROPHOS

    Universiteit Gent

    Sektie Mariene Biologie

    -

    Instituut voor Natuurbehoud

    -

    Katholieke Universiteit Leuven

    Laboratorium voor Aquatische Ecologie

    WETENSCHAPPELIJK VERSLAG

    voor de periode van 01/02/2002-31/01/2003

    Food web interactions at the Belgian Continental Shelf

    1221 Jan Vanaverbeke , Leon Moodley, Karline Soetaert & Magda Vincx

1 Ghent University, Biology Department, Marine Biology Section

    2 NIOO-CEME

Introduction

    Based on results obtained in a previous OSTC-programme (Functional and structural biodiversity of North Sea ecosystems), the existence of two different food webs on the Belgian Continental Shelf (BCS) was hypothesized. A comparison of the response of nematode communities at an “open” sea station (Station 330) and a coastal „accumulation” station (Station 115 bis) (Fig. 1) to the deposition of phytodetritus during a spring phytoplankton bloom revealed completely different reactions in terms of nematode densities, vertical distribution and diversity (Steyaert et al. subm, Vanaverbeke et al., in prep).

    51.25

    51.20330

    Longitude (N)Zeebrugge

    51.15Oostende

    115bis-5 m-10 mNieuwpoort-20 m

    Dunkerque51.03.053.152.552.252.352.45Latitude (E)

    Figure 1 Map of the Belgian continental shelf with indication of the samplin stations

    Within the framework of TROPHOS, we aim to unravel the differences in the benthic food webs at these two target locations. In a first step, all biota and structuring variables

     1

    at both stations are examined in order to quantify and understand the differences in primary and secondary production at both locations at the BCS.

General sampling scheme

Both stations are visited monthly with RV Belgica or Zeeleeuw and sampled according to

    the scheme presented in Fig. 2. The concentration and organic matter content of suspended particulate matter (SPM) will provide necessary insight into trophic status of the stations, whilst their stable isotope ratios (carbon and nitrogen) together with phytopigment concentrations will help track changes and blooms of primary producers. Similarly, the isotope ratios and pigment concentrations of surface sediment is analysed to follow organic matter transfer to the sediment (benthic-pelagic coupling). The amount of incoming organic matter channelled into benthic fauna will be traced through quantification of the biomass, standing stock and nitrogen and carbon isotope signatures of major benthic components (micro-, meio- and macro-fauna). Bulk remineralization of organic matter is followed by monthly sediment oxygen consumption (SOC) measurements

    SurfacewaterSurfacewater Pigments (UG + ULB)Pigments (UG + ULB)Pigments (UG + ULB)Pigments (UG + ULB)

    Nutrients (UG)Nutrients (UG)Nutrients (UG)Nutrients (UG)

    DOC (UG)DOC (UG)DOC (UG)DOC (UG) Phytoplankton (ULB)Phytoplankton (ULB)Phytoplankton (ULB)Phytoplankton (ULB)

    SPM (NIOO-CEME)SPM (NIOO-CEME)SPM (NIOO-CEME)SPM (NIOO-CEME)

    Stable isotopes (NIOO-CEME)Stable isotopes (NIOO-CEME)Stable isotopes (NIOO-CEME)Stable isotopes (NIOO-CEME)

    BottomWaterBottomWater

    Meiobenthos (UG + NIOO-CEME)Meiobenthos (UG + NIOO-CEME)Meiobenthos (UG + NIOO-CEME)SedimentSediment Pigments (UG)Pigments (UG)Pigments (UG)

     C/N (UG)C/N (UG)C/N (UG)

     Macrobenthos (UG)Macrobenthos (UG)Macrobenthos (UG)Bacteria: diversity (UG)Bacteria: diversity (UG)Bacteria: diversity (UG)

    Size (NIOO-CEME)Size (NIOO-CEME)Size (NIOO-CEME)

    Stable isotopes (NIOO-CEME)Stable isotopes (NIOO-CEME)Stable isotopes (NIOO-CEME)Slurry incubationsSlurry incubationsSlurry incubations

    Figure 2 General sampling scheme 2

Preliminary results

    The sampling campaigns, initiated in September 2002, have been very successful and analyses on the way. Here we present some preliminary data obtained in November 2002 during a cruise with the RV Zeeleeuw.

    Sediment oxygen consumption (SOC) is a good indicator of total benthic activity and in accordance with the hypothesis, station 115 bis is characterized by higher metabolic activity. SOC at station 115 bis is more that twice that found at the “open” sea station

    (Fig. 3), reflecting a larger input of reactive organic matter to the former station.

     Sediment Oxygen Consumption

    -120

    .day15 -2

    .m102

    5

    0mmol O 115 bis330

     Station

    Figure 3: Sediment Oxygen Consumption at Station 115 bis and Station 330 (data from November 2002)

    Similarly, surficial sediment bacterial biomass was also significantly higher at station 115 bis compared to station 330 (Fig. 4). Trends in SOC and bacterial biomass highlight the large differences in trophic status of the target locations.

     Bacterial Biomass (0-1 cm)

    800

    -2600

    400

    ugC.cm200

    0 115 bis330

    Station

     3 Figure 4. Bacterial biomass at Station 115bis and Station 330

    (data from November 2002)