The temporal variation of the meiobenthos along a bathymetrical transect Hausgarten, Arctic: impact - PowerPoint PPT Presentation

1 / 19
About This Presentation
Title:

The temporal variation of the meiobenthos along a bathymetrical transect Hausgarten, Arctic: impact

Description:

May be an explanation for the low copepod and nematode densities. H2O content of the sediment very high at 4000 m depth in 2002 just as copepod densities. ... – PowerPoint PPT presentation

Number of Views:64
Avg rating:3.0/5.0
Slides: 20
Provided by: annvan
Category:

less

Transcript and Presenter's Notes

Title: The temporal variation of the meiobenthos along a bathymetrical transect Hausgarten, Arctic: impact


1
The temporal variation of the meiobenthos along a
bathymetrical transect (Hausgarten, Arctic)
impact of climatic oscillations Eveline Hoste,
Thomas Soltwedel, Sandra Vanhove and Ann Vanreusel
2
Introduction
  • Meiofauna (Metazoa 32µm-1mm)
  • Arctic deepsea (1500m-5000m)
  • Temporal variation in climate includes
  • climate change
  • climatic oscillations
  • 1. ENSO
  • 2. AO
  • interannual variation

3
Objectives
  • The aim is to make a statistical model that
    allows predictions of changes in the meiobenthos
    ecosystem in relation to variation in
    environmental parameters linked to climate
    oscillations (e.g. NAO, ENSO) and global warming.
    Models will be adjusted according to the answers
    to following questions
  • Are there annual differences in meiobenthos
    composition in the Arctic region and can these
    differences be linked to changes in physical and
    biological environmental parameters, such as
    oxygen concentration, temperature and food
    supply?
  • Is there a relation between changes in meiofauna
    community structure and environmental parameters
    along the bathymetrical gradient?
  • Emphasis will be on nematodes and copepods, the
    most abundant meiofauna taxa

Materials and method
  • study area
  • sampling method

4
Results
  • Nematodes are the dominant taxon followed by
    copepods
  • 1000-2000 m forms a group in the MDS-plot
  • The group is separated from the other samples
    because of high nematode and copepod densities
  • BUT
  • Stress factor is relatively high
  • Other meiofauna taxa presented nauplii,
    Kinorhyncha, Gastrotricha, Tardigrada,
    Priapulida, Ostracoda, Rotifera, ... all in very
    low densities.

MDS mean meiofauna densities
5
Results (2)
  • High densities
  • max density 4057 nem/10 cm²
  • 105 cop/10 cm²
  • Both at 2000 m depth in 2002
  • Nematode and copepod densities follow same
    pattern along the depth gradient
  • Some interannual differences are apparent
  • Copepod and nematode densities are correlated
    with depth
  • nematode and copepod densities with depth
    within the sediment
  • High copepod and nematode densities at 2000 m,
    especially in 2002
  • very low copepod and nematode densities at 2500
    m in 2000
  • high copepod densities at 4000 m in 2002

6
Results (3)
  • Very fine sediment, deeper stations have
    coarser sediment
  • BUT
  • Data missing for 2000 and 5000 m depth and
    sediment analysis only for 2001
  • O2 data only for the year 2000 and only present
    for some stations
  • data for organic input present for 2000-2001 and
    very low value for phaeophytine at 2500 m depth
    for the year 2000
  • May be an explanation for the low copepod and
    nematode densities
  • H2O content of the sediment very high at 4000 m
    depth in 2002 just as copepod densities.
  • Linked with other environmental parameters?

7
Results (4)
  • There are indications that
  • Nematode length with depth within the
    sediment, such as width but the ratio L/W also
    with depth which means that deeper sediment
    layers incorporate bigger and more slender
    nematodes.
  • Diversity (N0, N1, N2, ES) from 0-2 cm depth
    and then again to reach the lowest diversity
    at 5 cm depth, N8 reaches its highest point at
    2-3 cm, Taxonomic distinctness from 0 -gt 5 cm
    depth
  • The different depths within the sediment have
    very different nematode communities with
  • 1st cm a Microlaimus and Aegialoalaimus
    dominated community
  • 2nd cm a Dichromadora and Acantholaimus
    dominated community
  • 3d cm a Monhystera and Aegialoalaimus dominated
    community
  • 4th cm a Pareudesmoscolex dominated community
  • 5th cm a Sabatieria dominated community

8
Conclusions and future research
  • The remaining environmental variables that will
    be obtained might tell more about the interannual
    differences in nematode and copepod densities.
  • Meiofauna densities are not enough to
    distinguish the depths along the bathymetrical
    transect in the Arctic deep-sea.
  • gt Further identification and measuring of
    nematodes and copepods will start in the near
    future and should reveal more differences between
    depths and maybe more links between meiofauna
    communities and environmental variables.

9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
What could be the reason of the high H2O content
at 4000m depth in 2002 and is this linked to
other environmental parameters that can explain
the high copepod densities?
14
Global warming
  • Temperature rise of 1-2C/decenium during the
    last 3 decennia
  • An additional temperature rise of 1,5-3C
    expected by 2030
  • Models predict that the global warming will be
    most acute at polar regions
  • Changes in ice extension (2,9 less since 1980),
    in sept 2002 smallest ice extent ever
  • Changes in primary production
  • Changes in global conveyer belt because of
    melting ice, higher precipitation (30 rise since
    1968), changes in atmospheric circulationgt less
    oxygen rich water reaches the deep sea
  • Since 1950 reduction of 20 of Nordish water
    going to more southern regions via its most
    important source (NADW)
  • Chemical changes of sea water (solubility of CO2
    and O2)

15
2 scenarios
  • Higher temperatures gt more primary production gt
    more transport to deep sea gt higher food
    availability
  • BUT phytoplankton blooms can be harmful for
    benthic life
  • Local blooms of species uncommon to the area
    (shift from diatoms to other phytoplankton
    species)gt lower food quality
  • Difference in ice formation gt less nutrients
    transported to surface gt less primary production
    gt less food availability for benthic life

16
1. ENSO (El Niño Southern Oscillation)
  • pressure difference between Darwin (Australia)
    Easter Island (east and west of the Pacific
    Ocean)
  • 2-5 year oscillation
  • influences on Arctic
  • more precipitation
  • big phytoplankton blooms

17
  • 2. AO (Arctic Oscillation)
  • Combination of
  • NAO (North Atlantic Oscillation)

18
minimum ice extent in September (7 million
km²) maximum ice extent in March (14 million
km²)
  • In 1999 the Alfred-Wegener Institute started a
    long term (10 years) sampling campaign of the
    Hausgarten site (79N, North Pole).
  • There are 9 stations along the depth gradient
    (1000-5500 m).
  • The stations are situated along the Ice Margin.

19
  • 2000-2004
  • 3 replicates of stations between 1000-5000m
    along Hausgarten bathymetrical transect.
  • Subsamples of MUC taken with a syringe of 2 cm
    diameter (3,14 cm2)
  • Upper 5 cm divided in 1- cm slices
  • 2003
  • Some extra subsamples with core of 3,6 cm
    diameter (10 cm2)
Write a Comment
User Comments (0)
About PowerShow.com