Title: The temporal variation of the meiobenthos along a bathymetrical transect Hausgarten, Arctic: impact
1The temporal variation of the meiobenthos along a
bathymetrical transect (Hausgarten, Arctic)
impact of climatic oscillations Eveline Hoste,
Thomas Soltwedel, Sandra Vanhove and Ann Vanreusel
2Introduction
- Meiofauna (Metazoa 32µm-1mm)
- Arctic deepsea (1500m-5000m)
- Temporal variation in climate includes
- climate change
- climatic oscillations
- 1. ENSO
- 2. AO
- interannual variation
3Objectives
- 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
4Results
- 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
5Results (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
6Results (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?
7Results (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
8Conclusions 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.
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13What 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?
14Global 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)
152 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
161. 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)