Hyperbenthos in the upper reaches of
the Scheldt estuary (Belgium):
an indispensable trophic link re-established
Erika van den Bergh
Hyperbenthos?
•
A group of typically small organisms that live in the lower layers of the
water column, just above the bottom
o Peracarida
- Mysida (opossum shrimps)
- Amphipoda
- Isopoda
o Decapod shrimps (epibenthos)
o Juvenile fish
•
Good estuarine ecosystem quality indicators
The Netherlands Belgium North Sea Antwerpen Vlissingen POLYHALINE MESOHALINE FRESHWATER Gent Melle Durme OLIGOHALINE
Scheldt estuary
• 1950-1980 permanent hypoxia, recurrent anoxia no life • 1980-2007 steady improvement of water quality macrobenthos boom & waterbirdssince 2007
zooplankton,
Aims
freshwater tidal zones are poorly studied and understood in Europe, the
upper reaches of the Scheldt estuary offer a quite unique study system
Intensive monitoring campaign in the mesohaline to freshwater tidal zones of the Scheldt estuary
- Document recovery of hyperbenthos community after decades of absence
- How do hyperbenthos communities vary in space and time?
- Which environmental variables drive spatio-temporal patterns?
Variables
Evironmental
•
Temperature (°C)
•
Conductivity (µS/cm)
•
DO (mg/l)
•
SPM (mg/l)
•
POM (mg/l)
•
River discharge
•
5days before (m³/s)
•
Preceding season (m³/day)
Species richness
Redundancy Analysis (RDA)
Seasonal variation
Focal species
>20% of the samples
>0.1 on at least one RDA axis
Total abundance
Total abundance
Total abundance
Osmerus eperlanus (European smelt)
Total abundance
Neomysis integer
Effect of river discharge
seasonal pattern most apparent in latter, dry, yearsnegative relation to short-term river discharge flushing
lower short-term residence time
Take home message
1. Hyperbenthic communities successfully recovered in the upper reaches of
the Scheldt estuary after decades of absence
2. A trophic link in the food web was re-established, adding to the estuarine
ecosystem resilience
3. Oligohaline and freshwater tidal areas can represent a valuable extension of the nursing and feeding grounds for marine and estuarine fish and shrimps, 4. Short intense peaks of high river discharge as well as long lasting periods of
