The Presentlatest Holocene zoobenthos foraminifera records in Lake Qarun, Egypt

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The Present-latest Holocene zoobenthos
(foraminifera) records in Lake Qarun, Egypt
Ramadan Abu-Zied1, K. Keatings2, A. Zalat3 and R.
Flower2 1 Geology Department, Faculty of Science,
Mansoura University 2 ECRC, University College
London 3 Geology Department, Faculty of Science,
Tanta University
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Location of the studied sediments
Q5
Map of Lake Qarun with the location of all coring
and surface-sediment sampling sites.
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Objectives

• Discover the structure, composition of the
  benthic foraminiferal ecosystem in sediments of
  the lake.
• Compare each species of these ecosystem with the
  prevailing ecological variables salinity
  changes, organic matter (anthropogenic
  materials), dissolved oxygen and water depth.
• Reconstruction the paleoecological changes in the
  studied core, based on the modern analogue.

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Results

• About 15 species recorded in the surface sediment
  samples of the lake, then this number decline in
  the core materials to three species
• Ammonia tepida, Quinqueloculina lata, and
  Elphidium excavatum are the most abundant taxa in
  the surface and core materials
• There is no much deformation in the foraminiferal
  shells
• All ontogenetic stages of the species present and
  tests are mostly intact indicating no signs of
  significant transport or sorting.

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The Island
East
West
Census data of benthic foraminifera from the
surface samples, Lake Qarun.
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Favorable ecosystem
Sample 3 (east of the Island)
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Favorable ecosystem
Sample 11 (near the Island)
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Stressed ecosystem
Sample 6 (west of the Island)
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Background about the species

• All the recorded species present today all over
  the world in hypo-to hypersaline lagoons,
  shallow-normal marine waters or in shallow
  brackish marine waters.
• Ammonia tepida is euryhaline cosmopolitan
  species, tolerant for a wide range of salinity
  variations. Laboratory experiments indicated that
  such species reproduce only between 13 and 40 .

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• Ammonia tepida never found in an ephemeral lake
  subjected to complete dryness during summer as
  does Elphidium (Cann and Deckker, 1981).
• Occurrence of Brizalina striatula in our records
  is interesting, as it occurs today in
  Mediterranean Sea under areas of high organic
  matter flux. It occupies different levels in the
  sediments tracking the summer stratification.

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Conclusion and future work

• The presence of Ammonia tepida in the lake
  sediments (grab samples and core) indicate that
  the interval scanned by the core (140 cm) must
  have had saline water no less than 10, then
  increases gradually reaching the present-day
  levels (35-40 ).
• Absence of Elphidium excavatum from the surface
  sediments of the western side (deepest parts)
  could be related to the development of dysoxic
  environments there as indicated by the presence
  of Brizalina striatula.

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• Occurrence of Rosalina bradyi (epiphytic taxon)
  in the present-day sediment and the upper part of
  the core could be related to the presence of
  seagrasses and phytal remnants.
• Future Work
• Increase the resolution of the studied materials.
• Find out any ecophenotypes (formae) variations
  within each predominant species. Such variations
  could be useful for any paleo-environmental
  inferences.

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Thank you