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| Titel |
Ecological, biogeochemical and salinity changes in coastal lakes and wetlands over the last 200 years |
| VerfasserIn |
Lucy Roberts, Jonathan Holmes, David Horne |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121936
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| Publikation (Nr.) |
 EGU/EGU2016-838.pdf |
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| Zusammenfassung |
| Shallow lakes provide extensive ecosystem services and are ecologically important aquatic
resources supporting a diverse flora and fauna. In marginal-marine areas, where such lakes
are subjected to the multiple pressures of coastal erosion, sea level rise, increasing sea surface
temperature and increasing frequency and intensity of storm surges, environments are
complex and unstable. They are characterised by physico-chemical variations due to climatic
(precipitation/evaporation cycles) and dynamic factors (tides, currents, freshwater drainage
and sea level changes). Combined with human activity in the catchment these processes can
alter the salinity, habitat and ecology of coastal fresh- to brackish water ecosystems. In
this study the chemical and biological stability of coastal lakes forming the Upper
Thurne catchment in the NE of the Norfolk Broads, East Anglia, UK are seriously
threatened by long-term changes in salinity resulting from storm surges, complex
hydrogeology and anthropogenic activity in the catchment. Future management
decisions depend on a sound understanding of the potential ecological impacts, but such
understanding is limited by short-term observations and measurements. This research uses
palaeolimnological approaches, which can be validated and calibrated with historical records,
to reconstruct changes in the aquatic environment on a longer time scale than can be
achieved by observations alone. Here, salinity is quantitatively reconstructed using
the trace-element geochemistry (Sr/Ca and Mg/Ca) of low Mg-calcite shells of
Ostracoda (microscopic bivalved crustaceans) and macrophyte and macroinvertebrate
macrofossil remains are used as a proxy to assess ecological change in response to
variations in salinity. δ13C values of Cladocera (which are potentially outcompeted by
the mysid Neomysis integer with increasing salinity and eutrophication) can be
used to reconstruct carbon cycling and energy pathways in lake food webs, which
alongside reconstructions of salinity and eutrophication can aid the disentanglement of
environmental drivers and increase understanding on the interactions between ecology and
biogeochemical cycles within the lake. Previous palaeolimnological work on the
Thurne Broads system has suggested shifts between macrophyte abundance and loss
within a framework of rising salinity (varying between 1.8-8.7‰ and eutrophication
(phosphorus loading greater than 100μg−1). A complex combination of salinity,
eutrophication, toxicity and associated changes in habitat have acted as drivers for ecological
change over the past 200 years, but these interactions have not previously been
well understood. By combining reconstructions of palaeosalinity, biodiversity, food
web dynamics, redox conditions and eutrophication, the interaction between and
controls on long-term variations in shallow lake environments can be further explored. |
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