 |
| Titel |
Phenology changes in the mayfly Ephemera danica in response to water temperature variations in the River Dove, UK |
| VerfasserIn |
Matthew Johnson, Nicholas Everall, Robert Wilby |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106692
|
| Publikation (Nr.) |
 EGU/EGU2015-6372.pdf |
|
|
|
|
|
| Zusammenfassung |
| Water temperature in rivers is critical to aquatic life. Climate and environmental change can
elevate river temperatures to levels that stress fish, but impacts on other aquatic organisms are
not well understood. In particular, rising temperatures are expected to alter the
phenology of aquatic insects at levels substantially below those required to stress fish
species.
The phenology of the mayfly Ephemera danica, a large burrowing species that is
widespread throughout Europe, is known to be sensitive to temperature change. To assess the
temporal and spatial variability in mayfly emergence, E. danica were monitored at two
reaches in the River Dove, English Peak District over the period 2007 to 2013. Variations in
Growing Degree Days (GDDs) were modelled for an upstream site with an annual
temperature range in excess of 15 Ë C (Beresford Dale) and a downstream site, dominated by
near constant discharges of cool groundwater with an annual range less than 8 Ë C
(Dovedale).
The emergence of E. danica was strongly related to GDDs at each site. E. danica
usually remains in an aquatic larval stage for two years before emerging in its adult,
terrestrial form. However, after particularly warm summers in Beresford Dale, E.
danica was recorded to emerge after only one year in its aquatic form. Following the
particularly wet/cold year of 2012, E. danica began to revert back to a bi-annual cycle.
In Dovedale, an average of 374 fewer GDDs were accumulated in comparison to
Beresford Dale. As a result, E. danica maintained a two-year growth cycle throughout
the monitoring period despite the phenology changes observed 8 km upstream at
Beresford.
Changes to insect phenology are significant because populations with a one-year cycle are
potentially more vulnerable to adverse weather when the majority of the population is in
terrestrial form. Also, altering the growth, development and size of insects affects
reproductive success with implications for population dynamics. Data from the present
study suggest that habitats near cool groundwater may provide important refugia for
populations of insects, potentially delaying permanent shifts in phenology under climate
change.
Conventional monitoring of both water temperature and invertebrates, as used by
regulatory authorities in the UK, did not identify the changes in insect phenology or the
association between phenology and water temperature. Therefore, new monitoring strategies
are required in order to identify important changes in aquatic populations in response to rising
temperatures. |
|
|
|
|
|
|