Monitoring the Responses of Freshwater Ecosystems to Climate Change - Climate Change Impacts on Freshwater Ecosystems - page 101

Invertebrates
In studies that compared invertebrate communities throughout Europe,
community composition was shown to change with maximum stream temperature,
mean July temperature, and with decreasing latitude and altitude (Lake et al .
2000; Heino 2002; Xenopoulos & Lodge 2006). Temperature affects invertebrate
community composition by influencing species-specific developmental rates and
overall assemblage phenology and by excluding taxa unable to tolerate certain
temperature ranges (Hawkins et al . 1997; Haidekker & Hering 2008). Higher
summer water temperature and low flow result in the progressive replacement of
upstream, cold-water invertebrate taxa by downstream, thermophilic invertebrate
taxa (Daufresne et al . 2004). Benthic invertebrate abundance and diversity
(particularly of Ephemeroptera, Plecoptera and Trichoptera) is predicted to
decrease as a result of changes in water temperature, flow regime, increased
sedimentation and changes in channel morphology, and thus changes in habitat
availability (Lake et al . 2000). Flow regime is another key factor for invertebrate
assemblage structure. From a set of hydrological variables, those associated with
flow had the highest correlation with macroinvertebrate community metrics for
sites in England and Wales (Monk et al . 2006). Leaf litter quality and quantity,
major food sources in small streams, respond also to climate change with coarse
particulate organic matter availability, decreasing with flood frequency. Buzby &
Perry (2000) showed that more than 50% of leaf inputs were exported, leaving
only sparse leaf litter available to invertebrates. Many of these changes are
reflected in the invertebrate community, e.g. by the composition of feeding types
and life history traits (Table 5.2).
The vulnerability of freshwater organisms to the direct and indirect effects of
climate change can be estimated by the ecological preferences of species. Species
may be classified as follows:

Species with limited distribution ('endemic species') are characterized by a
restricted ecological niche and limited dispersal capacity, and are thus more
affected by climate change than widely distributed species (Malcolm et al .
2006; Brown et al . 2007).

●

Species inhabiting large rivers characterized by relatively high water
temperatures are generally physiologically adaptive and may react to globally
rising temperatures by colonizing upstream river reaches; species inhabiting
springs cannot move further upstream and are thus more threatened (Fossa
et al . 2004).

●

Species adapted to low water temperatures ('cold-stenothermic species') are
threatened by climate change more than eurythermic species (compare
Schindler 2001).

●

Insect species potentially endangered by climate change are unevenly distributed in
Europe, but there are also differences between individual insect orders. Three insect
orders provide a case study of the above classification. A database on the distribution
and ecological preferences of European freshwater mayflies (Ephemeroptera),
stoneflies (Plecoptera) and caddisflies (Trichoptera) (www.freshwaterecology.info)