Monitoring the Responses of Freshwater Ecosystems to Climate Change - Climate Change Impacts on Freshwater Ecosystems - page 99

Increase of
r-strategists

Invertebrate r-strategists
benefit from unpredictable
flood events, e.g. in
summer, which remove
most invertebrates and
thus favour species rapidly
colonizing the competition-
free space.

Number and
discharge of
flood events in
unusual seasons
(recorded by
gauging
stations)

Unusual hydrological
events, e.g. floods in
summer, cause
catastrophic drifts of
invertebrate species and
favour r-strategists.

(x) x x

Changes in life
strategies

If small rivers become
intermittent, species with a
bivoltine or semivoltine life
cycle cannot survive and
the community will change
to univoltine species with
an early emergence period.

Drought periods As gauging stations are

not installed in most small
headwater streams,
drought periods can be
easily recorded by visiting
the respective streams.

(x) x

'Potamalization' -
effects on
invertebrates

Higher water temperature
leads to the disappearance
of species adapted to cold
water temperature and the
associated high oxygen
content, e.g. several
stonefly (Plecoptera)
species. They are replaced
by species typical for
warmer water previously
colonizing more
downstream reaches. Thus,
invertebrate species typical
for small streams ('rhithral')
will be replaced by species
from larger rivers
('potamal').

Share of
invertebrate
taxa preferring
the metarhithral
(trout zone)

Benthic invertebrates are
routinely monitored in
most European countries.
The response of the
invertebrate community
to temperature increase is
reflected by their
longitudinal zonation
preference. The share of
'metarhithral taxa' in an
unimpacted small stream
differs between
ecoregions, but should
typically be around 50%.

(x) x (x)