ABOUT THE PROJECT
Climate scenarios of the IPCC for the Central European area expect that the
climate will warm up in all seasons. Global warming has already shown impacts on European freshwater ecosystems and the services they provide to
humans. Main goal of the project is to understand and define the mitigation effect of riparian vegetation against adverse effects to benthic invertebrate and fish communities . Our aim is to assess the habitat characterization for key fish and invertebrate species which is closely linked to temperature characteristics.
This should contribute to support river managers in sustainable river restoration towards climate change adaptation, ecological services and socio-economic consequences.
Caddisflies (Trichoptera) on
submerged wood grayling from Lafnitz
Zingel from the Lafnitz Juvenile barbel from the Lafnitz
Electrofishing in the Lafnitz
Assessment of water temperature effects and aquatic habitat on fish and benthic invertebrates
Pablo Rauch (IHG BOKU, Austria, pablo.rauch@boku.ac.at), Florian Dossi, Wolfram Graf, Martin Guldenschuh, Patrick Leitner & Andreas Melcher (IHG, BOKU Vienna), Heidi Trimmel, Philipp Weihs (MET, BOKU Vienna), Gerda Holzapfel, Hans-Peter Rauch (IBLB, BOKU Vienna)
y (August) = 2,6208x + 1,3592 R2 = 0,9644
y (Juli) = 2,5036x + 1,2957 R2 = 0,9647
10 11 12 13 14 15 16 17 18 19 20
3 3,5 4 4,5 5 5,5 6 6,5 7
Fischregionsindex (FRI)
Mittlere Wassertemperatur [°C]
Modell August Modell Juli
Linear (Modell August) Linear (Modell Juli)
Barbel zone m.Temp:
16.8 Trout zone
mean Temp: 12.8
Grayling zone m.Temp: 13.5
Bream zone m.Temp: 18.8
Meanwatertemperaturein °C
Fish Zone Index 0
9
52 32 26 18
68
87 100 0
11 20
32 39
61 Pinka44
Lafnitz
Lafnitz - Wolfau (~km 52) Lafnitz - Neustift (~km 35)
Pinka - near Pinkafeld (~km 25) Pinka - Oberwart (~km 39)
LAFNITZ PINKA
Fig. 3: Abiotic characterization of the Lafnitz (left) and Pinka (right) and longitudinal changes. Variables depth, flow velocity and substrate (0=mud, 6=large rocks) are the most important microhabitat features for fishes and benthic invertebrates.
RESULTS
- Modelling fish habitat preferences with logistic regression allowed to calculate the potential habitat (Fig.4). Both Lafnitz and Pinka serve only very limited habitat for grayling. Both rivers provide habitats for spawning of barbel and nase but juvenile habitats are limited (Fig. 4).
- While the number of exclusive lithal invertebrate taxa is decreasing with river length, the number of xylal taxa found exclusively on deadwood structures is increasing with river length (Fig. 5).
- Biocenotic indices for both fish and invertebrates show a strong correlation with water temperature in the longitudinal gradient (R²=0.975) at the Lafnitz. Notably, temperature and index values are increasing strongly throughout the first 50 km (trout and grayling zones) and remain high and relatively stable throughout the rest of the river course (barbel zone).
0%
20%
40%
60%
80%
100% lower Pinka
0%
20%
40%
60%
80%
100% upper Pinka
0%
20%
40%
60%
80%
100% lower Lafnitz
0%
20%
40%
60%
80%
100% upper Lafnitz
Fig. 4: Potential habitat for key fish species nase (Chondrostoma nasus), barbel (Barbus barbus) and grayling (Thymallus thymallus) expressed as share of total avail- able habitat in upper and lower reach of the Lafnitz and Pinka (cut values at 40 km at the Lafnitz and 29 km at the Pinka).
no habitat habitat
0 5 10 15 20 25
0 1 2 3 4 5 6 7
0 20 40 60 80 100
Water temperature (°C)
Biotic Indexvalue
Distance from source (km)
trout zone grayling
zone barbel zone
Fish Index Benthic Index
Water temperature
Temperature effects on riverine biota
Fig. 6: Relation of water temperature (7 a.m. summer maxima) with biotic indices for fish (Fish zonation index) and benthic invertebrates (River zonation index). Both indices are based on species inventory at sampling sites.
Fig. 2: Mean summer water temperatures for Austria’s fish
zones with corresponding fish zone index. Data from 200 unimpacted sites in an average year (2000)
Fig. 1: Rivers Lafnitz and Pinka with sampling sites and corresponding distance from source in km.
R² = 0,2999
0 2 4 6 8 10 12
0 20 40 60 80 100
Number of lithal taxa
Distance from source (km)
R² = 0,6319
0 2 4 6 8 10 12
0 20 40 60 80 100
Number of xylal taxa
Distance from source (km)
Fig. 5: Exclusive xylal (on submerged wood) and lithal (on rock) species in longitudinal gradient. Data from river Lafnitz.
DISCUSSION
- Temperature is a crucial factor for biotic assemblages in riverine ecosystems.
- Increasing temperature induced by climatic changes may cause shifts of fish or invertebrate communities leading to reduced habitat availability and even extinction of cold-adapted species.
- Different types of habitats are needed for different species or life stages.
- Riparian vegetation has an important role for the ecological integrity by buffering climate change effects and providing direct and indirect habitats for fishes and benthic invertebrates
University of Natural Resources and Applied Life Sciences, Vienna / Department of Water, Atmosphere and Environment / Institute of Hydrobiology and Aquatic Ecosystem Management Max Emanuel Straße 17, 1180-Wien / Contact: Pablo Rauch - Tel.: +43 (0)650 6212840 - email: pablo.rauch@boku.ac.at
STUDY SITE & METHODOLOGY
The study is conducted at two rivers in the south-east of Austria, the Lafnitz and Pinka (Fig.1). Both are located in the Hungarian Plains ecoregion. This lowland region is subject to the highest future temperature increase in Austria (2 - 2.5°C until 2040).
At different sections along the river course samples were taken:
- point measurements of depth, flow velocity, substrate type, temperature, shading, etc. (Fig. 3)
- fish samples using the electrofishing method
- sampling of benthic invertebrates on the riverbottom and deadwood structures
The aim is to identify important variables for key species and their response to temperature effects.
