Navigation Links
TUM scientists document aquatic species decline at dams and weirs

Dams and weirs have a stronger impact on the ecosystem of watercourses than was previously realized. Species diversity in the dammed area upstream of weirs shows a significant decline: the diversity of fish species is one-quarter lower on average, and species diversity among invertebrates is up to 50 percent lower. The interruption of a river course thus has greater effects on the biodiversity than the geological origin of the river itself. Scientists from the Technische Universitaet Muenchen have demonstrated this on the basis of a survey of five rivers in the catchment areas of the Elbe, Rhine/Main, and Danube. Their analysis records, for the first time, both abiotic factors, for example chemical composition, current, and river bed substrate, and biotic factors, such as the number, size, and diversity of all important animal and plant groups on the two sides of weirs. The TUM researchers will present their findings, which have already been published online in the Journal of Applied Ecology, at the annual conference of the German Limnological Society, which takes place from September 12 to 16, 2011.

Whether it is done for the generation of electricity, for flood protection, or collection of drinking water, the damming of a river represents a drastic intervention in its ecosystem. Weirs and dams alter the chemical and physical characteristics of the water and the riverbed. Their construction is accompanied by a clear decline in upstream species diversity, and this is exacerbated by successive damming. This phenomenon, which is known as "serial discontinuity," has now been measured for all important animal and plant groups by system biologists from the TUM for the first time; the information available up to now concerned only individual taxonomic groups or species. The scientists carried out a systematic survey of the aquatic organisms on both sides of the weirs in five rivers of different geological origins. Their survey revealed a significant reduction in the number, biomass and variety of periphyton, invertebrates, and fish species upstream of the weirs. Compared with downstream areas, the diversity of fish species measured upstream of weirs was 25 percent lower on average; a threefold decline in biomass was also observed.

Current-loving fish species, many of which are on the "Red List" of endangered species, are particularly severely affected. "Brown trout, grayling and Danube salmon are demanding fish species that require oxygen-rich water and spawn in coarse gravel areas. As typical residents of the upper reaches of rivers, they are unable to find suitable habitats in dammed areas," explains Juergen Geist, Professor of Aquatic Systems Biology at TUM. "These river sections are often dominated instead by bream, chub, and even carp generalist species that are actually adapted to stagnant waters. The ecological impoverishment of rivers is particularly dramatic when series of dams prevent the sufficient interlinking of different habitat types," says Geist. According to the Bayerische Landesamt fr Umwelt (Bavarian Environmental Agency) there are more than 10,000 weirs in Bavaria's rivers alone.

According to the researchers, the main reason for the species decline is not the impermeability of the barrier to migrating fish species. Instead, the deciding factor is the chemical and physical alteration of the river itself which leads to a reduction of biodiversity. If the current is decelerated or interrupted, the flow rate upstream of the weir declines, and this is accompanied by increased water depth. In all of the surveyed dammed areas, the TUM scientists also recorded major differences in the oxygen content and temperature of the water and the sediment in the river bed, which hinders reproduction in current-loving fish species. The situation is compounded by differences in the structure of the sediments. The particles in the sediment found downstream of weirs are twice as large on average as those upstream, providing more and better quality spawning grounds.

River sections in the direct proximity of weirs should, therefore, be given greater consideration in ecological quality assessments, notes Prof. Geist: "During the evaluation of new weirs or modernization of hydroelectric power plants, attention should no longer be focused exclusively on the migration of fish species, but on the consequences of the structure and function for the river ecosystem as a whole." To ensure this, affected river sections must be covered by the relevant laws or regulations, such as the European Union Water Framework Directive. "A set of instruments for the quantification of the effects of weirs is now available, which records both the quality of the habitat and its biodiversity," says the TUM scientist.


Contact: Undine Ziller
Technische Universitaet Muenchen

Related biology news :

1. Scientists concerned about pesticide education funding
2. Scientists utilise breath and sweat to detect trapped humans
3. USC scientists generate first detailed map of human neuroreceptor
4. USC scientists probe connection between sight and touch in the brain
5. Biomedical/health informatics scientists to present cutting-edge science, health IT
6. Scientists offer way to address age-old questions
7. USC scientists identify key protein linked to acute liver failure
8. Scientists make turfgrass safer for animals, deadly for insects
9. Scripps Research scientists pinpoint shape-shifting mechanism critical to protein signaling
10. New cellular surprise may help scientists better understand human mitochondrial diseases
11. Scripps Research scientists establish new class of anti-diabetic compound
Post Your Comments:
(Date:11/19/2015)... 2015  Based on its in-depth analysis of the ... with the 2015 Global Frost & Sullivan Award for ... presents this award to the company that has developed ... of the market it serves. The award recognizes the ... on customer base demands, the overall impact it has ...
(Date:11/17/2015)... Paris from 17 th until 19 th ... from 17 th until 19 th November 2015.   ... the first combined scanner in the world which scans both ... two different scanners were required: one for passports and one ... same surface. This innovation is an ideal solution for electronic ...
(Date:11/16/2015)... 2015  Synaptics Inc. (NASDAQ: SYNA ), ... announced expansion of its TDDI product portfolio with ... and display driver integration (TDDI) solutions designed to ... TDDI products add to the previously-announced TD4300 ... resolution), and TD4322 (FHD resolution) solutions. All four ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... FRANCISCO , Nov. 24, 2015  Twist ... announced that Emily Leproust, Ph.D., Twist Bioscience chief ... Jaffray Healthcare Conference on December 1, 2015 at ... Hotel in New York City. --> ... . Twist Bioscience is on Twitter. ...
(Date:11/24/2015)... -- Capricor Therapeutics, Inc. (NASDAQ: CAPR ... and commercialization of first-in-class therapeutics, today announced that ... to present at the 2015 Piper Jaffray Healthcare Conference ... The Lotte New York Palace Hotel in ... --> . --> ...
(Date:11/24/2015)... According to two new studies, fewer men are having PSA ... doctors, scientists, and public health experts have been pushing for ... being done, will there be more men dying of ... "Despite the efforts made in regards to early detection for ... of death in men, killing approximately 27,500 men this year. ...
(Date:11/23/2015)... ... 23, 2015 , ... Noblis, Inc., a leading provider of science, technology, and ... Geospatial Intelligence Agency (NGA), has joined the Noblis NSP team as President of the ... intelligence community and the private sector,” said L. Roger Mason, Jr., Ph.D. , ...
Breaking Biology Technology: