Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

What the size distribution of organisms tells us about the energetic efficiency of a lake

05.06.2018

The size distribution of organisms in a lake facilitates robust conclusions to be drawn on the energy efficiency in the food web, as researchers from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) and international colleagues have now demonstrated empirically. This relationship enables scientists to gain a better and more direct understanding of biological processes and disturbances that impact aquatic ecosystems.

Any single habitat is only able to accommodate a certain number of large organisms because these must feed on smaller creatures. In ecology, this connection is described by the trophic transfer efficiency (TTE): around ninety per cent of energy is lost from one level of the food chain to the next or, in other words, only ten per cent remain.


Divided experimental lake in Brandenburg, Germany.

Photo: TERRALAC

If, for example, a bird of prey devours a rabbit, it can use only ten per cent of the energy, which the rabbit needed to grow and live, to increase its own weight – most of the energy, then, is lost. IGB researchers have now examined how large this important model parameter actually is in natural lake ecosystems, and how it relates to the population density of organisms of different size groups.

“Of course, investigations have already been carried out into the trophic transfer efficiency and size distribution, but they were on a smaller scale than our study: we analysed all trophic levels, from bacteria to large fish,” states Dr. Thomas Mehner, lead author of the study and head of the Food Web Ecology and Fish Communities Research Group at IGB.

Available food is utilised less efficiently than expected

The researchers’ study involved investigating food webs in two small, shallow and nutrient-rich lakes in Northern Germany, each of which divided into two closed systems for a period of one year by installing a curtain through the middle of each lake. The long period of division meant that the key groups of organisms developed differently in both halves, enabling the scientists to collect data for a total of four different aquatic ecosystems.

The researchers determined the biomass and size of all organisms present in the lakes. In addition, the team computed the trophic transfer efficiency for all levels of the food chain in the lake. To achieve this, they compared primary and bacterial production with secondary production (i.e. the increase in biomass at the consumer level).

“We found out that energy efficiency is lower than is generally assumed: namely, well below ten per cent. In other words, available food is utilised much less efficiently than expected,” reports Thomas Mehner. The TTEs determined in all four lake systems were more or less equally low.

However, the predictions of the ecological theories with respect to the connection between the TTE and size distribution were confirmed: when the trophic transfer efficiency falls below ten per cent, this corresponds to an increasingly steep declining curve in the model. Consequently, the biomass of the larger organisms also declined more strongly than expected in all four lake halves. For example, the researchers counted considerably fewer consumers in the water than would be expected in the case of a higher TTE.

Using size distribution in lakes as a “tool”

The fact that the relationship between the trophic transfer efficiency and size distribution is stable opens up new possibilities concerning the investigation of aquatic ecosystems. Rather than taking great pains to identify the TTE, it presumably suffices to measure population densities and size distributions. “The trophic transfer efficiency is an important parameter, but we often do not know the size of this parameter.

We were able to show that the size distribution, which is easier to determine and more commonly applied, might be sufficient for evaluating the energetic state and efficiency of an ecosystem,” Mehner summarises the relevance of the findings. As a result, the size distribution can be used as a “tool” for gaining information such as on the impact of global warming, the invasion of alien species, habitat changes or human exploitation of ecosystem functions.

Read the study in the journal Ecology > https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.2347

Mehner, T. , Lischke, B. , Scharnweber, K. , Attermeyer, K. , Brothers, S. , Gaedke, U. , Hilt, S. and Brucet, S. (2018) Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra. Ecology, 99: 1463-1472. doi:10.1002/ecy.2347

Contacts:

PD Dr. Thomas Mehner, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department 4 Biology and Ecology of Fishes, +49 (0)30 64181 613, mehner@igb-berlin.de

Katharina Bunk, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Public Relations, +49 (0)30 641 81 631, +49 (0)170 45 49 034, bunk@igb-berlin.de

About the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB):

Work at IGB combines basic research with preventive research as a basis for the sustainable management of freshwaters. In the process, IGB explores the structure and function of aquatic ecosystems under near-natural conditions and under the effect of multiple stressors. Its key research activities include the long-term development of lakes, rivers and wetlands under rapidly changing global, regional and local environmental conditions, the development of coupled ecological and socio-economic models, the renaturation of ecosystems, and the biodiversity of aquatic habitats. Work is conducted in close cooperation with universities and research institutions from the Berlin-Brandenburg region as well as worldwide. IGB is a member of the Forschungsverbund Berlin e.V., an association of eight research institutes of natural sciences, life sciences and environmental sciences in Berlin. The institutes are members of the Leibniz Association. http://www.igb-berlin.de/en

Weitere Informationen:

http://www.igb-berlin.de/en/news/what-size-distribution-organisms-tells-us-about...

Katharina Bunk | idw - Informationsdienst Wissenschaft

More articles from Ecology, The Environment and Conservation:

nachricht 100 % Organic Farming in Bhutan – a Realistic Target?
15.06.2018 | Humboldt-Universität zu Berlin

nachricht When corals eat plastics
24.05.2018 | Justus-Liebig-Universität Gießen

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Carbon nanotube optics provide optical-based quantum cryptography and quantum computing

19.06.2018 | Physics and Astronomy

How to track and trace a protein: Nanosensors monitor intracellular deliveries

19.06.2018 | Life Sciences

New material for splitting water

19.06.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>