Experimenting with ecosystems

Birth of radioecology

When we think of a nuclear accident, an atomic bomb or cosmic rays, our first concern is often not the environment. The majority of radiation protection policies are aimed at conserving human life and minimizing human exposure to radiation. The increasing efforts against climate change and pollution during the last decades has made many recognise the need to study radiation impacts on the environment. This resulted in the birth of radioecology. This field has greatly expanded, with large research bodies around the world studying the impacts in our environment. However, majority of these studies are still limited to determining effects on single species.

Ecosystem approach

During the 1960’s, many researchers observed chronic effects of pollution, in organisms at higher levels of the food chain. This observation puzzled them, as their assessments were not predicting any effect in these organisms. Further research showed that this effect was due to accumulation of the toxin in the food chain. Imagine for example, a pesticide is sprayed on a field with crops. It is then washed into soil, where earthworms can ingest this toxin in small quantities. Birds, which feed on earthworms eat many earthworms, effectively doubling and tripling the concentration of the pesticide in their own bodies. This accumulation is the indirect effect of environmental pollutants. Food chains are only one example of how important it is to study an ecosystem as a whole. In ecosystems, all organisms are connected one way or another. There are large gaps in our knowledge on how radionuclides travel through ecosystems and how radiation effects them. Ecosystem approach advocates for use of appropriate scientific methods, which are focused on levels of biological organization. The experiments should take into consideration the essential processes, functions and interactions among organisms and their environment.

Let’s experiment!

Ecosystem approach is the inspiration behind our latest research project. We aimed to create a small ecosystem, expose it to radiation and measure any direct and indirect impacts in the system. We created small aquariums or microcosms as they are termed in the science world. They were filled with sediment, fresh water, two types of plants, a small crustacean, which is often used as a study species, snails and two types of algae. We also sank small litter bags (a teabag with some collected fallen leaves) that introduced a microbacterial community to make the systems more natural. For several months prior to the exposure, these systems were tested and showed to be stable for long periods of time. A natural ecosystem developed in the aquariums and communities survived. The plants produced oxygen for the aquarium, the snails fed off plants and microorganisms, and the crustaceans fed on the algae. Reproduction followed soon.

Experimental aquariums set up for exposure

Experimental aquariums set up for exposure

Photo
Tanya Helena Hevrøy
In October 2016, we set up an experiment in Figaro. Figaro is a hall 20 meters long and 4 meters wide. It has a cobalt source at one end, which releases a beam of gamma radiation when opened. The distance to the source determines the strength of the dose one receives. Aquariums were placed at a variety of distances to determine if any effects could be measured at various doses. For one month, these systems were continuously exposed, as different parts of the aquariums were sampled several times a week.  We were measuring photosynthesis, grazing rates of animals, water quality and chemistry, cell damage, growth rates, reproduction and more.

At the end of the experiment, we dismantled all of the aquariums, keeping every part of them for further analyses. This analyses is what we are now working on. Twenty-five aquariums, tested twice a week for 4 weeks across numerous endpoints results in a LOT of data. We have a large job ahead of us, but we are hopeful that these results will give us a better insight into the effect of radiation in an ecosystem and open our minds to further research opportunities and questions. Because what is science if not the constant perusal of knowledge and unanswered questions?!

Photo on the top: Anna-Lea Golz sampling from the aquariums

Published 30. November 2016 - 11:04 - Updated 28. November 2018 - 10:58

Norwegian University of Life Sciences (NMBU)

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