VIRTUE discs - what to investigate?

VIRTUE discs - what to investigate?

On this page, we have gathered some questions that may be useful in working with Virtue racks. Some of the questions may require cooperation with other schools.

Basic questions

How do animals and other organisms colonise new areas?

Place a virtue rack in different environments, for example in two lakes – one small and one larger – or in a sea bay and a marina. Put out and analyse all CDs at the same time. Carefully observe what happens on their surface.

The answer to the question can be developed further by repeating the experiment at different times of the year, and observing differences in fouling between summer and winter.

The results can lead to new questions about how colonisation and transport of species occur. For example, how species spread to new environments and why there are large differences between marine and limnetic (fresh water) species, but also that large difference may be found between racks placed near each other. Another question might be how the colonisation of a surface is affected by the environment.

Read more here: http://ww2.mdsg.umd.edu/interactive_lessons/biofilm/baier.htm

Are there winners and losers in the competition for a surface to settle on?

Study the CDs on a rack over time. Find out which species arrive first, and whether these species are also staying the longest or if other species take over.

Once a virtue disc has been colonised, half the surface can be scraped clean. Then put it back on the rack and see if the same species returns or another one moves in.

Try replacing one or a few discs on a colonised rack with brand new ones. Then see whether the fouling differs compared with the discs that have been scraped clean.

How can the diversity in nature be explained? How come the same species do not dominate everywhere?

Place virtue racks in different environments, for example under a pier in a marina and at a beach. Which CDs have the most similar species? Is the largest difference found between the different environments (places), or are there larger differences within the same place (microenvironments)?

Advanced questions

What does the species composition look like in waters along the (Swedish) coast, or along an environmental gradient?

The salinity varies greatly along the Swedish coastline, and it is interesting to see the variation in species along this gradient. It is also interesting to find out what affects the presence of species. 
Place virtue racks at the same time in different locations along the Swedish coast (or any other coast). Try to select environments that are as similar as possible, but where the salinity differs. Collect the racks at the same time and assess the build-up of organisms.

To find out how salinity affects survival and whether mature organisms or larvae/spores are more affected by for example low salinity, just move the racks and see what happens.

Environmental pollution or salinity – what matters?

For the rivers Nordre Älv and Göta Älv (or other rivers), you can try to find out whether salinity or environmental pollution is more important for the species. In the outlet of Nordre Älv, the salinity is more important, but in Göta Älv both factors have strong effects. A salinity monitor comes in handy in these experiments!

You can also explore other gradients, such as the depth gradient. In this experiment, you can use several virtue racks tied together. After some time in the water, change the depth of a rack to see what happens to the build-up.

Pre-treat the CDs

Naturally fouled virtue CDs can be given different treatments in the lab. For example, you can expose them to different nutrient solutions and different salinity levels. You can also test different anti-fouling paints by painting some CDs and not others, and then placing them in various environments.

It may also be interesting to test exposure to environmental toxins. Are adjacent fouling organisms affected if an anti-fouling treated disc is placed in the same rack? Again, remember to use control discs.
Read more about what happens when a biofilm is formed on a virtue disc in water and how to measure biodiversity. Biofilms and Biodiversity