VIRTUE discs - what to investigate?

updated: 2020-11-15

On this page, we have gathered some research questions that may be useful in working with VIRTUE racks. For some of the questions (particularly those that explore geographical differences) it may be useful to cooperate with other schools.


Basic questions

How do animals and other organisms colonise in different ecosystems?

Place VIRTUE racks in different environments, for example in two lakes – one small and one larger – or in a sea bay and a marina. Retrieve and analyse all discs at the same time. Carefully observe what happens on the upper and lower surfaces.

The investigation of 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.

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 about Initial Events in Microbial Film Formation (pdf)

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

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

Does it matter when the discs are deployed?

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

Is the type of substrate important?

To find out if the actual material of a disc makes a  difference, or if previous fouling on a disc influences new fouling, use different materials (e.g. metal, wood, glass) or 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? Why don´the same species dominate everywhere?

Place VIRTUE racks in different environments, for example under a pier in a marina and at a beach. Which discs 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)?

Depth and light

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.

Advanced questions

What does the species composition look like in waters along a coastline, or along an environmental gradient?

The salinity or nutrient content of the water may vary with location and it is interesting to see the variation in species along gradients of these properties. It is also interesting to find out what affects the presence of species. 
Place VIRTUE racks at the same time in different locations along a coastline. Try to select environments that are as similar as possible, but where the salinity or nutrients differ. Collect the racks at the same time and assess the build-up of organisms.

To find out how e.g. 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. (Note, however, that factors like salinity or the presence of larvae may also vary in time, so in repeating an experiment some time later you may no longer have the same environmental conditions!)


Pre-treat the discs

Naturally fouled VIRTUE discs 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 discs 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.

Watch these VIRTUE videos and learn what happens when a biofilm is formed on a VIRTUE disc in water and how to measure biodiversity with VIRTUEs Biodiversity Calculator.