An underwater city: Using aquatic plant structures as indicators of invertebrate health

Commonwealth Scientific and Industrial Research Organisation

An underwater city: Using aquatic plant structures as indicators of invertebrate health

Species diversity of underwater plants is frequently used as a proxy for water quality. But what can the structural layout of underwater plants tell us about the aquatic system? Scientists investigate the connection between complex underwater plant growth and thriving aquatic organism communities, which has implications for biologists, waterfront landowners, and decision makers.

Law, A., Baker, A., Sayer, C., Foster, G., Gunn, I. D. M., Taylor, P., Pattison, Z., et al. (2019). The effectiveness of aquatic plants as surrogates for wider biodiversity in standing fresh waters. Freshwater Biology64(9), 1664-1675:

At one point or another, you have likely felt the gripping, animalistic fear of something slimy brushing against your foot while swimming in a lake on a hot summer day. Experiences like this have given underwater plants a bad rap.

Also known as aquatic vegetation, plants that grow from the bottom of lakes and ponds are actually an important part of the underwater ecosystem. They provide food and shelter for some of the smallest underwater creatures like insect larvae, freshwater snails, and clams. These groups of animals, often referred to as macroinvertebrates, support the rest of the life that is found in a lake or pond. Macroinvertebrates can give biologists key information about the overall health of the ecosystem. However, collecting these organisms is time consuming and expensive because they are so small.

There are many species of underwater plants and each has a different growing preference. The result of this is that the plants grow in layers within the water column. This is called structural diversity. The layers give macroinvertebrates many options of where to live and plenty of space to spread out.

Species diversity of underwater plants is often used as a proxy for water quality: the more plant species, the better the water. However, there is little research on if the growing structure of underwater plants can be used as a proxy for the health of aquatic systems. Dr. Alan Law with the University of Stirling and his team of colleagues recently set out to address this gap. The research group used ponds and lakes in the United Kingdom (UK) to investigate if characteristics about underwater plants could reveal patterns in the underwater animal communities around them.

Law and his team found that in ponds across the UK, the diversity of macroinvertebrates could be predicted by the structural complexity of underwater plants. In other words, the more layers of plants that are in the water column, the more macroinvertebrates that will be found there. This means that biologists can study the plant community structure and be able to make estimates about the underwater animal populations – saving both time and money.

While this study’s conclusions were limited to small ponds, their research may have opened the door for further investigations into using underwater plants as aquatic ecosystem proxies. This study only scratches the surface of how underwater plant communities may be able to predict the health of communities in lake ecosystems.

Law’s study has impacts beyond saving the science community time and money. Policy makers, citizen scientists, and waterfront landowners may soon be able to independently investigate the health of their local ponds or lakes just by collecting information on the plants. An approach like this can empower local residents to get involved in sampling and protecting their local resources and provide valuable information to local decision makers.

So next time you’re swimming, and a plant tickles your toes, your first thought may still be fear, but perhaps you can take comfort in the fact that this means the water is healthy and could be home to a diverse ecosystem.