Freshwater rivers are home to a wide range of animals, such as mammals, birds, amphibians, and many smaller organisms like invertebrates, crustaceans, and macrophytes. The rivers are used as a source of food, a breeding ground, and a refuge from predators.

With so many organisms relying on our rivers for survival, it is essential that they are kept in good health. However, increasing levels in pollution from sewage leakages and agricultural run off have caused the health of our rivers to dramatically decline.

One way to check the health of our rivers is to perform invertebrate surveys, assessing the range of species and number of organisms present. The species found can act as bioindicators of the state of the aquatic system, with certain groups having different tolerances to pollution. Each species group has been assigned a score relating to this tolerance. For example, worms and midge larvae have low scores, meaning they cope well with pollution. On the other hand, cased caddisfly larvae and freshwater shrimp have higher scores, with lower pollution tolerances. Using the number of species found and their correlating score, the biotic index of the river can be calculated.

We recently completed a freshwater invertebrate survey in the River Dore which runs along the boundary of Turnastone Court Farm. We used kick sampling, a method in which the riverbed is disturbed by dragging one foot across the bottom, dislodging rocks and debris, and allowing any organisms present to be caught by an awaiting net. The contents of the net are placed into a tray of water and a spoon can be used to carefully place the animals into a magnifying container for better identification.

Four samples were taken from varying points on the river with over 228 individuals collected from nine species groups. Some of the organisms found were Freshwater shrimp, Water beetles, and Swimming mayfly nymphs. A biotic index was calculated for each of the four samples, with the average for the river coming to 4.87, with 0 suggesting no life was present in the river and 10 indicatives of a very clean river free of most pollutants. This score suggests that the river is of average water quality, with some pollution present in the water.

It is vital that our rivers are freed of pollution to continue to support the variety of life that depends on them for survival. Many of the actions we perform on land end up impacting the aquatic systems through leaching and run off. Diffuse pollution from agricultural sources such as pesticides and animal waste accumulate over time and causes the nutrient enrichment of rivers. Despite sounding positive, this process has a great negative impact on our water systems. The excessive nutrients like phosphorus and nitrogen cause extreme plant and algal growth, decreasing levels of dissolved oxygen and causing hypoxia in fish and other aquatic life. This can also cause an increase in nuisance species and diseases.

All aquatic life in our rivers, lakes, and streams are under threat from pollution due to human activity. It is essential that pressure is put on government bodies for action in this area, to regulate the leaching of sewage into our water systems and introduce stricter methods of waste disposal in the agriculture sector. Hopefully, with these changes we will see the health of our rivers improve and future surveys will show an increase of low tolerance species. We would love to see the biotic index of the River Dore increase!