Written by: Shelby Paxton
Flatworms, clams, crayfish, leeches, mosquitos, black flies, mites and beetles. It may sound like I’m just listing off random invertebrates, but all these individuals have something in common. they’re all used in Ontario’s Benthos Biomonitoring Network or OBBN for short. This is a group of certified individuals who assess the water quality of lakes, streams, and ponds by analysing the aquatic invertebrates found within water’s sediments . It was developed by Ontario’s Ministry of Environment in the early 2000’s .
So why study these invertebrates? Well, they can be used to determine pollution levels, are inexpensive to gather and study, and they are at the bottom of food chain so differences in their populations will reflect upon species higher up the chain .
But how can invertebrates be used to detect pollution? Different groups of invertebrates are more sensitive to pollution than others, for example, mayflies, stoneflies, and most caddisflies are intolerant to it and can only survive in areas with minimal pollution . Thus, the presence of these groups indicates good quality water. On top of that, an overabundance of some groups such as leeches, aquatic earthworms, and snails, implies higher pollution levels . This is why it is crucial for members of OBBN to be able to accurately identify invertebrates, mistaking a damselfly nymph for a stonefly nymph could be the difference between reporting that a stream has minimal pollution levels when it is actually quite polluted .
Specific invertebrates can be less tolerant to certain pollutants than others, making them key indicators for that pollutant . An example would be scuds and caddisflies, both are especially sensitive to nitrate pollution which is a common result of fertilizer-contaminated runoff from agricultural fields . However, snails are tolerant to additional nitrate in the water so if you tested a stream and didn’t find scuds and caddisflies but gathered plenty of snails, it’s likely that the stream contains high concentrations of nitrate .
So now that you know how OBBN works, how to do you carry out study? First off, you are going to have to prepare to get a little messy since more often than not, you will need to wade around the body of water . Don’t worry though, you won’t be doing this alone, the recommended invertebrate collection method, the travelling kick and sweep, requires that one person holds onto a net while the other person kicks up the sediments into the net . The contents of the net are dumped into a bucket . Afterwards, you take the bucket full of invertebrates back to a lab, identify them, record the information, then release them back into the wild .
There are 2 different ways to analyse the aquatic invertebrates collected: richness, and abundance . Richness is used to study the number of different taxonomic groups (mayflies, stoneflies, worms, etc.) while abundance measures the total number of all invertebrates found . Richness is often the preferred method as different groups of invertebrates indicate different pollution levels while it’s more difficult to draw conclusions from areas that have larger numbers of invertebrates .
On top of working to help the environment, OBBN is also improving the social conditions of its members. Through a survey that the Ontario Ministry of Environment conducted on OBBN members, they discovered that they became more environmentally active within their community, their social capital increased, and their problem-solving abilities improved .
Unfortunately, OBBN is not perfect, there can be confounding factors that influence the species abundance and richness. One of the biggest factors is seasons due to the differences in temperature and water level. For example, despite what you might think, summer is the worst season for OBBN as warmer waters and lower oxygen levels prove to be hostile to many invertebrates, lowering species richness . On the other hand, winter is better for biomonitoring as the species richness is higher and the invertebrates tend to be larger and easier to identify . However, entering a freezing cold stream during the winter can be dangerous. This is why it is crucial to state when a biomonitoring study was done so that researchers can accurately compare the data.
Interested in becoming a certified member of OBBN? Attend one of the following training courses to gain your license and impress your friends by testing water quality using invertebrates: