by Ty Fischer, Riparian Health Restoration Intern

The word “spineless” is often used to describe something weak or purposeless. There is a certain irony, then, that macroinvertebrates – organisms that are “spineless” by their very nature – are actually vitally important in helping humans understand and monitor the health of freshwater ecosystems.

Macroinvertebrates are any organisms that do not have backbones and are large enough to be spotted without the use of a microscope. In aquatic food webs, these creatures undertake the very important roles of grazers and shredders as they break down tough organic matter and make nutrients available for higher trophic levels (Wallace, Webster, 1996). This is an essential function in every healthy ecosystem. 

However, the benefits they provide do not end there. Benthic macroinvertebrates, which are those found at the bottom of streams, rivers, and lakes, have a unique set of traits that make them an asset for freshwater ecologists looking to determine the health of a freshwater body. These characteristics include the fact that they are mostly immobile (Cook, 1976), they are diverse and widespread (Armellin, 2010), they are very sensitive to environmental changes (Hutchinson et al., 1998), and they have a relatively long lifespan (Pratt, Coler, 1976). Together, all these attributes make benthic macroinvertebrates highly representative of the surrounding ecological conditions and, most importantly, able to integrate and exhibit the combined effects of any environmental changes that arise (Li, Liu, 2010).

This makes macroinvertebrates excellent ‘bioindicators’. Bioindicators are living creatures that contain valuable information on the quality of the environment (Li, Liu, 2010), and they are frequently used in biomonitoring studies in which such organisms and their responses are used to detect changes to the local environment (Oertel, Salanki, 2003). As excellent bioindicators, benthic macroinvertebrates are extremely useful for monitoring freshwater health because they can show the combined effects of multiple stressors, such as eutrophication, toxicity, invasive species, or habitat degradation, all at once (Armellin, 2010). In this way, conducting a macroinvertebrate biomonitoring study can provide an overarching view of the health of the entire ecosystem.

Macroinvertebrate biomonitoring is not only a useful tool but a necessary one in order to accurately assess the health of rivers and streams, some of the most endangered ecosystems worldwide (Malmqvist, Rundle, 2002). This is because rivers and streams undergo frequent and rapid changes in their hydrology which makes physical, chemical, and bacteriological water quality measurements far less indicative than they are in still bodies of water such as lakes (Li, Liu, 2010). In other words, in running waters, water quality measurements provide but a snapshot in a series of ever-changing conditions and therefore an incomplete spectrum of information on the health of these aquatic ecosystems. This is why benthic macroinvertebrate biomonitoring is so important; it provides us with information about the long-term status of these especially at-risk areas that cannot be afforded to us by typical water quality testing. 

So, what is involved in a biomonitoring study? In a general sense, these studies consist of collecting a sample of macroinvertebrates in the river or stream of interest, identifying the constituents, and returning at a later date to repeat the process and see if the composition of the community has changed. One of the most important varieties of macroinvertebrates that researchers note in samples are the larval stages of various insects, including those of dragonflies, mayflies, caddisflies, and mosquitoes, since these are especially sensitive to environmental changes (Armellin, 2010). 

Researchers look for three main types of responses in these communities: a reduction in diversity between different species, dominance by one specific species, and a reduction in the size of the dominating species (Li, Liu, 2010). Observing such a response can be a clue that a specific change to the water quality has occurred. For example, in streams and rivers that have excessive organic matters of heavy metals, the species richness and diversity of the macroinvertebrate community is reduced, while Chironomidae (non-biting midges) become dominant over the more sensitive groups such as stoneflies, caddisflies, and mayflies (Li, Liu, 2010). In short, the effects of these pollutants in rivers and streams are expressed in the local populations of macroinvertebrates, but only if you know what to look for.

Of course, successful biomonitoring relies on accurate species identification (Hajibabaei et al., 2011). The classical approach to species identification relies on recognizing morphological features – physical characteristics of certain species – using a set of resources such as identification keys. This can however be difficult to do accurately and consistently (Hajibabaei et al., 2011). That is why researchers in Canada have started looking into an entirely new approach to identifying benthic macroinvertebrates collected in biomonitoring studies: DNA metabarcoding. In this approach, samples of macroinvertebrates that are collected in the field are extracted, amplified, and compared against an international DNA database to identify which species are present (Hajibabaei et al., 2011). Since it is far more accurate, consistent, and timely, implementing it improves the efficiency of such projects greatly and therefore expands their possibilities. This new approach is so important that a project has been developed here in Canada called STREAM (Sequencing The Rivers for Environmental Assessment and Monitoring) which has the specific goal of advocating for DNA metabarcoding to be the most common approach for generating biodiversity data in our freshwater ecosystems while breaking down barriers for community science groups to use it. 

In conclusion, macroinvertebrate biomonitoring projects are an incredibly impactful tool. Combined with DNA metabarcoding technology, they have the power to transform our ability to assess, monitor, and treat problems in our freshwater ecosystems which will provide benefits for us and our wildlife that will stretch far into the future. If you are interested in getting involved in these important projects yourself, there are many opportunities across Canada. Living Lakes Canada, an award-winning non-government organization that originally co-delivered the STREAM program, provides internship or volunteer opportunities in community-based water monitoring initiatives, in addition to training for countless organizations across the country to allow them to do the same. Connect with Living Lakes Canada or see if there is one of their partner organizations in your area – they can almost always use a helping hand! 

 

Sources

Armellin, A. (2010). Benthic macroinvertebrate communities: an indicator of ecosystem health and water quality in Lake Saint-Pierre. Environment Canada. Accessed from: https://publications.gc.ca/site/eng/383293/publication.html
Cook, S.E.K. (1976) Quest for an index of community structure sensitive to water pollution. Environmental Pollution, 11: 269-288.
Hajibabaei, M., Shokralla, S., Zhou, X., Singer, G. A., & Baird, D. J. (2011). Environmental barcoding: A next-generation sequencing approach for biomonitoring applications using River Benthos. PLoS ONE, 6(4). https://doi.org/10.1371/journal.pone.0017497
Hutchinson, T.H., Solbe, J. and Kloepper-Sams, P.J. (1998). Analysis of the ecetoc aquatic toxicity (EAT) database III-Comparative toxicity of chemical substances to different life stages of aquatic organisms. Chemosphere, 36(1): 129-142.
Li, L., Zheng, B., & Liu, L. (2010). Biomonitoring and bioindicators used for river ecosystems: Definitions, approaches and Trends. Procedia Environmental Sciences, 2, 1510–1524. https://doi.org/10.1016/j.proenv.2010.10.164
Malmqvist, B., & Rundle, S. (2002). Threats to the running water ecosystems of the world. Environmental Conservation, 29(2), 134–153. https://doi.org/10.1017/s0376892902000097
Oertel, N., & Salánki, J. (2003). Biomonitoring and bioindicators in aquatic ecosystems. Modern Trends in Applied Aquatic Ecology, 219–246. https://doi.org/10.1007/978-1-4615-0221-0_10
Pratt, J.M. and Coler, R.A. (1976) A procedure for the routine biological evaluation of urban runoff in small rivers. Water research, 10: 1019-1025
Wallace, J.B. and Webster, J.R. (1996). The role of macroinvertebrates in stream ecosystem function. Annual Review of Entomology, 41: 115-139.