Invertebrate Sampling
Benthic Macroinvertebrates
The term benthic means, “bottom dwelling” and refers to the organisms that live in, crawl, attach themselves to the bottom or the substrate in our rivers and streams. Macroinvertebrate refers to those invertebrates that can be seen with the naked eye. The benthic macroinvertebrate community is a major component of the aquatic ecosystem and forms a critical link between water and the fish community. These organisms play key roles in shaping components of the river ecosystem, and the food chains that support a healthy river (e.g. nutrient cycling).
Benthic macroinvertebrates are an important group of organisms to study because many are sensitive to physical and chemical changes in the watercourse. Their relative immobility means they cannot easily escape the impacts of thermal, chemical or organic pollution. Due to the species relative immobility when compared to that of the fisheries community, species can be more directly tied to site-specific habitats, and are therefore more reflective of the health of that specific habitat location. These organisms help us to better understand the health of our river and streams, and the processes that maintain them.
Benthic macroinvertebrates are easily collected in the watercourses in which they exist. The methodology that Citizen Scientists uses to collect benthic macroinvertebrates is outlined in the Ontario Stream Assessment Protocol (OSAP). This methodology maximizes reproducibility between years as the sample site boundaries are fixed, and provides a more comprehensive picture of benthic community, as sampling is conducted in all stream microhabitats (e.g. riffles, pools, glides, stream edges). A D-framed net is used to collect the sample, and we follow a traveling kick and sweep methodology. For some benthic macroinvertebrates it is necessary to undertake more targeted sampling using different methods of collection, because the OSAP methodology does not adequately survey their habitat type. For instance, crayfish and freshwater mussels are two groups of organisms where different sampling methods need to be employed to accurately characterize their species distribution and abundance in the river. In these cases, Citizen Scientists uses alternative methods for data collection.
Citizen Scientists collects benthic macroinvertebrate information twice a year, from June to October at each monitoring site. The benthic macroinvertebrate data that is collected is analyzed at two different taxonomic levels, one at a high level and one at a low level. The lower level taxonomy is conducted because the utility of the benthic macroinvertebrate data is greatly enhanced when identification is carried out to their lowest practical taxonomic level (i.e. genus/species). Typical macroinvertbrate analysis is carried only at a high level of taxonomy (typically Order). Within an individual order there can be hundreds, perhaps thousands of individual species, with each species having their own unique environmental sensitivities and habitat preferences. These unique life history characteristics are not usually detected, or can be misdiagnosed by only using higher taxonomy, such as the Order level. By examining an individual site’s species list and combining this with knowledge of species habitat and water quality preferences, it is possible to make more informed decisions about an individual monitoring site’s ecological condition and the health of our rivers and streams.
