Constructed stormwater wetlands are used to manage polluted stormwater before it enters waterways. To ascertain the effectiveness of these wetlands, the quality of water and sediments (i.e. pollutant load) in the inlet and outlet are often compared. If a reduction in pollutant load is observed, the wetland is deemed effective. This method, however, provides no information on how the biological communities in the wetland are impacted by pollution, creating a need for bioindicators. Bioindicators are useful in monitoring as they can provide an indication of the ecological health of a waterway.
Our study explored the bioindicator potential of biofilms and zooplankton in constructed stormwater wetlands. We conducted a crossed design microcosm study whereby biofilms and zooplankton were collected from sites with differing levels of nutrient and pesticide pollution and placed in water from their wetland of origin, as well as into that of the wetland with different water quality. Using this method, we were able to detect changes in community structure and abundance when biofilms and zooplankton were moved from higher to poorer quality water. Biofilms originating from higher quality water, became more heterotrophic and bacteria dominated when placed in poorer quality water, while zooplankton decreased in total abundance when placed into poorer quality water. In contrast, biofilms originating from poorer quality water remained relatively stable when placed in higher quality water, and zooplankton showed an increase in total abundance.
These results suggest that biofilms and zooplankton are sensitive to changes in pollution, and we recommend that future studies continue to explore the bioindicator potential of biofilms and zooplankton in constructed stormwater wetlands and other waterways.