Is freshwater macroinvertebrate biodiversity being harmed by synthetic chemicals in municipal wastewater?

Historically, indices of macroinvertebrate diversity have played a vital role in demonstrating the harmful impacts of poor quality wastewater effluent. The reduction of macroinvertebrate diversity in the past was associated with high organics, low oxygen and high ammonia. There is a current hypothesis that the profusion of micro-organic contaminants escaping in wastewater from modern society are harming macroinvertebrates. Whilst evidence exists for some reduced biodiversity downstream of wastewater treatment plants, it is unclear if such contaminants are responsible. However, evidence from reviewing long-term monitoring records shows consistent and welcome improvements in diversity since the 1990s in the UK. It is perplexing that more use is not made of such long-term macroinvertebrate records to address questions of chemical impacts.