 Macroinvertebrate families are good indicators of organic loading and both the BMWP scores and the more recent WHPT biotic index scores are very low, compared with a clean chalk stream like the River Mimram which has a biotic index of around 210.The best scoring area of the brook (close to the headwaters) has never gone above 32.Channel sediments are also heavily contaminated particularly with heavy metals, lead, zinc, copper, and cadmium are all extremely high.