New advances in keeping tabs on river slime

New information has been released this week by Environment Southland to show the extent of slime algae or periphyton levels in Southland rivers: and the news is good.

We now monitor more frequently than before, and this has helped paint a very different picture of slime algae in the region. With monthly samples, we can now say more confidently that none of the 30 sites we test at 27 different rivers and streams fall below the national bottom line for periphyton.

A national bottom line is a level that has been set by the Government in the National Policy Statement for Freshwater Management. There are bottom lines set for a number of different water quality measures, and no rivers and streams are to fall below this standard.

Environment Southland's monthly monitoring of slime algae began in 2014, and prior to this monitoring was carried out only once a year during summer.

Director of science and information Graham Sevicke-Jones said that this more regular monitoring has created a much more accurate picture of slime algae levels in Southland rivers, and that the picture is much more positive.

The data we have been collecting monthly shows us that the state of slime algae is better than we thought it was when we only had the yearly information to rely on. The annual results had previously shown that 12% of sites tested fell below that national bottom line, Graham said.

Slime algae is just one of the things Environment Southland measures to get a picture of water quality and the health of river stream-life, alongside nitrogen, phosphorus, clarity, and macroinvertebrates (insects, worms and snails).

Graham said, This slime algae grows naturally in all water, and is an essential part of freshwater ecosystems, however problems occur when high temperatures and nutrients cause overgrowth. Very thick mats of slime algae change the stream environment, reduce the number of macroinvertebrates that provide food for fish, and remove life-giving oxygen from the water.

We are committed to finding new and better ways to improve our water quality monitoring all the time, and this new information is very helpful for us, and our community.

Read the full report here: https://www.es.govt.nz/periphyton-report