Stormwater and wastewater discharge is slowing the larval dispersal of the common bat star — a marine organisms found in the coastal waters of Southern California - reports a study in Nature Communications this week. Billions of litres of effluent are discharged daily along high population coastlines like Southern California but the full ecological effects of these discharges is not fully understood.

Jonathan Puritz and Robert Toonen studied the impact of contaminants and toxins on 16 populations of the common bat star along the coastline of the Southern California Bight. This marine organism is not fished or harvested and therefore free from direct human impact. The results show a decrease in the population connectivity and the genetic diversity of the bat star which is linked to the discharge of storm- and waste water in to the coastal waters.