1.   Both consume oxygen when they get into aquatic ecosystems.

2.   More generally, many experts say, over-fertilization from organic runoff has surpassed industrial pollutants as a threat to aquatic ecosystems.

3.   Of particular concern is the impact of nitrogen overload on aquatic ecosystems, especially coastal ones.

4.   Remove them, and the temperature rises and the aquatic ecosystem is transformed.

5.   Their waning is a sign of serious problems in the whole freshwater aquatic ecosystem of the region, scientists say.

6.   We affect the water cycle by discharging pollutants both directly into aquatic ecosystems and on the land, from where they leach into waterways.

7.   Still, the pesky creatures have irreversibly altered the aquatic ecosystem, concentrating toxins in algae and eliminating native clams.