Question

A desalination plant is set up in a bay to provide fresh, drinkable water by removing salt from ocean water and returning the removed salt to the bay. How might the resulting increase in salinity in the bay affect the fish populations?

Answer 1

None effect on the fish population at all, one desalination plant plant won't cause any changes in a ecosystem, that rain won't compensate for. Considering a Ocean is is a big heap of water, the changes in Water & Salt ratio would be below millipromille range.

Answer 2

Actually the effect is quite on the contrary exuras, where the highly salinised water is being pumped out there will be localised high salinity. The relative weight of the saline water will cause it to sink to the sea floor potentially effecting any sea life there. For example sea grass may live in such an area which would support invertebrates which the fish in turn would feed upon hence effecting fish populations. The placement of the discharge pipes in relation to sensitive ecosystems and the flow and mixing of the seawater (and a few other factors) will determine if there is a big effect on the surrounding ecosystem. See this paper for more information: http://www.idswater.com/Common/Paper/Paper_153/Einav_footprint.pdf (or if this link doesn't work: http://www.sciencedirect.com/science/article/pii/S0011916402010573 )

Answer 3

I stand corrected @TranceNova, thank you for providing the corresponding links to publications concerning this.