That's the summary you chose. Here's what else is said:
"It must be noted that a large proportion of the published work is descriptive and provides little quantitative data that we could assess independently. Many of the monitoring studies lacked sufficient detail with respect to study design and statistical analyses, making conclusive interpretation of results difficult."
"It is clear that greater clarity and improved methodologies are required in the assessment of the ecological impacts of desalination"
Summary: Can be bad, but effects localised to tens of metres when done properly (i.e good flushing).