“Vast quantities of water are being pumped into the ocean as a result of human activities. A summation of the estimates for the various sectors in this review estimates that this has now surpassed 1,000 Gt/ year. Many of these discharges are contaminated or altered such that they vary significantly from the natural environment. This has led to a process of geoengineering on a global scale, too often intentionally with negative consequences. In many cases discharges are managed to limit local scale impacts, yet it remains acceptable to discharge toxic contaminants, such as chlorine and heavy metals, provided they are diluted to ‘acceptable levels’. Accumulation of nutrients is causing eutrophication leading to hypoxic dead zones and algal overgrowth of coral reefs.”
A review of anthropogenic marine water discharges July 2021 (pdf)