The most direct effect of desalination on the environment among the options you provided is:
Brine can kill ocean wildlife.
Desalination processes produce a concentrated brine byproduct that is often discharged back into the ocean. This brine can have harmful effects on marine ecosystems, as it increases salinity and can negatively impact marine life. The other options, while they may relate to water management issues, are not direct effects of desalination itself.