Impact on the marine environment is briefly mentioned in the last couple of paragraphs of the article, although they're a little dismissive and don't provide any evidence supporting their claim of negligible impact.
A bit more concerning is the notion of relocating these data centre pods. Long-term "reefs" that are relocated around the world could perhaps be a new and different vector for transmitting invasive organisms. I'm not an expert, but I'd want to hear a few of them opine as to whether this creates any risks that ordinary shipping does not.
The heated water from a power plant can actually provide a refuge for manatees and other wildlife that prefer warm water during cold winter. They're actually known as good fishing spots in Florida!
A server sub would put 200W * (say) 1000 servers, or 0.0002 GW.
That may change, but I doubt there are less server farms in 2020 than now.
As a side note, isn't that also Google's plan - the server farm as a single entity, where nothing is really fixed, just turned off and eventually replaced? In such a world, where a server farm exists then dies, underwater seems a great place for them. No regulations, no repairs, locally powered via means that no one can complain about (NIMBYism is a powerful force) just run until decommissioned.
What are the requirements for cargo ships? I suspect they run into this regularly when in a dock for extended periods or undergoing maintenance that doesn't require a dry-dock.
Nuclear plants also use cooling towers to lower the temperature before it dumped back into a lake/river/ocean. You can do a Google search, but those towers are hollow on the inside. Water runs down the inside walls and convection currents move up.
> The water just meters downstream of a Natick vessel would get a few thousandths of a degree warmer at most.
Sounds negligible to me, but I'm not a marine biologist. Would be interested to hear a specialist weigh in.
A single coal power plant is negligible to the environment too. Half the world powered by coal isn't.
Some of them apparently are at 500°F [1].
The issue is the amount of heat relative to the environment in which flora and fauna have evolved to survive, not relative to absolute zero.
It's like saying that a 313 Kelvin body temperature shouldn't bother me because I do fine with 310K (~37C). It's only a 3K difference, after all.
I'm not sure what that means (or if it's really true). The temperature at night doesn't drop to almost (absolute) zero; the oceans don't freeze; so plenty of the Sun's energy must still be present.
The second statement was that "OTOH, that 1GW drops to almost zero at night." It may be a literally true statement on its own, but it's misleading in response to a statement that absolute zero isn't a realistic basis for this discussion.