> Isn't land-based biology highly sensitive to heat pollution?
No, land-based organisms comparatively have a much, much higher tolerance to temperature swings.
Water's high heat capacity and conductivity means that most marine environments have extremely stable temperature ranges (a few degrees one way or other), so most marine species are adapted to live in only that range, and quickly die otherwise. Tropical fish are hard to keep alive precisely for this reason.
Air temperature varies much more widely depending on time of day, season, and weather, so terrestrial organisms have all developed extensive strategies for thermoregulation (e.g. mammals, birds). For example, dogs can survive in both arctic and tropical environments.
Plus, while heat is naturally dissipated upward, underwater thermal plumes are more likely to affect fish than above-ground plumes would affect birds.
FYI, Cornell uses lake water to cool several campus buildings, and they needed to carefully review that the warmer return water wouldn't negatively affect fish [1].
Sunlight imparts about a kilowatt per square meter to the surface of the ocean at noon, I'm not exactly sure how to use that information, but it does seem relevant for bounding the problem.
This gets a lot lower with differing latitudes and seasonal and daily cloud cover/evening time - closer to 100 W/m2 [1]. So over a day you'd get 2.4 kWh. In comparison an electric space heater uses about 1 kWh of energy in an hour.
So how much will 2.4 kWh change the temperature of a cubic meter of water at the ocean surface?
Density of water = 1000kg/1m3 so mass = 1000 kg
2.4 kWh = 8640 kJ
Heat_Energy = Conductance * Mass * change_in_temp
8640kJ = 4.186 kJ/(kg⋅K) * 1000kg * xC
x = 2C
So solar heat will change the first meter of water by about 2C over the course of a day. That's a small number b/c solar radiation is not a huge contributer to temperature swings. Instead what will effect the temperature difference is the seasonal change. If we can calculate the heat energy gained or lost due to seasonal extremes and water temp, then we can figure out what the range of acceptable heat energy is for surface water.
I'm guessing you've never experienced the joys of owning a 30 to 40 ft sized, completely non metal (fiberglass hull) sailboat kept in salt water, with all of the great fun of paying to haul it and have the marine growth scaped off, pressure washed, double or triple coat bottom paint re-applied, etc. Just because it's not metal doesn't mean it doesn't attract the category of what the maritime industry lumps together as "marine fouling".
Though marine fouling is primarily of concern for fiberglass boats because it massively increases drag which admittedly is less of an issue for a datacenter. It's still an issue for the pods as mentioned in the article, but I'd expect it to be less grave than on a boat.
GP was quite specifically taking about chemical corrosion, not bio-fouling. Even if the marine industry conflates these (I can't tell if that's what you're implying in the last sentence), we don't have to.
Plastics are good, but you need to have tubes going into the thing, as well as some means of accessing the inside even if you only access it on a ship/land. That means rubber and metal will have to be on the exterior somewhere.
To metals. Not so much to plastics.
> Isn't marine biology highly sensitive to heat pollution?
Isn't land-based biology highly sensitive to heat pollution?