[Richard777 (OP)]

I have read that a significant amount of microscopic particles of plastic contaminate our oceans.
How does this affect the heat content of the oceans?
I would assume that it will help the oceans to retain heat.
How does this affect marine life? Probably not too good.
It seems that nobody cares about the oceans, they seem to serve as the worlds communal dump.

[evan_au]

I would assume that (microplastics in the oceans) will help the oceans to retain heat

Water has a very high heat capacity, due to its hydrogen bonding. So it is already very good at retaining heat.
- In fact, a majority of human-induced global warming is absorbed by the oceans, reducing atmospheric warming
See: https://en.wikipedia.org/wiki/Table_of_specific_heat_capacities

Microplastics don't form an insulating layer on the oceans. If it did, it would merely reduce the amount of atmospheric warming that is soaking into the oceans.

I think the main threat of plastics in the ocean is that big pieces kill marine life (eg by suffocation), smaller pieces gets stuck in their guts, and tiny pieces leach chemicals that can do nasty things (like build up toxins in the body and affect hormone levels). And the same chemicals can affect humans, who eat marine life.

[alancalverd]

The specific heat capacity of most plastics is less than half that of water, so adding plastic residue actually reduces the mean heat capacity of the oceans.