I came across this article on the BBC recently and it struck me as an excellent idea and one in which sailors could make a contribution with very little effort. It's a simple device to measure plankton for Plymouth University and this is part of what they say:
The marine phytoplankton account for approximately 50% of all
photosynthesis on Earth and, through the plankton food web that they
support, they both underpin the marine food chain and play a central
role in the global carbon cycle strongly influencing the Earth’s
Living at the surface of the sea the phytoplankton are particularly
sensitive to changes in sea surface temperature. A recent study of
global phytoplankton abundance over the last century concluded that
global phytoplankton concentrations have declined due to rising sea
surface temperatures as a consequence of current climate change....
You can read the BBC article
and the stuff from Plymouth Uni
this second link has an additional link to downloading a mobile app to report the data you find. Apart from a phone they ask you to make a white 30cm disc, called a Secchi, take a reading between 10 and 2pm and a few other small points - well you can read about it in detail on the second site. Seems a great idea to harness those already out there on the oceans to provide valuable data. Most yotties I know seem to have mobile phones so no reason not to get involved....