Good question, but hard to say. The tricky bit is how to quentify “more affected”?
The Ocean and the land are very difficult to compare, already because humans live and shape the terrestrial land while no humans live in the Ocean. The Ocean and the land are completely differently affected by changes in the atmosphere, with all unknown variables, I’d say tricky to say. But the question is great for a long discussion!
Philip has summed this up nicely below. But yes I do think this is very difficult to answer. For me, we don’t even know what is in the ocean, so when climate breakdown begins to impact the ocean.. we won’t even know exactly what diversity we are losing. The same can be said for the rainforests and hard to access parts of the land based ecosystems.