An electron microscope is very powerful and allows you to see very tiny, thin specimens. The question makes it seem that you looked through both types of microscopes at specific samples? As for how they would differ, a light microscope's level of magnification is limited by the physical characteristics of light and therefore can only see objects as small as organelles inside of a cell. A scanning electron microscope, however, does not use light, it uses a beam of electrons to visualize the sample. Electrons are much smaller than the light beam and are able to image much smaller objects, such as molecules and atoms.
Warmer oceans would mean less dissolved CO2 as well as other gases such as oxygen in the global ocean. Lower CO2 would result in a decrease in photosynthesis of autotrophs living in the oceans.
