Plantae monophyletic group green algae dominant photosynthesizers in freshwater. Land plants: dominant photosynthesizers in terrestrial systems use both chlorophyll a and b. Chlorophyll b- in green algae and land plants. 8000 species, 90% freshwater, main primary producers in freshwater (critical to food webs), unicellular and multicellular species. Green algae 90% in freshwater environments, some are harsher (snow/cold) watermelon algae, form of green algae that grows at high elevation in snow. Under ice- diatom community that drives food chains of arctic ecosystems. Diatoms- in same group as brown algae, would not have chlorophyll b. As climate changes, 400ppm-700-1000 in next century, phytoplankton are important in global carbon cycles ( of world"s photosynthetic carbon fixation) Co2 at bottoms of oceans or lakes- long term carbon sink (carbon sinks) Dr. bell long term experiments to test carbon uptake by phytoplankton - hypothesis, phytoplankton have higher c activity in higher elevations expect both lines had higher co2 uptake at higher co2.