|MadSci Network: Botany|
Mikkel, Algae certainly have C3 photosynthesis. The confusion over C4 metabolism arises because the enzymes present in C4 photosynthesis are present in algae as well. These enzymes, PEP carboxylase and PEP carboxykinase, supplement C3 metabolism in the algae. These enzymes are present in different algal groups in different amounts and are not sensitive to oxygen like the Calvin cycle enzyme Ribulose bisphosphate carboxylase. Unlike terrestrial plants, though, they do not have the specialized Kranz anatomy. So algae are capable of more than C3 metabolism alone, but is not as complex as C4 or Crassulacean acid metabolism.
Try the links in the MadSci Library for more information on Botany.