VARIED SYSTEMS. “Seagrasses have long been regarded as C3 plants, but physiological measurements have gathered indications that several seagrass species, including Z. marina, are C3-C4 intermediates or have various carbon-concentrating mechanisms to aid the RuBisCO enzyme in carbon acquisition.”
http://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-11-8