Hydrolysis rates of six structurally distinct polysaccharides in surface ocean waters of the Atlantic, Pacific, Arctic, and Southern Oceans (pull = pullulan, lam = laminarin, xyl = xylan, fu = fucoidan, ara = arabinogalactan, and chon = chondroitin sulfate). Negative numbers = degrees S latitude. The range of substrates hydrolyzed by heterotrophic microbial communities, as well as summed rates of hydrolysis, varies systematically with latitude. Only for laminarin is this variation well-correlated with in situ temperature. Microbial community function varies in a systematic manner, perhaps reflecting large-scale changes in microbial community composition along latitudinal gradients and decreased community diversity towards the poles [11, 12] (figure reprinted from [13]).