Tweleve ponds on the McMurdo Ice Shelf were sampled to create and annual data set of water nutrient chemistry (DRP, NH4-N, NO3-N, TDN, TDP), pH, conductivity, temperature, phytoplankton chlorophyll a, and particulate N: P. Biological parameters collected include benthic algal chlorophyll a and ash-free dry weight, benthic microbial biomass, pigment and species composition. Species composition and ... dominance within the microbial mats varies from pond to pond. Photosynthetic and nitrogen fixation rates of benthic algae were determined from several ponds with contrasting physio-chemical properties. Samples were collected from ponds for algal species determination and microbial mat samples were collected and preserved for community spatial structure (i.e. position of each species within the microbial matrix). The annual 12-pond dataset has been operating since January 1988 and is one of the longest-running environmental datasets in Antarctica.