The McMurdo Dry Valleys of Antarctica are the largest ice-free region on the continent, and despite the name, they contain streams that flow for 8-12 weeks during the austral summer (November - February each year). These streams do not flow during the dark Antarctic winter. However, even during their summer flow seasons, they can cease flowing for a few hours or days depending on the weather as cold, cloudy conditions reduce the melt of glacier ice that feeds the streams; a snow storm can also reduce melt of glacier ice. Here we present three ways in which these intermittent stream ecosystems function. Firstly, their beds are covered with mats of algae that host microscopic diatoms and the mix of these diatoms is determined in part by how intermittent a stream is. Secondly, during low flow conditions, salt and nutrient concentrations tend to be relatively high in the streams, indicating that the streambeds are contributing solute-rich water to the channels. Finally, we describe how the stream ecosystem shifts from being net productive of oxygen to more consumptive during low and no-flow conditions, further evidence of the influence of the streambeds.