- The Marine Science Laboratory at the Pacific Northwest National Laboratory evaluated the impact of biofouling on the performance or uranium adsorbents. A surface-modified polyethylene adsorbent fiber provided by Oak Ridge National Laboratory, AF adsorbent, was tested in either the presence or absence of light to simulate deployment in shallow or deep marine environments. Samples of the adsorbent fiber were exposed to seawater as loose fibers packed with glass beads in columns and as >10-cm-long braids of fiber placed in a flume that provided a continuous flow representative of natural ocean currents. Exposure tests (42 days) in column and flume settings showed that biofouling resulted in decreased uranium uptake by the adsorbent fiber. Uranium uptake was reduced by up to 30%, in the presence of simulated sunlight, which also increased biomass accumulation and altered the microbial community composition on the fibers. These results suggest that deployment below the photic zone would mitigate the effects of biofouling, resulting in greater yields of uranium extracted from seawater.