Nanoparticles are entering natural systems through product usage, industrial waste and post-consumer material degradation. As the production of nanoparticles is expected to increase in the next decade, so too are predicted environmental loads. Engineered metal-oxide nanomaterials, such as titanium dioxide, are known for their photocatalytic capabilities. When these nanoparticles are exposed to ultraviolet radiation in the environment, however, they can produce radicals that are harmful to aquatic organisms. There have been a number of studies that have reported the toxicity of titanium dioxide nanoparticles in the absence of light. An increasing number of studies are assessing the interactive effects of nanoparticles and ultraviolet light. However, most of these studies neglect environmentally-relevant experimental conditions. For example, researchers are using nanoparticle concentrations and light intensities that are too high for natural systems, and are ignoring water constituents that can alter the light field. The purpose of this review is to summarize the current knowledge of the photocatalytic effects of TiO nanoparticles on aquatic organisms, discuss the limitations of these studies, and outline environmentally-relevant factors that need to be considered in future experiments.

The Columbia River has a dynamic and fast flushing estuary impacted by strong advection and mixing of riverine and oceanic waters, and high but variable loads of suspended particulate matter. Transient, but recurring water and nutrient fluxes from end-members impart strong spatial and temporal gradients, contributing to microbiological hotspots that play important ecological roles in the estuary. Investigations of corresponding microbiota require precisely timed samples that are contextualized by physical and biogeochemical data. To accomplish this, we embedded a robotic microbial sampler (Environmental Sample Processor, ESP) within the operations of an interdisciplinary observation and prediction system (Science and Technology University Research Network, SATURN; www.stccmop.org/saturn). Autonomous, adaptively sampled water collection by the ESP was implemented based on environmental conditions assessed from SATURN physical and biogeochemical sensors. Water was pumped from multiple depths to sensors and the ESP on dry land. If water met user-defined parameters, ESP sampling was automatically initiated. This strategy was tested during three deployments in summer 2013, during which operational tools for analysis and visualization were used to formulate well-constrained mission plans by providing estimates of the intensity and timing of oxygendepleted ocean water intrusion and estuarine turbidity maxima. This allowed the effective characterization of the impact of these events on selected estuarine microbiota.Microorganisms are key components of aquatic ecosystems that play determinant roles in global nutrient and energy cycles (Karl 2007). However, resolving microbial responses to environmental variability requires a sampling resolution that is often difficult to achieve through conventional approaches (Paul et al. 2007). This is especially true for dynamic estuaries such as the Columbia River. This riverdominated mesotidal estuary is subjected to large and varying influence from freshwater and oceanic end-members, strong currents, short water residence times, and high and variable suspended particulate matter concentrations.Recurring but transient events play important roles in the estuary. Among these, Estuarine Turbidity Maxima (ETM) are biologically active (Crump and Baross 1996;Crump et al. 1999;Br€ auer et al. 2013;Smith et al. 2013), short-lived sedimentary features generated during tidal reversals as salinity intrusion interacts with residual bottom currents (Jay and Musiak 1996). Their intensity varies according to season and tidal cycle, with larger ETM typically observed during spring tides (Small and Morgan 1994;Small and Prahl 2004). Other significant events occur transiently in the summer, such as intermittent intrusion into the estuary of ocean waters low in dissolved oxygen (DO, at times to the point of hypoxia, Roegner et al. 2011) during upwelling periods, and the recurring late summer bloom of phototrophic ciliate Mesodinium sp. (formally referred to as Myrionecta rubra) (Herfort et al....

We examined the possibility that decreased environmental oxygen can elevate the levels of indigenous bacteria in the hemolymph of Cancer magister. Crabs were exposed to air-saturated and hypoxic (50% air-saturation) water for 3 days and levels of culturable bacteria in hemolymph were measured every 24 h as the total number of colony-forming units (CFU) per milliliter of hemolymph. Bacteremia increased after 24 h of exposure to hypoxia and persisted for 72 h, whereas crabs exposed to normoxia had no measurable change in number of culturable bacteria. The predominant persistent bacteria in the hemolymph was isolated and identified by DNA sequence-based methods as Psychrobacter cibarus. Crabs were injected with P. cibarus or with buffered saline as a control after 3 h of hypoxia. Levels of culturable bacteria were significantly higher in hypoxic crabs than in normoxic ones (about 2500 versus 1000 CFU ml(-1) 80 min post-injection, respectively), and circulating levels of oxygen were significantly reduced in infected animals compared to uninfected ones after 48 h in hypoxia and after 72 h in air-saturated water post-injection. These data demonstrate that P. cibarius is present in Dungeness crabs, that environmental hypoxia can dramatically elevate levels of persistent bacteria, and that hypoxia in the presence of hemolymph bacteria may ultimately reduce immune and respiratory ability.

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