Abstract-The importance of salinity in whole effluent toxicity tests using marine organisms has been acknowledged in most testing protocols. However, little if any attention has been given to the specific effects of alteration of the ionic composition of seawater solutions to the test organism. The presence of persistent toxicity in effluents with no apparent toxic agents prompted examination of the potential influence of essential ions on the survival of the opossum shrimp, Mysidopsis bahia, a common effluent toxicity indicator organism. Through stepwise additions of ionic salts to deionized water, the minimum complement of salts to maintain survival of M. bahia during 96-h exposures was determined to be Ca, Mg, K, Br, Na, and Cl. The toxicity curves for Ca, Mg, K, and Br were then determined across test salinity ranging from 10 to 35 parts per thousand. These curves for Ca, Mg, and K revealed that there are significant negative effects on survival when the essential ions are present in either low or high concentrations relative to the levels in natural seawater. Although there were no statistically detectable effects of Br on organism survival over the concentration range tested (5-480 mg/L), Br toxicity at concentrations less than 5 mg/L and greater than 700 mg/L have been shown in other studies. In addition, the tolerance ranges for K, Ca, and Mg were shown to shift significantly with changes in salinity, with lower salinity causing an apparent decrease in tolerance to an excess of essential ions. Tests with toxic effluents from five industrial and municipal sources revealed that adjustment of the ionic balance prior to testing reduced or eliminated toxicity in four of the five whole effluents tested. Suggestions for integrating this information into biomonitoring programs and toxicity identification evaluations are presented.

Fuel profiles following fire & post-fire logging Donato et al. Abstract 28Following severe wildfires, managing fire hazard by removing dead trees (post-fire 29 logging) is an important issue globally. Data informing these management actions are relatively 30 scarce, particularly how fuel loads differ by post-fire logging intensity within different 31 environmental settings. In mixed-evergreen forests of Oregon, USA, we quantified fuel profiles 32 3-4 years after stand-replacement fire-assessing three post-fire logging intensities (0%, 25-33 75%, or >75% basal-area cut) across two climatic settings (mesic coastal, drier interior). Stand-34 replacement fire consumed ~17% of aboveground biomass. Post-fire logging significantly 35 reduced standing dead biomass, with high-intensity treatment leaving a greater proportion (28%) 36 of felled biomass on site compared to moderate-intensity treatment (14%) because of less 37 selective tree felling. A significant relationship between logging intensity and resulting surface 38 fuels (0.4-1.2 Mg*ha -1 increase per m 2 *ha -1 basal-area cut) indicated a broadly applicable 39 predictive tool for management. Down wood cover increased by 3-5 times and became more 40 spatially homogeneous after logging. Post-fire logging altered the fuel profile of early-seral 41 stands (standing material removed/transferred, short-term increase in surface fuels, likely 42 reduction in future large fuel accumulation), with moderate-intensity and unlogged treatments 43 yielding surface fuel loads consistent with commonly prescribed levels, and high-intensity 44 treatment resulting in greater potential need for follow-up fuel treatments. 45 46

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A toxicity identification evaluation (TIE) was conducted on the effluent from a petrochemical plant which discharges into an estuary. The effluent had been consistently toxic to mysid shrimp (Mysidopsis bahia) but not toxic to sheepshead minnows (Cyprinodon variegatus). Phase I effluent toxicity characterization tests revealed that treatment of the effluent with a cation exchange resin (Amberlite(R) IR-120 Plus) was partially effective at reducing, but not removing, toxicity. Phase II characterization tests revealed that four cations varied with toxicity: Ca and Sn were positively correlated with increasing toxicity; Mg and K were negatively correlated with increasing toxicity. Toxicity tests with SnCl2 revealed that the toxicity threshold for Sn was far above the concentrations present in the raw effluent. Reduction of Ca was shown to result in a significant improvement in survival, but some toxicity still remained. Further augmentation of the treated effluent with CaCl2, MgCl2, and KBr to restore the concentrations of Ca, Mg, K, and Br to natural seawater concentrations resulted in survival of all exposed organisms. Repeated success of this treatment regime on additional samples of the effluent as well as "mock effluent" studies confirmed that ion imbalance was the sole source of toxicity in this effluent. Process source water composition and essential ion balance are discussed as important components of marine effluent TIEs.

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