Toxicity and bioaccumulation in bluegill sunfish (Lepomis macrochirus) of 4-nonylphenol (NP), a common precursor and degradation intermediate of certain nonionic surfactants, were evaluated in a set of 18 aquatic mesocosms (littoral enclosures) in northeastern Minnesota. Nonylphenol was applied to enclosures every 48 h over a 20-d period (11 applications) at rates of 3, 30, 100, and 300 g/L. Additional enclosures served as untreated controls. Maximum NP levels in the integrated water column 2 h after each application averaged 5 Ϯ 4, 23 Ϯ 11, 76 Ϯ 21, and 243 Ϯ 41 g/L over the 11 applications at the 3-, 30-, 100-, and 300-g/L treatments, respectively. Sixty-one percent of the NP dissipated from the water column within ϳ39 h of each application. Estimated survival of stocked juvenile bluegills was significantly reduced at the 300-g/L NP treatment. No significant effects were noted at the other NP treatments; however, the 100-g/L enclosure with the highest mean NP concentration (93 Ϯ 39 g/L) within that treatment had four to nine times more dead bluegills and four to six times fewer bluegills captured at the end of the season than the other two 100-g/L enclosures (64 Ϯ 23 and 71 Ϯ 32 g/L) and the controls, suggesting increased mortality in this enclosure. Nonylphenol tissue concentrations in juvenile bluegills collected from enclosures treated with 3 and 30 g/L NP ranged from 0.01 to 2.94 g/g wet weight and showed a significant positive relationship with the average measured NP concentration in the water. The mean wet weight nonequilibrium NP bioaccumulation factor was 87 Ϯ 124. There was no relationship between fish lipid content and NP tissue concentration.

The effect of 4-nonylphenol (NP) on benthic, freshwater macroinvertebrates in littoral enclosures was evaluated over a 2-year period. Enclosures received 11 NP applications, 48 h apart, with nominal rates of 3, 30, 100, and 300 g/L. Mean measured peak concentrations in integrated water column samples over the 20-d application period were 5 Ϯ 4, 23 Ϯ 11, 76 Ϯ 21, and 243 Ϯ 41 g/L NP. Concentrations of NP in the water column decreased rapidly after the last application. Maximum NP concentrations measured in sediments, pore water, and macrophytes of a 300-g/L enclosure were 27.4 mg/kg, 29.9 g/L, and 89.6 mg/kg, respectively. The most abundant macroinvertebrate groups, Chironomidae, Oligochaeta, and Mollusca, decreased in abundance after application. Effects on Mollusca were the most severe. Their numbers were significantly reduced at the highest treatment (243 Ϯ 41 g/L NP) throughout most of the study. Oligochaetes (Naididae, Tubificidae) and chironomids (Tanytarsini, Chironomini) were also significantly reduced at the highest treatment, but populations recovered within 6 weeks. Snails and naidid oligochaetes were slightly affected at the second highest treatment (76 Ϯ 21 g/L NP). Insect emergence was reduced during and immediately postapplication, but the effects were likely caused or compounded by a surfactant sheen on the surface of the water that interfered with emergence and/or oviposition. The observed effects on the benthic community were most likely due to exposure from the water, although more persistent macrophyte-associated residues may have contributed to effects on Gastropoda, Naididae, and Tanytarsini. Macrophyte-associated NP residues may pose a small risk to benthic organisms, but it is probably minor compared to water exposures. The no-observed and lowest-observed-effect concentration for the benthic community was 23 Ϯ 11 and 76 Ϯ 21 g/ L NP, respectively.

Abstract-Toxicity and bioaccumulation in bluegill sunfish (Lepomis macrochirus) of 4-nonylphenol (NP), a common precursor and degradation intermediate of certain nonionic surfactants, were evaluated in a set of 18 aquatic mesocosms (littoral enclosures) in northeastern Minnesota. Nonylphenol was applied to enclosures every 48 h over a 20-d period (11 applications) at rates of 3, 30, 100, and 300 g/L. Additional enclosures served as untreated controls. Maximum NP levels in the integrated water column 2 h after each application averaged 5 Ϯ 4, 23 Ϯ 11, 76 Ϯ 21, and 243 Ϯ 41 g/L over the 11 applications at the 3-, 30-, 100-, and 300-g/L treatments, respectively. Sixty-one percent of the NP dissipated from the water column within ϳ39 h of each application. Estimated survival of stocked juvenile bluegills was significantly reduced at the 300-g/L NP treatment. No significant effects were noted at the other NP treatments; however, the 100-g/L enclosure with the highest mean NP concentration (93 Ϯ 39 g/L) within that treatment had four to nine times more dead bluegills and four to six times fewer bluegills captured at the end of the season than the other two 100-g/L enclosures (64 Ϯ 23 and 71 Ϯ 32 g/L) and the controls, suggesting increased mortality in this enclosure. Nonylphenol tissue concentrations in juvenile bluegills collected from enclosures treated with 3 and 30 g/L NP ranged from 0.01 to 2.94 g/g wet weight and showed a significant positive relationship with the average measured NP concentration in the water. The mean wet weight nonequilibrium NP bioaccumulation factor was 87 Ϯ 124. There was no relationship between fish lipid content and NP tissue concentration.

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