Abstract-The effects of 4-nonylphenol (NP) on freshwater zooplankton were evaluated in 18 littoral enclosure mesocosms in northeastern Minnesota. The 18 enclosures were allocated to three blocks of six units with each block including two untreated control enclosures and one enclosure for each of four NP treatments (3, 30, 100, and 300 g/L). Treated enclosures received 11 applications of NP over a 20-d period between July 8 and 28, 1993. Maximum NP concentrations measured in the water column 2 h after each application averaged (ϮSD) 5 Ϯ 4, 23 Ϯ 11, 76 Ϯ 21, and 243 Ϯ 41 g/L over the 11 applications. Nonylphenol dissipated rapidly from the water column but was more persistent in sediments and in/on macrophytes. All cladoceran and copepod taxa were significantly reduced in abundance at 243 Ϯ 41 g/L; some sensitive taxa were also affected at 76 Ϯ 21 and 23 Ϯ 11 g/L. While many rotifer taxa were unaffected at any of the test concentrations, several were affected at Ն76 Ϯ 21 g/L. Ostracods were only affected at 243 Ϯ 41 g/L. No zooplankton taxon was affected at 5 Ϯ 4 g/L. The period of maximum impact usually occurred within 1 to 7 d of the last NP application, and recovery to control abundance levels generally occurred within 7 to 28 d of the last NP application. Two sensitive taxa, Acroperus and Calanoida, did not recover at Ն76 Ϯ 21 g/L by the end of the study. The maximum acceptable toxicant concentration for protection of all zooplankton taxa was estimated at ϳ10 g/L, although overall community diversity was unaffected at 23 Ϯ 11. The water was the most probable route of NP exposure, but the greater persistence of NP residues in/on macropyhtes may have contributed to the lack of recovery of some macrophyte-associated taxa.

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.

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.

The effects of 4‐nonylphenol (NP) on freshwater zooplankton were evaluated in 18 littoral enclosure mesocosms in northeastern Minnesota. The 18 enclosures were allocated to three blocks of six units with each block including two untreated control enclosures and one enclosure for each of four NP treatments (3, 30, 100, and 300 μg/L). Treated enclosures received 11 applications of NP over a 20‐d period between July 8 and 28, 1993. Maximum NP concentrations measured in the water column 2 h after each application averaged (±SD) 5 ± 4, 23 ± 11, 76 ± 21, and 243 ± 41 μg/L over the 11 applications. Nonylphenol dissipated rapidly from the water column but was more persistent in sediments and in/on macrophytes. All cladoceran and copepod taxa were significantly reduced in abundance at 243 ± 41 μg/L; some sensitive taxa were also affected at 76 ± 21 and 23 ± 11 μg/L. While many rotifer taxa were unaffected at any of the test concentrations, several were affected at ≥76 ± 21 μg/L. Ostracods were only affected at 243 ± 41 μg/L. No zooplankton taxon was affected at 5 ± 4 μg/L. The period of maximum impact usually occurred within 1 to 7 d of the last NP application, and recovery to control abundance levels generally occurred within 7 to 28 d of the last NP application. Two sensitive taxa, Acroperus and Calanoida, did not recover at ≥76 ± 21 μg/L by the end of the study. The maximum acceptable toxicant concentration for protection of all zooplankton taxa was estimated at ˜10 μg/L, although overall community diversity was unaffected at 23 ± 11. The water was the most probable route of NP exposure, but the greater persistence of NP residues in/on macropyhtes may have contributed to the lack of recovery of some macrophyte‐associated taxa.

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