Effects of repeated exposure to 4‐nonylphenol on the zooplankton community in littoral enclosures

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 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.

Effects of 4‐nonylphenol on phytoplankton and periphyton in aquatic microcosms

“…Effects were apparent during the six‐week treatment period as well as the six‐week postapplication period, when NP concentrations were below detection limits. The recovery period found by O'Halloran [3] for zooplankton was one to four weeks. However, continuous exposure to NP, as simulated in this study, which occurs at sites receiving industrial and municipal effluents, might prevent recovery over a much longer time.…”

“…We found no effects of NP on species richness, diversity, and assemblage composition of periphyton. O'Halloran [3] suggested that periphyton growth might have been indirectly affected by a reduction in grazer numbers. We found that A. minutissimum , which is common in the presence of grazers, was dominating the assemblages in the controls and at higher NP concentrations during the treatment period but was less abundant at intermediate concentrations.…”

“…Concerns about the toxicity and endocrine potential of NP, a degradation product of the nonionic surfactants alkylphenol polyethoxylates, led to many studies on its occurrence in the environment and effects on aquatic animals and plants. However, most investigations were single species tests with only one study assessing effects on complex assemblages in littoral enclosures [1–4]. Effect concentrations for algae ranged from 2.5 to 2,500 μg/L, while NP concentrations up to 180 μg/L were found in freshwaters, but most were below 3 μg/L [5–10].…”

Evaluation of the Efficacy of Extrapolation Population Modeling to Predict the Dynamics of Americamysis Bahia Populations in the Laboratory

“…357-400), a series of papers describes the results from a comprehensive littoral enclosure study of NP in a freshwater system [31][32][33][34][35]. 357-400), a series of papers describes the results from a comprehensive littoral enclosure study of NP in a freshwater system [31][32][33][34][35].…”

Effects of nonylphenol on zooplankton in aquatic microcosms

“…Only one field study has so far investigated the effects of NP on complex zooplankton assemblages. A NP stock solution was added directly and repeatedly to the water of littoral enclosures, resulting in large variations of NP concentrations [17]. In our study, we added NP via controlled release to achieve a slow increase and more constant concentrations over a period of time.…”