An integrated evaluation of the persistence and effects of 4-nonylphenol in an experimental littoral ecosystem

Abstract

Abstract A comprehensive littoral enclosure study was conducted to assess the persistence and distribution of 4-nonylphenol (NP) in a littoral ecosystem, and to evaluate the compound's effects on resident aquatic biota. Enclosures with a mean (±SD) surface area and volume of 31.4 ± 3.3 m2 and 32.0 ± 6.4 m3, respectively, received eleven applications at 48-h intervals with one of four different rates of NP. This created a 20-d application period which was followed by a three to fourteen month observation period, depending on the endpoint measured. Mean ± SD NP concentrations in the water column measured 2 h after each application averaged 5 ± 4, 23 ± 11, 76 ± 21, and 243 ± 41 μg/L at nominal treatments of 3, 30, 100, and 300 μg/L, respectively. Persistence in the water column was relatively short, with a dissipation half-life estimated at ≤1.2 d. Persistence of NP in sediment and on macrophytes was substantially longer, with estimated half-lives of 28 to 104 d and 8 to 13 d, respectively. Zooplankton was the most sensitive group of organisms evaluated, with significant reductions in population abundances of some copepod taxa observed at the 23 ± 11-μg/L treatment. Fish survival was affected at 243 ± 41 μg/L. The most sensitive benthic macroinvertebrate taxon, Pisidium (Bivalvia) was affected at 76 ± 21 μg/L, but most taxa were only affected at the 243 ± 41-μg/L treatment. None of the assessed populations were affected at the 5 ± 4-μg/L treatment. Macrophytes and periphyton were not adversely affected by any of the treatments. Overall community composition, assessed at the family level or higher, was not affected at or below the 23 ± 11-μg/L treatment, but did exhibit substantial changes at the 243 ± 41-μg/L treatment. Some minor changes were observed at the 76 ± 21-μg/L treatment. The maximum acceptable toxicant concentration in the water column, based on protection of the most sensitive taxa in the test system, was estimated at ˜10 μg/L. Details on NP persistence and distribution within the enclosures, and detailed effects on zooplankton, benthic macroinvertebrates, and fish are described in four separate papers immediately following this overview.