Littoral Enclosure Research Articles

Pollution biomarkers in two estuarine invertebrates, Nereis diversicolor and Scrobicularia plana, from a Marsh ecosystem in SW Spain

The polychaete worm Nereis diversicolor and the clam Scrobicularia plana were collected from several sites, affected by different types of contamination, in a littoral enclosure in the SW Spain (Caño Sancti-Petri and Rio San Pedro). N. diversicolor was present in 6 sampling sites whereas S. plana in 4 of them. The aim of our study was to relate several pollution biomarkers to chemical sources (metals and organic pollutants e.g. PCB, PAH) in these species, thereby confirming their adequacy as sentinels for this habitat. The biomarkers surveyed in the two invertebrates were the activities of the antioxidant enzyme catalase (CAT), the phase II detoxifying enzyme glutathione S-transferase (GST) and the neurotoxicity marker acetylcholinesterase (AChE). Metallothionein (MT) levels were measured as a biomarker of exposure to metals. The results suggested a different response in the two sediment-dwelling organisms, the sediment-eating polychaete and the water-filtering clam, probably as a consequence of different contamination exposures. The results also suggested that samples from the “Caño Sancti-Petri” were exposed to biologically active compounds that altered some of their biochemical responses. Of all the biomarkers tested, AChE was the most sensitive one and N. diversicolor the potentially most robust sentinel in this ecosystem. In this low to moderately polluted environment, the biochemical approach better reflected temporal trends than site-related differences although it was also able to detect punctual chemical insults.

Persistence and Distribution of Azinphos-methyl Following Application to Littoral Enclosure Mesocosms

The organophosphorus insecticide azinphos-methyl was applied once to the surface of 12 of 18 littoral enclosure mesocosms (5×10 m) constructed in a 2-ha pond near Duluth, Minnesota. Water, sediment, macrophytes, and adult fathead minnows were analyzed for residue to determine the persistence, distribution, and mass balance of azinphos-methyl. Nominal treatment concentrations were 0, 0.2, 1, 4, and 20 μg/liter active ingredient. The maximum residue concentration in the water was measured 1h after treatment. The half-life in the water column ranged from 1.2 to 2 days and 95% of the residue dissipated in 5.4 to 10.2 days. Measurable residues were found in the sediment, macrophytes, and fish. Maximum residues in these media were measured at 4, 1, and 0.12 days. respectively. The water and sediment were the most important sorptive compartments for azinphos-methyl residue. The macrophytes and fish were of minor importance, containing only trace amounts of the mass applied.

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

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.

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

AbstractA 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.

Evaluation of model predictions of the persistence and ecological effects of diflubenzuron in a littoral ecosystem

The accuracy of the Littoral Ecosystem Risk Assessment Model ( leram) was evaluated using results from a littoral enclosure study of the distribution, persistence, and ecological effects of the insecticide diflubenzuron. leram simulates the community and ecosystem level effects of a chemical stressor by linking single-species toxicity data to a bioenergetic model of a littoral ecosystem. This study evaluated (1) the accuracy of a simple fate and persistence model used in conjunction with leram, (2) leram's ability to predict, a priori, the effects of diflubenzuron on aquatic life, and (3) leram's usefulness for selecting treatment concentrations for an actual littoral enclosure study. The ecological effects of nine initial diflubenzuron concentrations ranging from 0.2 to 35.0 μg/l were simulated. The field study used to evaluate these predictions was performed in 12 littoral enclosures constructed in a 2-ha pond in northeastern Minnesota. There were four untreated controls and two replicates of each of four diflubenzuron concentrations (0.7, 2.5, 7.0, and 30.0 μg/l). The half-life of diflubenzuron predicted by the fate and persistence model was 4 to 5 times lower than the half-life observed in the littoral enclosure water column. This discrepancy was related to the simplistic nature of the two-compartment (water, sediment) model which represented the water column as a single, fully mixed compartment. The smallest model-predicted LOEC (lowest observed effect concentration), where the effect was a decrease in biomass, was 3.2 μg/l. At this concentration, reductions were predicted to occur in biomass of insects, herbivorous copepods, and amphipods. Field-observed LOECs for the same taxa were 2.5, 0.7, and 0.7 μg/l, respectively. Cladocera was the most sensitive taxon in the field study (LOEC = 0.7 μg/l), but leram did not predict direct toxic effects on this taxon until the diflubenzuron concentration was ≥ 6.4 μg/l. This discrepancy, and leram's general ability to predict effects observed in the field, was directly related to the size and quality of the available laboratory single-species toxicity data base used as input for the model. Indirect effects of diflubenzuron on growth of larval bluegill sunfish was predicted by leram, but at a concentration five times higher than observed. Overall, leram correctly predicted that changes in the littoral community would begin at 0.8 μg/l, with concentrations > 35.0 μg/l yielding negligible new information on effects of diflubenzuron on aquatic biota. Predictions at intermediate concentrations varied in accuracy, with some indirect responses being exaggerated by cascading effects through the trophic levels of the ecosystem.

Effects of Diflubenzuron on Benthic Macroinvertebrates in Littoral Enclosures

Effects of Diflubenzuron on Benthic Macroinvertebrates in Littoral Enclosures

Effects of the Insect Growth Regulator Diflubenzuron on Insect Emergence within Littoral Enclosures

Effects of the insect growth regulator diflubenzuron on insect emergence were investigated in littoral enclosures in a pond in northeastern Minnesota. Adult insects were captured with floating emergence traps before and after each of 2 applications with 4 different diflubenzuron rates. Emergence was reduced by up to 87, 96, and 99% relative to controls 4–8 d after the 1st application with 2.5, 7.0, and 30 μg/liter diflubenzuron, respectively. None of the affected populations returned completely to control levels by the time of the 2nd application. Reductions of ≤18% in insect emergence at the 0.7 μg/liter treatment were not statistically significant. Effects of the 2nd diflubenzuron application were similar to those of the 1st. Based on measured maximum exposure concentrations, the no observable and lowest observable effect concentrations for insect emergence were 1.0 and 1.9 μg/liter, respectively. Concentration-response analyses of the data indicated that the field EC50 for insect emergence inhibition ranged from 1.0 to 1.4 μg/liter, depending on the calculation method and on whether nominal or measured diflubenzuron concentrations were used. The estimated maximum acceptable toxicant concentration for Chironomidae was 0.7–0.8 μg/liter. Overall, significant adverse effects on insect emergence could be expected at diflubenzuron concentrations > 1.0 μg/liter with the length and severity of effect being concentration dependent.

Effects of Azinphos-methyl on the Reproductive Success of the Bluegill Sunfish, Lepomis macrochirus, in Littoral Enclosures

Adult bluegills were exposed to a single application of azinphos-methyl in 12 littoral enclosures in a northern Minnesota pond. Responses measured were adult behavior and spawning, embryo hatchability, larval survival until swim-up, young-of-year (Y-O-Y) growth, and total biomass. Four enclosures each were treated at 1.0 and 4.0 μg/liter and four remained untreated. The half-life of azinphos-methyl was 2.3 and 2.4 days at each of the two treatment levels, respectively. Quantifiable residues remained in the water for 8 days. Concentrations of 4.0 or 1.0 μg/liter did not cause any significant long-term (63 day) effects on bluegill reproduction, embryo hatchability, larval survival, growth, or biomass. Although important bluegill prey such as copepod nauplii and cladocerans were significantly or greatly reduced by Day 7 following treatment, they recovered to levels equal to or greater than some of the control enclosures by Day 35. The apparent lack of significant long-term effects on reproductive success can be partially explained by the relatively short half-life of azinphos-methyl in littoral enclosures.

Distribution and Persistence of Diflubenzuron within Littoral Enclosure Mesocosms

The insecticide diflubenzuron was applied as Dimilin 25W twice, 32 days apart, to the surfaces of 12 of 18 littoral enclosure mesocosms (5×10 m) to study its distribution, persistence, and mass balance in a natural ecosystem. Nominal concentrations were 0.7, 2.5, 7, and 30 μg/L active ingredient. The residue half-life in the water column ranged from 3.3 to 8.2 days with a mean of 4.3 days and required 14-35 days for 95% dissipation. The half-life in the macrophytes ranged from 2.0 to 5.7 days, and 95% dissipation required 8.6-24.6 days. The half-life in sediment ranged from 6.2 to 10.4 days, and 95% dissipation required 26.9-45.0 days. The water was the major compartment for residues, with amounts ranging from 82.3% of that applied after 3 h to 11.6% after 7 days. The sediment and macrophytes had maximum amounts of 6.3 and 10.2%, respectively. The mass balance ranged from 82.3% after 3 h to nondetectable after 56 days

Specificity of choline uptake into syncytial microvillus membrane vesicles of human term placenta: Inhibition by organic cations

The clam Scrobicularia plana and the polychaete worm Nereis diversicolor were collected in several sites from a littoral enclosure in SW Spain. The aim of our study was to relate various biomarker responses in these species to a pollution gradient caused by untreated domestic discharges and to verify the adequacy of the selected species as sentinels in this habitat. The biomarkers selected were the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX) and DT-diaphorase (DT-D). In addition, the activities of cytochrome P450-dependent ethoxyresorufin O-deethylase (EROD) activity, the phase II detoxifying enzyme glutathione S-transferase (GST) and the neurotoxicity marker acetylcholinesterase (AChE) were measured. Metallothionein levels were selected as biomarkers of heavy metals exposure in both species. The results suggest a different response in the water filtering organism (clam) and the sediment eater (polychaete), probably as a consequent of different pollution exposure and that samples from the “Caño Sancti-Petri” were exposed to biologically active compounds that altered some of their biochemical responses. AChE was the most sensitive biomarker in both species and N. diversicolor proved to be a more robust sentinel in this ecosystem.

Field Evaluation of the Littoral Ecosystem Risk Assessment Model's Predictions of the Effects of Chlorpyrifos

The Littoral Ecosystem Risk Assessment Model (LERAM) is described and evaluated using field data from a littoral enclosure study of the effects of the insecticide chlopyrifos. LERAM is a bioenergetic ecosystem effects model that links single species toxicity data to a bioenergetic model of the trophic structure of an ecosystem in order to simulate community and ecosystem level effects of chemical stressors. It uses Monte Carlo iterations of these simulations in order to calculate probabilistic ecological risk assessments of chemical stressors. The means and standard deviations of the model parameters were calibrated using data from the control enclosures in the field. LERAM produced reasonable representations of the ecosystems in the littoral enclosures

Semipermeable membrane devices containing model lipid: A new approach to monitoring the bioavaiiability of lipophilic contaminants and estimating their bioconcentration potential

Low density “layflat” polyethylene tubing containing thin films of model lipid may simulate the bioconcentration of nonpolar organic contaminants by aquatic organisms. These semipermeable polymeric membrane devices (SPMDs) are shown to hold considerable promise as time-integrated concentrators of nonpolar organics in aquatic environments, and as a method for estimating bioavailability and potential bioconcentration factors for contaminants in organisms. The devices may also help define the relative role of equilibrium partitioning in the bioaccumulation of organic contaminants. The use of purified lipid extracts from aquatic organisms or specific lipids, such as triolein, in SPMDs is made more practical by a complementary analytical development showing the utility of polyethylene film as a membrane for dialyzing nonpolar organic compounds from coextracted lipids. Data are presented on the uptake kinetics and steady state distribution coefficients of aqueous residues of fenvalerate, mirex, 2,2′,5,5′-, and 3,3′,4,4′-tetrachlorobiphenyls when lipids are used in SPMDs. The feasibility of the SPMD approach for in situ monitoring of environmental contaminants is demonstrated by exposing SPMDs to Asana R (an isomer of fenvalerate) in a littoral enclosure of a small pond.

A littoral enclosure for replicated field experiments

AbstractA design for 5 × 10 m littoral enclosures that extend 10 m from the shoreline into the zone of submergent vegetation and incorporate undisturbed natural sediments for the bottom is presented and construction techniques are described. This type of enclosure was used to study the responses of caged and free‐living pond biota and the physical and chemical environment to a single application of Dursban® (chlorpyrifos) during the summer of 1986 as part of the development of a field testing protocol for pesticides needed by the U.S. Environmental Protection Agency Office of Pesticide Programs. Chlorpyrifos was added to 12 littoral enclosures built within a mesotrophic, 2‐ha pond near Duluth, Minnesota, at nominal concentrations of 0.0, 0.5, 5.0 or 20.0 m̈g/L. The enclosures proved to be both economical and durable and were useful for detecting direct and indirect (ecological) effects of the pesticide. Coefficients of variation (C.V.) associated with the chemical and biological response variables typically ranged from 10 to 40%. The ability to simultaneously monitor many response variables in replicate enclosures at a relatively low cost suggests that the littoral enclosure design should be useful for studying the effects of pesticide or other pollutant additions to natural aquatic systems.