Turbine fuels are often the only aviation fuel available in most of the world. Turbine fuels consist of numerous constituents with varying water solubilities, volatilities and toxicities. This study investigates the toxicity of the water soluble fraction (WSF) of JP-4 using the Standard Aquatic Microcosm (SAM). Multivariate analysis of the complex data, including the relatively new method of nonmetric clustering, was used and compared to more traditional analyses. Particular emphasis is placed on ecosystem dynamics in multivariate space.The WSF is prepared by vigorously mixing the fuel and the SAM microcosm media in a separatory funnel. The water phase, which contains the water-soluble fraction of JP-4 is then collected. The SAM experiment was conducted using concentrations of 0.0, 1.5 and 15% WSF. The WSF is added on day 7 of the experiments by removing 450 ml from each microcosm including the controls, then adding the appropriate amount of toxicant solution and finally bringing the final volume to 3 L with microcosm media. Analysis of the WSF was performed by purge and trap gas chromatography. The organic constituents of the WSF were not recoverable from the water column within several days of the addition of the toxicant. However, the impact of the WSF on the microcosm was apparent. In the highest initial concentration treatment group an algal bloom ensued, generated by the apparent toxicity of the WSF of JP-4 to the daphnids. As the daphnid populations recovered the algal populations decreased to control values. Multivariate methods clearly demonstrated this initial impact along with an additional oscillation seperating the four treatment groups in the latter segment of the experiment. Apparent recovery may be an artifact of the projections used to describe the multivariate data. The variables that were most important in distinguishing the four groups shifted during the course of the 63 day experiment. Even this simple microcosm exhibited a variety of dynamics, with implications for biomonitoring schemes and ecological risk assessments.

In this paper we present the community conditioning hypothesis, “ecological communities retain information about events in their history.” This hypothesis, which was derived from the concept of nonequilibrium community ecology, was developed as a framework for understanding the persistence of dose‐related responses in multispecies toxicity tests. We present data from three standardized aquatic microcosm (SAM) toxicity tests using the water‐soluble fractions from turbine fuels (Jet‐A, JP‐ 4, and JP‐8). In all three tests, the toxicants depressed the Daphnia populations for several weeks, which resulted in algal blooms in the dosed microcosms due to lower predation rates. These effects were short‐lived, and by the second and third months of the experiments, the Daphnia populations appeared to have recovered. However, multivariate analysis of the data revealed dose/response differences that reappeared during the later part of the tests, often due to differences in other consumers (rotifers, ostracods, ciliates), or algae that are not normally consumed (filamentous green algae and bluegreen “algae”). Our findings are consistent with ecological theories that describe communities as the unique product of their etiologies. The implications of this to environmental toxicology are that almost all environmental events leave lasting effects, whether or not we have observed them.

Ecotoxicological information for most contaminants is limited to a small number of taxa, and these are generally restricted to comparatively hardy organisms that are readily extractable from test media and easily identifiable. Advances in DNA sequencing can now provide a comprehensive view of benthic invertebrate diversity. The authors applied 454 pyrosequencing to examine the responses of benthic communities in microcosms exposed to sediments with elevated concentrations of triclosan, the endpoint being eukaryl communities that have successfully vertically migrated through the manipulated sediments. The biological communities associated with the 3 treatments (control triclosan, low triclosan [14 mg/kg], and high triclosan [180 mg/kg]) clustered into 3 groups: control/low (n = 6 controls and 4 low), moderate (n = 2 low), and high (n = 5 high). One sample was discarded as an outlier. The most pronounced change as a response to triclosan was the loss of number of metazoan operational taxonomic units (OTUs), indicative of the control/low and moderate groups, with this being most evident in the range of taxa associated with the classes Chromadorea and Bivalvia and the phylum Kinorhyncha. The authors also describe a range of other taxa that aided discrimination between the groups; compare findings with traditionally obtained meio- and macrofaunal communities obtained from the same experiment; and illustrate some of the advantages and limitations associated with both the molecular and traditional approaches. The described approach illustrates the capacity for amplicon sequencing to provide ecologically relevant information that can be used to strengthen an understanding of how sedimentary communities respond to a range of environmental stressors.

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Abstract-In this paper we present the community conditioning hypothesis, ''ecological communities retain information about events in their history.'' This hypothesis, which was derived from the concept of nonequilibrium community ecology, was developed as a framework for understanding the persistence of dose-related responses in multispecies toxicity tests. We present data from three standardized aquatic microcosm (SAM) toxicity tests using the water-soluble fractions from turbine fuels (Jet-A, JP-4, and JP-8). In all three tests, the toxicants depressed the Daphnia populations for several weeks, which resulted in algal blooms in the dosed microcosms due to lower predation rates. These effects were short-lived, and by the second and third months of the experiments, the Daphnia populations appeared to have recovered. However, multivariate analysis of the data revealed dose/response differences that reappeared during the later part of the tests, often due to differences in other consumers (rotifers, ostracods, ciliates), or algae that are not normally consumed (filamentous green algae and bluegreen ''algae''). Our findings are consistent with ecological theories that describe communities as the unique product of their etiologies. The implications of this to environmental toxicology are that almost all environmental events leave lasting effects, whether or not we have observed them.