Population Consequences of Fipronil and Degradates to Copepods at Field Concentrations: An Integration of Life Cycle Testing with Leslie Matrix Population Modeling

Department of Environmental Health Sciences, Norman J Arnold School of Public Health, University of South Carolina, Columbia, South Carolina 29208, USA.
Environmental Science and Technology (Impact Factor: 5.33). 01/2005; 38(23):6407-14. DOI: 10.1021/es049654o
Source: PubMed


The predominant data used in ecological risk assessment today are individual-based rather than population-based; yet environmental policies are usually designed to protect populations of threatened species or communities. Most current methods in ecotoxicology are limited by largely logistic/ technology-driven requirements that yield data for a relatively small number of test species and end points that focus on acute lethality or sublethal nonproduction-based parameters (e.g., biomarkers, mutagenesis, genetic change, physiological condition). A contrasting example is presented here showing the predictive ability of meiobenthos-based full life cycle toxicity testing to extrapolate multi-generational effects of chemicals on variables of import to population growth and maintenance. Less than 24-h-old larvae of a meiobenthic copepod were reared individually in 96-well microplate exposures to parent and degradates of the phenylpyrazole insecticide fipronil. Survival, development rates, sex ratio change, fertility, fecundity, and hatching success were tracked daily for 32 d through mating and production of three broods in spiked seawater. These data were then inserted in a Leslie (Lefkovitch) matrix stage-based population growth model to predict relative rates of population increase (lambda) and changes in net population growth with time and toxicant concentration. Field-reported test concentrations produced strong reproductive (52-88%) and net production (40-80%) depressions for parent (at 0.25 and 0.5 microg/L), desthionyl (0.25 and 0.5 microg/L), and sulfide (0.15 microg/L) moieties as compared to controls. Spiked sediment exposures of 65-300 ng of fipronil/g of dry sediment yielded significantly reduced production rates per female that were 67-50% of control production. The consistent reproductively linked impacts of fipronil and its degradation products at the population maintenance levels suggest risks to sediment-dwelling crustaceans at concentrations well below noneffects for most aquatic test species based on risk assessment data from primarily acute and sub-life cycle toxicity tests.

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    • "ological relevancy compared to ap - proaches based on the organism level ( Forbes and Calow , 2002 ; Stark et al . , 2004 ; De Mott et al . , 2005 ; Raimondo et al . , 2006 ) . Matrix population models were recognised as particularly valuable tools to predict toxic effects on population dynamics ( Forbes et al . , 2009 ; Salice and Miller , 2003 ; Chandler et al . , 2004 ; Bin - Le and Yaobin , 2009 ; Charles et al . , 2009 ) . The method is promising under the condi - tion that detailed descriptions of life - histories and robust datasets on biological effects of ionising radiations are available for reliability of model predictions ( Klok and de Roos , 1996 ) . However , predictions may be put under q"
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