Combined effects of flow speed and sub-lethal insecticide exposure on predator–prey interactions between the California killifish and an infaunal polychaete
Hydrodynamics and pollution affect estuarine populations, but their ecological effects have rarely been studied in combination. We conducted two laboratory experiments to quantify whether predator–prey interactions between California killifish, Fundulus parvipinnis, and the polychaete Polydora cornuta vary with flow speed and chlorpyrifos exposure. In one experiment, only F. parvipinnis was exposed to chlorpyrifos; in the other, only P. cornuta was exposed. The flume included a 300-cm2 area of sediment with 24 P. cornuta in a central patch (98 cm2). We videotaped groups of three killifish for 50 min at one of four flow speeds (6, 9, 12, or 15 cm/s) and recorded the proportion of bites directed at the prey patch. Unexposed killifish directed 70% of their bites at the prey patch at 6 cm/s, and prey-patch selection decreased as flow increased. Killifish exposed to chlorpyrifos directed 41% of their bites at the prey patch at 6 cm/s with reduced prey-patch selection relative to unexposed fish at 9 and 12 cm/s. At 15 cm/s, both exposed and unexposed fish displayed non-selective biting. Worms were videotaped to quantify their deposit- and suspension-feeding activities. Exposing worms to chlorpyrifos reduced total feeding activity by ~30%. Suspension feeding was more common at faster flow speeds, but the time worms spent suspension feeding relative to deposit feeding was unaffected by chlorpyrifos. No behavioral changes were noted in either species when the other was exposed to chlorpyrifos. This study highlights how hydrodynamic conditions can alter the relative importance of a toxicant’s effects on predator–prey interactions.
KeywordsChlorpyrifos Predator–prey interactions Hydrodynamic conditions Estuary Polydora cornuta Fundulus parvipinnis
We thank all the undergraduate assistants whose help made this project possible: J. Allyn, J. Hens, J. Savoie, G. Tice, S. Allwang, K. Richardson, K. Connelly. In addition, we thank three anonymous reviewers for comments that improved the manuscript. We also thank our funding sources, including a Faculty California State University, Council on Ocean Affairs, Science, and Technology (COAST) grant COAST-GDP-2013-004 (to BTH and TWA) and COAST Student Research Award CSUCOAST-HAYNIC-SDSU-AY1314 (to NTH). The flume used in these experiments was purchased using National Science Foundation grant NSF-OCE-0000951 (to BTH). This is Contribution No. 63 of the Coastal and Marine Institute Laboratory, San Diego State University.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted.
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