Metal Tolerance and Predator–prey Interactions in Benthic Macroinvertebrate Stream Communities

Abstract

Predicting responses of benthic communities to contaminants requires an understanding of both direct and indirect effects. I examined the influence of previous exposure to heavy metals on metal tolerance and susceptibility of benthic communities to stonefly predation in experimental streams and field cages. Benthic communities obtained from a reference stream, the Cache la Poudre River (PR), and a metal‐polluted stream, the Arkansas River (AR), in Colorado were exposed to a mixture of Cd, Cu, and Zn at ∼2× the U.S. EPA chronic criterion level (2.2 μg Cd/L, 24 μg Cu/L, and 220 μg Zn/L) for 10 d in stream microcosms. Effects of metals on survival were significantly greater on mayflies (Ephemeroptera) from the unpolluted PR than from the metal‐polluted AR. Metal exposure also significantly increased drift of Rhithrogena hageni, the dominant mayfly in the unpolluted stream but had no effect on invertebrates from the AR. In a second experiment, communities from the two locations were exposed to predatory stoneflies (Claassenia sabulosa) in stream microcosms. Stonefly predation significantly reduced total macroinvertebrate abundance, number of taxa, and abundance of Baetis tricaudatus (Ephemeroptera) and R. hageni. Mayflies from the metal‐polluted AR were also more susceptible to stonefly predation, but these results were probably influenced by differences in initial prey density. Results of caging experiments conducted at PR and AR field sites were consistent with results of laboratory experiments and showed that stonefly predation significantly reduced abundance of B. tricaudatus and R. hageni; however, effects of predation in the AR were relatively weak because of high prey immigration. Results of these experiments suggest that abiotic factors influence the outcome of species interactions in metal‐polluted streams. Ecosystems disturbed by contaminants, particularly those polluted for relatively long periods of time, provide excellent opportunities to study these interactions.

How do aquatic communities respond to contaminants? It depends on the ecological context

“…Similarly, we expect that communities with a long-term history of exposure to a specific stressor would show greater tolerance to that stressor. Microcosm experiments have shown that communities collected from metal-contaminated streams were more resistant to metals compared with reference communities [35]. These patterns are consistent with the pollution-induced community tolerance hypothesis, which states that increased tolerance occurs when sensitive species are eliminated from a community [36].…”

“…Interestingly, the increased tolerance for one set of stressors often results in greater susceptibility to other, novel stressors. Stream microcosm experiments have shown that metal-tolerant communities were more susceptible to acidification [37], UV-B radiation [38], and predation [35] compared with reference communities. These findings suggest that communities retain a long-term record of exposure that may persist long after a contaminant has dissipated or degraded [39].…”

Assessing contaminated sediments in the context of multiple stressors

“…1, Table 1) are less likely to be impacted by contaminated sediments. An exception to this is directly below mining operations where larger grained mine tailings may exist, or where periphyton have accumulated high metal concentrations from the overlying water [81][82][83][84]. The dominant contaminant exposure pathways for aquatic organisms in high-energy systems will tend to be runoff, outfalls, upwellings and downwellings, and food [9,75,[85][86][87][88][89][90][91][92].…”

Macroinvertebrates and Excessive Fine Sediment Conditions in Oregon Coastal Streams

“…Predation by vertebrates and invertebrates affects specific morphological features and behavior of taxa in single-organism experiments (Feltmate and Williams 1991) but in whole-stream studies was found to have a minimal effect on invertebrate assemblage, likely because of high emigration rates from drift or substrate (Thorp and Bergey 1981;Culp 1986;Vinson and Hawkins 1998;Clements 1999) or the effect is masked by high habitat variability (Brown and Lawson 2010).…”