Blinded by the stink: Nutrient enrichment impairs the perception of predation risk by freshwater snails

Abstract

Abstract. The acquisition of sensory information is central to all species interactions. Most aquatic organisms use chemical cues to assess predation risk and other key ecological factors, but chemoreception may be disrupted in systems with elevated pH. Elevated pH in lakes and rivers is often associated with eutrophication. We used laboratory and mesocosm experiments to test whether elevated pH impairs perception of predation risk by the freshwater snails Physa acuta and Helisoma trivolvis. In one set of experiments, nutrients were added to outdoor mesocosms, resulting in mid-afternoon pH values of 8.5-9.7. Both snail species moved to avoid fish in water with pH , 9.0 but showed no avoidance at higher pH. In a laboratory study, we used buffers to establish six pH treatments ranging from 7.5 to 10.0. At lower pH Physa acuta responded to fish cues by moving into safer habitats, but avoidance became impaired at a pH of 9.4. Helisoma trivolvis also responded to fish at lower pH, and their avoidance behavior became impaired at a pH of 8.8. Given the diversity of aquatic organisms that depend on reception of chemical cues and the broad extent of eutrophication, chemosensory impairment is likely a common occurrence in nature.

Bacterial Community Composition of Size-Fractioned Aggregates within the Phycosphere of Cyanobacterial Blooms in a Eutrophic Freshwater Lake

“…The formation of large mucilaginous cyanobacterial blooms in freshwater lakes restricts light penetration, depleting oxygen levels, thereby reducing water quality adversely affecting the ecosystem [1]. These changes can result in reduction in the numbers of submerged plants, killing of aquatic animals, and alteration in food web dynamics [2]. Furthermore, massive cyanobacterial blooms in eutrophic lakes are dominated by Microcystis spp., which produces toxic microcystins that can prevent water consumption [3].…”

Context‐dependent planktivory: interacting effects of turbidity and predation risk on adaptive foraging

“…For example, Carr and Lima (2010), Turner and Chislock (2010), and Large et al (2011) provide examples of how fast winds, elevated pH, and high water flow velocity, respectively, can disrupt the ability of intermediate consumers (birds, freshwater snails, and marine hard clams, respectively) to perceive predator cues in the air or water, thus leading to a diminished behavioral response of these intermediate consumers to their predator(s). Specific to TMIEs, Kimbro (2012) demonstrated how the tidal regime in the northeastern Gulf of Mexico influenced the ability of snails to detect predator cues in the water, which mediated the use of cordgrass (Spartina alternifolia) by snails as a refuge from top predators (blue crab Callinectes sapidus and conch Melongena corona).…”

Eutrophication of Aquatic Ecosystems: A Viewpoint on the Environmental Impact of Climate Change

“…The high rates of photosynthesis related to the eutrophication deplete the dissolved inorganic carbon and raise pH during the day time, in which the organisms that rely on the dissolved chemical impair their chemosensory abilities for survival [15]. When the algal blooms die, microbial decomposition takes place causing depletion of dissolved oxygen and creating a hypoxic or anoxic "dead zone".…”