Biotic structure indirectly affects associated prey in a predator-specific manner via changes in the sensory environment

Abstract

Indirect effects, which can be either positive or negative, may be important in areas containing biotic structure, because such structure can provide refuge and habitat, produce additional sensory cues that may attract predators, and modify the sensory landscape in which predator-prey interactions occur. To determine the indirect effects of biotic structure on prey populations, we assessed predation on patches of hard clams (Mercenaria mercenaria) by large odor-mediated blue crab (Callinectes sapidus) and knobbed whelk (Busycon carica) predators at 0, 5, and 10 m from oyster reefs in intertidal salt marshes. Oyster reefs had an overall indirect negative effect on hard clams, with higher predation rates closer to the reef than farther away. Predator-specific patterns of predation showed that blue crabs consumed more clams very close to the reef, whereas whelks consumed more clams at intermediate distances. Laboratory flume experiments suggest that the oyster reef structure creates turbulence that diminishes predator foraging efficiency, particularly in rapidly mobile predators such as blue crabs, but that oyster reef chemicals ameliorate the negative impact of turbulence on foraging success for both predators. Changes in the sensory landscape, in combination with predator perceptual ability, will determine the positive and/or negative impacts of biotic structure on associated prey. Gaining an understanding of the context specificity of positive and negative sensory effects of biotic structure provides insights that are important for developing a predictive framework to assess the magnitude and distribution of indirect interactions in natural communities.

Habitat complexity and predator size mediate interactions between intraguild blue crab predators and mud crab prey in oyster reefs

“…Although oyster reef structure provides a predation refuge, oyster reefs can also attract predators by emitting chemical attractants to foraging consumers (Wilson & Weissburg 2012).We confirmed the benefits of oyster reefs as a predation refuge in field tethering experiments, where more mud crabs generally survived in more complex habitats. Mud crabs were recovered from oyster reef habitats at a greater frequency than from shell hash and sand habitats at the PL site (Fig.…”

“…Furthermore, as oysters filter large volumes of water and release chemical cues, they may further facilitate predator aggregation by attracting predators that utilize odor-mediated foraging. For instance, blue crabs and knobbed whelks track oyster chemical cues emanating from reefs, resulting in higher predation rates on clams adjacent to oyster reefs (Wilson & Weissburg 2012). Despite these potential effects, the importance of oyster reef structure in mediating prey survival has rarely been demonstrated in the field and, to our knowledge, has only been demonstrated for bivalve species (Micheli & Peterson 1999, Wilson & Weissburg 2012 and porcelain crabs (Petrolisthes armatus; Hollebone & Hay 2008).…”

The smell of success: the amount of prey consumed by predators determines the strength and range of cascading non-consumptive effects

“…The amount of prey consumed by predators might be predicted to affect prey responses by modulating the amount, or concentration, of bioactive molecules released, which constitute potential cues associated with predation intensity; to our knowledge this effect never has been examined. Some studies deliberately have manipulated predator number, showing that prey responses increase when more predators are allowed to feed on prey ( Chivers et al, 2001 ; Relyea, 2003 ; Hill & Weissburg, 2013b ). This suggests altering the amount of prey flesh consumed by a predator also may mediate responses of focal prey and the consequences for other species (basal resources, competitors) that interact with this prey.…”

“…Blue crabs are an important predator of mud crabs; although blue crabs are generalist and opportunistic feeders, xanthid crabs compose roughly 10–40% of blue crab diets in the field ( Laughlin, 1982 ; Fitz & Weigert, 1991 ) and appear to be a major predator of mud crabs in Wassaw sound ( Hill & Weissburg, 2013a ). The presence of blue crabs ( Grabowski, 2004 ; Hill & Weissburg, 2013b ) or water in which blue crabs were kept ( Hill & Weissburg, 2013b ) reduces activity and foraging in mud crabs, suggesting mud crab responses to blue crab predators are at least partially the result of chemical cues.…”

Assessment of single‐instrument techniques for removing wave bias from Reynolds stress estimates

“…Hydrodynamics are known to impact a variety of ecological processes in estuaries including settlement (Abelson and Denny ; Lenihan ; Whitman and Reidenbach ), predator–prey interactions (Jackson et al ; Webster and Weissburg ; Smee et al ), food availability to the benthos (Butman et al ), anti‐predator behavior (Robinson et al ), and species density and distribution (Lauzon‐Guay and Scheibling ; Wilson and Weissburg ). As a result, accurate measurements of flow characteristics, in particular the turbulent characteristics, are essential in aquatic environments because they are key to understanding context‐specificity in species interactions and community processes in addition to directly influencing the transfer of energy and fluid momentum in the near‐bed environment.…”