S1-1.16 Jan. 4 The effects of vertical odor plume structure on navigation and foraging performance in blue crabs WEISSBURG, M*; JACKSON, J; RAHMAN, S; WEBSTER, DR; GA Tech email@example.com
Large marine invertebrate predators (e.g., blue crabs) navigate using odor plumes in turbulent boundary layers. Unfortunately, we know little about the vertical distribution of odors and how it affects navigation. This study used laser-induced fluorescence to examine the information content of plumes at several locations sampled by crab chemosensors. In parallel, we studied crab foraging to link odorant distributions and olfactory search performance, and altered the bed substrate to generate a large range of turbulence levels (u*=3-6; Re*= 0-350). Foraging success declined markedly over the first 2 roughness conditions then remained constant. Increased turbulence decreased odor burst concentration, which disrupted upstream movement and lowered walking speed. Path linearity was unaffected. The steering ability of animals depends on sensors located close to the bed, and is less affected by turbulence because mixing peaks close to the bed to create homogenous odor distributions even when turbulence is low. Odor is transported to the substrate better in rough than in smooth beds. This is advantageous for animals with sensors located close to the substrate, such as whelks, which forage well in turbulent conditions. Close to the source, odor concentration and concentration variance had sharp maxima near the source height, but become almost uniform across depth ca. 80 cm downstream. Profiles were more homogenous with increased roughness. Thus, 3D information may be used for near source decisions (e.g. local search, stopping) but is more limited when turbulence is increased. The ecological impact of fluid flow on foraging decisions and performance may be limited to distances relatively close to the source since plumes converge to similar structures regardless of turbulence level.