Cues, Not an Endogenous Rhythm, Control the Dusk Peak in Water-Column Entry by Benthic Copepods
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Individuals of some benthic species swim out of or away from the sediment surface into the water column, i.e., they emerge. Individuals of both emergent and nonemergent benthic species can be entrained by near-bottom flows. Both emergence and entrainment are of interest, e.g., for their roles in benthopelagic coupling, but the controlling factors are poorly understood. Our experiments with benthic copepods from contrasting environments showed that a factor (or factors) associated with the onset of darkness, rather than an endogenous rhythm, controls their dusk emergence. In addition, we argue that entrainment and emergence can interact in at least two ways: (1) Light-induced changes in oxygenation of the sediment pore water may affect the entrainment flux of benthic copepods and (2) if large numbers of individuals are entrained in the time leading up to sunset, few will remain in the sediment to be part of the dusk peak in emergence.
KeywordsEmergence Benthos Behavior Oxygen Sulfide
D. Oliff built the watertight cases for the light meter and the data logger. C. Hasemann, B. C. Hippolyte, I. Hoedl, G. Hurst, M. Pöhn, L. Sedlacek, K. Suderman, M. Teasdale, and A. Vopel helped in the laboratory or the field. The FSU Academic Diving Program provided equipment and training. The European Union Program “Training and Mobility of Researchers,” the Alfred Wegener Institute for Polar and Marine Research, the Kristineberg Marine Research Station of The Royal Swedish Academy of Science, the Klubban Biological Station of Uppsala University, the Florida State University Coastal and Marine Laboratory, and the Faculty of Health and Environmental Sciences of Auckland University of Technology provided funding and/or equipment.
Conflict of Interest
We do not have financial interests in the organizations that sponsored the research. We have full control of all primary data and agree to allow the journal to review the data if requested. No conflicts of interest exist.
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