MEPS 283:55-71 (2004)  -  doi:10.3354/meps283055

Characteristics of the chemical plume behind a sinking particle in a turbulent water column

André W. Visser1,*, George A. Jackson2

1Danish Institute for Fisheries Research, Kavalergården 6, 2920 Charlottenlund, Denmark 2Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA

ABSTRACT: Many aquatic organisms, from bacteria to crustaceans, use chemical plumes released by sinking particulate organic material either directly as a food source or as a signal to find potential food items (marine snow aggregates, fecal pellets). This work examines how the relevant metrics of the plume (length, volume and cross sectional area) relate to encounter rates and how they vary with turbulence. Total plume length appears to be invariant to turbulent shear rate, although plume volume and cross section do decrease strongly with increased turbulence. Turbulence can also break a plume into multiple segments. The length of the segment connected to the particle (the first unbroken segment) tends to be about 50% of the total plume length, as well as containing about half of the total plume volume and cross sectional area. Despite the complexity of the processes involved, these relationships can be described by relatively simple functions that are revealed both empirically through modelling and through theoretical analysis. The critical parameter is γT0*, the product of the average turbulent shear rate and the diffusive time scale—the length of time a plume would last in calm water. The results highlight the ecological differences associated with different turbulence intensities as a function of depth in the water column.

KEY WORDS: Turbulence · Marine snow · Fecal pellet · Dissolved organic matter · Chemical trail · Encounter rate

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