The Consumption of Marine Snow by Macrozooplankton and Its Impact on Aggregate Abundance In Situ

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Consumption of maarine snow (detrital aggregates0.5 mm) by zooplankton has the potential to be one of the mosst significnt pathways altering the size distribution and abundance of large sinking particales in the ocean and has been hypothesized to be a major cause of the exponential decrease in particulate flux with depth below the mixed layer. Yet almost nothing is known about the ability of pelagic animals to consume lare aggregates. We propose investigations of two of the potentially most important macrozooplankton consumers of marine snow, euphausiids and doliolids. Field observaations and preliminary experiments in our laboratory cleary demonstrate that these animals voraciouslly consume marine snow. We propose to 1) quantify the consumption of marine snow by Euphausia pacifica and Doliioetta gegenbauri as a function of the size, type and quality of aggregates offered, the size and hunger state of the animals, and the avialbility of alternate suspeended food sources, and 2) assess the impact of aggregate-conssuming macrozooplankton, especially vertically migrating euphausids, on the aabundance and vertical distripbution of marine snow in coastal surface water.