MEPS 505:107-117 (2014)  -  DOI: https://doi.org/10.3354/meps10775

ABSTRACT: The presence of zooplankton swimmers and carcasses in sediment trap samples has long been a concern in particle flux studies. We successfully developed a protocol using the vital stain Neutral Red to distinguish between copepod swimmers and carcasses in conventional cylindrical sediment traps. Swimmers were stained red whereas carcasses were pale or unstained. The color distinction allowed easy quantification of the two. We subsequently used the protocol in Otsuchi Bay, Japan, on 4 consecutive days in May and again in July 2013. Carcasses were present in the sediment traps on all occasions, and calanoid and cyclopoid copepods accounted for 60.0-93.6% of all carcasses. Swimmers were 1-2 orders of magnitude more abundant than carcasses, with cyclopoid copepods accounting for up to 75.6% of all swimmers. Copepod carcass flux was negatively related to current velocity at the trap depth. Overall, inclusion of copepod carcasses added no more than 10% to the total particulate organic flux, whereas inclusion of swimmers increased the particulate carbon flux by as much as 87.4%. The low C:N ratio of the other trap materials suggests that sinking particles were a high-quality food source for the benthos in Otsuchi Bay.

KEY WORDS: Swimmers · Carcasses · Sediment traps · Neutral Red · Particle flux