Abstract
Decaying gelatinous zooplankton (GZ) originating from surface waters has
been proposed as a possible major contributor to the biological carbon
pump. However, studies arrived at largely diverging conclusions
concerning the role of decaying GZ as organic matter supply for the
deep-sea heterotrophic biota. We complement previous approaches to GZ
sinking by proposing the first dynamically consistent physical model
coupling GZ sinking speed and its mass. We evaluate GZ contribution to
deep-ocean carbon sequestration and to the soft-tissue carbon pump by
solving the model equations on the global ocean grid employing monthly
climatological temperature fields and published exponential and linear
temperature dependencies of mass decay rates. We present the global
ocean distribution of the fraction of GZ-mass sinking out of the
euphotic zone (200 m depth), twilight zone (1000 m depth) and the
fraction of mass reaching the global ocean floor. Solutions in the upper
water column are strongly dependent on the mass decay rate. Since most
of the decay happens in the initial phase of the sinking process, the
sinking-decay coupling exerts a substantial impact on sinking rates but
has limited effect on the fraction of mass reaching the bathypelagic and
abyssal ocean. Our model approach indicates that there are substantial
latitudinal differences in the potential supply of GZ detrital matter to
the deep sea. While at low latitudes only negligible amounts of GZ
biomass are deposited at the ocean floor, high latitudes allow for
substantial GZ detrital mass transport to depths below 1000 m.