PT  - JOURNAL ARTICLE
AU  - David M. Durieux
AU  - Kevin T. Du Clos
AU  - Brad J. Gemmell
TI  - Benthic jellyfish dominate water mixing in mangrove ecosystems
AID  - 10.1101/784173
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 784173
4099  - http://biorxiv.org/content/early/2019/11/08/784173.short
4100  - http://biorxiv.org/content/early/2019/11/08/784173.full
AB  - Water mixing is a critical mechanism in marine habitats that governs many important processes, including nutrient transport. Physical mechanisms, such as winds or tides, are primarily responsible for mixing effects in shallow coastal systems, but the sheltered habitats adjacent to mangroves experience very low turbulence and vertical mixing. The significance of animal mediated biogenic mixing in pelagic habitats has been investigated but remains unclea. In this study we show that the upside-down jellyfish Cassiopea sp. plays a significant role with respect to biogenic contributions to water column mixing within its natural habitat. The mixing contribution was determined by means of high-resolution flow velocimetry methods in both the laboratory and in the natural environment. We demonstrate that Cassiopea sp. continuously pumps water from the benthos upward in a vertical jet with flow velocities on the scale of centimeters per second. The volumetric flow rate was calculated to be 212 l h−1 for average sized animals (8.6 cm bell diameter), which translates to turnover of the entire water column every 15 minutes for a median population density (29 animals m−2). In addition, we found Cassiopea sp. are capable of releasing porewater into the water column at an average rate of 2.64 ml h−1. The release of nutrient-rich benthic porewater combined with strong contributions to water column mixing, suggest a role for Cassiopea sp. as an ecosystem engineer in mangrove habitats.Significance Statement Water mixing is a critical process for aquatic life. Coastal mangrove habitats are vital nurseries for many commercial and ecologically important species, but these highly sheltered habitats experience very little water mixing. The upside-down jellyfish, Cassiopea sp., occurs in mangrove habitats around the world at densities of up to 100 animals m−2. Each jellyfish lives on the bottom and pulses nearly continuously, producing a vertical current that transports hundreds of liters per hour of seawater. This results in turnover of the entire water column every 15 minutes in an average population. In addition, Cassiopea sp. can greatly expedite the release of nutrient-rich water from sediments and transport these nutrients into the water column. This study demonstrates that the upside-down jellyfish represents a previously unrecognized ecosystem engineer that can affect primary productivity, nutrient distribution, and alter new habitats as their range is expanding.