Large Jelly Fall in the Flume

A large jellyfall is created in the NIOZ flume using mimic jellyfish.  The jellyfish cover 1/4 of the surface area of the experimental flume space. 

Freshly prepared mimic jellies 

NIOZ adv sampling the fluid velocity and turbidity around the mimic jellyfall. 

NIOZ Cheesecake Bakeoff

A bit of baking as a break from the flume.  Even better when everyone at NIOZ can benefit and an opportunity to say thank you for another great visit.  

The competitors

NIOZ Flume

Mimic jellyfish in the flume at NIOZ ready for some profiling to examine the effects of jellyfish carcasses on fluid dynamics.  

Acoustic Doppler Velocimeter collected data on the flow velocities around a mimic jellyfish 

Flow velocities are being measured around mimic jellyfish in the NIOZ flume to determine the effect of the fall of jellyfish carcasses on the benthic environment.  Our aim is to create flow conditions similar to those found in the deep fjords of Norway inside the flume (slow flows between 2 and 10 cm per second).

The Acoustic Doppler Velocimeter (ADV) is on a robotic arm that allows velocity profiles to be made all around and above the jellyfish carcass.  

Artificial Jellyfish Production

Artificial Jellyfish Flume Experiments

The effect of jellyfish carcasses on fluid dynamics at the seafloor has not been investigated.  Therefore, in April Kathy Dunlop is conducting experiments in flume at the Royal Netherlands Institute of Sea Research (NIOZ).  

First the board on which to place the artificial jellyfish (made of moulded agar) was made and an artificial jellyfish tested in the flume to ensure that it didn't float.

Creating the experimental board to insert into the flume. 

First artificial jellyfish in the flume

Jellyfish Decomposition Studies at IRIS.

Sediment cores collected in Hardangerfjord were used to examine the ammonium, sulphide and oxygen levels produced by decomposing jellyfish.  This information is needed to understand the dynamics of scavengers feeding on jellyfalls.  For example, it is reasonably to hypothesise that scavengers are discouraged from feeding on jellyfalls if high levels of ammonium and sulphides are produced, and oxygen is reduced during decomposition.

Jellyfish carcasses were added to sediment cores to simulate a jellyfall.

The size of jellyfalls is also hypothesised to affect the levels of ammonium and sulphide produced therefore relatively small, medium and large amounts of jelly fish material were added to the cores.

Cores were sampled periodically over 36 hours to examine changes in ammonium, sulphides and oxygen.  This information will be used to interpolate results from the scavenger deployment studies conducted in June 2016 and 2017.  

Creating Artificial Jellyfish

The benthic boundary layer is the layer of water above the sediment which is important for the  biogeochemistry of the oceans as it is the site of significant organic matter cycling.   The effect of the deposition of jellyfish carcasses on the seafloor and the benthic boundary layer is unknown however, it is thought that the presence of jellyfalls, particularly large falls, will induce a change in benthic boundary layer flow dynamics.

The Jelly-Farm Project is setting out to test whether the physical presence of jellyfish carcasses will induce "skimming flow" in the benthic boundary layer.  Skimming flow is when fluids find it easier to flow over rather than around objects.  It is thought that skimming flow over jellyfish carcasses would result in a thicker diffusive boundary layer and a reduction in oxygen flux to the sediments.  Such an impact would significantly affect organic matter cycling on the seafloor.  

In April flume experiments will be conducted to simulate and provide initial results to determine the effect of relatively small, medium and large jellyfalls on the benthic boundary layer.
 Today prototypes of artificial jellyfish carcasses were created in the lab at IRIS.  

Test materials for making artificial jellyfish carcasses. 

A disney ball used as a mould for an agar artificial jellyfish.  A screw is used as a weight to keep the jellyfish anchored to the sediment during the flume experiments.  

A smaller jellyfish mould prototype with washer weight.