When you’ve spent a long time immersed in the world of oceanography, it’s easy to forget that not everyone speaks your lingo in their daily lives. Someone outside of the ship might be surprised to hear us casually mention a monster onboard: the MOCNESS! Fortunately this is one beast we can (mostly) control. The MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) is a set of ten nets that can be closed at discrete depths, allowing us to sample and compare planktonic organisms from up to ten different parts of the water column. The MOCNESS also has environmental sensors (temperature, salinity, and fluorescence) which collect concurrent physical water measurements to produce a whole picture of the slice of ocean we sample.
Discrete-depth sampling helps us determine things like: how often and far plankton taxa move up and down in the water column throughout the day (many plankton undergo a daily cycle of vertical migration hundreds of meters up and down), whether certain types of plankton prefer specific water depths, and how plankton distributions change in high- versus low-productivity water masses. In the context of our current cruise to study a newly-upwelled, high-productivity filament off central California, the MOCNESS can also cue us in to how water column distributions change between nearshore and offshore waters, and within the filament as it evolves through time.
This afternoon’s MOCNESS brought up mainly euphausiids (krill) and a few mall fishes, but stay tuned for exciting hauls, especially from the night tows! We are halfway through our second cycle, which means we have two more MOCNESS tows for this round (one tonight, one tomorrow afternoon), along with the usual CTDs, Bongo net tows, and various drifter deployments. After a few brushes with the Navy’s missile testing schedule, we have been cleared to keep tracking our filament. Science stands strong!
Posted by: Laura Lilly, SIO