Creatures of the deep

For the last week and a half, we’ve been retrieving ocean bottom seismometers that were deployed in the Gulf of Alaska one and a half years ago. Upon successful recovery, this will be the longest deployment of temporary seafloor seismometers yet. Along with the excitement of hauling new data aboard to study earthquakes and Earth’s structure, some of the creatures that have called our sensors home are providing unexpected entertainment.

fish
A school of Pacific Cod surroundeds ROV Jason on the seafloor. Soon after, an unfortunate pair of cod were blended to a chowder when they swam through Jason’s thrusters.

Jason, the remotely operated underwater vehicle that we are using to recovery steel-shielded seismometers, is surrounded with flood lights and high resolution video cameras that record life beneath the sea surface. As Jason descends to the seafloor, it passes through a near-surface horizon of chlorophyll green imparted by photosynthetic plankton. Below ~50 meters, the water column is dark grey, but not barren. Jellyfish and marine snow, a mixture of krill, zooplankton, foraminifera, worms, and other organic matter, float softly around the vehicle. Near the bottom, we are occasionally visited by schools of Pacific cod, the most curious of which kissed one of Jason’s cameras.

basketstars
A basket star (possibly Gorgonocephalus eucnemis) clings to ropes on the top of  the steel shell of a trawl-resistant ocean-bottom seismometer (top). Basket stars are filter feeders with many branching arms that snag organic material and small swimming creatures from the water (below, from NOAA).

The hard exterior of the trawl-resistant seismometers shelters our instruments and provides a strong surface for filter-feeders and more immobile creatures to attach to. Flaps beneath the steel shielding capture marine mud. When hauled on board, these instruments bring a diverse mix of sea creatures and biological oddities: worms, eggs, sea stars, arthropods, and molluscs. Our job is to clean them off so that the instruments don’t smell like a cannery by the time they are shipped to Massachusetts. We try our best to be novice biologists and guess what they could be.

 

worms
A recovered seafloor temperature probe carries unidentified marine worms and eggs.

 

panel
An assortment of biological stowaways that were hauled aboard on trawl-resistant ocean-bottom seismometers. Clockwise from top left: shrimp, unidentified blob, hermit crab in a triton snail shell, sea urchin, triton snail eggs, and triton snail. All were returned to the sea.

 

 

 

 

 

 

 

 

 

 

 

-Andrew Gase, PhD student, University of Texas – Austin

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