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Hiking in the Deep Sea

posted Jul 8, 2012, 6:30 PM by Shannon Casey   [ updated Jul 9, 2012, 9:55 AM ]
As the chief scientist, Christina Frieder, explained in our opening blog, we aimed to use Scripps Institution of Oceanography’s Remotely Operated Vehicle (ROV) as our eyes to the deep sea, as a means to “hike” underwater to areas previously unknown or unseen. San Diego County has a complicated geology that offers a variety of habitats to explore. On land, hikers have easy access to a variety of hiking trails spanning from the beaches of Torrey Pines to peaks, such as Iron Mountain, and everything in between including canyons and plateaus. Areas with simpler geological formations lack this variety. What may be surprising to you is that many of these same qualities also hold true underwater within ocean (i.e. beaches, mountains, canyons, and plateaus). The reason why many of these areas aren’t as well known is because until now they have been difficult and expensive to access. With Scripps Institution of Oceanography’s ROV it may be possible to start seeing these environments more frequently.

Obviously, going to the seafloor is much different than preparing for a day hike at Torrey Pines or Iron Mountain. The deep sea is cold, dark, there is more pressure, and of course seawater itself has its own properties to contend with. To get us there the scientists onboard rely on the capable hands of the Scripps ROV operations team including pilots, engineers, and research and informational technology technicians. Think of the operations team as our guides along the hike that ensure the Scripps ROV gets to the areas of interest and that the instruments function. For our dives, our preparations included logs for our observations, a CTD to provide a context for understanding the environment (see Kirk Sato’s blog), and a collection box to safely store samples of interest. In an earlier blog, my colleague Amanda Netburn, describes some aspects of the ecosystems we targeted.

As I write, we’ve already conducted three dives and have the possibility for a fourth dive to look for methane seeps. We’ve seen some things that we were expecting and others we were not. As Amanda mentioned, I am interested in studying the seafloor. For these first dives I targeted the muddy plains habitat. These areas are one of the biggest habitats in the world and the coastline of San Diego is no exception. There are lots of muddy plains along our coast. On land if you were to try to walk on it you’d probably sink and have a hard time moving around. But with the ROV we were able to effortlessly glide over it for the most part. The deepest depth recorded was at 405m (~4 football field lengths). I’ve included a couple of snapshots from video taken from our descent and from transects taken while exploring the seafloor.

Photo: An octopus group mixed with a group of squid at 100m depth. Although market squid (i.e. calamari) are common, the mixed grouping with octopus was unexpected. Octopus lack the pair of tentacles that squid have (both animals have eight arms). In the photo, the organisms in the foreground are octopus and in whereas organisms in the background are squid.

Photo: A view of some of the common species along the seafloor at 400m depth. Although normally dark, the seafloor is illuminated with lights on the ROV and the temperature was a chilly 45° F. The balloon-like structure pictured on the bottom left (arrow) has been identified as a benthic jellyfish that lives among the urchins and seastars that dominate these communities.

Photo: An example of one of the sea urchin species that dominates the
seafloor off of San Diego at 400 m depth.
Photo credit: Amanda Netburn.

Photo: A common fish, hake, seen along the muddy seafloor.
Hake are important for commercial fisheries and for the ecology.

These photos represent just a few of the many organisms that we saw during our first dives. Data from the dives will be used to better our understanding for how bottom dwelling organisms interact with the waters above them, including important fisheries species such as calamari and spot prawn. With continued study, we’ll learn how they are affected by changing currents and water masses impacting our coast (e.g. ocean acidification). As mentioned previously, all of this is happening close to home. Although these images may look foreign, all were taken less than four miles from our coastline. Just like Torrey Pines and Iron Mountain, these areas are distinctly San Diegan.

-- Michael Navarro, Scripps Graduate Student