Rock ‘n Roll Again
At this writing, we’re heaving up and plunging down, leaning port then careening starboard, over and over again. Yep, the sea surface is definitely lumpy and bumpy. Monty Priede, our intrepid cruise leader, will be modifying yet another daily activity schedule. He continues to scheme and dream, sifting through the daily weather forecasts and shifting the research tasks to maximize what we can learn about the deep, dark and hyperbaric realm in the time available.
Expect the unexpected is one way of describing the variability in faunal diversity, distribution and abundance we experience each time we enter King Neptune’s domain. Diving the ISIS ROV continues to be exciting and always provides a surprise or two about life in the deep sea. A pelagic plunge begun yesterday afternoon landed back on deck in the wee hours this morning. During a journey through the water column, a vast fluid world comprising about 99% by volume of the inhabitable space on this planet, we’re always surrounded by a soup of particles, some living and some detrital, some suspended and some sinking. The various mixtures nurture the drifters, crawlers and burrowers below. On this journey to 2600 m we searched for elusive gelatinous carnivores (ctenophores, siphonophores and medusae) and puffy detritus feeders (appendicularians). Finding and collecting these so-called jellyfishes can be challenging because such animals are soft-bodied and easily fragment unless sampled very gently. Consequently, their presence, persistence and ecological roles continue to be underrated, and often unknown. Last night the “hottest” sectors above the Mid-Atlantic Ridge, in terms of the numbers and kinds of various jellies, occurred in the lower mesopelagic (700 to 1000 meters down) and in the benthic boundary layer (just centimeters above the seafloor). High-def video records highlighted gossamer ctenophores, stringy siphonophores, and whispy medusae. We also encountered a slender, 30-cm long squid with feathery-looking arms, seemingly sleeping in mid-water. Attempts to collect wily, undescribed appendicularians were unsuccessful but ROV pilots, David Edge, Bob Keogh, James Cooper, Simon Dodd and Peter Mason, did scoop and slurp delicate dark red blobs (unknown trachymedusae and cydippid ctenophores) and translucent holothurians (two different species) that cruised close to the bottom. Shortly before ascending, Andy Gooday and Andrey Gebruk, directed sampling with several coring tubes, which were pushed into the sandy, pteropod-rich sediments to collect giant forminiferans.
A relatively huge (ca. 2 cm diameter), amoeboid protozoan called a formaminiferan. This representative of an encrusting deep-sea animal (Discospirina) is characterised by a very thin, discolidal test having chambers incompletely subdivided by internal septa. Knowledge of the assemblage composition of large benthic foraminiferans in relation to environmental conditions provides information needed to interpret fossil records.
Once the ROV was on deck, the planktonic animals were offloaded and waltzed to the “cold room” where David Shale spent several bone-chilling hours digitizing their contrasting colors and swimming antics in aquaria and a specially-designed kriesel.
One of the mysterious trachymedusa (possibly Crossota, ca. 35 mm wide) that occur near the bottom of the deep sea in all the oceans. The plethora of tiny tentacles around the umbrella must allow this animal to capture and consume small bottom-living crustaceans, but its feeding behavior has never been observed
An enigmatic holothurian (Peniagone) that meanders close to the sea floor. The translucent body (ca. 10 cm long) is gelatinous with a broad, anterior brim overlying a mouth connected to a spiral, transverse gut filled with sediment. The posterior feet are fused into fan-shaped lobes that aid in locomotion.
The next shipboard activity was the deployment of the mega-multi-coring platform by the Stig and crew. Shortly after retrieval of this gear and the cartridge loads of sediment, strong winds commenced and further over-the-side activities were suspended.
We’re not finished yet; there’s still more sampling and observing to accomplish. Stay tuned.
“After all, I guess it doesn’t matter whether you look down or up, as long as you look.”
[Ed ‘Doc’ Ricketts – in John Steinbeck’s novel, Sweet Thursday]