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March 25, 2003: Leg 3, Day #14

Pescadero Basin

[This is Steve Haddock taking a turn to report on some of the things we have been finding during the blue-water SCUBA dives.]

Being far from shore has certain advantages. On moonless nights, the stars reach all the way to the horizon, and on windless days the ocean stretches out invitingly in all directions. Windless days are critical for blue-water diving, as we can’t operate effectively if it is blowing more than 15 knots. Today is one of the windy days, and I’m not yet sure how I feel about being unable to dive. I always love jumping in and seeing what bewildering variety of species is assembled, but this break forces me to rest up and perhaps catch up with the interesting things we have been accumulating. We have been very fortunate so far. We have been able to SCUBA dive on 9 of the 12 possible days, and each dive has been unique and surprising.

Mar25_s_Rob-through-sample.jpg (16606 bytes)Blue-water diving is essentially diving up in the water-column, where your only frame of reference is a system of lines and tethers connecting you back to a small inflatable boat. You might think that the shallow-dwelling plankton would be well understood, but in the same way that the ROV lets us examine siphonophores, ctenophores, polychaetes, and the occasional radiolarian, SCUBA diving gives us a unique perspective on the fragile organisms that can’t be obtained by typical method such as net tows. In addition to the diversity of these gelata, we have been focusing on how they behave in their normal environment and the relationships between organisms.

Abundant siphonophores greeted us on our first dives. This was good news, since several of us are interested in them, but they took our breath away in more ways than one: their potent stings set our lips and hands on fire. After suffering through this medley of electric shock+nettle+burning, Karen and I decided to make face shields out of pieces of lycra. So now in addition to breathing like Darth Vader, we look like him as well. Mock us all you want, but we have been sting-free since then!

Mar25_ss_OxyOcy8961.jpg (26360 bytes)Our Mexican collaborator Rebeca Gasca is interested in parasitic crustaceans called amphipods, which are usually examined after being preserved from plankton tows. On our SCUBA dives, we have witnessed numerous relationships between amphipods and their gelatinous hosts. For example, the amphipod Oxycephalus has chosen this unfortunate lobate Ocyropsis to be a nursery for her children. In a plankton net, the relationship between the two would have been lost (not to mention the ctenophore would have been shredded into unidentifiable goo).

Mar25_s_bradHetero.jpg (21632 bytes)Brad Seibel has been doing some of his first blue-water dives on this trip.He thinks we have been lying to him for all these years, because the pelagic molluscs which he studies have been the most abundant organisms on the majority of our dives. He has been working a lot on the respiration of heteropods (in the foreground of this video grab), which roam across our aqueous savanna like elefantitos.

Some of the predator-prey relationships we have seen are also quite unique. How else would we be able to observe the struggle between a siphonophore and a polychaete other than by joining them in their own environment? In the picture below, the alciopid has been snared by an Athorybia, and has released a defensive red ink cloud. In a cascade of parallels, we have also found the alciopid parasitic on a lobate ctenophore, and there is another lobate ctenophore that releases nearly identical red ink clouds! 

Mar25_s_AthorybiaAlciopid.jpg (7233 bytes)On the dives in the Farallón Basin, we had an amazing spectacle: the giant larvacean Bathochordaeus, which we see at around 200 meters in Monterey, was abundant up at 15 meters! It was strange to be able to swim up and poke (gently) something that you have always considered a midwater organism. And, we were able to make close-up observations of its filter structures on behalf of Bill Hamner.

One of my favorite finds on this trip is the ctenophore I call “picocydippid”. This amazing creature is bright blue with purplish lips, swims frenetically, and measures in at just over one millimeter long (yes millimeter), while its tentacles stretch out for at least 40 times that length. Many of the copepods we are seeing are bigger than this little guy! Because of its morphology, I’m fairly sure it is an adult and a new species as well. I caught one on our expedition to Hawaii, but it was rudely eaten by another ctenophore in the same jar before I could examine it. This time I was able to take photos and document it as best as I could aboard the ship.

That I could take decent pictures through our dissecting microscope is just one indication of how great a working environment the R/V Western Flyer provides! I’d like to thank the crew for giving us steadfast diving support, with all the extra effort required in launching and tending the boat.

So far the Gulf has had plenty to offer. The hazy blue water, a mix of tropical and gulf waters, is indicative of the productivity of the northern area and the influence of the warm oceanic water from the south. There have been many fascinating sights, like marea roja (red tide) a dense and dark monoculture of dinoflagellates that was less than half a meter thick, medusae dividing by fission, and siphonophores with specialized sections along the length of their tails. We look forward to more discoveries as we continue our visits to the realm of the gelata.

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