The Ocean Food Web: II

Gulf of Maine Expedition, Part 2

contributed scientific chronicles from the Harbor Branch Oceanographic Institute At-Sea

The Johnson Sea-Link (JSL) manned submersible allows scientists to gain a better understanding of the distribution and behavior of pelagic animals that are too delicate to be adequately studied with traditional approaches. This expedition was made possible through a grant from the Biological Oceanography Program of the National Science Foundation (NSF) with additional support from Harbor Branch


THE MAINE EVENT: FALL 2003
Predation by Gelatinous Zooplankton in the Gulf of Maine

MISSION DISPATCH 9 Saturday, September 20, 2003
Location: Georges Basin (42° 19’N, 67° 30’W)

Dispatch by Harry Breidahl – Marine Education Society of Australasia [MESA]

At 7.15 am (that’s 0715 hours, if we use the ship’s 24 hour clock) the R/V Seward Johnson pulled away from the dock at Gloucester, Massachusetts and headed out to sea once again. Both near the shore and well out to sea we were shrouded in marine fog produced by the warm, moist winds from Hurricane Isabel meeting the cool waters of the Gulf of Maine. Thankfully the seas were not as unsettled as expected but they were lumpy enough to bring back that familiar zig-zag stagger we all acquire as we make our way about the rolling vessel.

Captain Ralph van Hoek began sounding the fog horn as we departed the dock at Gloucester. Despite passing through a couple of partially sunny patches, the fog horn was still moaning at 8.15 pm (2015 hours ship time) when we arrived at Georges Basin. By this time the marine fog had really set in. After three days on shore the whole science party was inching to get JOHNSON SEA-LINK II (JSL II) back into the water but the fog put an end to that possibility. With visibility close to zero it was unsafe to launch, or more importantly recover, the submersible.

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Maine sunset
Credit: HBOI/At-Sea.org

This news came as a blow to the scientists but there was an alternative. In our case, we opted to deploy another vehicle that was sitting on the aft deck, unused to date. This technology is a rather ungainly but colorful concoction of pipes, cables, electric motors, lights and cameras called an ROV (ROV = Remotely Operated Vehicle). An ROV is an unmanned, deep-sea exploration platform that is lowered into the sea via a cable and controlled by an operator who remains on board. For tonight the ROV’s cameras would replace human eyes. The ROV controller was Alan Fuller, one of the sub crew, and he ‘piloted’ the ROV from inside a small shipping container on the 01 deck of R/V SEWARD JOHNSON.

The sub crew were able to set-up the ROV quickly and by 9 pm (2100 hours ship time) it was on its way down to 700 feet (just over 200 meters). Once the ROV had been launched, we were all keen to follow its progress but the small control room was crammed with electronic gear, TV monitors and the like. It was so cramped that we had to take turns to step into and out of the container to watch the ROV’s monitors that showed the distribution and abundance of undersea creatures.

Part of this exercise was a trial to see how effective this particular ROV would be as a research tool. Other oceanographic research institutions use ROV’s extensively but in our case it was quickly revealed that the ROV was far more limited than human observers in a submersible, such as JSL II. The TV images transmitted by the ROV only covered a small field of view but did return some interesting results, especially as the ROV returned to the surface. In the last 130 feet (40 meters) over 20 colonies of Nanomia cara were seen as sinuous, ghostly images on the main TV monitor. They were surprisingly close to the surface, with one Nanomia cara seen just at 10 meters (32 feet).

Once the ROV had completed its mission and was secured on deck, a MOCNESS net tow was launched into the foggy mist. Another tow will be conducted tomorrow morning, followed by a CTD cast. We’re hoping that warm sunshine will clear the air and allow a sub dive at 1.00 pm (1300 hours ship time) and then again at 8.30 pm (2030 hours).

Today’s Feature Creature – Beroe cucumis – by Brian Ortman
Thus far for The Maine Event 2003 cruise my favorite animal is the ctenophore Beroe cucumis. Ctenophore is the scientific name for a group of gelatinous creatures commonly known as comb jellies. While most ctenophores eat zooplankton, Beroe preys exclusively on other jellies, in this case Bolinopsis infundibulum. We have captured Beroe ranging in size from less than an inch (2.5 cm) to a foot (30 cm) in length. They are football-shaped and are essentially nothing more than a large mouth that opens into a giant stomach. These predatory jellies can stretch to ingest organisms larger than themselves. Beroe are perfectly adapted eating machines and are truly the "Jaws" of the midwater jelly world.

MISSION DISPATCH 10 Sunday, September 21, 2003
Location: Georges Basin (42° 18’N, 67° 30’W)

Dispatch by Harry Breidahl – Marine Education Society of Australasia [MESA]

Our second day at Georges Basin and the weather is thankfully on the improve but we are still surrounded by marine fog. The working day began before breakfast a with MOCNESS net tow, then followed a CTD cast and our first sub dive since Hurricane Isabel interrupted our at-sea activities. JOHNSON SEA-LINK II (JSL II) dive 3449 plunged below the waves at 1.00 pm (1300 hours). Colonies of Nanomia cara were numerous and aggregated in a 100 ft thick layer from about 650 to 750 ft. Only one colony was seen in the upper 150 ft. These observations contrast with those from the ROV last night when colonies were abundant throughout the upper 100 ft. Such results suggest that colonies migrate upward at night, perhaps to feed, and then return to deep water during the day. Such diurnal migrations were noted a few years ago in Wilkinson Basin when Nanomia cara was abundant there.

By the time evening rolled around, the marine fog had evaporated and the seas were flat. Conditions were ideal for a night dive. On this dive (#3450) we confirmed that a substantial segment of the siphonophore population moved into the upper 100 ft. Unfortunately, the suction pump on the rotary sampler failed to operate properly near the surface and so we were unable to collect any of these colonies. Consequently, we were unable to confirm that these colonies migrated to feed in shallow water. We did sample the deeper-living colonies of Nanomia cara and learned that less than 10% of the stomachs (called gastrozooids) contained prey, and only calanoid copepods.

With only a few days remaining on this cruise and the weather on our side, we decided to steam to deep-water canyon sites in order to compare our studies of Nanomia cara from Georges Basin to a population of Nanomia cara living at 2000 ft. The canyons along the southern margin of Georges Bank, especially Oceanographer and Lydonia, harbor an abundance of colonies (see The Maine Event 2002) and a high diversity of other gelatinous zooplankton.

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Maine beroe cucumis
Credit: HBOI/At-Sea.org

Yesterday, graduate student Brian Ortman wrote about the Feature Creature Beroe cucumis. On this cruise Brian is collecting samples of gelatinous zooplankton for analysis of their genetic structure. In particular, he is concentrating on three midwater species – Nanomia cara, Bolinopsis infundibulum and, you guessed it, Beroe cucumis. He intends to compare the genetic make-up of the common species from site to site. Genetic information is basic to our understanding of how deep-sea communities are structured and how creatures interact in this little known, but supposedly homogeneous, habitat.

Aino Hosia, another a graduate student, originally from Finland, is working on a doctoral degree at the University of Bergen in Norway. Her graduate studies will produce an ecological census of gelatinous zooplankton in Norwegian fjords. While aboard the R/V Seward Johnson Aino has been assisting Marsh Youngbluth with measurements of oxygen consumption using a novel optical approach. In her spare time, she also helps with the launch and recovery of diel MOCNESS tows to collect zooplankton, filters water from CTD casts for fatty acid analyses, picks out gastrozooids of Nanomia cara for predation studies, and photographs everything.

New technology has always offered scientists alternate ways to conduct old tasks more efficiently or to pursue new avenues of research. On this cruise, preliminary trials with a PC-controlled fiber optic oxygen meter have been successful. This technology has allowed Aino to measure basal metabolic rates of the same three gelatinous zooplankton species, specifically Nanomia cara, Bolinopsis infundibulum, and Beroe cucumis. Oxygen concentrations determined from separate analyses (the traditional Winkler titration method) of water samples taken at the beginning and end of a given experiment have been consistent with values recorded by a new micro optode system. The sensors are stable and respiration rates can be monitored continuously for several hours. The images added to this dispatch show the components that accommodate two sensors. One end of an optical fiber cable attaches to a detritus sampler held in a temperature-controlled laboratory. Pulsed light passes through the cable and strikes a small (0.25 in by 0.25 in) piece of sensor foil glued to the inside of the sampler. Light emanating from the foil passes back through the cable to the opposite end, which mates to the Fibox 3 meter. From here data passes through a transmission cable that winds its way from the cold room to the dry lab in order to connect the meters to a computer. Data are logged at 1-second intervals. Results from a typical 16-h experiment with Nanomia cara are plotted, control (pink) and animal (blue).

MISSION DISPATCH 11 Monday September 22, 2003
Location: Lydonia Canyon (40° 18.7’N and 67° 38.8’W)

Dispatch by Brian Cousin – Harbor Branch Oceanoraphic Institution

We are transiting from Georges Basin to the deep-water (ca. 3000 feet, 985 meters) canyons that indent the southern boundary of Georges Bank. The trip around the bank and its shoals takes about 15 hours. The site for our first JOHNSON SEA-LINK II (JSL II) dive this evening is Lydonia Canyon, at approximately 40° 18.7’N and 67° 38.8’W. The sky is blue (a welcome sight after the thick fog of the previous two days) and seas are calm for the time being. Norwegian Research Scientist Dr. Per Flood is in the wet lab, focused intently on the screen of his laptop computer as he edits a digital photograph of the deep-water ctenophore Beroe cucumis. With a critical eye, he removes minor imperfections, sharpens slightly, adjusts contrast, corrects color. Per is compiling a photographic atlas of marine plankton, a vast multitude of drifting organisms that inhabit all the oceans. "The idea is to assemble a collection of photographs of the more common planktonic organisms so people can identify what they find in the sea," Per explains. Per has been producing professional quality images since about 1990. On this trip he has added a digital camera to his arsenal of photographic equipment that interfaces with a dissecting microscope. Atop a more powerful compound scope, he maintains a 35-mm film camera. By combining aspects of images from each magnifying instrument, Per is creating photographic composites that reveal the remarkable morphological details of various creatures. The photograph of each organism is accompanied by a description of where the organism was collected and what is known about its natural behavior. And that’s what makes Per’s work so different. "Photography is an objective, physical process, in contrast to drawing, which is in principle a subjective process – a product of the mind. The eye observes the subject, it is processed in the brain, and the hand is made to interpret the result on paper."

Per also notes while drawings may include the most prominent morphological features, they often omit minor ones, or that illustrators may use a degree of creative license to complete a drawing. Either approach can be the cause of confusion and mis-identification of species by researchers relying on these hand-drawn illustrations. "Also, many drawings are made from fixed (preserved) specimens. An illustrator may never have seen the living organism and therefore cannot show the color, shape, or behavioral characteristics," Per says.

As the depth and breadth of marine science grows, accurate representations of the plankton world become even more important, so that scientists, other than qualified taxonomists, can easily identify a range of common species.

Per says he has about 300 species of phytoplankton and zooplankton so far, including Nanomia cara, Bolinopsis infundibulum and Beroe cucumis from the Maine Event. "This is a long-term project," he says. But Per has made all of his images by traveling "in-situ" – where the organisms live. That has taken him to the Mediterranean Sea along the south coast of France, the northwest and southwest Pacific in Washington and California, the Gulf Stream adjacent to Florida and the Gulf of Maine region where he is hard at work today. It’s clear Per Flood enjoys his work very much, as well as the prospect of making a compendium available to the scientific community and the general public. "I am not satisfied with just a picture, it must also be aesthetically pleasing, approaching – maybe art is too ambitious a word – but the photos must be appealing. Part of my intention is to introduce people to the natural beauty of marine life." Earlier this year, about 100 of Per’s photographs were exhibited in Gijon, Spain at a major international conference on marine zooplankton.

"My favorite marine animals are undoubtedly the larvaceans or Appendicularians. These are small and transparent organisms belonging to the same group as salps and sea-squirts and located at the transition between invertebrates and vertebrates in the animal kingdom. I often nick-name them "vacuum-cleaners of the sea" since they feed by sucking water through a complex set of filters to extract all small particles, including bacteria, single-celled algae and decaying organic matter. These particles provide the food for their growth. I discovered these extremely fine-meshed filters more than 30 years ago and feel in many ways I have been trapped in them ever since. On this cruise I hope to study several of the poorly known, deep-water species of larvaceans. When we reach the 3000 ft. maximum depth of the submersible that we are using in the canyons south of Georges Bank, we are likely to encounter species that nobody has ever seen!

Today we know that shallow water larvaceans, due to their unique external filter-house may grow 10 times faster than many other plankton organisms and also that they serve as prey for several commercially important species of fishes. These facts indicate that larvaceans constitute a crucial link in an ultrashort food chain from the microbial level to exploitable marine resources: There are certain flatfish larvae that will starve to death if they cannot find larvaceans to eat. Recently, we also learned that mackerel to a large extent depend on larvaceans as food. I am convinced that improved knowledge of larvacean biodiversity and ecology in the future will help us understand the annual variations in fish stock recruitment far better than we do today."

MISSION DISPATCH 12 Tuesday, September 23, 2003
Location: Oceanographer Canyon (40° 17’N, 68° 07’W)

Dispatch by Harry Breidahl – Marine Education Society of Australasia [MESA]

Yesterday we dove in Lydonia Canyon, today we have explored Oceanographer Canyon to a depth of 985 meters (close to 3000 feet). The feeling out here is that we are into the seriously deep blue ocean but, in truth, we are only on the edge. The canyons in which we are working only mark the boundary of the relatively shallow continental shelf. If we were to travel a little further east there would be as much as 3000 meters (approaching 10,000 feet) of water below us. Even more staggering is the fact that the average depth of the abyssal plains that make up most of the ocean’s floor is around 4000 meters (over 13,000 feet).

Last night’s sub dive at Lydonia Canyon was JOHNSON SEA-LINK II (JSL II) dive number 3451. Although there were plenty of Nanomia cara colonies, the dive was marred by equipment problems. Both the upper and lower critter gitter racks broke down part way through the dive and one of JSL’s nine electric motors conked-out. As soon as the sub landed on the aft deck around midnight the sub crew began stripping off the broken bits and pieces, adding spare parts, and replacing the dodgy thruster motor. By morning JSL II was ready to dive.

All JSL launches are witnessed by several deck-bound onlookers but dive 3452 drew a larger than usual crowd because Aino Hosia was making her first dive in the forward acrylic sphere. For those of us who still play at being contortionists to see out of the small viewing ports in the aft chamber, the thought of a seat and an uninterrupted view of the ocean’s interior is like heaven. According to Aino "one of the best parts of the dive was watching the bioluminescence when the sub was ascending, it was awesome."

Once the submersible was placed in its cradle on the aft deck, live colonies collected in the detritus samplers were quickly moved to the cold room to continue measurements of their oxygen consumption rates. Preserved siphonophores were taken to the dry lab to look for prey in their gastrozooids (stomachs). Other live fauna like medusae and siphonophores were placed in aquaria and photographed.

Despite some recurrent problems with a sampler on the sub, we plan to continue exploring Oceanographer Canyon with JSL II, MOCNESS net tows and CTD casts. The wind speed has been increasing steadily this afternoon as a cold front moves closer. Wave height is building and so it’s likely that the night dive will be cancelled.

Today’s Feature Creatures – Siphonophores by Francesc Pages
Since the first time I saw a siphonophore in a plankton sample (it was Chelophyes appediculata, a species common in temperate waters), I was captivated by the unique architecture of their transparent nectophores (swimming bells) and the variable inner canal system. Like other planktonic cnidarians, siphonophores combine a very fragile, gelatinous main body with a network of stinging cells, the cnidocysts or nematocysts. These stinging cells are used to catch and paralyze their prey – ( view animated Nanomia cara feeding sequence).

Siphonophores have a complex morphology with specific types of nectophores (swimming bells) forming the nectosome and with several kinds of polyps along the siphosome (stem). Whenever I see a siphonophore I want to know what species it is and how it is built. But what makes siphonophores unique to my eyes is the spreading of their tentacles and tentilla (cnidocyst batteries, the stinging sectors) to catch prey in the water column. Dozens or hundreds of highly contractile tentacles may stretch several meters in length to form a dense, curtain-shaped trap in the water column. These are such delicate creatures that their natural beauty can only really be appreciated from a submersible, such as the JSL II. An in situ view of a long-stemed siphonophore displaying highly synchronized movements of thousands of small pieces is most impressive. Apart from the target species for our current project, the physonect Nanomia cara, my favorite siphonophore on this cruise is a 20 cm (8 inch) long physonect. At a depth of 675 meters (2216 feet).we collected an unknown colony of Apolemia , a poorly known genus that comprises at least 12 more undescribed species.

MISSION DISPATCH 13 Wednesday, September 24, 2003
Location: Oceanographer Canyon (40° 17′ N, 68° 07′ W)

Dispatch by Harry Breidahl – Marine Education Society of Australasia [MESA]

As predicted, a cold front passed through the dive site area last night. Strong winds and choppy seas ruled out the sub dive and MOCNESS net tow planned for last night (Tuesday night). This cancellation was quite a letdown because everyone on board is so focused on work that we really didn’t know what to do with an evening off.

Sadly this morning was a washout as well. Large and lumpy waves seemed to be coming at us from all directions. One of the deck hands was heard to say "someone really turned on the blender". Some of the science crew took the chance to snooze, others went on with documentation of recent finds. Per Flood continued to update photographic records of gelatinous fauna collected on this and previous Maine Event cruises. Francesc Pages reviewed taxonomic descriptions of similar material. Aino Hosia, Chuck Jacoby and Marsh Youngbluth used statistical procedures to analyze micro optode derived rates of oxygen consumption by siphonophores and ctenophores (comb jellies).

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Maine marrus
Credit: HBOI/At-Sea.org

I talked to Second Mate LaVern Taylor about her role at the helm of the R/V Seward Johnson. I learned the ships crew consists of 11 people – 3 on the bridge, 3 engineers, 3 deck hands and 2 galley staff. Watches are set out so that crew members work 4 hour shifts separated by 8 hour off periods. Galley staff adjust their shifts to accommodate the meal periods aboard ship. In addition to the regular crew, Keith Martin and Laurie Roy represent the University of Miami technical support team. They are responsible for the MOCNESS and CTD deployments, chemical measurements of salinity and oxygen, and also keep everyone connected with the world beyond the ship via satellite e-mail links. Yesterday was Laurie’s birthday, our second birthday celebration for this cruise.

Weather conditions gradually improved that afternoon. At 2.00 pm (1400 hours) the announcement of a pre-dive briefing put the spring back into our steps. The Maine Event-2003 was on track again. During this dive Chuck Jacoby occupied the scientist seat next to sub pilot Tim Askew Jr. while, as part of a birthday celebration, Laurie Roy rode in the aft observation compartment accompanied by sub tech Jim Pierce. JOHNSON SEA-LINK II (JSL) dive number 3453 landed on the aft deck by 5.30 pm (1730 hours) carrying a cargo of siphonophores and a dark red deep-sea squid. Most of the Nanomia cara colonies were preserved in situ. These specimens were taken straight to the dry lab for the well-rehearsed routine of gastrozooid (stomach) content analysis.

One unusual physonect siphonophore was collected. Unfortunately only part of this colony could be captured because the bright lights of the submersible caused the ultra-sensitive siphonophore to self-destruct, shedding nectophores and autotomizing half of its stem. Fortunately, the portions that were obtained were sufficient to indicate that the colony is most likely a new species, according to Francesc Pages. His initial assessment is that this bright red siphonophore belongs to the genus Marrus. A detailed description required for the establishment of a new species is underway.

The deep-sea squid, also unknown (at this stage), captured on this dive provide an opportunity to test the micro optode system in another way. Oxygen consumption rates by this very active midwater organism were compared to those measured for the less active gelatinous creatures, such as siphonophores and ctenophores. As expected, the squid consumed oxygen at a much faster rate, i.e., about 5 times more in a third of the incubation time.

Calm weather prevails now, and the sea will be relatively flat for the next 48 hours. Three more sub dives remain on the schedule. After that we must leave Oceanographer Canyon and return to port at Woods Hole.

MISSION DISPATCH 14 Thursday, September 25, 2003
Location: Oceanographer Canyon (40° 13′ N, 68° 12′ W)

Dispatch by Harry Breidahl – Marine Education Society of Australasia [MESA]

Working at sea has its rewards and last night was one of those times that really etch themselves in one’s memory. Firstly, there was the brilliant sunset, a riot of incredible orange and pink hues for which I have no words and that photography simply won’t do justice to. Following the brief time taken to enjoy this evening spectacle, we returned to the business of marine science and what would turn out to be an unforgettable sub dive.

It was JOHNSON SEA-LINK II (JSL) dive 3454 with Marsh Youngbluth alongside sub pilot Tim Askew Jr. in the front chamber. Occupying the aft chamber were HBOI video specialist, Brian Cousin, and sub tech Jim Pierce. Using a submersible to explore oceanic midwaters can never be described as dull or routine. There is always an air of expectation that something really spectacular exists in the darkness. That’s why most of us on board are on the aft deck to welcome the return of the JSL. We are eager to learn what kinds of animals were seen and collected.

And spectacular is what we got from dive 3454. Approaching the sea floor of Oceanographer Canyon, at close to 900 meters (3000 feet), Marsh and Tim were greeted by a slow-moving 4.5 meter (15 foot) deep-sea shark (a Greenland shark – Somniosus microcephalus – much deeper than and very far south of it’s normal range). Marsh recorded this amazing encounter on video and at around 12.30 am (0030 hours) the dry lab was packed with scientists, sub techs and ships crew for the premier showing of "JSL II meets Jaws" (albeit a relatively gentle kind of Jaws).

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Greenland Shark
Credit: HBOI/At-Sea.org

The tape was shown over and over again as we witnessed the large shark suddenly, but gracefully, appear from the epibenthic darkness surrounding the submersible. The mottled gray giant swam purposefully into the sub’s lights and gently crashed into the acrylic sphere just in front of Tim’s face. The audio commentary on this section of the tape will probably not get a ‘for general viewing’ rating but, thankfully, neither the shark nor the sub were damaged. Once the behemoth realized this large, yellow-trimmed thing (the sub) wasn’t edible, she turned and slowly swam away with JSL II trailing close behind. After a short pursuit, it was back to the collection of siphonophores and other deep-sea creatures small enough to fit inside the sub’s sample buckets.

In addition to the collection of Nanomia cara, one of the detritus sample buckets contained a second specimen (about 30 cm in length) of the cirrate octopus Stauroteuthis syrtensis. A cousin of this red/orange octopus had been collected near the same depth (725 m) in Oceanographer Canyon earlier in this research cruise. At that time our attempts to photograph the octopus were not successful. On this go around we had the plankton kreisel set up in the main temperature-controlled lab, ready for just such a find. The chilling 60 C aboard ship matched the temperature where the animal lived. I watched in awe as this alien cephalopod swam and drifted around in the kreisel. At times it jetted forward with a spiraling, cork-screw motion. The octopus could also flare the webbing between it’s eight arms to take on the appearance of a living parachute. In this pose the octopus provided a clear view of the small pseudo-suckers along its arms. These organs have evolved to bioluminesce. Why this morphological change happened is unknown. Some people speculate that the eerie blue-green glow emanating from the tentacles serves to attract prey. We confirmed that this pelagic octopus feeds on small (3 mm sized) copepods (the diapause phase of copepod Calanus finmarchicus), and apparently sucks them past the beaks around its mouth. Three dozen individuals, in perfect condition, were found in the stomach.

The oceanic midwaters that stretch from 200 meters (650 feet) to 1000 meters (almost 3300 feet) below the waves are vast and almost completely unexplored. How many more treasures, such as skulking sharks and wily octopus, remain to be discovered?

MISSION DISPATCH 15 Friday, September 26, 2003
Location: Oceanographer Canyon (40° 18′ N, 68° 07′ W)

Dispatch by Harry Breidahl – Marine Education Society of Australasia [MESA]

As I start to write, JOHNSON SEA-LINK II (JSL II) dive number 3457 is around 800 meters (2600 feet) below us on the last dive for The Maine Event – Fall 2003. It seems like only yesterday that we were preparing for dive number 3436, the first for this research cruise. However, that was nearly three weeks, many dives and one hurricane ago. Now it is time to pack away lab equipment and all manner of other paraphernalia that we brought with us or accumulated on the voyage. Digital images have been organized, collections of zooplankton are cataloged, and all data are backed-up on CD disks, flash memory sticks or external hard drives.

As soon as the sub is retrieved, the R/V Seward Johnson will commence a 15- hour transit to Woods Hole, Massachusetts. Tomorrow morning we will dock briefly and offload some gear. The majority of the scientific party will leave the ship and drive or fly home to New Hampshire, Rhode Island, Florida, Spain, Norway and in my case, all the way across the Pacific Ocean to Australia. The R/V Seward Johnson will head south for a 4-day passage to its home base in Fort Pierce, Florida.

Eleven pm (2300) now and we are steaming at 11 knots through glassy seas. The night sky is cloudless and star-studded. Some members of the scientific group are busy packing microscopes, computers and samples. Moments ago a few of us went to the bow of R/V Seward Johnson to watch a stunning display of marine bioluminescence. Francesc Pages thought that the organisms responsible for the light show in the bow wake were salps, probably the very same salps Thalia democratica that clogged our seawater intakes earlier in the cruise and upon which sunfish (Mola mola) were seen to feed. I was delighted to hear Francesc refer to the blue-green flashes as the "language of the sea". If that is the case, the surface of the ocean was certainly very noisy tonight.

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Expedition Team
Credit: HBOI/At-Sea.org

One final treat was shared. As if on cue, four or five bioluminescent streaks headed, torpedo-like, at the bow. It took a couple seconds for us to realize that these plumes marked the movements of a small pod of dolphins. We had seen dolphins riding the bow wave earlier on the cruise but not when the R/V Seward Johnson was traveling at full speed and not at night. The combination of frolicking mammals and bioluminescence was awesome, a showy end to a highly successful and memorable research cruise.

As I am sure is the case with the rest of the people on board, my thoughts are now of home, back to the ‘real’ world. Or perhaps we are leaving the real world behind, a world of gelatinous life drifting about in constant darkness, cold temperature and intense pressure. I take with me many fond memories and a collection of ‘deep-sea shrunken’ styrofoam cups to return to children in Australian schools.