Year 3: April 2013 – May 2013
From Cape Hatteras to Canada, the continental slope is riddled with deep canyons that link the continental shelf to the deep sea, serving as pathways for nutrients, sediments and pollutants,. Little is known about life in the canyons’ unique habitats.
An interdisciplinary team of researchers will study the canyons, particularly Baltimore and Norfolk, over a four year period from 2010 – 2014. The results of this work will help guide the future uses of these ocean resources, which may include oil exploration, alternative energy development and intensive fisheries. The work will also assist in protecting vulnerable canyon habitats, through development of protected areas such as National Marine Sanctuaries.
During the first cruise, scientists used multibeam sonar to create detailed maps of nearly 1,400 sq. km of the canyons and surrounding areas. The multibeam maps helped researchers identify potential sites for exploration, and the project marine archaeologist identified nine new shipwreck sites. These maps will continue to be used to guide the sampling activities of the 2013 research cruise.
During fall of 2012 the science team used the Kraken II ROV to conduct video transects, collect samples of invertebrates, fishes sediment and water, and record environmental data. The ROV was also used to explore the shipwreck targets discovered by the multibeam sonar. As expected these were the remains of the WW-I era ‘Billy Mitchell Fleet’ that were sunk off the coast of Virginia. A variety of other non-ROV sampling activities were performed, including bottom trawling and box-coring to obtain information on soft sediment habitats in the canyons and collection of water column data using a CTD instrument. The scientists also deployed four benthic landers and two moorings to collect long-term information on temperature, salinity, oxygen, turbidity, current speed and direction, and sediment deposition over a one year period. During May of 2013 the team will continue their work natural ecosystems and historic shipwrecks in the middle Atlantic canyons.
This study is being funded under contract to CSA Ocean Sciences, Inc. and its academic partners from the Bureau of Ocean Energy Management (BOEM). The NOAA Office of Ocean Exploration and Research and the US Geological Survey are also collaborators on this four year effort.
As of 5/18/13
19 Science team members
12 ROV dives
492 two hour DVDs of dive footage recorded
10 ROV crew
367 genetics samples
335 gallons of seawater collected
1660 isotope samples
1009.5 nautical miles covered
30 ship’s crew
12 plastic site markers made
100 pounds of bacon eaten
32 box cores
43000 gallons of fuel burned
34 Push cores
2,250 eggs consumed
20 Mono cores
1068 pounds of mud collected
2 landers recovered and redeployed
60,000 gallons of freshwater made and used
1 music video
1941 specimen photos
20 degree difference in air temperature between the lab and the ROV control van
294 octocoral samples collected
50+ live animals collected and maintained
2 shrunken wig heads
Cheryl Morrison, PhD and Katharine Coykendall, PhD
Bathymodiolin mussels, all in the genus Bathymodiolus, evolved in environments very different than the ones we land-dwelling organisms, that get our energy indirectly from the sun through plants, did. Bathymodiolus species live in areas of the sea floor where fluids of chemicals, such as methane and sulfide gasses, are escaping through the sea floor. Not only can these mussels tolerate the chemicals that would be toxic to most marine organisms, they thrive here! They can filter feed, like many sedentary marine organisms (including intertidal mussels) but they also have unique microbes that live in their gills as symbionts. The symbiotic microbes can convert methane and/or sulfide to energy (chemosynthesis), and pass it along to their mussel hosts. It is such an efficient relationship that the mussels get most of their nutrition from the microbes, and have a reduced digestive tract.
Animals that have chemosynthetic bacterial symbionts acquire them in one of two ways: vertically or horizontally. Vertical transmission means that adult host animals pass their symbionts to their offspring. Like a favorite piece of jewelry handed down through generations, the symbiont is transferred to the young mussel. Some species of deep sea clams acquire their symbionts this way. Horizontal transmission means that at some point early in their development, host organisms capture symbionts from free-living bacteria in the environment. This would be more akin to going and buying a new piece of jewelry. Studies have shown that Bathymodiolus mussels acquire its symbionts this way.
Scientists can determine which mode of transmission a host uses by looking at the DNA of the host and the DNA of the chemosynthetic bacteria that live inside them. If vertical transmission is the norm, then one would expect that the pattern of evolution of the chemosynthetic bacteria to mirror that of the host’s. The closest relatives of the bacteria would be found in the closest relatives of the hosts. After many generations of being housed within the host, bacteria tend to lose some functional genes as they rely more and more on the host, so they have a reduced genome.
On the other hand, in horizontal transmission, every new generation of host captures a sample of bacteria from the environment. The evolutionary history of the bacteria and the host would not be parallel. Also, because the bacteria have to survive out in the environment and as a symbiont within a host, it has to have a complete, fully functioning genome. Interestingly, some species of Bathymodiolus have just methanotrophic symbionts, while others host both methanotrophs and thiotrophs (sulfide utilizers).
These mussels are often the first species to arrive at a new gas seep site and can cover large areas of the sea floor, as we saw on our dives. Finding a vast mussel bed without other characteristic seep animals like tubeworms may indicate that the seep is relatively young. The mussels may also actively exclude other potential settlers to the seep site by feeding on their larvae.
There are 35 species of Bathymodiolus mussels described to date, and 9 of these occur in the Atlantic, with the majority (7) found at cold seep sites. Similar shell morphology (shape) and soft tissue anatomy means that traditional taxonomy based on appearance has proven difficult as the sole means to distinguish among species.
We can delineate species by sequencing a section of DNA and comparing these sequences among species. From such analyses, two major groupings within the Bathymodiolus genus have been detected: The B. childressi group that includes some Pacific species and tends to be at shallower sites; and the B. boomerang/heckerae group, with both hydrothermal vent and cold seep species and tends to be found at greater depth. B. heckerae is found at Blake Ridge, a cold seep off of the Carolinas, as well as a seep off the west coast of Florida. We found bathymodiolin mussels at cold seeps in both Norfolk and Baltimore Canyons. By sequencing a barcoding gene (COX1) from several mussels from Baltimore Canyon collected last year, we know that the mussels from that seep site are B. childressi, a species that has one type of symbiont that oxidizes methane. We have been discussing which species of mussels we found – childressi, boomerang, or heckerae, or perhaps a combination! Once we get back to the lab, we will sequence this same stretch of DNA from our samples from the deeper seep off of Cape Henry,Virginia and get a molecular identification of this species.
Although the genus Bathymodiolus was described only 27 years ago, many new species of Bathymodiolus mussels are being described from hydrothermal vent and chemosynthetic communities. Our sampling will help build a richer understanding of these unique bivalves.
Although our primary purpose out here is studying what lives in the deepwater canyons, we can’t help noticing the life on the surface of the sea. It is not unusual to spot whale blows in the distance, or to have a call from the bridge “dolphins on the starboard fantail” which draws us all out of the lab.
Birds are common. It is not unusual for us to see gulls circling (and occasionally landing on) the ship. Terns are frequent visitors too. During the Jason recovery a common tern, Sterna hirundo, first settled on the A-frame (that holds the Medea) and then on the LARS (that holds the Jason). This bird breeds from Canada to the Carolinas, as well as southern Scandinavia, and winters in the Caribbean, southern Florida and northern Africa. As its name suggests, it is quite common!
Another frequent sighting is the Wilson’s storm petrel. This small black bird has a distinctive white patch on its rump, and appears to “walk on water” as it dabbles its webbed feet on the surface. It nests in Antarctica but spends the rest of its life at sea. One got trapped in some water on the deck of the ship. After extracting it, and letting it get warm and dry, we released it, and it flew off over the waves.
During the recovery of Jason an osprey, Pandion haliaetus, flew by. This was unusual because ospreys tend to stay within 10 km of their roosting site. We wondered if perhaps the bird we saw was migratory. Ospreys breed on every continent except Antarctica so perhaps this one was returning north after spending the winter in South America. Ospreys are skilled hunters with an outer toe that is reversible, which allows them to carry fish with two toes on each side. Their species name, haliaetus, comes from the Greek “halos” which means sea, and “aetus” which means eagle; a fitting name for a bird with hunting abilities that were so amazing there was a Medieval belief that the osprey mesmerized the fish, making them turn belly up.
We have had several calls for seeing a “fin” in the water. On two occasions it was a Mola mola or ocean sunfish. These unusually shaped fish appear to be “all head” and are as tall as they are long. They have a long dorsal fin on the top and long anal fin on the bottom, and not much of a body. This unusual shape has led to a variety of names. Mola means millstone in Latin, in reference to its round shape. Most European names mean “moonfish” in reference to the shape, however its English name, “sunfish,” comes from its habit of sunbathing at the surface. It propels itself through the water by a sculling motion with its fins. It is the heaviest bony fish known — an average adult can weigh 2,200 pounds. Females produce more eggs (300 million!) than any other known vertebrate. The young fish (called fry) are spiky and resemble miniature pufferfish. They eat jellyfish, squid, salps, and crustaceans found throughout the water column. The Museum has a replica of one on display on the second floor of the Main Building if you want to check one out!
We have also seen other fins in the water, including dolphins. We saw common dolphins playing in the waves and they put on quite a show. We have seen fins that we are certain belong to whales. Early in the cruise we spotted a minke whale. We could see the blow, a fin, and a bit of its back as it dove. During our weekly safety drill we spotted a blow and a fluke in the distance as we stood outside with our lifejackets on. We decided that had to be a humpback. We have spotted other blows in the distance (last night there were 8 distinct blows in a 2 minute span!) but have not been able to see a fin. Two pairs of shark fins were spotted one afternoon, and we could catches glimpses of the fins between the swells. We could not decide what type of shark they were and could not even agree on how big they were! Our length estimates ranged from the conservative of 8 feet to the high end of 20 feet.
The majority of our day is spent indoors, working in the science labs or the ROV Control Van, but when we get outside we look for the wildlife of the surface.
It is always traumatic to deploy very expensive science gear into the marine environment. Like fishermen, the military, or anyone who uses the ocean, sometimes gear is lost. For us, this risk is even more troublesome because in addition to perhaps losing equipment worth many thousands of dollars, we also lose invaluable data and experiments. But, if we do not take these risks, we will learn nothing, and the quest for knowledge that will help us understand and manage our ecosystems is of vital importance.
—Steve W. Ross and Sandra Brooke
This morning we successfully recovered the first UNCW lander deployed last fall. Imagine a triangular bunk bed outfitted with a variety of instruments. There are probes for monitoring water chemistry, such as dissolved oxygen. A wide variety of settling plates of different materials hang on the structure. Some made of of steel, some of limestone, some of sandstone for examining microbial growth. There were other plates made from plastic foam and mesh for determining if texture plays a role in settling. A rotating sediment cup trap, which collects samples for 30 day periods before switching to a new cup, is on it, as well as a current meter called an ADCP (Acoustic Doppler Current Profiler). This data allows us to do some interesting things, such as matching the sediment by month with the current data for that month. That might allow us to say “this flow brings organic matter,” or “this flow has sandy sediment,” etc. We will be able to tell when the current reverses and can characterize water masses in the canyons by looking at things such as speed, direction, temperature and salinity. This long-term data will give us a more complete picture of what is happening over time, which will complement the “snapshot” we get with an ROV dive.
Soon after the lander hit the bottom last year, the ship triangulated its position. This gave us an approximate position of the lander to go by this morning. We hovered over its calculated position and Mike Rhode (UNCW) signaled its acoustic releases to drop the 600 pound weight that anchored the lander to the seafloor. By constantly pinging the lander for its range, he could tell it was rising off the bottom. Based on its rate of ascent, we estimated it would get to the surface at 7:10.
Everyone was scanning the horizon, and right on time, the lander surfaced just off the bow of the R/V Ronald H. Brown. We could see the red flag and yellow floats as well as the trailing float line. Several Common Dolphins were spotted nearby, we suspect attracted to the pinging of the lander. The ship steamed alongside the lander, grappling its recovery line, and used a crane to lift the lander on board. The sea swells this morning made the lander swing as we brought it on deck, which was challenging. However the ship’s crew and science team got it on board safely. After being tied down, the lander was surrounded by scientists taking pictures, examining their experiments, and getting it ready to redeploy later today.
A question from Zach came through the blog recently, asking about the coolest animal we have brought up so far. Pycnogonids, or sea spiders, was the answer, and after learning more about them, an entire post on these extraordinary creatures was due.
These “sea spiders” are found all over the world, from shallow water reefs in the tropics to these deep areas of the canyons. They range in size from about a third of an inch to 35 inches. Although they are arthropods, they aren’t truly spiders, and there is debate where they should be classified. There is some thought that they are an ancient sister group to all living arthropods. Pycnogonid means “thick knees” and they certainly have obvious joints along their legs. When they walk, the resemblance to spiders is unmistakable, however they can also swim by pulsing their legs to propel themselves through the water.
Holding one in your hand it is difficult to tell which side is up. The super skinny body and long proboscis (for feeding) don’t provide many clues. However if you look closely you can find two tiny eyes, which indicate the top of the head. The proboscis is used for feeding. The pycnogonid inserts it into animals such as anemones and sucks nutrients out, much like a mosquito sucks blood from humans. The anemone does not die, just as we do not die from a mosquito bite. The proboscis on the specimens we collected is nearly as long at the entire body!
The anatomy of the pycnogonid is very confusing. Most pycnogonids have 4 pairs of walking legs, as do spiders. However there are some species with 5 or 6 pairs of walking legs. Most of us have seen the diagram showing three body parts for many arthropods – head, thorax and abdomen. In pycnogonids the thorax, where the legs attach, is the main “body” and the abdomen is tiny and almost vestigial. This means there is not much room for organs inside! There are several adaptations to this, for example pycnogonids do not have a respiratory system, rather they “breathe” through diffusion. Their long skinny legs and skinny body provide lots of surface area for this process. Their digestive tract has pockets that stretch down into their legs. They have very high blood pressure, with a heart rate between 90 and 180 beats per minute. Like spiders, they have some additional appendages near their head. One pair is called an “oviger.” The pycnogonid females use this to hand eggs to the males. The males use the ovigers during courtship and to guard the eggs during development. They have pairs of chelifores and palps which are similar to chelicerae and pedipalps found in spiders and are used for feeding and sensing the environment.
Pycnogonids were found in trawling operations during the Challenger Expedition between 1873-1876. I can imagine the confusion these creatures must have caused when they came up in the net. During that voyage they collected more than 4,000 previously unknown species and laid the groundwork for the science of oceanography. And here we are, 130 years later, still asking questions about these bizarre looking creatures.
All of us out here on the R/V Ron Brown want to say “Happy Mother’s Day!”
from the science team, the ship’s crew and the Jason crew