Daily updates from the RV Cape Hatteras, Gulf of Mexico deep coral cruise
We set sail from Gulfport Mississippi in the early evening after spending all day loading and stowing gear while the ROV team (University of Connecticut) assembled a mobile operations lab on the back deck. Our research vessel, the RV Cape Hatteras is 40m long, but every inch of deck and lab space is packed full with science gear. We have many objectives to fulfill in the next two weeks and the days will be long and busy.
There is a gentle breeze off the Gulf of Mexico as we head out of the docks at dusk. If the weather holds, with a little luck we should have a productive research cruise.
The ROV crew was up early constructing the complicated array of video monitors and communications systems that feed the images from the seafloor through to the pilots and observers in the ROV van.
The ROV, named the ‘Kraken’ after the mythical sea monster, was being equipped with a variety of sampling devices and instruments to gather samples and environmental data from the deep coral sites.
Our first site is called Viosca Knoll 826, which is a large feature with several areas of well developed thickets and bushes of Lophelia coral along the slopes and top. The Viosca Knoll site is located less than 100 km upslope from the Deepwater Horizon well-head and was the area of greatest concern after the explosion.
A recent research expedition visited these coral areas and they did not report any injury, but sometimes damage is not immediately apparent. Our research will follow up initial observations to look for evidence of any damage to the coral ecosystems.
The first ROV dive was a learning experience; flying the ROV along the seafloor takes a delicate balance of movement between the ship, the ROV depressor weight and the Kraken itself. With the wind blowing from one direction and the current pushing us in another – coordination took a little practice and we spent a lot of the first dive working on vehicle positioning.
Despite these challenges, we collected some nice branches of Lophelia for assessment of reproduction and genetics, and some coral associates like small crabs, shrimp and sea urchins for research into food webs. This is the time of year when Lophelia reproduce so we are keeping some alive in chilled aquaria to see if they will spawn so we can study their larvae and learn more about how this coral colonizes new habitat.
Today the dive went a lot more smoothly and we worked on the top of the knoll in a dense patch of Lophelia. It is a gorgeous site and does not appear to have suffered any direct damage. The coral polyps are open and the expected suite of associated animals were observed in abundance, which is an encouraging indication that the oil did not impact these coral ecosystems. A closer look at the animals we collect will tell us whether there are any sub-lethal effects; these are impacts that do not cause death, but may impact the growth, reproduction or overall condition of an animal.
Although the ROV is our primary collecting tool, it is not very useful for catching fish! We are using a variety of nets and traps to sample the fish communities on the seafloor and in the water column. This evening we pulled up a fish trap which we deployed on the first evening on station, but despite a really stinky bait of menhaden the fish remained elusive.
We did however catch a giant deep sea Isopod and a golden crab. The former looks like a huge pill-bug with Darth Vader eyes, but the golden crab is a fishery species in the Gulf of Mexico and is often found in or near the coral habitat. Unfortunately the large specimen we caught was not destined for the dinner table!
This is our third dive day and we are staying on our original site since it is the area of most extensive coral (as far as we know) in the northern Gulf of Mexico, and is also the closest to the oil well.
The ROV and ships crews are working well together and have coordinated the ‘dance’ between the RV Cape Hatteras and the Kraken. The weather is a little breezy, but it is still hot and sunny – a good day to dive.
One of our objectives out here is to take water samples, both in the water column and near the corals for chemical analysis. One of the side effects of increasing atmospheric CO2 is a reduction of pH in the water. This happens because when CO2 dissolves in water, it creates carbonic acid, and as the ocean absorbs more anthropogenic CO2, the water becomes increasingly caustic.
Unfortunately those animals with carbonate skeletons, such as corals, may begin to dissolve or be forced to channel energy into maintaining their skeleton instead of growing or reproducing normally. Intuitively it seems that animals at depths of over 400m would be safe from changing surface conditions, but because of complex oceanography, this is not the case.
To take water samples near the corals, we attached a ‘Niskin’ water bottle to the ROV. The water column is also sampled using a Niskin array (20 bottles), which provides real-time continuous data as it travels through the water column, and allows us to close the bottles at the depths we want.
We have some indication that the Gulf may have a naturally fairly low pH, so this is a good opportunity to study the effects of ocean acidification on corals, using a natural system that is already dealing with ‘future’ water chemistry conditions.
Yesterday evening we moved to another site a little further west and a little shallower (350-400 m); this area is more rocky and has less Lophelia coral than the main Viosca Knoll, but has high diversity of animals that like hard rocky habitat.
We started as usual by launching away from our target feature on sandy substrate and headed off upslope. Small patches of cobble or rubble are the first indications that we are nearing a coral area. Even these small chunks of hard substrate are covered with anemones, tiny ‘lollipop’ glass sponges and the occasional small soft coral, and any structure in the deep ocean seems to have a fish or crab sheltering beside it.
Moving upslope, we see larger patches of rock with black corals, bamboo corals and the ever present anemones. The Lophelia colonies were near the top of the feature and do not form large mounds here, but are moderate sized and they look very healthy with open polyps and very little dead skeleton.
This is a very pretty site, with a large area of low relief hard substrate covered in patches of coral and sponges, but the elevated section with Lophelia is quite small. There are also many large fish here, and several observations of fishing line indicate that other people know that too.
Today is Saturday, but unlike shore based work weeks, there are no days off at sea. The ship and ROV time are so precious that we cannot waste them with R and R!
Days at sea are generally very long; the day shift starts at 7am and we are usually still working at 10.30pm. We also have a night shift that conducts non-diving operations such as mid-water trawling for animals that live in the pelagic zone, fish traps, water column profiles for water quality data (temperature, salinity, oxygen, turbidity) and plankton sampling. This kind of data gives us a comprehensive ecosystem view to put the seafloor communities into perspective, allows us to describe the pelagic community structure and collect samples for food web analysis.
Today’s collecting went well and I have more good healthy corals to keep alive for laboratory studies on Lophelia reproductive biology and physiology.
Today we woke to torrential rain; it was so heavy that we could not see beyond a few meters around the ship. It feels cozy standing under the shelter of the upper deck in the early morning with a cup of coffee watching the steel grey ocean and feeling completely isolated from the rest of the world.
The ROV crew are not so happy as they prepare the Kraken for launch in hot heavy rain gear.
Today we are exploring a site we have never visited. From the multibeam map, it looks like a feature that should have coral, and today we will find out.
Multibeam mapping involves shooting sound waves through the water and analyzing the return signal to create a three-dimensional image of the seafloor. We have multibeam maps for our main target areas, and it opens up a whole new perspective for exploration, and understanding the shape and location of coral habitat.
Without this technology we relied on the ship’s fathometer and navigation charts to tell us where there might be ‘bumps’ to investigate, which is a very ‘hit and miss’ way of trying to find these small features on a vast seafloor.
This dive paid off – one more coral feature documented! We found a small but gorgeous area of coral habitat, with Lophelia, black corals, bamboo corals and sponges as well as a very diverse community of mobile invertebrates such as crabs, sea urchins, sea stars and fish. The conger eels were especially numerous, peeping from the safety of their burrows near the corals while we slurped up and grabbed their neighbors in the name of science.
Today was a long transit day to our next study area, 22 hours away on the West Florida Slope, so now we get some down time to wash stinky salty clothes, nurse the variety of bumps and bruises that inevitably happen when you carry heavy objects around a rocking ship, catch up on data entry…and sleep.
The transit was smooth and sunny, but the weather news tells us a tropical storm is brewing in the Caribbean, and it may head our way. This time of year in the Gulf it is not unusual for tropical systems to pass through, and all we can do is hope it goes and bothers someone else.
The live corals are doing well but they are hard work to maintain. These corals need good clean cold water so we have a chiller system set up for their maintenance. We collect their water using an array of water bottles to avoid any contamination or freshwater layers that may be floating on the surface of the water.
Previous cruises have provided samples to study the reproductive cycles of Lophelia
and other corals in the Gulf of Mexico, and we now know that this is the time of year that Lophelia
releases eggs and sperm into the water to create tiny planktonic larvae. One of our objectives out here is to study the development, lifespan and behavior of the coral larvae so we can have some idea of where they go and how quickly they may colonize new or damaged areas. We are collecting small fragments and holding them to see of they will oblige and spawn.
Unfortunately there is not much we can do to force them, so it’s a waiting game.
Today was our first dive at a new site and it is spectacular, lots of live coral, good diversity of sessile animals such as corals and sponges, and lots of mobile invertebrates (crabs, starfish, sea urchins) and fish.
It’s always exciting going to a new area, but it is doubly so when it turns out to be a lovely new reef.
One of our projects involves studying the population genetics of Lophelia coral, and for this small fragments are needed from many different places. This work links well with the larval study since it will tell us where the corals came from and whether the reef is made up of a few or many individuals.
Understanding the population dynamics tells us which areas are critical sources of new colonies, and whether these Gulf populations are connected to those in the Atlantic. So far we have lots of samples from the northern Gulf of Mexico and the east coast from North Carolina to Florida, but the gap is right here on the west Florida slope so these samples are very important as they provide the linkage between the Gulf and Atlantic.
Tomorrow we will carry on exploring this area, which looks extensive from the multibeam maps.
After the ROV dive the seas started picking up so we worked late into the night securing everything that had become scattered around the lab and deck during our period of calm seas.
Everything looks nice and tidy again as the night watch comes on and the day watch goes below, but that won’t last long with so many people doing work on a small ship.
The dive today was a little deeper than yesterday in an area that nobody has visited before. Exploration is always a gamble; if we find new coral areas, we can make significant contributions to deep coral ecology. If not, well all information is useful, but since ship and ROVs time is so expensive we would prefer not to spend it on mud flats.
This location was a success – we found a very diverse coral community with several different species of stony corals, sponges, gorgonians, hydrocorals and some large white soft corals that have not been documented in the eastern Gulf of Mexico.
There are plenty of live colonies as well as lots of standing dead coral and It is not unusual to find a higher diversity of sessile filter feeders in dead coral areas. Live Lophelia has large polyps that are equipped with batteries of stinging cells, and there are few larvae that seem to be able to settle on live coral branches. We did not see many mobile animals at this site, which is curious as Lophelia reefs are usually teeming with associated invertebrates. Every time we visit one of these reefs it seems to raise more questions than answers.
Today’s dive was spectacular! We visited a new mound west of our first dive and the first sight we saw when the bottom came into view was a massive carpet of shrimp – thousands of them just hanging around near the edge of the reef. These were some deep sea species that we had seen occasionally on previous dives here, but not at this abundance. It is possible that this is a breeding aggregation and we will know more when we identify them and look at their reproductive status – and even then we will not know for sure.
Since we see these systems so infrequently, we often do not have the data we need to fully understand their ecology, we can only make logical deductions based on the information we have. As we neared the top of the mound we came across large live thickets of Lophelia, mixed with other stony corals that are rarely seen in the northern Gulf of Mexico, or the Atlantic.
This is a unique type of assemblage and unlike yesterday’s site there are lots of small crabs, brittle stars, sea urchins and other mobile animals. At one point we were completely surrounded by a school of squid that blocked the camera view and followed is for several minutes. This was truly a lovely reef and today was a great dive despite rather choppy seas.
Today we dove on a site close to where deep corals were first seen on the west Florida Slope by John Reed of Harbor Branch Oceanographic Institution. The habitat he documented was different from those we have seen during this trip, but he was a little closer to shore and the seafloor was more exposed rock than coral bioherms.
We have noticed that the amount of live coral and the types of animals we see can vary quite a lot between sites. We do not fully understand why we see these differences; depth seems to be one of the primary drivers, along with the type and shape of the substrate, but there are probably other more subtle factors such as food supply, current regime or water conditions that make the environment more favorable to some animals more than others.
One of our study objectives involves analyzing our video footage from different areas and correlating the community structure with habitat type and environmental conditions to see if we can tease out why these differences occur and how we might use this information to predict where we might find more coral ecosystems.
Since we cannot hope to explore the entire seafloor, our ability to predict where corals are found is an important tool for agencies tasked with protecting these ecosystems.
This was our last dive day and we were several miles north of our previous dive site on another new ‘bump’ on the multibeam map. This one was quite large and we were optimistic that it would be as spectacular as our previous explorations.
We were not disappointed – although the dive was shorter than usual (only 5 hours), we covered enough territory to know that this was a well-developed deep coral ecosystem similar to the others we had visited, with the usual abundant reef-associated animals. The ROV van was peaceful and quiet as the pilots flew the Kraken over the reef and the two science crew took notes and pictures.
The rest of the ship however, was a frenzy of activity as equipment was stowed for the transit to shore, and the working chaos of the lab was forced to order and re-packed. As soon as the ROV was on the deck, the Captain headed east to St Petersburg, Florida. It was mid-afternoon and we were scheduled to arrive the next morning around breakfast.
It has been a great cruise with no apparent damage to the corals, a lot of new sites explored and enough samples to keep everyone busy for months. As much as I love being at sea though, it’s always nice to come home.