We have safely and successfully returned to land after the end of our 2019 CCE-LTER Process Cruise! On Friday, we sailed back past Point Loma into San Diego Harbor and offloaded our month’s worth of scientific gear and samples. Only time and sample analysis will tell us what we found, but we know we conducted plenty of science! Over the course of 32 days, we did 93 CTD casts (ran out of time for the final 7), 26 MOCNESS tows, 3 SeaSoar deployments, and innumerable Bongo tows and trace metal CTD casts – not to mention Zippy’s solo excursion!
The numbers only capture half the story, though. Going to sea with 57 people on a 280-foot ship inspires you to get to know those around you, and our party bonded across scientific and geographic lines. We look forward to future collaborations around the world! We’ll miss the daily sightings of whales and dolphins, though.
Sara Rivera is a graduate student in the Aluwihare Lab at Scripps Institution of Oceanography. Here, she recounts some of her challenges in sampling at sea.
Being at sea for research requires innovative solutions for problems not typically experienced on land. One of the main issues faced when sampling for microorganisms and organic chemistry is the impact of light on samples. On land, it is easy to grab a piece of foil to cover a rack of vials. At sea, it is not so easy because it is fast, windy, and there are limited supplies. At first, I used foil to cover my tube rack, like I would on land, to block the sunshine. I found that with the fast pace at sea that I needed to get my samples done, I constantly ripped the foil and needed to get a new piece. I would also end up chasing pieces of foil as they were blown across the deck. As my supply of foil dwindled, I contemplated what else would efficiently block the sunshine while allowing easy and efficient access to the sample tubes.
Lo and behold, the answer sat in front of me in an essential piece of cruise equipment: a roll of duct tape. I created a barn-like structure out of duct tape that would slide over the tube rack and completely block out any sunlight. It is waterproof and reusable. It is also removable, allowing me to continue to use the tube rack for other experiments as needed.
Why do I care this much about keeping the samples out of the sunlight? Sunlight impacts both chemical and biological processes. The untraviolet (UV) region of sunlight leads to photo-oxidation of organic molecules, changing the chemistry of the sample before I have time to process it. Recent work by Neal Arakawa (Science Advances, September 2017) demonstrated that a single type of molecule, β-carotene, can photooxidize to generate a slew of carotenoid degradation products that is linked to 4% of the total dissolved organic matter in the ocean. If one molecule can degrade to such a large number of other molecules, from simply sitting in the sunshine, I do not want that happening in my samples! I want the samples to reflect the chemistry of the sea water from the depth from which I collected it.
UV also damages biological cells. The biological damage can impact both the biology and chemistry as distressed cells will take up and release different molecules than in their normal state. Since I measure both the biology and chemistry, this one is doubly bad.
The visible light regions of sunlight are absorbed by the green pigment chlorophyll, found in the organelles called chloroplasts, which is essential to photosynthesis in the majority of marine phytoplankton. These chloroplasts also give the phytoplankton their green color. Light is attenuated as you go deeper in the ocean. We sample at a variety of depths from the surface down to 515 meters (1690 ft). The organisms below the surface are not acclimated or adapted to the light on the deck of the ship- it is much too bright for them. It can also lead to fast growth and production from increased photosynthesis. Because I want to capture the biology at the different depths we sample, I don’t want them to suddenly start growing faster because of the additional light.
When you do zooplankton
tows, you bring a lot of monstrous-looking creatures onboard. Sometimes we get Phronima
hyperiid amphipods, which were the inspiration for the 1979 movie Alien;
occasionally we pull up red tuna crabs, small lobster-like crustaceans with
very sharp claws; and the other day we caught two vampire squids, small purple
creatures with big black eyes, Dumbo ears, and tissues between their tentacles
that resemble vampire cloaks. But one of the craziest monsters we have is the
net we use to capture and sample these organisms: the MOCNESS!
Assuming you haven’t
been living under a rock for the past hundred years, you will probably
recognize MOCNESS as a play on Scotland’s Loch Ness Monster. MOCNESS stands for
Multiple Opening/Closing Net and Environmental Sampling System, and was
developed by Peter Wiebe at Woods Hole Oceanographic Institution. If you can process
that behemoth of a name, you will get clues about what the MOCNESS does. Most
of our plankton nets have simple circular ‘mouths’ that stay open for the whole
net deployment: they go down to depth open and come back up still open, so if
we sample down to 200 meters we are actually collecting animals everywhere
between the surface and 200 meters. That comprehensive sampling is fine for a
lot of the research questions we ask (aka: “Who is present in the upper ocean
off San Diego versus Monterey?”), but sometimes we want more information about
which animals live at specific depths. As its name implies, the MOCNESS has
multiple nets (10 on our current setup!) attached to one frame, and they can be
opened and closed in sequence to sample different depths. If you want to
compare the zooplankton living at 1000 meters versus 100 meters, you can
program separate nets to close at each of those depths. The MOCNESS also has
oceanographic instruments to measure water temperature, salinity, oxygen, and
fluorescence, so we can get information about the physical water profile in
addition to zooplankton specimens.
Most of our MOCNESS tows on this cruise sample down to 450 meters, although occasionally we sample to 1000 meters. Those deep tows can last over three hours, which doesn’t even include the net washdowns afterward! The majority of the sample from each net filters down to a plastic jar attached to the end of the net, but once the nets come back on deck, we hose them down to make sure we collect all the animals that may have gotten stuck in the net mesh. Net washdowns sometimes feel like they go on forever, but they can be very important: one of the vampire squids we caught a couple of days ago was stuck halfway down the net, and we wouldn’t have collected it if we hadn’t done the net washdown.
Net washing time is also essential for taking in the afternoon sun (or sometimes early morning pre-dawn air) out on deck, and for keeping an eye and ear open for passing whales. Today we started our third cycle, and we were graced all day by the presence of several fin whales. Their broad backs and deep exhales were sometimes just 50 feet from our ship. The sound of a fellow mammal emerging from the depths of the ocean to release a breath of air never gets old. Plus, all those whales are a sure sign that there are zooplankton around to feed on!
As the Beatles once said, “It’s been a hard day’s night.” Once a week, the entire science party on our cruise turns into vampires and samples the ocean all night long, from sunset to sunrise. These marathons are known as transects because the ship sails in a straight line across a gradient between different oceanographic features, and we do a sampling “station” (CTD and water samples, trace metal cast, zooplankton net tow) every hour. We start the transect in lower-productivity waters outside of the filament, cut through the high-productivity filament, and then sail back into low-productivity waters on the other side. The goal of our transects is to measure gradients in water properties (temperature, salinity, oxygen), nutrients and trace metals such as iron, and biological communities (phytoplankton, zooplankton, bacteria) across and outside of the filament. By sunrise on Sunday morning, we had sampled 7 stations and had as many samples from one night as we usually have over a four-day cycle!
On transect nights, the entire science party starts their work shift together at sunset and ends in time for breakfast (hopefully). These nights are one of the only times when the whole science party is awake at the same time. They are intense nights, but are made better by teamwork, positive attitudes, and good music. Some people on the ship claim that the bioanalytical laboratory is the place to be on these nights. Although the people working in that lab have to spend hours filtering the water samples they collect on the transect stations, they also keep a wide variety of snacks in a clean part of the lab. Some of their favorites (that they’ve revealed) include apples, peanut butter pretzels, and chocolate cookies. Both the bioanalytical lab and the wet lab (which processes the zooplankton samples and lays claim to the other funnest place on the ship during transects) often have impromptu 4 a.m. sing-alongs and dance parties in between stations.
We conduct the transects entirely at night to avoid changes that can occur in marine plants and animals between day and night. Just like land plants, phytoplankton use chloroplasts filled with chlorophyll to convert sunlight into carbon, and these chloroplasts can get ‘quenched’, or oversaturated, during the day. Measuring phytoplankton at night gives a more accurate indicator of their chlorophyll levels and functionality. Zooplankton also show day/night differences in measurements. One reason is that some zooplankton have surprisingly good eyesight, which allows them to see nets coming in the water and swim away. Nighttime allows us to sneak up on zooplankton, true to our vampiric form. The second reason is that many zooplankton undergo a daily mass migration several hundred meters up and down through the water column (which is quite remarkable considering that many zooplankton are 0.5-2 mm in length!). Scientists believe that this mass migration, called diel vertical migration, is a zooplanktonic attempt to balance feeding opportunities in surface waters against the threat of visually-hunting predators. At night, many zooplankton move up to shallower waters to feed, but when sunrise hits, they move back down to depth to avoid being seen. Sampling the upper 200 meters of the water column during day versus night could therefore give vastly different indications of who is present.
Yesterday we started Cycle 2, which should last several more days. We are back in the core of our upwelled filament, with lots more green, productive waters to sample!
For the first week of our cruise, we were carrying a stowaway science member onboard the Atlantis: Zippy the Zooglider! Zippy is four feet long, orange, and torpedo-shaped, but don’t mistake him for a giant carrot. On Monday, we released Zippy into the ocean to cruise underwater off central California for 20 days while we do our shipboard sampling.
Zippy comes from a class of Spray gliders, which are autonomous underwater vehicles (AUVs) developed by Russ Davis and Jeff Sherman at Scripps Institution of Oceanography. True to their name, AUVs are completely independent, remotely-operated vehicles that can navigate underwater without being tethered to a ship (if you are quick on your nautical literature references, you might recognize the name Spray from the ship that Joshua Slocum single-handedly sailed around the world, as told in his book A Solo Sailing Trip Around the World). The Spray gliders are controlled by engineers on land to ‘fly’ in any underwater pattern we designate. Underwater gliders are gaining popularity for precisely the reason that they can be left out in the ocean for months at a time to record data with no shipboard support. They just need to be launched and recovered! Most Spray gliders are deployed by small dinghys off Scripps, but since we want Zippy to profile the waters that we are sampling on our cruise, we brought him out to deploy at sea.
Similar to the SeaSoar, Spray gliders are equipped with oceanographic sensors to measure water temperature, salinity, oxygen, fluorescence, and biological particles in the ocean. Zippy has an additional characteristic beyond his standard Spray outfit: his “nose” has a shadowgraph plankton camera attached to it, which allows him to image live plankton in their real habitats. This addition was the product of a collaboration between the Instrument Development Group (which runs the Spray program) and Mark Ohman’s lab (also at Scripps), which studies mesozooplankton ecology and behavior. These in situ images give us important insights beyond what our standard shipboard plankton net tows tell us. As with all sampling metrics, plankton nets have advantages and disadvantages. Nets allow us to scoop up an actual sample of ocean plankton in order to visually and genomically identify animals and determine what they feed on, but nets can mangle fragile organisms (long tentacles and watery bodies don’t hold up well against nylon mesh) and they don’t capture animals in their natural habitats. The Zooglider’s camera gives us a literal picture of the natural shapes and orientations of animals, especially features like filamentous antennae and delicate shells. Best of all, it can cover an additional swath of the ocean that our ship won’t have time to sample. The Zooglider still requires land-based image processing, and we can’t always identify individual species, but Zippy does a powerful job of measuring who’s out there.
We hope that Zippy will encounter Hubert the Sea Llama while he is out and about. Hubert is a sharp-witted by elusive fellow who first befriended Steve the SeaSoar when Steve was out cruising last week. We’re looking forward to hearing about that and other adventures when Zippy comes back onboard at the end of our trip! In other news, we are just finishing our first four-day cycle, which sampled the heart of the newly-upwelled water filament we are tracking. The waters have literally been green with phytoplankton, so we are curious to see what our other measurements tell us about the new waters. Stay tuned for more updates.
You know you’re off Central California in the summer when you wake up to the ship’s fog horn going off! Overnight, we sailed into thick fog off Monterey, and this morning we could barely see 20 feet away. Amazingly, as we sailed toward land, the fog lifted and we were greeted with stunning views of the mountainous Big Sur coastline gleaming in the morning sun. We even saw a pod of whales feeding several hundred feet off the ship’s bow.
Yesterday we ended our 72-hour SeaSoar transect and recovered the SeaSoar. This morning, we launched the Moving Vessel Profiler (MVP) for another all-day transect. Similar to the SeaSoar, the MVP gets towed behind the ship and completes diving profiles up and down of the upper 200 meters of the ocean. The MVP can go closer to shore, which is advantageous because we want to sample the waters right off the coast – sometimes with the bottom only 50 m deep! We are surveying this area off Big Sur in preparation for two sampling transects tonight and tomorrow night. Transects are where the ship sails in a straight line bisecting an oceanographic feature – in this case, various arms of the upwelled filament that we are tracking – and the science team conducts a series of CTD casts and zooplankton tows (to be explained more in-depth later).
We will be transiting in and out of the fog this afternoon
as we zig zag inshore and offshore on our MVP transect. We are hoping for clear
skies tonight as we start our first transect! In the words of Neil Young, “It’s
better to burn out than to fade away”.
We have officially begun our cruise’s scientific measurements! Tuesday evening, we deployed the SeaSoar, a small yellow airplane-shaped vehicle about the size of a bicycle. We will tow the SeaSoar behind the ship for three days as we sail in a radiator grid pattern (long lines from south to north and back south) off Monterey, California. The SeaSoar descends from the surface down to 300 meters and then back up, changing the pitch of its wings to control its direction. It will repeat this yo-yo pattern continuously the whole time it is deployed. SeaSoar measures water temperature, salinity, oxygen, fluorescence (an indicator of how much chlorophyll is produced by phytoplankton), and several other biogeochemical variables. We combine the SeaSoar dives into cross-sectional profiles to give us an image of what the subsurface waters off central California look like.
We do this profiling transect at the beginning of our cruise to identify and determine the water ‘feature’ that we will sample throughout the month. Our goal is to find a newly-upwelled water filament (think a triangular-shaped parcel of water, with the wide base along the coast and the tip pointing offshore) and to follow that filament as it moves progressively offshore. We have identified a potential filament off Monterey using satellite measurements of sea surface temperature and water currents, so we are cruising through the area with the SeaSoar to get additional information about the subsurface structure of the feature. We hope that this emerging filament continues to grow and move offshore, so that we have time to sample various areas of it!
We have been graced by lots of animal sightings while we do the SeaSoar survey. As we were preparing to deploy the SeaSoar on Tuesday evening, a mola mola floated by at the surface! Molas are oval-shaped bony fish with very flat bodies. They often float on their sides at the surface of the ocean, resembling large pancakes. Sharks and killer whales have been known to sample them (or perhaps use them as frisbees), but overall they are rather unpalatable. We have also seen albatrosses and other seabirds. Wednesday afternoon the sky cleared for a beautiful sunset with pods of dolphins and whales cruising alongside the ship!
We are officially underway on our 2019 CCE-LTER Process Cruise! We left San Diego Harbor yesterday afternoon under sunny skies and smooth sailing conditions, and we are now heading north toward Monterey, California. We won’t see Point Loma again until September!
The goal of our monthlong cruise is to track water filaments that are upwelled in near-coastal waters off central California and flow out to the open ocean several hundred miles offshore. We are measuring various aspects of the biological production associated with filaments: viruses and bacteria, phytoplankton and zooplankton, along with the nutrients that fuel their growth. Our cruise the latest installment in the California Current Ecosystem Long-Term Ecological Research (CCE-LTER) Program, which was started in 2004. The program consists of a core body of scientists from Scripps Institution of Oceanography and collaborators from numerous other institutions, as well as visiting scientists and volunteers from around the world. Our current cruise includes participants from as far away as Canada, France, Luxembourg, and Ghana! Yesterday evening, we stopped 20 miles offshore to test our scientific sampling equipment. Some of our graduate students and volunteers are out on their first sea trip ever, so they got a glimpse of the deployments we will be doing during the cruise. Stay tuned for future features on our various types of sampling equipment and the scientists who use them.
We are sailing on the Research Vessel (R/V) Atlantis, which is operated by Woods Hole Oceanographic Institution (WHOI) out of Massachusetts. Scripps and WHOI are both members of the University-National Oceanographic Laboratory System (UNOLS), under which ships are built for certain institutions but are shared with other institutions based on where in the ocean the ship is and where a given cruise is going. The Atlantis has a unique claim to fame: it is the mother ship of Alvin, a submersible vehicle that can carry scientists to the seafloor to explore deep-sea communities. The Atlantis and Alvin have been sampling hydrothermal vents in the Pacific Ocean for the past year, so the ship was in the right spot for our cruise. We don’t have plans for Alvin dives on our cruise, but you never know what could come up at sea!