Home >> Oceanography >> Atlantic Explorer Cruise
BIOS Research Cruise 20 - 23 May 2019
As part of discussions with Kaitlin Noyes of BIOS about the redesign of the SGY 2 Oceanography course, I was invited to spend three days aboard their research ship, the Atlantic Explorer. Although I have worked on research ships before it has been over nine years since I was last aboard one, and then they were both dedicated to deep sea mooring replacement as part of the RAPID MOC program, so there was no biology or chemistry work carried out. Therefore, I jumped at the opportunity as it would be useful to see the current state of affairs on Bermuda's ship and how I can use this information during the next year's new course. Besides, being at sea is one of my happy places. Science and the sea - bonus!
I plan to keep a logbook going and hopefully it will give students an insight into life as an ocean scientist. |
Monday 20 May 2019
1100
Came aboard at 0800, safety briefing carried out by the mate on fire, MOB and abandon ship drills. Mustered with lifejackets at the liferaft stations.
At 1000 we cast off from BIOS and steamed out to sea – light winds and little swell. Most scientists wearing patches or wrist bands. Science briefing in the bridge deck room. Science appears to be two fold.
The ship has a number of built in labs – at least three – plus 2 labs that are in containers on the deck.
Kaitlin is here as she is producing a data collection module for her science education unit of work at BIOS – similar to me! Marcus is a young BIOS intern who is looking to become a scientist.
We are trying to stay out the way as much as possible, yet still get involved!
1155 – working in the teaching lab which has big windows. Chatted with Marcus and Kaitlin about what the goals are – to collate information on data collection techniques as well as life at sea. Kaitlin gave me details on how to view Argo float data – go to Argo website and click on the KMZ file for Google Earth. From there, click on each float and download a text file that can be imported into Excel. This would be a useful exercise for the students to do.
http://www.argo.ucsd.edu/Argo_GE.html
Also the “null earth” website that has real time animations on the ocean and atmosphere.
https://earth.nullschool.net/
Came aboard at 0800, safety briefing carried out by the mate on fire, MOB and abandon ship drills. Mustered with lifejackets at the liferaft stations.
At 1000 we cast off from BIOS and steamed out to sea – light winds and little swell. Most scientists wearing patches or wrist bands. Science briefing in the bridge deck room. Science appears to be two fold.
- Measuring how zoo plankton behave during the day and night by sampling with a large towed net at different depths at different times during the day
- Measuring how some small critters (copepods) poop. They come to surface during the day and eat and poop, then dive deep to avoid predators at night (may have this the wrong way around). But do they poop if they can’t eat? German lady in charge of this
- At the same time the usual sampling of temp, salinity and depth (CTD) will be carried out.
The ship has a number of built in labs – at least three – plus 2 labs that are in containers on the deck.
Kaitlin is here as she is producing a data collection module for her science education unit of work at BIOS – similar to me! Marcus is a young BIOS intern who is looking to become a scientist.
We are trying to stay out the way as much as possible, yet still get involved!
1155 – working in the teaching lab which has big windows. Chatted with Marcus and Kaitlin about what the goals are – to collate information on data collection techniques as well as life at sea. Kaitlin gave me details on how to view Argo float data – go to Argo website and click on the KMZ file for Google Earth. From there, click on each float and download a text file that can be imported into Excel. This would be a useful exercise for the students to do.
http://www.argo.ucsd.edu/Argo_GE.html
Also the “null earth” website that has real time animations on the ocean and atmosphere.
https://earth.nullschool.net/
1206 – aim to read and write a bit about waves before we get onto station.
1458 – been a busy few hours. Grabbed some salad for lunch and the CTD was lowered over the side. We were hove to at Hydrostation S and the CTD sent down to 1000 m deep. The winch and instrument controls are on the aft end of the bridge deck. The CTD rosette is surround by Nisken bottles that can be closed remotely to collect water samples. These are then drained off through filters when the CTD is back on deck. Partly this is to calibrate the salinity and other measurements such as dissolved oxygen. The water samples are stowed in small bottles in a lab for 24 hrs to bring them to the same temperature as the lab, as the conductivity of salt water varies as a function of salinity and temperature.
After the CTD was done, the MOCNESS was set up for a 600 m deep tow. It looks like a gigantic butterfly net with smaller cones off of it to 8” (check) diameter cylinders that can open and close at specified times. The whole net has a door at the front which is again controlled remotely.
1458 – been a busy few hours. Grabbed some salad for lunch and the CTD was lowered over the side. We were hove to at Hydrostation S and the CTD sent down to 1000 m deep. The winch and instrument controls are on the aft end of the bridge deck. The CTD rosette is surround by Nisken bottles that can be closed remotely to collect water samples. These are then drained off through filters when the CTD is back on deck. Partly this is to calibrate the salinity and other measurements such as dissolved oxygen. The water samples are stowed in small bottles in a lab for 24 hrs to bring them to the same temperature as the lab, as the conductivity of salt water varies as a function of salinity and temperature.
After the CTD was done, the MOCNESS was set up for a 600 m deep tow. It looks like a gigantic butterfly net with smaller cones off of it to 8” (check) diameter cylinders that can open and close at specified times. The whole net has a door at the front which is again controlled remotely.
Water samples – variety of tests. Some bits are filtered and frozen, to be sent to the university to run through a mass spectrometer to measure the percentage of stable isotopes of carbon and nitrogen. This is to try to determine what is fixing the carbon and nitrogen which is a major part of the carbon and nitrogen cycles. The ocean’s vast area means that the tiny amount of fixation is magnified up to a significant amount. Others are checking for urea and ammonia (are the zooplankton peeing???)
The poop sample is an odd one.
Zooplankton - https://en.wikipedia.org/wiki/Zooplankton - seem to be many different little critters rather than just one species. They are mostly microscopic and feed off plankton and in turn form the basis of the diet of bigger critters.
Plankton – the base word is “wanderer”. These are ANY organism that cannot swim, but rather just drifts wherever the sea takes them. Phytoplankton are plant-based and undergo photosynthesis, while zooplankton are animals that feed off plankton. Zooplankton can range in size from microscopic to jellyfish. They do up and down the water column though.
Night -time – at the surface to feed
Daytime – deep down, why? To hide from predators? How do they go up and down? Swim or buoyancy changes?
1600 – net recovered and samples removed. https://en.wikipedia.org/wiki/MOCNESS
The remote operation runs through the CTD cable and the connections are a constant source of problems. The loading on the cables are high.
Brooke (from University of Washington) was explaining how they are working on a protein/genome sampling of marine organisms. A lot of the common organisms have similar RNA which a high school student did a project on. The idea is to build a data base and see how the distributions change due to stressors such as acidification, pollution and temperature rise. https://www.ocean.washington.edu/
Weather forecast for tomorrow is looking a bit breezy. This will make deploying the MOCNESS and working in the labs difficult.
Toured the engine room. Ship is powered by 2 large diesel engines that are directly coupled to the prop shafts. She has three generators to power the electrical system and the hydraulics. There are two rudders and a large bow thruster for station keeping. Plus the usual water makers, sewage systems, ac systems etc.
The poop sample is an odd one.
Zooplankton - https://en.wikipedia.org/wiki/Zooplankton - seem to be many different little critters rather than just one species. They are mostly microscopic and feed off plankton and in turn form the basis of the diet of bigger critters.
Plankton – the base word is “wanderer”. These are ANY organism that cannot swim, but rather just drifts wherever the sea takes them. Phytoplankton are plant-based and undergo photosynthesis, while zooplankton are animals that feed off plankton. Zooplankton can range in size from microscopic to jellyfish. They do up and down the water column though.
Night -time – at the surface to feed
Daytime – deep down, why? To hide from predators? How do they go up and down? Swim or buoyancy changes?
1600 – net recovered and samples removed. https://en.wikipedia.org/wiki/MOCNESS
The remote operation runs through the CTD cable and the connections are a constant source of problems. The loading on the cables are high.
Brooke (from University of Washington) was explaining how they are working on a protein/genome sampling of marine organisms. A lot of the common organisms have similar RNA which a high school student did a project on. The idea is to build a data base and see how the distributions change due to stressors such as acidification, pollution and temperature rise. https://www.ocean.washington.edu/
Weather forecast for tomorrow is looking a bit breezy. This will make deploying the MOCNESS and working in the labs difficult.
Toured the engine room. Ship is powered by 2 large diesel engines that are directly coupled to the prop shafts. She has three generators to power the electrical system and the hydraulics. There are two rudders and a large bow thruster for station keeping. Plus the usual water makers, sewage systems, ac systems etc.
My favorite room on the ship is the teaching lab below the bridge deck, as it has large windows and a good view over the aft working deck and CTD crane.
Reading a book on sampling techniques. Now to write them up.
1849 – had dinner, then assisted with draining the Niskin bottles into a jug through a filer for copepods to live in for the poop experiment.
Learned a bit more about the zooplankton experiment over dinner. The diurnal migration of zooplankton is poorly understood and is considered to be the largest mass migration on the planet. The nighttime depth is about 150 m and the daytime is about 450 m.
This means that the little critters swim a long way in comparison to their size.
For a (say) 1 mm critter, swimming 300 m in a few hours would be epic – so why do it? Apparently if there is upwelling, then they can’t make the full depth, which means more food for fish and why fisherman notice and look for upwelling. The upwelling does increase the turbidity of the water, so helps to hide the critters though. So, at dusk, they swim upwards to 150 m in order to feed during the night as there is lots of phytoplankton at 120 m as seen by the fluorescence on the CTD profile. Then at dawn, they descend to 450 m during the daytime. How and why? My initial thought that it was as they eat loads and become negatively buoyant, then poop bigtime at 450 m and become positively buoyant again. This would indicate responsive behavior rather than active behavior. The scientists did not immediately poo poo my idea so maybe it is a working theory?
https://en.wikipedia.org/wiki/Diel_vertical_migration
The MOCNESS has had issues, the different nets got tangled up. The whole thing is homemade and begging for a redesign.
The poop experiment – the idea is to capture a load of copepods and place them in filtered seawater, simulate the diurnal cycle and measure the mass of poop at the end. Seems iffy science to me!
https://en.wikipedia.org/wiki/Copepod
https://en.wikipedia.org/wiki/Biological_pump
Protein Expression – “Protein expression refers to the way in which proteins are synthesized, modified and regulated in living organisms. In protein research, the term can apply to either the object of study or the laboratory techniques required to manufacture proteins. This article focuses on the latter meaning of protein expression.’
2010 – scheduled to be on deck at 0500 to help with water sampling. Sun down and heavy clouds, but gentle swell running.
Weather forecast has moderated a bit, previously they were forecasting 30-50kts! Always feel a bit nervous when I hear the words tropical storm in a forecast and am at sea!
Reading a book on sampling techniques. Now to write them up.
1849 – had dinner, then assisted with draining the Niskin bottles into a jug through a filer for copepods to live in for the poop experiment.
Learned a bit more about the zooplankton experiment over dinner. The diurnal migration of zooplankton is poorly understood and is considered to be the largest mass migration on the planet. The nighttime depth is about 150 m and the daytime is about 450 m.
This means that the little critters swim a long way in comparison to their size.
For a (say) 1 mm critter, swimming 300 m in a few hours would be epic – so why do it? Apparently if there is upwelling, then they can’t make the full depth, which means more food for fish and why fisherman notice and look for upwelling. The upwelling does increase the turbidity of the water, so helps to hide the critters though. So, at dusk, they swim upwards to 150 m in order to feed during the night as there is lots of phytoplankton at 120 m as seen by the fluorescence on the CTD profile. Then at dawn, they descend to 450 m during the daytime. How and why? My initial thought that it was as they eat loads and become negatively buoyant, then poop bigtime at 450 m and become positively buoyant again. This would indicate responsive behavior rather than active behavior. The scientists did not immediately poo poo my idea so maybe it is a working theory?
https://en.wikipedia.org/wiki/Diel_vertical_migration
The MOCNESS has had issues, the different nets got tangled up. The whole thing is homemade and begging for a redesign.
The poop experiment – the idea is to capture a load of copepods and place them in filtered seawater, simulate the diurnal cycle and measure the mass of poop at the end. Seems iffy science to me!
https://en.wikipedia.org/wiki/Copepod
https://en.wikipedia.org/wiki/Biological_pump
Protein Expression – “Protein expression refers to the way in which proteins are synthesized, modified and regulated in living organisms. In protein research, the term can apply to either the object of study or the laboratory techniques required to manufacture proteins. This article focuses on the latter meaning of protein expression.’
2010 – scheduled to be on deck at 0500 to help with water sampling. Sun down and heavy clouds, but gentle swell running.
Weather forecast has moderated a bit, previously they were forecasting 30-50kts! Always feel a bit nervous when I hear the words tropical storm in a forecast and am at sea!
Tuesday 21 May 2019
0757 – up at 0500 to sample the CTD, drawing water for bacteria samples from the Niskin bottles into Falcon tubes (pointy ends) 40 ml. Then taking them into a lab under a fume hood. Used a fancy pipette to draw off 1.0 ml of each sample twice into cyrotubes that would be frozen at -80 deg C. Before they went into the freezer I had to add 0.05 ml of formalydhyde using another fancy pipette to 'fix' them - which I took to mean kill them but stop them decaying. These will be analysed later back at BIOS.
Breakfast and coffee!
Weather is a bit worse, about 15 kts, grey and overcast with seas about m high. Light rain starting.
MOCNESS went over the side and is now recovered and the copepod hunting continues. One thing that I noticed in the samples is the huge amount of stuff in the water – this is called Marine Snow and it falls at terminal velocity to the sea bed. Comprised of dead stuff and outerlayers of shedded skin. Including one very complex looking shell of see through cartilage. The terminal velocity of this stuff is so slow that it can take over a year to hit the bottom and form the sediments that make up the seafloor.
https://en.wikipedia.org/wiki/Marine_snow
Weather forecast is for Subtropical depression Andrea to pass near us – max winds 35 kts at the moment.
Breakfast and coffee!
Weather is a bit worse, about 15 kts, grey and overcast with seas about m high. Light rain starting.
MOCNESS went over the side and is now recovered and the copepod hunting continues. One thing that I noticed in the samples is the huge amount of stuff in the water – this is called Marine Snow and it falls at terminal velocity to the sea bed. Comprised of dead stuff and outerlayers of shedded skin. Including one very complex looking shell of see through cartilage. The terminal velocity of this stuff is so slow that it can take over a year to hit the bottom and form the sediments that make up the seafloor.
https://en.wikipedia.org/wiki/Marine_snow
Weather forecast is for Subtropical depression Andrea to pass near us – max winds 35 kts at the moment.
1035 – bit of downtime for me at the moment, so caught some much needed sleep. Last night I had forgotten how cold it is aboard a ship with the ac always on throughout. And how thin the blanket that they give you is! So too chilly to sleep, but not cold enough to force me up and put more clothes on, so all told not much sleep. Ugg.
The CTD
The CTD (conductivity, temperature and depth) is a large frame of instruments and water bottles, called Niskin bottles, that is the standard equipment for sampling the water column. The principal instruments are conductivity sensor to measure the salinity, temperature sensor and a pressure sensor to measure the depth. You could in theory use the amount of cable paid out by the winch for the depth, but as the cable gets longer, it gets heavier and starts to stretch – so is not a reliable measuring device. Other sensors such as fluorescence (to detect photosynthesis) and dissolved oxygen are included.
The hydrostatic pressure essential is linear with depth, so correlates well. The conductivity of seawater varies as a function of salinity and temperature, so an accurate temperature reading is required to determine the salinity. The variation of temperature and salinity affects the density of the seawater, so is the major cause of convection and currents. Ocean physics depends on accurate vertical density profiles. The Niskin bottles are open tubes, so that they don’t crush under the pressure, with spring loaded end caps that can be ‘fired’ off by the CTD controller at ‘bottle stops’. As water cannot be compressed the sealed bottles will not explode as the CTD is brought up.
To prep the CTD, the deck crew open and cock the bottles on their trigger levers, check the top air and bottom sampling valves are closed and remove the buffering water syringes from the two conductivity sensors. To deploy can be tricky and dangerous in rough seas. The ship is hove to with the starboard bow in to wind so that that ship is lying about 60 deg to the waves. The cable is taken up to lift the CTD off the deck. It is held under control by two deckhands with ropes to stop it swinging out of control. The crane is then swung outboard and the CTD allowed to swing slowly over the water. Then it is lowered as the guide ropes are released. Once below the surface it is more stable. The danger for the ship is that the CTD barely wobbles as the ships rolls due to the weight of the cable and the drag through the water, so that the loads on the cable vary as the ship rolls. The ship slowly drifts with the wind and waves as the CTD is lowered and raised by the winchman.
The winch is a complex piece of machinery that has to pay out the cable under heavy load and bring it back in, without jamming! It is hydraulically powered. The scrolling mechanism on the front enables a neat and tight lying of the cable on the drum – otherwise it would be impossible to stow 6000 m of cable! The closing of the Niskin bottles is controlled by the main computer and the depths of the relevant bottles is recorded.
The CTD
The CTD (conductivity, temperature and depth) is a large frame of instruments and water bottles, called Niskin bottles, that is the standard equipment for sampling the water column. The principal instruments are conductivity sensor to measure the salinity, temperature sensor and a pressure sensor to measure the depth. You could in theory use the amount of cable paid out by the winch for the depth, but as the cable gets longer, it gets heavier and starts to stretch – so is not a reliable measuring device. Other sensors such as fluorescence (to detect photosynthesis) and dissolved oxygen are included.
The hydrostatic pressure essential is linear with depth, so correlates well. The conductivity of seawater varies as a function of salinity and temperature, so an accurate temperature reading is required to determine the salinity. The variation of temperature and salinity affects the density of the seawater, so is the major cause of convection and currents. Ocean physics depends on accurate vertical density profiles. The Niskin bottles are open tubes, so that they don’t crush under the pressure, with spring loaded end caps that can be ‘fired’ off by the CTD controller at ‘bottle stops’. As water cannot be compressed the sealed bottles will not explode as the CTD is brought up.
To prep the CTD, the deck crew open and cock the bottles on their trigger levers, check the top air and bottom sampling valves are closed and remove the buffering water syringes from the two conductivity sensors. To deploy can be tricky and dangerous in rough seas. The ship is hove to with the starboard bow in to wind so that that ship is lying about 60 deg to the waves. The cable is taken up to lift the CTD off the deck. It is held under control by two deckhands with ropes to stop it swinging out of control. The crane is then swung outboard and the CTD allowed to swing slowly over the water. Then it is lowered as the guide ropes are released. Once below the surface it is more stable. The danger for the ship is that the CTD barely wobbles as the ships rolls due to the weight of the cable and the drag through the water, so that the loads on the cable vary as the ship rolls. The ship slowly drifts with the wind and waves as the CTD is lowered and raised by the winchman.
The winch is a complex piece of machinery that has to pay out the cable under heavy load and bring it back in, without jamming! It is hydraulically powered. The scrolling mechanism on the front enables a neat and tight lying of the cable on the drum – otherwise it would be impossible to stow 6000 m of cable! The closing of the Niskin bottles is controlled by the main computer and the depths of the relevant bottles is recorded.
Once the CTD is recovered and secured to the deck, the scientists rush out to take the samples from the Niskin bottles to test for a variety of sciency stuff:
Ships are an expensive platform to work on – Atlantic Explorer costs the US taxpayer $1000/hr to run, although the costs would be almost the same if she were just in port and not on a cruise.
- Bacteria
- pH
- Salinity – to calibrate the instruments if required.
- Dissolved solids
- Carbon isotopes
- Other stuff that I don’t know about yet!
- Some water is bled off through a filter to support the captured copepods while experiments are done on their pooping habits.
Ships are an expensive platform to work on – Atlantic Explorer costs the US taxpayer $1000/hr to run, although the costs would be almost the same if she were just in port and not on a cruise.
|
Far better video than the one that I attempted to make! He explains the CTD and what it is measuring.
|
1258 – been sampling the CTD bottles again, this time filling 4 litre bottles for isotope analysis. The idea is to find isotopes of carbon and nitrogen, as the ocean plays a major role in the carbon and nitrogen cycles. Still unclear exactly how this experiment is run. But the sampling is wet and fun, especially with the ship rolling and water occasionally sloshing over the side and under the deck grills. Put the tube on, open the air vent, place tube in bottle and open valve. Rinse twice using the Niskin water and then fill the bottle. Easy stuff.
1646 – went lay down for a bit and crashed out for a couple of hours! Groggy headed now. Seas still ok, winds 25-30 kts but this is a big ship and only gently rolling. Some of the scientists still feeling it. Think that I have annoyed every one of them with my questions and trying to help!!
Saying that, I am now helping do the pipette sampling for bacteria at 1745.
1910 – sampling done!
Down time until 2100, when the next copepod hunt starts.
Saying that, I am now helping do the pipette sampling for bacteria at 1745.
1910 – sampling done!
Down time until 2100, when the next copepod hunt starts.
Wednesday 22 May
0913 – Up at 0600 to watch the preparations for the 0700 MOCNESS deployment, overnight the scientists were having ongoing problems with the built in CTD unit so issues with the depth measurements. I don’t have much to do until the CTD rosette goes overboard at 1100. Been reading about the properties of water that make it so important.
Also, trying to find out the principle behind measuring the Dissolved Oxygen content.
https://www.thebermudian.com/heritage/heritage-heritage/the-devils-hole/
https://www.wikihow.com/Measure-the-Dissolved-Oxygen-Level-of-Water
1136 – prepped the CTD, which I am getting the hang of now and the crew deployed it over the side. The bridge must always be connected with as the ship must be hove to and cannot maneuver while the CTD is over the side. Given that the maximum winching speed is 50 m/min, and the depth on this trip is usually 1000 m, it takes a while to winch it back up! *** how long? **** So, the bridge needs to ensure that there is no shipping that could cause issues.
1400 – still downtime for me, so I have been working on the new oceanography modules.
2100 – been a busy afternoon and evening in moderately rough seas. Lowered the CTD twice and sampled from it, first time for water for the pooping experiment and filtering more precious drip feed water. Then cleaning filters for a chlorophyll experiment and then prepping and lowering a second CTD for a whole range of sampling experiments, where I collected and spiked the bacteria samples. This entails collecting 40 ml of water in a Falcon tube (large with pointed end), then takng to the fume cupboard and using a fancy pipette drawing off 1.0 mm into a small cryotube – being careful with labels – then adding a fixicant called PFA to ‘lock in the bacteria’, these tubes are then stowed in a -80 dec C freezer. The Falcon tube samples are then ‘spiked’ with formaldehyde and stored in a “dead fridge”. After helping out with some other odd jobs it was time for bed!
Also, trying to find out the principle behind measuring the Dissolved Oxygen content.
https://www.thebermudian.com/heritage/heritage-heritage/the-devils-hole/
https://www.wikihow.com/Measure-the-Dissolved-Oxygen-Level-of-Water
1136 – prepped the CTD, which I am getting the hang of now and the crew deployed it over the side. The bridge must always be connected with as the ship must be hove to and cannot maneuver while the CTD is over the side. Given that the maximum winching speed is 50 m/min, and the depth on this trip is usually 1000 m, it takes a while to winch it back up! *** how long? **** So, the bridge needs to ensure that there is no shipping that could cause issues.
1400 – still downtime for me, so I have been working on the new oceanography modules.
2100 – been a busy afternoon and evening in moderately rough seas. Lowered the CTD twice and sampled from it, first time for water for the pooping experiment and filtering more precious drip feed water. Then cleaning filters for a chlorophyll experiment and then prepping and lowering a second CTD for a whole range of sampling experiments, where I collected and spiked the bacteria samples. This entails collecting 40 ml of water in a Falcon tube (large with pointed end), then takng to the fume cupboard and using a fancy pipette drawing off 1.0 mm into a small cryotube – being careful with labels – then adding a fixicant called PFA to ‘lock in the bacteria’, these tubes are then stowed in a -80 dec C freezer. The Falcon tube samples are then ‘spiked’ with formaldehyde and stored in a “dead fridge”. After helping out with some other odd jobs it was time for bed!
What is it about these zooplankton?
In terms of overall biomass, the zooplankton diurnal vertical migration is by far the biggest in the world. Gazillions of tiny zooplankton move up and down the water column between 150 m and 450 m every day. Night time at the upper layer and at the deeper depths during the day. Some of the zooplankton is really small, i.e. less than 2 mm in size. The terminal velocity of them is very slow, although Amy was unsure if it has ever been measured. Form most marine snow of a similar size and mass, the terminal velocity (where their weight is balanced by the upwards drag of water) is so slow that it can take up to a year to reach the ocean floor. So the zooplankton cannot be in free fall. The water itself is often not sinking at that rate either - so the critters must either be changing buoyancy or swimming. The swimming hypothesis is the most likely. Certainly they can accelerate really really fast when I tried to suck them into a pipette. But for a 2 mm critter, swimming 300 m in a few hours day in and day out is no mean achievement. The other major question is why do they do it? The light at 150 m depth in the tropical ocean is only about 1 % of that at the surface, at 450 m, there is far less. The most obvious, and yet unproven, theory is that they do it to escape predators. They can't stay at the deeper depth for long though as there is no photosynthesizing phytoplankton at that depth, so respiration will be consuming resources faster than they can be replaced. As the CTD graph showed, the majority of the phytoplankton exist between the surface and 150 m.
Another question springs to mind, which is that this is all very fascinating, but why care? They have obviously being going up and down the water column for millions of years and we have never noticed. Why get interested now? As with everything it is to gain a deeper understand of the carbon cycle in the oceans. Carbon dioxide is absorbed the phytoplankton and fixed as carbohydrates and other biological molecules. During the night, the zooplankton feed off these and some carbon dioxide is released during respiration. Once they have dived to the deeper levels, they defecate (poop - nicknamed zoopoop) and some of this carbon is actively transported to the deep ocean. Therefore, the vertical migration of zooplankton is assisting in the active transport of carbon from the surface to the ocean, where it may remain for centuries. And a significant amount of it too - between 15 - 40% of the organic carbon in the ocean globally. The major objective of this cruise is to gather data to better understand the process of the vertical migration and how the zooplankton metabolism changes as a response to light, pressure and temperature. Hence the poop experiment and the respiration experiment. Future studies will also try to quantify the volumetric density (average number per cubic metre of ocean) of these little understood critters.
References:
https://www.nature.com/scitable/blog/saltwater-science/what_makes_plankton_migrate
https://www.us-ocb.org/zooplankton-vertical-migrations-represent-a-significant-source-of-carbon-export-in-the-ocean/
http://www.bios.edu/currents/scientist-at-work-a-conversation-with-bios-biologist-amy-maas
In terms of overall biomass, the zooplankton diurnal vertical migration is by far the biggest in the world. Gazillions of tiny zooplankton move up and down the water column between 150 m and 450 m every day. Night time at the upper layer and at the deeper depths during the day. Some of the zooplankton is really small, i.e. less than 2 mm in size. The terminal velocity of them is very slow, although Amy was unsure if it has ever been measured. Form most marine snow of a similar size and mass, the terminal velocity (where their weight is balanced by the upwards drag of water) is so slow that it can take up to a year to reach the ocean floor. So the zooplankton cannot be in free fall. The water itself is often not sinking at that rate either - so the critters must either be changing buoyancy or swimming. The swimming hypothesis is the most likely. Certainly they can accelerate really really fast when I tried to suck them into a pipette. But for a 2 mm critter, swimming 300 m in a few hours day in and day out is no mean achievement. The other major question is why do they do it? The light at 150 m depth in the tropical ocean is only about 1 % of that at the surface, at 450 m, there is far less. The most obvious, and yet unproven, theory is that they do it to escape predators. They can't stay at the deeper depth for long though as there is no photosynthesizing phytoplankton at that depth, so respiration will be consuming resources faster than they can be replaced. As the CTD graph showed, the majority of the phytoplankton exist between the surface and 150 m.
Another question springs to mind, which is that this is all very fascinating, but why care? They have obviously being going up and down the water column for millions of years and we have never noticed. Why get interested now? As with everything it is to gain a deeper understand of the carbon cycle in the oceans. Carbon dioxide is absorbed the phytoplankton and fixed as carbohydrates and other biological molecules. During the night, the zooplankton feed off these and some carbon dioxide is released during respiration. Once they have dived to the deeper levels, they defecate (poop - nicknamed zoopoop) and some of this carbon is actively transported to the deep ocean. Therefore, the vertical migration of zooplankton is assisting in the active transport of carbon from the surface to the ocean, where it may remain for centuries. And a significant amount of it too - between 15 - 40% of the organic carbon in the ocean globally. The major objective of this cruise is to gather data to better understand the process of the vertical migration and how the zooplankton metabolism changes as a response to light, pressure and temperature. Hence the poop experiment and the respiration experiment. Future studies will also try to quantify the volumetric density (average number per cubic metre of ocean) of these little understood critters.
References:
https://www.nature.com/scitable/blog/saltwater-science/what_makes_plankton_migrate
https://www.us-ocb.org/zooplankton-vertical-migrations-represent-a-significant-source-of-carbon-export-in-the-ocean/
http://www.bios.edu/currents/scientist-at-work-a-conversation-with-bios-biologist-amy-maas
Thursday 23 May
0116 – woke up shortly before 0100 as I am a light sleeper and instantly noticed that the ship has stopped rolling and is steaming downwind at 8 kts. She is being repositioned to the leeward side of the island as the seas are getting too rough for some of the scientists and the SW side of the island may provide more shelter from the swells. Motion is now very smooth as the ship is running directly ahead of the waves. This will change once we get on station and heave to lower and tow a zooplankton net at 0200. Next CTD has been shifted to 0500. Back to sleep for me!
0630 – up and waiting for the person to get out of the shower…. Could be a while! Crew on deck getting ready to deploy the MOCNESS. We are about 5 miles SW of the island, can clearly see Gibbs Hill off the port bow. Feel sad that this is the last day. Trying to think about the plan for the next few days – pushing hard to get the early units for the new course completed at least in the online version. Could add more depth to everything. Need to think about a year 9 assessment.
0630 – up and waiting for the person to get out of the shower…. Could be a while! Crew on deck getting ready to deploy the MOCNESS. We are about 5 miles SW of the island, can clearly see Gibbs Hill off the port bow. Feel sad that this is the last day. Trying to think about the plan for the next few days – pushing hard to get the early units for the new course completed at least in the online version. Could add more depth to everything. Need to think about a year 9 assessment.
Burning Fuel
Note about diesel: Main engines at full whack burn 1200 gallons per day. The generators together can consume about 600 gallons a day. Most of the time the ship can run on one generator, switching out for another for servicing etc. If lots of deck work is being done, another generator is needed to power the hydraulic systems. As we have been only on 1 engine at low speeds, the engineer estimates that we will have used only about 300 gallons total for the trip.
Weather is calmer on this this side of the island, just a slow swell of about 6 m wavelength as we are in the lee off the south shore beaches. Some rain on the horizon.
1100 - Lowered the CTD for the last time and drew 4 litres from each bottle for Shannon's poop experiment.
Stood out to sea to dump the ship's sewage tanks, then turned for home.
1830 - Hove to off Sea Buoy waiting for the pilots to come aboard.
1900 - Berthed up at Penno's Wharf next to a superyacht and the tall ship, 'Picton Castle'.
Note about diesel: Main engines at full whack burn 1200 gallons per day. The generators together can consume about 600 gallons a day. Most of the time the ship can run on one generator, switching out for another for servicing etc. If lots of deck work is being done, another generator is needed to power the hydraulic systems. As we have been only on 1 engine at low speeds, the engineer estimates that we will have used only about 300 gallons total for the trip.
Weather is calmer on this this side of the island, just a slow swell of about 6 m wavelength as we are in the lee off the south shore beaches. Some rain on the horizon.
1100 - Lowered the CTD for the last time and drew 4 litres from each bottle for Shannon's poop experiment.
Stood out to sea to dump the ship's sewage tanks, then turned for home.
1830 - Hove to off Sea Buoy waiting for the pilots to come aboard.
1900 - Berthed up at Penno's Wharf next to a superyacht and the tall ship, 'Picton Castle'.