Featured photo: Night recovery of the multicorer
Its been a hectic couple of days! First, we had two successful core deployments off Jervis Bay in just about a kilometer and a half of water (1500 m) ! The cores looked great!
Nice clear sediment-water interface in the core (clear overlying water!). The one on the far right slid on recovery so we couldn’t use it.
Minimal disturbance, so we were able to keep and process 11 out of the 12 cores! And what a show during recovery! The deployments happened in the middle of the night, and the light from the ship attracted the dolphins (well attracted the squid and the fish that the dolphins wanted to feed on!) So many dolphins, and so acrobatic. Flying all over and making quick turns as they tried to catch a snack.
Dolphins feeding as we waited for the core recovery. Hard to get a decent shot with only the lighting from the ship but so cool to watch.
As we were busy processing the cores over the next day and a half, the Investigator began a transit North- our goal, enter the East Australian Current around Coffs Harbour, and follow a water mass as it moved south in the current! This meant deploying floats into the current, called ‘drifters,’ that then call back their location to the ship about every 2 hrs allowing the ship to stay close. While drifting we were regularly taking water samples, running incubations, and taking CTD profiles. Staying with the current took us almost 200km to the south in less than 3 days!
CTD water samples to bring back for rare earth element (REE) analysis next to the initial report on the CTD including the depth each bottle was fired at, and the temperature/pressure/salinity at that depth. Most CTDs on this voyage are deployed within the upper 1000 m (focus on the East Australian Current and shifts in community immediately below it), but the CTD was deployed once to 4000 m towards the southern end of the transect (and will be again to the north). For REEs, we’re only pulling water from these deeper 4000 m deployments.
Then, as soon as the cores from 1500 m were processed we got another set of cores from 2600 m in a location to the north of Sydney! Another great set of cores. This particular site was on the edge of a submarine canyon.
A rendering of the bathymetry near surrounding our 2600 m site using swath profiles taken by the R/V Investigator’s underway systems (courtesy of Dave Watts). Dark blues represent deeper water (about 4000 m on this scale) and yellows are closer to 200 meters. The green ‘ship’ indicates our location in the Tasman Sea. The ship had to hold for nearly 5 hours for 2 successful deployments in the current and strong winds- drifting onto the ridge to the south would have likely compromised our ability to collect sediment!
The range of science being done on board is still amazing. While we were processing multiple cores looking to get 5 nanograms of neodymium per pore water interval in order to measure isotopes (that’s 0.000000005 grams) others were carefully watching the horizon as part of a marine mammal survey- a major part of which has been counting humpback whales. Humpback that can weigh more than 30,000 kilograms (30,000,000 grams)! Talk about a range in sizes! And everything in between! Microbes, plankton, larval fish– one of the nets even brought up a tiny squid the other night! And a spotting of a sperm whale had everyone excited.
A tiny squid (4-6cm in length) was brought up in one of the night net tows.
Morgan changes the filters on the atmospheric sampling system. She’s looking at trace metal deposition from the atmosphere (including dry air and wet from a rain sampler) as well as doing trace metal sampling in the water on this voyage.
The R/V Investigator is equipped with many underway systems. These instruments give a constant stream of information to scientists on board, ranging from sea surface temperature and salinity (helps us track a water mass), current direction and speed, bathymetry, and the location of plankton and fish below us (the EK60 sounders-these range from 18 to 200 kilohertz (KHZ). Kilohertz is a measurement of frequency, with 18 KHZ having a lower frequency than a 200 KHZ. The frequency determines both the range that is observable and the size of the critters that can be detected. The lower frequencies can travel further (thus we can see whats going on at the deeper sites) but they are less sensitive, whereas the higher frequencies are better resolution (can see the tiny plankton swarms) but don’t penetrate as deep in the water column). Many of these are part of the ship’s drop keels. These were specifically designed for scientific purposes and allow sampling below the influence of the ship’s hull. There is also a supply of underway seawater brought on board for additional sampling (such as dissolved inorganic carbon (DIC) and diatom abundances).
This schematic of the instrumentation of the Gondola and Drop Keels on the Investigator is posted in the operations room
Looking down at the drop keel from inside the ship. This area is restricted access for obvious safety reasons, but can be viewed on an engine room tour given by Chris, the ship’s engineer.
We’re busy, science is happening around the clock- even during transits, we’re normally catching up on samples from the last stop, sampling underway seawater, or preparing for the next location. But we still have fun! Part of going to sea is the unique souvenirs! Styrofoam cups and permanent markers may not seem that exciting on shore, but when you’re sending equipment down 1000, 2000, sometimes even 4000 m all of a sudden the cups seem a lot more exciting. The pressure at depth forces the air out of the cup, making miniature cups (and making the drawings look so much better for those of us that can’t draw!). Remember for every 10m of water, the pressure increases about 1 atmosphere… so by 4000 m thats 400 atmospheres (400x the pressure at sea level!). Cups sent down to 100 m come back bigger than those sent to 4000 m.
Stockings make great holders for cups. Here are some stockings filled with cups ready to be attached to the CTD rosette for a 4000 m deployment.
And a cup upon its return! Almost thimble sized instead of cup size!
We’ve also had quite a few birthdays on board: instead of several small celebrations, our chefs took out all the stops and put on a spectacular ‘half-way through’ buffet last weekend.
The dessert table for our combined birthdays half-way celebration. Everything was delicious and they were sure to accomodate the various dietary restrictions.
Also, check out my blog post for the official CSIRO R/V Investigator blog at: https://blog.csiro.au/voyage-meaning-life-ocean-microbes/
It has a dolphin video!!