Chasing Rhodoliths

Author: Sofie Voerman

Our team (Heidi Burdett, Beau Marsh, Sofie Voerman) has been chasing rhodoliths across the Atlantic Ocean, to a small island 350 km off the coast of Brazil. Here, rhodoliths occur up to an incredible 100m depth.  Albeit only small amounts, light still reaches those depths in the mid oceanic waters. Our divers were also enjoying the crystal clear conditions. Check out some of the amazing photos below.  This research trip was supported by a Leverhulme Trust Research Project Grant awarded to Dr Heidi Burdett in collaboration with the University of St Andrews.

The full team at  40m at a large rhodolith bed. Photo credit: @All_Angle underwater photography
Sand tilefish Malacanthus plumieri collect to build their home. Photo credit: @All_Angle underwater photography
Me and a ray at the shallow site (about 15m). Photo credit: @All_Angle underwater photography




Back To Reality

Authour: Annabell Moser

On the 16th of June we arrived back to shore and started early in the morning to unload the vessel. Andrew, Marta and I had a bet. Andrew said we could unload the vessel, dismantle our landers and pack everything back in the container in one day. Marta and I bet against it. Despite the bet, we gave our best to pack as fast as possible and after one and a half day everything was packed back in the container so we could enjoy a bit more of Hawai’i and the feeling of having actual solid ground under our feet. After being surrounded by the ocean for a whole month but never being able to go for swim, it was the first thing we did after finishing work.

Unloading the Kilo Moana

It is now a week since we started our journey back to Europe.

For me personally the cruise was an important experience. I learned about all the possibilities that can go all wrong being in the middle of the Pacific but also how to overcome these problems by working together as a team. Thank you Marta and Andrew for taking me with you on the cruise!

Cruise picture of all scientists, crew and the ROV team

For this summer, all the exciting cruises to the Pacific came to an end and I hope you enjoyed reading our blog. However, we try to keep this blog alive because there is so much more our group does from deep-sea algae to master projects all over the world.


P.s.: On this blog ( you can read even more about the adventures and the different researchers on board of the RV Kilo Moana.

Answering Questions

Author: Annabell Moser

I shared my last blog post ‘First data’ on social media like Facebook and Twitter and asked our readers what they like to know about our research cruise. Here I would like to answer the questions. I shared my last blog post ‘The first data’ on social media like Facebook and Twitter and asked our readers what they like to know about our research cruise. Here I would like to answer the questions.

Is anyone experiencing seasickness? If so, how do they deal with it?

Fortunately, I never got seriously seasick. Normally, it takes me the first days to get used to the rocking and rolling. My strategy is to eat some ginger sweets and drink ginger ale. During this cruise, it seems that nobody got severe seasickness. Worst comes to worst the only solution is to take anti-seasickness medication and rest.

Can you tell us what a ‘normal day’ on your research vessel is like?

That is a good but also a hard to answer question. Honestly, there is no such thing as a ‘normal day’. Everyday differs and the mealtimes are the only constants. For our group days divide in ‘Deployment Day’, ‘Recovery Day’ and the days in between like ‘Transit Days’ or ‘Waiting for the Lander Days’.

On a ‘Deployment Day’, we would wake up at any time of the day or night to get some breakfast. Afterwards we would start preparing for a deployment.

Respirometer Lander (Malihini):

  • Put weights on
  • Cleaning syringes
  • Attach syringes to the lander
  • Fill injectors with labelled algae
  • Turn on strobe and beacon
  • Connect and tight all plugs
  • Program the computer

Microprofiler Lander (Yellow tang):

  • Calibrate oxygen electrodes
  • Prepare and attach weights
  • Connect electrodes to lander and field computer
  • Remove protection from electrodes
  • Connect and tight all plugs
  • Program the computer
Respirometer ready to deploy!
Everyone has a last check on it before it goes down.


‘Recovery Days’ are the most nerve wracking days. When we try to communicate with our lander and tell it to come up everybody is anxious if it will work. After recovering, we process the samples and data from the deep sea. (Handling tag lines for the first time, blog post about a recovery)

Respirometer Lander (Malihini):

  • Take water samples
  • Take sediment samples
  • Sieve sediment for fauna

Microprofiler Lander (Yellow tang):

  • Take off the electrodes
  • Download the oxygen data from the field data logger (clever word for computer)

‘Transit Days’ or ‘Waiting for the Lander Days’

On these days we clean up the lab space, prepare whatever we can prepare for the deployments as labeling tubes and bottles for our samples. Marta is always writing something, from her literature review to her major report to the cruise report. Nevertheless, we also try to relax a bit by sleeping in mornings and stay up ‘late’ watching movies. (Life aboard the RV Kilo Moana, more aboutour everyday life)

Thank you for reading our blog and for the questions we received. Never hesitate to ask questions on our blog and feel free to drop a comment!

Let’s get sciency, poking and grabbing deep-sea sediments

Author: Marta Maria Cecchetto

It’s been almost a month since we have left Honolulu harbour. An exciting month collecting sediments and data from the deep blue Pacific Ocean. You will be wondering why poking and grabbing.

Well, let’s see if I can explain it.

In this case it has a literal meaning. In the past month, Andrew, Annabell and I have been poking the deep seafloor with really fine and fragile glass sensors to collect oxygen data. We sent our lander, Yellow Tang, down to 5 km deep into the ocean to observe the changes in oxygen concentrations within deep-sea sediments. Yellow Tang is what we call a micro-profiler lander as its functions is to obtain profiles of different chemicals by using different type of micro-sensors. The data from this lander can be observed immediately as we don’t have to process any samples in the lab once we are ashore.

Annabell showed and explained our data in a previous blog entry (The First Data).

 In addition to mistreating the deep sea by sticking needles into its sediments, our group has been busy measuring sediments oxygen consumption (how much the organisms in the sediments breath) and grabbing sediments samples. This was done by our second lander, Malihini, in Hawaiian means “new comer” as it has been our newest addition.

Malihini consists of three chambers of ~20 cm3 connected to three different deep-sea computers, which have the task to transmit information regarding samples collection. Once the lander reaches the seafloor (it takes 3 hours!), the chambers are programmed to start entering the sediment and different data are collected, from water to sediment samples. In addition the chambers are connected to oxygen optodes (=sensors) and algal injectors, which have the job to inject previously grown isotopically labelled algae into the chambers. Oxygen sensors are measuring the concentration of oxygen over time so we can calculate how much the organisms in the sediments are breathing over time. While at the seafloor, syringes have the job to collect water samples over time just above the sediemnts for Dissolved Inorganic Carbon (DIC) and Nutrient analyses. Once Malihini is safe on deck we start collecting sediment samples at different sediment heights, usually 0-2 cm and 2-5 cm. Sediments samples will be processed again once in the lab at The Lyell Centre, in Edinburgh, to analyse Total Organic Carbon (TOC) and sort between the different faunal assemblages present in the sediments.

Chamber 3 example_small
Malihini Chamber 3 

Isotopically labeled algae Isotopes are forms of the same element that differ in the number of neutrons in the nucleus. Usually, there is a heavy and a light isotope of carbon. 13Carbon or 15Nitrogen have one more neutron than 12Carbon or 14Nitrogen in their nucleus. Six month ago, I have grown diatoms (a type of algae) in seawater with a higher content of heavier carbon and nitrogen isotopes to obtain a substrate (the algae) standing out from normal background conditions.

As we fed the organisms present in the sediments with algae with a heavier carbon isotope ratio than normal conditions we can trace the heavier carbon isotopes and see the resulting feeding pathways among the different organisms and assess benthic (=at the seafloor) ecosystem functioning, determining how an ecosystem works based on carbon flows and turnover.

Our adventure is almost at the end, as sad as this can be it’s been a month rich in new experiences, from manning and tagging lines to see and touch animals from 5000 m depth, now, I look forward to get even more sciency and start a new chapter on the discovery of this remote and unexplored environment; lab work here we come!

The first data

Author: Annabell Moser
The countdown has started, only 8 days left of the cruise and we have accomplished 2 APEIs in the CCZ including 3 microprofiler and 4 respirometer deployments. Some were more successful than others but all together Marta gets a lot of data for her PhD thesis.
We already mentioned in a previous blog post that the microprofiler measures dissolved oxygen in the sediment. To be more precise in the pore-water which is the area between the sediment particles.

OPD_Deep Sea
Fig. 2: Oxygen sediment profile of the first APEI in CCZ. The oxygen is reaching 15 cm deep into the sediment.

Here is an example how the microprofiler data look like (Fig. 1). On the y-axis, the sediment depth (brown) and the height of the water column above (blue) is plotted (Fig. 1). The oxygen concentration in µmol is shown on the x-axis. The maximum of dissolved oxygen (also called oxygen saturation) in water depends on the temperature and the salinity. For this deep-sea site (4893 m deep), the temperature is ~2°C and the salinity is ~35, which results in an oxygen saturation of 340.4 µmol l-1. Here the oxygen concentration is half of the saturation. However, it penetrates deep into the sediment (brown coloured area) where animals and bacteria even in 10 cm depth can use it.
In shallower regions of the ocean, oxygen only penetrates a few mm into the sediment. In the below example (Fig. 2 and 3), oxygen was measured in a sediment core from the Baltic Sea (~30 m deep). The oxygen only penetrates 5 mm into the sediment, and is available only here to be used.


Fig. 2: In comparison an oxygen sediment profile from an eutrophic and shallow (30 m) area in the Baltic Sea. The depth scale is the same as in Fig. 1 
OPD_Shallow_diff scale
An oxygen sediment profile from an eutrophic and shallow (30 m) area in the Baltic Sea. Notice the different depth scale. Oxygen only reachs mm into the sediment.

Why does the oxygen penetration depth vary in different sediments?

Many different reasons determine the oxygen penetration depth of sediments such as sediment structure/size/composition, concentration of organic matter (all particles that fall from the surface layer of the ocean into the deep and function as food), organism activity such as bioturbation, oxygen concentration in the overlying water and physical parameter such as currents.
For example, high concentrations of organic matter lead to a high turnover (organic matter is used/eaten/consumed by organism) and therefore to a high oxygen consumption. The high oxygen consumption is a result of higher activity such as food/nutrient uptake by the organisms. The more active the organism are, the more oxygen they need. To create a better and more understandable picture just imagine us. The more active we are, for example while we are running, the more oxygen (we breathe faster), we need to maintain that activity. In the ocean, a high oxygen consumption leads to low concentrations of oxygen which result into a low oxygen penetration depth in the sediment. Usually, high organic matter can be found in shallower and/or eutrophic (high nutrients -> many algae -> high organic matter) areas like the example from the Baltic Sea.
In contrast, deep-sea sediments, especially here in the CCZ are highly oligotrophic (low in nutrients) since there are not enough nutrients at the surface to develop a significant amount algae that can reach all the way down to 4893 m in the form of organic matter. Therefore, the organic content is low and less oxygen is utilized (the organisms down there are more the lazy kind) resulting in a higher oxygen penetration depth into the sediments.
Actually, it is nice to experience all the theory I have learnt during my Marine Biology Master right in front of me in the middle of the Pacific. The next and last set of deployments just started. So stay tuned to hear more from our adventures.



Happy Birthday!

Author: Annabell Moser

Successfully we finished the first of three APEIs (Area of particular environmental interest) with 4 deployments, two respirometer and two microprofiler. While we are steaming to the next APEI everyone fills their free time differently. Some try to watch as many Game of Thrones episodes as possible others trying to pick up with work from home. We mainly post processing data and preparing for the coming deployments. In detail, Marta tries to get the data sorted from the oxygen optodes and electrodes. Andrew has renewed the weights on the microprofiler and I am writing this blog entry.

Yesterday, besides work there was a special occasion to celebrate, Andrew’s Birthday. For the birthday of our supervisor, Marta and I, asked the kitchen if they could bake a cake and if we could decorate it. Additionally, we drew a birthday card everybody signed and watched a movie together in the lounge. A nice change from our work/ship routine.

Handling tag lines for the first time

Author: Annabell Moser

Yesterday, Malihini, the respirometer lander was recovered a second time. This time Marta and I were on the tag lines.

When we recover our lander, the process is the following. First, the crew catches the lander from above with a hook and a tag line. Secondly, the line will be attached to the crane hook also called the headache ball. From here, the crane will turn the lander over to the portside of the stern where we finally attach two more tag lines on the side. These stabilize the lander in the air and guide the lander to a save landing on deck. Marta and I did these tag lines for the first time on a recovery. It took us some time until we finally hooked them into the sides. When we hit it, adrenaline rushed in our veins and we tried to secure it at fast as possible to the boat. With all our strength, we kept the lander as stable as possible until it landed safely on deck. After securing everything on deck, we started to process the samples Malihini brought us from Deep Ocean. Three deployments are successfully finished and there will be more to look forward to.

How to tagline
This is how the tagline gets connected to the lander and the crane
tagline_marta and I
Marta (left) and I (right) being ready to get Malihini back on deck