Shelf Sea Biogeochemistry blog

Showing posts with label Shelf Seas Biogeochemistry programme. Show all posts
Showing posts with label Shelf Seas Biogeochemistry programme. Show all posts

Sunday 15 March 2015

Meet Jo Cox, the first female captain of any NERC owned research vessel.

On Monday we continued our work at sites H and I as well as the spatial survey which we are carrying out between the sites. There will be more about the spatial survey later in the blog, as today’s post is focused on the most important person on the ship.  Jo Cox is the captain of the RRS Discovery, and indeed the first female captain of any NERC (Natural Environment Research Council) owned research vessel.

Jo has always been a keen sailor and spent most of her childhood sailing in circles round a reservoir at weekends, however she took an unconventional path towards a career at sea spending five years training as an engineering apprentice and test engineer with Land Rover. During her apprenticeship she was given the opportunity of sailing on a Tall Ship (Sail training for children and young adults), spending 10 days sailing on the schooner Winston Churchill.


Jo Cox, captain of the RRS Discovery, and the first female captain of any NERC owned research vessel.

After that, she was hooked and she spent most of her annual leave and most weekends sailing offshore. “I loved my job at Land Rover, but my heart was rapidly over-ruling my head, so I took the plunge and quite literally ran away to sea.”

Since running away to sea, Jo has sailed on a variety of ships from a 300,000t tanker, to an old general cargo ship on a round the world trip. One trip stood out above the rest with 6 months spent on the British AntarcticSurvey (BAS) vessel RRS James Clark Ross (JCR). “I loved the science work that the vessel undertook, the range of people that I came across, and of course, the beauty of the Antarctic was also pretty amazing.”

Following this BAS offered her a 3rd mate position on the JCR, and she spent the following 10 years working for BAS on the JCR and the other UK Polar ship the RRS Ernest Shackleton. In 2012 a change of career beckoned and Jo left the open waves to spend three seasons working as the Government officer in an Antarctic base on the island of South Georgia manned by BAS scientists; however with each passing season her desire to return to sea got greater and this lead her to apply for the vacant Masters position on the RRS Discovery.
 “The Masters position on RRS Discovery represented an amazing opportunity to work at the cutting edge of research, on a purpose built vessel with the ability to carry out a fantastic range of scientific activities.”

Coming from an engineering background, Jo has only ever worked in male dominated environments and offered the following advice to other women considering a career at sea. 

"The maritime industry offers a fantastic career opportunity for anyone with the commitment and dedication that is required to pursue it. In doing so there are inevitable sacrifices, but the rewards and job satisfaction more than make up for it. Women at sea are no longer the rarity that they once were, and with each passing year there are a steadily increasing number reaching the ranks of Master and Chief Engineer. It’s certainly not for everyone, but if you’re willing to get stuck in and work hard then the opportunities are out there.”

She also offered the following advice to scientists concerned with making her life at sea a little less stressful – “Be organised and be ready on time…..”

Sound advice I think….

Wednesday 11 March 2015

Deploying the Cefas Lander and the SmartBuoy

Louis Byrne, British Oceanographic Data Centre, NOC

Wednesday saw the deployment of two moored instrument suites owned by Cefas. The first deployment was a lander similar to the NOC-L (National Oceanography Centre, Liverpool) Mini-STABLE lander deployed earlier in the cruise, although the instruments attached to the Cefas minilander are very different.

The Cefas lander has an ADCP (Acoustic Doppler Current Profiler), which uses the Doppler affect to measure current speed and direction through the water column. As well as the ADCP there is a water sampler collecting a sample of water in a plastic bag (to be analysed for nutrients on land after the mooring is retrieved) and other instruments measuring a variety of parameters including temperature, chlorophyll fluorescence and optical backscatter (a way of measuring how many particles are in the water, which is useful for determining how much sediment any storm events may mix into the water column).

 


A Cefas SmartBuoy on deck

The second one was a Cefas SmartBuoy which was deployed at the same location as the lander but instead of resting on the seabed it floats on the surface. The SmartBuoy has all the same instruments that are on the lander as well as a water sampler which will collect one sample of water each day for analysis back at the lab.

The Lander and the SmartBuoy are useful because they can provide long term high resolution background data. The overall UK SSB programme is a seasonal project, lasting one year, and repeatedly sampling the same sites to see how the processes affecting the carbon and nitrogen cycles vary between the seasons.

The seasonal changes in the Celtic Sea primarily revolve around the development of water column temperature stratification in spring, through to when it breaks down in late summer to early autumn (see the previous blog post for an explanation to  this process and the resulting phytoplankton blooms).



A Cefas SmartBuoy after being deployed in the Cetic Sea

The data collected by the SmartBuoy and minilander provide very useful data on the timing and magnitude of the development of stratification and the phytoplankton blooms. The chlorophyll fluorescence and oxygen sensors attached to the SmartBuoy on the sea surface can detect the start of the phytoplankton bloom as phytoplankton use chlorophyll to photosynthesise, a process which produces oxygen as a by-product.

Meanwhile on the seabed, when stratification develops there will be a decrease in oxygen. This is because aerobic bacteria and the countless other marine organisms which require oxygen will continue to use it, however, as this layer has now been cut off from the surface (by the thermocline) the oxygen diffusing into the  surface water from the atmosphere does not make it down to the water below the thermocline quick enough to replenish it. This decrease in oxygen will be picked up by the oxygen sensor attached to the Cefas minilander. The minilander is also able to detect when the phytoplankton bloom dies off, as the large influx of dead phytoplankton cells falling down through the water column (also known as Marine Snow) will cause a peak in chlorophyll and later a further decrease in oxygen, as the phytoplankton are consumed.



Large amount of marine particles or marine snow in suspension just above the sea floor. Image credit:

 https://phys.org/news/2013-07-marine-scientists-explore-biodiversity-ecosystems.html

By measuring the biogeochemical changes which revolve around the development and breakdown of stratification, the data from the Cefas minilander and SmartBuoy can help put the rest of the data collected during SSB into context, by placing the measurements taken during this cruise within the seasonal cycle that this region experiences.

Tuesday 10 March 2015

Springtime phytoplankton blooms in the Celtic Sea

Louis Byrne, British Oceanographic Data Centre, NOC

The seasonal changes in the Celtic Sea primarily revolve around the development of water column stratification in spring and when it breaks down in late summer to early autumn.  Right now in March, the Celtic Sea is fully mixed, however with the days getting longer and warmer (we hope), the surface of the Celtic Sea is also warming. As the surface warms its density decreases and the water becomes lighter compared to the colder waters below which don’t have access to the suns heat. (Fig 1.) To help watch for these changes we have a daily set of sea surface chlorophyll and temperature satellite images sent from the NEODAAS team at PML to the ship, and any developments of blooms and changes to the temperature can be seen as they occur.


Fig. 1: Temperature profiles in the mid latitudes in the ocean. Dashed (- - - -) line is for the winter and the continuous line for the summer season
.Source: https://nptel.ac.in/

This will eventually result in the creation of two distinct bodies of water, with a warm surface layer resting above a colder layer below, much like a cocktail which often have two or three coloured layers sitting on top of one another.

As well as causing the onset in stratification, the increase in temperature and sunlight also causes a truly massive increase in the number of phytoplankton in an event known as a plankton bloom [many plankton blooms are so large they can be seen from space! (see Fig.2)]. This results in a feeding frenzy as zooplankton (Fig. 3) numbers surge and they are in turn eaten by other organisms, passing the energy down the food web.


Fig. 2: Plankton Bloom in the Celtic Sea. Captured by the Envisat's Medium Resolution Imaging Spectrometer (MERIS) on 23 May 2010. Credits ESA

The phytoplankton bloom starts just before the onset of stratification, and then continues in the surface layer as the water there is warmer and receives much more sunlight. Eventually the phytoplankton will use all of the nutrients available in the surface layer and most of the plankton will die off. When this happens their cells will fall through the water column, causing a large increase in the biological material available on the seabed.


"Copepodkils". Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Copepodkils.jpg#/media/File:Copepodkils.jpg
 
When stratification breaks down at the end of summer, the water column in the Celtic Sea is again fully mixed. The bottom layer of water is still nutrient rich and these nutrients are also mixed into the surface of the water column, and become available for photosynthesis. This causes a smaller phytoplankton bloom at the end of summer before the days darken, and the cycle is complete.

Saturday 7 March 2015

What is happening in the benthos?

Louis Byrne, British Oceanographic Data Centre, NOC

The seas picked up again on Saturday and unfortunately again a few members of the science crew have been feeling a bit green, however the strong winds left us on Sunday and we had our first days’ proper sunshine of the cruise, complete with the obligatory sunset photograph, but not the fabled green flash!

The focus on this cruise is on processes that are happening in the benthos – meaning the environment above and within the seabed – and how these processes change as the seabed moves from sandy sediment to muddy sediment. To do this we are investigating four sites which are characterised as sand, sandy mud, muddy sand and mud. We managed to complete the NIOZ coring of the sandy site (Site G) over Sunday night, giving our sedimentologists some sandy samples to analyse along with the muddy sediment collected from site A.


A sample of sandy sediment ready to be sliced

Natalie Hicks (SAMS) is using the samples collected by the NIOZ corer to investigate the dynamics of benthic carbon cycling, including how deep and for how long carbon is stored in the different types of marine sediments, and how much is released back into the water column. She is collecting sediment samples from the seabed to a depth of 25 cm and then slicing it into cross sections, with each slice containing sediment from a different depth. These will then be stored in a freezer until the end of the cruise, when they are taken back to the laboratories in the Scottish Association for Marine Science (SAMS) to be analysed.

 


Natalie slicing her core into cross sections

Back at SAMS, the sediments will be analysed for their porosity, which refers to how much space there is for water between the grains in the sediment. Muddy sediment has smaller grains which fit together more tightly than sandy sediment, leaving less space for water between them. This makes it easier for pockets of water deeper in the sediment to be cut off from the sea water above.

Once this happens the water in the pocket will quickly run out of oxygen (there will be more about this later in the blog), making it impossible for aerobic bacteria (they are the ones requiring oxygen for respiration) to consume the organic matter in the water. This organic matter will then be stored in the sediments, unless it is resuspended through physical water movement or animal activity.
 



A NIOZ core about to be dropped into the Celtic Sea

Apart from the porosity and grain size, the carbon (both inorganic and organic) is measured as well as the amount of the lead isotope,
210Pb. The carbon is measured so that we can have an idea of how much biological material is buried within the different sediment types.  210Pb is measured as it can be used as an indicator for how often the sediment at each depth is being resuspended or accumulated. Putting all of these measurements together, can give you a better understanding of benthic carbon cycling, and how this differs between the different sediment types

All of this is important so that we can determine whether each sediment type is a source or a sink of carbon. If we can understand better how deep carbon needs to be buried in the different sediments before it is sequestered (stored permanently in the seabed sediments) and how long it will stay the sediments for, then we can know how much carbon they will absorb over time. This will help us predict how much atmospheric CO2 may be buried in our marine sediments over a certain timescale.

The rains and rough weather returned on Sunday, however I think most of us have our sea legs now!
 



Sunset on Saturday