Carbon capture by Antarctic seabeds

The ASCCC Project  has been funded by ACE (Antarctic Circumnavigation Expedition) to investigate, quantify and understand the role of polar and subpolar seabeds in the carbon cycle, particularly in response to climate change.  

Antarctic Circumnavigation Expedition route

Introduction

The continental shelf around Antarctica is vast, 1000 km wide in places and it is very important for carbon cycling (through very productive micro-algal diatom blooms) and for accumulation in terms of rich, abundant consumers – marine animals.  Although better known for very considerable stocks of zooplankton, such as krill, and higher predators, such as whales, most species known from polar waters live on the seabed (benthos SCAR-MarBIN link).  Recent Darwin Initiative funded cruises (Darwin Initiative newsletter) of the RRS James Clark Ross have shown that they play an important, and increasing, role in the carbon cycle.

Benthos commonly comprise echinoderms (sea stars, brittlestars, sea ucrhins), molluscs (clams & snails), corals, sponges, crustaceans, bryozoans (sea mosses) and many other animal types. They eat plankton (such as microscopic plants and animals).  Carbon is transported through the system by being fixed in photosynthesis by the tiny algae, which are eaten by benthos.  Many benthos are long lived so the skeletons in their structures build up large accumulations of CaCO₃, and crucially can bury this when these benthic animals die.

We call this ‘carbon immobilization’ (net annual carbon accumulation) and our main aim is to attempt to measure how much carbon is held per unit area of the seabed per year, and how this varies in time and space.  To date we have focussed mainly on one group of animals (bryozoans) because they are common, easy to identify, sessile (they don’t move) and have annual growth lines in their skeletons (like tree rings) – making them easier to age.  They can be important bioconstructors helping to form what The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) term Vulnerable Marine Ecosystems.  They have another advantage, in terms of ‘representing’ other benthos; their productivity:biomass rates are about median amongst the different benthic groups.

Carbon immobilization in the Antarctic

What do we do?

The majority of our work has taken place on board the RRS James Clark Ross, an ice-strengthened vessel operated by the British Antarctic Survey.

To date we have used a variety of apparatus: 1) a multibeam swath to map the physical characteristics of the seabed; 2) a bespoke camera lander that photographs precise areas of the seabed in high resolution; 3) an Agassiz trawl that collects specimens of larger benthic species; 4) an Epibenthic sledge which collects smaller benthic species and; 5) a CTD which collects information on the physical and chemical characteristics of the water column above the seabed.  Through a series of treatments (e.g. drying and ashing) of certain specimens, we can calculate the proportion of organic and inorganic carbon in each annual growth increment of each animal.  Image analysis of photographs allows us to calculate densities, so that we can estimate the total and yearly carbon in life on the seabed for each sample site.

What have we found so far?

We calculated the first estimate for carbon stocks and annual increments on West Antarctic continental shelves.  We also found that this value has nearly doubled in the last 25 years, coincident with sea ice losses.  So although rising CO₂ in the atmosphere has driven global warming, which has reduced Arctic and west Antarctic sea ice through warming air and/or sea temperatures, it has led to more carbon accumulation in animals on the seabed (thus less in the air).  Therefore it acts as a (negative) feedback working against climate change.

Antarctic seafloor life

Our second paper in 2015 found that carbon immobilization is much higher at certain locations in the Southern Ocean, particularly the South Orkney Islands.   This carbon sink hotspot was not due to animal density or longevity but caused by rapid growth fuelled by longer phytoplankton blooms (primary production).  We compared remotely (satellite) sensed and directly sampled sources (Antarctic research station collections), and both datasets correlated to duration (rather than amount) of phytoplankton food availability.   Climate forced sea-ice losses have allowed longer micro algal blooms and life on the sea floor is ‘cashing in’ on this longer banquet.  Good news for us, as these are becoming significant carbon sinks and negative feedbacks to climate change.

Problem

Subantarctic shelves, with less ice cover and more spring and autumn daylight, are likely to be more productive yet carbon accumulation and sequestration there remain unknown.

The overall goal of the ACE Project is to offer to international teams of distinguished scientists an outstanding and unique opportunity to study the marine and terrestrial environment of the sub-Antarctic ecosystem.  The research aims of this project are to:

• quantify total, and annual accumulation of, carbon held by benthos on all major shelf areas of the subAntarctic region
• investigate spatial and temporal changes in carbon accumulation across and within shelves and find environmental drivers for such changes
• identify which functional groups and key species are responsible for most carbon accumulation
• investigate conversion of accumulation to immobilization to sequestration through burial on death of benthos. Thus ultimately to estimate and report the size of the subAntarctic marine carbon budget to relevant stakeholders, eg CCAMLR.

Christoph Held
Christoph Held is a Senior Research Scientist at the Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, in Bremerhaven, Germany. He is the Head of Evolutionary Genetics research group in the Functional Ecology Section. He has conducted several major biodiversity surveys in the Antarctic and sub-Antarctic. Christoph specialises in phlylogeography and population genetics in Antarctic marine fauna, particularly crustaceans such as isopods.

Rachel Downey
Antarctic marine biogeographer with a research interest in the spatio-temporal impacts of environmental change on biological diversity. Project management skills gained in a number of global/large-scale scientific data collaborations. Interested in extending expertise to devise new methodologies and analysis to monitor current and predict future large-scale biodiversity change in our marine environment.

Camille Moreau

I am a French PhD student at the Université Libre de Bruxelles (ULB) and the Université de Bourgogne (Dijon) since October 2014 (supervisors: B. Danis & T. Saucède). My research at the Marine Biology Lab focuses on the diversity and connectivity of sea stars (Asteroidea) in the Southern Ocean. Biogeography and phylogeography will be the main domains used for this project.

Narissa Bax
Narissa is a benthic ecologist specialising in Antarctic and Patagonian coral reef habitats. Cold-water corals are sensitive to the potential threats of climate change, and are easily damaged by trawl fisheries. Antarctic corals often form dense, but isolated aggregations, and therefore their ability to recover from disturbance is limited. She has conducted research exploring the dispersal capabilites of corals in these regions, in order to determine how resilient they are to future threats.

Maria Paulsen
I am Danish but have been studying and working in Iceland and Norway the past 6 years. My main interest in this project is the meiofauna; the tiny animals (0.5–1 mm) that live between the sand grains. Looking though the microscope you quickly realise that it is not just mud, but that there is a vast diversity of Crustaceans (shrimp-like), Molluscs (mussel-like) and Polychaetes (worm-like) living within the sediment. Even though these animals are so tiny you can’t really see them with the naked eye, they are very abundant and of great importance for the consumption of carbon within in the sediment.

Bernabe Moreno
I am a Peruvian marine biologist, scientific diver & underwater cameraman. I currently work as a collaborative docent in laboratory sessions in the Marine Biology Laboratory at the Científica del Sur University where I’m also part of the Antarctic Project. My main interest is to study the effects of environmental variability on the functional ecology of macrozoobenthic communities. I’m using this approach both in Antarctic and Peruvian marine ecosystems. I’m an APECS Council Member and a member of an international multidisciplinary project called CIENPERU (Coastal Impacts of El Niño 2015–2016 in Peruvian marine ecosystem). As a diver, I’ve been registering important changes in biological assemblages in several offshore-and-coastal protected islands and altitude lakes.

Kirill Minin
I am a benthic ecologist, specialising in the integrative taxonomy of echinoids (sea urchins) around the world at the P.P. Shirshov Institute of Oceanology in Moscow, Russia. I have worked all over the world on a number of key projects, specialising particularly in deep-water and polar benthic environments. My current research is determining the biogeographic history of echinoids utilising morphological and molecular (genetic) taxonomy.

Oliver Hogg
I am a PhD student researching the use of multidisciplinary scientific approaches to increase our understanding of biogeographical and ecological patterns in benthic biodiversity; and assess how this knowledge can be used to inform on marine conservation and management strategies in the Southern Ocean. Oliver’s research integrates biological, geophysical, and ocean productivity data with regional oceanographic models and high-resolution seabed photography. This synthesis of multidisciplinary information enables large-scale biotopic characterisations to be made of marine benthic habitats. This allows us to study the respective influences of local-scale drivers verses large-scale abiotic gradients on biological communities, and model the distributions of potentially rare or endemic fauna and vulnerable marine ecosystems.

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