An international team of scientists spent a week in Algoa Bay collecting samples from the seabed as part of a ground-breaking new project to help put the skids on climate change.
The premise of the fascinating new Convex Seascape Survey is that global warming is driving instability, and our terrestrial world is becoming increasingly fragile, with wildfires releasing dangerously high volumes of carbon into the atmosphere.
As this happens, the relative stability of the ocean’s carbon cycle is becoming increasingly important.
The floor of the sea anchors this stability by locking in organic carbon in the form of plankton carcasses and sea life faeces.
Instead of releasing carbon into the atmosphere, the organic debris drifts down into the depths in a kind of “marine snow” and accumulates on the seabed.
The remains of larger marine animals also contribute to this ancient injection of organic carbon.
Driven by carbon emissions, climate change would be much worse if the seabed was not playing such an important stabilising role.
So, according to the scientists, the factors that are damaging it need to be identified and stopped.
The spots where the best carbon anchoring is happening also need to be protected to boost this process, and hopefully deal climate change a blow.
The Convex survey is a groundbreaking five-year research initiative focused on this twin goal.
It is spearheaded by three UK-based entities, the Blue Marine Foundation, Exeter University and Convex Insurance, which partner with different local organisations at each site they visit.
The team has already explored sites off Scotland and New Zealand and has now come to Algoa Bay and linked up with Nelson Mandela University.
Speaking to The Herald on the research boat last week, Exeter University’s Dr Ben Harris said Algoa Bay was the perfect site for the project.
This was because it included an intricate mix of rich marine life and a range of geological factors and human activity including three inflowing rivers, two harbours, trawling, dredging and pollution issues.
The question was how, if at all, these different factors were affecting the sea floor, either improving its carbon absorption or “sequestration” capacity, or diminishing it by disturbing the sediment and releasing the remineralised carbon up through the water into the atmosphere.
Harris said marine zones with strong carbon sequestration capacity could provide a powerful new reason for properly policing marine protected areas, which was all too often not being done, and for creating more MPAs.
“Good carbon sequestration capability as a reason to protect a marine zone provides a possibly more compelling incentive than protecting an obscure species or even countering over-fishing because the role players co-ordinating the move could earn carbon credits.”
The carbon credit system allows companies and countries to offset their own carbon emissions by funding projects that reduce or remove emissions elsewhere.
Gail Fordham of the Blue Marine Foundation said they had used a vibrocore to take the first samples in Algoa Bay.
Once lowered to the sea floor, the machine used vibration to drive down a large tube, capturing a metre-deep sausage of sediment.
“Back in the SA Environmental Observation Network lab at NMU, this sausage will be sliced into patties, with each patty revealing a different moment in time, which will be pinpointed using carbon dating.
“We will then match that against its carbon content, and what we know was happening at that time, in terms of particular human or environmental activity.”
She said different creatures living on the seabed could affect the carbon cycle in their area, depending on their size and behaviour.
“It seems crazy to think these little invertebrates could do that but, when you consider how vast the sea floor is and how many of these creatures there are, it makes sense.
“We think burrowing animals could be benefiting the system by helping to bury marine snow.
“But their burrowing might also be disturbing carbon. It’s one of the things we hope to find out.”
Besides the CTD (measuring salinity, temperature and depth), the main machine deployed on Wednesday was the ingenious “grab sampler”.
With Ferdi Jacobs of the SA Institute of Aquatic Biology manning the winch, it was lowered to the sea floor for six grabs at each site, flipping open, scooping up 6-7l of sediment and snapping closed to be winched up and swung onto deck.
Assisted at various times through the day by different members of the team on each grab, the University of Exeter’s Dr Sabrina Sykes removed whatever little feathery, spiny and squelchy critters there were on top for separate attention, then scooped up and labelled two bottles of sediment.
She showed how the bottles were carefully labelled, noting all the particulars of the site.
“It’s important to keep track or else it all mushes into one.”
NMU’s Dr Frederick Mokumo spent most of the trip poring over sieves full of starfish, sponges, brittle stars, feather stars and jointed worms in a confusing jumble of sand and other debris.
He used a pair of tweezers to extract each of the little animals, dividing them according to their general behaviour and how they engaged with the seabed.
“Sometimes these worms look inanimate because they have built a communal cone from sand and other debris to protect themselves.
“In that case, I extract the whole lot and we do the further sorting in the lab, but we try do as much sorting as possible on the boat.
“Most important will be to link species to site and to understand how they function and how that is affecting the carbon content of that part of the seabed.
“But at the end we will also check the carbon content of each animal itself by subtracting its ashed weight from its actual weight.”
In terms of NMU’s two-step ethical invertebrate collection policy, each creature was placed into a weak solution of ethanol to stun it, before being euthanised and preserved in a strong solution of ethanol.
Harris said one study had found that the volume of carbon released into the atmosphere because of dredging was greater than the volume from the aviation industry.
“There has been some pushback against this finding, but it is certainly significant, which is why we are considering it here.”
He said sewage pollution, a common feature in Algoa Bay as a result of the Nelson Mandela Bay municipality’s shaky wastewater management system, was another negative.
“It might even push up the organic carbon for a while because it’s introducing extra nutrients — but in the long run it will kill marine life and without that life there can be no organic carbon.
“Further, even as we zero in on climate change and the vital issue of reducing atmospheric carbon, we have to remember that biodiversity is also fundamental, and if we lose that, we lose everything.”
Artist Naomi Hart spent her time on the trip doing lightning-fast sketches of the team members as they went about their different tasks, and then some close-ups of the machines and the creatures brought to the surface.
She said she hoped to capture the reality of field science.
“I hope, by seeing it through that lens, people who might not otherwise be interested in climate change will become inspired.”
Fordham said the hope was that the project would make a difference globally.
“However, the more immediate benefits will likely be local.
“Our open-data approach means all our findings will be available, and they can be used to help the authorities at the different sites we visit to implement marine spatial planning, and thereby drive a sustainable ocean economy.”
The Herald
