Seabed samples from the coldest place on earth are now being studied in one of the world’s hottest.
In Saudi Arabia, scientists are examining layers of mud from the Antarctic seabed to determine how whale populations have thrived and declined in the past 500 years.
While the near-extinction of whales due to hunting in the 19th century is known, scientists from King Abdullah University of Science and Technology (Kaust) hope to prove that the healthy whale populations before then helped protect the atmosphere from carbon.
The samples arrived in Saudi Arabia in late September after being extracted by marine scientist Dr Carlos Preckler who led the fieldwork along the Antarctic Peninsula a year ago.
It is thought that whales stimulate the ocean’s ecosystem in their lifetime through their diet of krill and their love of diving into the deep sea before swimming up to the surface, which helps bring up nutrients.
Floating whale faeces also produce phytoplankton on the surface. When sunlight penetrates the water, the plankton photosynthesise and absorb carbon from the atmosphere.
When whales die, traces of their decomposed bodies containing carbon remain on the seabed as layers of mud are formed. The plankton they help produce – which the krill eat – also eventually sinks. That carbon is then stored, a phenomenon known as carbon sequestration, which prevents it from being released in the atmosphere.
“The first step will be to begin DNA extractions from the sediment samples,” Dr Preckler told The National. “The main objective is to detect and quantify whale DNA within the sediments, date the sediment layers, and estimate past primary production in the ocean. These analyses will help us assess the contribution of whales to the carbon cycle,” he said.
Dr Preckler and PhD candidate Diego Rivera had joined the Challenge-2 project aboard the Spanish research vessel BIO Hespérides to carry out extensive sampling and data analyses along the peninsula.
Scientists believe that the seabed’s ability to capture carbon could be used to cut global CO2 emissions by up to 6 per cent of the amount needed to cap the rise in global temperatures at 1.5ºC. But they need to prove it.
“The carbon sequestration of the ocean is hard to demonstrate. It’s mostly based on models and calculations (which) are not really a solid basis. We need empirical evidence,” said Prof Carlos Duarte, the award-winning marine ecologist who is leading the project at KAUST.
By analysing the carbon and DNA from mud cores that were extracted from the peninsula last spring, scientists hope to prove that a healthy whale population leads to more varied marine life and better carbon storage.
“We will be able to see if there is a smoking gun in Antarctica – as I believe there is,” he told The National.
The project is part of the Convex Seascape Survey, an international collaboration led by the University of Exeter and the Blue Marine Foundation which aims to study in detail how shallow seas can be used to store carbon.
Kaust, where Prof Duarte is based, was chosen for its DNA sequencing technologies and its specialism in analysing sediments. “The question we're asking is, what is the role that whales play in maintaining the capacity of the ocean to sequester carbon?” he said.
It took several months for the extracted cores to arrive in Saudi Arabia after the Kaust team’s four-week expedition in Antarctica.
To the naked eye, there is nothing remarkable about the mud samples that will be analysed at Kaust. But they contain a detailed history of the Southern Ocean.
A metre in depth of mud was extracted from the seabed for each of the cores. These were then divided during the expedition into small samples of just a few centimetres each, and packaged in tubes and bags.
These tiny sediment samples contain large amounts of information. Analysis of the mud's environmental DNA (e-DNA) can help quantify the tens of thousands of species living in the ocean.
Just 2cm of mud captures a year of insights about the animals and vegetation that lived at that time. The same samples will then be sent to a partner university in Australia to analyse the isotopes and establish their age.
The findings will be relevant to the Arabian Gulf, where there is a small population of humpback whales, and conservation efforts are under way to protect coral reefs, mangrove forests and another sea mammal: the dugong.
The sea there is shallow, and rapid urban development means there is a risk of carbon being released into the atmosphere if not properly managed. The cordoning off of areas reserved for oil exploitation meant some parts of the Gulf could be turned into conservation areas, Prof Duarte said.
“Industrial activities in the Gulf - rather than deteriorate the environment - protected it from massive exploitation of biological resources, because access to many of the areas where oil and gas operations are conducted was restricted” he said. “An outcome of that is that the Arabian Gulf has an untapped conservation value that is unique in the world,” he said.
There have been major changes to Antarctica since Prof Duarte's last expedition there in 1996, almost 30 years ago. Tourist trips to the continent have increased, he said, which has had an impact on what was once a “pristine ecosystem”.
The impact of climate change, he added, is visible. “The areas that were covered with ice are retreating. We see a lot more plant cover. A number of invasive species, including insects, are able to establish themselves there,” he said.
