Science communication

2018.10.11

Welcome to WEGAS!

No, that's not a typo. WEGAS is short for Water Equilibration Gas Analysis System, scientific analytical instruments that we took on board the recent research cruise

This is a repost of an article I wrote for the Baltic Sea Centre website.

In September, The Baltic Sea Centre’s research vessel Electra, traveled to Tvärminne Zoological Station for a sampling week as part of the Swedish-Finnish research collaboration, "Baltic Bridge".

This was the second multi-disciplinary research trip in the Finnish archipelago with scientists from several departments at both Stockholm University and University of Helsinki. The week was spent investigating a range of different geological, oceanographical and ecological factors of the area. One of the projects involved exploring the carbon cycling in the sea by studying the greenhouse gases methane and carbon dioxide.

Investigating the carbon cycle

Carbon dioxide in the sea is produced naturally, when fish and other marine life "breathe" and when bacteria break down organic matter, such as carbon-rich material formed by the decay of living things. Carbon dioxide in the air also dissolves in seawater, where it can remain as a dissolved gas or be taken up by algae.

Methane is produced in sediments when there is no oxygen. Even if oxygen is present in bottom waters and surface sediments, deeper sediments are oxygen-free. There are many types of micro-organisms that survive well under these conditions, including those that convert carbon dioxide and other carbon molecules into methane. Methane is about 30 times more potent than carbon dioxide as a greenhouse gas, so it is important to understand where methane production is occurring.

- Previous studies have focused on deep areas of the sea and we really don’t know how much carbon dioxide and methane are produced in shallow areas, says Dr. Xiaole Sun, researcher at the Baltic Sea Centre.

Generally, rates of carbon dioxide and methane increase with increasing organic matter. Coastal sediments contain more organic matter than deep sediments because of inputs from land, for instance from soils and leaves, and because there is more biological activity in shallow areas.

Research: it’s a gas! 

To study the carbon cycling in the sea, Dr. Xiaole Sun and Dr. Christoph Humborg used WEGAS (Water Equilibration Gas Analysis System), a state-of-the-art system, during this cruise. WEGAS can be run continuously while the ship is moving and take real-time measurements of the concentrations of the greenhouse gases carbon dioxide and methane in water and the air just above the water.

- What is great about WEGAS is that we get instant data, says cruise leader Dr. Christoph Humborg. Without WEGAS it would be impractical, if not impossible, to gather the same amount of data by manually collecting water and air samples that would then be analyzed in the laboratory. Also, the amount of data collected by WEGAS allows us to do powerful statistical analyses.

WEGASDr. Christoph Humborg is excited about the real-time data collected by WEGAS

At number of times and locations during the cruise, the concentration of carbon dioxide in the sea water was more than double the concentration in the air. The difference was even bigger for methane; in some places, the concentration in the water was more than 25 times greater than in the air. In these cases, the coastal waters are a source of carbon dioxide and methane to the air, because the gas molecules naturally move from areas of high concentration to low concentration.

- This is really exciting! Using WEGAS on Electra allows us to measure changes in carbon dioxide and methane concentrations in the water along different gradients, like from the open sea to the river mouth, says Dr. Xiaole Sun.

WEGASDr. Xiaole Sun monitors WEGAS during a recent research cruise aboard Electra

From land or sea?

WEGAS is also capable of measuring the isotopes of carbon in carbon dioxide. Isotopes are atoms of the same element that have different weights because they contain different numbers of neutrons. Most carbon atoms have 6 protons and 6 neutrons, and this is what we call 12C. About 1% of all carbon atoms are called 13C since they have 7 neutrons. The ratios between 13C and 12C in organic matter from land are different from the ratios of organic matter produced in the sea and can provide a clue about the sources of the carbon.

- Carbon isotopes can help us understand things like how much of the carbon dioxide in sea water was produced by the decay of organic matter that came from land, says Dr. Xiaole Sun. In this way, isotope data can reveal the influence of land on carbon cycling in shallow areas of the sea.

Bridging gaps in Baltic Sea research

The Baltic Bridge collaboration, a strategic partnership between Stockholm University’s Baltic Sea Centre and the University of Helsinki’s Tvärminne Zoological Station, aims at sharing expertise and infrastructure to advance Baltic Sea research. Something that Dr. Christoph Humborg finds essential in this carbon cycling project.

- There is a great opportunity to combine the carbon dioxide and methane data that we collected during this cruise with Tvärminne’s knowledge about the ecology of the area, says Dr. Christoph Humborg.

Michelle McCrackin

Limnologist
michelle.mccrackin@su.se