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Blog: Plankton blooms and clouds - what's the link? - 11 March

Today we found NIWA’s Andrew Marriner hard at work in the Ocean-Atmosphere Container Lab and asked him to explain his work onboard. Andrew is researching gradients of the dissolved gas dimethylsulphide (DMS) in the water column and its concentrations in the surface layer of the sea.

Andrew Marriner, NIWA, at work in the Ocean-Atmosphere Container Lab. Andrew is responsible for taking daily discrete water samples from the CTDs and constant samples from the underway seawater supply to run through a complicated-looking series of lab equipment.

[Photo: Sadie Mills, NIWA]

Andrew Marriner, NIWA all kitted out for the Antarctic conditions on the trawl deck.


[Photo: Sadie Mills, NIWA]

Andrew Marriner, NIWA adding sodium hydroxide pellets to water samples from the CTD to measure total DMS.


[Photo: Sadie Mills, NIWA]

The fields of marine microbial research and atmospheric science are closely linked here. DMS forms when a compound called dimethylsulphonioproprionate (DMSP), which is produced by some types of phytoplankton, breaks down. So, high levels of DMS in the water can indicate that there has been a large phytoplankton bloom in the area. What is intriguing though, is that the DMS escapes into the atmosphere where it can influence cloud formation.

This unit bubbles nitrogen gas into the seawater samples, either from the underway system or CTD samples, and extracts volatile gases, such as dimethylsulphide.

[Photo Sadie Mills, NIWA]

As we explained in an earlier blog DMS is one of the tiny aerosol particles present in the atmosphere on which water can condense to form clouds – cloud condensation nucleii or CCN. Over the oceans, where other forms of CCN are relatively sparse, DMS can occur in high concentrations and thus might have a strong influence on cloud formation. As oceanic cloud formation is an important and poorly-understood process in climate models, the links between the what our biologists study in the ocean and our atmospheric scientists study above it are stronger than you might have thought.

Finally, the amount of dimethylsulphide (DMS) present in the samples plots onto the screen.

Sadie Mills, NIWA

This freezing unit traps the DMS gas at -20°C.

Sadie Mills, NIWA