Low-carbon sampling of high-carbon plankton across the Atlantic Ocean

  • Heath, M. (Speaker)
  • Malene Clemmensen (Contributor)
  • Andrew Watson (Contributor)
  • Michael St John (Contributor)

Activity: Talk or presentation typesOral presentation


During a trans-Atlantic voyage of the 12m sailing vessel Storm Svale in May-July 2023 we collected daily plankton samples with a towed bongo net, and recorded the catch composition photographically at sea. Here we describe the distribution of a relatively little studied group of organisms – aragonite-secreting pteropods – which potentially form an important part of the global carbon sequestration story [1].

The voyage began in Saint Martin in the Leeward Islands, Caribbean, on 25 May and ended in Plymouth, UK, on 14 July after 40 days at sea plus a stop in the Azores. The passage relied almost entirely on sail and solar power, consuming only around 40 litres of diesel for occasional propulsion and 12 kg of liquefied butane for cooking. Each night at around local midnight (± 1 hour, weather permitting), we hand-deployed a 17 cm diameter bongo net (200 micron mesh) to around 5 m depth and towed for 30 minutes. The catch was examined within 1 hour and photographed at a range of magnifications up to 1000x.

Here we report on the distribution of the straight-shelled pteropods Cuvierina sp. (1.0-1.5cm length), and the smaller Styliola and Creseis sp., although coiled-shelled Heliconoides sp and Limacina sp. were also present in large numbers at some locations [2].

Along the 4000 nm length of the longitudinal Atlantic track, the area west of the Azores on the mid-Atlantic Ridge (30°-37°W) was a hot-spot of these pteropod species. Surface water temperatures in this area were 20-21°C, and the sampling also showed a high biomass of crustacean plankton. However, high crustacean biomass elsewhere along the track (e.g. the approaches to the European shelf) was not associated with the presence of pteropods.

Recent research shows that the carbonate shells of coccolithophores and perhaps the smaller, lightly calcified pteropods, can dissolve in the photic zone and hence their role in carbon sequestration may be less than previously thought [3]. However, the larger, more heavily calcified species such as Cuvierina sp. are an abundant feature of the sedimentary fossil record in some regions, suggesting that their shells may survive dissolution and contribute to the carbon flux to the seafloor. Nevertheless, in the current rising CO2 climate, they are also vulnerable to ocean acidification.
Period5 Dec 2023
Event titleMASTS Annual Science meeting 2023
Event typeConference
LocationGlasgow, United KingdomShow on map
Degree of RecognitionNational


  • Atlantic Ocean
  • carbon
  • calcification
  • pteropods