PRIMUS members Javier Arístegui, Xosé A. Álvarez-Salgado and Nauzet Hernández-Hernández from ULPGC and IIM-CSIC, were recently collecting in-situ primary production and biogeochemical data in the Canary Current EBUS, during an expedition led by Prof. Arístegui on board of RV Sarmiento de Gamboa (27th July to 27th August 2022). The cruise was part of PRIMUS-related project e-IMPACT aimed at exploring the “secrets” and life history of mesoscale eddies formed in the Canary Islands, and how they influence primary production and the biogeochemical properties of the Canary Current EBUS.
RV Sarmiento de Gamboa is a multidisciplinary research vessel fully equipped to study global ocean circulation, marine biodiversity, fishery resources and issues related to climate change. The ship belongs to the CSIC, it is based in Vigo, and managed by the Marine Technology Unit (UTM) of the CSIC.
The e-IMPACT-1 scientific team which has recently sailed on board of RV Sarmiento de Gamboa.
Three eddies – two cyclonic, and one anticyclonic - named Nublo, Anaga and Garajonay were tracked and measured in their first stages of development, using remotely sensed sea surface data (SST) of moderate (VIIRS Sentinel 3 SLSTR), and high-resolution Landsat 8 and 9). Satellite data were used in synergy with Copernicus products (aviso and IBI model), as well as intensive surveys with SeaSoar, ADCP and XBTs, complemented with a glider survey. Above, you can see their evolution during 2-9 August. Orange-red colors indicate warmer SSTs while green-bluish colors indicate colder SSTs.
The expedition allowed a fine-scale resolution in-situ sampling of primary production data (6-miles separation) from 14 stations along two sections crossing eddies Nublo, Anaga and Garajonay, using photosynthesis - irradiance curves (P-I curves) by means of 14C uptake along a light gradient at two water depths – surface and deep chlorophyll maximum (DCM). The primary production data will be a valuable contribution to the aims of PRIMUS.
Above is the setup for obtained the 14C-uptake P-I curves which are used to measure marine primary production.
Additional measurements using a LabSTAF active fluorometer (Chelsea co.) were also used to generate Fluorescence Light Curves (FLCs) at the same stations, but at 5-6 water depths in the euphotic zone. The actinic light source integrated within LabSTAF allows for assessment of the photon irradiance dependence of phytoplankton primary production through the application of FLCs. These comprise an automated set of Single Turnover Active Fluorometry measurements, made at several photon irradiance levels between darkness and saturating light, providing information equivalent to the traditional carbon fixation-based P-I curves.
LabSTAF equipment used to generate the Fluorescence Light Curves. Preliminary on board observations indicate a quite good agreement between the P-I curves obtained from this method, and data from the C14 uptake at 5-6 depths.
For more information about the expedition and Project e-IMPACT (“Biogeochemical impact of mesoscale and sub-mesoscale processes along the life history of cyclonic and anticyclonic eddies: plankton variability and productivity”) check the cruise blog here.