Seasonal oceanography of Hvalfjörður in southwest Iceland 2024-2025 - CTD data

The research project Seasonal oceanography of Hvalfjörður in southwest Iceland 2024-2025 was carried out by the Icelandic Marine and Freshwater Research Institute (MFRI) to obtain baseline data on physical and chemical oceanography and phytoplankton of the fjord over a full year. The geographic area of this research is bounded by the following coordinates: North: 64.5°, South: 64.2°, West: -21.3°, East: -22.1°. 
During twenty cruises conducted between April 2024 and April 2025 on three different vessels (Bjarni Sæmundsson HF30, Sæmundur fróði RE32 and Vonin KE10), samples were collected from ten to twelve fixed stations throughout the fjord for measurement of various parameters. Profiles of temperature, salinity, dissolved oxygen, pressure, fluorescence, turbidity and  Photosynthetic Active Radiation (PAR) were obtained by CTD. Discrete samples were collected at different depths  with Niskin bottles for the determination of salinity, dissolved oxygen, nitrate, silicate, phosphate, ammonium, pH, dissolved inorganic carbon, total alkalinity and chlorophyll a. At three of the fixed stations at two depths, samples were obtained for environmental DNA and sequenced using 18S rRNA V4 primers. Additionally, five moorings equipped with MicroCATs for obtaining timeseries for temperature, salinity, pressure, oxygen and pH, as well as ADCPs measuring current velocity, direction and acoustic backscatter were deployed at five different locations in the fjord. All data has been quality controlled. The full dataset has been split up into four subsets: CTD, discrete samples, e-DNA sequences and mooring data.
The data improves the basic understanding of the seasonality of the oceanography of the fjord at this point in time. In addition, the information can be used as input in model validations as well as enabling better assessment of the impact of various stressors, man-made or natural, on the environment in the fjord. 
This dataset is a part of a bigger dataset from the research that also contains CTD data, mooring data and eDNA data. This dataset includes all the measurements obtained from discrete samples collected during the project, including salinity, dissolved oxygen, nutrients (nitrate, silicate, phosphate, and ammonium), pH measured on the total scale at controlled temperature, dissolved inorganic carbon, total alkalinity, chlorophyll a, and Flowcam analyses. The data has been quality controlled and assigned quality flags following WOCE standards. Flag values are: 2 good data, 3 questionable data, 4 bad data, 6 replicates, and 9 missing data.