|Narrative summary of dataset||The provided microplastic dataset was generated during The Ocean Race Europe in May-June 2021. The samples were collected onboard two 65’ one-design yachts known as VolvoOcean65, called AmberSail2 and AkzoNobel Ocean Racing in the Baltic Sea, North Atlantic Ocean and Mediterranean Sea.
The instruments used for underway measurements were the same as used in Tanuha et al., 2020. The system consists of a specially built OceanPack RACE manufactured by SubCtech GmbH in Kiel, which was connected to a microplastic filtration unit built by bbe Moldaenke GmbH. (Data submission https://www.emodnet-ingestion.eu/submissions/submissions_details.php?menu=39&tpd=232&step=0103_001volvo%20ocean%20race).
The mixed-layer surface water (~1.5 m depending on the heel of the yachts) was sampled in the Baltic Sea, North Atlantic Ocean and Mediterranean Sea. The laboratory analysis of collected samples was undertaken by GEOMAR (Kiel), under the supervision of Aaron Beck and Toste Tanuha.
The data variables includes GPS positions, time, temperature, salinity, flow rates and durations, sample ID, measured microplastic fiber, fragments and total concentration in [particles/m³]. Respetive concentrations of fiber and fragments are also provided for different colors: blue,red, orange, pink, yellow, green, black, clear, purple, grey, brown.
Acknowledgements go to 11th Hour, teams AmberSail2 (Tomas Ivanauskas,Regimantas Buozius) and AkzoNobel (Liz Wardley), TheOcean Race Sustainability and Science programmes, bbe Moldaenke GmbH and SubCtech GmbH.
|Summary of processing methodology||During the race and delivery periods, a total of 36 microplastic samples were taken by filtering seawater through two stainless steel filters with 100 and 500 µm meshes. Only the 500 µm are analysed in this dataset. The samples were typically taken 0.5–1.5 meter below the sea surface, although this is dependent on sea-state and heel, being representative of the mixed-layer microplastic concentration, rather than the microplastics floating on the surface. The water supply was from one of two inlets located at each side of the yachts bottom; the leeward intake was always used to avoid air contamination in the system. Some water for the yacht’s water maker supply was diverted to the filtration system and an analytical system (OceanPack™Race by SubCtech GmbH) that also measured salinity, temperature and partial pressure of carbon dioxide (pCO2). The OceanPack continuously logged the position during sampling, as well as the volume of sampled water from a flowmeter located at the filtration unit. The filters were exchanged at variable intervals during the delivery and race periods due to competitive constraints which resulted in a range of sampling-times and volumes. The average time between filter change was ~12h (min 2h, max 22h) and the sampled volume for each sample averaged at 0.37 m³ (min 0.05m³ max 0.7m³).
After sampling, these filters were securely packed and transported to the lab in Kiel to be measured for their microplastic concentration after sampling.
In a laboratory under filtered air (DB1000, HEPA filtration, Q = 950 m³/h, Mo¨cklinghoff Lufttechnik; Bergmann et al., 2017), each filter was transferred to a glass beaker and the inside of the bag rinsed into the beaker with 0.2 µm-filtered ultrapure water (18.2 MOhm-cm; MilliQ, Millipore). The filter was sonicated in an ultrasonic bath for 15 minutes to remove particles, and the filter removed from the beaker and rinsed. The remaining suspension was then filtered onto a glass-fiber filter (GF/F; Whatman) under gentle vacuum, and filters air-dried and stored in glass petri dishes. Plastic fragments and fibers were identified visually under magnification by personnel trained on reference particles down to 20 µm in size. Plastic items were transferred to glass mounting slides for imaging, size measurement, and polymer identification by near-infrared hyperspectral imaging (Beck et al., in prep). This method has a practical size detection limit of about 100 µm, but reliable measurement is limited by the narrowest particle dimension. Unfortunately, the particles found in the current study were too small to give clearly identifiable spectra for polymer identification. Work is ongoing to improve detection limits for small particles. Note the presented analysis focuses on the 500 um filter data as particles on the 100 um filter are too small for the hyperspectral camera.
The methods employed allowed separating microplastic fibers and fragments which is a new feature with respect to the last sampling campaign and Raman measurements (Tanuha et al., 2020).
Tanhua T, Gutekunst SB, Biastoch A (2020) A near-synoptic survey of ocean microplastic concentration along an around-the-world sailing race. PLoS ONE 15(12): e0243203. https://doi.org/10.1371/journal.pone.0243203. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0243203
Beck, A.J., M. Kaandorp, T. Hamm, B. Bogner, M. Lenz, E. Van Sebille, E.P. Acterberg. Rapid shipboard measurement of net-collected marine microplastics using near-infrared hyperspectral imaging, in prep.
Bergmann, M., Wirzberger, V., Krumpen, T., Lorenz, C., Primpke, S., Tekman, M. B., & Gerdts, G. (2017). High quantities of microplastic in Arctic deep-sea sediments from the HAUSGARTEN observatory. Environmental science & technology, 51(19), 11000-11010.|