Abundance and characteristics of microfibers detected in sediment trap material from the deep subtropical North Atlantic Ocean.

Plastics and microplastics increasingly gain importance due to their perils and wide distribution in the marine environment. Microfibers account for the largest percentage of anthropogenic-induced microparticles, which inter alia, consist of plastic, and are found in deep-sea sediments. However, the sinking of fibers from the surface through the water column to the seafloor is still poorly understood. The present study investigates microfibers extracted from sediment trap samples, which were deployed in the North Atlantic Subtropical Gyre (NASG). The average result of eleven analyzed samples showed 913 microfibers per gram of collected particle flux material, with a predominant fiber length shorter than 1 mm (75.6%) and a distribution maximum between 0.2 and 0.4 mm. Further, the average number of microfibers found in this study was used to derive microfiber fluxes for the NASG based on the deployment time of the sediment trap. Extrapolating the computed flux of 94 microfibers m-2 day-1 to the entire NASG area would correspond to a total microfiber mass flux of 9800 t a-1 or 73 × 1013 microfibers a-1 of sinking microfibers through the water column. These findings offer an extended application of sediment traps to monitor microfiber fluxes, which reveals the opportunity to investigate the mechanism driving sinking of microfibers and microplastics into the deep open ocean.

A Multi-Pumping Flow System for In Situ Measurements of Dissolved Manganese in Aquatic Systems.

A METals In Situ analyzer (METIS) has been used to determine dissolved manganese (II) concentrations in the subhalocline waters of the Gotland Deep (central Baltic Sea). High-resolution in situ measurements of total dissolved Mn were obtained in near real-time by spectrophotometry using 1-(2-pyridylazo)-2-naphthol (PAN). PAN is a complexing agent of dissolved Mn and forms a wine-red complex with a maximum absorbance at a wavelength of 562 nm. Results are presented together with ancillary temperature, salinity, and dissolved O 2 data. Lab calibration of the analyzer was performed in a pressure testing tank. A detection limit of 77 nM was obtained. For validation purposes, discrete water samples were taken by using a pump-CTD system. Dissolved Mn in these samples was determined by an independent laboratory based method (inductively coupled plasma-optical emission spectrometry, ICP-OES). Mn measurements from both METIS and ICP-OES analysis were in good agreement. The results showed that the in situ analysis of dissolved Mn is a powerful technique reducing dependencies on heavy and expensive equipment (pump-CTD system, ICP-OES) and is also cost and time effective.