Distribution and abundance of surface water microlitter in the Baltic Sea: A comparison of two sampling methods.

ABSTRACT

Two methods for marine microlitter sampling were compared in the Gulf of Finland, northern Baltic Sea manta trawl (333µm) and a submersible pump (300 or 100µm). Concentrations of microlitter (microplastics, combustion particles, non-synthetic fibres) in the samples collected with both methods and filter sizes remained <10particlesm(-3). The pump with 100µm filter gave higher microlitter concentrations compared to manta trawl or pump with 300µm filter. Manta sampling covers larger areas, but is potentially subjected to contamination during sample processing and does not give precise volumetric values. Using a submerged pump allows method controls, use of different filter sizes and gives exact volumetric measures. Both devices need relatively calm weather for operation. The choice of the method in general depends on the aim of the study. For monitoring environmentally relevant size fractions of microlitter the use of 100µm or smaller mesh size is recommended for the Baltic Sea.