The extraction of microplastics from organic-rich freshwater samples is challenging and limited information is available in the literature. This study aims at developing efficient methods for water volume reduction and organic matter removal in freshwater samples, while focusing on the reduction of the economic and environmental costs, maintaining microplastics integrity and avoiding contamination. For the water volume reduction approach, centrifuging freshwater samples (water, sediment, algae, leaves, driftwood, fish tissue) at different speeds (3500, 6000 rpm) and times (5, 10 min) showed that 3500 rpm for 5 min was efficient to settle the mineral and organic material, while preserving the polymers and showing high microplastic recovering rates (93 ± 6%). These recovery rates were significantly higher than the traditional sieving approach (77 ± 22%). The posterior minimal consumption of reagents resulting from the reduction of water volume helped to reduce the economic and environmental costs of the devised methodology, becoming more aligned with green chemistry principles. For biogenic organic matter removal, four digestion solutions were tested on freshwater samples, namely 10% potassium hydroxide, Fenton reagent (30% H₂O₂ + Fe(II)), 7% and 10% sodium hypochlorite (NaClO), under 3 periods of time (1, 6 and 15 h), at 50 °C. Both 7% and 10% NaClO showed the highest rates of organic matter removal (86 ± 1% and 90 ± 1%, respectively), after 6 h at 50 °C. Exposure of virgin and aged polymers (polyethylene, polypropylene, polystyrene, polyvinyl chloride, nylon, polyethylene terephthalate) to NaClO showed no weight, visual, surface structure, Fourier transform infrared spectra and carbonyl index changes, except for nylon, although not to an extent that affected its identification. This method resulted in high recovery rates of polymers (92 ± 6%). Thus, 7% NaClO at 50 °C for 6 h (or overnight) may be efficiently used for microplastic analysis in organic-rich freshwater samples.

Competition with fisheries and incidental capture in fishing gear are the major current threats for seabirds at sea. Fishing is a traditional activity in Portugal and is mainly composed of a great number of small vessels. Given the lack of knowledge on effects of the Portuguese fishing fleet on seabird populations, bycatch was assessed in mainland coastal waters for 2010–2012. Interviews and on-board data were divided into 5 strata, according to fishing gear: Bottom trawling, Bottom longline, Purse seine, Beach seine, Polyvalent (≥12 m) and Polyvalent (<12 m). Polyvalent included Setnets, Traps and Demersal longlines. Overall, 68 birds were recorded to be bycaught. The average catch per unit effort (CPUE) was 0.05 birds per fishing event. Polyvalent (<12 m), Polyvalent (≥12 m) and Purse seiners had the biggest seabird bycatch rates, with 0.5 (CPUE=0.1), 0.11 (CPUE=0.05) and 0.2 (CPUE=0.11) birds per trip, respectively. Within Polyvalent gear, Setnets captured the largest diversity of seabird species (CPUE=0.06), while Demersal longline had the highest CPUE (0.86). Northern gannet was the most common bycaught species. Although more observation effort is required, our results suggest that substantial numbers of Balearic shearwater might be bycaught annually, mainly in Purse seine and Setnets