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Microplastics are now synonymous with human impacts on the environment and as a threat to marine organisms. Numerous taxa are at risk from microplastics including commercially valuable bivalves as seafood, which are also disproportionately important as biogenic reef-forming species that enhance biodiversity such that they are commonly protected under conservation actions. As a sessile filter-feeding organism, bivalves are highly susceptible to microplastic ingestion but despite their socio-economic and ecological importance, no research has been undertaken to assess how a reef 's structural arrangement might affect plastic ingestion. Here, using a series of flume experiments, we examined how change in spatial arrangement of the blue mussel, Mytilus edulis, interacts with different flow speeds to effect retention of microplastic over reef surfaces and ingestion risk by individual mussels. Our results show that clumped spatial arrangements reduce boundary layer velocities, and increase turbulence, boundary layer thickness and plastic retention over reef surfaces under faster flow conditions, increasing plastic ingestion by 3-fold. Our findings suggest that the structural arrangement and rugosity of natural reef structures may create natural sinks of anthropogenic pollution, and species like Mytilus that are also important species for human consumption, while disproportionately susceptible to microplastic pollution, may be useful bioindicators of microplastic pollution.

Estuaries receive large quantities of terrestrially derived organic material, yet the current view is that such terrestrial carbon is unimportant for temperate estuarine benthic trophic dynamics beyond microbial processing. This consensus, however, may derive from a lack of consideration in estuarine food web studies of taxa with evolutionary affinities to freshwater systems where these taxa process terrestrial detritus. Here, we used a multiple stable isotope approach (carbon, nitrogen and sulphur) in 3 similar estuarine systems to test whether taxa with high (oligochaetes), medium (amphipods) and low (marine polychaetes and other crustacean taxa) evolutionary associations with freshwater systems differed in their assimilation of carbon derived from contrasting detrital sources. Oligochaetes had isotopic signatures significantly different to those of other organisms, yet not significantly different from tree and ground plant signatures, demonstrating that they assimilate terrestrial carbon. In contrast, amphipods and marine taxa had isotope signatures that indicated a reliance on marine algal carbon, independent of where in the estuary they were sampled, suggesting that, unlike oligochaetes, these taxa do not have an inherent physiological ability to successfully assimilate terrestrial material. These findings indicate that terrestrial carbon can play a significant role in estuarine systems, with oligochaetes providing the metazoan entry route for this carbon source into food webs, and that evolutionary detritivore-detritus associations may influence present-day trophic dynamics within estuaries.KEY WORDS: Stable isotopes · Estuary · Carbon · Nitrogen · Sulphur · Food web · Oligochaeta · DetritusResale or republication not permitted without written consent of the publisher

We report the demonstration of a 2850 nm diode-pumped Ho, Pr co-doped fluoride fiber amplifier that delivers pulses with an average power of 2.45 W, 122 μJ energy, and 500 ps duration at a repetition rate of 20 kHz. To the best of our knowledge, the average power and pulse energy are the highest to be obtained from a sub-nanosecond fiber source operating in the 3 μm spectral region. The amplifier is seeded by an optical parametric generation source and is pumped around 915 nm using widely available InGaAs laser diodes.

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