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Dungeness crabs ( Metacarcinus magister ) are ecologically and economically important in the coastal Northeast Pacific, yet relatively little is currently known about their feeding behaviour in the wild or their natural diet. Trophic biomarkers, such as fatty acids (FA), can be used to reveal trophic interactions. We used two feeding experiments to assess differences in FA composition of juvenile crabs fed different known foods to evaluate how they modify and integrate dietary FA into their own tissues and determine whether crab FA reflect diet changes over a six-week period. These experimental results were then compared with the FA signatures of wild caught juvenile crab with undetermined diets. We found that juvenile Dungeness crabs fed different foods assimilated dietary FA into their tissues and were distinct in their FA signatures when analysed with multivariate statistics. Experimentally fed juvenile crabs contained greater proportions of the most abundant long-chain polyunsaturated fatty acids (LCPUFA, >C20) than their foods. Crabs fed foods lacking in LCPUFA, particularly DHA (22:6 ω 3, docosahexaenoic acid), did not survive or grew slower than crabs fed other foods. This suggests that LCPUFA are physiologically important for this species and indicates biosynthesis of these FA does not occur or is not sufficient to meet their needs. This article is part of the theme issue ‘The next horizons for lipids as ‘trophic biomarkers’: evidence and significance of consumer modification of dietary fatty acids’. 

To investigate the timing and intensity of winter spawning by coastal invertebrates, we enumerated embryos in plankton samples collected in daily time series from January to March of 2014 (79 d), 2015 (73 d), and 2016 (74 d). Samples were collected near the mouth of the Coos Bay estuary in Oregon. We enumerated several hundred different morphologically distinct types of embryos and larvae representing at least five phyla. Forty‐three embryo types were abundant enough (abundance > 500 over the time series) to enable statistical analysis. Twenty of these types were identified using genetic barcoding of which there were four nemerteans, four gastropods, four chitons, five polychaetes, and two echinoderms. In winter 2014, hydrographic conditions were similar to average historical values. Conditions in 2015 and 2016 were characterized by marine heat waves (MHWs). In 2015, the “warm blob”—anomalously warm water in the Northeastern Pacific—affected conditions and in 2016, there was a strong El Niño. In 2015 and 2016, winter spawning intensity was orders of magnitude lower than in 2014 and many taxa failed to spawn (11 and 24 in 2015 and 2016, respectively); spawning appears to have been adversely impacted by the MHWs. The MHW of 2015 has been attributed to anthropogenic global climate change while the 2016 El Niño may have been strengthened by climate change. The frequency, intensity, and duration of MHW are projected to increase dramatically with global warming, which may adversely affect reproduction and recruitment by numerous marine taxa.

 

Marine plastic debris floating on the ocean surface is a major environmental problem. However, its distribution in the ocean is poorly mapped, and most of the plastic waste estimated to have entered the ocean from land is unaccounted for. Better understanding of how plastic debris is transported from coastal and marine sources is crucial to quantify and close the global inventory of marine plastics, which in turn represents critical information for mitigation or policy strategies. At the same time, plastic is a unique tracer that provides an opportunity to learn more about the physics and dynamics of our ocean across multiple scales, from the Ekman convergence in basin-scale gyres to individual waves in the surfzone. In this review, we comprehensively discuss what is known about the different processes that govern the transport of floating marine plastic debris in both the open ocean and the coastal zones, based on the published literature and referring to insights from neighbouring fields such as oil spill dispersion, marine safety recovery, plankton connectivity, and others. We discuss how measurements of marine plastics (bothin situand in the laboratory), remote sensing, and numerical simulations can elucidate these processes and their interactions across spatio-temporal scales.