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Abstract Particulate organic matter supports pelagic food webs, and the activity of these food webs attenuates the flux of carbon into the ocean interior. Understanding the extent to which microbial and metazoan heterotrophs influence particle dynamics is essential to describing the biological carbon pump and nutrient delivery to deep ecosystems. We present results of bulk and compound‐specific nitrogen stable isotope analyses and a Bayesian mixing model of zooplankton fecal pellets (FP), phytoplankton, and microbial detritus end‐members on size‐fractionated particulate organic matter from 10 depths in the upper 500 m of Monterey Bay, CA. Our results suggest three distinct zones of plankton‐particle interactions in Monterey Bay: primary production and grazing from 0 to 60 m, intense microbial reworking from 60 to 200 m, and inclusion into metazoan food webs below 200 m. Zooplankton FP signatures were found in a <20 μm particle size fraction, both at the approximate depth to which zooplankton migrate at night (∼25–60 m) and in the mesopelagic at the approximate depth to which zooplankton migrate during the day (∼200 m). This finding indicates that fecal pellets were rapidly disaggregated at the depth at which they were produced, which has implications for estimates of zooplankton FP contribution to carbon export and modeling efforts. In some water columns, much of zooplankton FP production may be disaggregated and entrained in the epipelagic zone, above the export depth. 

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Abstract One grand challenge for printed organic electronics is the development of a knowledge platform that describes how polymer semiconductors assemble from solution, which requires a unified picture of the complex interplay of polymer solubility, mass transport, nucleation and, e.g., vitrification. One crucial aspect, thereby, is aggregate formation, i.e., the development of electronic coupling between adjacent chain segments. Here, it is shown that the critical aggregation temperatures in solution (no solvent evaporation allowed) and during film formation (solvent evaporation occurring) are excellent pointers to i) establish reliable criteria for polymer assembly into desired aggregates, and ii) advance mechanistic understanding of the overall polymer assembly. Indeed, important insights are provided on why aggregation occurs via a 1‐ or 2‐step process depending on polymer solubility, deposition temperature and solvent evaporation rate; and the selection of deposition temperatures for specific scenarios (e.g., good vs bad solvent) is demystified. Collectively, it is demonstrated that relatively straightforward, concurrent in situ time‐resolved absorbance and photoluminescence spectroscopies to monitor aggregate formation lead to highly useful and broadly applicable criteria for processing functional plastics. In turn, improved control over their properties and device performance can be obtained toward manufacturing sensors, energy‐harvesting devices and, e.g., bioelectronics systems at high yield. 

Abstract Paleontological reconstructions of plankton community structure during warm periods of the Cenozoic (last 66 million years) reveal that deep-dwelling ‘twilight zone’ (200–1000 m) plankton were less abundant and diverse, and lived much closer to the surface, than in colder, more recent climates. We suggest that this is a consequence of temperature’s role in controlling the rate that sinking organic matter is broken down and metabolized by bacteria, a process that occurs faster at warmer temperatures. In a warmer ocean, a smaller fraction of organic matter reaches the ocean interior, affecting food supply and dissolved oxygen availability at depth. Using an Earth system model that has been evaluated against paleo observations, we illustrate how anthropogenic warming may impact future carbon cycling and twilight zone ecology. Our findings suggest that significant changes are already underway, and without strong emissions mitigation, widespread ecological disruption in the twilight zone is likely by 2100, with effects spanning millennia thereafter. 

We demonstrate that Cherenkov radiation can be manipulated in terms of operation frequency, bandwidth, and efficiency by simultaneously controlling the properties of drifting electrons and the photonic states supported by their surrounding media. We analytically show that the radiation rate strongly depends on the momentum of the excited photonic state, in terms of magnitude, frequency dispersion, and its variation vs the properties of the drifting carriers. This approach is applied to design and realize miniaturized, broadband, tunable, and efficient terahertz and far-infrared sources by manipulating and boosting the coupling between drifting electrons and engineered hyperbolic modes in graphene-based nanostructures. The broadband, dispersive, and confined nature of hyperbolic modes relax momentum matching issues, avoid using electron beams, and drastically enhance the radiation rate—allowing that over 90% of drifting electrons emit photons. Our findings open an exciting paradigm for the development of solid-state terahertz and infrared sources. 

North Atlantic Deep Water (NADW), the return flow component of the Atlantic Meridional Overturning Circulation (AMOC), is a major inter-hemispheric ocean water mass with strong climate effects but the evolution of its source components on million-year timescales is poorly known. Today, two major NADW components that flow southward over volcanic ridges to the east and west of Iceland are associated with distinct contourite drift systems that are forming off the coast of Greenland and on the eastern flank of the Reykjanes (mid-Atlantic) Ridge. Here we provide direct records of the early history of this drift sedimentation based on cores collected during International Ocean Discovery Programme (IODP) Expeditions 395C and 395. We find rapid acceleration of drift deposition linked to the eastern component of NADW, known as Iceland–Scotland Overflow Water at 3.6 million years ago (Ma). In contrast, the Denmark Strait Overflow Water feeding the western Eirik Drift has been persistent since the Late Miocene. These observations constrain the long-term evolution of the two NADW components, revealing their contrasting independent histories and allowing their links with climatic events such as Northern Hemisphere cooling at 3.6 Ma, to be assessed. 

We propose engineering optical traps over plasmonic surfaces and precisely controlling the trap position with an external bias by inducing in-plane nonreciprocity on the surface. The platform employs an incident Gaussian beam to polarize targeted nanoparticles, and exploits the interplay between nonreciprocal and spin-orbit lateral recoil forces to construct stable optical traps and manipulate their position within the surface. To model this process, we develop a theoretical framework based on the Lorentz force combined with nonreciprocal Green’s functions and apply it to calculate the trapping potential. Rooted on this formalism, we explore the exciting possibilities offered by graphene to engineer stable optical traps using low-power laser beams in the mid-IR and to manipulate the trap position in a continuous manner by applying a longitudinal drift bias. Nonreciprocal metasurfaces may open new possibilities to trap, assemble and manipulate nanoparticles and overcome many challenges faced by conventional optical tweezers while dealing with nanoscale objects.