A survey of Antarctic waters along the East Scotia Ridge in the Southern Ocean reveals a new vent biogeographic province among previously uncharacterized deep-sea hydrothermal vent communities.

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10Eutrophication is a globally significant challenge facing aquatic ecosystems, associated with human 11 induced enrichment of these ecosystems with nitrogen (N) and phosphorus (P). However, the limited 12 availability of inherent labels for P and N has constrained understanding of the triggers for 13 eutrophication in natural ecosystems and appropriate targeting of management responses. This paper 14 proposes and evaluates a new multi-stable isotope framework that offers inherent labels to track 15 biogeochemical reactions governing both P and N in natural ecosystems. importance of abiotic and metabolic processes for the in-river fate of N and P are also explored 27 through the stable isotope framework. Microbial uptake of ammonium to meet metabolic demand for 28 N is suggested by substantial enrichment of δ 15 N NH4 (by 10.2‰ over a 100m reach) under summer 29 low flow conditions. Whilst the concentration of both nitrate and phosphate decreased substantially 30 along the same reach, the stable isotope composition of these ions did not vary significantly, 31indicating that concentration changes are likely driven by abiotic processes of dilution or sorption. 32The in-river stable isotope composition and the concentration of P and N were also largely constant 33 downstream of the waste water treatment works, indicating that effluent-derived nutrients were not 34 strongly coupled to metabolism along this in-river transect. Combined with in-situ and laboratory 35 hydrochemical data, we believe that a multi-stable isotope framework presents a powerful approach 36 for understanding and managing eutrophication in natural aquatic ecosystems. 37 38

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The first molecular-based studies of microbes in snow and on glaciers have only recently been performed on the vast Greenland Ice Sheet (GrIS). Aeolian microbial seeding is hypothesized to impact on glacier surface community compositions. Localized melting of glacier debris (cryoconite) into the surface ice forms cryoconite holes, which are considered ‘hot spots’ for microbial activity on glaciers. To date, few studies have attempted to assess the origin and evolution of cryoconite and cryoconite hole communities throughout a melt season. In this study, a range of experimental approaches was used for the first time to study the inputs, temporal and structural transformations of GrIS microbial communities over the course of a whole ablation season. Small amounts of aeolian (wind and snow) microbes were potentially seeding the stable communities that were already present on the glacier (composed mainly of Proteobacteria, Cyanobacteria, and Actinobacteria). However, the dominant bacterial taxa in the aeolian samples (Firmicutes) did not establish themselves in local glacier surface communities. Cryoconite and cryoconite hole community composition remained stable throughout the ablation season following the fast community turnover, which accompanied the initial snow melt. The presence of stable communities in cryoconite and cryoconite holes on the GrIS will allow future studies to assess glacier surface microbial diversity at individual study sites from sampling intervals of short duration only. Aeolian inputs also had significantly different organic δ13C values (-28.0 to -27.0‰) from the glacier surface values (-25.7 to -23.6‰), indicating that in situ microbial processes are important in fixing new organic matter and transforming aeolian organic carbon. The continuous productivity of stable communities over one melt season makes them important contributors to biogeochemical nutrient cycling on glaciers.

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A new tool was developed for large volume sampling to facilitate marine microbiology and biogeochemical studies. It was developed for remotely operated vehicle and hydrocast deployments, and allows for rapid collection of multiple sample types from the water column and dynamic, variable environments such as rising hydrothermal plumes. It was used successfully during a cruise to the hydrothermal vent systems of the Mid-Cayman Rise. The Suspended Particulate Rosette V2 large volume multi-sampling system allows for the collection of 14 sample sets per deployment. Each sample set can include filtered material, whole (unfiltered) water, and filtrate. Suspended particulate can be collected on filters up to 142 mm in diameter and pore sizes down to 0.2 μm. Filtration is typically at flowrates of 2 L min-1. For particulate material, filtered volume is constrained only by sampling time and filter capacity, with all sample volumes recorded by digital flowmeter. The suspended particulate filter holders can be filled with preservative and sealed immediately after sample collection. Up to 2 L of whole water, filtrate, or a combination of the two, can be collected as part of each sample set. The system is constructed of plastics with titanium fasteners and nickel alloy spring loaded seals. There are no ferrous alloys in the sampling system. Individual sample lines are prefilled with filtered, deionized water prior to deployment and remain sealed unless a sample is actively being collected. This system is intended to facilitate studies concerning the relationship between marine microbiology and ocean biogeochemistry.