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Carbon export (from the epipelagic towards the mesopelagic zone) and sequestration (from the mesopelagic towards the bathypelagic zone) in the ocean are reviewed. Particulate organic carbon (POC) flux, and active flux due to migrant zooplankton and micronekton are shown from the epipelagic to the mesopelagic zone, and from the latter to the bathypelagic zone. Values towards the meso- and bathypelagic zones are compared in oligotrophic and productive systems. Zooplankton and prokaryote respiration in the meso- and bathypelagic zones of the ocean are also reviewed for oligotrophic and productive systems. Values were integrated over a depth layer and are given as the flux or respiration under one square meter (in g/m**2/a) between e.g. 100 m and 1000 m depth.

This submission consists of 40 eddy covariance datasets collected from six shallow sites in the Baltic Sea over an 18 month period. Hourly fluxes were extracted from the high-density data streams and were used to compute daily rates of benthic metabolism (gross primary production (GPP), respiration (R), and net ecosystem metabolism (NEM); in mmol O2 m-2 d-1). These were converted to C assuming an O2 : C of 1.0 for GPP and R. A description of the flux data processing protocol is given in the manuscript. These datasets were used to compute annual rates of GPP, R, and NEM at each habitat site. The annual rates were then used to investigate (i) phototrophic biomass turnover rates, by comparing the GPP rates with standing phototrophic biomass measurements, and (ii) the regional importance of benthic metabolism, by upscaling the annual rates to habitat distribution maps. This dataset includes all data on standing biomass and habitat extent. Attard et al. LO LettersDaily benthic metabolism rates, annual integrated rates, biomass turnover rates, and spatial upscaling estimates presented in Attard et al. LO LettersMetadata template_Attard et alMetadata template for Attard et al. LO Letters dataset

We report the results of an aquaria-based experiment testing the effects of suspended particles generated during potential mining activities, on a common habitat-building coral species in the Azores, Dentomuricea aff. meteor. Coral fragments were maintained in 10-L aquaria and exposed to three experimental treatments for a period of four weeks at the DeepSeaLab aquaria facilities (Okeanos-University of the Azores): (1) control conditions (no added sediments); (2) suspended polymetallic sulphide (PMS) particles; (3) suspended quartz particles. Seawater physical-chemical parameters were measured daily in each aquarium. Seawater salinity was measured with a S30 SevenEasy™ conductivity meter, pH and temperature with a glass electrode (Crison pH 25+), and oxygen with a Fibox4 (PreSens) with a Oxygen Dipping Probe DP-PSt3. Seawater samples for inorganic nutrient analyses were collected on times 0 (immediately before the start of the experiment), and once a week on days 6, 13, 20 and 27 of the experiment and determined using a colorimetric autoanalyzer Sanplus with segmented flow. Monitoring of aquaria: Monitoring of physical-chemical conditions in each experimental aquaria (2 replicate aquaria per treatment)

We report the results of an aquaria-based experiment testing the effects of suspended particles generated during potential mining activities, on a common habitat-building coral species in the Azores, Dentomuricea aff. meteor. Coral fragments were maintained in 10-L aquaria and exposed to three experimental treatments for a period of four weeks at the DeepSeaLab aquaria facilities (Okeanos-University of the Azores): (1) control conditions (no added sediments); (2) suspended polymetallic sulphide (PMS) particles; (3) suspended quartz particles. Trace elements (Co, Cu, Mn) released from the resuspension of PMS particles to the water column in each aquaria were determined using passive sampling (DGT® Research Ltd) coupled with inductively coupled plasma mass spectrometry (ICPMS). DGT-holders were deployed in all aquaria and replaced every week (days 6, 13, 20, 27). Metals in seawater: Measurements of metal content in seawater in the different experimental treatments

Coral gardens are considered to be hotspots of biodiversity and ecosystem functioning, due to the important structural and biogeochemical role of cold-water coral (CWC) species. Despite an increase in studies on deep reef-forming species, information on cold-water octocoral species is still very scarce. The present study focused on the feeding biology of two habitat-forming octocoral species typically encountered in seamounts in the Azores between 200 and 600m of depth: Dentomuricea aff. meteor and Viminella flagellum. We used an experimental approach aiming at determining the ability of the species to utilize different food sources including live phytoplankton (the diatom Chaetoceros calcitrans), Dissolved Organic Carbon (DOC) and live zooplankton (the rotifer Branchionus plicatilis). Food sources were isotopically enriched with tracers (13C, 15N) which allowed to trace the ingested food in different physiological processes, such as tissue incorporation, Dissolved Inorganic Carbon (DIC) respiration and excretion of Particulate Organic Carbon (POC) and Particulate Organic Nitrogen (PON).