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Organic matter composition and heterotrophic bacterial activity at declining summer sea ice in the central Arctic Ocean

Abstract.

"The Arctic Ocean is highly susceptible to climate change as evidenced by rapid warming and the drastic loss of sea ice during summer. The consequences of these environmental changes for the microbial cycling of organic matter are largely unexplored. Here, we investigated the distribution and composition of dissolved organic matter (DOM) along with heterotrophic bacterial activity in seawater and sea ice of the Eurasian Basin at the time of the record ice minimum in 2012. Bacteria in seawater were highly responsive to fresh organic matter and remineralized on average 55% of primary production in the upper mixed layer. Correlation analysis showed that the accumulation of dissolved combined carbohydrates (DCCHO) and dissolved[...]"

 

Source: Association for the Sciences Limnology and Oceanography
Authors: Judith Piontek et al.
DOI: https://doi.org/10.1002/lno.11639

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Atmospheric deposition of organic matter at a remote site in the central Mediterranean Sea: implications for the marine ecosystem

Abstract.

"Atmospheric fluxes of dissolved organic matter (DOM) were studied for the first time on the island of Lampedusa, a remote site in the central Mediterranean Sea (Med Sea), between 19 March 2015 and 1 April 2017. The main goals of this study were to quantify total atmospheric deposition of DOM in this area and to evaluate the impact of Saharan dust deposition on DOM dynamics in the surface waters of the Mediterranean Sea. Our data show high variability in DOM deposition rates without a clear seasonality and a dissolved organic carbon (DOC) input from the atmosphere of 120.7 mmol DOC m−2 yr−1. [...]"

Source: Biogeosciences
Authors: Yuri Galletti et al.
DOI: 10.5194/bg-17-3669-2020

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Seasonal changes in the chemical composition and reactivity of dissolved organic matter at the land-ocean interface of a subtropical river

Abstract.

"Dissolved organic matter (DOM) is a critical component in aquatic ecosystems, yet its seasonal variability and reactivity remain not well constrained. These were investigated at the land-ocean interface of a subtropical river (Minjiang River, SE China), using absorption and fluorescence spectroscopy. [...]"

Source: Environmental Science and Pollution Research
Authors: Liyang Yang et al.
DOI: 10.1007/s11356-019-05700-2

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High denitrification and anaerobic ammonium oxidation contributes to net nitrogen loss in a seagrass ecosystem in the central Red Sea

Abstract.

"Nitrogen loads in coastal areas have increased dramatically, with detrimental consequences for coastal ecosystems. Shallow sediments and seagrass meadows are hotspots for denitrification, favoring N loss. However, atmospheric dinitrogen (N2) fixation has been reported to support seagrass growth. Therefore, the role of coastal marine systems dominated by seagrasses in the net N2 flux remains unclear. Here, we measured denitrification, anaerobic ammonium oxidation (anammox), and N2 fixation in a tropical seagrass (Enhalus acoroides) meadow and the adjacent bare sediment in a coastal lagoon in the central Red Sea. [...]"

Source: Biogeosciences
Authors: Neus Garcias-Bonet et al.
DOI: 10.5194/bg-15-7333-2018

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Distribution of Meiofauna in Bathyal Sediments Influenced by the Oxygen Minimum Zone Off Costa Rica

Abstract.

"Ocean deoxygenation has become a topic of increasing concern because of its potential impacts on marine ecosystems, including oxygen minimum zone (OMZ) expansion and subsequent benthic effects. We investigated the influence of oxygen concentration and organic matter (OM) availability on metazoan meiofauna within and below an OMZ in bathyal sediments off Costa Rica, testing the hypothesis that oxygen and OM levels are reflected in meiofaunal community structures and distribution. Mean total densities in our sampling cores (400–1800 m water depth) were highest with 3688 ind. 10 cm−2 at the OMZ core at 400 m water depth, decreasing rapidly downslope. [...]"

Source: Frontiers in Marine Science
Authors: Carlos Neira et al.
DOI: 10.3389/fmars.2018.00448

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Distribution of meiofauna in bathyal sediments influenced by the oxygen minimum zone off Costa Rica

Abstract.

"Ocean deoxygenation has become a topic of increasing concern because of its potential impacts on marine ecosystems, including oxygen minimum zone (OMZ) expansion and subsequent benthic effects. We investigated the influence of oxygen concentration and organic matter (OM) availability on metazoan meiofauna within and below an OMZ in bathyal sediments off Costa Rica, testing the hypothesis that oxygen and OM levels are reflected in meiofaunal community structures and distribution. [...]"

Source: Frontiers in Marine Science
Authors: Carlos Neira et al.
DOI: 10.3389/fmars.2018.00448

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Deep-ocean dissolved organic matter reactivity along the Mediterranean Sea: does size matter?

Abstract.

"Despite of the major role ascribed to marine dissolved organic matter (DOM) in the global carbon cycle, the reactivity of this pool in the dark ocean is still poorly understood. Present hypotheses, posed within the size-reactivity continuum (SRC) and the microbial carbon pump (MCP) conceptual frameworks, need further empirical support. Here, we provide field evidence of the soundness of the SRC model. We sampled the high salinity core-of-flow of the Levantine Intermediate Water along its westward route through the entire Mediterranean Sea. At selected sites, DOM was size-fractionated in apparent high (aHMW) and low (aLMW) molecular weight fractions using an efficient ultrafiltration cell. [...]"

Source: Scientific Reports
Authors: Alba María Martínez-Pérez, Xosé Antón Álvarez-Salgado, Javier Arístegui & Mar Nieto-Cid
DOI: 10.1038/s41598-017-05941-6

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