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Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment

We performed an experiment in the Baltic Sea in order to investigate the consequences of the increasing CO₂levels on biological processes in the free water mass. There was more accumulation of organic carbon at high CO₂levels. Surprisingly, this was caused by reduced loss processes (respiration and bacterial production) in a high-CO₂environment, and not by increased photosynthetic fixation of CO₂. Our carbon budget can be used to better disentangle the effects of ocean acidification.

Using present-day observations to detect when anthropogenic change forces surface ocean carbonate chemistry outside preindustrial bounds

Biogeosciences
DOI 10.5194/bg-13-5065-2016
13 September 2016

Ocean carbonate observations from surface buoys reveal that marine life is currently exposed to conditions outside preindustrial bounds at 12 study locations around the world. Seasonal conditions in the California Current Ecosystem and Gulf of Maine also exceed thresholds that may impact shellfish larvae. High-resolution observations place long-term change in the context of large natural variability: a necessary step to understand ocean acidification impacts under real-world conditions.

Spring bloom onset in the Nordic Seas

We investigated the bloom onset in the Nordic Seas using 6 bio-optical floats. We found that the float data are consistent with two possible scenarios for the onset of blooms in the Nordic Seas. The Nordic Seas blooms could have started either when the light became sufficiently abundant that the division rates exceeded the loss rates, or when the photoperiod, the number of daily light hours experienced by phytoplankton, exceeded a critical value.

Estimate of changes in agricultural terrestrial nitrogen pathways and ammonia emissions from 1850 to present in the Community Earth System Model

Future increases are predicted in the amount of nitrogen produced as manure or used as synthetic fertilizer in agriculture. However, the impact of climate on the subsequent fate of this nitrogen has not been evaluated. Here we describe, analyze and evaluate the FAN (flows of agricultural nitrogen) process model that simulates the the climate-dependent flows of nitrogen from agriculture. The FAN model is suitable for use within a global terrestrial climate model.

Non-deforestation fire vs. fossil fuel combustion: the source of CO2 emissions affects the global carbon cycle and climate responses

We simulated both fire pulses and stable fire regimes and found the resulting climatic impacts to be irreconcilable with equivalent amounts of CO2 emissions produced by fossil fuel combustion. Consequently, side-by-side comparisons of fire and fossil fuel CO2 emissions—implicitly implying that they have similar effects—should be avoided. Our study calls for the explicit representation of fire in climate models in order to improve our understanding of its impacts in the Earth system.

A multiproxy approach to understanding the “enhanced” flux of organic matter through the oxygen-deficient waters of the Arabian Sea

Drifting sediment traps were deployed in the oxygen-deficient waters of the Arabian Sea, where the sinking flux is less attenuated than in more oxic waters. Six mechanisms that might explain this “enhanced flux” were evaluated using literature and data. In the upper 500m, evidence was found supporting an oxygen effect and/or changes in the efficiency of the microbial loop, including the addition of chemoautotrophic carbon to the sinking flux.

Ideas and perspectives: Holocene thermokarst sediments of the Yedoma permafrost region do not increase the northern peatland carbon pool

We investigate the properties of soils and sediments in a particular and ancient Siberian permafrost landscape. We critically examine statements from a recent study that specific permafrost landforms affected by thawed permafrost (alases) in this region contain very large quantities of peat that previous studies had failed to include because of data set biases. We conclude that there is no evidence to suggest biases in existing data sets or that alas deposits increase the northern peatland pool.

Upwellings mitigated Plio-Pleistocene heat stress for reef corals on the Florida platform (USA)

We present stable isotope proxy data and calcification records from fossil reef corals. The corals investigated derive from the Florida carbonate platform and are of middle Pliocene to early Pleistocene age. From the data we infer an environment subject to intermittent upwelling on annual to decadal timescales. Calcification rates were enhanced during periods of upwelling. This is likely an effect of dampened SSTs during the upwelling.

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All-clear for gourmets: truffles not radioactive

Although ranging among the most expensive gourmet foods, it remains unclear whether truffles accumulate radioactivity at a harmful level comparable to other fungi. Insignificant radiocaesium concentrations in specimens from Switzerland, Germany, France, Italy, and Hungary provide an all-clear for truffle hunters and cultivators in Europe as well as dealers and customers from around the world.

Apparent increase in coccolithophore abundance in the subtropical North Atlantic from 1990 to 2014

In this study, we combine phytoplankton pigment data with particulate inorganic carbon and chlorophyll measurements from the satellite record to assess recent trends in phytoplankton dynamics in the North Atlantic subtropical gyre, with a focus on coccolithophores. We show that coccolithophores in the North Atlantic have been increasing in abundance. Correlations suggest that they are responding positively to increasing inorganic carbon from anthropogenic inputs in the upper mixed layer.

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