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Ideas and perspectives: hydrothermally driven redistribution and sequestration of early Archaean biomass – the “hydrothermal pump hypothesis”

The origin of organic matter in the oldest rocks on Earth is commonly ambiguous (biotic vs. abiotic). This problem culminates in the case of hydrothermal chert veins that contain abundant organic matter. Here we demonstrate a microbial origin of kerogen embedded in a 3.5 Gyr old hydrothermal chert vein. We explain this finding with the large-scale redistribution of biomass by hydrothermal fluids, emphasizing the interplay between biological and abiological processes on the early Earth.

Satellite remote sensing reveals a positive impact of living oyster reefs on microalgal biofilm development

Biogeosciences
DOI 10.5194/bg-15-905-2018
13 February 2018

Using satellite technology and a life-size experiment, we analysed the impact of oyster reefs on mats of microscopic algae that develop within coastal mudflats. We showed that the relationship between microalgae and oysters is not limited to a one-way process where microalgae are a food source to oysters, but that oysters also promote microalgae mats development, presumably by providing nutrients to them. This might yield new insights into coastal ecosystem management.

Modelling ocean-colour-derived chlorophyll a

This study provides a demonstration that a biogeochemical/ecosystem/optical computer model which explicitly captures how light is radiated at the surface of the ocean and can be used as a laboratory to explore products (such as Chla) that are derived from satellite measurements of ocean colour. It explores uncertainties that arise from data input used to derive the algorithms for the products, and issues arising from the interplay between optically important constituents in the ocean.

Reviews and syntheses: to the bottom of carbon processing at the seafloor

Organic carbon processing at the seafloor is studied by geologists to better understand the sedimentary record, by biogeochemists to quantify burial and respiration, by organic geochemists to elucidate compositional changes, and by ecologists to follow carbon transfers within food webs. These disciplinary approaches have their strengths and weaknesses. This award talk provides a synthesis, highlights the role of animals in sediment carbon processing and presents some new concepts.

Continuous measurement of air–water gas exchange by underwater eddy covariance

We use the aquatic eddy covariance technique – developed first for benthic O₂flux measurements – right below the air–water interface (~ 4 cm) to determine gas exchange rates and coefficients. This use of the technique is particularly useful in studies of gas exchange and its dynamics and controls. The approach can thus help reduce the recognized problem of large uncertainties linked to gas exchange estimates in traditional aquatic ecosystem studies.

Reviews and syntheses: on the roles trees play in building and plumbing the critical zone

This review represents the outcome from an invigorating workshop discussion that involved tree physiologists, geomorphologists, ecologists, geochemists, and hydrologists and developed nine hypotheses that could be tested. We argue these hypotheses point to the essence of issues we must explore if we are to understand how the natural system of the earth surface evolves, and how humans will affect its evolution. This paper will create discussion and interest both before and after publication.

Global consequences of afforestation and bioenergy cultivation on ecosystem service indicators

Many climate change mitigation scenarios require negative emissions from land management. However, environmental side effects are often not considered. Here, we use projections of future land use from two land-use models as input to a vegetation model. We show that carbon removal via bioenergy production or forest maintenance and expansion affect a range of ecosystem functions. Largest impacts are found for crop production, nitrogen losses, and emissions of biogenic volatile organic compounds.

Vertical segregation among pathways mediating nitrogen loss (N2 and N2O production) across the oxygen gradient in a coastal upwelling ecosystem

This investigation characterizes the variability of pathways involved in N loss in the water column over the continental shelf off central Chile during the development of the upwelling season. Our results highlight the links between several pathways involved in N removal, and considering the extreme variation in oxygen observed could help to understand the ecological and biogeochemical implications due to global warming when intensification and/or expansion of the oceanic OMZs are projected.

Expansion of oil palm and other cash crops causes an increase of the land surface temperature in the Jambi province in Indonesia

From the analysis of MODIS and Landsat satellite data of the Jambi province in Indonesia, this first study on the effects of oil palm expansion on the surface temperature in Indonesia shows shows a local and regional warming effect caused by the expansion of oil palm plantations and other cash or tree crops between 2000 and 2015. The observed warming effects may affect ecosystem services, reduce water availabilty in the dry period and increase the vulnerability to fires in the province.

Reviews and syntheses: Systematic Earth observations for use in terrestrial carbon cycle data assimilation systems

This paper briefly reviews data assimilation techniques in carbon cycle data assimilation and the requirements of data assimilation systems on observations. We provide a non-exhaustive overview of current observations and their uncertainties for use in terrestrial carbon cycle data assimilation, focussing on relevant space-based observations.

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