Repeated storage of respired carbon in the equatorial Pacific Ocean over the last three glacial cycles
"As the largest reservoir of carbon exchanging with the atmosphere on glacial–interglacial timescales, the deep ocean has been implicated as the likely location of carbon sequestration during Pleistocene glaciations. Despite strong theoretical underpinning for this expectation, radiocarbon data on watermass ventilation ages conflict, and proxy interpretations disagree about the depth, origin and even existence of the respired carbon pool. [...]"
Authors: A.W. Jacobel
Source: Nature Communications
Oxygenation as a driver of the Great Ordovician Biodiversification Event
"The largest radiation of Phanerozoic marine animal life quadrupled genus-level diversity towards the end of the Ordovician Period about 450 million years ago. A leading hypothesis for this Great Ordovician Biodiversification Event is that cooling of the Ordovician climate lowered sea surface temperatures into the thermal tolerance window of many animal groups, such as corals. [...]"
Source: Nature Geoscience
Authors: Cole T. Edwards
Ocean deoxygenation – a climate-related problem
"Many take for granted low oxygen as “just another water-quality issue”. Excessive loads of nutrients from non-point and point sources, including sewage, enter aquatic ecosystems where they increase biological oxygen demand and promote eutrophic conditions that can lead to periods of hypoxia or anoxia (in coastal areas somewhat misnamed as “dead zones”). [...]"
Source: Frontiers in Ecology and the Environment
Authors: Karin E Limburg, Denise Breitburg, Lisa A Levin
When oxygen disappeared, early marine animals really started evolving
"Animals need oxygen to survive, but a relative lack of oxygen in Earth’s ancient oceans helped early marine creatures evolve, a new study claims. Indeed, the “Cambrian explosion”—the burst of evolution about 540 million years ago that included the birth of most of the major animal groups we know today—was enabled by oxygen deprivation, the researchers say. The finding comes in the wake of a better understanding of how oxygen levels in the oceans and the atmosphere fluctuated in the deep past, and may shift how scientists think animal evolution can proceed. [...]"
Source: Science Magazine
Author: Lucas Joel
Read the full article here.
Diverse Marinimicrobia bacteria may mediate coupled biogeochemical cycles along eco-thermodynamic gradients
"Microbial communities drive biogeochemical cycles through networks of metabolite exchange that are structured along energetic gradients. As energy yields become limiting, these networks favor co-metabolic interactions to maximize energy disequilibria. Here we apply single-cell genomics, metagenomics, and metatranscriptomics to study bacterial populations of the abundant “microbial dark matter” phylum Marinimicrobia along defined energy gradients. [...]"
Source: Nature Communications
Authors: Alyse K. Hawley et al.
A Three-Dimensional Mapping of the Ocean Based on Environmental Data
"The existence, sources, distribution, circulation, and physicochemical nature of macroscale oceanic water bodies have long been a focus of oceanographic inquiry. Building on that work, this paper describes an objectively derived and globally comprehensive set of 37 distinct volumetric region units, called ecological marine units (EMUs). They are constructed on a regularly spaced ocean point-mesh grid, from sea surface to seafloor, and attributed with data from the 2013 World Ocean Atlas version 2. The point attribute data are the means of the decadal averages from a 57-year climatology of six physical and chemical environment parameters (temperature, salinity, dissolved oxygen, nitrate, phosphate, and silicate). [...]"
Authors: Roger G. Sayre
Abyssal ocean overturning shaped by seafloor distribution
"The abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less-dense waters above them. Understanding what controls the strength and structure of these interhemispheric flows—referred to as the abyssal overturning circulation—is key to quantifying the ocean’s ability to store carbon and heat on timescales exceeding a century. [...]"
Authors: C. de Lavergne et al.
Mysterious ‘shadow zone’ traps 2000-year-old water
"A MYSTERIOUS abyss in the ocean known as the “shadow zone” traps ancient water dating back to 400AD. We now know why it’s there.
IT’S called the “shadow zone” and it lies around two kilometres below the surface in an ocean abyss where trapped water dates back to the fourth century.
This ancient water, which is between 1000 and 2000 years old, dates back to when the ancient Germanic tribe the Goths instigated the end of the Western Roman Empire and the rise of Medieval Europe. [...]"
M/V Columbia starts its study of ocean acidification
"An Alaska state ferry recently started work doubling as an ocean research platform.
The M/V Columbia, which conducts weekly runs between Bellingham, Washington and Alaska, has been installed with a seawater monitoring system to study ocean acidification, a byproduct of human-caused climate change which could affect sea life in Alaska and around the world. [...]"
Source: Juneau Empire
Climate and anthropogenic controls of coastal deoxygenation on interannual to centennial timescales
"Understanding dissolved oxygen variability in the ocean is limited by the short duration of direct measurements, however sedimentary oxidation-reduction reactions can provide context for modern observations. Here we use bulk sediment redox-sensitive metal enrichment factors (MoEF, ReEF, and UEF) and scanning X-ray fluorescence (XRF) records to examine annual-scale sedimentary oxygen concentrations in the Santa Barbara Basin from the Industrial Revolution (AD ~1850) to present. [...]"
Source: Geophysical Research Letters
Authors: Yi Wang, Ingrid Hendy, Tiffany J. Napier