Acid coastal seas off US putting common fish species at risk
Scientists have recently discovered that marine creatures can be adversely affected by hypercapnia, a condition of too much dissolved CO2 in seawater (CO2 partial pressure, or pCO2). When this level rises above 1000 micro atmospheres (1000 μatm), some fish species suffer cognitive problems and disorientation, such as losing their way or even swimming towards predators. Surface ocean CO2 partial pressures tend to be around 400 μatm, so until now scientists have thought that hypercapnia was a problem which would only become apparent over time in subsurface waters. [...]"
Sedimentary molybdenum cycling in the aftermath of seawater inflow to the intermittently euxinic Gotland Deep, Central Baltic Sea
"Molybdenum (Mo) concentrations and isotope compositions in sediments and shalesare commonly used as proxies for anoxic and sulfidic (i.e., euxinic) conditions in the water column of paleo-marine systems. A basic assumption underlying this practice is that the proxy signal extracted from the geological record is controlled by long-term (order of decades to millennia) Mo scavenging in the euxinic water column rather than Mo deposition during brief episodes or events (order of weeks to months). [...]"
Source: Chemical Geology
Authors: Florian Scholz et al.
Autonomous biogeochemical floats detect significant carbon dioxide outgassing in the high‐latitude Southern Ocean
"Although the Southern Ocean is thought to account for a significant portion of the contemporary oceanic uptake of carbon dioxide (CO2), flux estimates in this region are based on sparse observations that are strongly biased towards summer. Here we present new estimates of Southern Ocean air‐sea CO2 fluxes calculated with measurements from biogeochemical profiling floats deployed by the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project during 2014‐2017. Compared to ship‐based CO2 flux estimates, the float‐based fluxes find significantly stronger outgassing in the zone around Antarctica where carbon‐rich deep waters upwell to the surface ocean. [...]"
Source: Geophysical Research Letters
Authors: Alison R. Gray et al.
Transport, properties, and life cycles of mesoscale eddies in the eastern tropical South Pacific
"The influence of mesoscale eddies on the flow field and the water masses, especially the oxygen distribution of the eastern tropical South Pacific, is investigated from a mooring, float, and satellite data set. Two anticyclonic (ACE1/2), one mode-water (MWE), and one cyclonic eddy (CE) are identified and followed in detail with satellite data on their westward transition with velocities of 3.2 to 6.0cms−1 from their generation region, the shelf of the Peruvian and Chilean upwelling regime, across the Stratus Ocean Reference Station (ORS; ∼ 20°S, 85°W) to their decaying region far west in the oligotrophic open ocean. [...]"
Source: Ocean Science
Authors: Rena Czeschel et al.
Back to the future of climate change
Researchers are looking to the geologic past to make future projections about climate change. Their research focuses on the ancient Tethys Ocean (site of the present-day Mediterranean Sea) and provides a benchmark for present and future climate and ocean models.
Source: Science Daily
Perturbation to the nitrogen cycle during rapid Early Eocene global warming
"The degree to which ocean deoxygenation will alter the function of marine communities remains unclear but may be best constrained by detailed study of intervals of rapid warming in the geologic past. The Paleocene–Eocene Thermal Maximum (PETM) was an interval of rapid warming that was the result of increasing contents of greenhouse gases in the atmosphere that had wide ranging effects on ecosystems globally. Here, we present stable nitrogen isotope data from the Eastern Peri-Tethys Ocean that record a significant transition in the nitrogen cycle. [...]"
Source: Nature Communications
Authors: Christopher K. Junium, Alexander J. Dickson & Benjamin T. Uveges
Increased biofilm formation due to high-temperature adaptation in marine Roseobacter
"Ocean temperatures will increase significantly over the next 100 years due to global climate change. As temperatures increase beyond current ranges, it is unclear how adaptation will impact the distribution and ecological role of marine microorganisms. To address this major unknown, we imposed a stressful high-temperature regime for 500 generations on a strain from the abundant marine Roseobacter clade. High-temperature-adapted isolates significantly improved their fitness but also increased biofilm formation at the air–liquid interface. [...]"
Source: Nature Microbiology
Authors: Alyssa G. Kent et al.
A Novel Eukaryotic Denitrification Pathway in Foraminifera
"Benthic foraminifera are unicellular eukaryotes inhabiting sediments of aquatic environments. Several species were shown to store and use nitrate for complete denitrification, a unique energy metabolism among eukaryotes. The population of benthic foraminifera reaches high densities in oxygen-depleted marine habitats, where they play a key role in the marine nitrogen cycle. However, the mechanisms of denitrification in foraminifera are still unknown, and the possibility of a contribution of associated bacteria is debated. Here, we present evidence for a novel eukaryotic denitrification pathway that is encoded in foraminiferal genomes. [...]"
Source: Current Biology
Authors: Christian Woehle et al.
How nutrients are removed in oxygen-depleted regions of the ocean
"In the course of global climate change, scientists are observing the increase of low-oxygen areas in the ocean, also termed oxygen minimum zones (OMZs). Large-scale OMZs exist, for example, in the Pacific off the coast of South America or in the Indian Ocean. Since little to no oxygen is present in these regions - depending on the depth of the water - organisms whose metabolisms is independent of oxygen have a distinct advantage. These organisms include some representatives of the foraminifera: unicellular, shell-forming microorganisms, which have a nucleus and thus belong to the eukaryotes. Their life style involves a particular metabolic pathway termed anaerobic respiration. In the absence of oxygen, they convert nitrate present in the water into molecular nitrogen. [...]"
Scientists draw new connections between climate change and warming oceans
"Earth scientists exploring how ocean chemistry has evolved found similarities between an event 55 million years ago and current predicted trajectories of planet temperatures, with regards to inputs of CO2 into the atmosphere and oxygen levels in the oceans. As the oceans warm, oxygen decreases while hydrogen sulfide increases, making the oceans toxic and putting marine species at risk."
Source: Science Daily (University of Toronto)