Gulf of Mexico Battles Expanding Dead Zone in Louisiana
The Gulf of Mexico meets the shorelines of Alabama, Louisiana, Mississippi, Texas and western Florida and is home to a large fishing industry. Several rivers from the Midwestern watershed flow south into the Gulf, carrying with them sediment, nutrient loads, and pollution from fossil fuel burning and wastewater systems.
The problem isn’t new, but it is expanding. "
Author: Mindy Cooper
Source: Environmental Monitor
Deep oceans may acidify faster than anticipated due to global warming
"Oceans worldwide are undergoing acidification due to the penetration of anthropogenic CO2 from the atmosphere. The rate of acidification generally diminishes with increasing depth. Yet, slowing down of the thermohaline circulation due to global warming could reduce the pH in the deep oceans, as more organic material would decompose with a longer residence time. [...]"
Source: Nature Climate Change
Authors: Chen-Tung Arthur Chen
Read the full article here.
Investigating the impacts of treated effluent discharge on coastal water health (Visakhapatnam, SW coast of Bay of Bengal, India)
"The present study investigated the impacts of treated effluent discharge on physicochemical and biological properties of coastal waters from three pharmaceuticals situated along the coast of Visakhapatnam (SW Bay of Bengal). Seawater samples were collected (during the months of December 2013, March 2014 and April 2014) from different sampling locations (Chippada (CHP), Tikkavanipalem (TKP) and Nakkapalli (NKP)) at 0- and 30-m depths within 2-km radius (0.5 km = inner, 1 km = middle and 2 km = outer sampling circles) from the marine outfall points. [...]"
Source: Environmental Monitoring and Assessment
Authors: Aziz Ur Rahman Shaik et al.
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.