Posts Tagged 'review'

Better regional ocean observing through cross-national cooperation: a case study from the Northeast Pacific

The ocean knows no political borders. Ocean processes, like summertime wind-driven upwelling, stretch thousands of kilometers along the Northeast Pacific (NEP) coast. This upwelling drives marine ecosystem productivity and is modulated by weather systems and seasonal to interdecadal ocean-atmosphere variability. Major ocean currents in the NEP transport water properties such as heat, fresh water, nutrients, dissolved oxygen, pCO2, and pH close to the shore. The eastward North Pacific Current bifurcates offshore in the NEP, delivering open-ocean signals south into the California Current and north into the Gulf of Alaska. There is a large and growing number of NEP ocean observing elements operated by government agencies, Native American Tribes, First Nations groups, not-for-profit organizations, and private entities. Observing elements include moored and mobile platforms, shipboard repeat cruises, as well as land-based and estuarine stations. A wide range of multidisciplinary ocean sensors are deployed to track, for example, upwelling, downwelling, ocean productivity, harmful algal blooms, ocean acidification and hypoxia, seismic activity and tsunami wave propagation. Data delivery to shore and observatory controls are done through satellite and cell phone communication, and via seafloor cables. Remote sensing from satellites and land-based coastal radar provide broader spatial coverage, while numerical circulation and biogeochemical modeling complement ocean observing efforts. Models span from the deep ocean into the inland Salish Sea and estuaries. NEP ocean observing systems are used to understand regional processes and, together with numerical models, provide ocean forecasts. By sharing data, experiences and lessons learned, the regional ocean observatory is better than the sum of its parts.

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Dynamic CO2 and pH levels in coastal, estuarine, and inland waters: theoretical and observed effects on harmful algal blooms

Highlights

• Global change effects on HABs are often modified by local factors.
• Interaction of environmental factors complicates multifactorial experiments.
• HABs may become more severe as a result of acclimating to global change.
• More studies are needed to determine genetic adaptation of HAB species to global change.

Abstract

Rising concentrations of atmospheric CO2 results in higher equilibrium concentrations of dissolved CO2 in natural waters, with corresponding increases in hydrogen ion and bicarbonate concentrations and decreases in hydroxyl ion and carbonate concentrations. Superimposed on these climate change effects is the dynamic nature of carbon cycling in coastal zones, which can lead to seasonal and diel changes in pH and COconcentrations that can exceed changes expected for open ocean ecosystems by the end of the century. Among harmful algae, i.e. some species and/or strains of CyanobacteriaDinophyceae, Prymnesiophyceae, Bacillariophyceae, and Ulvophyceae, the occurrence of a CO2 concentrating mechanisms (CCMs) is the most frequent mechanism of inorganic carbon acquisition in natural waters in equilibrium with the present atmosphere (400 μmol CO2  mol−1 total gas), with varying phenotypic modification of the CCM. No data on CCMs are available for Raphidophyceae or the brown tide Pelagophyceae. Several HAB species and/or strains respond to increased CO2 concentrations with increases in growth rate and/or cellular toxin content, however, others are unaffected. Beyond the effects of altered C concentrations and speciation on HABs, changes in pH in natural waters are likely to have profound effects on algal physiology. This review outlines the implications of changes in inorganic cycling for HABs in coastal zones, and reviews the knowns and unknowns with regard to how HABs can be expected to ocean acidification. We further point to the large regions of uncertainty with regard to this evolving field.

 

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A review of interventions proposed to abate impacts of ocean acidification on coral reefs

Coral reefs experiencing ocean acidification (OA) are likely to recover much more slowly from damage caused by acute events such as mass bleaching because OA slows coral reef growth and reproduction. To maintain reefs in a net growth or net-neutral condition, curbing the impact of OA is therefore necessary. A variety of mitigation and adaptation strategies have been proposed to abate OA impacts on reefs. However, detailed guidance for managers on the types, effectiveness, or costs of different local interventions to address OA is scarce. To advance the discussion about available interventions, this review explores and compares mitigation and adaptation techniques that have been proposed to abate OA impacts on coral reefs. We focus primarily on four categories of interventions intended to address different ecosystem service changes: phytoremediation, chemical remediation, reef restoration, and assisted evolution. We briefly touch on traditional restoration methods like marine protected areas (MPAs) and reducing secondary sources of stress. Of the techniques reviewed, most are costly and do not scale at the same pace as global reef loss. Nor do they address the root cause of OA, global carbon emissions. That said, intervention should not be an all or nothing approach; some techniques may be worth implementing at smaller scales in a coordinated way. Working to save pieces of ecosystems and buying time may help ensure that there is more to rebuild from in the future. Despite the seemingly high price tag of many of these techniques, given the potential value of regained ecosystem services, net gains may exceed implementation costs. It is certain, however, from the limited reach of coral reef interventions, that they must be undertaken as part of a suite of global-scale interventions including atmospheric CO2 reduction to preserve coral reef ecosystem function and benefits to humanity.

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Seagrasses, the unique adaptation of angiosperms to the marine environment: effect of high carbon and ocean acidification on energetics and ion homeostasis

As a functional group, seafrasses form highly productive ecosystems present along the coasts of all continents (except Antarctic), where they rival tropical rainforests and coral reefs in ecosystem services (Costanza et al., 1997; Fourqurean et al., 2012). Unfortunately, seagrasses are diminishing worldwide and several studies confirm a lack of appreciation for the value of these systems (Cullen-Unsworth et al., 2014). Since the last century, the effects of climate change on natural and agricultural terrestrial plant communities have already received significant attention.

Continue reading ‘Seagrasses, the unique adaptation of angiosperms to the marine environment: effect of high carbon and ocean acidification on energetics and ion homeostasis’

More acidic seas

In 1956, Roger Revelle and Hans Guess, two visionary geochemists, warned of a possible increase in carbon dioxide in the atmosphere. We all know that this has happened, yet they saw beyond the rise in temperatures, because this and other gases that are responsible for the so-called greenhouse effect were forming higher and higher concentrations due to industry, transport, agricultural uses, and so on. The increase in this gas could lead, among other things, to acidification of both inland and marine waters. The issue is complex, but it arises in the following way: the carbon dioxide entering the sea combines with water and gives rise to another compound, weak carbonic acid (H2CO3), capable of releasing hydrogen ions (H+) with ease. Having lost this hydrogen, the carbonic acid remains as a bicarbonate ion, HCO3. When this happens, hydrogen ions remain in the water, acidifying the liquid medium.

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Drivers of pH variability in coastal ecosystems

A synthesis of long-term changes in pH of coastal ecosystems shows that, in contrast to the uniform trends of open-ocean acidification (-0.0004 to -0.0026 pH units yr-1) driven by increased atmospheric CO2, coastal ecosystems display a much broader range of trends (-0.023 to 0.023 pH units yr-1) and are as likely to show long-term increase as decline in pH. The majority of the 83 investigated coastal ecosystems displayed non-linear trends, with seasonal and interannual variations exceeding 1 pH unit for some sites. The high pH variability of coastal ecosystems is primarily driven by inputs from land. These include freshwater inputs that typically dilute the alkalinity of seawater thereby resulting in reduced buffering, nutrients enhancing productivity and pH, as well as organic matter supporting excess respiration driving acidification. For some coastal ecosystems, upwelling of nutrient-rich and corrosive water may also contribute to variability in pH. Metabolic control of pH was the main factor governing variability for the majority of coastal sites, displaying larger variations in coastal ecosystems with low alkalinity buffering. pH variability was particularly pronounced in coastal ecosystems with strong decoupling of production and respiration processes, seasonally or through stratification. Our analysis demonstrate that coastal pH can be managed by controlling inputs of nutrients, organic matter, and alkalinity. In well-mixed coastal waters, increasing productivity can improve resistance to ocean acidification, whereas increasing productivity enhances acidification in bottom waters of stratified coastal ecosystems. Environmental management should consider the balance between the negative consequences of eutrophication versus those of acidification, to maintain biodiversity and ecosystem services of our coastal ecosystems.

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Ocean acidification: dealing with uncharted waters

There are ancient air bubbles trapped in ice that have allowed NASA to observe what Earth’s atmosphere was like in the past 400,000 years. Through research, NASA discovered the carbon dioxide (CO2) levels in the atmosphere are higher than they have ever been. Since the industrial revolution, it is no secret humans have contributed immensely to the significant increase of CO2. In fact, the Earth’s oceans absorb an astonishing amount of CO2 emissions. Today, the Earth’s oceans absorb twenty-two million tons of CO2 every day. To make things more troublesome, researchers are predicting CO2 levels will continue to rise in the coming years, resulting in unprecedented effects to Earth. When the Earth’s ocean absorbs an increase of CO2, there is a corresponding increase in the acidity levels of the ocean’s chemical makeup. The astoundingly high levels of CO2 have resulted in Earth’s oceans becoming thirty percent more acidic than in recorded history. This underappreciated issue is called ocean acidification, and its effects create profound consequences. Ocean acidification is threatening the ocean’s chemical makeup, ecosystems, marine organisms, and biodiversity. “Absent immediate action, ‘irreversible, catastrophic changes to marine ecosystems’ are anticipated to occur[,]” even endangering human life. Although these facts are troubling, humans have the resources and ability to mitigate our ocean’s chemical makeup and change its terrifying future.

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Ocean acidification in the IPCC AR5 WG II

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