Posts Tagged 'review'

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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Ulva prolifera green tide outbreaks and their environmental impact in the Yellow Sea, China

The Ulva prolifera green tides in the Yellow Sea, China, which have been occurring since 2007 are a serious environmental problem attracting worldwide attention. Despite extensive research, the outbreak mechanisms have not been fully understood. Comprehensive analysis of anthropogenic and natural biotic and abiotic factors reveals that human activities, regional physicochemical conditions and algal physiological characteristics as well as ocean warming and biological interactions (with microorganism or other macroalgae) are closely related with the occurrence of green tides. Dynamics of these factors and their interactions could explain why green tides suddenly occurred in 2007 and decreased abruptly in 2017. Moreover, the consequence of green tides is serious. The decay of macroalgal biomass could result in hypoxia and acidification, possibly induce red tide, and even have long lasting impact on coastal carbon cycles and ecosystem. Accordingly, corresponding countermeasures have been proposed in our study for future reference in ecosystem management strategy and sustainable development policy.

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Impacts of global warming and elevated CO2 on sensory behavior in predator-prey interactions: a review and synthesis

Ecosystems are shaped by complex interactions between species and their environment. However, humans are rapidly changing the environment through increased carbon dioxide (CO2) emissions, creating global warming and elevated CO2 levels that affect ecological communities through multiple processes. Understanding community responses to climate change requires examining the consequences of changing behavioral interactions between species, such as those affecting predator and prey. Understanding the underlying sensory process that govern these interactions and how they may be affected by climate change provides a predictive framework, but many studies examine behavioral outcomes only. This review summarizes the current knowledge of global warming and elevated CO2 impacts on predator-prey interactions with respect to the relevant aspects of sensory ecology, and we discuss the potential consequences of these effects. Our specific questions concern how climate change affects the ability of predators and prey to collect information and how this affects predator-prey interactions. We develop a framework for understanding how warming and elevated CO2 can alter behavioral interactions by examining how the processes (steps) of sensory cue (or signal) production, transmission and reception may change. This includes both direct effects on cue production and reception resulting from changes in organismal physiology, but also effects on cue transmission resulting from modulation of the physical environment via physical and biotic changes. We suggest that some modalities may be particularly prone to disruption, and that aquatic environments may suffer more serious disruptions as a result of elevated CO2 and warming that collectively affect all steps of the signaling process. Temperature by itself may primarily operate on aspects of cue generation and transmission, implying that sensory-mediated disruptions in terrestrial environments may be less severe. However, significant biases in the literature in terms of modalities (chemosensation), taxa (fish), and stressors (elevated CO2) examined currently prevents accurate generalizations. Significant issues such as multimodal compensation and altered transmission or other environmental effects remain largely unaddressed. Future studies should strive to fill these knowledge gaps in order to better understand and predict shifts in predator-prey interactions in a changing climate.

Continue reading ‘Impacts of global warming and elevated CO2 on sensory behavior in predator-prey interactions: a review and synthesis’

Highest plasticity of carbon‐concentrating mechanisms in earliest evolved phytoplankton

Phytoplankton photosynthesis strongly relies on the operation of carbon‐concentrating mechanisms (CCMs) to accumulate CO2 around their carboxylating enzyme ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBisCO). Earlier evolved phytoplankton groups were shown to exhibit higher CCM activities to compensate for their RuBisCO with low CO2 specificities. Here, we tested whether earlier evolved phytoplankton groups also exhibit a higher CCM plasticity. To this end, we collected data from literature and applied a Bayesian linear meta‐analytic model. Our results show that with elevated pCO2, photosynthetic CO2 affinities decreased strongest and most consistent for the earlier evolved groups, i.e., cyanobacteria and dinoflagellates, while CO2‐dependent changes in affinities for haptophytes and diatoms were smaller and less consistent. In addition, responses of maximum photosynthetic rates toward elevated pCO2 were generally small and inconsistent across species. Our results demonstrate that phytoplankton groups with an earlier origin possess a high CCM plasticity, whereas more recently evolved groups do not, which likely results from evolved differences in the CO2 specificity of RuBisCO.

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Evolution of the human impact on oceans: tipping points of socio-ecological coviability

Since an important degree of the carbon dioxide (CO2) that mankind emits in the atmosphere ends up in the ocean as a result of gas exchange through the air-sea interface, the ocean acidifies itself (because of the reaction CO2 produces when it contacts water). Ocean acidification is one of the perturbing anthropogenic effects (because of human activity), not only for maritime ecosystems but also for Man himself as he will have to adapt. He will have to deal with variations in fisheries and other costal touristic activities (reduction of corals, and so on). However, the anthropogenic CO2 penetration in the ocean is not uniform, and the cold Polar Regions will be affected by the change faster than the warm tropical regions. The study that we are conducting addresses several points of the quantification, in time and space, of anthropogenic CO2 penetration in the ocean. One of them has permitted the identification of breaking points. We demonstrate that four tipping points can be located in order to quantify risks of ocean acidification, which may have as a result the dissolution of calcium carbonates that are indispensable to marine ecosystems (shells, corals, and so on).

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Ocean carbon cycle

This article briefly reviews the broader aspects of the global carbon cycle and in particular, the ocean carbon cycle. Topics discussed include the following: a brief overview of the global carbon cycle; the ocean carbon and the chemistry of carbon dioxide in seawater; the solubility, exchange of carbon dioxide between the ocean and atmosphere, and chemical buffering in seawater; recent perturbations to the marine carbon cycle including ocean acidification; and solubility, biological and carbonate pumps that transport and redistribute carbon in the ocean. This revised piece updates an early version of the article (Carlson et al., 2001).

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Socio-economic tools to mitigate the impacts of ocean acidification on economies and communities reliant on coral reefs–a framework for prioritization

Coral reef preservation is a challenge for the whole of humanity, not just for the estimated three billion people that directly depend upon coral reefs for their livelihoods and food security. Ocean acidification combined with rising sea surface temperatures, and an array of other anthropogenic influences such as pollution, sedimentation, over fishing, and coral mining represent the key threats currently facing coral reef survival. Here we summarise a list of agreements, policies, and socio-economic tools and instruments that can be used by global, national and local decision-makers to address ocean acidification and associated threats, as identified during an expert workshop in October 2017. We then discuss these tools and instruments at a global level and identify the key tasks for raising decision makers’ awareness. Finally, we suggest ways of prioritizing between different actions or tools for mitigation and adaptation.

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Ocean acidification in the IPCC AR5 WG II

OUP book