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Breitburg, DL, Salisbury J, Bernhard JM, Cai WJ, Dupont S, Doney SC, Kroeker KJ, Levin LA, Long WC, Milke LM, Miller SH, Phelan B, Passow U, Seibel BA, Todgham AE, Tarrant AM.  2015.  And on top of all that... Coping with ocean acidification in the midst of many stressors. Oceanography. 28:48-61.   10.5670/oceanog.2015.31   AbstractWebsite

Oceanic and coastal waters are acidifying due to processes dominated in the open ocean by increasing atmospheric CO2 and dominated in estuaries and some coastal waters by nutrient-fueled respiration. The patterns and severity of acidification, as well as its effects, are modified by the host of stressors related to human activities that also influence these habitats. Temperature, deoxygenation, and changes in food webs are particularly important co-stressors because they are pervasive, and both their causes and effects are often mechanistically linked to acidification. Development of a theoretical underpinning to multiple stressor research that considers physiological, ecological, and evolutionary perspectives is needed because testing all combinations of stressors and stressor intensities experimentally is impossible. Nevertheless, use of a wide variety of research approaches is a logical and promising strategy for improving understanding of acidification and its effects. Future research that focuses on spatial and temporal patterns of stressor interactions and on identifying mechanisms by which multiple stressors affect individuals, populations, and ecosystems is critical. It is also necessary to incorporate consideration of multiple stressors into management, mitigation, and adaptation to acidification and to increase public and policy recognition of the importance of addressing acidification in the context of the suite of other stressors with which it potentially interacts.

Mora, C, Wei CL, Rollo A, Amaro T, Baco AR, Billett D, Bopp L, Chen Q, Collier M, Danovaro R, Gooday AJ, Grupe BM, Halloran PR, Ingels J, Jones DOB, Levin LA, Nakano H, Norling K, Ramirez-Llodra E, Rex M, Ruhl HA, Smith CR, Sweetman AK, Thurber AR, Tjiputra JF, Usseglio P, Watling L, Wu TW, Yasuhara M.  2013.  Biotic and human vulnerability to projected changes in ocean biogeochemistry over the 21st century. Plos Biology. 11   10.1371/journal.pbio.1001682   AbstractWebsite

Ongoing greenhouse gas emissions can modify climate processes and induce shifts in ocean temperature, pH, oxygen concentration, and productivity, which in turn could alter biological and social systems. Here, we provide a synoptic global assessment of the simultaneous changes in future ocean biogeochemical variables over marine biota and their broader implications for people. We analyzed modern Earth System Models forced by greenhouse gas concentration pathways until 2100 and showed that the entire world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity. In contrast, only a small fraction of the world's ocean surface, mostly in polar regions, will experience increased oxygenation and productivity, while almost nowhere will there be ocean cooling or pH elevation. We compiled the global distribution of 32 marine habitats and biodiversity hotspots and found that they would all experience simultaneous exposure to changes in multiple biogeochemical variables. This superposition highlights the high risk for synergistic ecosystem responses, the suite of physiological adaptations needed to cope with future climate change, and the potential for reorganization of global biodiversity patterns. If co-occurring biogeochemical changes influence the delivery of ocean goods and services, then they could also have a considerable effect on human welfare. Approximately 470 to 870 million of the poorest people in the world rely heavily on the ocean for food, jobs, and revenues and live in countries that will be most affected by simultaneous changes in ocean biogeochemistry. These results highlight the high risk of degradation of marine ecosystems and associated human hardship expected in a future following current trends in anthropogenic greenhouse gas emissions.

Hofmann, GE, Smith JE, Johnson KS, Send U, Levin LA, Micheli F, Paytan A, Price NN, Peterson B, Takeshita Y, Matson PG, Crook ED, Kroeker KJ, Gambi MC, Rivest EB, Frieder CA, Yu PC, Martz TR.  2011.  High-Frequency Dynamics of Ocean pH: A Multi-Ecosystem Comparison. Plos One. 6   10.1371/journal.pone.0028983   AbstractWebsite

The effect of Ocean Acidification (OA) on marine biota is quasi-predictable at best. While perturbation studies, in the form of incubations under elevated pCO(2), reveal sensitivities and responses of individual species, one missing link in the OA story results from a chronic lack of pH data specific to a given species' natural habitat. Here, we present a compilation of continuous, high-resolution time series of upper ocean pH, collected using autonomous sensors, over a variety of ecosystems ranging from polar to tropical, open-ocean to coastal, kelp forest to coral reef. These observations reveal a continuum of month-long pH variability with standard deviations from 0.004 to 0.277 and ranges spanning 0.024 to 1.430 pH units. The nature of the observed variability was also highly site-dependent, with characteristic diel, semi-diurnal, and stochastic patterns of varying amplitudes. These biome-specific pH signatures disclose current levels of exposure to both high and low dissolved CO2, often demonstrating that resident organisms are already experiencing pH regimes that are not predicted until 2100. Our data provide a first step toward crystallizing the biophysical link between environmental history of pH exposure and physiological resilience of marine organisms to fluctuations in seawater CO2. Knowledge of this spatial and temporal variation in seawater chemistry allows us to improve the design of OA experiments: we can test organisms with a priori expectations of their tolerance guardrails, based on their natural range of exposure. Such hypothesis-testing will provide a deeper understanding of the effects of OA. Both intuitively simple to understand and powerfully informative, these and similar comparative time series can help guide management efforts to identify areas of marine habitat that can serve as refugia to acidification as well as areas that are particularly vulnerable to future ocean change.