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2011
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.

Yu, PC, Matson PG, Martz TR, Hofmann GE.  2011.  The ocean acidification seascape and its relationship to the performance of calcifying marine invertebrates: Laboratory experiments on the development of urchin larvae framed by environmentally-relevant pCO(2)/pH. Journal of Experimental Marine Biology and Ecology. 400:288-295.   10.1016/j.jembe.2011.02.016   AbstractWebsite

Variation in ocean pH is a dynamic process occurring naturally in the upwelling zone of the California Current Large Marine Ecosystem. The nearshore carbonate chemistry is under-characterized and the physiology of local organisms may be under constant challenge from cyclical changes in pH and carbonate ion concentration of unexpectedly high magnitude. We looked to environmental pH conditions of coastal upwelling and used those values to examine effects of low pH on 4-arm larvae of purple sea urchin Strongylocentrotus purpuratus. We deployed a pH sensor at a nearshore shallow benthic site for 3 weeks during summer 2010 to assess the changes in pH in the Santa Barbara Channel, a region considered to have relatively less intense upwelling along the US Pacific Coast. Large fluctuations in pH of up to 0.67 pH units were observed over short time scales of several days. Daily pH fluctuations on a tidal pattern followed temperature fluctuations over short time scales, but not over scales greater than a day. The lowest pH values recorded (similar to 7.70) are lower than some of those pH values predicted to occur in surface oceans at the end of the century. In the context of this dynamic pH exposure, larvae were raised at elevated pCO(2) levels of 1000 ppm and 1450 ppm CO(2) (pH 7.7 and 7.5 respectively) and measured for total larval length (from the spicule tip of the postoral arm to the spicule tip of the aboral point) along the spicules, to assess effects of low pH upwelling water on morphology. Larvae in all treatments maintained normal development and developmental schedule to day 6, and did not exhibit significant differences in larval asymmetry between treatments. At day 3 and day 6, larvae in the 1450 ppm CO(2) treatment were significantly smaller (p<0.001) than the control larvae by only 7-13%. The observation of smaller larvae raised under high pCO(2) has an as yet undetermined physiological mechanism, but has implications for locomotion and feeding. These effects of small magnitude in these urchin larvae are indicative of a potential resilience to near-future levels of ocean acidification. Using environmental monitoring of pH to inform experimental parameters provides a means to improve our understanding of acclimatization of organisms in a dynamic ecosystem. (C) 2011 Elsevier B.V. All rights reserved.