Publications

Export 2 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N [O] P Q R S T U V W X Y Z   [Show ALL]
O
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.

Martz, TR, Johnson KS, Riser SC.  2008.  Ocean metabolism observed with oxygen sensors on profiling floats in the South Pacific. Limnology and Oceanography. 53:2094-2111.   10.4319/lo.2008.53.5_part_2.2094   AbstractWebsite

We estimated rates of production and export in the South Pacific (80 degrees W to 180 degrees W in a zonal band between 35 degrees S and 50 degrees S) using 1.5 yr of oxygen measurements from profiling floats. Export production, calculated from oxygen utilization rates below the compensation depth from December to April, was 10.7 +/- 2 mmol C m(-2) d(-1) (n = 36, 95% CI). The corresponding satellite net primary production was 46 6 4 mmol C m(-2) d(-1), yielding a regional e-ratio of 0.23 +/- 0.05. Averaging oxygen utilization rates resulted in a net cancellation of most water mass changes related to advection and float migration. The composite vertical profile of remineralization rates, obtained by binning 36 rate profiles, agreed with published measurements based on oxygen utilization rates in hydrographic surveys and fits the classic form of a particulate organic carbon (POC) attenuation function. However, the disagreement between oxygen-based remineralization rates and those obtained by sediment traps suggests fundamental differences between these two methods. Using float data to constrain a one-dimensional mixed-layer model, the annual net community production at 45 degrees S, 144 degrees W was similar to 2.5 mol C m(-2) yr(-1). Spatial trends in export production coinciding with the New Zealand shelf and Subtropical Front are identified.