To document the status and progress of ocean acidification in open-ocean and coastal environments and to understand its drivers and impacts on marine ecosystems, it will be necessary to develop a coordinated multidisciplinary multinational approach for observations. In partnership with the NOAA Ocean Acidification Program, the International Ocean Carbon Coordination Project, and the Global Ocean Observing System, the University of Washington is hosting a workshop on June 26-28th to take steps to develop a global ocean acidification monitoring network.
Archive for June 1st, 2012
Working Group II (WGII) of the Intergovernmental Panel on Climate Change (IPCC) is pleased to announce that the first-order drafts of its contribution to the IPCC Fifth Assessment Report (AR5), Climate Change 2013: Impacts, Adaptation, and Vulnerability, will be available for formal review from 11 June to 6 August 2012. The WGII Technical Support Unit (TSU) is accepting pre-registrations for the Expert Review until 10 June 2012.
Growth of cultured giant clams (Tridacna spp.) in low pH, high-nutrient seawater: species-specific effects of substrate and supplemental feeding under acidificationPublished 1 June 2012 Science Leave a Comment
Tags: biological response, calcification, laboratory, molluscs, South Pacific
Four species of giant clams, Tridacna maxima, T. squamosa, T. derasa and T. crocea, were cultured in outdoor raceways for 364 days at the Waikīkī Aquarium and the Oceanic Institute on the island of O‘ahu, Hawai‘i, USA. Growth of each species was compared among individuals grown with and without supplemental phytoplankton feeding, and directly on the substrate or mounted on concrete plugs in low pH, high nutrient seawater. Among clams cultured with and without supplemental phytoplankton (Chaetoceros spp.), feeding resulted in significantly lower mortality in all species but T. deresa, whereas growth was significantly higher among fed clams for all species except T. squamosa. Tridacna derasa showed roughly a three-fold increase in growth when fed (88.5 g ± 4.4 SD) than when unfed (26.0 g ± 2.1 SD), whereas T. maxima growth was substantially lower, but nearly 10-fold greater in response to feeding (9.0 g ± 1.9 SD). The overall mortality rate of juvenile clams was significantly lower in the fed (44.4 ± 10.0%) than the unfed (71.8 ± 9.6%) trials, with the greatest effect observed in mortality of T. maxima (fed 15% versus unfed 80%) and T. squamosa (fed 65% versus unfed 95%). None of the T. squamosa remained on concrete plugs for the duration of the experiment. Among the remaining three species, there was no difference in either wet weight or shell length for T. maxima and for wet weight only in T. derasa on (186.5 g ± 16.1 SD) and off (147.0 g ± 6.0 SD) the concrete plugs. In contrast, T. crocea had significantly greater shell growth off the plugs (14.3 mm ± 1.0 SD versus 8.5 mm ± 1.7 SD) but significantly greater gain in wet weight on the concrete plugs (26.3 g ± 1.5 SD versus 58.5 g ± 2.5 SD). The seawater wells used for this study are well characterized with elevated levels of inorganic nutrients and higher pCO2 relative to tropical ocean waters, roughly approximating predictions for future oceanic conditions under IPCC IS92a emission scenarios. In comparison to previous studies in natural seawater, T. derasa had a significantly higher shell growth rate in the high-nutrient, low-pH well water. In contrast, T. maxima and T. squamosa had significantly lower growth rates in low pH, whereas growth of T. crocea was not significantly different between low pH and ambient seawater. These experiments demonstrate species-specific differences with each treatment, which cautions against making broad generalizations regarding the effects of substrate type, feeding effects, nutrient enrichment, and ocean acidification on tridacnid culture and survival.
The Early Eocene Thermal Maximum 2 (ETM2) at ~53.7 Ma is one of multiple hyperthermal events that followed the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma). The negative carbon excursion and deep ocean carbonate dissolution which occurred during the event imply that a substantial amount (103 Gt) of carbon (C) was added to the ocean-atmosphere system, consequently increasing atmospheric CO2 (pCO2). This makes the event relevant to the current scenario of anthropogenic CO2 additions and global change. Resulting changes in ocean stratification and pH, as well as changes in exogenic cycles which supply nutrients to the ocean, may have affected the productivity of marine phytoplankton, especially calcifying phytoplankton. Changes in productivity, in turn, may affect the rate of sequestration of excess CO2 in the deep ocean and sediments. In order to reconstruct the productivity response by calcareous nannoplankton to ETM2 in the South Atlantic (Site 1265) and North Pacific (Site 1209), we employ the coccolith Sr/Ca productivity proxy with analysis of well-preserved picked monogeneric populations by ion probe supplemented by analysis of various size fractions of nannofossil sediments by ICP-AES. The former technique of measuring Sr/Ca in selected nannofossil populations using the ion probe circumvents possible contamination with secondary calcite. Avoiding such contamination is important for an accurate interpretation of the nannoplankton productivity record, since diagenetic processes can bias the productivity signal, as we demonstrate for Sr/Ca measurements in the fine (