Archive for August, 2012

The current rate of ocean acidification has no precedent in 300 million years of Earth history

Peering into the past can help us to discern the future. But, when it comes to ocean acidification, past events may offer little indication of what is in store.

A third to a half of all the carbon dioxide that humans have released into the atmosphere has been absorbed by the ocean. Once dissolved in seawater, CO2 forms carbonic acid, which not only lowers the pH of the ocean – that is, makes it more acidic – but also decreases the availability of Carbonate ions (CO32-) to organisms that need it to grow Calcium Carbonate (CaCO3) shells. Laboratory studies have shown that many organisms at the base of the marine food web suffer from reduced shell formation in acidified conditions – conditions that may become typical during this century. In other words, ocean acidification threatens the very foundation of the marine ecosystem.

Continue reading ‘The current rate of ocean acidification has no precedent in 300 million years of Earth history’

Mesozooplankton community development at elevated CO2 concentrations: results from a mesocosm experiment in an Arctic fjord

The increasing CO2 concentration in the atmosphere caused by burning fossil fuels leads to increasing pCO2 and decreasing pH in the world oceans. These changes may have severe consequences for marine biota, especially in cold-water ecosystems due to higher solubility of CO2. However, studies on the response of mesozooplankton communities to elevated pCO2 are yet lacking. In order to test whether abundance and taxonomic composition change with pCO2, we have sampled nine mesocosms, which were deployed in Kongsfjorden, an Arctic fjord at Svalbard, and were adjusted to eight CO2 concentrations, initially ranging from 185 μatm to 1420 μatm. Samples were taken weekly over a six-week period with an Apstein net (55 μm mesh size) in all mesocosms and the surrounding fjord. In addition, sediment trap samples, taken every second day in the mesocosms, were analyzed to account for losses due to vertical migration and mortality. The taxonomic analysis revealed that meroplanktonic larvae (cirripeds, polychaetes, bivalves, gastropod, and decapods) dominated in the mesocosms while copepods (Calanus spp., Oithona similis, Acartia longiremis and Microsetella norvegica) were found in lower abundances. In the fjord copepods prevailed for most of our study. With time, abundance and taxonomic composition developed similarly in all mesocosms; the pCO2 had no significant effect on the overall community structure. However, single taxa responded to elevated CO2concentrations. The ratio of cirripedia nauplii to cypris larvae, the next developmental stage, in the sediment traps averaged over the entire experiment increased with pCO2 and this suggests that increased pCO2 may have delayed their development. Also, the number of bivalves, averaged over the experimental period, decreased significantly with increasing pCO2. The nature of the CO2 effect, either direct or indirect, remains open and needs to be addressed in future.

Continue reading ‘Mesozooplankton community development at elevated CO2 concentrations: results from a mesocosm experiment in an Arctic fjord’

A national glider network for sustained observation of the coastal ocean

A national glider network is essential to provide baseline ocean observations to connect the coastal and global ocean, and to address such issues as natural climate variability, ecosystem health, and water quality. The development of gliders is briefly reviewed. Requirements for a national network are presented, and the capabilities of gliders are shown to be suited for the task. The needs of a data management system tuned to gliders are outlined. Planning is underway for a workshop to produce a strategy for a glider network. A document from this workshop will be completed during 2012.

Continue reading ‘A national glider network for sustained observation of the coastal ocean’

Ocean acidification in the Eastern Tropical North Pacific

The oceanic water south of Cabo San Lucas, Mexico is an oxygen minimum zone (OMZ.) OMZs lead to greater concentrations of carbon dioxide in the water. The OMZ near Cabo is expanding, causing an increase in CO2 concentrations and a steadily declining pH in the region. As oceanic pH continues to decline, the water undergoes ocean acidification, causing calcium carbonate (CaCO3) shelled organisms to have increased difficulty forming their shells. In the data collected from the ETNP in late March, 2012, the pH ranged from 7.49 off the coast of San Diego, CA to 7.39 near the center of the OMZ at a depth of 800 meters. More data collection in this region is required to gain an appropriate overview of the effects of ocean acidification on the ecosystem as a whole.

Continue reading ‘Ocean acidification in the Eastern Tropical North Pacific’

Late Campanian-Maastrichtian planktic foraminiferal biostratigraphy, taxonomy, and isotope paleoecology of ODP Leg 198 Sites 1209 and 1210, Shatsky Rise

Well-preserved and diverse assemblages of late Campanian-Maastrichtian age (76.5-65.5 Ma) planktic foraminifera from Ocean Drilling Program Sites 1209 and 1210 on Shatsky Rise provide an excellent source of data to better understand the environmental and biotic changes of the end-Cretaceous Period in the tropical Pacific. A thorough taxonomic and biostratigraphic study of planktic foraminifera has revealed significant differences in species ranges when compared to detailed studies from the western North Atlantic and eastern South Atlantic. These observations are attributed to site locations with different ocean current and productivity conditions.

During the globally recognized “mid-Maastrichtian Event”, inoceramid clams, rare at Shatsky Rise, dramatically increased (~69.3 Ma) before suddenly going extinct (69.1 Ma). This Inoceramid Acme Event (IAE), occurs during high sedimentation rates (~21.8-m/myr) and is indicated in planktic foraminifera by a 0.50‰ positive shift in δ18O values (~2 °C cooling), a 0.24‰ negative shift in δ13C values of and high species richness. A simultaneous decrease in both the δ18O and δ13C gradients between surface and thermocline dwelling planktic foraminifera indicate the IAE was possibly initiated by an increase in surface productivity due to the upwelling of cooler, nutrient-rich waters.

A dissolution event was identified at ~66.1 Ma lasting to the Cretaceous/Paleogene boundary (65.5 Ma) and is characterized by chalky, highly fragmented planktic foraminifera, increased dissolution of larger Globotruncanids, increased small (< 63 μm) planktic foraminifera, large and increasingly abundant benthic foraminifera, a sharp decrease in species richness and increased sedimentation rates (~19.9-m/myr). This event follows a transitional interval at ~66.7 Ma where preservation is highly variable. The dissolution event, reported in previous studies at Shatsky Rise (Caron, 1975; Premoli Silva et al., 2005), is not reported in the North and South Atlantic but may help to explain the high diachroneity in species occurrences between ocean basins. These events may indicate that the calcite carbonate compensation depth (CCD) shoaled to shallower depths than previously reported (Theirstein, 1979) due to changing deep or intermediate water mass sources. Alternatively, the timing the dissolution is approximately coincident with the main pulse of Deccan Trap volcanism on the Indian subcontinent suggesting a possible link through ocean acidification.

Continue reading ‘Late Campanian-Maastrichtian planktic foraminiferal biostratigraphy, taxonomy, and isotope paleoecology of ODP Leg 198 Sites 1209 and 1210, Shatsky Rise’

The effect of dosing with sodium hydroxide (NaOH−) on water pH and growth of Haliotis midae in an abalone serial-use raceway

Abalone culture systems are characterised by high water exchange rates as abalone are sensitive to changes in water quality. To reduce the costs of pumping, serial reuse systems have been tested. As water pH can decline in these systems, this study determined the effect of raising pH through the addition of sodium hydroxide (NaOH) on weight gain, length gain and feed conversion ratio of H. midae in a serial-use raceway. Dosing with NaOH increased pH by 0.3, 0.27 and 0.21 units at positions 1, 2 and 3 of a serial-pass system, respectively. Weight gain (Wg) and length gain (Lg) were correlated with pH (Wg: F 1, 16 = 16.35, P = 0.0009, r 2 = 0.51; Lg: F 1, 16 = 16.16, P = 0.0009, r 2 = 0.50), and using pH, dissolved oxygen and free ammonia nitrogen as independent variables suggested that water pH was the best predictor for abalone growth.

Continue reading ‘The effect of dosing with sodium hydroxide (NaOH−) on water pH and growth of Haliotis midae in an abalone serial-use raceway’

Effects of water temperature and pH on growth and metabolite biosynthesis of coral reef sponges

Warmer, more acidic water resulting from increased emissions of greenhouse gases will impact coral reef organisms, but the effects remain unknown for many dominant groups such as sponges. To test for possible effects, adult sponges of 6 common Caribbean coral reef species—Aiolochroia crassa, Aplysina cauliformis, Aplysina fistularis, Ectyoplasia ferox, Iotrochota birotulata and Smenospongia conulosa—were grown for 24 d in seawater ranging from values experienced at present-day summer-maxima (temperature = 28°C; pH = 8.1) to those predicted for the year 2100 (temperature = 31°C; pH = 7.8). For each species, growth and survival were similar among temperature and pH levels. Sponge attachment rates, which are important for reef consolidation, were similar between pH values for all species, and highest at 31°C for E. ferox, I. birotulata and A. cauliformis. Secondary metabolites, responsible for deterring predation and fouling, were examined for A. crassa, A. cauliformis, E. ferox and I. birotulata, with 1 to 3 major metabolites quantified from each species. Final metabolite concentrations varied significantly among treatments only for zooanemonin from E. ferox and N-tele-methylhistamine from I. birotulata, but these concentrations were similar to those found in wild conspecifics. Considering adult sponges only, these findings suggest that the ecological roles and physiological processes of the 6 coral reef species will be little affected by the mean values of water temperature and pH predicted for the end of the century.

Continue reading ‘Effects of water temperature and pH on growth and metabolite biosynthesis of coral reef sponges’

Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions (update)

Emiliania huxleyi (strain B 92/11) was exposed to different nutrient supply, CO2 and temperature conditions in phosphorus controlled chemostats to investigate effects on organic carbon exudation and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC).14C incubation measurements for primary production (PP) and extracellular release (ER) were performed. Chemical analysis included the amount and composition of high molecular weight (>1 kDa) dissolved combined carbohydrates (HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO2 and temperature conditions were 300, 550 and 900 μatmpCO2 at 14 °C, and additionally 900 μatm pCO2 at 18 °C simulating a greenhouse ocean scenario.

Enhanced nutrient stress by reducing the dilution rate (D) from D = 0.3 d−1to D = 0.1 d−1 (D = μ) induced the strongest response in E. huxleyi. At μ = 0.3 d−1, PP was significantly higher at elevated CO2 and temperature and DO14C production correlated to PO14C production in all treatments, resulting in similar percentages of extracellular release (PER; (DO14C production/PP) × 100) averaging 3.74 ± 0.94%. At μ = 0.1 d−1, PO14C production decreased significantly, while exudation of DO14C increased. Thus, indicating a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 ± 2.3% were observed at μ = 0.1 d−1at elevated CO2 and temperature.

While cell densities remained constant within each treatment and throughout the experiment, concentrations of HMW-dCCHO, pCCHO and TEP were generally higher under enhanced nutrient stress. At μ = 0.3 d−1, pCCHO concentration increased significantly with elevated CO2 and temperature. At μ = 0.1 d−1, the contribution (mol % C) of HMW-dCCHO to DOC was lower at elevated CO2 and temperature while pCCHO and TEP concentrations were higher. This was most pronounced under greenhouse conditions. Our findings suggest a stronger transformation of primary produced DOC into POC by coagulation of exudates under nutrient limitation. Our results further imply that elevated CO2 and temperature will increase exudation by E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.

Continue reading ‘Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions (update)’

ELEMENTS: Scientists track ocean acidity in Arctic

A team of scientists will sail through Arctic ice to test the chemistry of the worlds northernmost waters.

A couple years ago Scripps Institution of Oceanography held an international paleocanography conference, featuring keynote speaker Ken Caldeira, whose description of ocean acidification became a linchpin of research documenting rising global temperatures.

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Ocean acidification: a systems approach to a global problem

In this curriculum module, students in high school life and marine science courses act as interdisciplinary scientists and delegates to investigate how the changing carbon cycle will affect the oceans along with their integral populations.

Continue reading ‘Ocean acidification: a systems approach to a global problem’

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Ocean acidification in the IPCC AR5 WG II

OUP book