Carbonates are used extensively to reconstruct paleoclimate and paleoceanographic conditions over geologic time scales. However, these archives are susceptible to diagenetic alteration via dissolution, recrystallization and secondary precipitation, particularly during ocean acidification events when intense dissolution can occur. Despite the possible effects of diagenesis on proxy fidelity, the impacts of diagenesis on the calcium isotopic composition (δ44Ca) of carbonates are unclear. To shed light on this issue, bulk carbonate δ44Ca was measured at high resolution in two Pacific deep sea sediment cores (ODP Sites 1212 and 1221) with considerably different dissolution histories over the Paleocene–Eocene Thermal Maximum (PETM, ∼55 Ma∼55 Ma). The δ44Ca of marine barite was also measured at the deeper Site 1221, which experienced severe carbonate dissolution during the PETM. Large variations (∼0.8‰∼0.8‰) in bulk carbonate δ44Ca occur in the deeper of the two sites at depths corresponding to the peak carbon isotope excursion, which correlate with a large drop in carbonate weight percent. Such an effect is not observed in either the 1221 barite record or the bulk carbonate record at the shallower Site 1212, which is also less affected by dissolution. We contend that ocean chemical changes associated with abrupt and massive carbon release into the ocean–atmosphere system and subsequent ocean acidification at the PETM affected the bulk carbonate δ44Ca record via diagenesis in the sedimentary column. Such effects are considerable, and need to be taken into account when interpreting Ca isotope data and, potentially, other geochemical proxies over extreme climatic events that drive sediment dissolution.
Effects of ocean acidification on the marine calcium isotope record at the Paleocene–Eocene Thermal MaximumPublished 27 March 2015 Science Leave a Comment
Tags: biological response, laboratory, mollusks, morphology, mortality, reproduction
Increasing atmospheric CO2 can decrease seawater pH and carbonate ions, which may adversely affect the larval survival of calcareous animals. In this study, we simulated future atmospheric CO2 concentrations (800, 1500, 2000 and 3000 ppm) and examined the effects of ocean acidification on the early development of 3 mollusks (the abalones Haliotis diversicolor and H. discus hannai and the oyster Crassostrea angulata). We showed that fertilization rate, hatching rate, larval shell length, trochophore development, veliger survival and metamorphosis all decreased significantly at different pCO2 levels (except oyster hatching). H. discus hannai were more tolerant of high CO2 compared to H. diversicolor. At 2000 ppm CO2, 79.2% of H. discus hannai veliger larvae developed normally, but only 13.3% of H. diversicolor veliger larvae. Tolerance of C. angulata to ocean acidification was greater than the 2 abalone species; 50.5% of its D‑larvae developed normally at 3000 ppm CO2. This apparent resistance of C. angulata to ocean acidification may be attributed to their adaptability to estuarine environments. Mechanisms underlying the resistance to ocean acidification of both abalones requires further investigation. Our results suggest that ocean acidification may decrease the yield of these 3 economically important shellfish if increasing CO2 is a future trend.
Last Wednesday afternoon, a group of scientists and a handful of lucky onlookers crowded around a heap of computer monitors onboard a NOAA research vessel in between Santa Cruz and Anacapa islands. In the middle of this scrum were two men controlling a remotely operated vehicle (ROV) 500 feet beneath the boat’s hull.
Later in the day, an oceanographer named Peter Etnoyer would ruminate on the fact that when he was in college, researchers still believed that the deep sea consisted of dead zones devoid of life; however, the ROV’s electrical eyes revealed an ecosystem teeming with fish, crustaceans, and the organism that nobody knew actually existed in the Santa Barbara Channel until recently: coral.
Everyone held their breath as they watched the ROV clamp onto a pink gorgonian coral bush, more commonly known as a sea fan, and deposit it onto the submersible’s “front porch.” Exhales. Applause. Soon after, scientists and their assistants were slicing and dicing the specimen so it could be preserved for examination. The abiding question is how deep-sea corals are impacted by ocean acidification.
A University of Colorado Boulder study shows a ubiquitous type of phytoplankton — tiny organisms that are the base of the marine food web – appears to be suffering from the effects of ocean acidification caused by climate change.
According to the study authors, the single-celled organism under study is a type of “calcifying” plankton called a coccolithophore, which makes energy from sunlight and builds microscopic calcium carbonate shells, or plates, to produce a chalky suit of armor. The researchers used satellites tuned to observe the amount of calcium carbonate present in the surface of the Southern Ocean produced by Emiliania huxleyi, one of the most common species of coccolithophores in the region.
The coccolithophore E. huxleyi is important in the marine carbon cycle and is responsible for nearly half of all calcium carbonate production in the ocean, said lead study author Natalie Freeman, a doctoral student in the CU-Boulder’s Department of Atmospheric and Oceanic Sciences (ATOC). The new study indicates there has been a 24 percent decline in the amount of calcium carbonate produced in large areas of the Southern Ocean over the past 17 years.
The researchers used satellite measurements and statistical methods to calculate the calcification rate – the amount of calcium carbonate these organisms produced per day in surface ocean waters. Across the entire Southern Ocean, which surrounds Antarctica, there was about a 4 percent reduction in calcification rate during the summer months from 1998 to 2014. In addition, the researchers found a 9 percent reduction in calcification during that period in large regions of the Pacific and Indian sectors of the Southern Ocean.
Job no: 493373
Work type: Fixed term – Full-time
Categories: Faculty of Sciences
Closing date: 10 April 2015
The University of Adelaide is one of Australia’s leading Group of Eight, research-intensive universities and is consistently ranked among the top 1% of universities in the world. Established in 1874, it is Australia’s third oldest university with a strong reputation for preparing educated leaders and delivering research outcomes that contribute to local, national and global wellbeing.
The Faculty of Sciences is one of five faculties at the University of Adelaide. As the first university in Australia to grant degrees in science (1882), science has long been at the cornerstone of the institution and this continues today. As a research and education leader in fields such as biomedical sciences, agricultural, environmental and earth sciences, and photonics, the faculty offers an exciting and innovative work environment.
Tags: biological response, fish, fisheries, individualmodeling, modeling, mortality, reproduction, socio-economy
Ocean Acidification (OA) will influence marine ecosystems by changing species abundance and composition. Major effects are described for calcifying organisms, which are significantly impacted by decreasing pH values. Direct effects on commercially important fish are less well studied. The early life stages of fish populations often lack internal regulatory mechanisms to withstand the effects of abnormal pH. Negative effects can be expected on growth, survival, and recruitment success. Here we study Norwegian coastal cod, one of the few stocks where such a negative effect was experimentally quantified, and develop a framework for coupling experimental data on OA effects to ecological-economic fisheries models. In this paper, we scale the observed physiological responses to the population level by using the experimentally determined mortality rates as part of the stock-recruitment relationship. We then use an ecological-economic optimization model, to explore the potential effect of rising CO2 concentration on ecological (stock size), economic (profits), consumer-related (harvest) and social (employment) indicators, with scenarios ranging from present day conditions up to extreme acidification. Under the assumptions of our model, yields and profits could largely be maintained under moderate OA by adapting future fishing mortality (and related effort) to changes owing to altered pH. This adaptation comes at the costs of reduced stock size and employment, however. Explicitly visualizing these ecological, economic and social tradeoffs will help in defining realistic future objectives. Our results can be generalized to any stressor (or stressor combination), which is decreasing recruitment success. The main findings of an aggravation of trade-offs will remain valid. This seems to be of special relevance for coastal stocks with limited options for migration to avoid unfavorable future conditions and subsequently for coastal fisheries, which are often small scale local fisheries with limited operational ranges.
West Coast governors are working to arrange a meeting with senior officials in the White House and federal agencies to push for more spending on research into the problem, which has hit the region’s shellfish industry. The world’s oceans absorb an increasing amount of carbon dioxide from the burning of fossil fuels, and that corrosive water can prevent oyster and clam larvae from developing shells.