Impacts of ocean acidification on intertidal benthic foraminiferal growth and calcification

Foraminifera are expected to be particularly susceptible to future changes in ocean carbonate chemistry as a function of increased atmospheric CO2. Studies in an experimental recirculating seawater system were performed with a dominant benthic foraminiferal species collected from intertidal mudflats. We investigated the experimental impacts of ocean acidification on survival, growth/calcification, morphology and the biometric features of a calcareous species Elphidium williamsoni. Foraminifera were exposed for 6 weeks to four different pH treatments that replicated future scenarios of a high CO2 atmosphere resulting in lower seawater pH. Results revealed that declining seawater pH caused a decline in foraminiferal survival rate and growth/calcification (mainly through test weight reduction). Scanning electron microscopy image analysis of live specimens at the end of the experimental period show changes in foraminiferal morphology with clear signs of corrosion and cracking on the test surface, septal bridges, sutures and feeding structures of specimens exposed to the lowest pH conditions. These findings suggest that the morphological changes observed in shell feeding structures may serve to alter: (1) foraminiferal feeding efficiency and their long-term ecological competitiveness, (2) the energy transferred within the benthic food web with a subsequent shift in benthic community structures and (3) carbon cycling and total CaCO3 production, both highly significant processes in coastal waters. These experimental results open-up the possibility of modelling future impacts of ocean acidification on both calcification and dissolution in benthic foraminifera within mid-latitude intertidal environments, with potential implications for understanding the changing marine carbon cycle

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Sedimentation rates and foraminiferal assemblages from ODP Site 162-184

Sedimentological and faunal records from the transitional period marking the onset of widespread northern hemisphere glaciation have been investigated at Ocean Drilling Program Site 984. The late Pliocene interglacial sediments of the northeast Atlantic are carbonate rich and show evidence of vigorous bottom water circulation at intermediate water depths. Contrasting this, the late Pliocene glacial sediments are characterised by carbonate dissolution and slower bottom current velocities. Weak or "leaky" Norwegian Sea overflows, undersaturated with respect to carbonate, influenced this region during the late Pliocene glacials. The early Pleistocene pattern of intermediate water circulation appears to have changed radically in the northeast Atlantic. At this time, interglacial carbonate values and inferred bottom current velocities are low. This suggests slow-flowing, undersaturated Norwegian Sea water bathing the site. The overflow increased during the early Pleistocene interglacials as the exchange between the Atlantic and Norwegian-Greenland Seas improved. The most significant feature of the early Pleistocene glacials is the increase in inferred bottom current velocity. These changes reflect a switch in deep North Atlantic convection to shallower depths during glacial periods, possibly in a manner similar to the increasing contribution of glacial intermediate water to the North Atlantic during the late Pleistocene glacials. Our results suggest that the late Pleistocene climate variability of the North Atlantic is a pervasive feature of the late Pliocene-early Pleistocene record

(Table 1) Foraminifera abundance of ODP Hole 162-985A sediments

The stratigraphic distribution of deep-water agglutinated foraminifers was examined using 50 samples from Ocean Drilling Program (ODP) Hole 985A, drilled on the gentle slope of the Iceland Plateau in the Norwegian Basin. A total of 40 species and generic groupings was determined in this study. Three stratigraphically meaningful assemblages are recognized in Hole 985A: a basal assemblage with coarsely agglutinated forms (Cores 162-985A-62X through 50X), a Spirosigmoilinella compressa assemblage (Cores 162-985A-49X through 40X), and a sparse assemblage with pyritized radiolarians in the uppermost part of the studied interval (Cores 162-985A-39X through 32X). The whole succession from the base of Hole 985A to Core 162-985A-32X is here assigned to the Dorothia siegliei-Rotaliatina bulimoides Zone of Oligocene age. The stratigraphic ranges of several species extended into younger strata compared with biostratigraphic records from the Vøring Slope (ODP Hole 643A) and from an exploration well on the Vøring Plateau. Taxonomic differences between the foraminiferal records of the Norwegian Sea and the deep Labrador Sea provide evidence for faunal isolation of the deep Norwegian basin during the Oligocene. This isolation is attributed to limited marine connections across the Greenland-Scotland Ridge, resulting in Norwegian Sea deep water that was corrosive and poorly ventilated. Foraminiferal evidence suggests that Norwegian Sea deep water was poorly oxygenated during the Oligocene

Size matter of betnhic foraminifera counts

Benthic foraminifera counts for small and large size fractio