Biogeochemistry of Paleozoic brachiopods from New York State and Ontario

A comprehensive elemental, isotopic and microstructural analyses was undertaken of brachiopod calcites from the Hamilton Group (Middle Devonian), Clinton Group (Middle Silurian) and Middle to Upper Ordovician strata of Ontario and New York State. The majority of specimens were microstructurally and chemically preserved in a pristine state, although a number of specimens show some degree of post-depositional alteration. Brachiopod calcites from the Hamilton and Clinton Groups were altered by marine derived waters whereas Trenton Group (Middle Ordovician) brachiopods altered in meteorically derived fluids. Analysis of the elemental and isotopic compositions of pristine Hamilton Group brachiopods indicates there are several chemical relationships inherent to brachiopod calcite. Taxonomic differentiation of Mg, Sr and Na contents was evident in three co-occuring species from the Hamilton Group. Mean Mg contents of pristine brachiopods were respectively Athyris spiriferoides (1309ppm), Mucrospirifer mucronatus (1035ppm) and Mediospirifer audacula (789ppm). Similarly, taxonomic differentiation of shell calcite compositions was observed in co-occuring brachiopods from the Clinton Group (Middle Silurian) and the Trenton Group (Middle Ordovician). The taxonomic control of elemental regulation into shell calcite is probably related to the slightly different physiological systems and secretory mechanisms. A relationship was observed in Hamilton Group species between the depth of respective brachiopod communities and their Mg, Sr and Na contents. These elements were depleted in the shell calcites of deeper brachiopods compared to their counterparts in shallower reaches. Apparently shell calcite elemental composition is related to environmental conditions of the depositional setting, which may have controlled the secretory regime, mineral morphology of shell calcite and precipitation rates of each species. Despite the change in Mg, Sr and Na contents between beds and formations in response to environmental conditions, the taxonomic differentiation of shell calcite composition is maintained. Thus, it may be possible to predict relative depth changes in paleoenvironmental reconstructions using brachiopod calcite. This relationship of brachiopod chemistry to depth was also tested within a transgressiveregressive (T-R) cycle in the Rochester Shale Formation (Middle Silurian). Decreasing Mg, Sr and Na contents were observed in the transition from the shallow carbonates of the Irondequoit Formation to the deeper shales of the lowest 2 m of Rochester Shale. However, no isotopic and elemental trends were observed within the entire T-R cycle which suggests that either the water conditions did not change significantly or that the cycle is illusory. A similar relationship was observed between the Fe and Mn chemistries of shell calcite and redox/paleo-oxygen conditions. Hamilton Group brachiopods analysed from deeper areas of the shelf are enriched in Mn and Fe relative to those from shallow zones. The presence of black shales and dysaerobic faunas, during deposition of the Hamilton Group, suggests that the waters of the northern Appalachian Basin were stratified. The deeper brachiopods were marginally positioned above an oxycline and their shell calcites reflect periodic incursions of oxygen depleted water. Furthermore, analysis of Dalmanella from the black shales of the Collingwood Shale (Upper Ordovician) in comparison to those from the carbonates of the Verulam Formation (Middle Ordovician) confirm the relationship of Fe and Mn contents to periodic but not permanent incursions of low oxygen waters. The isotopic compositions of brachiopod calcite found in Hamilton Group (813C; +2.5% 0 to +5.5% 0; 8180 -2.50/00 to -4.00/00) and Clinton Group (813C; +4.00/00 to +6.0; 8180; -1.8% 0 to -3.60/ 00) are heavier than previously reported. Uncorrected paleotemperatures (assuming normal salinity, 0% 0 SMOW and no fractionation effects) derived from these isotopic values suggest that the Clinton sea temperature (Middle Silurian) ranged from 18°C to 28°C and Hamilton seas (Middle Devonian) ranged between 24°C and 29°C. In addition, the isotopic variation of brachiopod shell calcite is significant and is related to environmental conditions. Within a single time-correlative shell bed (the Demissa Bed; Hamilton Group) a positive isotopic shift of 2-2.5% 0 in 013C compositions and a positive shift of 1.0-1.50/00 in 0180 composition of shell calcite is observed, corresponding with a deepening of brachiopod habitats toward the axis of the Appalachian Basin. Moroever, a faunal succession from deeper Ambocoelia dominated brachiopod association to a shallow Tropidoleptus dominated assocation is reflected by isotopic shifts of 1.0-1.50/00. Although, other studies have emphasized the significance of ±20/oo shifts in brachiopod isotopic compositions, the recognition of isotopic variability in brachiopod calcite within single beds and within depositional settings such as the Appalachian Basin has important implications for the interpretation of secular isotopic trends. A significant proportion of the variation observed isotopic distribution during the Paleozoic is related to environmental conditions within the depositional setting

Formation and transport of corrosive water in the Pacific Arctic region

This paper is not subject to U.S. copyright. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 152 (2018): 67-81, doi:10.1016/j.dsr2.2018.05.020.Ocean acidification (OA), driven by rising anthropogenic carbon dioxide (CO2), is rapidly advancing in the Pacific Arctic Region (PAR), producing conditions newly corrosive to biologically important carbonate minerals like aragonite. Naturally short linkages across the PAR food web mean that species-specific acidification stress can be rapidly transmitted across multiple trophic levels, resulting in widespread impacts. Therefore, it is critical to understand the formation, transport, and persistence of acidified conditions in the PAR in order to better understand and project potential impacts to this delicately balanced ecosystem. Here, we synthesize data from process studies across the PAR to show the formation of corrosive conditions in colder, denser winter-modified Pacific waters over shallow shelves, resulting from the combination of seasonal terrestrial and marine organic matter respiration with anthropogenic CO2. When these waters are subsequently transported off the shelf, they acidify the Pacific halocline. We estimate that Barrow Canyon outflow delivers ~2.24 Tg C yr-1 to the Arctic Ocean through corrosive winter water transport. This synthesis also allows the combination of spatial data with temporal data to show the persistence of these conditions in halocline waters. For example, one study in this synthesis indicated that 0.5–1.7 Tg C yr-1 may be returned to the atmosphere via air-sea gas exchange of CO2 during upwelling events along the Beaufort Sea shelf that bring Pacific halocline waters to the ocean surface. The loss of CO2 during these events is more than sufficient to eliminate corrosive conditions in the upwelled Pacific halocline waters. However, corresponding moored and discrete data records indicate that potentially corrosive Pacific waters are present in the Beaufort shelfbreak jet during 80% of the year, indicating that the persistence of acidified waters in the Pacific halocline far outweighs any seasonal mitigation from upwelling. Across the datasets in this large-scale synthesis, we estimate that the persistent corrosivity of the Pacific halocline is a recent phenomenon that appeared between 1975 and 1985. Over that short time, these potentially corrosive waters originating over the continental shelves have been observed as far as the entrances to Amundsen Gulf and M’Clure Strait in the Canadian Arctic Archipelago. The formation and transport of corrosive waters on the Pacific Arctic shelves may have widespread impact on the Arctic biogeochemical system and food web reaching all the way to the North Atlantic.National Science Foundation Grant PLR-1303617

Adaptive carbon export response to warming in the Sargasso Sea

Ocean ecosystem models predict that warming and increased surface ocean stratification will trigger a series of ecosystem events, reducing the biological export of particulate carbon to the ocean interior. We present a nearly three-decade time series from the open ocean that documents a biological response to ocean warming and nutrient reductions wherein particulate carbon export is maintained, counter to expectations. Carbon export is maintained through a combination of phytoplankton community change to favor cyanobacteria with highcellular carbon-to-phosphorus ratios and enhanced shallow phosphorus recycling leading to increased nutrient use efficiency. These results suggest that surface ocean ecosystems may be more responsive and adapt more rapidly to changes in the hydrographic system than is currently envisioned in earth ecosystem models, with positive consequences for ocean carbon uptake

Revising upper-ocean sulfur dynamics near Bermuda : new lessons from 3 years of concentration and rate measurements

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Environmental Chemistry 13 (2016): 302-313, doi:10.1071/EN15045.Oceanic biogeochemical cycling of dimethylsulfide (DMS), and its precursor dimethylsulfoniopropionate (DMSP), has gained considerable attention over the past three decades because of the potential role of DMS in climate mediation. Here we report 3 years of monthly vertical profiles of organic sulfur cycle concentrations (DMS, particulate DMSP (DMSPp) and dissolved DMSP (DMSPd)) and rates (DMSPd consumption, biological DMS consumption and DMS photolysis) from the Bermuda Atlantic Time-series Study (BATS) site taken between 2005 and 2008. Concentrations confirm the summer paradox with mixed layer DMS peaking ~90 days after peak DMSPp and ~50 days after peak DMSPp : Chl. A small decline in mixed layer DMS was observed relative to those measured during a previous study at BATS (1992–1994), potentially driven by long-term climate shifts at the site. On average, DMS cycling occurred on longer timescales than DMSPd (0.43 ± 0.35 v. 1.39 ± 0.76 day–1) with DMSPd consumption rates remaining elevated throughout the year despite significant seasonal variability in the bacterial DMSP degrader community. DMSPp was estimated to account for 4–5 % of mixed layer primary production and turned over at a significantly slower rate (~0.2 day–1). Photolysis drove DMS loss in the mixed layer during the summer, whereas biological consumption of DMS was the dominant loss process in the winter and at depth. These findings offer new insight into the underlying mechanisms driving DMS(P) cycling in the oligotrophic ocean, provide an extended dataset for future model evaluation and hypothesis testing and highlight the need for a reexamination of past modelling results and conclusions drawn from data collected with old methodologies.The authors acknowledge funding from the National Science Foundation (NSF) (OCE-0425166) and the Center for Microbial Oceanography Research and Education (CMORE) a NSF Science and Technology Center (EF-0424599)

Calcification and trophic responses of mesophotic reefs to carbonate chemistry variability

Mesophotic coral ecosystems (MCEs) are extensions of adjacent shallow water coral reefs. Accessibility to these ecosystems is challenging due to their depth limits (~ 30 – 150 m) and as a result, scientific knowledge of these reef systems is limited. It has been posited that the depth limits of MCEs diminish anthropogenic effects experienced by shallow reef systems. A lack of empirical measurements to date has made this hypothesis impossible to determine for mesophotic reef metabolism. The alkalinity anomaly technique was utilized to determine rates of net ecosystem calcification (NEC) and net ecosystem production (NEP) from 30, 40 and 60 m mesophotic reefs during a 15-month period. Seawater chemistry was determined to be chemically conducive for calcification (average aragonite saturation Ωaragonite of 3.58, average calcite saturation Ωcalcite of 5.44) with estimates of NEC indicating these reef systems were net accretive and within global average values for shallow coral reefs ( gross CaCO3 dissolution). The measured inorganic carbon chemistry and estimates of NEC and NEP represent the first such biogeochemical measurements for MCEs. The values established by this study demonstrate just how close these understudied ecosystems are in terms of the known boundary thresholds for low saturation state reefs. Making predictions on how these ecosystems will respond to future climatic conditions, will require greater sampling effort over long times scales to decouple the environmental controls exerted on such ecosystems

The influence of winter water on phytoplankton blooms in the Chukchi Sea

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 118 (2015): 53-72, doi:10.1016/j.dsr2.2015.06.006.The flow of nutrient-rich winter water (WW) through the Chukchi Sea plays an important and previously uncharacterized role in sustaining summer phytoplankton blooms. Using hydrographic and biogeochemical data collected as part of the ICESCAPE program (June-July 2010-11), we examined phytoplankton bloom dynamics in relation to the distribution and circulation of WW (defined as water with potential temperature ≤ -1.6°C) across the Chukchi shelf. Characterized by high concentrations of nitrate (mean: 12.3 ± 5.13 μmol L-1) that typically limits primary production in this region, WW was correlated with extremely high phytoplankton biomass, with mean chlorophyll a concentrations that were three-fold higher in WW (8.64 ± 9.75 μg L-1) than in adjacent warmer water (2.79 ± 5.58 μg L-1). Maximum chlorophyll a concentrations (~30 μg L-1) were typically positioned at the interface between nutrient-rich WW and shallower, warmer water with more light availability. Comparing satellite-based calculations of open water duration to phytoplankton biomass, nutrient concentrations, and oxygen saturation revealed widespread evidence of under-ice blooms prior to our sampling, with biogeochemical properties indicating that blooms had already terminated in many places where WW was no longer present. Our results suggest that summer phytoplankton blooms are sustained for a longer duration along the pathways of nutrient-rich WW and that biological hotspots in this region (e.g. the mouth of Barrow Canyon) are largely driven by the flow and confluence of these extremely productive pathways of WW that flow across the Chukchi shelf.This material is based upon work supported by the National Aeronautic and Space Administration (NASA) under Grant No. NNX10AF42G and the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0645962 to K.E. Lowry

Ocean circulation and biogeochemistry moderate interannual and decadal surface water pH changes in the Sargasso Sea

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 42 (2015): 4931–4939, doi:10.1002/2015GL064431.The oceans absorb anthropogenic CO2 from the atmosphere, lowering surface ocean pH, a concern for calcifying marine organisms. The impact of ocean acidification is challenging to predict as each species appears to respond differently and because our knowledge of natural changes to ocean pH is limited in both time and space. Here we reconstruct 222 years of biennial seawater pH variability in the Sargasso Sea from a brain coral, Diploria labyrinthiformis. Using hydrographic data from the Bermuda Atlantic Time-series Study and the coral-derived pH record, we are able to differentiate pH changes due to surface temperature versus those from ocean circulation and biogeochemical changes. We find that ocean pH does not simply reflect atmospheric CO2 trends but rather that circulation/biogeochemical changes account for >90% of pH variability in the Sargasso Sea and more variability in the last century than would be predicted from anthropogenic uptake of CO2 alone.Funding to N.F.G. was provided by the University of Hong Kong and the National Research Foundation Singapore under its Singapore NRF Fellowship scheme (National Research Fellow Award NRF-RF2012-03), as administered by the Earth Observatory of Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. S.C.D. and K.A.H. acknowledge support from the National Science Foundation and Woods Hole Oceanographic Institution

Porewater Carbonate Chemistry Dynamics in a Temperate and a Subtropical Seagrass System

Seagrass systems are integral components of both local and global carbon cycles and can substantially modify seawater biogeochemistry, which has ecological ramifications. However, the influence of seagrass on porewater biogeochemistry has not been fully described, and the exact role of this marine macrophyte and associated microbial communities in the modification of porewater chemistry remains equivocal. In the present study, carbonate chemistry in the water column and porewater was investigated over diel timescales in contrasting, tidally influenced seagrass systems in Southern California and Bermuda, including vegetated (Zostera marina) and unvegetated biomes (0–16 cm) in Mission Bay, San Diego, USA and a vegetated system (Thallasia testudinium) in Mangrove Bay, Ferry Reach, Bermuda. In Mission Bay, dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited strong increasing gradients with sediment depth. Vertical porewater profiles differed between the sites, with almost twice as high concentrations of DIC and TA observed in the vegetated compared to the unvegetated sediments. In Mangrove Bay, both the range and vertical profiles of porewater carbonate parameters such as DIC and TA were much lower and, in contrast to Mission Bay where no distinct temporal signal was observed, biogeochemical parameters followed the semi-diurnal tidal signal in the water column. The observed differences between the study sites most likely reflect a differential influence of biological (biomass, detritus and infauna) and physical processes (e.g., sediment permeability, residence time and mixing) on porewater carbonate chemistry in the different settings

Randomized trial of erlotinib plus whole-brain radiotherapy for NSCLC patients with multiple brain metastases

Background: Median survival of non-small cell lung cancer (NSCLC) patients with brain metastases is poor. We examined concurrent erlotinib and whole brain radiotherapy (WBRT) followed by maintenance erlotinib in patients with untreated brain metastases, given the potential radiosensitizing properties of erlotinib and its direct effect on brain metastases and systemic activity.Methods: Eighty NSCLC patients with KPS of 70 and greater and multiple brain metastases were randomly assigned to placebo (n = 40) or erlotinib (100mg, n = 40) given concurrently with WBRT (20 Gy in 5 fractions). Following WBRT, patients continued with placebo or erlotinib (150mg) until disease progression. The primary end point was neurological progression-free survival (nPFS); hazard ratios (HRs) were calculated using Cox regression. All P values were two-sided.Results: Fifteen patients (37.5%) from each arm were alive and without neurological progression 2 months after WBRT. Median nPFS was 1.6 months in both arms; nPFS HR 0.95 (95% CI = 0.59 to1.54; P = .84). Median overall survival (OS) was 2.9 and 3.4 months in the placebo and erlotinib arms; HR 0.95 (95% CI = 0.58 to 1.55; P = .83). The frequency of epidermal growth factor receptor (EGFR) mutations was low with only 1 of 35 (2.9%) patients with available samples had activating EGFR-mutations. Grade 3/4 adverse event rates were similar between the two groups (70.0% in each arm), except for rash 20.0% (erlotinib) vs 5.0% (placebo), and fatigue 17.5% vs 35.0%. No statistically significant quality of life differences were found.Conclusions: Our study showed no advantage in nPFS or OS for concurrent erlotinib and WBRT followed by maintenance erlotinib in patients with predominantly EGFR wild-type NSCLC and multiple brain metastases compared to placebo. Future studies should focus on the role of erlotinib with or without WBRT in patients with EGFR mutations.Up to 40% of patients with non-small cell lung cancer (NSCLC) develop brain metastases (BM), which are associated with poor outcome (median survival <5 months) (1–3). Treatment options include whole-brain radiotherapy (WBRT) with or without corticosteroids. Modifying the radiation dose or fractionation or combining radiotherapy with radiosensitizers have not substantially improved prognosis (4–10). More than half of patients treated with WBRT ultimately die of progressive systemic disease (11–13).Erlotinib, an epidermal growth factor receptor (EGFR) pathway inhibitor, is currently approved as first-line treatment for advanced NSCLC patients harboring EGFR mutations, and, as maintenance, second-line or third-line treatments following chemotherapy (14–17). Pre-clinical data show that erlotinib enhances the inhibitory effect of ionizing radiation in lung cancer, and it crosses the blood-brain barrier, so it could be used to provide sufficient radiosensitizing and therapeutic level in the brain (18–22).To exploit the potential radiosensitizing properties, the direct effect on brain metastases, and systemic activity of erlotinib, we examined the role of erlotinib given concurrently with WBRT, then as maintenance

Depth Dependent Relationships between Temperature and Ocean Heterotrophic Prokaryotic Production

9 páginas, 2 figuras, 1 tabla.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these termsCorrigendum: Depth Dependent Relationships between Temperature and Ocean Heterotrophic Prokaryotic Production, Frontiers in Marine Science 4: 91 (2017) https://doi.org/10.3389/fmars.2017.00091Marine prokaryotes play a key role in cycling of organic matter and nutrients in the ocean. Using a unique dataset (>14,500 samples), we applied a space-for-time substitution analysis to assess the temperature dependence of prokaryotic heterotrophic production (PHP) in epi- (0–200 m), meso- (201–1000 m) and bathypelagic waters (1001–4000 m) of the global ocean. Here, we show that the temperature dependence of PHP is fundamentally different between these major oceanic depth layers, with an estimated ecosystem-level activation energy (Ea) of 36 ± 7 kJ mol−1 for the epipelagic, 72 ± 15 kJ mol−1 for the mesopelagic and 274 ± 65 kJ mol−1 for the bathypelagic realm. We suggest that the increasing temperature dependence with depth is related to the parallel vertical gradient in the proportion of recalcitrant organic compounds. These Ea predict an increased PHP of about 5, 12, and 55% in the epi-, meso-, and bathypelagic ocean, respectively, in response to a water temperature increase by 1°C. Hence, there is indication that a major thus far underestimated feedback mechanism exists between future bathypelagic ocean warming and heterotrophic prokaryotic activityFinancial support for this project was provided by the Australian Institute of Marine Science (AIMS) and a grant from the Carlsberg Foundation to CL. XA, XM and JG were funded by the Malaspina expedition 2010 (grant n° CSD2008–00077) and HOTMIX (grant n° CTM2011–30010–C02–02) projects. TR was supported by the PADOM project (Austrian Science Fund grant n° P23221-B11). GH was funded by the Austrian Science Fund (FWF) project I486-B09 and by the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement No. 268595 (MEDEA project).Peer reviewe