Deciphering the dynamics of inorganic carbon export from intertidal salt marshes using high-frequency measurements

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Chemistry 206 (2018): 7-18, doi:10.1016/j.marchem.2018.08.005.The lateral export of carbon from coastal marshes via tidal exchange is a key component of the marsh carbon budget and coastal carbon cycles. However, the magnitude of this export has been difficult to accurately quantify due to complex tidal dynamics and seasonal cycling of carbon. In this study, we use in situ, high-frequency measurements of dissolved inorganic carbon (DIC) and water fluxes to estimate lateral DIC fluxes from a U.S. northeastern salt marsh. DIC was measured by a CHANnelized Optical Sensor (CHANOS) that provided an in situ concentration measurement at 15-min intervals, during periods in summer (July – August) and late fall (December). Seasonal changes in the marsh had strong effects on DIC concentrations, while tidally-driven water fluxes were the fundamental vehicle of marsh carbon export. Episodic events, such as groundwater discharge and mean sea water level changes, can impact DIC flux through altered DIC concentrations and water flow. Variability between individual tides within each season was comparable to mean variability between the two seasons. Estimated mean DIC fluxes based on a multiple linear regression (MLR) model of DIC concentrations and high-frequency water fluxes agreed reasonably well with those derived from CHANOS DIC measurements for both study periods, indicating that high-frequency, modeled DIC concentrations, coupled with continuous water flux measurements and a hydrodynamic model, provide a robust estimate of DIC flux. Additionally, an analysis of sampling strategies revealed that DIC fluxes calculated using conventional sampling frequencies (hourly to two-hourly) of a single tidal cycle are unlikely to capture a representative mean DIC flux compared to longer-term measurements across multiple tidal cycles with sampling frequency on the order of tens of minutes. This results from a disproportionately large amount of the net DIC flux occurring over a small number of tidal cycles, while most tides have a near-zero DIC export. Thus, high-frequency measurements (on the order of tens of minutes or better) over the time period of interest are necessary to accurately quantify tidal exports of carbon species from salt marshes.This work was funded by NSF Graduate Research Fellowship Program, NSF Ocean Sciences Postdoctoral Fellowship (OCE-1323728), Link FoundationOcean Engineering and Instrumentation Fellowship, National Institute of Science and Technology (NIST no. 60NANB10D024), the USGS LandCarbon and Coastal & Marine Geology Programs, NSF Chemical Oceanography Program (OCE-1459521), NSF Ocean Technology and Interdisciplinary Coordination program (OCE-1233654) and NOAA Science Collaborative (NA09NOS4190153)

Intertidal salt marshes as an important source of inorganic carbon to the coastal ocean

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography 61 (2016): 1916–1931, doi:10.1002/lno.10347.Dynamic tidal export of dissolved inorganic carbon (DIC) to the coastal ocean from highly productive intertidal marshes and its effects on seawater carbonate chemistry are thoroughly evaluated. The study uses a comprehensive approach by combining tidal water sampling of CO2 parameters across seasons, continuous in situ measurements of biogeochemically-relevant parameters and water fluxes, with high-resolution modeling in an intertidal salt marsh of the U.S. northeast region. Salt marshes can acidify and alkalize tidal water by injecting CO2 (DIC) and total alkalinity (TA). DIC and TA generation may also be decoupled due to differential effects of marsh aerobic and anaerobic respiration on DIC and TA. As marsh DIC is added to tidal water, the buffering capacity first decreases to a minimum and then increases quickly. Large additions of marsh DIC can result in higher buffering capacity in ebbing tide than incoming tide. Alkalization of tidal water, which mostly occurs in the summer due to anaerobic respiration, can further modify buffering capacity. Marsh exports of DIC and alkalinity may have complex implications for the future, more acidified ocean. Marsh DIC export exhibits high variability over tidal and seasonal cycles, which is modulated by both marsh DIC generation and by water fluxes. The marsh DIC export of 414 g C m−2 yr−1, based on high-resolution measurements and modeling, is more than twice the previous estimates. It is a major term in the marsh carbon budget and translates to one of the largest carbon fluxes along the U.S. East Coast.USGS Coastal & Marine Geology Program; U.S. National Science Foundation Grant Number: OCE-1459521; NOAA Science Collaborative Grant Number: NA09NOS4190153; USGS LandCarbon Progra

Changes in anthropogenic carbon storage in the Northeast Pacific in the last decade

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 4618–4632, doi:10.1002/2016JC011775.In order to understand the ocean's role as a sink for anthropogenic carbon dioxide (CO2), it is important to quantify changes in the amount of anthropogenic CO2 stored in the ocean interior over time. From August to September 2012, an ocean acidification cruise was conducted along a portion of the P17N transect (50°N 150°W to 33.5°N 135°W) in the Northeast Pacific. These measurements are compared with data from the previous occupation of this transect in 2001 to estimate the change in the anthropogenic CO2 inventory in the Northeast Pacific using an extended multiple linear regression (eMLR) approach. Maximum increases in the surface waters were 11 µmol kg−1 over 11 years near 50°N. Here, the penetration depth of anthropogenic CO2 only reached ∼300 m depth, whereas at 33.5°N, penetration depth reached ∼600 m. The average increase of the depth-integrated anthropogenic carbon inventory was 0.41 ± 0.12 mol m−2 yr−1 across the transect. Lower values down to 0.20 mol m−2 yr−1 were observed in the northern part of the transect near 50°N and increased up to 0.55 mol m−2 yr−1 toward 33.5°N. This increase in anthropogenic carbon in the upper ocean resulted in an average pH decrease of 0.002 ± 0.0003 pH units yr−1 and a 1.8 ± 0.4 m yr−1 shoaling rate of the aragonite saturation horizon. An average increase in apparent oxygen utilization of 13.4 ± 15.5 µmol kg−1 centered on isopycnal surface 26.6 kg m−3 from 2001 to 2012 was also observed.National Science Foundation Ocean Acidification Program Grant Number: OCE-1041068; National Institute of Standards and Technology Grant Number: (NIST-60NANB10D024); National Science Foundation Graduate Research Fellowship Program2017-01-0

Serum-Nutrient Starvation Induces Cell Death Mediated by Bax and Puma That Is Counteracted by p21 and Unmasked by Bcl-xL Inhibition

The cyclin-dependent kinase inhibitor p21 (p21WAF1/Cip1) is a multifunctional protein known to promote cell cycle arrest and survival in response to p53-dependent and p53 independent stimuli. We herein investigated whether and how it might contribute to the survival of cancer cells that are in low-nutrient conditions during tumour growth, by culturing isogenic human colorectal cancer cell lines (HCT116) and breast cancer cell lines in a medium deprived in amino acids and serum. We show that such starvation enhances, independently from p53, the expression of p21 and that of the pro-apoptotic BH3-only protein Puma. Under these conditions, p21 prevents Puma and its downstream effector Bax from triggering the mitochondrial apoptotic pathway. This anti-apoptotic effect is exerted from the cytosol but it is unrelated to the ability of p21 to interfere with the effector caspase 3. The survival function of p21 is, however, overcome by RNA interference mediated Bcl-xL depletion, or by the pharmacological inhibitor ABT-737. Thus, an insufficient supply in nutrients may not have an overt effect on cancer cell viability due to p21 induction, but it primes these cells to die, and sensitizes them to the deleterious effects of Bcl-xL inhibitors regardless of their p53 status

Health care utilisation under the 30-Baht Scheme among the urban poor in Mitrapap slum, Khon Kaen, Thailand: a cross-sectional study

Background: In 2001, the Government of Thailand introduced a universal coverage scheme with the aim of ensuring equitable health care access for even the poorest citizens. For a flat user fee of 30 Baht per consultation, or for free for those falling into exemption categories, every scheme participant may access registered health services. The exemption categories include children under 12 years of age, senior citizens aged 60 years and over, the very poor, and volunteer health workers. The functioning of these exemption mechanisms and the effect of the scheme on health service utilisation among the poor is controversial. Methods: This cross-sectional study investigated the prevalence of 30-Baht Scheme registration and subsequent self-reported health service utilisation among an urban poor population in the Teparuk community within the Mitrapap slum in Khon Kaen city, northeastern Thailand. Furthermore, the effectiveness of the exemption mechanisms in reaching the very poor and the elderly was examined. Factors for users' choice of health facilities were identified. Results: Overall, the proportion of the Teparuk community enrolled with the 30-Baht Scheme was high at 86%, with over one quarter of these exempted from paying the consultation fee. User fee exemption was significantly more frequent among households with an above-poverty-line income (64.7%) compared to those below the poverty line (35.3%), χ2 (df) = 5.251 (1); p-value = 0.018. In addition, one third of respondents over 60 years of age were found to be still paying user fees. Self-reported use of registered medical facilities in case of illness was stated to be predominantly due to the service being available through the scheme, with service quality not a chief consideration. Overall consumer satisfaction was high, especially among those not required to pay the 30 Baht user fee. Conclusion: Whilst the 30-Baht Scheme seems to cover most of the poor population of Mitrapap slum in Khon Kaen, the user fee exemption mechanism only works partially with regard to reaching the poorest and exempting senior citizens. Service utilisation and satisfaction are highest amongst those who are fee-exempt. Service quality was not an important factor influencing choice of health facility. Ways should be sought to improve the effectiveness of the current exemption mechanisms.Sophie Coronini-Cronberg, Wongsa Laohasiriwong and Christian A Gerick

A principal component meta-analysis on multiple anthropometric traits identifies novel loci for body shape

Large consortia have revealed hundreds of genetic loci associated with anthropometric traits, one trait at a time. We examined whether genetic variants affect body shape as a composite phenotype that is represented by a combination of anthropometric traits. We developed an approach that calculates averaged PCs (AvPCs) representing body shape derived from six anthropometric traits (body mass index, height, weight, waist and hip circumference, waist-to-hip ratio). The first four AvPCs explain >99% of the variability, are heritable, and associate with cardiometabolic outcomes. We performed genome-wide association analyses for each body shape composite phenotype across 65 studies and meta-analysed summary statistics. We identify six novel loci: LEMD2 and CD47 for AvPC1, RPS6KA5/C14orf159 and GANAB for AvPC3, and ARL15 and ANP32 for AvPC4. Our findings highlight the value of using multiple traits to define complex phenotypes for discovery, which are not captured by single-trait analyses, and may shed light onto new pathways