Oxygen dynamics in shelf seas sediments incorporating seasonal variability

Shelf sediments play a vital role in global biogeochemical cycling and are particularly important areas of oxygen consumption and carbon mineralisation. Total benthic oxygen uptake, the sum of diffusive and faunal mediated uptake, is a robust proxy to quantify carbon mineralisation. However, oxygen uptake rates are dynamic, due to the diagenetic processes within the sediment, and can be spatially and temporally variable. Four benthic sites in the Celtic Sea, encompassing gradients of cohesive to permeable sediments, were sampled over four cruises to capture seasonal and spatial changes in oxygen dynamics. Total oxygen uptake (TOU) rates were measured through a suite of incubation experiments and oxygen microelectrode profiles were taken across all four benthic sites to provide the oxygen penetration depth and diffusive oxygen uptake (DOU) rates. The difference between TOU and DOU allowed for quantification of the fauna mediated oxygen uptake and diffusive uptake. High resolution measurements showed clear seasonal and spatial trends, with higher oxygen uptake rates measured in cohesive sediments compared to the permeable sediment. The significant differences in oxygen dynamics between the sediment types were consistent between seasons, with increasing oxygen consumption during and after the phytoplankton bloom. Carbon mineralisation in shelf sediments is strongly influenced by sediment type and seasonality

Free radicals and antioxidants at a glance using EPR spectroscopy

The delicate balance between the advantageous and detrimental effects of free radicals is one of the important aspects of human (patho)physiology. The controlled production of reactive oxygen and nitrogen species has an essential role in the regulation of various signaling switches. On the other hand, imbalanced generation of radicals is highly correlated with the pathogenesis of many diseases which require the application of selected antioxidants to regain the homeostasis. In the era of growing interest for redox processes, electron paramagnetic resonance (EPR) spectroscopy is arguably the best-suited technique for such research due to its ability to provide a unique insight into the world of free radicals and antioxidants. Herein, I present the principles of EPR spectroscopy and the applications of this method in assessing: (i) the oxidative status of biological systems, using endogenous long-lived free radicals (ascorbyl radical (Asc(center dot)), tocopheroxyl radical (TO center dot), melanin) as markers; (ii) the production of short-lived radicals (hydroxyl radical (OH center dot), superoxide radical anion (O-2(-)), sulfur-and carbon-centered radicals), which are implicated in both, oxidative stress and redox signaling; (iii) the metabolism of nitric oxide (NO center dot); (iv) the antioxidative properties of various drugs, compounds, and natural products; (v) other redox-relevant parameter. Besides giving a comprehensive survey of up-to-date literature, I also provide illustrative examples in sufficient detail to provide a means to exploit the potential of EPR in biochemical/physiological/medical research. The emphasis is on the features and characteristics (both positive and negative) relevant for EPR application in clinical sciences. My aim is to encourage fellow colleagues interested in free radicals and antioxidants to expand their base knowledge or methods used in their laboratories with data acquired by EPR or some of the EPR techniques outlined in this review, in order to boost up the exciting area of redox science