Wave-induced H2S flux sustains a chemoautotrophic symbiosis

Symbioses involving sulfur‐oxidizing bacteria and invertebrate hosts require a source of reduced sulfur, a source of O2, and transport mechanisms that ensure them a supply of both. We investigated these mechanisms using the symbiosis between the sessile ciliate Zoothamnium niveum (Hemprich and Ehrenberg 1831) and bacteria living on its surface. The stalked colonies of Z. niveum grow on peat walls around the openings of centimeter‐scale conduits created when mangrove rootlets decompose. Using in situ, time‐series measurements with fast‐responding amperometric microelectrodes, we found that the conduits were charged with H2S by diffusion from the decaying rootlets during periods of low boundary‐layer flow speed. During these times, the feeding current of the zooids transported oxygenated seawater from outside the peat wall toward the ectobiotic bacteria. During periods of high flow speed, H2S‐rich seawater from the conduits was drawn along the colonies and over the bacteria. We conclude that this symbiosis exploits a combination of two transport mechanisms: (1) venting of H2S‐rich seawater due to pulsating boundary‐layer current over ciliate groups and (2) the continuous and rapid feeding current generated by the host’s cilia. This discovery raises the possibility that other systems in which pockets of decay are exposed to pulsating flow could support similar symbioses

Deposition of aerially applied spray to a stream within a vegetative barrier

Drift of aerially applied forest herbicides can result in chemical deposition to streams. Riparian vegetation is expected to attenuate drift, but there is little corresponding data. A field study was conducted in the Coast Range west of Corvallis, Oregon, to evaluate the effectiveness of forested riparian buffers. The buffers studied are typical of those used for small and medium fish-bearing streams in western Oregon as mandated by the Oregon Forest Practices Act. A helicopter sprayed two tracers over four transects. Twenty trials were conducted, resulting in over 1400 tracer samples. Results confirm that these vegetative barriers are effective at reducing deposition into streams. Reduction of deposition on artificial foliage samplers placed immediately above the stream surface ranged from 37% to 99% and averaged 92%. Reductions were less clear in stable atmospheric conditions due to low wind speed and highly variable wind directions. Low wind speed conditions are not generally high-drift scenarios, but there is evidence that drift of suspended droplets beyond the barrier, comprising a small fraction of the total mass, increases in stable conditions

Rotary atomizer drop size distribution database

Wind tunnel measurements of drop Size distributions from Micronair A U4000 and A U5000 rotary atomizers were collected to develop a database for model use. The measurements varied tank mix, flow rate, air speed, and blade angle conditions, which were correlated by multiple regressions (average R-2 = 0.995 for A U4000 and 0.988 for AU5000). This database replaces an outdated set of rotary atomizer data measured in the 1980s by the USDA Forest Service and fills in a gap in data measured in the 1990s by the Spray Drift Task Force. Since current USDA Forest Service spray projects rely on rotary atomizers, the creation of the database (and its multiple regression interpolation) satisfies a need seen for ten years

Meiofauna in the Gollum Channels and the Whittard Canyon, Celtic Margin—How Local Environmental Conditions Shape Nematode Structure and Function

The Gollum Channels and Whittard Canyon (NE Atlantic) are two areas that receive high input of organic matter and phytodetritus from euphotic layers, but they are typified by different trophic and hydrodynamic conditions. Sediment biogeochemistry was analysed in conjunction with structure and diversity of the nematode community and differences were tested between study areas, water depths (700 m vs 1000 m), stations, and sediment layers. The Gollum Channels and Whittard Canyon harboured high meiofauna abundances (1054–1426 ind. 10 cm−2) and high nematode diversity (total of 181 genera). Next to enhanced meiofauna abundance and nematode biomass, there were signs of high levels of organic matter deposition leading to reduced sedimentary conditions, which in turn structured the nematode community. Striking in this respect was the presence of large numbers of ‘chemosynthetic’ Astomonema nematodes (Astomonema southwardorum, Order Monhysterida, Family Siphonolaimidae). This genus lacks a mouth, buccal cavity and pharynx and possesses a rudimentary gut containing internal, symbiotic prokaryotes which have been recognised as sulphur-oxidising bacteria. Dominance of Astomonema may indicate the presence of reduced environments in the study areas, which is partially confirmed by the local biogeochemical environment. The nematode communities were mostly affected by sediment layer differences and concomitant trophic conditions rather than other spatial gradients related to study area, water depth or station differences, pointing to small-scale heterogeneity as the main source of variation in nematode structure and function. Furthermore, the positive relation between nematode standing stocks, and quantity and quality of the organic matter was stronger when hydrodynamic disturbance was greater. Analogically, this study also suggests that structural diversity can be positively correlated with trophic conditions and that this relation is tighter when hydrodynamic disturbance is greater

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

Benthic pH gradients across a range of shelf sea sediment types linked to sediment characteristics and seasonal variability

This study used microelectrodes to record pH profiles in fresh shelf sea sediment cores collected across a range of different sediment types within the Celtic Sea. Spatial and temporal variability was captured during repeated measurements in 2014 and 2015. Concurrently recorded oxygen microelectrode profiles and other sedimentary parameters provide a detailed context for interpretation of the pH data. Clear differences in profiles were observed between sediment type, location and season. Notably, very steep pH gradients exist within the surface sediments (10–20 mm), where decreases greater than 0.5 pH units were observed. Steep gradients were particularly apparent in fine cohesive sediments, less so in permeable sandier matrices. We hypothesise that the gradients are likely caused by aerobic organic matter respiration close to the sediment–water interface or oxidation of reduced species at the base of the oxic zone (NH4+, Mn2+, Fe2+, S−). Statistical analysis suggests the variability in the depth of the pH minima is controlled spatially by the oxygen penetration depth, and seasonally by the input and remineralisation of deposited organic phytodetritus. Below the pH minima the observed pH remained consistently low to maximum electrode penetration (ca. 60 mm), indicating an absence of sub-oxic processes generating H+ or balanced removal processes within this layer. Thus, a climatology of sediment surface porewater pH is provided against which to examine biogeochemical processes. This enhances our understanding of benthic pH processes, particularly in the context of human impacts, seabed integrity, and future climate changes, providing vital information for modelling benthic response under future climate scenarios

Prenatal Exposure to Organophosphorus Pesticides and Preschool ADHD in the Norwegian Mother, Father and Child Cohort Study

Prenatal organophosphorus pesticide (OPP) exposure has been associated with child attention-deficit/hyperactivity disorder (ADHD) in agricultural communities and those that are exposed to residentially applied insecticides. To examine this association in populations that are exposed primarily through diet, we estimate the associations between prenatal OPP exposure and preschool ADHD in the Norwegian Mother, Father and Child Cohort Study (MoBa), and describe modification by paraoxonase 1 (PON1) gene variants. We used participants from the MoBa Preschool ADHD Sub-study (n = 259 cases) and a random sample of MoBa sub-cohort participants (n = 547) with birth years from 2004 to 2008. Prenatal urinary dialkylphosphate (DAP) metabolites (total diethylphosphate [∑DEP] and total dimethylphosphate [∑DMP]) were measured by an ultra-performance liquid chromatography-time-of-flight system and summed by molar concentration. Maternal DNA was genotyped for coding variants of PON1 (Q192R and L55M). We used a multivariable logistic regression to calculate the odds ratios (OR) and 95% confidence intervals, adjusted for maternal education, parity, income dependency, age, marital status, ADHD-like symptoms, pesticide use, produce consumption, and season. We found no associations between DAP metabolite concentrations and preschool ADHD. The adjusted ORs for exposure quartiles 2–4 relative to 1 were slightly inverse. No monotonic trends were observed, and the estimates lacked precision, likely due to the small sample size and variation in the population. We found no evidence of modification by PON1 SNP variation or child sex. Maternal urinary DAP concentrations were not associated with preschool ADHD