Ecosystem engineering by plants on wave-exposed intertidal flats is governed by relationships between effect and response traits

In hydrodynamically stressful environments, some species—known as ecosystem engineers—are able to modify the environment for their own benefit. Little is known however, about the interaction between functional plant traits and ecosystem engineering. We studied the responses of Scirpus tabernaemontani and Scirpus maritimus to wave impact in full-scale flume experiments. Stem density and biomass were used to predict the ecosystem engineering effect of wave attenuation. Also the drag force on plants, their bending angle after wave impact and the stem biomechanical properties were quantified as both responses of stress experienced and effects on ecosystem engineering. We analyzed lignin, cellulose, and silica contents as traits likely effecting stress resistance (avoidance, tolerance). Stem density and biomass were strong predictors for wave attenuation, S. maritimus showing a higher effect than S. tabernaemontani. The drag force and drag force per wet frontal area both differed significantly between the species at shallow water depths (20 cm). At greater depths (35 cm), drag forces and bending angles were significantly higher for S. maritimus than for S. tabernaemontani. However, they do not differ in drag force per wet frontal area due to the larger plant surface of S. maritimus. Stem resistance to breaking and stem flexibility were significantly higher in S. tabernaemontani, having a higher cellulose concentration and a larger cross-section in its basal stem parts. S. maritimus had clearly more lignin and silica contents in the basal stem parts than S. tabernaemontani. We concluded that the effect of biomass seems more relevant for the engineering effect of emergent macrophytes with leaves than species morphology: S. tabernaemontani has avoiding traits with minor effects on wave attenuation; S. maritimus has tolerating traits with larger effects. This implies that ecosystem engineering effects are directly linked with traits affecting species stress resistance and responding to stress experienced

Development and Validation of an Analytical Method for Quantitation of Monobutylphthalate, a Metabolite of Di-n-Butylphthalate, in Rat Plasma, Amniotic Fluid, Fetuses and Pups by UPLC-MS/MS

Abstract Phthalates have been used for decades as softening agents in the production of plastics, but in recent years have been extensively investigated for their potential hazards to human health and the environment. Di-n-butyl phthalate (DBP), with widespread exposure occurring through a variety of consumer products such as cosmetics and pesticides, is a suspected carcinogen and an endocrine system disruptor in both humans and laboratory animals. Its predominant metabolite is the monoester, monobutyl phthalate (MBP), which can serve as a marker of exposure. To support toxicological studies of DBP in pregnant and lactating rats and their offspring, a novel ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for quantitation of MBP in rat plasma, amniotic fluid, fetuses and whole pup samples. Plasma samples were extracted using a simple protein precipitation with acetonitrile. Extraction and delipidation of pup homogenate was performed using acetonitrile and then submerging the vials in liquid nitrogen. Extracts were analyzed by UPLC-MS/MS in the negative ion mode. The method was successfully validated over the concentration ranges 25–5,000 ng/mL in female Sprague Dawley (SD) rat plasma and 50–5,000 ng/g in SD pup homogenate. Matrix calibration curves were linear (r ≥ 0.99), and the percent relative error (%RE) values were ≤ ±15% for standards at all levels. Absolute recoveries were &amp;gt; 92% in both matrices. The limits of detection (LODs) were 6.9 ng/mL in plasma and 9.4 ng/g in pup homogenate. Acceptable intra- and interday accuracy and precision were demonstrated by mean %RE ≤ ±7.5 and relative standard deviation (%RSD) ≤ 10.1%. Extract stability was demonstrated for ~6 days at various temperatures and freeze–thaw stability was demonstrated after 3 cycles over 3 days. Secondary matrix evaluation was performed for MBP in amniotic fluid and pooled fetus homogenate (mean %RE ≤ ±11.5 and %RSD ≤ 13.7). These data demonstrate that this simple method is suitable for determination of MBP in plasma, amniotic fluid, fetus and pup samples from toxicological studies of DBP.</jats:p

Development and Validation of an Analytical Method for Quantitation of Bisphenol S in Rodent Plasma, Amniotic Fluid and Fetuses by UPLC–MS-MS

Abstract Bisphenol S (BPS) has been detected in personal care products, water, food and indoor house dust, demonstrating the potential for human exposure. Due to limited data to characterize the hazard of BPS, the National Toxicology Program (NTP) is investigating the toxicity of BPS in rodent models. Generating systemic exposure data is integral to putting toxicological findings into context. The objective of this work was to develop and validate a method to quantitate free (unconjugated parent) and total (free and all conjugated forms of) BPS in rodent plasma, amniotic fluid and fetal homogenate in support of NTP studies. The method used incubation with (total BPS) and without (free BPS) deconjugating enzyme and then protein precipitation followed by ultra-performance liquid chromatography-tandem mass spectrometry. In Sprague Dawley rat plasma, the method was linear (r ≥ 0.99) over the range 5–1,000 ng/mL, accurate (mean relative error (RE) ≤ ±10.5%) and precise (relative standard deviation (RSD) ≤ 7.7%). Mean recoveries were ≥93.1% for both free and total analyses. The limits of detection were 1.15 ng/mL (free) and 0.862 ng/mL (total) in plasma. The method was evaluated in the following study matrices: (i) male Hsd:Sprague Dawley®SD® (HSD) rat plasma, (ii) female HSD rat plasma, (iii) male B6C3F1 mouse plasma, (iv) female B6C3F1 mouse plasma, (v) HSD rat gestational day (GD) 18 dam plasma, (vi) HSD rat GD 18 amniotic fluid, (vii) HSD rat GD 18 fetal homogenate and (viii) HSD rat postnatal day 4 pup plasma (mean %RE ≤ ±8.2 and %RSD ≤ 8.7). Stability of BPS in extracted samples was demonstrated for up to 7 days at various temperatures, and freeze–thaw stability was demonstrated after three cycles over 7 days. BPS in various matrices stored at −80°C for at least 60 days was within 92.1–115% of Day 0 concentrations, demonstrating its stability in these matrices. These data demonstrate that this simple method is suitable for determination of free and total BPS in plasma, amniotic fluid and fetuses following exposure of rodents to BPS.</jats:p

Development and Validation of an Analytical Method for Quantitation of Sulfolane in Rat and Mouse Plasma by GC–MS

AbstractSulfolane is an industrial solvent commonly used for extraction of aromatic hydrocarbons in the oil refining process, as well in the purification of natural gas. Its wide use and high solubility in water has led to contamination of groundwater. The objective of this work was to develop and validate an analytical method to quantitate sulfolane in rodent plasma in support of the National Toxicology Program toxicology and toxicokinetic studies of sulfolane. The method uses extraction of plasma with ethyl acetate and analysis by gas chromatography–mass spectrometry with electron ionization. The method was validated in male Sprague Dawley (SD) rat plasma over the concentration range of 20–100,000 ng/mL. The method was linear (r ≥ 0.99), accurate (mean relative error (RE) ≤ ±5.1%) and precise (relative standard deviation (RSD) ≤ 2.9%). The absolute recovery was ≥74%. The limit of detection was 0.516 ng/mL. Standards as high as ~2.5 mg/mL could be successfully diluted into the calibration range (mean %RE ≤ ±4.5; %RSD ≤ 4.6). Extracted samples were stable for at least 3 days at ambient and refrigerated temperatures, and freeze/thaw stability in matrix was demonstrated after three cycles over 3 days (calculated concentrations within 90.8–102% of Day 0 concentrations). Sulfolane was stable in frozen plasma for at least 75 days at −80°C (calculated concentrations within 93.0–98.1% of Day 0 concentrations). Matrix evaluation was performed for sulfolane in female SD rat plasma and male and female B6C3F1 mouse plasma (mean %RE ≤ ±4.9; %RSD ≤ 3.3). These data demonstrate that the method is suitable for determination of sulfolane in rodent plasma.</jats:p

Quantifying critical conditions for seaward expansion of tidal marshes: a transplantation experiment

The alternative stable states theory is increasingly applied to tidal marsh shorelines, where the two opposing stable states – a dense vegetated state on the one hand and a bare tidal flat on the other hand – can coexist in time but differ in space. The shift from the bare to vegetated state by the establishment of individual plants (seedlings, rhizome-grown shoots) on the bare tidal flat is known to be triggered by the occurrence of windows of opportunity. These are periods when species- and life stage-dependent thresholds, such as sediment dynamics or wave impact, are not exceeded. One controlling environmental parameter in intertidal wetlands is elevation as many important stressors for plants – such as hydroperiod, sediment dynamics and wave properties (wave period and wave height) – are typically correlated to it. Disentangling the respective impact of these correlated stressors remains challenging. In this paper, we present the results of a transplantation experiment where the establishment of three different life stages (seedlings, rhizome-grown shoots and patches) of the brackish pioneer <i>Scirpus maritimus</i> was tested over an elevation gradient at two locations of contrasting wave exposure. This gradient reached from the bare tidal flat into the marsh and covered an elevation range at which continuous <i>S. maritimus-</i>dominated pioneer marsh is known to occur. We found that erosion stress influences seedling survival on tidal flats while drought stress seems to limit long-term establishment of individual shoots and seedlings in the marsh. Furthermore, survival of transplants was more successful on the tidal flat of the sheltered site compared to the tidal flat of the exposed site whereas survival time within the marsh did not differ between sites. This highlights the attenuation of waves and currents in exposed marshes. However, no long-term establishment occurred on the tidal flat, emphasizing the importance of clonal integration for tidal flat colonization

Development of an Analytical Method for Quantitation of 2,2ʹ-Dimorpholinodiethyl Ether (DMDEE) in Rat Plasma, Amniotic Fluid and Fetal Homogenate by UPLC–MS-MS for Determination of Gestational and Lactational Transfer in Rats

Abstract 2,2ʹ-Dimorpholinodiethyl ether (DMDEE) is a specialty amine catalyst used in the production of flexible foams, adhesives and coatings. The potential for occupational exposure to DMDEE is high, but toxicity data are very limited. The objective of this work was to develop a method to quantitate DMDEE in biological matrices to assess gestational and lactational transfer of DMDEE in rats following exposure of dams The method used protein precipitation, followed by removal of phospholipids and analysis of supernatant by ultra-performance liquid chromatography-tandem mass spectrometry. Rat fetuses were homogenized in water prior to protein precipitation and delipidation procedures. The method was evaluated in male Sprague Dawley rat plasma over the concentration range 5 to 1000 ng/mL. The method was linear (r ≥ 0.99), accurate (mean relative error (RE) ≤ ±11.9%) and precise (relative standard deviation (RSD) ≤ 2.7%). The mean absolute recovery was 106%. The limit of detection was 0.262 ng/mL. Standards as high as ∼100,000 ng/mL could be successfully diluted into the calibration range (mean %RE = −14.9; %RSD = 0.5). The method was evaluated in Sprague Dawley rat dam plasma, post-natal day 4 pup plasma, gestational day (GD) 18 amniotic fluid and fetal homogenate (mean %RE ≤ ±11.9; %RSD ≤ 2.3). Concentrations of DMDEE in rat dam plasma, amniotic fluid and fetal homogenate stored for at least 29 days and in pup plasma for at least 18 days at −80°C were within 87.7 to 99.5% of Day 0 concentrations, demonstrating that DMDEE is stable in these matrices. The method was used to quantitate DMDEE in rat plasma, amniotic fluid and fetus samples from a dose range finding toxicology study in which dams were dosed via gavage with DMDEE from GD 6 at doses of 0 (control), 62.5 and 250 mg/kg/day. DMDEE concentration increased with the dose in all matrices examined. The concentration in GD 18 fetuses was almost 2-fold higher than GD 18 dams demonstrating gestational transfer of DMDEE. However, the concentration in post-natal day 4 pup plasma was more than an order of magnitude lower than corresponding dam plasma suggesting less potential for transfer of DMDEE from dams to pups via lactation. There was no significant difference in concentration for male and female pup plasma.</jats:p