Reduced Nutrient Availability Research Articles

Straw composts, gypsum and their mixtures enhance tomato yields under continuous saline water irrigation

Freshwater shortage is common in most areas of the world, especially in arid and semiarid regions. Although saline water can be an alternative to freshwater in agricultural production, continuous saline (NaCl) water irrigation can easily lead to adverse effects on the soil-crop system. In this study, we measured the effects of flue gas desulfurization (FGD) gypsum, straw compost (SC), the SC mixed with FGD gypsum on site and the SC co-composted with FGD gypsum on soil properties, root nutrient uptake, shoot growth, crop yields and tomato quality under continuous saline water irrigation. The treatments considered were (i) untreated soils irrigated with non-saline water (control), (ii) untreated soils irrigated with saline water (SW), (iii) soils treated with SC and irrigated with saline water (SW + C), (iv) soils treated with FGD gypsum and irrigated with saline water (SW + G), (v) soils treated with the SC mixed with FGD gypsum on site and irrigated with saline water (SW + C+G), and (vi) soils treated with co-composted FGD gypsum-SC and irrigated with saline water (SW + GC). In general, under untreated soil conditions, continuous saline water irrigation resulted in adverse effects on soil properties (e.g. enhanced Na+ and sodium adsorption ratio and reduced nutrient availability) and tomato growth (e.g. the reduction of photosynthesis rate, plant growth rate, plant biomass and fruit yield, and the enhancement of blossom-end rot in tomato fruit). However, these adverse effects of continuous saline water irrigation were efficiently alleviated by the application of FGD gypsum and/or SC. The application of co-composted FGD gypsum-SC resulted in the highest fruit yield and the lowest blossom-end rot under continuous saline water irrigation. Plant straw co-composted with FGD gypsum can improve soil properties, maintain crop yields and enhance fruit quality under continuous saline water irrigation.

Siberian Trap volcanism, global warming and the Permian-Triassic mass extinction: New insights from Armenian Permian-Triassic sections

AbstractPermian-Triassic boundary sections from Armenia were studied for carbon isotopes of carbonates as well as oxygen isotopes of conodont apatite in order to constrain the global significance of earlier reported variations in the isotope proxies and elaborate the temporal relationship between carbon cycle changes, global warming and Siberian Trap volcanism. Carbon isotope records of the Chanakhchi and Vedi II sections show a 3–5‰ negative excursion that start in the Clarkina nodosa (C. yini) conodont Zone (latest Permian) with minimum values recorded in Hindeodus parvus to Isarcicella isarcica conodont zones (earliest Triassic). Sea surface temperatures (SST) reconstructed from oxygen isotopes of conodont apatite increase by 8–10 °C over an extrapolated time interval of ∼39 ka with the onset of global warming occurring in the C. iranica (C. meishanensis) Zone of the latest Permian. Climate warming documented in the Armenian sections is comparable to published time-equivalent shifts in SST in Iran and South China suggesting that this temperature change represents a true global signature. By correlating the Armenian and Iranian section with the radiometrically well-dated Meishan GSSP (Global Stratotype Section and Point) section (South China), the negative shift in δ13C is estimated to have occurred 12–128 ka prior to the onset of global warming. This temporal offset is unexpected given the synchrony in changes in atmospheric CO2 and global temperature as seen in Pleistocene ice core records. The negative δ13C excursion is explained by the addition of emission of isotopically light CO2 and CH4 from thermogenic heating of organic carbon-rich sediments by Siberian Trap sill intrusions. However, the observed time lag in the δ13C and δ18O shifts questions the generally assumed cause-effect relationship between emission of thermogenically produced greenhouse gases and global warming. The onset of temperature rise coincides with a significant enrichment in Hg/TOC (total organic carbon) ratios arguing for a major volcanic event at the base of the extinction interval. Whether global warming was a major factor for the Late Permian mass extinction depends on the duration of the extinction interval. Warming only starts at the base of the extinction interval, but with the extinction encompassing a time interval of 60 ± 48 ka, global climate warming in conjunction with temperature-related stressors as hypoxia and reduced nutrient availability may have been one of the major triggers of the most devastating biotic crisis in Earth history.

Does topsoil removal in grassland restoration benefit both soil nematode and plant communities?

Abstract Successful restoration of semi‐natural grasslands on grasslands previously subject to intensive management needs to overcome manifold barriers. These include high soil fertility, the dominance of a few fast‐growing plant species, degraded soil faunal communities and missing propagules of the targeted above‐ and below‐ground flora and fauna. A combination of removing the topsoil and introducing propagules of target plants has become one of the major tools for nature conservation agencies and practitioners to reduce soil fertility and restore former species‐rich grasslands in various European countries. Using topsoil removal as a restoration measure has provoked an ongoing debate between supporting nature conservation and rejecting soil protection agencies. Although it favours species‐rich plant communities, it strongly disturbs soil communities and affects physical and chemical soil properties and processes. Currently, there is a lack of long‐term data to assess how restored grassland ecosystems develop and recover after topsoil removal. Here, we used two well‐established bioindicators, soil nematodes and plants, to quantify restoration success of topsoil removal in comparison with alternative restoration measures and target communities 22 years after intervention. The nematode community composition indicated reduced nutrient availability in the restored systems, as was aimed at by topsoil removal. Nevertheless, after this 22‐year period following topsoil removal, nematode composition and structure revealed successful recovery. Plant communities benefitted from the reduction of soil nutrients after topsoil removal as indicated by higher numbers of plant species and higher Shannon diversity. Furthermore, topsoil removal strongly promoted the re‐establishment of plant species of the target plant community. Synthesis and applications. Overall, our study demonstrates how a massive intervention by topsoil removal proved successful in converting intensively managed into species‐rich grasslands. This contrasts with the mild intervention of repeated mowing and removing of the harvested plant material. We show that, in the long run, potential negative effects of topsoil removal on the soil fauna can be successfully overcome and plant communities can develop into targeted species‐rich grassland.

Are we restoring functional fens? - The outcomes of restoration projects in fens re-analysed with plant functional traits.

In peatland restoration we often lack an information whether re-established ecosystems are functionally similar to non-degraded ones. We re-analysed the long-term outcomes of restoration on vegetation and plant functional traits in 38 European fens restored by rewetting (18 sites) and topsoil removal (20 sites). We used traits related to nutrient acquisition strategies, competitiveness, seed traits, and used single- and multi-trait metrics. A separate set of vegetation records from near-natural fens with diverse plant communities was used to generate reference values to aid the comparisons. We found that both restoration methods enhanced the similarity of species composition to non-degraded systems but trait analysis revealed differences between the two approaches. Traits linked to nutrient acquisition strategies indicated that topsoil removal was more effective than rewetting. After topsoil removal competitive species in plant communities had decreased, while stress-tolerant species had increased. A substantial reduction in nutrient availability ruled out the effect of initial disturbance. An ability to survive and grow in anoxic conditions was enhanced after restoration, but the reference values were not achieved. Rewetting was more effective than topsoil removal in restricting variation in traits values permitted in re-developing vegetation. We found no indication of a shift towards reference in seed traits, which suggested that dispersal constraint and colonization deficit can be a widespread phenomena. Two functional diversity indices: functional richness and functional dispersion showed response to restoration and shifted values towards reference mires and away from the degraded systems.We concluded that targeting only one type of environmental stressor does not lead to a recovery of fens, as it provides insufficient level of stress to restore a functional ecosystem. In general, restoration efforts do not ensure the re-establishment and long-term persistence of fens. Restoration efforts result in recovery of fen ecosystems, confirmed with our functional trait analysis, although more rigid actions are needed for restoring fully functional mires, by achieving high and constant levels of anoxia and nutrient stresses.

Trait‐based approach confirms the importance of propagule limitation and assembly rules in old‐field restoration

Community assembly theory is suggested as a guiding principle for ecological restoration to help understand the mechanisms that structure biological communities and identify where restoration interventions are needed. We studied three hypotheses related to propagule limitation, stress‐dominance, and limiting similarity concepts in community assembly in a restoration field experiment with a trait‐based null model approach. The experiment aimed to assist the recovery of sand grassland on former arable land in the Kiskunság, Pannonian biogeographic region, Europe. Treatments included initial seeding of five grassland species, carbon amendment, low‐intensity mowing, and combinations in 1 m by 1 m plots in three old fields from 2003 to 2008. The distribution of 10 individual plant traits was compared to the null model and the effect of time and treatments were tested with linear mixed effect models. Initial seeding had the most visible impact on species and trait composition confirming propagule limitation in grassland recovery. Reducing nutrient availability through carbon amendment strengthened trait convergence for length of flowering as expected based on the stress‐dominance hypothesis. Mowing changed trait divergence to convergence for plant height with a strengthening impact with time, supporting our hypothesis of increasing dominance of limiting similarity with time. Our results support the idea that community assembly is simultaneously influenced by propagule limitation and multiple trait‐based processes that act through different traits. The limited impact of manipulating environmental filtering and limiting similarity compared to seeding, however, supports the view that only targeting the dispersal and environmental filters in parallel would improve restoration outcome.

Developmental diet irreversibly shapes male post-copulatory traits in the neriid fly Telostylinus angusticollis.

Nutrient availability has been shown to influence investment in many fitness-related traits, including male reproductive success. Many studies have demonstrated that a reduction in nutrient availability alters male post-copulatory trait expression, with some studies demonstrating an effect of developmental nutrients and others, an effect of adult nutrients. However, few studies have manipulated both developmental and adult nutrients in the same experiment. Therefore, it is not clear what life-stage has the greatest effect on post-copulatory trait expression, and if the effects of developmental and adult nutrients can interact. Here, we investigate effects of developmental and adult nutrition on male testes and accessory gland size, sperm movement within the female reproductive tract and sperm length in the neriid fly, Telostylinus angusticollis. We found that males fed a nutrient-poor developmental diet produced sperm with a reduced tail beat frequency and had smaller testes and accessory glands compared to males fed a nutrient-rich developmental diet. In contrast, we found no effects of adult nutrition on any traits measured, although sperm length was correlated with body size and male age but unaffected by nutrition at any stage. Therefore, investment in adult post-copulatory traits is determined early on by developmental nutrients in male neriid flies, and this effect is not altered by adult nutrient availability.

Abstract 449: Targeting PKR-like endoplasmic reticulum kinase modulates metabolism to promote T-cell effector function and PD1 immunotherapy responsiveness

Abstract The development of immunotherapy is a major recent advance in clinical oncology. However the majority of patients do not respond and those who do, experience resistance and relapse. Therefore, understanding the molecular mechanisms of immune checkpoint inhibitor resistance is critical to develop combinatorial drug strategies to potentiate therapeutic responsiveness to reduce mortality. Highly secretory cells, such as T-cells, have a larger endoplasmic reticulum (ER) to handle the increased protein translation capacity required by the cell. Therefore, T-cells may be highly sensitive to ER stress. The high nutrient needs of the tumor deplete resources in the microenvironment subjugating infiltrating T-cells to reduced nutrient availability resulting in stress. Our data indicate that co-culturing melanoma cells with T-cells increase T-cell specific unfolded protein response (UPR) signaling. Stimulating ER stress decreased cytolytic T-cell function in TALL-104 T-cells, enabling Mun2b melanoma survival. Knockdown of PERK restored T-cell killing capacity in ER stress induced cells. In an ex-vivo model of antigen-specific mediated T-cell death, Pmel-1 T-cells stimulated with gp100 displayed increased B16 melanoma killing when treated with GSK2606414 (a small molecule PERK inhibitor). PERK inhibition also elevated glycolysis proteins and mitochondrial bioenergetics in T-cells, suggesting PERK inhibition increases T-cell metabolism. As proof-of-concept, we determined the effect of PERK inhibition in a syngeneic B16 melanoma model. Male C57/Bl6 mice were inoculated with B16 melanoma cells. At 5 days post injection, mice were treated with a control IgG, antisense morpholino targeting PERK, PD1 antibody, or a combination of PERK morpholino and PD1 antibody. PERK morpholino treatment alone was sufficient to reduce tumor volume by 46.5%. PD1 antibody therapy alone reduced tumor volume by 47.4%. The combination of PD1 antibody and PERK targeting therapy significantly reduced B16 melanoma tumor volume by 64.5% demonstrating that targeting PERK in vivo enhanced immunocheckpoint therapy efficacy. Treated B16 tumors were homogenized and infiltrating T-cells isolated by flow cytometry. Gated CD3+ infiltrating leukocytes were then counted for CD8 and PD1 expression. Tumor infiltrating CD8+ T-cells doubled with PERK inhibition alone, giving further proof indicating that PERK may be a novel immune checkpoint target. Small molecule PERK inhibitors were previously shown to cause β-islet damage and insulin resistance; therefore we tested the effect of our PERK morpholino on glucose tolerance in the B16 melanoma model. PERK morpholino treatment had no overall impact on glucose tolerance and therefore may be a novel therapeutic to induce T-cell metabolism and potentiate immune checkpoint therapy efficacy with reduced off-target toxicities. Citation Format: David R. Soto-Pantoja, Yismeilin R. Feliz-Mosquea, Kenysha YJ Clear, Adam S. Wilson, Katherine L. Cook. Targeting PKR-like endoplasmic reticulum kinase modulates metabolism to promote T-cell effector function and PD1 immunotherapy responsiveness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 449.

Transition Metal Sequestration by the Host-Defense Protein Calprotectin.

In response to microbial infection, the human host deploys metal-sequestering host-defense proteins, which reduce nutrient availability and thereby inhibit microbial growth and virulence. Calprotectin (CP) is an abundant antimicrobial protein released from neutrophils and epithelial cells at sites of infection. CP sequesters divalent first-row transition metal ions to limit the availability of essential metal nutrients in the extracellular space. While functional and clinical studies of CP have been pursued for decades, advances in our understanding of its biological coordination chemistry, which is central to its role in the host-microbe interaction, have been made in more recent years. In this review, we focus on the coordination chemistry of CP and highlight studies of its metal-binding properties and contributions to the metal-withholding innate immune response. Taken together, these recent studies inform our current model of how CP participates in metal homeostasis and immunity, and they provide a foundation for further investigations of a remarkable metal-chelating protein at the host-microbe interface and beyond.

Concepts, Challenges, and Emerging Themes of Restoration Ecology

Concepts, Challenges, and Emerging Themes of Restoration Ecology

Ascophyllum nodosum-based algal extracts act as enhancers of growth, fruit quality, and adaptation to stress in salinized tomato plants

Seaweed extracts (SWE) are widely used to improve plant growth, fruit quality, and stress tolerance. However, the functional link between the complex composition of algal-based products and their mechanisms of action has been only marginally addressed. A greenhouse experiment was performed on Microtom tomato plants in order to evaluate the effect of two Ascophyllum nodosum-based algal derivatives, Rygex (R) and Super Fifty (SF), on a tomato exposed to salinity (0, 42.5, and 85 mM NaCl) and normal and reduced nutrient availability (100 and 70% of the standard regimen). Bioactive compounds, with possible beneficial effects on growth and stress adaptation, were characterized via gas chromatography-mass spectrometry analysis (GC-MS). Enhanced growth of 13% was observed with Super Fifty treatment under a full-strength nutritional regimen, independent of the salinity treatment. Although Rygex and Super Fifty treatments did not significantly enhance plant growth and yield under salt treatment, they enhanced the accumulation of minerals, antioxidants, and essential amino acids in tomato fruits, with an overall improvement in nutritional value. Overall, SWE may affect and ameliorate different aspects of nutrition and stress tolerance and thus contribute to the sustainability of agricultural systems. Elucidating the link between bioactive compounds in SWE and plant responses will be critical to characterizing the mechanism of action of SWE.

Regional Dispersal Influences Zooplankton Community Response to Dreissena polymopha Invasion

Aquatic systems are becoming increasingly susceptible to invasive species whereby local species are reduced in abundance and richness leading to changes in many food webs. Dispersal of species from surrounding lakes may provide a natural mechanism to increase local resistance by providing a diversity of locally adapted species to colonize affected communities. This study examined how zooplankton dispersal could potentially reduce the effects of the invasive zebra mussel, Dreissena polymorpha, on zooplankton community total abundance, species richness and diversity. Field experiments were conducted in 20 large tanks, with five replicates, to observe zooplankton community response to (1) the presence and absence of zebra mussels, and (2) the presence and absence of regional disperser zooplankton. Live regional zooplankton, from six surrounding lakes, were added fortnightly to dispersal treatments, while heat-killed zooplankton were added to no-dispersal treatments. All tanks were sampled for chlorophyll and zooplankton community samples prior to dispersal additions. Zooplankton were counted and identified as cladocerans and copepods (macrozooplankton), and rotifers (microzooplankton) to species. In the presence of mussels, chlorophyll was significantly depleted, reducing nutrient availability. All zooplankton richness and abundance decreased suggesting strong resource competition and direct predation by mussels. Dispersal did not affect macrozooplankton community structure, however, dispersal influenced the effect of zebra mussels on rotifers, further decreasing richness. This suggests species from the surrounding lakes may be highly competitive among local species, further proposing that regional species may influence zooplankton community structure and responses to zebra mussel invasion, but the effect is species dependent.

Plant species occurrence patterns in Eurasian grasslands reflect adaptation to nutrient ratios

Previous studies of Eurasian grasslands have suggested that nutrient ratios, rather than absolute nutrient availabilities and associated productivity, may be driving plant species richness patterns. However, the underlying assumption that species occupy distinct niches along nutrient ratio gradients remains to be tested. We analysed plant community composition and nutrient status of 644 Eurasian wet grassland plots. The importance of nutrient ratios driving variation in species composition was analysed using ordination methods (DCA and CCA). Subsequently, we assessed the niche position and width along the most important nutrient ratio gradient [N:P] for each species. We found that the N:P ratio explained part of the variation in species composition independent from conventional explanatory variables. The N:P ratio explained less variation than soil moisture or pH, but more than productivity or the availability of N and P separately, highlighting its importance for grassland species composition. Species occupied distinct niches along the N:P gradient, and species’ niche widths decreased toward extreme nutrient limitation. After correcting for niche position, there was no overall difference in niche width between endangered and non-endangered species. Surprisingly, endangered species with niche optima at the extreme P-limited end of the gradient had broader niches than their non-endangered counterparts. As species occupied distinct niches along a nutrient ratio gradient, future grassland conservation efforts may benefit from targeting changes in nutrient ratios, i.e. the balance between N and P, rather than only focussing on a general reduction in nutrient availability. However, what management interventions can be used for this purpose remains unclear.

Reprint to: Phosphate starvation during the transition phase increases the sex ratio and 12-oxo-phytodienoic acid contents in females of Urtica dioica

The transition phase in plants, which is marked by the onset of flowering and seed production, is very sensitive to the physical environment. Moreover, dimorphic plant species can show important sex-related differences in the response to nutrient availability. How availability of inorganic phosphate (Pi) during the transition phase influences sex ratios and whether or not male and female plants respond differently to nutrient stress is still however very poorly understood. Here, we examined whether contrasting Pi availability during the transition phase may influence sexual differentiation in stinging nettle (U. dioica L.) plants. We also evaluated to what extent males and females respond differently to varying Pi concentrations in terms of nutrient accumulation, C and N isotopic composition, photo-oxidative stress and hormone profiling. Results showed that reduced Pi availability delays plant maturation in males, causing as well an increase in the sex ratio towards females. Females showed enhanced lipid peroxidation (as indicated by higher lipid hydroperoxide contents) compared to males under Pi starvation, but sexes did not differ in photosystem II efficiency. Furthermore, reduced Pi availability led to enhanced 12-oxo-phytodienoic acid contents, the immediate precursor of jasmonic acid, particularly in females. This increase was, however, not accompanied by increases in other jasmonates, neither free nor conjugated jasmonic acid, thus suggesting a specific role for 12-oxo-phytodienoic acid in chemical defense in females under Pi starvation. Sex biased ratios in favour of females over males and enhanced 12-oxo-phytodienoic acid contents in the former under Pi starvation illustrate the great adaptive capacity of dimorphic species to reduced nutrient availability.

Mechanism of toxicity and transformation of silver nanoparticles: Inclusive assessment in earthworm-microbe-soil-plant system

Long term and inclusive toxicity studies encompassing soil, plants, and organisms are rare in literature for AgNPs. This study examines AgNP behavior in soil-plant system through 72weeks long soil experiment, earthworm response, and plant metabolic analysis. AgNP exposed earthworms did not show reproductive failure; yet high oxidative stress and reduced protein synthesis led to significant weight loss. Such stress was highest with AgNP50 exposure. Correspondingly, the 50ppm exposure of AgNP was capable to reduce nutrient availability and microbial growth in soil. Contrary to previous reports, we demonstrated that dissolution rate of AgNP increased with time in soil. Dynamic Light Scattering and UV-VIS assessments exhibited concentration and time dependent agglomeration of AgNP in soil and aqueous media. Moreover, lab based experiments in aqueous medium revealed that significant reduction in silver availability was due to formation of Ag2S or Ag3PO4; which also greatly affected the P and S availability. Although the vegetative growth of tomato was normal, AgNP (10mgkg−1) treatment markedly upset the fruit yield. The 10mgkg−1 AgNP exposure significantly enhanced oxidative stress and Ag uptake in plants; consequently, retarded N-assimilating enzyme (glutamate synthase, glutamine synthetase, and nitrate reductase) activity by suppressing their genes in plants. Eventually, photosynthesis and CO2 assimilating efficiency were severely disrupted. These assays were vital to appreciate the true toxicity and are not well attended in most of the studies with AgNPs.

The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

Abstract. Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996–2011) recorded off the coast of Callao (12° 02′ S, 77° 29′ W). The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes). The span of the data set allows us to contrast two OMZ regimes. The strong regime is associated with the strong 1997–1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The weak regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The data also reveal a long-term trend from 1999 corresponding to a deepening of the oxygen-deficient waters and warming. The implications of our results for understanding the OMZ dynamics off Peru are discussed.

Phosphate starvation during the transition phase increases the sex ratio and 12-oxo-phytodienoic acid contents in females of Urtica dioica

The transition phase in plants, which is marked by the onset of flowering and seed production, is very sensitive to the physical environment. Moreover, dimorphic plant species can show important sex-related differences in the response to nutrient availability. How availability of inorganic phosphate (Pi) during the transition phase influences sex ratios and whether or not male and female plants respond differently to nutrient stress is still however very poorly understood. Here, we examined whether contrasting Pi availability during the transition phase may influence sexual differentiation in stinging nettle (U. dioica L.) plants. We also evaluated to what extent males and females respond differently to varying Pi concentrations in terms of nutrient accumulation, C and N isotopic composition, photo-oxidative stress and hormone profiling. Results showed that reduced Pi availability delays plant maturation in males, causing as well an increase in the sex ratio towards females. Females showed enhanced lipid peroxidation (as indicated by higher lipid hydroperoxide contents) compared to males under Pi starvation, but sexes did not differ in photosystem II efficiency. Furthermore, reduced Pi availability led to enhanced 12-oxo-phytodienoic acid contents, the immediate precursor of jasmonic acid, particularly in females. This increase was, however, not accompanied by increases in other jasmonates, neither free nor conjugated jasmonic acid, thus suggesting a specific role for 12-oxo-phytodienoic acid in chemical defense in females under Pi starvation. Sex biased ratios in favour of females over males and enhanced 12-oxo-phytodienoic acid contents in the former under Pi starvation illustrate the great adaptive capacity of dimorphic species to reduced nutrient availability.

Legacy effects of drought alters the aquatic food web of a northern boreal peatland

Abstract Compared to other temporary aquatic ecosystems, we know relatively little about how inundation frequency and duration (i.e. hydrologic regime) influences the structure of aquatic communities in northern peatlands. In this study, we examined patterns in nutrient availability and aquatic community structure during a natural flooding event in an Alaskan fen where water‐table position had been manipulated in three large‐scale experimental plots during previous years to simulate both drought (lowered water‐table treatment) and flooding (raised water‐table treatment) conditions relative to a control without manipulation. Although the natural flood disrupted the long‐term experimental manipulation, it provided an opportunity to evaluate how variation in past hydrologic regime influences nutrient dynamics and aquatic food web structure during periods of inundation in a northern boreal peatland. Despite similar water depth among experimental plots during the time of sampling (i.e. water was above the peat surface in all plots), water‐column nutrient concentrations were significantly greater in the drought treatment (where water table had been lowered during the previous growing season) compared to the raised water‐table treatment and the control. Algal production increased with enhanced nutrient availability across all water‐table treatments and was most elevated following the rewetting of dry sediments in the drought treatment. Consumer biomass (heterotrophic bacteria and macroinvertebrates) increased with algal production and was significantly greater in the drought treatment compared to the raised water‐table treatment and the control. Consumer biomass decreased into the second year of constant inundation as algal production was constrained by reduced nutrient availability. Stable isotope analysis (13C and 15N) showed that elevated levels of periphyton (i.e. the intact biofilm) associated with enhanced nutrient availability promoted energy transfer to higher trophic levels (grazers and predators) rather than living or dead mosses or vascular plant material. Consumption of algal material by grazers altered the size and composition of the algal community. The algal community shifted from coccoid (edible) to filamentous (inedible) growth forms with increased grazer abundance in the drought treatment, possibly owing to selective grazing. Conversely, there was a similar proportion of edible and inedible taxa in the control and raised treatments where grazers were lower in abundance. Our results show that the legacy effects of drought can regulate aquatic community structure in northern peatlands. Within a predictive context, our findings suggest that conditions of more variable hydrology expected with climate change (i.e. increased frequency of drought) occurring across northern latitudes will promote energy flow to higher trophic levels by releasing nutrient constraints on microalgae during periods of inundation.

Phytase dose effects in practically formulated diets that vary in ingredient composition on feed manufacturing and broiler performance

Considering approaches to efficiently produce broiler chickens, an experiment was conducted to describe the manufacturing and feeding effects of a corn, soybean meal, and wheat based diet with varying levels of corn distillers dried grains with solubles (DDGS) and commercial phytase. Treatments were arranged in a 3 × 2 factorial randomized complete block design varying in phytase (zero, 1,000, and 6,000 FTU/kg) and DDGS inclusion (zero or 5%). Phytase inclusion decreased dietary non-phytate phosphorous (nPP) and total Calcium (Ca) in formulation by 0.12 and 0.1%, respectively. Diets were steam conditioned at 82°C for 10 s, extruded through a 4.7 × 38 mm pellet die, and fed as crumbles (starter and grower) or pellets (finisher). Ten replicate pens of straight-run Hubbard × Cobb 500 chicks consumed one of 6 dietary treatments for 38 days. Phytase improved feed conversion ratio (FCR) in the starter period (P = 0.05), but benefits were not apparent in the grower or finisher periods. Phytase and formulation main effects interacted to affect overall FCR (P = 0.05), demonstrating a 0.05 decrease in FCR when birds were fed a diet containing a super-dose of phytase and without DDGS relative to diets containing a super-dose of phytase and DDGS. The DDGS likely provided reduced nutrient availability relative to their nutrient values used for diet formulation or provided non-starch polysaccharides (NSP) at a level that decreased bird performance. Based on tibia ash measures, performance improvement associated with the super-dose of phytase was likely associated with reducing phytate phosphorus gastrointestinal irritation rather than meeting bird phosphorus requirement.

Interactive effects of nutrient availability and temperature on growth and survival of different size classes of Saccharina japonica (Laminariales, Phaeophyceae)

:In northern Japan, the production of Saccharina japonica exhibits marked annual fluctuation due to changes in seawater temperature and nutrient availability during winter and spring. To better understand this phenomenon, we examined the combined effects of temperature (5°C, 10°C, 15°C and 20°C) and nutrient availability (seawater enriched with 25% Provasoli's enriched seawater vs nonenriched seawater) on photosynthesis, growth and survival and nitrogen and chlorophyll a contents of juvenile sporophytes (2–3 cm) and larger size class sporophytes (100–150 cm) from southern Hokkaido. Both juvenile sporophytes and discs from 100–150-cm-class sporophytes cultured in enriched seawater showed significantly higher growth rates and photosynthetic activities than those cultured in nonenriched seawater. This difference likely was due to the significantly higher nitrogen and chlorophyll a contents of thalli grown in enriched seawater. Significant effects of temperature on growth and photosynthesis were also detected. A significant interaction between temperature and nutrient availability for relative growth rate (RGR) was detected. The positive effect of elevated nutrient availability on RGRs was magnified by an increase in temperature from 5°C to 15°C for juvenile sporophytes and from 5°C to 10°C for 100–150-cm-class sporophytes; whereas, the negative effect of elevated temperature from 10°C to 15°C on RGRs of 100–150-cm-class sporophytes was antagonised by a reduction in nutrient availability. In contrast to the 100% survival rate in enriched seawater, dead juvenile sporophytes and discs from 100–150-cm-class sporophytes were found at 15°C and 20°C in nonenriched seawater, and the survival rates decreased with increasing temperature. Therefore, the growth and survival of sporophytes of S. japonica are significantly affected by nutrient availability and temperature, which may lead to marked fluctuations in annual production.

Pollution and climate change drive long-term change in Scottish wetland vegetation composition

Wetlands are key components of upland landscapes and support a diverse and specialised biota. These habitats are subject to multiple drivers of change including pollutant deposition, climate change and grazing, which have varied over the last four decades. We used a resurvey approach to investigate vegetation change in Carex swamps and spring communities in the Scottish uplands between the 1970s and 2000s. We assessed changes in species group richness and cover and cover-weighted mean Ellenberg values between surveys, and related this to change in nitrogen and sulphur deposition, climate and grazing by sheep and deer.Species richness, particularly of graminoids and forbs, but also bryophytes in springs, increased between surveys. Graminoid cover in springs increased while forbs and bryophytes declined. Changes in Ellenberg values, suggested slight eutrophication in swamp habitats, but acidification and reduction in nutrient availability in springs. This apparent acidification occurred despite large reductions in sulphur deposition over the survey period and was associated with both cumulative sulphur and oxidised nitrogen deposition. Impacts of climate change were detected in spring habitats, where increases in growing degree days were associated with increased graminoid cover and a decline in forb cover. Grazing impacts were detected only in springs, where sheep grazing appeared to counteract the deleterious effects of warming by reducing graminoid cover. Our study highlights the multiple threats facing wetland communities in the uplands. The results show the need for ongoing pollution reductions to prevent further degradation of sensitive wetland habitats which are further impacted by climate change.