Aquatic Vegetation Loss and Its Implication on Climate Regulation in a Protected Freshwater Wetland of Po River Delta Park (Italy)

Aquatic vegetation loss caused substantial decrease of ecosystem processes and services during the last decades, particularly for the capacity of these ecosystems to sequester and store carbon from the atmosphere. This study investigated the extent of aquatic emergent vegetation loss for the period 1985–2018 and the consequent effects on carbon sequestration and storage capacity of Valle Santa wetland, a protected freshwater wetland dominated by Phragmites australis located in the Po river delta Park (Northern Italy), as a function of primary productivity and biomass decomposition, assessed by means of satellite images and experimental measures. The results showed an extended loss of aquatic vegetated habitats during the considered period, with 1989 being the year with higher productivity. The mean breakdown rates of P. australis were 0.00532 d−1 and 0.00228 d−1 for leaf and stem carbon content, respectively, leading to a predicted annual decomposition of 64.6% of the total biomass carbon. For 2018 the carbon sequestration capacity was estimated equal to 0.249 kg C m−2 yr−1, while the carbon storage of the whole wetland was 1.75 × 103 t C (0.70 kg C m−2). Nonetheless, despite the protection efforts over time, the vegetation loss occurred during the last decades significantly decreased carbon sequestration and storage by 51.6%, when comparing 2018 and 1989. No statistically significant effects were found for water descriptors. This study demonstrated that P. australis-dominated wetlands support important ecosystem processes and should be regarded as an important carbon sink under an ecosystem services perspective, with the aim to maximize their capacity to mitigate climate change.

Does long-term fire suppression impact leaf litter breakdown and aquatic invertebrate colonization in pine flatwoods wetlands?

Ephemeral wetlands are commonly embedded within pine uplands of the southeastern United States. These wetlands support diverse communities but have often been degraded by a lack of growing-season fires that historically maintained the vegetation structure. In the absence of fire, wetlands develop a dense mid-story of woody vegetation that increases canopy cover and decreases the amount of herbaceous vegetation. To understand how reduced fire frequency impacts wetland processes, we measured leaf litter breakdown rates and invertebrate communities using three common plant species (Longleaf Pine (Pinus palustris), Pineland Threeawn Grass (Aristida stricta), and Black Gum (Nyssa sylvatica)) that occur in pine flatwoods wetlands located on Eglin Air Force Base, Florida. We also tested whether or not the overall habitat type within a wetland (fire maintained or fire suppressed) affected these processes. We placed leaf packs containing 15.0 g of dried leaf litter from each species in both fire-maintained and fire-suppressed sections of three wetlands, removing them after 103–104 days submerged in the wetland. The amount of leaf litter remaining at the end of the study varied across species (N. sylvatica = 7.97 ± 0.17 g, A. stricta = 11.84 ± 0.06 g, and P. palustris = 11.37 ± 0.07 g (mean ± SE)) and was greater in fire-maintained habitat (leaf type: F2,45 = 437.2, P < 0.001; habitat type: F1,45 = 4.6, P = 0.037). We identified an average of 260 ± 33.5 (SE) invertebrates per leaf pack (range: 19–1,283), and the most abundant taxonomic groups were Cladocera, Isopoda, Acariformes, and Diptera. Invertebrate relative abundance varied significantly among litter species (approximately 39.9 ± 9.4 invertebrates per gram of leaf litter remaining in N. sylvatica leaf packs, 27.2 ± 5.3 invertebrates per gram of A. stricta, and 14.6 ± 3.1 invertebrates per gram of P. palustris (mean ± SE)) but not habitat type. However, both habitat (pseudo-F1,49 = 4.30, P = 0.003) and leaf litter type (pseudo-F2,49 = 3.62, P = 0.001) had a significant effect on invertebrate community composition. Finally, this work was part of ongoing projects focusing on the conservation of the critically imperiled Reticulated Flatwoods Salamander (Ambystoma bishopi), which breeds exclusively in pine flatwoods wetlands, and we examined the results as they relate to potential prey items for larval flatwoods salamanders. Overall, our results suggest that the vegetation changes associated with a lack of growing-season fires can impact both invertebrate communities and leaf litter breakdown.

Dynamic FRET-FLIM based screening of signal transduction pathways

Fluorescence Lifetime Imaging (FLIM) is an intrinsically quantitative method to screen for protein–protein interactions and is frequently used to record the outcome of signal transduction events. With new highly sensitive and photon efficient FLIM instrumentation, the technique also becomes attractive to screen, with high temporal resolution, for fast changes in Förster Resonance Energy Transfer (FRET), such as those occurring upon activation of cell signaling. The second messenger cyclic adenosine monophosphate (cAMP) is rapidly formed following activation of certain cell surface receptors. cAMP is subsequently degraded by a set of phosphodiesterases (PDEs) which display cell-type specific expression and may also affect baseline levels of the messenger. To study which specific PDEs contribute most to cAMP regulation, we knocked down individual PDEs and recorded breakdown rates of cAMP levels following transient stimulation in HeLa cells stably expressing the FRET/FLIM sensor, Epac-SH189. Many hundreds of cells were recorded at 5 s intervals for each condition. FLIM time traces were calculated for every cell, and decay kinetics were obtained. cAMP clearance was significantly slower when PDE3A and, to a lesser amount, PDE10A were knocked down, identifying these isoforms as dominant in HeLa cells. However, taking advantage of the quantitative FLIM data, we found that knockdown of individual PDEs has a very limited effect on baseline cAMP levels. By combining photon-efficient FLIM instrumentation with optimized sensors, systematic gene knockdown and an automated open-source analysis pipeline, our study demonstrates that dynamic screening of transient cell signals has become feasible. The quantitative platform described here provides detailed kinetic analysis of cellular signals in individual cells with unprecedented throughput.

Quantifying the response of a functional indicator of ecosystem health to disturbance gradients in New Zealand riverine environments: a meta-analysis

<p><b>In New Zealand, recent policy changes require freshwater managers to take more comprehensive and integrated approaches to monitoring and maintaining ecosystem health. To attempt to prevent and reverse the adverse effects of land use change on freshwater ecosystems, management decisions need to be based upon a suite of indicators each with a strong foundation of knowledge regarding the nature of responses at a national scale. Monitoring ecosystem function in addition to structural indicators has long been suggested to provide a more accurate and holistic narrative of ecosystem health, however, it has yet to be adopted in routine bioassessment. The cotton strip assay has shown promise as a consistent, relatively cheap, and repeatable method for monitoring freshwater ecosystem function, indicating the ecological processing rates of riverine microbial communities and the organic matter processing potential of riverine environments. Numerous regional-scale studies have applied the cotton strip assay in New Zealand, but these data have yet to be explored in unison. For managers to successfully monitor, manage, and restore ecological processes in river environments, a comprehensive understanding of the proximate drivers of cotton breakdown is needed. The aim of this study is to conduct a meta-analysis of cotton strip assay data to explore the relationship between river function and other measures of ecosystem health and land-use stressors at a national scale.</b></p> <p>I collated published and unpublished cotton strip data to create a meta-dataset, with measures harmonised by deployment time and temperature for more meaningful comparisons at a national scale. I sourced additional data from national databases describing water quality and physical river classification information for more comprehensive, higher resolution analyses. I then used the meta-dataset was to investigate the nature of cotton decomposition responses along varying levels of impairment across different seasonal conditions and spatial catchment attributes. </p> <p>I used linear mixed-effects models to determine the relationships between cotton decomposition and physicochemical predictor variables, along with any additional influence attributed to underlying spatial variation across sites. Results suggest that bioavailable nutrients and water clarity are the largest drivers in cotton breakdown rates at a national scale. Water temperature and seasonal conditions emerged as likely limiting factors on microbial activity and cotton breakdown, indicating that consistent intra-seasonal monitoring is advisable. Climate and underlying geology can also be important when looking to discriminate underlying catchment variation and should be incorporated when making larger scale comparisons. Relationships with land use were found to be non-linear and likely to have too many co-varying factors enacting influence on cotton breakdown rates to be successful predictive gradients. Breakdown responses were, however, most consistent under high levels of vegetation cover, and high variability in responses in more urban and pastoral developed catchments. The assays’ sensitivity to nutrient enrichment at a national scale could aid in informing management policies with respect to nutrient limits, and the setting of natural ecosystem processing benchmarks.</p>

Quantifying the response of a functional indicator of ecosystem health to disturbance gradients in New Zealand riverine environments: a meta-analysis

<p><b>In New Zealand, recent policy changes require freshwater managers to take more comprehensive and integrated approaches to monitoring and maintaining ecosystem health. To attempt to prevent and reverse the adverse effects of land use change on freshwater ecosystems, management decisions need to be based upon a suite of indicators each with a strong foundation of knowledge regarding the nature of responses at a national scale. Monitoring ecosystem function in addition to structural indicators has long been suggested to provide a more accurate and holistic narrative of ecosystem health, however, it has yet to be adopted in routine bioassessment. The cotton strip assay has shown promise as a consistent, relatively cheap, and repeatable method for monitoring freshwater ecosystem function, indicating the ecological processing rates of riverine microbial communities and the organic matter processing potential of riverine environments. Numerous regional-scale studies have applied the cotton strip assay in New Zealand, but these data have yet to be explored in unison. For managers to successfully monitor, manage, and restore ecological processes in river environments, a comprehensive understanding of the proximate drivers of cotton breakdown is needed. The aim of this study is to conduct a meta-analysis of cotton strip assay data to explore the relationship between river function and other measures of ecosystem health and land-use stressors at a national scale.</b></p> <p>I collated published and unpublished cotton strip data to create a meta-dataset, with measures harmonised by deployment time and temperature for more meaningful comparisons at a national scale. I sourced additional data from national databases describing water quality and physical river classification information for more comprehensive, higher resolution analyses. I then used the meta-dataset was to investigate the nature of cotton decomposition responses along varying levels of impairment across different seasonal conditions and spatial catchment attributes. </p> <p>I used linear mixed-effects models to determine the relationships between cotton decomposition and physicochemical predictor variables, along with any additional influence attributed to underlying spatial variation across sites. Results suggest that bioavailable nutrients and water clarity are the largest drivers in cotton breakdown rates at a national scale. Water temperature and seasonal conditions emerged as likely limiting factors on microbial activity and cotton breakdown, indicating that consistent intra-seasonal monitoring is advisable. Climate and underlying geology can also be important when looking to discriminate underlying catchment variation and should be incorporated when making larger scale comparisons. Relationships with land use were found to be non-linear and likely to have too many co-varying factors enacting influence on cotton breakdown rates to be successful predictive gradients. Breakdown responses were, however, most consistent under high levels of vegetation cover, and high variability in responses in more urban and pastoral developed catchments. The assays’ sensitivity to nutrient enrichment at a national scale could aid in informing management policies with respect to nutrient limits, and the setting of natural ecosystem processing benchmarks.</p>

Dileucine ingestion is more effective than leucine in stimulating muscle protein turnover in young males: a double blind randomized controlled trial

Leucine is regarded as an anabolic trigger for the mTORC1 pathway and the stimulation muscle protein synthesis rates. More recently, there has been an interest in underpinning the relevance of BCAA-containing dipeptides and their intact absorption into circulation to regulate muscle anabolic responses. We investigated the effects of dileucine and leucine ingestion on postprandial muscle protein turnover. Ten healthy young men (age: 23±3 y) consumed either 2 g of leucine (LEU) or 2 g of dileucine (DILEU) in a randomized crossover design. The participants underwent repeated blood and muscle biopsy sampling during primed continuous infusions of L-[ring-13C6]phenylalanine and L-[15N]phenylalanine to determine myofibrillar protein synthesis (MPS) and mixed muscle protein breakdown rates (MPB), respectively. LEU and DILEU similarly increased plasma leucine net area under the curve (AUC; P = 0.396). DILEU increased plasma dileucine AUC to a greater extent than LEU (P = 0.013). Phosphorylation of Akt (P = 0.002), rpS6 (P <0.001) and p70S6K (P < 0.001) increased over time in both LEU and DILEU conditions. Phosphorylation of 4E-BP1 (P = 0.229) and eEF2 (P = 0.999) did not change over time irrespective of condition. Cumulative (0-180 min) MPS increased in DILEU (0.075±0.032 %⋅hour-1), but not in LEU (0.047±0.029 %⋅hour-1; P=0.023). MPB did not differ between LEU (0.043±0.030 %⋅h-1) and DILEU conditions (0.051±0.027 %⋅hour-1; P = 0.659). Our results showed that dileucine ingestion elevated plasma dileucine concentrations and muscle protein turnover by stimulating MPS in young men.