Litter Quality Is a Stronger Driver than Temperature of Early Microbial Decomposition in Oligotrophic Streams: a Microcosm Study

Litter decomposition is an ecological process of key importance for forest headwater stream functioning, with repercussions for the global carbon cycle. The process is directly and indirectly mediated by microbial decomposers, mostly aquatic hyphomycetes, and influenced by environmental and biological factors such as water temperature and litter quality. These two factors are forecasted to change globally within the next few decades, in ways that may have contrasting effects on microbial-induced litter decomposition: while warming is expected to enhance microbial performance, the reduction in litter quality due to increased atmospheric carbon dioxide and community composition alteration may have the opposite outcome. We explored this issue through a microcosm experiment focused on early microbial-mediated litter decomposition under stream oligotrophic conditions, by simultaneously manipulating water temperature (10 °C and 15 °C) and litter quality (12 broadleaf plant species classified into 4 categories based on initial concentrations of nitrogen and tannins). We assessed potential changes in microbial-mediated litter decomposition and the performance of fungal decomposers (i.e., microbial respiration, biomass accrual, and sporulation rate) and species richness. We found stronger effects of litter quality, which enhanced the performance of microbial decomposers and decomposition rates, than temperature, which barely influenced any of the studied variables. Our results suggest that poorer litter quality associated with global change will have a major repercussion on stream ecosystem functioning.

Fungal richness does not buffer the effects of streams salinization on litter decomposition

Freshwater salinization is a world-wide phenomenon threatening stream communities and ecosystem functioning. In these systems, litter decomposition is a main ecosystem-level process where fungi (aquatic hyphomycetes) play a central role linking basal resource and higher levels of food-web. The current study evaluated the impact of aquatic hyphomycete richness on leaf litter decomposition when subjected to salinization. In a microcosm study, we analysed leaf mass loss, fungal biomass, respiration and sporulation rate by fungal assemblages at three levels of species richness (1, 4, 8 species) and three levels of salinity (0, 8, 16 g NaCl L‑1). Mass loss and sporulation rate were depressed at 8 and 16 g NaCl L‑1, while fungal biomass and respiration were only negatively affected at 16 g L‑1. A richness effect was only observed on sporulation rates, with the maximum values found in assemblages of 4 species. In all cases, the negative effects of high levels of salinization on the four tested variables superimposed the potential buffer capacity of fungal richness. The study suggests functional redundancy among the fungal species even at elevated salt stress conditions which may guarantee stream functioning at extreme levels of salinity. Nonetheless, it also points to the possible importance of salt induced changes on fungal diversity and identity in salinized streams able to induce bottom-up effects in the food webs.

Cognitive Visual Dysfunctions in Children with Autism Spectrum Disorders and Other Developmental Delays

Background: Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by a triad of social, communicative, and imaginative impairments. Although early detection and intervention are important to improve functional outcomes in ASD, similar features between ASD and other developmental delays may impede timely diagnosis. In this study, we aimed to investigate the feasibility of Cognitive Visual Assessment Questionnaire (CVAQ) in differentiating ASD from other developmental delays.Methods: We retrospectively reviewed the medical records of 115 pediatric patients (80 males, 35 females) with ASD and other developmental delays who had the Modified Checklist for Autism in Toddlers (M-CHAT) and CVAQ performed at Uijeongbu St. Mary's Hospital from January 2017 to June 2019. Results: The mean age at M-CHAT and CVAQ was 31.8 months (range, 14.1 – 48). The proportion of ASD was significantly higher in patients with screen-positive M-CHAT than those with screen-negative M-CHAT (P = 0.035). The sensitivity of CVAQ for detecting ASD was 83.3% and 94.1% in 14.1 – <24 months and 24 – <36 months age groups, respectively. Among patients with screen-negative M-CHAT, the mean number of failed tasks related to dorsal stream pathway was greater in ASD compared to other developmental delays, although the differences were not statistically significant (P = 0.437).Conclusions: Our study demonstrates that autistic individuals may have a specific impairment in dorsal stream functioning. CVAQ also showed improved sensitivity for detecting ASD in toddlers. When coupled with clinical observation and judgement, CVAQ is a useful alternative screening tool for differentiating ASD from other developmental delays in young children.