UMP clinched 9 medals at BioMalaysia 2011

Universiti Malaysia Pahang (UMP) continued to record successful achievements by garnering a gold medal, a silver medal and seven bronze medals at the BioMalaysia 2011 and Pacific RIM Summit on Industry and BioEnergy 2011 in Kuala Lumpur recently. The event was officially opened by Prime Minister Dato’ Sri Mohd Najib Tun Razak at Kuala Lumpur Convention Centre on November 21, 2011

Quantity and Quality Limit Detritivore Growth: Mechanisms Revealed by Ecological Stoichiometry and Co-Limitation Theory

Resource quantity and quality are fundamental bottom-up constraints on consumers. Best understood in autotroph-based systems, co-occurrence of these constraints may be common but remains poorly studied in detrital-based systems. Here, we used a laboratory growth experiment to test limitation of the detritivorous caddisfly larvae Pycnopsyche lepida across a concurrent gradient of oak litter quantity (food supply) and quality (phosphorus : carbon [P:C ratios]). Growth increased simultaneously with quantity and quality, indicating co-limitation across the resource gradients. We merged approaches of ecological stoichiometry and co-limitation theory, showing how co-limitation reflected shifts in C and P acquisition throughout homeostatic regulation. Increased growth was best explained by elevated consumption rates and improved P assimilation, which both increased with elevated quantity and quality. Notably, C assimilation efficiencies remained unchanged and achieved maximum 18% at low quantity despite pronounced C limitation. Detrital C recalcitrance and substantive post-assimilatory C losses probably set a minimum quantity threshold to achieve positive C balance. Above this threshold, greater quality enhanced larval growth probably by improving P assimilation toward P-intensive growth. We suggest this interplay of C and P acquisition contributes to detritivore co-limitation, highlighting quantity and quality as potential simultaneous bottom-up controls in detrital-based ecosystems, including under anthropogenic change like nutrient enrichment

Algal-Mediated Priming Effects on the Ecological Stoichiometry of Leaf Litter Decomposition: A Meta-Analysis

In aquatic settings, periphytic algae exude labile carbon (C) that can significantly suppress or stimulate heterotrophic decomposition of recalcitrant C via priming effects. The magnitude and direction of priming effects may depend on the availability and stoichiometry of nutrients like nitrogen (N) and phosphorus (P), which can constrain algal and heterotrophic activity; in turn, priming may affect heterotrophic acquisition not only of recalcitrant C, but also N and P. In this study, we conducted a meta-analysis of algal-mediated priming across leaf litter decomposition experiments to investigate (1) bottom-up controls on priming intensity by dissolved N and P concentrations, and (2) effects of algal-mediated priming on the fate of litter-periphyton N and P during decomposition. Across a total of nine datasets, we quantified priming intensity and tested algal effects on litter-periphyton C:N, C:P, and N- and P-specific mass loss rates. Algal effect sizes did not significantly differ from zero, indicating weak or inconsistent algal effects on litter-periphyton stoichiometry and nutrient loss. These findings were likely due to wide variation in algal priming intensity across a limited number of experiments, ranging from strongly negative (410% reduced decomposition) to strongly positive (104% increased decomposition). Correlation and response surface analyses showed that priming intensity switched from negative to positive with increasing dissolved inorganic N:P across datasets. Algal effects on litter-periphyton stoichiometry and nutrient loss further co-varied with dissolved N:P across datasets, suggesting algae most strongly influence the stoichiometry of decomposition under imbalanced N:P, when priming is most intense. Our findings from this limited meta-analysis support the need for additional tests of aquatic priming effects, especially across gradients of N and P availability, with consideration of coupled C and nutrient dynamics during priming of organic matter decomposition

Brown Meets Green: Light and Nutrients Alter Detritivore Assimilation of Microbial Nutrients From Leaf Litter

In aquatic detrital-based food webs, research suggests that autotroph-heterotroph microbial interactions exert bottom-up controls on energy and nutrient transfer. To address this emerging topic, we investigated microbial responses to nutrient and light treatments during Liriodendron tulipifera litter decomposition and fed litter to the caddisfly larvae Pycnopsyche sp. We measured litter-associated algal, fungal, and bacterial biomass and production. Microbes were also labeled with 14C and 33P to trace distinct microbial carbon (C) and phosphorus (P) supporting Pycnopsyche assimilation and incorporation (growth). Litter-associated algal and fungal production rates additively increased with higher nutrient and light availability. Incorporation of microbial P did not differ across diets, except for higher incorporation efficiency of slower-turnover P on low-nutrient, shaded litter. On average, Pycnopsyche assimilated fungal C more efficiently than bacterial or algal C, and Pycnopsyche incorporated bacterial C more efficiently than algal or fungal C. Due to high litter fungal biomass, fungi supported 89.6–93.1% of Pycnopsyche C growth, compared to 0.2% to 3.6% supported by bacteria or algae. Overall, Pycnopsyche incorporated the most C in high nutrient and shaded litter. Our findings affirm others\u27 regarding autotroph-heterotroph microbial interactions and extend into the trophic transfer of microbial energy and nutrients through detrital food webs

Detrital Nutrient Content and Leaf Species Differenitally Affect Growth and Nutritional Regulation of Detritivores

© 2018 The Authors Resource nutrient content and identity are common bottom–up controls on organismal growth and nutritional regulation. One framework to study these factors, ecological stoichiometry theory, predicts that elevated resource nitrogen (N) and phosphorus (P) contents enhance organism growth by alleviating constraints on N and P acquisition. However, the regulatory mechanisms underlying this response – including whether responses depend on resource identity – remain poorly understood. In this study, we tested roles of detrital N and P contents and identity (leaf species) in constraining growth of aquatic invertebrate detritivores. We synthesized results from seven detritivore species fed wide nutrient gradients of oak and maple detritus in the laboratory. Across detritivore taxa, we used a meta-analytic approach quantifying effects of detrital leaf species and N and P contents on growth, consumption, and N- and P-specific assimilation and growth efficiencies. Detritivore growth rates increased on higher-N and P detritus and on oak compared to maple detritus. Notably, the mechanisms of improved growth differed between the responses to detrital nutrients versus leaf species, with the former driven by greater consumption rates despite lower assimilation efficiencies on higher-nutrient detritus, and the latter driven by improved N and P assimilation and N growth efficiencies on oak detritus. These findings suggest animal nutrient acquisition changes flexibly in response to resource changes, altering the fate of detrital N and P throughout regulation. We affirm resource identity and nutrients as important bottom–up controls, but suggest these factors act through separate pathways to affect organism growth and thereby change detrital ecosystems under anthropogenic forest compositional change and nutrient enrichment

Algal-Mediated Priming Effects on the Ecological Stoichiometry of Leaf Litter Decomposition: A Meta-Analysis

In aquatic settings, periphytic algae exude labile carbon (C) that can significantly suppress or stimulate heterotrophic decomposition of recalcitrant C via priming effects. The magnitude and direction of priming effects may depend on the availability and stoichiometry of nutrients like nitrogen (N) and phosphorus (P), which can constrain algal and heterotrophic activity; in turn, priming may affect heterotrophic acquisition not only of recalcitrant C, but also N and P. In this study, we conducted a meta-analysis of algal-mediated priming across leaf litter decomposition experiments to investigate (1) bottom-up controls on priming intensity by dissolved N and P concentrations, and (2) effects of algal-mediated priming on the fate of litter-periphyton N and P during decomposition. Across a total of nine datasets, we quantified priming intensity and tested algal effects on litter-periphyton C:N, C:P, and N- and P-specific mass loss rates. Algal effect sizes did not significantly differ from zero, indicating weak or inconsistent algal effects on litter-periphyton stoichiometry and nutrient loss. These findings were likely due to wide variation in algal priming intensity across a limited number of experiments, ranging from strongly negative (410% reduced decomposition) to strongly positive (104% increased decomposition). Correlation and response surface analyses showed that priming intensity switched from negative to positive with increasing dissolved inorganic N:P across datasets. Algal effects on litter-periphyton stoichiometry and nutrient loss further co-varied with dissolved N:P across datasets, suggesting algae most strongly influence the stoichiometry of decomposition under imbalanced N:P, when priming is most intense. Our findings from this limited meta-analysis support the need for additional tests of aquatic priming effects, especially across gradients of N and P availability, with consideration of coupled C and nutrient dynamics during priming of organic matter decomposition

Periphytic Algae Decouple Fungal Activity From Leaf Litter Decomposition Via Negative Priming

1. Well‐documented in terrestrial settings, priming effects describe stimulated heterotrophic microbial activity and decomposition of recalcitrant carbon by additions of labile carbon. In aquatic settings, algae produce labile exudates which may elicit priming during organic matter decomposition, yet the directions and mechanisms of aquatic priming effects remain poorly tested. 2. We tested algal‐induced priming during decomposition of two leaf species of contrasting recalcitrance, Liriodendron tulipifera and Quercus nigra, in experimental streams under light or dark conditions. We measured litter‐associated algal, bacterial, and fungal biomass and activity, stoichiometry, and litter decomposition rates over 43 days. 3. Light increased algal biomass and production rates, in turn increasing bacterial abundance 141%–733% and fungal production rates 20%–157%. Incubations with a photosynthesis inhibitor established that algal activity directly stimulated fungal production rates in the short term. 4. Algal‐stimulated fungal production rates on both leaf species were not coupled to long‐term increases in fungal biomass accrual or litter decomposition rates, which were 154%–157% and 164%–455% greater in the dark, respectively. The similar patterns on fast‐ vs. slow‐decomposing L. tulipifera and Q. nigra, respectively, indicated that substrate recalcitrance may not mediate priming strength or direction. 5. In this example of negative priming, periphytic algae decoupled fungal activity from decomposition, likely by providing labile carbon invested towards greater fungal growth and reproduction instead of recalcitrant carbon degradation. If common, algal‐induced negative priming could stimulate heterotrophy reliant on labile carbon yet suppress decomposition of recalcitrant carbon, modifying energy and nutrients available to upper trophic levels and enhancing organic carbon storage or export in well‐lit aquatic habitats

Global Patterns and Controls of Nutrient Immobilization On Decomposing Cellulose In Riverine Ecosystems

Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature