Ecological implications of fecal pellets produced by the Antarctic krill Euphausia superba in the Antarctic Ocean

Organic analyses and electron microscopic observations on fecal pellets produced by the Antarctic krill Euphausia superba Dana showed that krill fed on choanoflagellates, the abundant heterotrophic flagellate in the Antarctic Ocean. Two new pathways of organic materials in the Antarctic ecosystem are proposed: (1) a new food chain including non-living particulate and dissolved organics, and bacteria-choanoflagellate-krill-vertebrate, which coexists with the traditional diatom-krill-vertebrate food chain; (2) non-phytoplanktonic organic materials in surface waters are transferred into choanoflagellates and are transported to deep water as fecal pellets which are still useful as nutrition for other organisms there.     

Risk evaluation with waste scenario: lead emissions in solder waste treatment

In this work, an estimate of the elevation of airborne lead concentrations via the lead solder contained in domestic electricity installations and an investigation into the effects of human exposure were conducted using a simulation method. The elevation of airborne lead concentrations due to incineration was calculated to be 0.001 µg/m³ maximum. The simulation results of the calculations indicated that blood lead concentrations could reach as high as 10⁻⁵ µg/dl. These concentrations could primarily be attributed to the inhalation of airborne lead particles. In addition, we discuss the influences of lead solder disposal on the ecosystem via soil and water.     

Detecting pigments from colourful eggshells of extinct birds

The known chemical basis of diverse avian eggshell coloration is generated by the same two classes of tetrapyrrole pigments in most living birds. We aimed to extend the evolutionary scope of these patterns by detecting pigments from extinct birds’ eggs. In our samples biliverdin was successfully extracted from subfossil shell fragments of the blue-green egg-laying upland moa Megalapteryx didinus, while protoporphyrin was extracted from the beige eggs of two other extinct moa species. Our data on pigment detection from eggshells of other extant paleognath birds, together with published information on other modern lineages, confirm tetrapyrroles as ubiquitous and conserved pigments contributing to diverse eggshell colours throughout avian evolution.     

More asymmetric tree competition brings about more evapotranspiration and less runoff from the forest ecosystems: A simulation study

The present paper reports how stand size-structure dynamics due to competition between different-sized trees affect long-term forested water balance in Japanese cool-temperate planted stands (evergreen coniferous Cryptomeria japonica and deciduous coniferous Larix kaempferi stands) using a fully coupled multi-layered meteorological surface physics—terrestrial ecosystems model. The simulation captured the well-known annual variation in leaf area index (LAI) accurately with stand age in monocultured and even-aged stands; the occurrence of maximum LAI during the early growth stage and then a gradual decline followed by a steady state after the maximum LAI. The simulations also detected a high dependency of annual evapotranspiration (AETr) on LAI with stand age that is well known by prior observational researches. In the C. japonica (shade-tolerant late-successional species) stand, the relationship between annual net primary productivity of an individual tree (NPP_ind) and individual tree mass (w) changed from linear to a convex curve during self-thinning, indicating that the degree of asymmetric tree competition intensified with forest stand development. The higher degree of competitive asymmetry characterized by the convex-shaped NPPind-w relationship produced greater size inequality, i.e., the formation of trees stratified by height. Under such conditions, AETr and annual transpiration (ATr) were mainly regulated by larger trees. On the other hand, the NPPind-w relationships in the L. kaempferi (shade-intolerant early-successional species) stand were linear throughout the simulated period, indicating the lower degree of competitive asymmetry. Under such conditions, the growth of intermediate-sized trees was enhanced and these trees became a dominant source of AETr (and also ATr) during self-thinning. Furthermore, the sensitivity analysis of the effects of ecophysiological parameters such as foliage profile (i.e., vertical distribution of leaf area density) of an individual tree (distribution pattern is described by the parameter η), the maximum carboxylation velocity (V_cmax0) and biomass allocation pattern of individual plant growth (μ₁) on AETr, ATr and annual runoff (AR_off) showed that the temporal trends of AETr, ATr, AR_off and NPPind-w relationships were completely the same as those in the control simulations. However, the NPPind-w relationship during self-thinning indicated higher degrees of competitive asymmetry when η or V_cmax0 were greater than those in the control simulation and generated greater AETr and ATr and thus smaller AR_off. We found that more asymmetric tree competition brings about greater size inequality between different-sized trees and thus more evapotranspiration and less runoff in a forest stand. Overall, our simulation approach revealed that not only LAI dynamics but also plant competition, and thus size-structure dynamics, in a forest ecosystem are essential to long-term future projections of forested water balance.