Session A3: Think Big: Adding Large Structures To Improve Ecosystem Health

Abstract: The Vindel River is one of the few freeflowing its entire catchment are part of the Natura 2000 network. The river was exploited for timber floating between 1850–1976; rapids in the main channel and tributaries below the alpine tree line were channelized to increase timber transport capacity. Side channels were cut off and the flow was concentrated to a single channel from which boulders and large wood were removed. Hence, previously heterogeneous environments were replaced by more homogeneous systems with limited habitat for riverine species. The Vindel River LIFE project (LIFE08 NAT/S/000266) works with the restoration of 25 tributaries in the Vindel River system. The project strives to alleviate the effects of fragmentation and channelization in affected rapids, to improve the quality of water and riparian habitats. The work has included the construction of over 1000 spawning grounds for brown trout, removal of 17 splash dams, the relocation of rocks into the channels, and the strategic placement of large boulders and dead wood in over 50 km of river. Follow up studies have been done in the channels that have been restored with “demonstration methods,” where previously best-practice restored reaches have been re-restored by adding large boulders and large wood (i.e., entire trees, including root wads) from adjacent upland to the channel. The demonstration restoration has generated wider and more complex streams, which in turn has led to more variable water flow and higher water levels. This will decrease the risk of erosion during high flow and reduce the risk of losing spawning areas. However, fish population data collected by electrofishing before and after restoration show very inconsistent results among tributaries. This highlights the need for considering potential catchment scale degradation and not only concentrating on reach scale problems in order to re-establish ecosystem health

Passive dosing of triclosan in multi-generation tests with copepods - Stable exposure concentrations and effects at the low µg l^-1 range

Ecotoxicity testing is a crucial component of chemical risk assessment. Still, due to methodological difficulties related to controlling exposure concentrations over time, data on long-term effects of organic chemicals at low concentrations are limited. The aim of the present study was, therefore, to test the applicability of passive dosing to maintain stable concentrations of the organochlorine bacteriocide triclosan in the water phase during a 6-wk multigeneration population development test with the harpacticoid copepod Nitocra spinipes. Triclosan was loaded into silicone (1000 mg), which was used as passive dosing phase in the exposure vials. The distribution ratio for triclosan between silicone and water (Dsilicone-water) was 10466 +/- 1927. A population development test was conducted at 3 concentration levels of triclosan that were measured to be 3 mu g/L to 5 mu g/L, 7 mu g/L to 11 mu g/L and 16 mu g/L to 26 mu g/L. The results demonstrate that passive dosing is applicable for long-term ecotoxicity testing of organic chemicals, including during significant growth of the test organism population. Shifts in the demographic structure of the population during exposure suggest the most severe effects were exerted on juvenile development. Progressively lower development index values in the populations exposed to increasing triclosan concentrations suggest developmental retardation. The results further stress the need for chronic exposure during ecotoxicity testing in chemical risk assessment because even the most sensitive endpoint was not significant until after 7 d of exposure.</p

Metabolic control of arginine and ornithine levels paces the progression of leaf senescence

Pools of arginine and ornithine generated during protein degradation can pace the progression of leaf senescence by affecting the TCA cycle, polyamine biosynthesis and the ethylene signaling pathway.Leaf senescence can be induced by stress or aging, sometimes in a synergistic manner. It is generally acknowledged that the ability to withstand senescence-inducing conditions can provide plants with stress resilience. Although the signaling and transcriptional networks responsible for a delayed senescence phenotype, often referred to as a functional stay-green trait, have been actively investigated, very little is known about the subsequent metabolic adjustments conferring this aptitude to survival. First, using the individually darkened leaf (IDL) experimental setup, we compared IDLs of wild-type (WT) Arabidopsis (Arabidopsis thaliana) to several stay-green contexts, that is IDLs of two functional stay-green mutant lines, oresara1-2 (ore1-2) and an allele of phytochrome-interacting factor 5 (pif5), as well as to leaves from a WT plant entirely darkened (DP). We provide compelling evidence that arginine and ornithine, which accumulate in all stay-green contexts-likely due to the lack of induction of amino acids (AAs) transport-can delay the progression of senescence by fueling the Krebs cycle or the production of polyamines (PAs). Secondly, we show that the conversion of putrescine to spermidine (SPD) is controlled in an age-dependent manner. Thirdly, we demonstrate that SPD represses senescence via interference with ethylene signaling by stabilizing the ETHYLENE BINDING FACTOR1 and 2 (EBF1/2) complex. Taken together, our results identify arginine and ornithine as central metabolites influencing the stress- and age-dependent progression of leaf senescence. We propose that the regulatory loop between the pace of the AA export and the progression of leaf senescence provides the plant with a mechanism to fine-tune the induction of cell death in leaves, which, if triggered unnecessarily, can impede nutrient remobilization and thus plant growth and survival

Distribution of Pyruvate Dehydrogenase Complex Activities between Chloroplasts and Mitochondria from Leaves of Different Species.

Protoplasts from barley (Hordeum vulgare), pea (Pisum sativum), wheat (Triticum aestivum), and spinach (Spinacia oleracea) leaves were fractionated into chloroplast- and mitochondrion-enriched fractions. Pyruvate dehydrogenase complex capacities in mitochondria (mtPDC) and chloroplasts (cpPDC) were measured in appropriate fractions under conditions optimal for each isozyme. The total cellular capacity of PDC was similar in barley and pea but about 50% lower in wheat and spinach. In pea a distribution of 87% mtPDC and 13% cpPDC was found on a cellular basis. In barley, wheat, and spinach the subcellular distribution was the opposite, with about 15% mtPDC and 85% cpPDC. cpPDC activity was constant at about 0.1 nmol cell-1 h-1 in cells from different regions along the developing barley leaf and showed no correlation with developmental patterns of photosynthetic parameters, such as increasing Chl and NADP-glyceraldehyde-3-phosphate dehydrogenase activity. Similarly, the capacity of the mitochondrial isoform did not change during barley leaf development and had a developmental pattern similar to that of citrate synthase and fumarase. Differences in subcellular distribution of PDCs in barley and pea are proposed to be due to differences in regulation, not to changes in isozyme proportions during leaf development or to species-specific differences in phosphorylation state of mtPDC after organelle separation