Artificial indoor streams as a method to investigate the impact of chemicals on lotic communities

The potential hazard of chemicals on aquatic communities are generally evaluated by standardised single-species bioassays. Safety assessment is based on results gained from organisms adapted to lentic systems and biological interactions in ecosystems are neglected. While lotic communities are often at first in contact with chemicals, it is astonishing that microcosms with lentic communities are mainly used as a bridge between laboratory bioassays and outdoor aquatic systems. Hence, we established five artificial indoor streams to simulate abiotic factors of small rivers. The closed-circuit system was filled with nutrients added to tap water. Washed pebbles were used as sediment. The dynamics of a simple biocoenoses consisting of aufwuchs, Lumbriculus variegatus Asellus aquaticus and Gammarus fossarum was investigated. The dynamic of aufwuchs and periphyton was determined as dry weight and chlorophyll-a, respectively and qualitatively by pigment pattern. The abundance of different developmental stages of L. variegatus was determined at the end of the experiment as well as the population dynamics of G. fossarum and A. aquaticus. Survival rates of gammarids and juveniles per female were investigated and data were used for modelling the population dynamics. The experiment was carried out to investigate the performance of the established artificial streams and the developed approaches to investigate effects of chemicals on a basic lotic community. The prime reason to establish this approach was to close a gap between complex artificial stream systems and laboratory single species tests to assess the impact of chemicals on the aquatic environment.     

The metabolic demands of swimming behavior influence the evolution of skeletal muscle fiber design in the brachyuran crab family Portunidae

We investigated the influence of intracellular diffusion on muscle fiber design in several swimming and non-swimming brachyuran crabs. Species with sustained swimming behavior had aerobic dark fibers subdivided into small metabolic functional units, creating short diffusion distances necessary to support the high rates of aerobic ATP turnover associated with endurance activity. This dark fiber design was observed in all swimming species including Ovalipes ocellatus, which has apparently evolved swimming behavior independently of other Portunidae. In addition, we observed fiber and subdivision size-dependent differences in organelle distribution. Mitochondria, which rely on oxygen to function, were uniformly distributed in small fibers/subdivisions, but were clustered at the fiber periphery in larger fibers. The inverse pattern was observed for nuclei, which are not oxygen dependent, but rely on the transport of slow diffusing macromolecules. Phylogenetically independent contrast analysis revealed that these relationships were largely independent of phylogeny. Our results demonstrate cellular responses to diffusion that were necessary for the evolution of swimming and that are likely to be broadly applicable.     

Variation in dissolved organic matter controls bacterial production and community composition

An ongoing debate in ecology revolves around how species composition and ecosystem function are related. To address the mechanistic controls of this relationship, we manipulated the composition of dissolved organic matter (DOM) fed to aquatic bacteria to determine effects on both bacterial activity and community composition. Sites along terrestrial to aquatic flow paths were chosen to simulate movement of DOM through catchments, and DOM was fed to downslope and control bacterial communities. Bacterial production was measured, and DOM chemistry and bacterial community composition (using denaturing gradient gel electrophoresis of 16S rRNA genes) were characterized following incubations. Bacterial production, dissolved organic carbon (DOC)-specific bacterial production, and DOC consumption were greatest in mesocosms fed soil water DOM; soil water DOM enhanced lake and stream bacterial production by 320-670% relative to lake and stream controls. Stream DOM added to lake bacteria depressed bacterial production relative to lake controls in the early season (-78%) but not the mid-season experiment. Addition of upslope DOM to stream and lake bacterial communities resulted in significant changes in bacterial community composition relative to controls. In four of five DOM treatments, the bacterial community composition converged to the DOM source community regardless of the initial inoculum. These results demonstrate that shifts in the supply of natural DOM were followed by changes in both bacterial production and community composition, suggesting that changes in function are likely predicated on at least an initial change in the community composition. The results indicate that variation in DOM composition of soil and surface waters influences bacterial community dynamics and controls rates of carbon processing in set patterns across the landscape.     

Climate and air quality-driven scenarios of ozone and aerosol precursor abatement

In addition to causing domestic and regional environmental effects, many air pollutants contribute to radiative forcing (RF) of the climate system. However, climate effects are not considered when cost-effective abatement targets for these pollutants are established, nor are they included in current international climate agreements. We construct air pollution abatement scenarios in 2030 which target cost-effective reductions in RF in the EU, USA, and China and compare these to abatement scenarios which instead target regional ozone effects and particulate matter concentrations. Our analysis covers emissions of PM (fine, black carbon and organic carbon), SO₂, NO_x, CH₄, VOCs, and CO. We find that the effect synergies are strong for PM/BC, VOC, CO and CH₄. While an air quality strategy targeted at reducing ozone will also reduce RF, this will not be the case for a strategy targeting particulate matter. Abatement in China dominates RF reduction, but there are cheap abatement options also available in the EU and USA. The justification for international cooperation on air quality issues is underlined when the co-benefits of reduced RF are considered. Some species, most importantly SO₂, contribute a negative forcing on climate. We suggest that given current knowledge, NO_x and SO₂ should be ignored in RF-targeted abatement policies.     

Land cover composition determinants in the Uckermark (NE Germany) over a 220-year period

There is broad consensus that land use/cover has changed in central Europe over millennia. However, few studies have addressed the roles of the anthropogenic (socio-economic) and natural (biophysical) factors driving these changes over shorter periods (e.g., 100 years). In this study, we analyse the determinants of land cover composition at three discrete time periods (c. 1780, 1890, and 2000). We hypothesise that different anthropogenic and natural factors are the determinants of the main land cover types (arable fields, grasslands, and forests) and that the effects of natural and anthropogenic factors on the main land cover types differ among landscapes with highly dynamic and more stable forest-open land distributions. The study was carried out in the Uckermark region located in northeastern Germany. We compiled data on natural and anthropogenic factors (e.g. forest cover and number of inhabitants) of 65 municipalities in four landscape sections of equal size (10 × 10 km). Landscape sections were selected to reflect different dynamics (high/low) in conversion from forest to arable fields or grasslands and vice versa from 1780 to 2000. Averaged linear mixed-effect models explained between 7.5 and 81.2 % of the variance. The unique effect of anthropogenic factors varied from 2.1 to 18.7 % and that of natural factors varied from 0.2 to 43.4 %. In four of six models that included both types of factors, the natural factors were more influential than the anthropogenic factors. Except in three cases, anthropogenic and natural factors showed opposite effects on land cover types in more dynamic and more stable windows. Though the Uckermark region has been influenced by human activity for thousands of years, natural factors were a major determinant of land cover composition during all time periods, whereas anthropogenic factors became more important only during the latest time period under investigation.     

A dominant coalition and policy change: an analysis of shale oil and gas politics in India

This paper identifies the coalitions involved in the topic of shale oil and gas development in India and identifies the circumstances surrounding a change in policy in 2013 by the Ministry of Petroleum and Natural Gas to promote shale exploration. Using the Advocacy Coalition Framework as the theoretical lens, the data are collected primarily from newspaper articles from 2010 to 2015 to identify coalitions, including actors’ positions, priorities, and interactions. The findings show the presence of a dominant advocacy coalition in favor of shale oil and gas development with priorities about energy security and a regulatory framework. The findings indicate some internal coalition disagreement, but stronger internal coalition agreement. Policy change was preceded by a spike in disagreement internal to the dominant coalition. This paper shows how a change in a dominant coalition can precede a change in policy, offers a replicable method of identifying and measuring coalitions via newspaper content analysis, provides a rare application of the Advocacy Coalition Framework outside of North America and Western Europe, and provides evidence of support for shale oil and gas development in India.