Impact of the Flow Velocity and Sedimentation on Microbial Biofilms in the Stream Ilm (Thuringia/Germany)

Streams are linear definite one dimensional structures and several theoretical concepts aiming the stream ecology are existing. The River Continuum Concept (RCC) for instance describes streams as a continuous series of physical gradients and associated biotic adjustments indicating that the stream organisms interact with the longitudinal changing environment (Vannote et al., 1980). The products of streams are highly appropriate to be transported downstream than reaching the river bottom (Schönborn, 2003). Most of the organic matter available in streams is of allochthonious origin, as leaves from the riparian zones (99%). After entering the stream, allochtonious material undergoes three phases of processing: leaching, microbial colonization (conditioning) and fragmentation by physical forces and invertebrate feeding (Fisher and Likens, 1973). The amount of terrestric organic carbon transported or transformed by stream and river ecosystems world wide is about 2 Pg per year whereas the metabolic capacity in these fluvial systems may result from microbial attachements as biofilms (Battin et al., 2008)

Bacterial community composition and extracellular enzyme activity in temperate streambed sediment during drying and rewetting

Droughts are among the most important disturbance events for stream ecosystems; they not only affect stream hydrology but also the stream biota. Although desiccation of streams is common in Mediterranean regions, phases of dryness in headwaters have been observed more often and for longer periods in extended temperate regions, including Central Europe, reflecting global climate change and enhanced water withdrawal. The effects of desiccation and rewetting on the bacterial community composition and extracellular enzyme activity, a key process in the carbon flow of streams and rivers, were investigated in a typical Central European stream, the Breitenbach (Hesse, Germany). Wet streambed sediment is an important habitat in streams. It was sampled and exposed in the laboratory to different drying scenarios (fast, intermediate, slow) for 13 weeks, followed by rewetting of the sediment from the fast drying scenario via a sediment core perfusion technique for 2 weeks. Bacterial community structure was analyzed using CARD-FISH and TGGE, and extracellular enzyme activity was assessed using fluorogenic model substrates. During desiccation the bacterial community composition shifted toward composition in soil, exhibiting increasing proportions of Actinobacteria and Alphaproteobacteria and decreasing proportions of Bacteroidetes and Betaproteobacteria. Simultaneously the activities of extracellular enzymes decreased, most pronounced with aminopeptidases and less pronounced with enzymes involved in the degradation of polymeric carbohydrates. After rewetting, the general ecosystem functioning, with respect to extracellular enzyme activity, recovered after 10 to 14 days. However, the bacterial community composition had not yet achieved its original composition as in unaffected sediments within this time. Thus, whether the bacterial community eventually recovers completely after these events remains unknown. Perhaps this community undergoes permanent changes, especially after harsh desiccation, followed by loss of the specialized functions of specific groups of bacteria

Bridging Restoration Science and Practice: Results and Analysis of a Survey from the 2009 Society for Ecological Restoration International Meeting

Developing and strengthening a more mutualistic relationship between the science of restoration ecology and the practice of ecological restoration has been a central but elusive goal of SERI since its inaugural meeting in 1989. We surveyed the delegates to the 2009 SERI World Conference to learn more about their perceptions of and ideas for improving restoration science, practice, and scientist/practitioner relationships. The respondents' assessments of restoration practice were less optimistic than their assessments of restoration science. Only 26% believed that scientist/practitioner relationships were “generally mutually beneficial and supportive of each other,” and the “science–practice gap” was the second and third most frequently cited category of factors limiting the science and practice of restoration, respectively (“insufficient funding” was first in both cases). Although few faulted practitioners for ignoring available science, many criticized scientists for ignoring the pressing needs of practitioners and/or failing to effectively communicate their work to nonscientists. Most of the suggestions for bridging the gap between restoration science and practice focused on (1) developing the necessary political support for more funding of restoration science, practice, and outreach; and (2) creating alternative research paradigms to both facilitate on-the-ground projects and promote more mutualistic exchanges between scientists and practitioners. We suggest that one way to implement these recommendations is to create a “Restoration Extension Service” modeled after the United States Department of Agriculture's Cooperative Extension Service. We also recommend more events that bring together a fuller spectrum of restoration scientists, practitioners, and relevant stakeholders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79142/1/j.1526-100X.2010.00743.x.pd

Composition and diversity of culturable cyanobacteria in sediment samples from the upper layers of two tropical reservoirs

Benthic cyanobacteria research in high mountain reservoirs remains limited, mainly due to their complexity and knowledge gaps that persist in relation to their ecology in tropical regions. This study aimed to explore the composition, diversity, and toxic potential of cyanobacterial in the upper sediment of two Colombian reservoirs. Our investigation involved multiple methodologies, such as germination experiments, that allowed us to assess the presence and viability of cyanobacteria in upper sediment samples, while the competitive ELISA assay allowed for the quantification of toxins within the cultures. The molecular analysis of Operational Taxonomic Units (OTUs) from subsamples of sediment cultures focused on evaluating cyanobacterial diversity and richness among prokaryotic phyla, and the Phylogenetic analysis of culturable cyanobacteria. Chlorophyll-a measurements confirmed the presence of viable populations in sediment cultures, while microscopic identification demonstrated the growth capacity of cyanobacteria from the orders Nostocales, Chroococcales, Oscillatoriales, and Synechococcales under controlled laboratory conditions. Despite low microcystin levels in culture, the prior detection of mcy genes in direct sediment samples suggests a possible toxic potential of cyanobacterial inhabiting the upper sediments. Community analysis, based on the OTUs abundance, revealed a notably diverse microbial community in both reservoir sediments, with a higher relative abundance of cyanobacteria compared to other prokaryotic phyla. These findings support the hypothesis that surface sediments play a fundamental role as a repository for cyanobacteria that may pose inherent risks to ecosystem health. In conclusion, this research underscores the necessity of further studies to achieve a holistic comprehension of benthic cyanobacteria dynamics in high-mountain tropical reservoirs

The impacts of "run-of-river' hydropower on the physical and ecological condition of rivers

This paper synthesises published literature on run-of-river hydropower, highlighting its potential to affect both the physical and ecological conditions of river systems. The paper considers the limited number of direct studies and reviews a wider literature on the two principal impacts of such schemes on river systems: the introduction or maintenance of in-channel barriers and water abstraction/flow regime alteration. We outline how river systems are likely to be impacted by such schemes and identify the key issues arising from their continued development. Potential mitigation approaches are highlighted and the areas of future research required to adequately address current knowledge gaps are identified