Eutrophication of Lake Hayq in the Ethiopian Highlands

Lake Hayq was previously described as having exceptionally clearwater and very low phytoplankton biomass. It is now very different,with a shallow euphotic depth and abundant phytoplankton. Zooplanktonpopulations have changed as well; Daphnia and Diaphanosoma wererecorded before, whereas we found no Cladocera. Among the possiblecauses for this change in trophic status is the introductionof the planktivorous fish Oreochromis niloticus.     

Identification of Amino Acids in the N-Terminal Domain of Corticotropin-Releasing Factor Receptor 1 that Are Important Determinants of High-Affinity Ligand Binding

Abstract : The aim of the present study was to identify the N-terminal regions of human corticotropin-releasing factor (CRF) receptor type 1 (hCRF-R1) that are crucial for ligand binding. Mutant receptors were constructed by replacing specific residues in hCRF-R1 with amino acids from the corresponding position in the N-terminal region of the human vasoactive intestinal peptide receptor type 2 (hVIP-R2). In cyclic AMP stimulation and CRF binding assays, it was established that two regions within the N-terminal domain were crucial for the binding of CRF receptor agonists and antagonists : one region mapping to amino acids 43-50 and a second amino acid sequence extending from position 76 to 84 of hCRF-R1. Recently, it was found that the latter sequence plays a very important role in determining the high ligand selectivity of the Xenopus CRF-R1 (xCRF-R1). Replacement of amino acids 76-84 of hCRF-R1 with residues from the same segment of the hVIP-R2 N terminus markedly reduced the binding affinity of CRF ligands. Mutation of Arg⁷⁶ or Asn⁸¹ but not Gly⁸³ of hCRF-R1 to the corresponding amino acids of xCRF-R1 or hVIP-R2 resulted in 100-1,000-fold lower affinities for human/rat CRF, rat urocortin, and astressin. These data underline the importance of the N-terminal domain of CRF-R1 in high-affinity ligand binding.     

Eutrophication history of Lake Arendsee (Germany)

At the maximum depth of Lake Arendsee (49.5 m) only a thanatocenosis could be found in a freeze core with a length of 52 cm. According to varve-counting, the fauna changed between 1960 and 1972, characteristic of mesotrophic to eutrophic state. The cause for eutrophication could be correlated with the sewage loading of the town of Arendsee and the drainage of Lake Fauler See into Lake Arendsee. Lake Arendsee did not yet recover from the loading because of the long retention time of 114 years. The investigation of the living meio- and macrobenthos of Lake Arendsee shows that the lower profundal is not colonized.     

杭州西湖富营养化模型的不确定性分析

运用结合了灵敏度分析的Monte Carlo方法对西湖富营养化生态模型不确定性进行了定量分析．通过模型不确定性分析,为管理决策者提供了有价值的信息,包括模型输出值的统计分布信息以及各种管理策略和整治措施所能实现目标的可能性方面的信息．根据这些信息,管理者可以客观评价并选择合适的管理策略和整治措施,在可接受的风险水平上进行决策．     

Eutrophication of Lake Geneva indicated by the oligochaete communities of the profundal

Primary production rates and total phosphorus concentrations indicated that Lake Geneva (Switzerland) was meso-eutrophic from 1970 to 1983. Worm communities of the profundal (50–309 m deep) were very similar in 1978 and 1983. Species numerically dominant in eutrophic lakes — such as Potamothrix hammoniensis, P. heuscheri and Tubifex tubifex — constituted the bulk (75%) of the communities. Species numerically dominant in mesotrophic lakes (mostly Potamothrix vejdovskyi) or in oligotrophic lakes (mostly Stylodrilus heringianus) constituted respectively 18% and 7% of the worm communities. The dominance of eutrophic species increased with depth in the whole lake; it increased also in the eastern region of the lake which is directly exposed to the heavy organic inputs of the Rhône River. Oligotrophic and mesotrophic species decreased along the same gradients. Species dominant in oligotrophic lakes were absent in 1978 and 1983 from the deepest area of Lake Geneva (300–309 m) whereas they constituted therein 25% of worm communities in 1967. Data based on worm species groups — i.e. species with similar resistance to eutrophication pooled together — were more easy to analyse statistically than those based on the isolated species. Thus, the relative abundance of three species groups, expressed in several ways, can indicate precisely the trophic state of a lake.     

Eutrophication of Lake Neuchâtel indicated by the oligochaete communities

Lake Neuchâtel (Switzerland), oligotrophic until 1950, was meso-eutrophic in 1980. The relative abundance in worm communities of Peloscolex velutinus and Stylodrilus heringianus was used to monitor the trophic state of the lake. In 1980, the median relative abundance of these oligotrophic species was 9% in the whole of Lake Neuchâtel compared with 70% in oligotrophic lakes, 35% in mesotrophic lakes, and 0% in eutrophic lakes. The scarcity of oligotrophic species in the deepest area (153 m) characterized better the meso-eutrophic state of Lake Neuchâtel than oxygen concentrations which never descended below 6 mg·1^-1. Location of the area within the lake from where worms were sampled was of critical importance to assess the trophic state: some areas reflected the past rather than the present state of the lake.     

Eutrophication and macrophyte species richness in the large shallow North-European Lake Peipsi

We present an overview of long-term changes in the floristic composition and growth areas in L. Peipsi (3555 km², unregulated water level) that have occurred since the 1960s and a list of plant taxa containing 140 species of higher plants and 4 charophytes. A significant correlation was found between the relative abundance and frequency per stations (Fs) (Rs = 0.93). Data on five inhabitants of the eulittoral revealed significant (p < 0.05) inter-annual differences in Fs. Comparison of the data of Fs for 67 taxa for 1970-1980 (87 stations) and 1997-2007 (139 stations) showed a significant change in the Fs distribution (p < 0.03) and a decline (p < 0.05) for 20 taxa; for 15 species Fs had decreased two times or more. However, 14 of the markedly declined taxa, e.g. the long-term dominating submergent Potamogeton perfoliatus, belong still among the top 33 in the list. A significant (χ² = 11.8; p < 0.028) change was observed in the species number of different frequency classes. The number of taxa in the Fs class 46-100 (92)% was 17 in 1970-1980 but only 3 in 1997-2007. The top of the list of macrophytes is dominated by circumpolar species and vicariants. Impoverishment of the flora in the course of eutrophication is expressed by the decrease in Fs; at the same time, the total number of species had not changed. Among the 20 declined taxa 14 are characteristic of the temporarily flooded and/or shallow-water zone of eutrophic water bodies (amphibious and emergent plants); the remaining taxa are shallow-water submergents. The simpliest explanation for their decrease is the expansion of thick reeds occupying suitable eulittoral habitats.     

Temporal ecology in the Anthropocene

Two fundamental axes – space and time – shape ecological systems. Over the last 30 years spatial ecology has developed as an integrative, multidisciplinary science that has improved our understanding of the ecological consequences of habitat fragmentation and loss. We argue that accelerating climate change – the effective manipulation of time by humans – has generated a current need to build an equivalent framework for temporal ecology. Climate change has at once pressed ecologists to understand and predict ecological dynamics in non‐stationary environments, while also challenged fundamental assumptions of many concepts, models and approaches. However, similarities between space and time, especially related issues of scaling, provide an outline for improving ecological models and forecasting of temporal dynamics, while the unique attributes of time, particularly its emphasis on events and its singular direction, highlight where new approaches are needed. We emphasise how a renewed, interdisciplinary focus on time would coalesce related concepts, help develop new theories and methods and guide further data collection. The next challenge will be to unite predictive frameworks from spatial and temporal ecology to build robust forecasts of when and where environmental change will pose the largest threats to species and ecosystems, as well as identifying the best opportunities for conservation.     

Legacies of recent environmental change in the benthic communities of Lake Joyce, a perennially ice-covered Antarctic lake

Many Antarctic lakes provide habitat for extensive microbial mats that respond on various timescales to environmental change. Lake Joyce contains calcifying microbialites and provides a natural laboratory to constrain how environmental changes influence microbialite development. In Lake Joyce, depth-specific distributions of calcitic microbialites, organic carbon, photosynthetic pigments and photosynthetic potential cannot be explained by current growth conditions, but are a legacy of a 7-m lake level rise between 1973 and 2009. In the well-illuminated margins of the lake, photosynthetically active benthic communities colonised surfaces submerged for just a few years. However, observed increases in accumulated organic material with depth from 5 to 20 m (2-40 mg ash-free dry weight cm(-2)) and the presence of decimetre-scale calcite microbialites at 20-22 m depth, apparently related to in situ photosynthetic growth, are inconsistent with the current distributions of irradiance, photosynthetic pigments and mat photosynthetic potential (as revealed by pulse-amplitude-modulated fluorometry). The microbialites appeared photosynthetically active in 1986 and 1997, but were outside the depth zone where significant phototrophic growth was possible and were weakly photosynthetically competent in 2009. These complex microbial structures have persisted after growth has ceased, demonstrating how fluctuating environmental conditions and the hysteresis between environmental change, biological response and microbialite development can be important factors to consider when interpreting modern, and by inference ancient, microbially mediated structures.     

Reversibility of Man-Induced Eutrophication. Experiences of a Lake Recovery Study in Sweden

Recovery of polluted lakes is a complicated process involving many factors. Different lake rehabilitation techniques and former experiences with advanced wastewater treatment and sewage diversion are reviewed. The response in water quality after a nutrient reduction may vary significantly, despite a lowering of the phosphorus concentration in the lake. The different factors influencing the process, such as climatic fluctuations, the growth-limiting effect of nutrients and phosphorus release from the sediments, are discussed, based on examples from a lake recovery study in Sweden carried out in 30 lakes. Due to various interrelationships between physical characteristics and biological mechanisms involved, and to significant fluctuations in these factors from one year to the next, it is difficult to generalize and to forecast the actual response of a certain water body to a reduced nutrient input. Unfortunately, too many monitoring programmes aimed at elucidating the effects of remedial efforts are not designed in such a manner that relevant information can be obtained about the nutrient load — lake response relationships. Ways for optimizing and increasing the predictive power of inventory studies and monitoring programmes are discussed.     

Expanding insect pollinators in the Anthropocene

Global changes are severely affecting pollinator insect communities worldwide, resulting in repeated patterns of species extirpations and extinctions. Whilst negative population trends within this functional group have understandably received much attention in recent decades, another facet of global changes has been overshadowed: species undergoing expansion. Here, we review the factors and traits that have allowed a fraction of the pollinating entomofauna to take advantage of global environmental change. Sufficient mobility, high resistance to acute heat stress, and inherent adaptation to warmer climates appear to be key traits that allow pollinators to persist and even expand in the face of climate change. An overall flexibility in dietary and nesting requirements is common in expanding species, although niche specialization can also drive expansion under specific contexts. The numerous consequences of wild and domesticated pollinator expansions, including competition for resources, pathogen spread, and hybridization with native wildlife, are also discussed. Overall, we show that the traits and factors involved in the success stories of expanding pollinators are mostly species specific and context dependent, rendering generalizations of ‘winning traits’ complicated. This work illustrates the increasing need to consider expansion and its numerous consequences as significant facets of global changes and encourages efforts to monitor the impacts of expanding insect pollinators, particularly exotic species, on natural ecosystems.     

Daily activity timing in the Anthropocene

Animals are facing novel ‘timescapes’ in which the stimuli entraining their daily activity patterns no longer match historical conditions due to anthropogenic disturbance. However, the ecological effects (e.g., altered physiology, species interactions) of novel activity timing are virtually unknown. We reviewed 1328 studies and found relatively few focusing on anthropogenic effects on activity timing. We suggest three hypotheses to stimulate future research: (i) activity-timing mismatches determine ecological effects, (ii) duration and timing of timescape modification influence effects, and (iii) consequences of altered activity timing vary biogeographically due to broad-scale variation in factors compressing timescapes. The continued growth of sampling technologies promises to facilitate the study of the consequences of altered activity timing, with emerging applications for biodiversity conservation.     

Are Infaunal Predators Important in Structuring Marine Soft-Bottom Communities?

The role of infaunal predators in structuring marine soft-bottomcommunities was evaluated according to these predators': 1)effects on prey density based on manipulative field experiments,2) feeding rates, 3) effects on prey distribution, 4) effectson species diversity, and 5) interactions with their prey. Estimatesof feeding rates indicate that many predatory taxa have thepotential to reduce the size of prey populations and suggestthat nemerteans are likely to have a larger impact on infaunalabundances than polychaetes. Infaunal predators have been demonstratedto have a significant effect on infaunal densities and to affectthe spatial and temporal distribution of their prey. The effectsof these predators on species diversity apparently depend onthe predator and the diversity of the system. These conclusionsmay not be applicable to all soft-bottom habitats or all groupsof infaunal predators because they are based on studies of veryfew taxa conducted almost exclusively in intertidal, unvegetated,mud habitats. Additional studies are needed on the effects ofpredation by infauna on infaunal population dynamics and onthe mechanisms of interactions between predator and prey. Furtherinvestigation will probably reveal that different groups ofinfaunal predators play different roles in structuring soft-bottomcommunities.