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901.
Long‐Term Trends of Nutrients and Sediment from the Nontidal Chesapeake Watershed: An Assessment of Progress by River and Season
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Qian Zhang Damian C. Brady Walter R. Boynton William P. Ball 《Journal of the American Water Resources Association》2015,51(6):1534-1555
To assess historical loads of nitrogen (N), phosphorus (P), and suspended sediment (SS) from the nontidal Chesapeake Bay watershed (NTCBW), we analyzed decadal seasonal trends of flow‐normalized loads at the fall‐line of nine major rivers that account for >90% of NTCBW flow. Evaluations of loads by season revealed N, P, and SS load magnitudes have been highest in January‐March and lowest in July‐September, but the temporal trends have followed similar decadal‐scale patterns in all seasons, with notable exceptions. Generally, total N (TN) load has dropped since the late 1980s, but particulate nutrients and SS have risen since the mid‐1990s. The majority of these rises were from Susquehanna River and relate to diminished net trapping at the Conowingo Reservoir. Substantial rises in SS were also observed, however, in other rivers. Moreover, the summed rise in particulate P load from other rivers is of similar magnitude as from Susquehanna. Dissolved nutrient loads have dropped in the upland (Piedmont and above) rivers, but risen in two small rivers in the Coastal Plain affected by lagged groundwater input. In addition, analysis of fractional contributions revealed consistent N trends across the upland watersheds. Finally, total N:total P ratios have declined in most rivers, suggesting the potential for changes in nutrient limitation. Overall, this integrated study of historical data highlights the value of maintaining long‐term monitoring at multiple watershed locations. 相似文献
902.
Axel Hochkirch Michael J. Samways Justin Gerlach Monika Böhm Paul Williams Pedro Cardoso Neil Cumberlidge P. J. Stephenson Mary B. Seddon Viola Clausnitzer Paulo A. V. Borges Gregory M. Mueller Paul Pearce-Kelly Domitilla C. Raimondo Anja Danielczak Klaas-Douwe B. Dijkstra 《Conservation biology》2021,35(2):502-509
Measuring progress toward international biodiversity targets requires robust information on the conservation status of species, which the International Union for Conservation of Nature (IUCN) Red List of Threatened Species provides. However, data and capacity are lacking for most hyperdiverse groups, such as invertebrates, plants, and fungi, particularly in megadiverse or high-endemism regions. Conservation policies and biodiversity strategies aimed at halting biodiversity loss by 2020 need to be adapted to tackle these information shortfalls after 2020. We devised an 8-point strategy to close existing data gaps by reviving explorative field research on the distribution, abundance, and ecology of species; linking taxonomic research more closely with conservation; improving global biodiversity databases by making the submission of spatially explicit data mandatory for scientific publications; developing a global spatial database on threats to biodiversity to facilitate IUCN Red List assessments; automating preassessments by integrating distribution data and spatial threat data; building capacity in taxonomy, ecology, and biodiversity monitoring in countries with high species richness or endemism; creating species monitoring programs for lesser-known taxa; and developing sufficient funding mechanisms to reduce reliance on voluntary efforts. Implementing these strategies in the post-2020 biodiversity framework will help to overcome the lack of capacity and data regarding the conservation status of biodiversity. This will require a collaborative effort among scientists, policy makers, and conservation practitioners. 相似文献
903.
Salas-Zapata Walter Posada-Castaño Anny Mejía-Durango Diana 《The Environmentalist》2021,41(4):487-500
Environment Systems and Decisions - Natural resources are a type of good whose individual utility maximization is not desirable, as it could lead to their depletion. This problem, raised several... 相似文献
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In mammals, the chemical profiles of individuals are complex and variable mixtures, and animals perceive information based on variation in the overall quality of these mixtures. A variety of compounds potentially involved in chemical communication have been characterized in the urine of different felid species, but little is known about the information content of felid scent marks. In this study, we investigated whether chemical composition of Eurasian lynx Lynx lynx urine was related to sex, reproductive state, and individual identity. We further analysed if elemental sulphur in lynx urine could serve as a dietary cue or as an indicator for the freshness of a scent mark. We collected urine from captive and wild Eurasian lynx, and analysed volatile constituents of urine by means of solid phase microextraction and gas chromatography-mass spectrometry. Our results show that lynx scent profiles contain sex-specific information on reproductive state, as well as individual identity cues. Urine marks are, therefore, well-suited to fulfil a role in reproductive behaviour and social organisation of wild lynx populations. Relative sulphur content was unrelated to time since last feeding, but decreased with age of the urine sample. The influence of diet and body condition on scent profiles should be further investigated by means of experimental studies, and may shed more light on the messages encoded in carnivore scent-marks. 相似文献
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Molecular phylogeny and DNA barcoding of tropical eastern Pacific shallow-water gorgonian octocorals
The octocoral fauna inhabiting the shallow waters (<50 m) of the eastern Pacific has been the subject of renewed interest, and the taxonomy of the most important genera in the region has been reviewed and clarified. Many new species have been described, significantly increasing the known biological diversity of the region. Despite their importance as potential sister-groups of Caribbean octocorals, the phylogenetic relationships of eastern Pacific octocorals remain poorly studied. Here, using partial mitochondrial MutS and igr1-COI sequences, we provide a phylogenetic assessment of a broad sample of eastern Pacific shallow-water octocorals and investigate their phylogenetic relationships with Caribbean gorgonians. We corroborate the monophyly of Pacifigorgia, Leptogorgia and Eugorgia and provide evidence of a close relationship between Swiftia and Psammogorgia, currently placed in Plexauridae. In addition, the phylogenies obtained here provide insights into the historical biogeography and phylogenetic diversity of the eastern Pacific octocoral assemblages and on character evolution among this diverse faunal assemblage. Finally, we evaluate the classification power of DNA barcoding for identifying species of shallow-water eastern Pacific octocorals and assess the use of a nuclear intron (SRP54) to supplement traditional mitochondrial barcodes in this group of organisms. 相似文献
910.
Beatriz Willink Federico Bolaños Heike Pröhl 《Behavioral ecology and sociobiology》2014,68(2):249-261
The evolution of aposematism is linked to increased opportunities for conspicuous sexual displays since detection by potential predators is no longer disadvantageous. Therefore, phenotypic divergence in aposematic species leading to relatively cryptic forms is expected to constrain such opportunities, by restoring the trade-off between natural and sexual selection on the boldness of sexual displays. We asked if and how a derived phenotype of the poison-dart frog Oophaga granulifera that appears relatively cryptic to potential predators exhibits conspicuous sexual displays for potential mates. We used visual modeling of frog contrasts against their natural backgrounds to test if for conspecifics green frogs appear less conspicuous than red frogs as they do for birds. We conducted behavioral observations of focal red and green males to determine if green frogs adjust their display behavior to the availability of potential mates. Dorsal brightness is known to influence female preferences in at least one poison frog species. We found that, despite being less visible under some measures, green frogs may appear as bright as red frogs for conspecifics but not birds, when viewed on dark backgrounds. Additionally, green males called more intermittently than red males when advertising to distant females, but they exhibited a dramatic increase in calling activity in proximity of a female and were as active as red males in this context. Together, our results suggest that green frogs retain context-dependent conspicuousness to conspecifics despite the evolution of relative crypsis to potential predators. 相似文献