Aim Little is known about factors affecting the elevational and longitudinal zonation of tropical Andean stream communities. We investigated epilithon, macroinvertebrate and fish assemblages along a 4100-m elevational-longitudinal gradient in an Andean headwater of the Amazon Basin. We interpret our results within the context of environmental factors, emphasizing temperature, as well as ecological theory relating shifts in metazoan functional feeding groups to shifts in basal resources along the fluvial continuum.Location Araz a-Inambari-Madre de Dios watershed, south-eastern Peru.Methods We sampled water physicochemistry, epilithon and macroinvertebrate diversity and abundance, and fish diversity at 18 main-stem and 14 tributary sites from high puna grasslands (4300 m a.s.l.) to Amazon Basin lowlands (200 m a.s.l.). ResultsWater physicochemical parameters and the taxonomic and ecological structure of invertebrate and fish assemblages displayed mostly nonlinear responses to elevation: water temperature and percentage of macroinvertebrate taxa identified as leaf shredders had U-shaped responses; dissolved oxygen and percentage of macroinvertebrate taxa identified as grazers had hump-shaped responses. Epilithon richness increased slightly with elevation whereas macroinvertebrate and fish richness decreased.Main conclusions Elevational gradients in physicochemical parameters are insufficient to explain abrupt and nonlinear shifts in community taxonomic and functional structure. Rather, trophic interactions, including predation and longitudinal turnover in basal food resources, seem to exert a stronger influence on the distributions of Andean aquatic organisms. A steep elevational decline in relative taxonomic diversity of leaf-shredding (versus algae-grazing) insects supports the hypothesis that temperature affects the functional composition of insect assemblages via its influence on microbial decomposition rates. This relationship, and the distributions of several insect and fish species across narrow elevational bands, suggests that Andean stream communities may be sensitive to global warming. Placer mining and road building impacts have already altered stream community structure, including the absence of many benthic species from low-elevation habitats.
1. Comparative research and generalisations in lotic ecology are challenged by the dynamic hydrology of fluvial systems. The aim of this study was to understand more fully how factors such as light, nutrients and flow can predict variation in autochthonous production and algal biomass. 2. We measured seasonal changes in percent bankfull discharge, inorganic nutrient concentrations, turbidity, instream primary production, respiration and algal biomass in the littoral zone of five floodplain rivers in one temperate and two tropical regions of the Western Hemisphere. The Brazos, Guadalupe and Neches rivers are in Texas, while the Tambopata River is in Peru and the Cinaruco River in Venezuela. Our study rivers represented a range of hydrological regimes, turbidity levels and nutrient concentrations. 3. Flooding patterns were more seasonal in the tropical rivers than in the (temperate) Texas rivers. Inorganic nutrient concentrations were higher in the temperate rivers, probably due to anthropogenic nutrient loading. Turbidity was higher following periods of high flow in the Brazos, Tambopata and Guadalupe rivers than in the Neches and Cinaruco rivers. Littoral zones in the sediment-laden Brazos and Tambopata rivers became heterotrophic during periods of high discharge, while littoral zones in the Guadalupe, Neches and Cinaruco rivers were consistently autotrophic. Regression tree analysis suggested that algal production and biomass in the water column responded more strongly to seasonal changes in nutrients and temperature than to turbidity, while benthic algae responded more strongly to turbidity. 4. Our findings suggest that during periods of high flow and turbidity in rivers containing fine sediments, autochthonous production is limited and terrestrial-based organic matter may assume greater importance in the aquatic food web.
The recent surge in incorporation of metallic and metal oxide nanomaterials into consumer products and their corresponding use in occupational settings have raised concerns over the potential for metals to induce size-specific adverse toxicological effects. Although nano-metals have been shown to induce greater lung injury and inflammation than their larger metal counterparts, their size-related effects on the immune system and allergic disease remain largely unknown. This knowledge gap is particularly concerning since metals are historically recognized as common inducers of allergic contact dermatitis, occupational asthma, and allergic adjuvancy. The investigation into the potential for adverse immune effects following exposure to metal nanomaterials is becoming an area of scientific interest since these characteristically lightweight materials are easily aerosolized and inhaled, and their small size may allow for penetration of the skin, which may promote unique size-specific immune effects with implications for allergic disease. Additionally, alterations in physicochemical properties of metals in the nano-scale greatly influence their interactions with components of biological systems, potentially leading to implications for inducing or exacerbating allergic disease. Although some research has been directed toward addressing these concerns, many aspects of metal nanomaterial-induced immune effects remain unclear. Overall, more scientific knowledge exists in regards to the potential for metal nanomaterials to exacerbate allergic disease than to their potential to induce allergic disease. Furthermore, effects of metal nanomaterial exposure on respiratory allergy have been more thoroughly-characterized than their potential influence on dermal allergy. Current knowledge regarding metal nanomaterials and their potential to induce/ exacerbate dermal and respiratory allergy are summarized in this review. In addition, an examination of several remaining knowledge gaps and considerations for future studies is provided.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.