Does periphyton turn less palatable under grazing pressure?

Periphyton acts as an important primary producer in stream food webs with bottom-up grazing pressure and is also subject to effects of top-down grazing pressure. However, the underlying mechanisms of these interactions remain unclear. In this study we conducted a mesocosm experiment to explore the periphyton response to grazing pressure by the freshwater snail in relation to food quality indicated by polyunsaturated fatty acid (PUFA) biomarkers, including eicosapentaenoic acid (20:5n3) and the 22C fatty acid docosahexaenoic acid (22:6n3), which are essential for cell growth and reproduction and cannot be synthesized by most consumers of periphyton.

Global Relative Importance of Denitrification and Anammox in Microbial Nitrogen Loss Across Terrestrial and Aquatic Ecosystems.

Denitrification and anaerobic ammonium oxidation (anammox) are the major microbial processes responsible for global nitrogen (N) loss. Yet, the relative contributions of denitrification and anammox to N loss across contrasting terrestrial and aquatic ecosystems worldwide remain unclear, hampering capacities to predict the human alterations in the global N cycle. Here, a global synthesis including 3240 observations from 199 published isotope pairing studies is conducted and finds that denitrification governs microbial N loss globally (79.

Soil nitrogen biogeochemistry and hydrological characteristics shape the nitrate levels in a river.

The high levels of nitrate (NO) in the surface water have contributed to eutrophication and other eco-environmental damages worldwide. Although the excessive NO concentrations in rivers were often attributed to anthropogenic activities, some undisturbed or slightly disturbed rivers also had high NO levels. This study utilized multi-pronged approaches (i.

Regional sustainability outranked damming effects in affecting water quality in the lower reaches of the Jinsha River, China.

Besides cascade hydropower development, regional socio-economic activities also significantly affect water quality in the drainage region. However, it remains challenging to ascertain the implications of the damming effects and regional sustainability on water quality. This study examined the variations in water quality indicators, including chemical oxygen demand (COD), ammonia nitrogen (NH-N), and total phosphorus (TP), during the cascade hydropower development (both the construction and impoundment periods from 2006 to 2023) in the lower reaches of the Jinsha River (the upper reaches of the Yangtze River).

Extreme rainfall events eliminate the response of greenhouse gas fluxes to hydrological alterations and fertilization in a riparian ecosystem.

Riparian ecosystems are essential carbon dioxide (CO) sources, which considerably promotes climate warming. However, the other greenhouse gas fluxes (GHGs), such as methane (CH) and nitrous oxide (NO), in the riparian ecosystems have not been well studied, and it remains unclear whether and how these GHG fluxes respond to extreme weather, fertilization and hydrological alterations associated with reservoir management. Here, we assessed the impacts of hydrological alterations (i.

Coupled sulfur and nitrogen cycling at a catchment scale: insights from isotopic and molecular techniques.

The biogeochemical cycles of nitrogen (N) and sulfur (S) play important roles in sustaining the Earth's ecosystem. However, their potential coupling process and underlying mechanisms in the nature remain unclear. Through joint applications of river water's isotopic compositions, isotope-pairing experiments, and molecular techniques, this study revealed the coupled N-S cycling processes at a catchment scale from both geochemical and biological perspectives.

Nutritional Quality of Basal Resource in Stream Food Webs Increased with Light Reduction-Implications for Riparian Revegetation.

Biofilms are considered a basal resource with high nutritional quality in stream food webs, as periphytic algae are abundant of polyunsaturated fatty acids (PUFAs). PUFAs are essential for growth and reproduction of consumers who cannot or have very limited capacity to biosynthesize. Yet, how the nutritional quality based on PUFA of basal food sources changes with light intensity remains unclear.

Differential phenotypic plasticity of subalpine trees predicts trait integration under climate warming.

Understanding limiting factors of phenotypic plasticity is essential given its critical role in shaping biological adaptation and evolution in changing environments. It has been proposed that the pattern of phenotypic correlation could constrain trait plasticity. However, the interplay between phenotypic plasticity and integration has remained contentious.

Internal transformation and damming regulate the longitudinal variation of DOM bioavailability in a large river.

Understanding the spatial patterns of dissolved organic matter (DOM) and factors that influence them is crucial for maintaining river ecosystem functions and riverine health, considering the significant role of DOM in water quality and aquatic ecosystems. Nevertheless, there is limited knowledge regarding the spatial variation of DOM bioavailability and the factors driving them in large river systems. This study involved 39 sampling locations along the main stem of the Changjiang River, spanning its entire length (>5000 km) during a dry season.

Remittance from migrants reinforces forest recovery for China's reforestation policy.

Forests play a key role in the mitigation of global warming and provide many other vital ecosystem goods and services. However, as forest continues to vanish at an alarming rate from the surface of the planet, the world desperately needs knowledge on what contributes to forest preservation and restoration. Migration, a hallmark of globalization, is widely recognized as a main driver of forest recovery and poverty alleviation.

Lithology constrains the origination of autochthonous carbon in river ecosystems.

Dissolved inorganic carbon (DIC) provides a substrate for primary production in the lotic ecosystems, yet carbon's biogeochemical origination in the lotic food webs is still poorly constrained. Here, we assembled a global dataset of isotopic composition (i.e.

Meta-analysis shows the impacts of ecological restoration on greenhouse gas emissions.

International initiatives set ambitious targets for ecological restoration, which is considered a promising greenhouse gas mitigation strategy. Here, we conduct a meta-analysis to quantify the impacts of ecological restoration on greenhouse gas emissions using a dataset compiled from 253 articles. Our findings reveal that forest and grassland restoration increase CH uptake by 90.

Linking ecosystem multifunctionality to microbial community features in rivers along a latitudinal gradient.

Microorganisms regulate numerous ecosystem functions and show considerable differences along a latitudinal gradient. Although studies have revealed the latitudinal patterns of microbial community structure and single ecosystem function, the latitudinal patterns of ecosystem multifunctionality (EMF) and how microbial communities affect EMF along a latitudinal gradient remain unclear. Here, we collected channel sediments, riparian rhizosphere soils, and riparian bulk soils from 30 rivers across China and calculated EMF using 18 variables related to nitrogen cycling, nutrient pool, plant productivity, and water quality.

Multiomics analyses reveal the mechanisms of the responses of subalpine treeline trees to phenology and winter low-temperature stress.

Withstanding extreme cold stress is a prerequisite for alpine treeline trees to persist and survive. However, the underlying mechanism by which treeline trees sense phenological changes and survive hard winters has not been fully elucidated. Here, we investigated the physiology, transcriptome, and metabolome of the subalpine treeline species Larix chinensis to identify the molecular mechanism of phenological and cold resistance.

Eutrophication and loss of riparian shading influence food quality and trophic relation in stream food webs.

Eutrophication induced by excessive inputs of nutrient is one of the main stressors in aquatic ecosystems. Deforestation in riparian zones alter riparian shading, which together with eutrophication is expected to exert a complex control over stream food webs. We manipulated two levels of riparian shading (open canopy vs.

Climate warming could free cold-adapted trees from C-conservative allocation strategy of storage over growth.

Carbon allocation has been fundamental for long-lived trees to survive cold stress at their upper elevation range limit. Although carbon allocation between non-structural carbohydrate (NSC) storage and structural growth is well-documented, it still remains unclear how ongoing climate warming influences these processes, particularly whether these two processes will shift in parallel or respond divergently to warming. Using a combination of an in situ downward-transplant warming experiment and an ex situ chamber warming treatment, we investigated how subalpine fir trees at their upper elevation limit coordinated carbon allocation priority among different sinks (e.

Effects of environmental factors on the river water quality on the Tibetan Plateau: a case study of the Xoirong River, China.

Climate, topography, and landscape patterns affect river water quality through processes that influence non-point source pollution. However, little is known about the response of the water quality of rivers on China's Tibetan Plateau to these environmental factors. Based on the water quality parameters data of the Xoirong River on the Tibetan Plateau in western China, the redundancy analysis and variation partitioning analysis were adopted to determine the main influencing factors affecting river water quality and their spatial scale effects.

Unexpectedly high nitrate levels in a pristine forest river on the Southeastern Qinghai-Tibet Plateau.

River nitrate (NO) pollution is a global environmental issue. Recently, high NO levels in some pristine or minimally-disturbed rivers were reported, but their drivers remain unclear. This study integrated river isotopes (δO/δN-NO and δD/O-HO), N pairing experiments, and qPCR to reveal the processes driving the high NO levels in a nearly pristine forest river on the Qinghai-Tibet Plateau.

[Hydrochemical Evolution in the Yarlung Zangbo River Basin].

In order to explore the hydro-chemical evolution law of the Yarlung Zangbo River Basin from 1973 to 2020, the hydro-chemical characteristics and major ion sources were studied using a Piper diagram, Gibbs diagram, ion ratio, and correlation analysis, and the irrigation applicability of the Yarlung Zangbo River was evaluated using the sodium adsorption ratio (SAR), sodium percentage (Na%), and permeability index (PI). The results showed that the mean value of TDS was (208.30±58.

From Soil to River: Revealing the Mechanisms Underlying the High Riverine Nitrate Levels in a Forest Dominated Catchment.

Elevated riverine nitrate (NO) levels have led to increased eutrophication and other ecological implications. While high riverine NO levels were generally ascribed to anthropogenic activities, high NO levels in some pristine or minimally disturbed rivers were reported. The drivers of these unexpectedly high NO levels remain unclear.

Open riparian canopy and nutrient pollution interactively decrease trophic redundancy and allochthonous resource in streams.

Riparian deforestation, which leads to increase in light intensity and excessive nutrient loading in waterways, are two pervasive environmental stressors in the stream ecosystems. Both have been found to alter basal resource availability and consequently stream food webs. However, their interactive effects on trophic structure in stream food webs are unclear.

Coupling geochemical and microbial molecular techniques to reveal catchment-scale nitrate yield and fluvial export dynamics.

The disturbance of reactive nitrogen (N) on ecosystems and biogeochemical cycles is now one of the most severe environmental problems worldwide. Nitrate (NO) is usually a dominant reactive N species in river ecosystems. Excessive NO concentrations in rivers have led to eutrophication and consequent ecological and environmental damages.