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1.
Due to the increasing number of biological invasions, more and more non-native species become components of already existing food chains and new interactions develop within communities. In our study, we checked whether (1) the predation preferences depended on sympatric or allopatric occurrence of predator and prey (a predator may choose the well-known prey or rather benefit from the naïvety of the novel one) and (2) fish preferences depended on prey susceptibility to fish predation (ability to hide, active predator avoidance) and/or on its palatability. We studied foraging efficiency of two species of Ponto-Caspian gobies (the round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris) and the European bullhead Cottus gobio on two species of amphipods—Ponto-Caspian Dikerogammarus villosus and non-invasive Gammarus fossarum, occurring in Central and Western Europe. The gammarids were offered to fish with or without shelters and as mobile individuals or immobilized to test the effect of their hiding ability, mobility and palatability on fish predation. Fish selectivity was exhibited only in trials with motile prey, where all tested predators preferred G. fossarum over D. villosus, showing that their selectivity was independent of prey origin. No selectivity was observed for immobilized amphipods. When shelters were present, the predation was lowest. Thus, predator preferences depended on prey behavioural traits (effective shelter utilization and/or activity reduction) rather than on their palatability. Effective predator preference of G. fossarum over D. villosus may be one of the reasons of the successful invasion of the latter to the European inland waters.  相似文献   

2.
The selective radius shift model was used to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation/dissolution within a pore depends on the local pore volume. The pore bundle concept was used to connect pore-scale changes to macroscopic soil hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and, consequently, in the effective porosity. In a time step of the numerical model, mineral reactions lead to a discontinuous pore-size distribution because only the water-filled pores are affected. The pore-size distribution is converted back to a soil moisture characteristic function to which a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with a mixed-form solution of Richards’ equation for aqueous phase flow, the model was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC’s comprehensive geochemical reactions. Example applications include kinetic halite dissolution and calcite precipitation as a consequence of cation exchange. These applications showed marked changes in the soil’s hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on water contents. The simulations also revealed the strong influence of the degree of saturation on the development of the saturated hydraulic conductivity through its quadratic dependency on the van Genuchten parameter α. Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even increase during precipitation due to changes in the pore-size distribution.  相似文献   

3.
Due to the production of toxins, cyanobacteria may adversely affect economically important fish such as Nile tilapia Oreochromis niloticus in tropical lakes. We studied the diet composition and factors affecting the diet of Nile tilapia in two tropical lakes where cyanotoxins were present. Particle-bound microcystins were present in all analysed water samples, ranging in concentration from 0.00012 to 1.11 and from 0.006 to 0.254 μg L−1 in Murchison Bay in Lake Victoria and Lake Mburo, respectively. Detritus and phytoplankton were the main dietary components of the Nile tilapia, with phytoplankton contributing to over 30% by volume of stomach contents. The cyanobacteria Microcystis spp., which are also the most likely source of microcystins in the lakes, accounted for more than 80% of ingested phytoplankton. Microcystis spp. were also the most abundant cyanobacteria in both lakes (>60%). We found no significant relationship between the contribution of phytoplankton in Nile tilapia diet and the concentration of microcystins in the water but we found a close association between water transparency and the contribution of insects to Nile tilapia diets in Murchison Bay. Our results further show that none of the other measured environmental variables was a good predictor of diet items in Nile tilapia. Adult Nile tilapia in our study lakes, rely heavily on filter feeding, particularly under conditions of low water transparency, trapping detritus and phytoplankton cells especially colonies. They can ingest more mobile prey like insects and insect larvae when the water transparency and visibility increases.  相似文献   

4.
王文种  黄对  刘九夫  刘宏伟  王欢 《湖泊科学》2020,32(5):1552-1563
湖泊变化是气候变化的指示器.为探索利用单一短时间尺度的卫星水位数据源估算长时间序列的湖泊水量变化的可行性，本文利用短时间尺度（2016—2018年） Sentinel-3A合成孔径雷达高度计（SRAL）作为唯一卫星水位数据源，以藏北高原内陆湖泊当惹雍错为例，结合基于Landsat光学遥感数据提取的1988—2018年的湖泊面积，综合分析2016—2018年间的非结冰期遥感湖泊面积与遥感湖泊水位变化，基于该时段范围的水位变化-面积变化关系和水量估算公式，估算1988—2018年湖泊水位水量变化与2001—2018年的年内变化，并结合GLDAS产品数据与雪线变化情况初步探讨湖泊变化的可能原因.结果表明：当惹雍错近30年湖泊面积扩张明显，湖泊水位、水量增加显著，相比1988年，2018年的湖泊面积、水位、水量分别增加21.1 km2、5.29 m、44.75亿m3.其中1988—1998年湖泊面积-水位-水量有所减少，2000—2018年间湖泊变化总体呈增加趋势.2001—2018年内湖泊面积、水位、水量变化呈现干湿季特征.1996—2014/2015年湖泊水量变化为38.3亿/35.5亿m3，水量变化趋势、变化量与以往对应时间段的研究结果具有较强的一致性.湖泊面积扩张主要发生在水下地形平缓的东南部和中西部区域.结合气候因素与雪线变化的分析表明，湖泊水量变化受降雨、气温影响复杂，长时间年际尺度上的湖泊水量增长与气温的一致性较降水量强，湖泊湿季受降水量与气温的影响都较大，其中2008—2018年的湿季降水量、气温与水量变化散点拟合的确定性系数R2分别为0.613、0.845.该研究表明Sentinel-3A合成孔径雷达数据在湖泊水量变化估算上的潜力，为利用单一且只具有短时段数据的卫星雷达数据估算长时间序列湖泊水量变化提供依据.  相似文献   

5.
Benthic diatoms are often used for assessing environmental conditions, such as water quality and habitat conditions in stream and river systems. Although laboratory experiments have shown that each diatom species have different levels of tolerance to different stressors, few studies have been conducted in laboratory settings that analyze the responses of the diatom assemblage to the effects of multiple simultaneous variables. The aim of this study was to evaluate some structural responses (such as species composition and diversity) of the diatom assemblage on a short time scale to the effects of the simultaneous increase in four variables that are directly linked to the environmental changes affecting the Pampean streams: turbidity, nutrients (phosphorous and nitrogen), water velocity and temperature. To this end we conducted a five-week laboratory experiment using artificial channels where we simulated two environmental conditions (LOW and HIGH) employing epipelic biofilm from a mesotrophic stream. The results obtained in the experiment show that the structure of the diatom assemblage in the epipelic biofilm is affected by the simultaneous modification of temperature, water velocity, nutrient concentration and turbidity. These modifications in the assemblage included moderate decreases in diversity, small decreases in the proportion of species sensitive to eutrophication and saprobity, moderate increases in the IDP (Pampean Diatom Index) values and moderate changes in the percentages of the stalked growth-forms. The relative abundance of species such as Luticola mutica, Navicula cryptocephala and Navicula lanceolata were negatively affected by both treatments; other species such as Planothidium lanceolatum, Caloneis bacillum, Encyonema minutum, Humidophila contenta, Luticola kotschyi, Nitzschia amphibia, Navicula veneta, Pinnularia subcapitata var. subcapitata were positively affected by the HIGH treatment; and Nitzschia fonticola was positively affected by both treatments. The results suggest that, in the very short term of the bioassay conducted, the diatom assemblage can modify its structure to respond in a sensitive manner to the abrupt changes in multiple physical–chemical variables.  相似文献   

6.
During the past decades, major anthropogenic environmental changes occurred in Lake Victoria, including increased predation pressure due to Nile perch introduction, and decreases in water transparency and dissolved oxygen concentrations due to eutrophication. This resulted in a collapse of the haplochromine cichlids in the sub-littoral waters of the Mwanza Gulf in 1986–1990, followed by a recovery of some species in the 1990s and 2000s, when Nile perch densities declined. We studied two data sets: (1) haplochromines from sand and mud bottoms in the pre-collapse period; (2) haplochromines from sub-littoral areas during the pre-collapse, collapse and recovery periods. Water over mud is murkier and poorer in oxygen than water over sand, and differences in haplochromine communities in these natural habitats during the pre-collapse period may predict the effects of anthropogenic eutrophication during the collapse and recovery periods. In the pre-collapse period, haplochromine densities over sand and mud did not differ, but species richness over sand was 1.6 times higher than over mud bottoms. Orange- and white-blotched colour morphs were most common at the shallowest sand station. More specifically, insectivores and mollusc-shellers had higher numbers of species over sand than over mud, whereas for mollusc-crushers no difference was found. Laboratory experiments revealed that mollusc shelling was more affected by decreased light intensities than mollusc crushing. During the pre-collapse period, spawning occurred year-round in shallow areas with hard substrates and relatively clear water. In deeper areas with mud bottoms, spawning mainly occurred during months in which water clarity was high. No effects of hypoxia on spawning periods were found. It follows that clearer water seems to support differentiation in feeding techniques as well as year-round spawning, and both may facilitate species coexistence. Water clarity is also known to be important for mate choice. These observations may explain why, since the decline of Nile perch, haplochromine densities have recovered, the numbers of hybrids increased and species diversity in the current eutrophic sub-littoral waters has remained 70 % lower than before the environmental changes.  相似文献   

7.
Asymmetrical interspecific competition among top predators can indirectly affect the predation risk for their prey by altering the abundance, diet, and habitat use of inferior competitors. However, the indirect effects of such biological interactions are poorly known because of the difficulties in measuring predation risk in nature. We addressed this issue by assessing the effect of asymmetrical competition among brook trout (Salvelinus fontinalis) and two superior non-piscivorous competitors, creek chub (Semotilus atromaculatus) and white sucker (Catostomus commersonii), on the predation risk of a brook trout prey, northern redbelly dace (Chrosomus eos). We determined the spatio-temporal patterns of relative predation risk of dace with tethering experiments in 11 lakes containing either only brook trout and dace (n = 5), or brook trout, dace, chub, and sucker (n = 6). The diel pattern of the relative predation risk and the overall relative predation risk of dace were not significantly different in lakes with or without brook trout competitors. However, we observed a significant shift in the relative predation risk from the lower pelagic to the upper pelagic and littoral zones in the presence of brook trout competitors. This study highlights the fact that the outcome of interactions can vary in space and that care should be used when extrapolating the results of small-scale experiments or coarse-scale estimates to the whole ecosystem.  相似文献   

8.
Diet and feeding intensity of the portunid crab Polybius henslowii were studied during the spring of 2004 along Galician and Cantabrian continental shelves (NW Iberian Peninsula) between 78 and 287 m. The area had been affected by the Prestige oil spill in November 2002, with different sectors at different levels of pollution: highest in between Miño River and Cape Finisterre (MF) and from there to Estaca de Bares Point (FE) and lowest from Estaca to Cape Peñas (EP). From 37272 specimens collected in 59 bottom hauls, 342 were analysed for stomach fullness and diet composition. Stomach fullness was lower in FE, but with no significant differences among sectors. Diet was a mixture of pelagic and benthic prey: cephalopods (Ilex coindetti), brachyurans (P. henslowii) and polychaetes (Glycera sp.). Other prey were beloniform eggs and fish remains. Two stress markers were also studied in some specimens: Acetylcholinesterase (a neurotoxicity marker) varied among sampled areas, while lipid peroxidation (an oxidative stress marker) did not. Changes in trophic variables, distribution and density were analysed in relation to depth, surface and bottom T, surface Chl a from satellite imagery and tar aggregate concentration in sediments. Along Galician and Cantabrian coasts prey availability, linked to productivity level, seems to be the main factor affecting P. henslowii diet and distribution. Interannual abundance variability seems to be controlled by large-scale climatic conditions (NAO index). This natural variability masks possible effects induced by the oil spill.  相似文献   

9.
Given their small size, isolation and unpredictability, temporary rockpools present high environmental stress and impoverished communities of species that have adapted to such stressful conditions. Special adaptations of the invertebrates living in these habitats include tolerance to desiccation and fast ontogenetic development in order to maintain stable populations and face high risk of extinction. Dozens of small rockpools (mostly with Ø < 1 m) can be found in east Spain on limestone substrate, where the only known Iberian populations of Heterocypris bosniacaPetkovski et al. (2000), an ostracod species with geographic parthenogenesis, have been recently found. In this survey, two of these rockpools have been monitored during the main hydroperiod between the fall of 2005 and summer 2006 to test the ability of H. bosniaca parthenogenetic populations to face unpredictable hydroperiod dynamics. Pools were visited weekly, and limnological data and ostracod samples were obtained from either water or substrate in dry periods. Ostracod individuals were counted and assigned to growth instars to monitor population changes. In the laboratory, experimental cultures allowed the estimation of survival dependence on the substrate desiccation rate. Throughout the hydrological cycle studied, several hatching periods were observed, usually preceded by desiccation, followed by substrate hydration and water dilution by rain. The demographic changes observed indicate that H. bosniaca populations are able to persist in intermittently inundated environments and produce several generations per annual hydrological cycle. In addition, adult individuals were able to survive in the wet mud of dry pools for longer than five weeks. The experimental data suggest a lower average survival time when exposed to desiccation processes, and that the velocity of substrate water loss is a determining factor for the survival rate of ostracods resisting dry events in temporary ponds. As shown by ostracods’ life histories in temporary aquatic environments undergoing unpredictable desiccation events, a combined strategy of adult tolerance to short periods of water scarcity and rapid hatching from resting egg banks can be advantageous for the monopolization of small-sized ephemeral habitats.  相似文献   

10.
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11.
While specialized species are linked to a particular resource, omnivorous species may switch between food items according to the availability and the quality of resources. Here we use larvae of the omnivorous caddisfly genus Hydropsyche (Trichoptera) to analyse changes in diet composition across an elevational gradient. Periphyton and Hydropsyche larvae were sampled from 22 populations at stream orders from 2 to 5 on the German part of the Bohemian Forest. Elevations of sampling sites ranged between 300 m and 900 m a.s.l.. Diet composition was estimated by the analyses of the gut content of larvae as well as by stable nitrogen isotopes (δ15N). The δ15N values of the periphyton decreased and the C/N ratio of periphyton increased with increasing environmental harshness (decreasing water pH, temperature and conductivity with increasing elevation) indicating a decrease of periphyton food quality. Across individuals, the proportion of animals in the gut of Hydropsyche larvae was positively related to the difference of δ15N values between larvae and periphyton. The proportion of animals within the gut and (baseline corrected) δ15N values of Hydropsyche populations increased with increasing environmental harshness. We suggest that the (i) low primary production caused by shading, low temperatures and low nutrient levels, (ii) the low nutrient quality of periphyton and (iii) the availability of animal prey due to the input of allochthonous resources in headwaters caused the shift in the diet of Hydropsyche larvae along the river continuum.  相似文献   

12.
Sensitivity study of the air–ice drag coefficient C Dai is presented with an ice–ocean coupled model for the Sea of Okhotsk. The C Dai?×?103 value is varied from 2 to 5 based on the direct measurements in the region. The maximum volume transport of the East Sakhalin Current and the mean sea ice velocity were intensified as C Dai increased. The sensitivity experiment with the ice–water drag coefficient C Diw showed that the East Sakhalin Current volume transport is hardly affected by C Diw but significantly intensified by C Dai. While the ice drift in the off-ice-edge direction was intensified by the increase in C Dai and the decrease in C Diw, the ice edge location was nearly unchanged. This was due to melting caused by the relatively warm water inflow from the North Pacific. That is, sea ice extent in the region is strongly influenced by melting caused by a large ice–ocean heat transfer. In the active melting regions, the ice–ocean heat transfer of more than 100 W/m2 occurred even in mid-winter. This is the same order as the cooling by air in winter, and a heat insulation capacity of sea ice is weakened in such regions.  相似文献   

13.
《Marine pollution bulletin》2009,58(6-12):295-301
The coastal waters of Bolinao, Pangasinan, Philippines experienced environmental changes over a 10-year period (1995–2005), the most significant effect of which was the major fish kill event in 2002 that coincided with the first reported Philippine bloom of a dinoflagellate Prorocentrum minimum. Days before the bloom, dissolved oxygen was <2.0 mg/l in the waters that were stratified. These conditions may be linked to the uncontrolled proliferation of fish pens and cages to more than double the allowable limit of 544 units for Bolinao waters. Mariculture activities release organic matter from unconsumed feed and fecal material that accumulate in the water and sediments. In over 10 years, water quality conditions have become eutrophic with ammonia increasing by 56%, nitrite by 35%, nitrate by 90%, and phosphate by 67%. The addition of more fish pens and cages placed additional stress to this poorly flushed, shallow area that affected water quality due to changes in the water residence time.  相似文献   

14.
The decomposition of plant litter is a fundamental ecological process in small forest streams. Litter decomposition is mostly controlled by litter characteristics and environmental conditions, with shredders playing a critical role. The aim of this study was to evaluate the effect of leaf species (Maprounea guianensis and Inga laurina, which have contrasting physical and chemical characteristics) and water nutrient enrichment (three levels) on leaf litter chemical characteristics and fungal biomass, and subsequent litter preference and consumption by Phylloicus sp. (a typical shredder in tropical streams). Maprounea guianensis leaves had lower lignin and nitrogen (N) concentrations, higher polyphenols concentration and lower lignin:N ratio than I. laurina leaves. Phosphorus concentrations were higher for both leaf species incubated at the highest water nutrient level. Fungal biomass was higher on M. guianensis than on I. laurina leaves, but it did not differ among nutrient levels. Relative consumption rates were higher when shredders fed on M. guianensis than on I. laurina leaves, due to the lower lignin:N ratio and higher fungal biomass of M. guianensis. Consumption rates on M. guianensis leaves were higher for those exposed to low water nutrient levels than for those exposed to moderate water nutrient levels. Feeding preferences by shredders were not affected by leaf species or nutrient level. The low carbon quality on I. laurina leaves makes it a less attractive substrate for microbial decomposers and a less palatable resource for shredders. Changes in litter input characteristics may be more important than short-term nutrient enrichment of stream water on shredder performance and ecosystem functioning.  相似文献   

15.
In 2002 to 2006, sediment profile imagery (SPI) was used to study the environmental impact of eutrophication-induced irregular and seasonal hypoxia on marine benthic habitats in six regions in the Skagerrak and Kattegat (West Sweden). The benthic habitat quality (BHQ) was assessed by parameterisation of biogenic structures observed by the SPI technique, and benthic quality status was related to the EU Water Framework Directive (EU-WFD). The temporal changes were analysed by a 5-factor nested ANOVA and significant temporal differences were recorded within three of the regions. Two of these were affected by hypoxia in the deeper parts and one was probably affected by hypoxia below the halocline. The environmental quality status according to the EU-WFD was bad to high in two regions, moderate to good in three regions, and good to high, i.e., acceptable according to the EU-WFD, in only one region. As BHQ is highly correlated to benthic faunal data, measures have to be taken to improve the coastal water quality in five of the six studied areas.  相似文献   

16.
Widespread persistent coseismic groundwater level changes induced by the M w 7.9 Wenchuan earthquake were recorded in 80 wells in Taiwan, located approximately 2,000?km from the epicenter. The timing and magnitude of these changes, ranging from ?40 to +23?cm, have been examined by statistical evaluation. The coseismic fall dominated in the plain area, but in the mountainous area most changes are coseismic rises. Both the coseismic rise and the coseismic fall were observed in wells of different depths at two monitoring stations. The processes of the coseismic changes can be shown by the high-frequency well water level data. Analysis of the 1?Hz water level data and the broadband seismogram revealed that a temporary water level change, ranging from 0.2 to 2.3?cm, occurred at the arrival of high-energy Love waves and Rayleigh waves. However, a water level change of 0.3–6.4?cm occurred in 7–20?min after the passing of high-energy surface waves. It is doubtful that such a change could be induced directly by ground shaking. The cross-formational flow due to fracturing or unclogging of sediment pores was possibly too slow to cause the coseismic change. Further studies are required to understand the mechanism of coseismic groundwater level changes induced by a distant earthquake.  相似文献   

17.
Fish may affect macrobenthic communities through trophic interactions and modification of habitat conditions. We compared the density, diversity and taxonomic composition of larval chironomids under low vs high fish impact, created by stocking semi-natural ponds with either young/small common carp Cyprinus carpio at low biomass densities or with high biomass densities of older/large common carp, supplemented by other cyprinids and predatory fish species.Over the study season, May–August, total chironomid abundance was considerably lower in ponds with high fish biomass than in low fish biomass ponds. In July–August larval densities declined significantly, irrespective of the fish status of the ponds. The composition of larval communities diverged between ponds with different fish status. Chironomus riparius and C. plumosus accounted for most of the observed dissimilarity. C. plumosus densities were not affected by the fish status of the pond, constituting on average >38 % of chironomid specimens in both types of ponds. C. riparius was abundant in ponds with low fish biomass (on average 30 %), but rare in ponds with high fish biomass (4 %). Other common taxa were Glyptotendipes pallens (15 % and 13 %, respectively) and Procladius sp. (14 % in ponds with low fish impact). Canonical correspondence analysis showed that fish biomass was more important in determining chironomid community composition than environmental variables indicative of pond eutrophication (total N, P, chlorophyll a and conductivity).Despite adverse effects on total abundance, chironomid diversity was higher under apparently stronger trophic pressure by fish. Fish may have relieved some chironomid species from invertebrate predation and competition with dominant Chironomus larvae. Other important drivers of chironomid assemblage and diversity patterns may include species-specific feeding modes and prey size selectivity of fish, the ability of chironomid larvae to attain size- and depth-refuge from small fish but not larger fish, and differential vulnerability of free-living and tube-dwelling larvae relative to ontogenetic niche shifts of fish.  相似文献   

18.
《Marine pollution bulletin》2011,62(7-12):367-374
The distribution of zooplanktonic prey of fish larvae was examined in three bays and two lagoonal stations in the Southwest lagoon of New Caledonia. Water column conditions were characterized by increasing chlorophyll a and particulate organic matter (POM) concentrations from the lagoon to the estuarine bay. The mean zooplankton settled volume and total density were significantly higher in the estuarine bay, reaching 35.1 mL m−3 and 3.5 × 105 individuals m−3, respectively. The total zooplankton density also progressively increased along the sampling period. The composition of assemblages differed between the lagoon and the bays, and was similar in the three bays. Wind speed, surface temperature, chlorophyll a and POM explained these variations, as revealed by a co-inertia analysis (COIA). The prey preferred by fish larvae, i.e. small crustaceans and small copepods, were more abundant in bays. Sheltered bays, most influenced by terrigenous inputs, are likely to provide the best feeding conditions.  相似文献   

19.
The effects of precipitation on the hygienic quality of water and blue mussels collected from five different localities in the urban areas in the Inner Oslofjord were investigated, with samples analysed for Escherichia coli, Salmonella spp., pathogenic Vibrio spp., Norovirus, Sapovirus, Cryptosporidium spp. and Giardia duodenalis. The sampling sites were located at varying distances from the outlet of combined sewer overflows (CSO)-impacted rivers/streams. In general, 1–3 log10 increases in fecal indicator bacteria and human pathogens were observed after heavy rainfalls. Blue mussels appeared to be a useful indicator of the impact of sewage at these sites, and generally a good correlation was identified between concentrations of E. coli and other human pathogens in the mussels. Provision of general advice to the public of avoiding areas near the outlets of CSO-impacted rivers after heavy rainfall may reduce the risk of gastroenteritis by bathers and others that may swallow water during recreational activities.  相似文献   

20.
Most streams draining to the Mediterranean basin are temporary. As a result of their hydrological regime, temporary streams are affected by drying and rewetting periods. Drying can alter in-stream nitrogen (N) availability and reduce N processing rates and subsequent retention after re-wetting. We sought to determine if hydrologic drying modifies reach-scale sediment chemical properties and constrains the response of N processing to rewetting. We compared different abiotic characteristics of sediments and nitrification and denitrification rates between a perennial and intermittent reach in the same stream over a wet period, when surface water flowed in both reaches, and a dry period, when the intermittent reach dried up. We analyzed N processing rates by incubating sediments with stream water, thereby simulating a rewetting when sediments from the intermittent reach were dry. We found that drying increased the sediment nitrate (NO3 ?) content. Conversely, drying did not reduce the recovery of N processing rates to pre-dry levels after simulated flooding conditions. Our results suggest that dry reaches may act as a potential NO3 ? source by releasing downstream NO3 ? pulses after stream flow recovery. Given the European Water Framework Directive requirements to assess stream ecological status, these N pulses following rewetting should be considered when designing management plans in temporary streams. Our study highlights the rapid response of in-stream N processing to rewetting period following a drought. This high resilience to process N should be seen as a vital ecosystem service provided by temporary streams despite annual dry periods.  相似文献   

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