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1.
Annika M. Felton Adam Felton Jeff T. Wood William J. Foley David Raubenheimer Ian R. Wallis David B. Lindenmayer 《International journal of primatology》2009,30(5):675-696
All free-living animals must make choices regarding which foods to eat, with the choices influencing their health and fitness.
An important goal in nutritional ecology is therefore to understand what governs animals’ diet selection. Despite large variation
in the availability of different food items, Peruvian spider monkeys (Ateles chamek) maintain a relatively stable daily protein intake, but allow total energy intake to vary as a function of the composition
of available food items. This is referred to as protein-dominated macronutrient balancing. Here we assess the influence of
this nutritional strategy on daily and seasonal nutritional intakes, estimate the nutritional value of different foods, and
interpret unusual food choices. We conducted continuous all-day observations of focal spider monkeys inhabiting a semideciduous
forest in Bolivia. We recorded feeding events, collected foods, and analyzed their nutrient content. By using the Geometric
Framework for nutrition, we show that individuals reached their daily end-point in nutrient space —balance between protein
and nonprotein energy intake— by consuming nutritionally balanced foods or by alternating between nutritionally complementary
foods. The macronutritionally balanced figs of Ficus boliviana were their primary staple food and therefore dominated their overall nutritional intake. Our results also demonstrate that
spider monkeys consumed a diverse array of ripe fruits to overcome periods of fig scarcity rather than vice versa; they could
obtain sufficient protein on a diet of pure fruit; and unripe figs constituted a nutritionally rewarding and reliable food
resource. We hope that the approaches taken and the conclusions reached in this study will catalyze further inquiries into
the nutritional ecology of frugivorous primates. 相似文献
2.
Males often have reduced immune function compared to females but the proximate mechanisms underlying this taxonomically widespread pattern are unclear. Because immune function is resource-dependent and sexes may have different nutritional requirements, we hypothesized that sexual dimorphism in immune function may arise from differential nutrient intake (acquisition hypothesis). To test this hypothesis, we examined patterns of phenoloxidase (PO) activity in relation to nutrient consumption in Queensland fruit flies (Q-flies). In the first experiment, flies were allowed to choose their preferred nutrient intake. Compared with males, female Q-flies had higher PO activity, consumed more calories, and preferred a higher protein:carbohydrate (P:C) diet, suggesting that differential acquisition could explain sex differences. In the second experiment, we restricted flies to one of 12 diets varying in protein and carbohydrate concentrations and mapped PO activity for each sex onto a nutritional landscape. Counter to our hypothesis, females had higher PO activity than males at any given level of nutrient intake. Both carbohydrate and protein intake affected PO activity in females but only protein affected PO activity in males. Our results indicate that sex differences in Q-fly immune function are not solely explained by sex differences in nutrient intake, although nutrition does contribute to the magnitude of these sex differences. 相似文献
3.
Donovan P. German 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(6):759-771
Few investigations have empirically analyzed fish gut function in the context of chemical reactor models. In this study, digestive
enzyme activities, levels of gastrointestinal fermentation products [short chain fatty acids (SCFA)], luminal nutrient concentrations,
and the mass of gut contents were measured along the digestive tract in herbivorous and carnivorous minnows to ascertain whether
their guts function as “plug-flow reactors” (PFRs). Four of the species, Campostoma anomalum, C. ornatum, C. oligolepis, and C. pauciradii, are members of a monophyletic herbivorous clade, whereas the fifth species, Nocomis micropogon, is a carnivore from an adjacent carnivorous clade. In the context of a PFR model, the activities of amylase, trypsin and
lipase, and the concentrations of glucose, protein, and lipid were predicted to decrease moving from the proximal to the distal
intestine. I found support for this as these enzyme activities and nutrient concentrations generally decreased moving distally
along the intestine of the four Campostoma species. Furthermore, gut content mass and the low SCFA concentrations did not change (increase or decrease) along the gut
of any species. Combined with a previous investigation suggesting that species of Campostoma have rapid gut throughput rates, the data presented here generally support Campostoma as having guts that function as PFRs. The carnivorous N. micropogon showed some differences in the measured parameters, which were interpreted in the contexts of intake and retention time to
suggest that PFR function breaks down in this carnivorous species. 相似文献
4.
Maressa Q. Takahashi Jessica M. Rothman David Raubenheimer Marina Cords 《American journal of primatology》2019,81(7)
Generalist primates eat many food types and shift their diet with changes in food availability. Variation in foods eaten may not, however, match variation in nutrient intake. We examined dietary variation in a generalist‐feeder, the blue monkey (Cercopithecus mitis), to see how dietary food intake related to variation in available food and nutrient intake. We used 371 all‐day focal follows from 24 adult females (three groups) in a wild rainforest population to quantify daily diet over 9 months. We measured food availability using vegetation surveys and phenology monitoring. We analyzed >700 food and fecal samples for macronutrient content. Subjects included 445 food items (species‐specific plant parts and insect morphotypes) in their diet. Variation in fruit consumption (percentage of diet and total kcal) tracked variation in availability, suggesting fruit was a preferred food type. Fruits also constituted the majority of the diet (by calories) and some fruit species were eaten more than expected based on relative availability. In contrast, few species of young leaves were eaten more than expected. Also, subjects ate fewer young leaves (based on calories consumed) when fruit or young leaves were more available, suggesting that young leaves served as fallback foods. Despite the broad range of foods in the diet, group differences in fiber digestibility, and variation that reflected food availability, subjects and groups converged on similar nutrient intakes (grand mean ± SD: 637.1 ± 104.7 kcal overall energy intake, 293.3 ± 46.9 kcal nonstructural carbohydrate, 147.8 ± 72.4 kcal lipid, 107.8 ± 12.9 kcal available protein, and 88.1 ± 17.5 kcal structural carbohydrate; N = 24 subjects). Thus, blue monkeys appear to be food composition generalists and nutrient intake specialists, using flexible feeding strategies to regulate nutrient intake. Findings highlight the importance of simultaneously examining dietary composition at both levels of foods and nutrients to understand primate feeding ecology. 相似文献
5.
ABSTRACT Fifth stadium tobacco hornworm caterpillars, Manduca sexta (L.), given artificial diet diluted to varying extents with either cellulose or water compensated for the food's reduced nutrient content by eating more of it. This compensation was, however, in most cases not sufficient to maintain normal growth rates. When the water content of the diet was reduced, the insects ate less than the usual fresh weight of food but maintained their intake of nutrients. Nevertheless, growth rate was impaired. The insects were better able to compensate for dilution of their food with water than with cellulose. The efficiency of conversion of ingested food (ECI) was decreased when the diet was adulterated with cellulose. At moderate dilution (50% nutrient) this was due mostly to decreased approximate digestibility (AD), but at greater dilution (25% and 10% nutrient content) the efficiency of conversion of digested food (ECD) was decreased. ECI was maintained when the water content of the diet was increased to give 50% nutrient concentration, but was decreased when water content was changed more radically (200%, 25% and 10% nutrient diets). This was due mostly to increased metabolic costs (decreased ECD) in all cases. The retention time of food in the gut was progressively decreased (i.e. speed of passage was increased) as nutrients were replaced by cellulose. By contrast, dilution of the diet with water resulted in only slight changes in retention time, except at extreme dilution (10% nutrient content) when retention time was reduced. Compensation of food intake was achieved by spending more (or less) time eating. Video analysis of feeding behaviour showed that there were significant changes in the length of feeding bouts and of interfeed gaps when caterpillars fed on diets of altered composition. For diets diluted with cellulose, changes in bout length and bout frequency contributed substantially to the increased time spent feeding on the adulterated food. For diets diluted with water, however, almost all of the compensatory change in behaviour was due to increased bout length, with bout frequency affected only slightly. This suggests that volumetric feedback contributes principally to the termination of feeding bouts in caterpillars, while nutrient flow may affect both the initiation and termination of feeding. 相似文献
6.
Mineral and trace element interactions were studied in a balance trial with rats. Calcium, copper, and zinc were supplied
to a rapeseed meal diet in a factorial design. Animals were fedad libitum, and absorption, excretion, and retention of the elements were evaluated either as fractions of total intake or in relation
to nitrogen retention to account for differences in food intake and lean body mass increment. The intrinsic content of minerals
and trace elements was sufficient to support growth at a rate that could be expected from the rapeseed protein quality. However,
when calcium was included in the diet, the intrinsic dietary level of zinc appeared to be limiting, despite the fact that
the zinc level was twice the recommended level. Additional zinc supply reversed growth impairment. This calcium-zinc interaction
is believed to be owing to the formation of phytate complexes. Calcium addition influenced the calcium, phosphorus, magnesium,
zinc, and iron—but not the copper—balances. The addition of calcium reduced the availability of the intrinsic zinc, whereas
no effect was seen in the zinc-fortified groups. The availability of intrinsic copper was in a similar way significantly impaired
by addition of dietary zinc, where-as copper-supplied groups were unaffected by zinc addition. Intrinsic iron availability
was also dependent upon zinc addition, although in a more ambigouus way. Thus, addition of extrinsic minerals to a diet high
in phytate can result in significant impairments of growth and mineral utilization. 相似文献
7.
Thompson SN Redak RA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(3):375-391
Effects of dietary nicotine and macronutrient ratio on M. sexta larvae were examined. Larvae were fed a carbohydrate-biased, protein-biased or diet having equal amounts of casein and sucrose,
with and without nicotine. Without nicotine, larvae displayed compensatory feeding on the low protein diet, but despite consuming
more, grew least on this diet. Nicotine at 0.5% had no effect on nutrient consumption. Nicotine at 1.0 and 2.0% reduced overall
consumption and thereby also reduced nicotine consumption. Larvae parasitized by C congregata displayed reduced nutrient intake and growth on all diets. Parasitized larvae responded to 1% nicotine similarly to unparasitized
larvae. At 0.5% nicotine, they displayed reduced consumption on all diets, possibly due to altered chemoreceptor sensitivity
to nicotine. When offered a choice of two diets having different macronutrient ratios, one with and the other without 0.1%
nicotine, all larvae preferred the diet lacking nicotine and failed to regulate nutrient intake such that the nutrient intake
target, a ratio of nutrients supporting optimal growth, was achieved. Parasitized larvae consumed less nicotine on a fresh
weight basis than unparasitized insects, suggesting that the feeding response of parasitized larvae to nicotine minimizes
the exposure of nicotine to developing parasites. 相似文献
8.
We explored modulation of retention time in cedar waxwings (Bombycilla cedrorum) by feeding them diets varying in hexose concentration. Our goals were to (1) test three predictions of a chemical reactor-based model of how guts might respond optimally to diet shifts; (2) determine whether modulation of retention time can occur quickly, thereby facilitating rapid changes in diet; (3) tease apart the relative influence of ingestion rate and nutrient concentration on retention time; and (4) examine the degree of axial mixing in the intestine and its relationship with retention time. The model's predictions were rejected: mean retention time did not decrease, ingestion rate did not increase, and glucose assimilation efficiency did not decrease with increased hexose concentration of the diet. Instead, birds displayed maximal intake rate at intermediate sugar concentration, and mouth to cloaca mean retention times increased with hexose concentration. Significant modulation of retention time occurred quickly, within 3 h of exposure to a different diet. Birds did equally well in terms of total energy assimilated on diets differing 3.3-fold in hexose concentration (from 500 mmol/L to 1660 mmol/L) but showed reduced intake when fed food with low hexose concentration (110 mmol/L). Far more variation in retention time was explained by direct effects of ingestion rate than by direct effects of hexose concentration. Finally, a gut dispersion index that measured degree of axial mixing was positively correlated with mean retention time, indicating that higher retention times are accompanied by increased axial mixing. We propose a modification of the assumptions of the original model. The resulting "osmotic constraint" model better captures the interaction between feeding rate and digestive function in fruit-eating birds. 相似文献
9.
Hannah V. Carey 《Ecography》1985,8(4):259-264
This study examined the basis of diet preference in a mammalian hibernator, the yellow-bellied marmot Marmota flaviventris , in the White Mountains of California. Preference indices calculated from dietary data and food plant availability in the habitat indicated that forb species were preferred over graminoids, particularly in the spring and early summer. Chemical analysis of food plant species suggested that marmots preferred forbs over graminoids because of their lower fiber (cellulose) content and higher concentrations of phosphorus, sodium and possibly protein. Inclusion of graminoids in the diets was probably due to their greater availability in the habitat coupled with the need to maximize the rate of nutrient intake during the short (4–5 month) active season. Seasonal changes in diet composition were noted which may reflect, in part, temporal changes in nutrient demands. 相似文献
10.
Afolabi PR Jahoor F Gibson NR Jackson AA 《American journal of physiology. Endocrinology and metabolism》2004,287(2):E327-E330
The plasma concentrations of albumin, HDL apolipoprotein A1 (apoA1), retinol-binding protein (RBP), transthyretin (TTR), haptoglobulin, and fibrinogen were measured, and a stable isotope infusion protocol was used to determine the fractional and absolute synthesis rates of RBP, TTR, and fibrinogen in 12 young adults on three occasions during a reduction of their habitual protein intake from 1.13 to 0.75 g x kg(-1) x day(-1) for 10 days. This study was performed to determine whether healthy adults could maintain the rates of synthesis of selected nutrient transport and positive acute-phase proteins when consuming a protein intake of 0.75 g x kg(-1) x day(-1). During the lower protein intake, the plasma concentration of all the proteins, other than HDL-apoA1, remained unchanged. HDL-apoA1 concentration was significantly reduced (P < 0.05) after 3 days of the lower protein intake, but not at 10 days. The rates of synthesis of RBP and TTR declined significantly (P < 0.05), whereas the rate of synthesis of fibrinogen remained unchanged. The results indicate that, when normal adults consume the recommended safe level of protein, 0.75 g x kg(-1) x day(-1), there is a slower rate of turnover of nutrient transport proteins than on their habitual diet. Hence, healthy individuals consuming this amount of protein may be less able to mount an adequate metabolic response to a stressful stimulus. 相似文献
11.
Because small ruminants (<15 kg) have a high ratio of metabolic rate to fermentation capacity, they are expected to select
and require low-fiber, nutrient-dense concentrate diets. However, recent studies suggest that small ruminants may not be as
limited in their digestive capacity as previously thought. In this study, we examined harvesting, rumination, digestion, and
passage of three diets (domestic figs Ficus carica, fresh alfalfa Medicago sativa, and Pacific willow leaves Salix lasiandra) ranging from 10 to 50% neutral detergent fiber content (NDF) in captive blue duikers (Cephalophus monticola, 4 kg). Harvesting and rumination rates were obtained by observing and videotaping animals on each diet, and digestibility
and intake were determined by conducting total collection digestion trials. We estimated mean retention time of liquid and
particulate digesta by administering Co-EDTA and forages labelled with YbNO3 in a pulse dose and monitoring fecal output over 4 days. Duikers harvested and ruminated the fig diet faster than the alfalfa
and willow diets. Likewise, they achieved higher dry matter, energy, NDF, and protein digestibility when eating figs, yet
achieved a higher daily digestible energy intake on the fresh willow and alfalfa than on the figs by eating proportionately
more of these forages. Duikers maintained a positive nitrogen balance on all diets, including figs, which contained only 6.3%
crude protein. Mean retention time of cell wall in the duikers’ digestive tract declined with increasing NDF and cellulose
content of the diet. Digestibility coefficients and mean retention times of these small ruminants were virtually equivalent
to those measured for ruminants two orders of magnitude larger, suggesting that they are well adapted for a mixed diet.
Received: 10 August 1999 / Accepted: 16 November 1999 相似文献
12.
Hannan MA Faraji B Tanguma J Longoria N Rodriguez RC 《Biological trace element research》2009,127(1):6-15
The dietary intake of zinc (Zn), iron (Fe), selenium (Se), and iodine (I) of 31 lactating Mexican–American women attending
the Hidalgo County WIC program in Rio Grande Valley (RGV), Texas was estimated from 24-h dietary recall interviews. Milk samples
were obtained from lactating mothers who had infants 3 months of age and younger. Milk samples were collected in two visits
to assess change in breast milk composition after 1–3 months postpartum: group A—after 30–45 days and group B—75–90 days.
Dietary intakes indicated that the study participants had significantly inadequate percent energy intakes than the DRI (Dietary
Recommended Intakes) percent recommended kilocalorie values but protein intakes were substantially higher than the percent
recommended values. The estimated percent Zn, Fe, Se, and I intakes were also significantly lower than the DRI percent recommended
values. The lactating mothers consumed significantly less Zn, Se, and I when compared to the Recommended Dietary Allowances
(RDA) even though Fe intake was higher than the RDA value. Breast milk concentration of Zn, Fe, and Se were in agreement within
the range of representative values for Constituents of Human Milk but I has significantly less concentration than the representative
value. There was no statistically significant correlation observed between dietary intake and milk concentration of Zn, Fe,
Se, and I. This study compares the estimated dietary intake of zinc, iron, selenium, and iodine to the concentration of these
trace elements in the maternal milk of lactating women of Mexican–American heritage who attend the Rio Grande Valley WIC clinic. 相似文献
13.
Ahmed S. Rahman Mieko Kimura Katsuhiko Yokoi Tanvir-E Naher Yoshinori Itokawa 《Biological trace element research》1996,53(1-3):57-64
Three groups of rats were fed two types of synthetic diets for 52 d. The—A group was allowed free access to a vitamin A-deficient
diet and showed classical signs of vitamin A deficiency. The brain was the only organ in our experiment where no significant
weight difference was present among the three groups. In the brain, calcium concentration was significantly higher in the—A
group when compared with the PF (Pair-fed; allowed restricted amount of control diet) and +A groups (allowed free access to
control diet). In the tibia, calcium and magnesium concentrations were significantly lower in the—A group when compared with
other two groups. Excessive accumulation of calcium in brain and apparently similar unbalance in bone, mineral concentration
were observed in central nervous system (CNS) degenerative diseases. Our results suggest that abnormal metabolism of calcium
and magnesium in some tissues and excessive accumulation of calcium in brain may be responsible for the development of neurological
disorders in vitamin A-deficient rats. 相似文献
14.
Trumble SJ Barboza PS Castellini MA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2003,173(6):501-509
We hypothesized that increased feeding frequency in captive harbor seals would increase nutrient loads and thus reduce retention time and the digestive efficiency of natural prey. We measured daily feed intake and excretion during 6 feeding trials and fed herring (49% lipid), pollock (22% lipid) or an equal mix of each diet over 24 months. Animals were accustomed to feeding at either high or low frequency. Body mass and intake did not vary with season. Although mean retention times were similar between diets and feeding frequencies, solute and particulate digesta markers separated at high feeding frequency. Consistent dry matter digestibility resulted in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were approximately 25% greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg–0.75 day–1. Our hypothesis of a trade-off between intake and digestion was not supported for protein but was supported for lipid. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting prey of lower energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake.Abbreviations DM
dry matter
- DEI
digestible energy intake
- DIT
diet-induced thermogenesis
- FF
feeding frequency
- MRT
mean retention time
Communicated by: G. Heldmaier 相似文献
15.
Wood-eating catfishes of the genus Panaque: gut microflora and cellulolytic enzyme activities 总被引:1,自引:0,他引:1
J. A. Nelson § D. A. Wubah M. E. Whitmer† E. A. Johnson ‡ D. J. Stewart ‡ 《Journal of fish biology》1999,54(5):1069-1082
Fresh gut contents of the wood-eating loricariid Panaque and a generalized loricariid Liposarcus sp. had enzymatic activity directed against both cellulose and hemicellulose. Aerobic cultures made from the guts of Panaque exhibited growth on a minimal salts medium containing only crystalline cellulose as a carbon source as well as on a variety of other substrates containing carbon polymers found in wood. Anaerobic cultures made from Panaque guts only grew with glucose as a carbon source. Cultures of whole gut contents grown on a yeast extract basal salts medium had significant cellulolytic activity. However, no culture of individual microbes had significant cellulolytic activity, suggesting that any cellulose breakdown which occurs in loricariid guts is by a consortium of micro-organisms. A variety of aerobes, microaerophiles and facultative anaerobes were found in the guts of Panaque ; several of these bacteria appear to be new species. 相似文献
16.
Sehnem NT de Bittencourt LR Camassola M Dillon AJ 《Applied microbiology and biotechnology》2006,72(1):163-167
The inducer effect of lactose on cellulase activity in Penicillium echinulatum 9A02S1 was studied. Submerged cultivation was performed using different concentrations of lactose and cellulose, in which the pH, mycelial mass, soluble proteins, filter paper activity (FPA), and activity of β-glucosidases were measured. The cultures containing lactose only presented low FPAs (0.1 FPU/ml). The cultures with associated cellulose and lactose and those containing cellulose only presented similar enzymatic activities (1.5 FPU/ml), suggesting the possibility of up to 75% reduction in the cellulose concentration. In relation to the β-glucosidases, increasing the lactose/cellulose ratio results in a proportional increase of enzymatic activity. In the cultures using both inducers, there is a longer duration of the acid phase in relation to treatments using only cellulose or lactose, indicating diauxia and catabolic repression. 相似文献
17.
Summary We examined digestibility of dry matter, nutrients, and fiber, and food intake, metabolic fecal losses, weight change, and gut size of pocket gophers (Thomomys bottae) in relation to diet quality in the laboratory. Pocket gophers were maintained for 15–20 days on one of seven diets which contained from 18% to 56% neutral detergent fiber (NDF). NDF content of the diet was an excellent predictor of diet quality. Digestibility of dry matter, NDF, and nitrogen all decreased with increasing NDF content of the diet. In general, pocket gophers compensated for low diet quality by increasing dry matter intake, but those given high quality forage before the lowest quality diet reduced their intake. Thus, the response of pocket gophers to low quality diets may depend on their body condition. Because increased food intake resulted in increased total metabolic fecal losses and metabolic fecal nitrogen losses, decreasing food intake on low-quality diets may be advantageous. A further response of pocket gophers to decreased food quality was an increase in size of cecum and large intestine, suggesting that fermentation of cell walls became increasingly important as diet quality decreased. 相似文献
18.
Dietary protein supplementation and its consequences for intake,digestion, and physical activity of a carnivorous marsupial,Sminthopsis crassicaudata
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Lihong Yuan Shawn Wilder David Raubenheimer Stephen J. Simpson Michelle Shaw Bronwyn M. McAllan 《Ecology and evolution》2018,8(7):3636-3647
Diet regulation behavior can mediate the consequences of imbalanced diets for animal well‐being, particularly for captive species that have little dietary choice. Dasyurids (carnivorous marsupials) are of conservation concern in Australia, and many species are in captive breeding programmes. However, their nutrient targets and dietary regulation behaviors are poorly understood, a limitation that may decrease the breeding success and well‐being of captive animals. We tested how dietary protein content influenced the intake and utilization of nutrients, physical activity, and body mass of fat‐tailed dunnarts Sminthopsis crassicaudata. Twelve adult dunnarts from six sibling pairs (one female and one male per pair) were provided ad libitum access to three diets in a repeated measures design: cat food, cat food supplemented with raw lean beef (1:1), and cat food supplemented with cooked lean beef (1:1). Food intake, activity level, and fecal output were measured daily. Dunnarts significantly decreased food intake, increased protein digestion, and physical activity, but body mass was unchanged when on the high‐protein diet compared to the normal cat food diet. These observations suggest a capacity of dunnarts to maintain constant body mass using a dynamic balance of feeding, digestion, and activity. We also found a significant effect of family, with differences between families as large as the difference between the diet treatments, suggesting a genetic component to diet selection. The nutrient regulation responses of dunnarts to high‐protein diets and the strong family effects provide important messages for the management of populations of small carnivores, including the aspects of dietary manipulation and conservation of genetic diversity. 相似文献
19.
Thomas Deforet Pierre Marmonier Dominique Rieffel Nadia Crini Patrick Giraudoux Daniel Gilbert 《Hydrobiologia》2009,623(1):235-250
The changes in both physical and chemical properties of interstitial water were investigated within a large gravel bar to
determine if the parafluvial zone was a hotspot for nutrient transformations in a lowland eutrophic river, the Doubs (Eastern
France). Interstitial water was sampled in 30 piezometers along five transects across the gravel bar, surface water was sampled
in main and chute channels. Five campaigns of sampling were performed among summer and winter. In both interstitial and surface
samples, water chemistry (electrical conductivity, pH, chloride, dissolved oxygen concentrations—DO) and nutrient concentrations
(nitrate—NO3
−, ammonium—NH4
+, soluble reactive phosphorus—SRP, dissolved organic carbon—DOC) were measured. Moreover, temperature, water level, sediment
grain size distribution and total bacterial abundance were assessed along a flowpath through a lateral gravel bar of the Doubs
River. Measurements of water table elevation in the bar, main and chute channels indicated that the parafluvial flowpath was
perpendicular to the main channel. Very low changes in chloride concentration and electrical conductivity showed minor groundwater
input along the flowpath. The parafluvial zone was 0.9 m thick under the mean piezometric level, hydraulic gradients along
the flowpath were 0.3%, and the discharge of interstitial water through the bar calculated at low flow was 40.6 m3 day−1. Most changes in interstitial nutrients occurred during the warm season, suggesting that biotic mechanisms occurred. Along
the flowpath, DO, DOC, and bacterial abundance declined, while phosphate increased. Temporal trends of nitrate were less clear,
exhibiting a slight increase during spring (organic matter biodegradation) and a decrease during summer (denitrification).
Using the parafluvial discharge and nutrient concentrations of water infiltrating into and seeping from the gravel bar, the
retention capacity of the bar was 171 gC day−1 for DOC and 48.3 gN day−1 for nitrate. Phosphate production ranged from 0.65 to 2.3 gP day−1. These values were low compared to the nutrient fluxes in the river Doubs, suggesting a minimal local impact of the parafluvial
zone in regulating of river pollution.
Handling editor: J. Padisak 相似文献
20.
Having the guts to compete: how intestinal plasticity explains costs of inducible defences 总被引:1,自引:0,他引:1
Predators commonly induce phenotypic changes that make prey better at surviving predation at the cost of reduced growth. While we have a good understanding of how trait changes affect predation risk, we lack a mechanistic understanding of why predator‐induced phenotypes differ in growth. Using two mesocosm experiments, we combined phenotypic plasticity theory with predictions from optimal digestion theory to demonstrate that intra‐ and interspecific competition induced relatively long guts while predators induced relatively short guts. The longer guts induced by competition appear to be an adaptive response that allows more efficient digestion and more rapid growth whereas the shorter guts induced by predators appear to result from a tradeoff of building larger tails in predator environments at the cost of smaller bodies. By combining these two bodies of theory, we now have a much better understanding of the mechanisms that cause the phenotypic trade‐offs that select for inducible defences. 相似文献