Journal articles on the topic 'Nutrient additions'
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1
Anderson, Wendy B., and William G. Eickmeier. "Physiological and morphological responses to shade and nutrient additions of Claytonia virginica (Portulacaceae): implications for the "vernal dam" hypothesis." Canadian Journal of Botany 76, no. 8 (August 1, 1998): 1340–49. http://dx.doi.org/10.1139/b98-134.
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Because of their unique phenology and physiology, spring ephemeral herbs are believed to play an important role in intrasystem nutrient cycling in deciduous forest ecosystems. It was hypothesized that they function as a "vernal dam" by temporarily sequestering nutrients and preventing leaching from the system during a period of high nutrient availability. However, spring ephemerals require high-irradiance growing conditions. How do their physiological and morphological responses to ambient light and shade limit their ability to sequester excess nutrients? We performed field experiments using Claytonia virginica L. as a model to test several responses to shade and increasing levels of nutrient additions. We also examined the biomass responses and nutrient storage capacities of other spring ephemeral herbs. In C. virginica, shading reduced ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity, photosynthesis rate, specific leaf weight, leaf width/length (W/L), and biomass; nutrient additions increased W/L and biomass only under unshaded conditions. Other herbs responded similarly but reached maximum biomass at lower nutrient addition levels than C. virginica. Shading reduced and nutrient additions increased nitrogen and phosphorus concentrations in both C. virginica and other herbs. Shaded herbs generally reached nutrient saturation at lower nutrient addition levels than unshaded herbs. Overall, unshaded plants sequestered larger amounts of nutrients than shaded plants. This pattern is best explained by a reduction in biomass under shaded conditions. We concluded that C. virginica and other spring herbs, although important components in forest nutrient cycling in the early spring, are limited in their capacity to store excess nutrients, particularly when shaded.Key words: Claytonia virginica, nutrient cycling, spring ephemerals, vernal dam.
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Ebel, Jonathan D., Amy M. Marcarelli, and Andre E. Kohler. "Biofilm nutrient limitation, metabolism, and standing crop responses to experimental application of salmon carcass analog in Idaho streams." Canadian Journal of Fisheries and Aquatic Sciences 71, no. 12 (December 2014): 1796–804. http://dx.doi.org/10.1139/cjfas-2014-0266.
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Dramatic declines of Pacific salmon (Oncorhynchus spp.) populations have decreased delivery of marine-derived material to Pacific Northwest streams where juvenile salmon reside. Managers use artificial nutrient additions to increase juvenile salmon growth and survival and typically assume nutrient-driven increases in biofilm production are an important pathway by which nutrients become available to higher trophic levels. To evaluate how biofilms respond to additions of salmon carcass analog, a pasteurized, processed form of nutrient mitigation materials, we quantified biofilm nutrient limitation, benthic and whole-stream metabolism, and biofilm standing crops before and following experimental additions in tributaries of the Salmon River, Idaho, USA. Biofilm nutrient limitation did not change and standing crop did not increase in response to analog additions at two different levels (low, 30 g·m−2; or high, 150 g·m−2) within 1 month of addition. In contrast, whole-stream and benthic primary productivity and respiration increased in a high-analog treated segment, but did not increase in a low-analog treated segment. Together, our results suggest that metabolism may be a more appropriate tool for assessing the ecosystem effects of nutrient additions than biofilm standing crop or nutrient limitation, which are constrained by a variety of abiotic and biotic factors like hydrology and grazing.
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Wrenn, Brian A., Hao Zheng, Eugene S. Kohar, Kenneth Lee, and Albert D. Venosa. "Effect of Pulsed Additions of Nutrients on Oil Biodegradation in Continuous-Flow Beach Microcosms." International Oil Spill Conference Proceedings 2001, no. 1 (March 1, 2001): 339–44. http://dx.doi.org/10.7901/2169-3358-2001-1-339.
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ABSTRACT Bioremediation of oil-contaminated shorelines can be effected by providing sufficient quantities of certain rate-limiting nutrients, especially nitrogen and phosphorus. Although stoichiometry, based on the determination of optimal C:N:P ratios from batch oil-biodegradation experiments, traditionally has been the primary method for estimating required nutrient dosages, recent research suggests that nutrient uptake and microbial growth kinetics may be more important in determining the success of oil spill bioremediation. Because nutrient washout can be relatively rapid in intertidal environments, nutrient application strategies must consider the relative rates of nutrient washout and uptake by microorganisms. Because there may be significant differences between ammonium and nitrate with respect to both of these processes, a laboratory investigation of the performance of these two nitrogen sources was conducted in continuous-flow beach microcosm reactors. The behavior of these nutrients was compared under abiotic conditions to determine whether ammonium could be retained in oil-contaminated beaches longer than nitrate by ion exchange. Their ability to support oil biodegradation under continuous and intermittent feeding conditions also was compared. No differences between ammonium and nitrate could be detected based on either criterion, but faster oil biodegradation was observed under pulse-feeding conditions than when the nutrients were supplied continuously. The relatively poor performance of the continuously fed systems was attributed to nutrient limitation because the nutrient input rate was less than the nutrient demand rate.
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Zhuang, Liyan, Qun Liu, Ziyi Liang, Chengming You, Bo Tan, Li Zhang, Rui Yin, Kaijun Yang, Roland Bol, and Zhenfeng Xu. "Nitrogen Additions Retard Nutrient Release from Two Contrasting Foliar Litters in a Subtropical Forest, Southwest China." Forests 11, no. 4 (March 27, 2020): 377. http://dx.doi.org/10.3390/f11040377.
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Litter decomposition plays a critical role in regulating biogeochemical cycles in terrestrial ecosystems and is profoundly impacted by increasing atmospheric nitrogen (N) deposition. Here, a N manipulation experiment was conducted to explore the effects of N additions (0 kg N ha−1 yr−1, 20 kg N ha−1 yr−1 and 40 kg N ha−1 yr−1) on decay rates and nutrients release of two contrasting species, the evergreen and nutrient-poor Michelia wilsonii and the deciduous and nutrient-rich Camptotheca acuminata, using a litterbag approach at the western edge of the Sichuan Basin of China. The decay rate and the mineralization of N and phosphorus (P) was faster in nutrient-rich C. acuminata litter than in nutrient-poor M. wilsonii litter, regardless of N regimes. N additions tended to decrease the decay constant (k value) in M. wilsonii litter, but had no effect on C. acuminata litter. N additions had no significant effects on carbon (C) release of both litter types. N additions showed negative effects on N and P release of M. wilsonii litter, particularly in the late decomposition stage. Moreover, for C. acuminata litter, N additions did not affect N release, but retarded P release in the late stage. N additions did not affect the C:N ratio in both litter types. However, N additions—especially high-N addition treatments—tended to reduce C:P and N:P ratios in both species. The effect of N addition on N and P remaining was stronger in M. wilsonii litter than in C. acuminata litter. The results of this study indicate that N additions retarded the nutrients release of two foliar litters. Thus, rising N deposition might favor the retention of N and P via litter decomposition in this specific area experiencing significant N deposition.
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Benjamin, Joseph R., J. Ryan Bellmore, Emily Whitney, and Jason B. Dunham. "Can nutrient additions facilitate recovery of Pacific salmon?" Canadian Journal of Fisheries and Aquatic Sciences 77, no. 10 (October 2020): 1601–11. http://dx.doi.org/10.1139/cjfas-2019-0438.
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Multiple restoration actions have been implemented in response to declining salmon populations. Among these is the addition of salmon carcasses or artificial nutrients to mimic marine-derived nutrients historically provided by large spawning runs of salmon. A key assumption in this approach is that increased nutrients will catalyze salmon population growth. Although effects on aquatic ecosystems have been observed during treatments, it is unclear whether permanent population increases for salmon will occur. To test this assumption and address associated uncertainties, we linked a food web model with a salmon life cycle model to examine whether carcass additions in a river reach would improve conditions for salmon in the long term. Model results confirmed immediate increases in the biomass of periphyton, macroinvertebrates, and fish during carcass additions. In turn, juvenile salmon grew larger and experienced improved freshwater and smolt survival, which translated to a greater number of adults returning to spawn. However, once additions ceased, salmon abundance returned to pretreatment levels, which, based on our model, is owing to a combination of instream and out-of-basin factors. Overall, results of this work suggest that benefits during carcass and nutrient additions may not translate into persistent productivity of salmon unless additions are sustained indefinitely or other limiting factors are addressed.
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Timmer, V. R., and G. Armstrong. "Growth and nutrition of containerized Pinusresinosa at exponentially increasing nutrient additions." Canadian Journal of Forest Research 17, no. 7 (July 1, 1987): 644–47. http://dx.doi.org/10.1139/x87-105.
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Containerized red pine (Pinusresinosa Ait.) seedlings were reared on different fertility regimes that compared conventional applications of a recommended 39 mg N per seedling as a complete nutrient solution (175 mg N•L−1) with more frequent applications of an equal, one-half, or one-quarter amount of nutrients delivered at exponentially increasing solution concentrations over the same time period. Height growth, dry matter production, and root development at the end of the greenhouse rotation was significantly greater for seedlings receiving nutrients at exponentially rather than constantly increasing rates, although shoot growth among the three exponential treatments did not differ significantly. The increased yield was attributed to improved seedling nutrition as fertilizer addition rates better matched exponential growth development and nutrient consumption of the plants. The results indicate that superior seedlings can be grown successfully at low concentrations of nutrient solution, applying only one-quarter of the fertilizer dose conventionally used for container stock production.
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Perrin, Chris J., Max L. Bothwell, and Pat A. Slaney. "Experimental Enrichment of a Coastal Stream in British Columbia: Effects of Organic and Inorganic Additions on Autotrophic Periphyton Production." Canadian Journal of Fisheries and Aquatic Sciences 44, no. 6 (June 1, 1987): 1247–56. http://dx.doi.org/10.1139/f87-147.
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Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the Keogh River, British Columbia, following additions of grain and inorganic fertilizer as separate treatments during spring–summer 1981. Two different levels of N and P addition were used: one to attain ambient N and P concentrations of 200 and 15 μg∙L−1, respectively, and the other to attain 400 and 20 μg∙L−1, respectively. Grain (rolled barley) was added monthly at 280 g∙m−2. N and P additions increased chlorophyll a accrual rates by more than an order of magnitude. Diatoms dominated the periphyton community until midsummer. In July and most of August, the relative importance of chlorophytes increased and biomass levels declined markedly in spite of continued nutrient additions. Grain additions resulted in no detectable change in periphyton accrual, but alkaline phosphatase activity increased by 35% over control levels. These results suggest that additions of labile organic matter to nutrient-deficient coastal streams can increase autotrophic P deficiency. Based on responses of juvenile salmonids, additions of inorganic nutrients to increase autotrophic production can maximize trophic enhancement in nutrient-deficient streams.
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Christoforou, Anthea, Sheida Norsen, Jodi Bernstein, and Mary L’Abbe. "Examining the Prevalence, Nutritional Quality and Marketing of Foods with Voluntary Nutrient Additions in the Canadian Food Supply." Nutrients 13, no. 9 (September 5, 2021): 3115. http://dx.doi.org/10.3390/nu13093115.
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Foods with voluntary nutritional additions are a fast-growing sector of the global food industry. In Canada, while the addition of nutrients to foods has been regulated through fortification regulations, parallel policies which aim to encourage product innovation have also allowed for the voluntary addition of nutrients and other novel ingredients to ‘supplemented’ and ‘functional’ foods. Concerns have been raised that the consumption of these products may have negative repercussions on population health, such as high nutrient intakes inappropriate for certain population subgroups (e.g., children) and the shifting of dietary patterns to include more unhealthy foods. The aim of this study was to evaluate the prevalence, nutritional quality, and marketing characteristics of foods with added nutrients in the Canadian market. We found many nutritionally-enhanced foods contained high levels of nutrients beyond recommended intakes, despite these nutrients having no evidence of inadequacy in the Canadian population. Additionally, a large proportion of foods with added nutrients had poor nutrient profiles (were deemed ‘less healthy’ than their non-enhanced counterparts) and carried heavy marketing on their labels, regardless of their nutritional quality. Taken together these findings raise concerns about foods with voluntary nutrient additions and suggest the need to further investigate consumer attitudes and decision-making towards these foods.
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Anderson, Wendy B., and William G. Eickmeier. "Nutrient resorption in Claytonia virginica L.: implications for deciduous forest nutrient cycling." Canadian Journal of Botany 78, no. 6 (June 1, 2000): 832–39. http://dx.doi.org/10.1139/b00-056.
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According to the vernal dam hypothesis, spring ephemeral herbs temporarily sequester large nutrient pools in deciduous forests prior to canopy closure and return the nutrients to the soil following senescence of aboveground tissues. However, many species resorb nutrients from their leaves back to belowground tissues during senescence, and the degree of resorption is often associated with soil nutrient availability. Species that store large proportions of their absorbed nutrients between years are not participating in the temporary sequestering and rapid recycling of nutrients implied by the vernal dam. We investigated the extent to which Claytonia virginica L. sequestered and returned nutrients to the soil in response to nitrogen (N) and phosphorus (P) availability. We tested the effect of nutrient availability on nutrient use efficiency, resorption efficiency, and resorption proficiency (% nutrient in senescent leaves) of Claytonia. Nutrient additions significantly decreased N but not P use efficiency of Claytonia, particularly as the growing season progressed. Nutrient additions also significantly reduced N resorption efficiency from 80 to 47% and decreased P resorption efficiency from 86 to 56%. N and P resorption proficiencies were also significantly lower in senesced leaves of fertilized plants: N concentrations were 2.33% when unfertilized and 4.13% when fertilized, while P concentrations were 0.43% when unfertilized versus 0.57% when fertilized. When unfertilized, Claytonia was more efficient at resorption compared with other spring herbs, but similar to other species when fertilized. However, Claytonia was much less proficient in resorbing nutrients than other reported plants, because senescent tissues maintained substantially higher concentrations of N and P, particularly when fertilized. In conclusion, Claytonia, an important spring ephemeral species, exhibits physiological responses that emphasize its role in the vernal dam by its temporary sequestration and substantial, rapid return of nutrients in deciduous forests. Adding nutrients to the site increases the total mass and the relative proportion of nutrients that Claytonia returns to the soil rather than sequestering between seasons, which ultimately increases nutrient recycling rates within the entire system.Key words: Claytonia virginica, nutrient response, resorption efficiency, nutrient cycling, spring ephemerals, vernal dam.
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Morris, Liz, Gregory Jenkins, David Hatton, and Timothy Smith. "Effects of nutrient additions on intertidal seagrass (Zostera muelleri) habitat in Western Port, Victoria, Australia." Marine and Freshwater Research 58, no. 7 (2007): 666. http://dx.doi.org/10.1071/mf06095.
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Loss of seagrass habitat in many parts of the world has been attributed to increases in nutrient loading to nearshore areas. The role of excess epiphyte, macroalgal or phytoplankton growth in shading of seagrass leaves and negatively affecting seagrass health is generally agreed to be a prevalent mechanism in seagrass decline worldwide. In the present study nutrient addition experiments were undertaken at three sites in Western Port, Victoria. Nutrients were added to the water column using the controlled release fertiliser Osmocote™ in late summer 2005. The experiments ran for one month at two of the sites (Blind Bight and Hastings) and at the third site (Crib Point) the experiment ran for three months. Control and nutrient addition plots were monitored for concentrations of inorganic nutrients, number of seagrass leaves, seagrass, epiphyte and loose algal biomass and invertebrate faunal assemblages. Nutrient additions had increased ash free dry weight of seagrass leaves and loose algae at two of the three sites studied. There was also an increase in gammarid amphipod densities at the Crib Point site. We consider that Western Port seagrass habitat is sensitive to increased loads of nutrients within the water column with the Blind Bight region most at risk.
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Stewart Jr., C. Neal, and Erik T. Nilsen. "Drosera rotundifolia growth and nutrition in a natural population with special reference to the significance of insectivory." Canadian Journal of Botany 70, no. 7 (July 1, 1992): 1409–16. http://dx.doi.org/10.1139/b92-177.
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The impact of nutrient addition on growth and nutrient accumulation in Drosera rotundifolia was studied in a field population. Experiments were performed by exclosing insects and (or) adding phosphorus and (or) nitrogen to soil. Drosera rotundifolia did not significantly benefit from insect capture nutritionally or energetically in native or nutritionally enhanced soils. Added nutrients to the soil or supplemental foliar insect feeding decreased phosphorus retention in hibernacula by 50%. Nutrient additions reduced D. rotundifolia vegetative growth in both N and P addition treatments. In addition, allocation to reproduction (inflorescences) decreased by 98% when N was added to the soil. Phosphorus retention in hibernacula was especially high in plots in which no nutrients were added via the soil or by insect applications. Although not statistically significant, flower stalk density and floral biomass were greater where insects were available to plants. The data from this study indicate that insectivory has little impact on growth of field grown D. rotundifolia. This species is adapted to low nutrient availability and nutrient enhancement reduces growth. Indices of nutrient retention suggest that phosphorus is conserved more than nitrogen and therefore may be an important limiting nutrient. Key words: insectivory, nitrogen, phosphorus, sundew.
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Leff, Jonathan W., Stuart E. Jones, Suzanne M. Prober, Albert Barberán, Elizabeth T. Borer, Jennifer L. Firn, W. Stanley Harpole, et al. "Consistent responses of soil microbial communities to elevated nutrient inputs in grasslands across the globe." Proceedings of the National Academy of Sciences 112, no. 35 (August 17, 2015): 10967–72. http://dx.doi.org/10.1073/pnas.1508382112.
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Soil microorganisms are critical to ecosystem functioning and the maintenance of soil fertility. However, despite global increases in the inputs of nitrogen (N) and phosphorus (P) to ecosystems due to human activities, we lack a predictive understanding of how microbial communities respond to elevated nutrient inputs across environmental gradients. Here we used high-throughput sequencing of marker genes to elucidate the responses of soil fungal, archaeal, and bacterial communities using an N and P addition experiment replicated at 25 globally distributed grassland sites. We also sequenced metagenomes from a subset of the sites to determine how the functional attributes of bacterial communities change in response to elevated nutrients. Despite strong compositional differences across sites, microbial communities shifted in a consistent manner with N or P additions, and the magnitude of these shifts was related to the magnitude of plant community responses to nutrient inputs. Mycorrhizal fungi and methanogenic archaea decreased in relative abundance with nutrient additions, as did the relative abundances of oligotrophic bacterial taxa. The metagenomic data provided additional evidence for this shift in bacterial life history strategies because nutrient additions decreased the average genome sizes of the bacterial community members and elicited changes in the relative abundances of representative functional genes. Our results suggest that elevated N and P inputs lead to predictable shifts in the taxonomic and functional traits of soil microbial communities, including increases in the relative abundances of faster-growing, copiotrophic bacterial taxa, with these shifts likely to impact belowground ecosystems worldwide.
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Smithwick, Erica A. H., Douglas C. Baldwin, and Kusum J. Naithani. "Grassland productivity in response to nutrient additions and herbivory is scale-dependent." PeerJ 4 (December 1, 2016): e2745. http://dx.doi.org/10.7717/peerj.2745.
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Vegetation response to nutrient addition can vary across space, yet studies that explicitly incorporate spatial pattern into experimental approaches are rare. To explore whether there are unique spatial scales (grains) at which grass response to nutrients and herbivory is best expressed, we imposed a large (∼3.75 ha) experiment in a South African coastal grassland ecosystem. In two of six 60 × 60 m grassland plots, we imposed a scaled sampling design in which fertilizer was added in replicated sub-plots (1 × 1 m, 2 × 2 m, and 4 × 4 m). The remaining plots either received no additions or were fertilized evenly across the entire area. Three of the six plots were fenced to exclude herbivory. We calculated empirical semivariograms for all plots one year following nutrient additions to determine whether the scale of grass response (biomass and nutrient concentrations) corresponded to the scale of the sub-plot additions and compared these results to reference plots (unfertilized or unscaled) and to plots with and without herbivory. We compared empirical semivariogram parameters to parameters from semivariograms derived from a set of simulated landscapes (neutral models). Empirical semivariograms showed spatial structure in plots that received multi-scaled nutrient additions, particularly at the 2 × 2 m grain. The level of biomass response was predicted by foliar P concentration and, to a lesser extent, N, with the treatment effect of herbivory having a minimal influence. Neutral models confirmed the length scale of the biomass response and indicated few differences due to herbivory. Overall, we conclude that interpretation of nutrient limitation in grasslands is dependent on the grain used to measure grass response and that herbivory had a secondary effect.
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Nataraja, T. H., Raja Naika, Shashidhar K. Shankarappa, Krishna Viswanatha Reddy, Shaimaa A. M. Abdelmohsen, Fatemah F. Al-Harbi, Tarek K. Zin El-Abedin, Hosam O. Elansary, and Ashraf M. M. Abdelbacki. "Productivity of Paddies as Influenced by Varied Rates of Recommended Nutrients in Conjunction with Biofertilizers in Local Landraces." Agronomy 11, no. 6 (June 7, 2021): 1165. http://dx.doi.org/10.3390/agronomy11061165.
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This research work explores the productive performance of local paddy landraces under different fertility levels as well as the role of microbial inoculants in improving the yields of paddy landraces and reducing nutrient additions by increasing nutrient use efficiency under changing climatic scenarios in coastal areas. The landrace Padmarekha recorded taller plants, more tillers per hill, higher total dry matter accumulation other than grain and straw yields besides better uptake of N, P2O5, K2O, S and Zn. Further, nutrient management with the application of 100% of the recommended doses of fertilizers combined with biofertilizers including Azospirillum + Bacillus megatherium var. Phosphoticum + Frateuria quaratia + Thiobacillus thiooxidans + Vesicular Arbuscular Mycorrhiza recorded higher growth and yield traits in addition to improving the uptake of nutrients and partial factor productivity. Thus, it can be concluded that the application of 100% of the recommended dose of fertilizer, inoculated with biofertilizers, would be helpful in increasing the efficiency of applied nutrients in addition to improving yield and nutrient use efficiency.
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Horrocks, JL, GR Stewart, and WC Dennison. "Tissue nutrient content of Gracilaria spp. (Rhodophyta) and water quality along an estuarine gradient." Marine and Freshwater Research 46, no. 6 (1995): 975. http://dx.doi.org/10.1071/mf9950975.
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Tissue nutrient content of Gracilaria spp. (Rhodophyta) was tested as a bioindicator of water column nutrient availability in the Logan River and southern Moreton Bay, south-eastem Queensland. Macroalgae were incubated for one to two weeks within flow-through incubation chambers suspended in the water column. Tissue nutrient content of Gracilaria spp, and water column nutrients were measured at five sites over a five-month period. Tissue nitrogen content (%N) was correlated with dissolved inorganic nitrogen (DIN) at a site 15 km upstream from the Logan River mouth (r² = 0.81), at the Logan River mouth (r² = 0.50), and at a Moreton Bay site 8 km from the Logan River mouth (r² = 0.71). Time-course analyses of water column nutrients and plant tissue content showed more significant correlations with nitrogen (N) than with phosphorus (P). Plant tissue nitrogen-to-phosphorus (N:P) molar ratios ranged between 19 and 23 whereas water column N:P ratios were between 2 and 6, suggesting low nitrogen availability relative to plant requirements and possible N limitation. In the laboratory, Gracilaria verrucosa was subjected to treatments of N, P or N + P nutrient additions. Deepening of the thallus colouration was observed after additions of N. Chlorophyll and phycoerythrin concentrations increased in treatments with N addition; however, owing to wide variability between phycoerythrin replicates, only chlorophyll increases were significant. The amino acid citrulline also increased with the addition of N and accounted for up to 16% of the total tissue N. Macroalgae may be more useful than traditional water quality sampling for integrating biologically available pulses of nutrients, especially for a limiting nutrient such as N in coastal marine ecosystems.
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Lafrancois, Brenda Moraska, Koren R. Nydick, Brett M. Johnson, and Jill S. Baron. "Cumulative effects of nutrients and pH on the plankton of two mountain lakes." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 7 (July 1, 2004): 1153–65. http://dx.doi.org/10.1139/f04-053.
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We conducted enclosure experiments to examine the cumulative effects of nutrient enrichment and acidification on the plankton of two mountain lakes with differing nutrient conditions. The low-nitrate lake responded to N, N plus acid, and N plus acid plus P additions, showing four- to seven-fold increases in chlorophyll a, increased photosynthetic rate, compositional shifts toward large chlorophytes, and decreased zooplankton biomass. The high-nitrate lake responded minimally to either N or P alone but responded strongly to combined additions of N plus acid plus P, showing eightfold increases in chlorophyll a, increased cell density and photosynthetic rates, and compositional shifts toward chlorophytes and the dinoflagellate Gymnodinium. In both study lakes, changes in chlorophyll a were linked to addition of limiting nutrients regardless of pH, whereas shifts in phytoplankton species composition were apparently affected by both nutrient conditions and acidity. The most striking changes in species composition and biomass occurred in combined N plus acid plus P treatments, indicating that continued nutrient enrichment may interact with acidification to produce marked changes in the plankton of mountain lakes.
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Chénier, Martin R., Danielle Beaumier, Réal Roy, Brian T. Driscoll, John R. Lawrence, and Charles W. Greer. "Impact of Seasonal Variations and Nutrient Inputs on Nitrogen Cycling and Degradation of Hexadecane by Replicated River Biofilms." Applied and Environmental Microbiology 69, no. 9 (September 2003): 5170–77. http://dx.doi.org/10.1128/aem.69.9.5170-5177.2003.
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ABSTRACT Biofilm communities cultivated in rotating annular bioreactors using water from the South Saskatchewan River were assessed for the effects of seasonal variations and nutrient (C, N, and P) additions. Confocal laser microscopy revealed that while control biofilms were consistently dominated by bacterial biomass, the addition of nutrients shifted biofilms of summer and fall water samples to phototrophic-dominated communities. In nutrient-amended biofilms, similar patterns of nitrification, denitrification, and hexadecane mineralization rates were observed for winter and spring biofilms; fall biofilms had the highest rates of nitrification and hexadecane mineralization, and summer biofilms had the highest rates of denitrification. Very low rates of all measured activities were detected in control biofilms (without nutrient addition) regardless of season. Nutrient addition caused large increases in hexadecane mineralization and denitrification rates but only modest increases, if any, in nitrification rates, depending upon the season. Generally, both alkB and nirK were more readily PCR amplified from nutrient-amended biofilms. Both genes were amplified from all samples except for nirK from the fall control biofilm. It appears that bacterial production in the South Saskatchewan River water is limited by the availability of nutrients and that biofilm activities and composition vary with nutrient availability and time of year.
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Bungard, Ralph A., Shirley A. Zipperlen, Malcolm C. Press, and Julie D. Scholes. "The influence of nutrients on growth and photosynthesis of seedlings of two rainforest dipterocarp species." Functional Plant Biology 29, no. 4 (2002): 505. http://dx.doi.org/10.1071/pp01137.
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This study aims to determine the influence of nutrient additions in the form of nitrogen (N), phosphorus (P) and potassium (K) on the photosynthetic physiology, morphology and growth of Dryobalanops lanceolata Burck and Shorea johorensis Foxw., two co-existing dipterocarp species in the understorey of secondary forest. Analysis of the light environment revealed that the total daily irradiance in the understorey was 4.57 ± 0.70 mol photons m–2 d–1, approximately 20% higher than that which could be expected to occur in the primary forest understorey. Around 50% of total irradiance occurred at fluxes over 400 μmol photons m–2 s–1, and this was received over 7% of the daylight period. Both D. lanceolata and S. johorensis grew over the 16-month study, but only S. johorensis increased growth in response to nutrient additions. Neither species altered biomass partitioning in response to additional nutrients. Both species also showed increased rates of photosynthetic induction (T0.5Asat) in response to nutrient additions, but only S. johorensis showed an increase in light-saturated rates of photosynthetic capacity (Asat), and the chlorophyll content of leaves. We argue that additional nutrients increased the capacity of S. johorensis to utilise the sporadic burst of high irradiance in sunflecks. Analysis of the nutrient composition of leaves from age cohorts up to > 16 months showed that additional nutrients increased the P and K concentration in D. lanceolata leaves, and the P and N content of S. johorensis leaves. This suggests that neither P nor K were limiting the growth of D. lanceolata in this secondary forest environment, but that P and/or N may limit growth of S. johorensis. Our data highlights differences in the ecology of two co-existing dipterocarp species. We argue that D. lanceolata shows characteristics consistent with a low resource-demanding species that may have a competitive advantage over S. johorensis in low resource environments, while S. johorensis shows traits better suited to higher resource availability. Thus, there are distinct species-specific differences in the ability to respond to nutrients that depend on the irradiance environment, and which may have a role in niche partitioning among the dipterocarps.
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Paul, A. J., D. W. Schindler, A. K. Hardie, and P. R. Leavitt. "Direct and indirect effects of predation by a calanoid copepod (subgenus: Hesperodiaptomus) and of nytrients in a fishless alpine lake." Canadian Journal of Fisheries and Aquatic Sciences 52, no. 12 (December 1, 1995): 2628–38. http://dx.doi.org/10.1139/f95-852.
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The calanoid copepod Diaptomus (subgenus: Hesperodiaptomus) arcticus is a keystone predator in fishless alpine lakes of the Canadian Rockies. We quantified the effects of predation by D. arcticus on other copepods, rotifers, and algae in large mesocosm experiments (2250 L) using two levels of predator (present and absent) and two levels of nutrient addition (ambient and 4×). Standing stocks of algal taxa were assessed by high performance liquid chromatography of phytoplankton pigments. Diaptomus arcticus suppressed the biomass of rotifers and cyclopoid nauplii at both nutrient levels. The indirect effect of D. arcticus on algal biomass was minimal under ambient nutrient conditions, possibly owing to high rates of nutrient recycling by grazers. Biomass of algae, cyclopoid nauplii, and rotifers responded positively to nutrient additions. Nutrient addition increased algal standing crop 2- to 4-fold and changed dominance from diatoms and chrysophytes to blue-green algae. Diaptomus arcticus accelerated these changes, possibly by eliminating grazing by rotifers. These results suggest that in the absence of increased nutrients D. arcticus directly limits the biomass of herbivorous zooplankton but the indirect effect on phytoplankton is minimal.
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Wright, Robert D. "The Pour-through Nutrient Extraction Procedure." HortScience 21, no. 2 (April 1986): 227–29. http://dx.doi.org/10.21273/hortsci.21.2.227.
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Abstract Nutrient absorption and subsequent plant growth is related to an adequate supply of the nutrient in the soil solution. Thus, fertilizer practices in a nursery and greenhouse should attempt to maintain nutrient levels in the soil solution that promote optimal growth (2, 3). Maintenance of nutrients for greenhouse and nursery crops is usually via slow-release fertilizer or frequent additions through the irrigation water, where mass flow rather than diffusion is probably the predominant process by which nutrients move to plant root surfaces. In effect, the container medium serves primarily as mechanical support for the plant, and, in contrast to mineral soil systems, nutrients adsorbed to the medium are insignificant in relation to the rate of nutrient uptake and subsequent plant growth. This is particularly true for macronutrients, although the extent that it applies to micronutrients is still not clear.
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Miao, S. L., R. E. Borer, and F. H. Sklar. "Sawgrass Seedling Responses to Transplanting and Nutrient Additions." Restoration Ecology 5, no. 2 (June 1997): 162–68. http://dx.doi.org/10.1046/j.1526-100x.1997.09719.x.
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Järvinen, Marko, and Kalevi Salonen. "Influence of changing food web structure on nutrient limitation of phytoplankton in a highly humic lake." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 12 (December 1, 1998): 2562–71. http://dx.doi.org/10.1139/f98-137.
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We determined the potential nutrient limitation of summer phytoplankton production using 2 × 2 × 2 factorial design of enrichment bioassays both before and after the introduction of planktivorous whitefish (Coregonus lavaretus) in a polyhumic lake with an abundant population of the large cladoceran Daphnia longispina. After the fish introduction, Daphnia disappeared and was substituted by the rotifer Keratella cochlearis. During the dominance of Daphnia, additions of nutrients had little or no effect on primary production of phytoplankton in short-term (1-day) incubations. However, 5-day incubations suggested that P most likely was the limiting nutrient. After the fish introduction, both 1- and 5-day enrichment bioassays indicated potential N limitation of phytoplankton production. The strong response of phytoplankton production to combined enrichments with P and N also suggested colimitation by P and N, but this was probably forced by the relatively high additions of nutrients. Consistently low primary production after the combined addition of P and glucose suggests that in the presence of a labile organic C source, epilimnetic bacteria were superior to algae in the uptake of P. Our results suggest that changes in the food web structure may determine the limiting nutrient also in a highly humic lake.
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Giovagnetti, V., C. Brunet, F. Conversano, F. Tramontano, I. Obernosterer, C. Ridame, and C. Guieu. "Assessing the role of dust deposition on phytoplankton ecophysiology and succession in a low-nutrient low-chlorophyll ecosystem: a mesocosm experiment in the Mediterranean Sea." Biogeosciences 10, no. 5 (May 3, 2013): 2973–91. http://dx.doi.org/10.5194/bg-10-2973-2013.
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Abstract. In this study, we investigate the response of the phytoplankton community, with emphasis on ecophysiology and succession, after two experimental additions of Saharan dust in the surface water layer of a low-nutrient low-chlorophyll ecosystem in the Mediterranean Sea. Three mesocosms were amended with evapocondensed dust to simulate realistic Saharan dust events, while three additional mesocosms were kept unamended and served as controls. The experiment consisted in two consecutive dust additions and samples were daily collected at different depths (−0.1, −5 and −10 m) during one week, starting before each addition occurred. Data concerning HPLC pigment analysis on two size classes (< 3 and > 3 μm), electron transport rate (ETR) vs. irradiance curves, non-photochemical fluorescence quenching (NPQ) and phytoplankton cell abundance (measured by flow cytometry), are presented and discussed in this paper. Results show that picophytoplankton mainly respond to the first dust addition, while the second addition leads to an increase of both pico- and nano-/microphytoplankton. Ecophysiological changes in the phytoplankton community occur, with NPQ and pigment concentration per cell increasing after dust additions. While biomass increases after pulses of new nutrients, ETR does not greatly vary between dust-amended and control conditions, in relation with ecophysiological changes within the phytoplankton community, such as the increase in NPQ and pigment cellular concentration. A quantitative assessment and parameterisation of the onset of a phytoplankton bloom in a nutrient-limited ecosystem is attempted on the basis of the increase in phytoplankton biomass observed during the experiment. The results of this study are discussed focusing on the adaptation of picophytoplankton to nutrient limitation in the surface water layer, as well as on size-dependent competition ability in phytoplankton.
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Stutter, Marc, Daniel Graeber, and Gabriele Weigelhofer. "Available Dissolved Organic Carbon Alters Uptake and Recycling of Phosphorus and Nitrogen from River Sediments." Water 12, no. 12 (November 26, 2020): 3321. http://dx.doi.org/10.3390/w12123321.
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Concurrent with nutrient pollution, agriculture has significantly impacted the quantity, composition, and bioavailability of catchment-derived dissolved organic carbon (DOC) in stream ecosystems. Based on the stoichiometric theory, we tested the hypothesis that bioavailable DOC will stimulate the heterotrophic uptake of soluble reactive P (SRP) and inorganic nitrogen in stream sediments. In a simplified laboratory column flow-through study, we exposed stream sediments to additions of glucose, nitrate, and phosphate alone and in combination (+C, +NP, +CNP), and calculated gross and net changes in DOC and nutrients via a mass balance approach. Our results show that glucose-C increased nutrient uptake, but also that NP additions resulted in the enhanced consumption of both native and added organic C. The effects of C addition were stronger on N than P uptake, presumably because labile C stimulated both assimilation and denitrification, while part of the P uptake was due to adsorption. Internal cycling affected net nutrient uptake due to losses of dissolved organically-complexed P and N (DOP and DON). Overall, our study shows that increases in the stoichiometric availability of organic carbon can stimulate N and P sequestration in nutrient-polluted stream sediments. Future studies are required to assess the effects of complex organic carbon sources on nutrient uptake in stream sediments under different environmental conditions, and whether these stoichiometric relations are relevant for ecosystem management.
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Villegas-Pangga, Gina, G. J. Blair, and R. D. B. Lefroy. "Measurement of decomposition and associated nutrient release from barrel medic (Medicago truncatula) hay and chickpea (Cicer arietinum) straw using an in vitro perfusion system." Australian Journal of Agricultural Research 51, no. 5 (2000): 563. http://dx.doi.org/10.1071/ar99118.
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Two in vitro laboratory experiments were conducted to evaluate the effects of nutrient additions, soil inoculation, and sampling times on the decomposition rates and nutrient release patterns of leguminous crop residues. Cumulative CO2 evolution and the percentage nutrient release from barrel medic hay (Medicago truncatula) and chickpea straw (Cicer arietinum) were determined over a 6-week period using a 0.005 M CaCl2 recycling system (UNE in vitro perfusion apparatus). The decomposition study was carried out at 25˚C in a controlled temperature laboratory. There were no significant differences between the decomposition rates of the 2 residues. The percentage C release was not significantly affected by nutrient addition or by soil inoculation. More than 50% of the total C that was released from the residues occurred in the first 7 days with peak release at 3–4 days. Because of an accumulation of nutrients in a muscilaginous substance in the apparatus, and adsorption of P to the plastic, it was not possible to measure the release of nutrients from the residues by sampling the perfusion solution. This had to be achieved by direct measurement of loss of nutrients from the residues. Except for K, the nutrient released from residues was not affected by residue or sampling time.
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Goh, Tee Boon, M. R. Banerjee, Shihua Tu, and D. L. Burton. "Vesicular arbuscular mycorrhizae-mediated uptake and translocation of P and Zn by wheat in a calcareous soil." Canadian Journal of Plant Science 77, no. 3 (July 1, 1997): 339–46. http://dx.doi.org/10.4141/p95-079.
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Vesicular-arbuscular mycorrhizae (VAM) have been credited with improving the growth and mineral nutrition of many host plants but these effects are moderated by soil factors and nutrient balance. We investigated the combined effects of VAM, zinc and phosphorus application on the growth, uptake and translocation of nutrients in wheat using a calcareous soil marginal in P and Zn. Wheat was grown in a growth chamber under various combinations of VAM, P and Zn with measurements done at heading stage and maturity. Vegetative dry matter accumulation was increased by P additions and reduced by VAM infection. Both P addition and VAM infection increased grain yield. Zinc concentration and uptake were generally reduced by P additions and VAM infection. There was an absence of antagonistic effects of Zn additions on P concentration and uptake. In contrast, VAM infection had both positive and negative effects on P uptake depending on the growth stage and translocation of nutrients. We observed that in calcareous soils where the Zn and P fertilizer combinations were adequate for growth, the role of VAM in enhancing the translocation of Zn and P from root and straw to grain is beneficial towards seed set and yield. Key words: VA mycorrhizae, P and Zn fertilization, calcareous soil, wheat, yield, nutrient acquisition, translocation
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Witkowski, E. T. F. "Effects of nutrient additions on litter production and nutrient return in a nutrient-poor Cape fynbos ecosystem." Plant and Soil 117, no. 2 (July 1989): 227–35. http://dx.doi.org/10.1007/bf02220716.
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Pouliot, Rémy, Line Rochefort, and Gilles Gauthier. "Moss carpets constrain the fertilizing effects of herbivores on graminoid plants in arctic polygon fens." Botany 87, no. 12 (December 2009): 1209–22. http://dx.doi.org/10.1139/b09-069.
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We conducted a fertilization experiment in polygon fens that were grazed by Greater Snow Geese on Bylot Island (Canadian Arctic) to determine whether mosses can interfere with nutrient cycling and thereby prevent a direct fertilizing effect of herbivore faeces on vascular plants. We measured the effects of nitrogen (N), phosphorus (P), and faecal addition on growth parameters and nutrient content of graminoids and mosses over a 2 year period. Growth and nutrient content of graminoids were enhanced only for high levels of N addition (5 g·m–2 per season), and showed little response to P addition. Although the growth of mosses showed a slight response to N or P addition, it is primarily nutrient content that was generally enhanced at all levels of fertilization. In many cases, stronger responses were detected when N and P were applied in combination, rather than singly. Addition of goose droppings had no effect on any measured parameters. Our results suggest that bryophytes act as a natural barrier by absorbing nutrients from external additions, thus blocking the access of highly assimilable nutrients to graminoid plant roots. At increased levels of N addition, bryophytes were apparently saturated so the nutrient surplus leached down to roots and was thus available for graminoid plant growth. The presence of a thick moss layer likely explains why the deposition of faeces by herbivores such as geese has no effect on graminoid growth in arctic polygon fens.
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Tsoy, Zoya, Yuri Nikulin, and Olga Nikulina. "Effect of marine feed additions on the digestibility of poultry nutrients." E3S Web of Conferences 210 (2020): 06022. http://dx.doi.org/10.1051/e3sconf/202021006022.
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Poultry farming is one of the most important branch of animal husbandry. Poultry is very sensitive to a lack of protein, vitamins, microelements and macroelements. The lack of these substances is very bad for the health, development, growth and productivity of poultry. Primorsky Krai is rich in seafood, which is extracted in large quantities. In the process of processing seafood, a large amount of waste remains, which could be used for feed purposes, for feeding farm animals and poultry. The use of seafood waste would solve the problem with a nutrient deficiency in the diets of poultry. The digestibility of feed nutrients is a secondary indicator of their nutritional value. The better the nutrients are digested in the animal's body, the more nutritious the food is. In our research work, we studied the influence of marine hydrobionts on the digestibility of dietary nutrients.
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Rose, Laura, Robert Buitenwerf, Michael Cramer, Edmund C. February, and Steven I. Higgins. "Effects of nutrient supply on carbon and water economies of C4 grasses." Functional Plant Biology 45, no. 9 (2018): 935. http://dx.doi.org/10.1071/fp17359.
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C3 plants can increase nutrient uptake by increasing transpiration, which promotes the flow of water with dissolved nutrients towards the roots. However, it is not clear if this mechanism of nutrient acquisition, termed ‘mass flow’, also operates in C4 plants. This is an important question, as differences in mass flow capacity may affect competitive interactions between C3 and C4 species. To test if mass flow can be induced in C4 species, we conducted an experiment in a semiarid seasonal savanna in South Africa. We grew six C4 grasses in nutrient-poor sand and supplied no nutrients, nutrients to the roots or nutrients spatially separated from the roots. We measured the rates of photosynthesis and transpiration, water-use efficiency (WUE), nitrogen gain and biomass. For all species biomass, N gain, photosynthesis and transpiration were lowest in the treatment without any nutrient additions. Responses to different nutrient positioning varied among species from no effect on N gain to a 50% reduction when nutrients were spatially separated. The ability to access spatially separated nutrients showed a nonsignificant positive relationship with both the response of transpiration and the response of WUE to spatial nutrient separation. This indicates that nutrient acquisition is not regulated by decreasing WUE in C4 grasses. Overall, our study suggests that under elevated CO2, when evaporative demand is lower, C4 species may be at a competitive disadvantage to C3 species when it comes to nutrient acquisition.
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Morris, Liz, and Michael J. Keough. "Testing the effects of nutrient additions on mudflat macroinfaunal assemblages in the presence and absence of shorebird predators." Marine and Freshwater Research 54, no. 7 (2003): 859. http://dx.doi.org/10.1071/mf02157.
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An issue that is of increasing concern worldwide relates to the possibility that areas subject to conservation agreements, owing to the resident and migratory bird populations they support, will be adversely affected by attempts to reduce organic inputs into nearshore environments. In the present study, we investigated the effects of nutrient additions and shorebird exclusion on the infaunal assemblages of an intertidal mudflat. Where responses to nutrient additions were observed they only occurred in the high-dose treatments, indicating that a high nutrient loading is required before infaunal responses are initiated at this site. There was no evidence to support the idea that nutrient additions would only stimulate macroinfaunal assemblages where shorebird foraging was reduced. Instead, nutrient additions were detectable separately from any effects of shorebird predation and, contrary to expectations, appeared to be of more importance than shorebird predation in this environment. There was also no evidence to suggest that shorebird predation has a strong interaction with the infaunal prey assemblage and, although further studies will be needed to support this statement, it is possible that moderate changes in nutrient status will not impact on the shorebird populations at this site.
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GAUDES, A., J. OCAÑA, and I. MUÑOZ. "Meiofaunal responses to nutrient additions in a Mediterranean stream." Freshwater Biology 57, no. 5 (March 7, 2012): 956–68. http://dx.doi.org/10.1111/j.1365-2427.2012.02757.x.
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Sands, PJ, and PJ Smethurst. "Modelling Nitrogen Uptake in Ingestad Units Using Michaelis-Menten Kinetics." Functional Plant Biology 22, no. 5 (1995): 823. http://dx.doi.org/10.1071/pp9950823.
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The concept of nutrient flux density was developed to grow plants at a controlled and stable relative growth rate whilst maintaining a constant internal concentration of a limiting nutrient. The method requires frequent and exponentially increasing additions of nutrients to replenish uptake. In developing this approach there has been little reference to Michaelis-Menten-like nutrient uptake kinetics for characterising uptake by roots. This paper applies a simple model of nitrogen-limited plant growth using Michaelis-Menten uptake kinetics to data from previously published experiments based on the nutrient flux density approach. It is shown that the model can indeed reproduce key features of experiments: (1) plant relative growth rate equals nitrogen relative addition rate up to a limit; (2) when nitrogen uptake kinetic parameters are within the range reported in the literature, this limiting growth rate agrees with that observed; and (3) solution nitrogen concentrations are consistent with those published. We suggest that the understanding of nutrient uptake and utilisation by plants could be advanced by jointly considering these two approaches.
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Ganf, GG, SJL Stone, and RL Oliver. "Use of protein to carbohydrate ratios to analyse for nutrient deficiency in phytoplankton." Marine and Freshwater Research 37, no. 2 (1986): 183. http://dx.doi.org/10.1071/mf9860183.
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A series of laboratory experiments was designed to investigate the influence of nitrogen, phosphorus and photon irradiance on the protein to carbohydrate ratio and growth rate of Scenedesmus quadricauda. These parameters responded to nutrient additions and depletions in a predictable manner. As nutrients were added the ratio rose to a maximum of 5, but as nutrients were depleted from the medium the ratio fell to < 1 during long-term experiments. The ratio also showed that diurnal fluctuations in cultures grown under a 12 h light : 12 h dark cycle were similar in magnitude to the long-term changes. The extent of these diurnal changes was dependent upon the nutrient status of the cells. In nutrient-saturated medium the ratio showed maximum change (4.2 to 1.1), but in nutrient-depleted medium the change was small (0.98 to 0.81). In addition to these responses to nutrients, the ratio was also influenced by photon flux. At high photon fluxes the ratio showed a marked diurnal change (0.91 to 4.05), but this change decreased with decreasing photon fluxes. A general relationship existed between growth rate and the protein to carbohydrate ratio for ratios >2. Below this value, however, growth rate was independent of the protein to carbohydrate ratio. Criteria based upon these laboratory experiments were derived to determine the nutrient status of field populations of phytoplankton. Using these criteria, the phytoplankton of Mount Bold Reservoir were shown to pass from a condition indicating nutrient sufficiency in November to a condition that implied varying degrees of nutrient deficiency for the period December to March. This pattern of nutrient sufficiency based upon protein to carbohydrate ratios agreed well with the results of nutrient-enrichment trials. This pattern would not have been discernible by the rigid application of previously determined critical protein to carbohydrate ratios.
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Vimercati, Lara, Clifton P. Bueno de Mesquita, and Steven K. Schmidt. "Limited Response of Indigenous Microbes to Water and Nutrient Pulses in High-Elevation Atacama Soils: Implications for the Cold–Dry Limits of Life on Earth." Microorganisms 8, no. 7 (July 16, 2020): 1061. http://dx.doi.org/10.3390/microorganisms8071061.
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Soils on the world’s highest volcanoes in the Atacama region represent some of the harshest ecosystems yet discovered on Earth. Life in these environments must cope with high UV flux, extreme diurnal freeze–thaw cycles, low atmospheric pressure and extremely low nutrient and water availability. Only a limited spectrum of bacterial and fungal lineages seems to have overcome the harshness of this environment and may have evolved the ability to function in situ. However, these communities may lay dormant for most of the time and spring to life only when enough water and nutrients become available during occasional snowfalls and aeolian depositions. We applied water and nutrients to high-elevation soils (5100 meters above sea level) from Volcán Llullaillaco, both in lab microcosms and in the field, to investigate how microbial communities respond when resource limitations are alleviated. The dominant taxon in these soils, the extremophilic yeast Naganishia sp., increased in relative sequence abundance and colony-forming unit counts after water + nutrient additions in microcosms, and marginally in the field after only 6 days. Among bacteria, only a Noviherbaspirillum sp. (Oxalobacteraceae) significantly increased in relative abundance both in the lab and field in response to water addition but not in response to water and nutrients together, indicating that it might be an oligotroph uniquely suited to this extreme environment. The community structure of both bacteria and eukaryotes changed significantly with water and water + nutrient additions in the microcosms and taxonomic richness declined with amendments to water and nutrients. These results indicate that only a fraction of the detected community is able to become active when water and nutrients limitations are alleviated in lab microcosms, and that water alone can dramatically change community structure. Our study sheds light on which extremophilic organisms are likely to respond when favorable conditions occur in extreme earthly environments and perhaps in extraterrestrial environments as well.
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Giovagnetti, V., C. Brunet, F. Conversano, F. Tramontano, I. Obernosterer, C. Ridame, and C. Guieu. "Assessing the role of dust deposition on phytoplankton ecophysiology and succession in a low-nutrient low-chlorophyll ecosystem: a mesocosm experiment in the Mediterranean Sea." Biogeosciences Discussions 9, no. 12 (December 21, 2012): 19199–243. http://dx.doi.org/10.5194/bgd-9-19199-2012.
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Abstract. In this study, we investigate the phytoplankton community response, with emphasis on ecophysiology and succession, after two experimental additions of Saharan dust in the surface layer of a low-nutrient low-chlorophyll ecosystem in the Mediterranean Sea. Three mesocosms were amended with evapocondensed dust to simulate realistic Saharan dust events while three additional mesocosms were kept unamended and served as controls. Experiments consisted in two consecutive dust additions and samples were daily collected at different depths (−0.1, −5 and −10 m) during one week, starting before each addition occurred. Data concerning HPLC pigment analysis on two size classes (< 3 and > 3 µm), electron transport rate (ETR) versus irradiance curves, non-photochemical fluorescence quenching (NPQ) and phytoplankton cell abundance (measured by flow cytometry), are presented and discussed in this paper. Results show that picophytoplankton mainly respond to the first dust addition, while the second addition leads to an increase of both pico- and nano-/microphytoplankton. Ecophysiological changes in the phytoplankton community are revealed, and an increase in NPQ development, as well as in pigment concentration per cell, follows the dust additions. ETR does not show large variations between dust-amended and control conditions, while biomass increases in response to the dust additions. Furthermore, the biomass increase observed during this mesocosm experiment allows us to attempt a quantitative assessment and parameterization of the onset of a phytoplankton bloom in a nutrient-limited ecosystem. These results are discussed focusing on the adaptation of picophytoplankton to such a nutrient-limited mixed layer system, as well as on size-dependent competition ability in phytoplankton.
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Weaver, Daniel M., Stephen M. Coghlan, and Joseph Zydlewski. "Sea lamprey carcasses exert local and variable food web effects in a nutrient-limited Atlantic coastal stream." Canadian Journal of Fisheries and Aquatic Sciences 73, no. 11 (November 2016): 1616–25. http://dx.doi.org/10.1139/cjfas-2015-0506.
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Resource flows from adjacent ecosystems are critical in maintaining structure and function of freshwater food webs. Migrating sea lamprey (Petromyzon marinus) deliver a pulsed marine-derived nutrient subsidy to rivers in spring when the metabolic demand of producers and consumers are increasing. However, the spatial and temporal dynamics of these nutrient subsidies are not well characterized. We used sea lamprey carcass additions in a small stream to examine changes in nutrients, primary productivity, and nutrient assimilation among consumers. Algal biomass increased 57%–71% immediately adjacent to carcasses; however, broader spatial changes from multiple-site carcass addition may have been influenced by canopy cover. We detected assimilation of nutrients (via δ13C and δ15N) among several macroinvertebrate families including Heptageniidae, Hydropsychidae, and Perlidae. Our research suggests that subsidies may evoke localized patch-scale effects on food webs, and the pathways of assimilation in streams are likely coupled to adjacent terrestrial systems. This research underscores the importance of connectivity in streams, which may influence sea lamprey spawning and elicit varying food web responses from carcass subsidies due to fine-scale habitat variables.
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Pereira, Danielle Goeldner, Fábio Amodêo Lansac-Tôha, Gustavo Mayer Pauleto, Luis Mauricio Bini, and Luiz Felipe Machado Velho. "Effects of nitrogen and phosphorus on the abundance and cell size of planktonic nanoflagellate communities." Acta Limnologica Brasiliensia 24, no. 4 (April 19, 2013): 427–37. http://dx.doi.org/10.1590/s2179-975x2013005000009.
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AIM: We experimentally investigated the effects of nutrients (Nitrogen and Phosphorus) enrichment on the density, biomass, and cell size of pigmented and heterotrophic plankton nanoflagellates communities. METHODS: The experiment was done in mesocosms in a tropical reservoir during a 19-day period. Four different treatments were carried out: Control (non-nutrient addition - C), phosphorus additions (P), nitrogen addition (N) and phosphorus + nitrogen addition (N + P). Each treatment was performed in triplicate, sorted randomly, thus giving a total of 12 experimental carboys, which were placed transversely in the middle of the reservoir. RESULTS: In general, pigmented and heterotrophic nanoflagellates fractions responded to nutrient addition, increasing densities and biomass values at the fertilized treatments. Opposed to expected, enriched treatments resulted in a slight decrease in mean cell size of the pigmented fraction. Moreover, in nutrient-rich treatments, pigmented nanoflagellates had higher relative abundance than in the control. CONCLUSIONS: Our results indicate that: i) the density and biomass of nanoflagellates responded to the nutrient enrichment, mainly when N and P were added together; ii) the pigmented and heterotrophic fractions showed distinct time responses to fertilization; iii) the growth of nanoflagellate community seems to be co-limited by N and P; iv) the nutrient enrichment led to a greater pigmented than heterotrophic fraction contribution; and v) among the analyzed variables, nanoflagellate densities seem to be more sensitive to changes in nutrient availability than biomass or mean cell size.
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Barlett, Melissa A., and Laura G. Leff. "The effects of N:P ratio and nitrogen form on four major freshwater bacterial taxa in biofilms." Canadian Journal of Microbiology 56, no. 1 (January 2010): 32–43. http://dx.doi.org/10.1139/w09-099.
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Bacteria in freshwater systems play an important role in nutrient cycling through both assimilatory and dissimilatory processes. Biotic and abiotic components of the environment affect these transformations as does the stoichiometry of the nutrients. We examined responses of four major taxa of bacteria in biofilms subjected to various N:P molar ratios using either nitrate or ammonium as a nitrogen source. Fluorescent in situ hybridization was used to enumerate the Domain bacteria as well as the α-, β-, and γ-proteobacteria, and the Cytophaga–Flavobacteria cluster. Generally, bacterial responses to the treatments were limited. However, the Cytophaga–Flavobacteria and β-proteobacteria both responded more to the ammonium additions than nitrate, whereas, the α-proteobacteria responded more to nitrate additions. The β-proteobacteria also exhibited peak relative abundance at the highest N:P ratio. Nutrient concentrations were significantly different after the incubation period, and there were distinct changes in the stoichiometry of the microcosms with ammonium. We demonstrated that bacteria may play an important role in nutrient uptake, and transformation, and can have a dramatic effect on the nutrient stoichiometry of the surrounding water. However, although some taxa exhibited differences in response to ammonium and nitrate, the impact of nutrient stoichiometry on the abundance of the taxa examined was limited.
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Vitousek, Peter M., Grant Gerrish, Douglas R. Turner, Lawrence R. Walker, and Dieter Mueller-Dombois. "Litterfall and nutrient cycling in four Hawaiian montane rainforests." Journal of Tropical Ecology 11, no. 2 (May 1995): 189–203. http://dx.doi.org/10.1017/s0266467400008634.
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ABSTRACTThe mass of fine litterfall and nutrient circulation through litterfall were determined in four Melrosideros polymorpha/Cibotium spp.-dominated rainforests that differed in substrate age, parent material texture and annual precipitation on Kilauea and Mauna Loa volcanoes on the island of Hawaii. Three of the sites had rates of litterfall of 5.2 Mg ha−1 y−1; the fourth, which was on the most fertile soil, produced 7.0 Mg ha−1 y−1 of litterfall with higher concentrations of nitrogen and phosphorus. Tree ferns of the genus Cibotium cycled relatively large amounts of nitrogen, phosphorus and potassium through litterfall; their contribution to nutrient circulation was disproportionate to their mass in the forest, or in litterfall. The forest on the youngest substrate, which also had the lowest concentrations of nitrogen in litterfall, was fertilized with complete factorial combinations of nitrogen, phosphorus and a treatment consisting of all other plant nutrients. Additions of nitrogen increased the quantity and nitrogen concentration in litterfall during the second year following the initiation of fertilization, while no other treatment had a significant effect. Additions of nitrogen had no effect on litterfall mass or nutrient concentrations in the most nutrient-rich site.
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Hong, Daniel S., Kara E. Gonzales, Timothy J. Fahey, and Ruth D. Yanai. "Foliar nutrient concentrations of six northern hardwood species responded to nitrogen and phosphorus fertilization but did not predict tree growth." PeerJ 10 (April 21, 2022): e13193. http://dx.doi.org/10.7717/peerj.13193.
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Foliar chemistry can be useful for diagnosing soil nutrient availability and plant nutrient limitation. In northern hardwood forests, foliar responses to nitrogen (N) addition have been more often studied than phosphorus (P) addition, and the interactive effects of N and P addition have rarely been described. In the White Mountains of central New Hampshire, plots in ten forest stands of three age classes across three sites were treated annually beginning in 2011 with 30 kg N ha−1 y−1 or 10 kg P ha−1 y−1 or both or neither–a full factorial design. Green leaves of American beech (Fagus grandifolia Ehrh.), pin cherry (Prunus pensylvanica L.f.), red maple (Acer rubrum L.), sugar maple (A. saccharum Marsh.), white birch (Betula papyrifera Marsh.), and yellow birch (B. alleghaniensis Britton) were sampled pre-treatment and 4–6 years post-treatment in two young stands (last cut between 1988–1990), four mid-aged stands (last cut between 1971–1985) and four mature stands (last cut between 1883–1910). In a factorial analysis of species, stand age class, and nutrient addition, foliar N was 12% higher with N addition (p < 0.001) and foliar P was 45% higher with P addition (p < 0.001). Notably, P addition reduced foliar N concentration by 3% (p = 0.05), and N addition reduced foliar P concentration by 7% (p = 0.002). When both nutrients were added together, foliar P was lower than predicted by the main effects of N and P additions (p = 0.08 for N × P interaction), presumably because addition of N allowed greater use of P for growth. Foliar nutrients did not differ consistently with stand age class (p ≥ 0.11), but tree species differed (p ≤ 0.01), with the pioneer species pin cherry having the highest foliar nutrient concentrations and the greatest responses to nutrient addition. Foliar calcium (Ca) and magnesium (Mg) concentrations, on average, were 10% (p < 0.001) and 5% lower (p = 0.01), respectively, with N addition, but were not affected by P addition (p = 0.35 for Ca and p = 0.93 for Mg). Additions of N and P did not affect foliar potassium (K) concentrations (p = 0.58 for N addition and p = 0.88 for P addition). Pre-treatment foliar N:P ratios were high enough to suggest P limitation, but trees receiving N (p = 0.01), not P (p = 0.64), had higher radial growth rates from 2011 to 2015. The growth response of trees to N or P addition was not explained by pre-treatment foliar N, P, N:P, Ca, Mg, or K.
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Ramey, Tonya L., Cindy E. Prescott, and John S. Richardson. "Influence of moisture, nutrients, and distance from stream on early-stage mass loss of western red cedar leaf litter in headwater riparian forests." Canadian Journal of Forest Research 50, no. 12 (December 2020): 1391–98. http://dx.doi.org/10.1139/cjfr-2020-0176.
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Western red cedar (Thuja plicata Donn ex D.Don) is a dominant species in forests of the Pacific Northwest in North America, but little is known about its decomposition in riparian habitat. We experimentally tested how early-stage mass loss of cedar leaf litter varied with distance from the stream (five distances from 1 to 40 m away) and responded to nutrient and water additions near four headwater streams in southwestern British Columbia. We ran three coarse-mesh litterbag trials in durations between five months to one year from January 2013 and January 2014. Litterbags were either untreated or given the following treatments: water additions during dry summer months, nitrogen and phosphorus additions, or additions of both. Control litterbags lost 21% initial mass over 12 months (January 2013 – January 2014), 20% over five months (January 2013 – June 2013), and 15% over eight months (June 2013 – January 2014). Rates of mass loss did not increase with water in any trial but did increase with nutrients in the 12-month trial. Litter located 40 m from the stream lost 7% more mass than that located 1 m away in this same trial. Our study indicates that cedar leaf litter mass loss responded primarily to nutrient additions.
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Posey, Martin H., Troy D. Alphin, Lawrence Cahoon, David Lindquist, and Meredith E. Becker. "Interactive Effects of Nutrient Additions and Predation on Infaunal Communities." Estuaries 22, no. 3 (September 1999): 785. http://dx.doi.org/10.2307/1353111.
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MACEK, P., and E. REJMÁNKOVÁ. "Response of emergent macrophytes to experimental nutrient and salinity additions." Functional Ecology 21, no. 3 (June 2007): 478–88. http://dx.doi.org/10.1111/j.1365-2435.2007.01266.x.
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Rosemond, A. D., J. P. Benstead, P. M. Bumpers, V. Gulis, J. S. Kominoski, D. W. P. Manning, K. Suberkropp, and J. B. Wallace. "Experimental nutrient additions accelerate terrestrial carbon loss from stream ecosystems." Science 347, no. 6226 (March 5, 2015): 1142–45. http://dx.doi.org/10.1126/science.aaa1958.
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Wang, Wen-Xiong, and Robert C. H. Dei. "Effects of major nutrient additions on metal uptake in phytoplankton." Environmental Pollution 111, no. 2 (February 2001): 233–40. http://dx.doi.org/10.1016/s0269-7491(00)00071-3.
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Bidartondo, M. I., H. Ek, H. Wallander, and B. Soderstrom. "Do nutrient additions alter carbon sink strength of ectomycorrhizal fungi?" New Phytologist 151, no. 2 (August 2001): 543–50. http://dx.doi.org/10.1046/j.1469-8137.2001.00180.x.
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Bokn, Tor L., Carlos M. Duarte, Morten F. Pedersen, Nuria Marba, Frithjof E. Moy, Cristina Barr�n, Birger Bjerkeng, et al. "The Response of Experimental Rocky Shore Communities to Nutrient Additions." Ecosystems 6, no. 6 (October 1, 2003): 577–94. http://dx.doi.org/10.1007/s10021-002-0108-6.
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Rifai, Husen, Firman Zulpikar, Muhammad Safaat, Jeverson Renyaan, Laode Alifatri, and Asep Rasyidin. "Responses of Seagrass Amphibolis antarctica Roots to Nutrient Additions Along a Salinity Gradient in Shark Bay, Western Australia." Omni-Akuatika 17, no. 2 (December 1, 2021): 90. http://dx.doi.org/10.20884/1.oa.2021.17.2.913.
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Seagrass meadows in oligotrophic environments are particularly susceptible to nutrient enrichment, yet morphological and architectural seagrass root responses in these ecosystems are poorly understood. This study aimed to investigate the response of Amphibolis antarctica, one of dominant seagrass species in Shark Bay, roots to nutrient additions along a salinity gradient in the oligotrophic ecosystem of Shark Bay, Western Australia. A fully factorial nutrient additional experiment with four treatments (Control, N, P and N+P) was conducted at each of five sites along a salinity gradient (between ~38ppt in site 1 and ~50ppt in site 5) in Shark Bay across a three-year period (2012-2015). In the laboratory, the roots morphology and architecture A. antarctica were investigated using a software (WinRhizo). Then, a two-way analysis of variance (ANOVA) was performed to investigate if there was a significant change in the morphology and architecture of the roots after the nutrient inputs and along five sites with salinity gradient. There was no significant impact of nutrient addition on the root’s morphology and architecture of A. antarctica species. However, the effect of site factor with salinity gradient was significant to all morphological aspects (total root length, root surface area and root diameter) of A. antarctica roots. These findings highlight the more ecological function of A. antarctica roots being in anchoring of the plant into the seafloor rather than to absorb nutrient from the sediment.Keywords: Nutrient addition, Oligotrophic habitats, Amphibolis antarctica, Shark Bay
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Duarte, Carlos M., Anna Lucea, and Morten Søndergaard. "The effect of nutrient additions on the partitioning of nutrients in an experimental coastal Mediterranean system." Biogeochemistry 68, no. 2 (April 2004): 153–67. http://dx.doi.org/10.1023/b:biog.0000025735.03721.64.
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