Influence Of Nutrient Addition Research Articles

Imbalanced stoichiometric patterns in foliar nutrient resorption response to N and P addition in grazing alpine grassland

Although the effect of nutrient availability on plant nutrient resorption has been extensively studied, the influence of nutrient addition on the coupled biogeochemical cycling of N and phosphorus (P) remains unclear. Studies on how increased nutrient addition affects the imbalance between N and P resorption are limited. We investigated the influence of a wide nutrient addition gradient on the foliar nutrient resorption of dominant grass, Stipa capillata, in grazing alpine grassland. We applied seven addition levels for N (0.5–24 g N ∙ m−2 yr−1) and P (0.05–3.2 g P ∙ m−2 yr−1), collected plant and soil samples, and calculated plant foliar nutrient resorption. Results showed that N and P resorption efficiencies decreased with increasing N addition and N:P resorption ratios. However, N and P resorption efficiencies significantly decreased but N:P resorption ratios increased with the P addition gradient. Moreover, the N:P resorption ratios were negatively correlated with senesced foliar N:P ratios. Our findings suggest that N and P responses to nutrient fertilization are tightly coupled at the intraspecific level. Hence, plants show different tendencies of resorbing nutrient with N and P addition, leading to imbalance between N and P. Plant stoichiometric patterns were regulated by the nutrient status of senesced foliar. This study reveals that nutrient additions accelerate ecosystem N and P cycling, N and P cycles are coupled, but their resorptions are imbalanced. The imbalanced stoichiometric patterns in foliar nutrient resorption response to nutrient enrichment provide insights into N and P cycling under human-driven nutrient imbalance scenarios.

The influence of nutrient addition on the invasion of Spartina alterniflora towards the non-tidal wetlands in the Chinese Yellow River delta

Spartina alterniflora is a notoriously invasive species in the low marsh of China, and meanwhile anthropogenic eutrophication is an urgent and prevalent environmental problem in the coastal wetlands. Soils in the coastal wetland are nutrient-poor, nutrient enrichment may enhance the spread of S. alterniflora towards the non-tidal marsh of the Yellow River Delta. We conducted a 2-year transplant and nutrient addition field experiment to investigate the influence of nutrient enrichment and interspecific interactions on the performance (growth, survival or inflorescence) of S. alterniflora. We found that nutrient addition and species competition did not have significant effects on the variation in performances of S. alterniflora. However, vegetative zones (Suaeda salsa and Phragmites australis), years (2013 and 2014) significantly contributed to the variation. The biomass per stem, survival and inflorescence were much higher in the P. australis than the S. salsa zone (biomass per stem: 1.86 ± 0.17 g vs. 0.82 ± 0.15 g; survivorship: 79% vs. 36%; inflorescence: 40% vs. 2%), and in 2013 than 2014 (biomass per stem: 1.72 ± 0.19 g vs. 0.91 ± 0.13 g; survivorship: 65% vs. 50%; inflorescence: 36% vs. 6.94%), which may be due to the combination of less flooding frequency and high salinity in the S. salsa zone and year 2014. These findings implied that eutrophication may not enhance the spread of S. alterniflora towards the non-tidal wetlands in the Chinese Yellow River Delta.

Hexadecane mineralization activity in hydrocarbon-contaminated soils of Ross Sea region Antarctica may require nutrients and inoculation

Hydrocarbon spills on Antarctic soils occur mainly near settlements where fuel is stored and aircraft and vehicles are refuelled. To investigate those factors that may preclude hexadecane mineralization activity in long-term hydrocarbon-contaminated soils from the Ross Sea Region, samples were collected from Scott Base, the site of former bases (Cape Evans, Marble Point, Vanda Station), and two oil spill sites in the Wright Valley (Bull Pass and Loop Moraine). The soils had low levels of nitrogen (<0.1% total N) and a high C/N ratio (>24) reflecting hydrocarbon contamination. Following soil water adjustment to 10% (v/w), the influence of nutrient addition (250 mg/kg N added as monoammonium phosphate) and inoculation (spiking with Antarctic soil containing high numbers of hydrocarbon degraders) as required on hexadecane mineralization activity was determined. Hexadecane mineralization activity occurred in contaminated soils from Marble Point, Cape Evans and one sample from Vanda Station without nutrient addition. In contrast soils from Scott Base, Cape Evans, another sample from Vanda Station and Loop Moraine required nutrients, whereas Bull Pass soil required inoculation and nutrients before hexadecane mineralization proceeded. Hydrocarbon degrader numbers were highest in coastal soils from Scott Base and Marble Point (107 per gram) and less prevalent in inland soils from Wright Valley (<105 per gram). The bacterial community structure of the soils differed between sites, but soils from the same sites tended to cluster together more closely, except for those from Vanda Station. Addition of nutrients did not cause large shifts in the soil bacterial communities. Results from this study indicate that hydrocarbon degradation may occur at some sites in summer when water is available. Long-term hydrocarbon-contaminated Antarctic soils may provide a valuable resource of hydrocarbon-degrading bacteria that can serve as inocula for more recent oil spills on land.

Influence of nutrient addition on growth and accumulation of cadmium and copper in Lemna gibba

Aquatic plants have been identified as potentially useful for accumulating and bioconcentrating heavy metals. This study was developed to test the hypothesis that nutrient enrichment enhances the metal tolerance of floating macrophytes. Relative growth rates (RGR), photosynthetic pigments (chlorophyll a, b and carotenoid), malondialdehyde (MDA) content, and electrical conductivity (EC) were measured in Lemna gibba exposed to different cadmium and copper concentrations in laboratory conditions. Relative growth rates were negatively correlated with metal exposure, but nutrient addition suppressed this effect. Photosynthetic pigment levels were negatively correlated with metal exposures, and nutrient addition attenuated chlorophyll decrease in response to metal exposures. MDA content and EC also showed sharp increases at higher concentrations, indicating oxidative stress. This study indicates that nutrient enrichment increases the tolerance of Lemna gibba to metals, and that Lemna gibba is a suitable candidate for the phytoremediation of low-level copper and cadmium pollution.

Stimulation of the brown tide organism, Aureococcus anophagefferens, by selective nutrient additions to in situ mesocosms

The influence of nutrient additions and sediment exchange on Aureococcus anophagefferens growth was studied using 200 l mesocosms deployed in situ at the Southampton College Marine Science Center in Long Island, New York. A. anophagefferens cell density increased in mesocosms with separate additions of the following materials: urea + glucose and desiccation-stressed Enteromorpha tissue. A decrease in A. anophagefferens cell density was observed in mesocosms with either no additions (control) or with added nitrate. A treatment containing a sediment layer exhibited an increase in average cell densities, but the increase was not statistically significant ( P = 0.15). In the 9 day experiment, net growth of A. anophagefferens was only observed during the last 3 days, which corresponded to a period of high solar irradiation. Total chlorophyll concentration declined in all treatments during the first 6 days, which corresponded to relatively low daily irradiance, suggesting low-light stress on the phytoplankton assemblage during the initial phase of the experiment. During the ensuing sunny period, a 4–5-fold increase in chlorophyll concentration was observed in the nitrate and urea treatments with lesser increases in the other treatments. A. anophagefferens density increased relative to total phytoplankton biomass (Chl basis) in the urea + glucose and Enteromorpha treatments. Results are consistent with a prevailing hypothesis that organic nitrogen nutrients favor the growth of A. anophagefferens. Specifically, our evidence indicates that A. anophagefferens exhibited net population growth under organic N, but not inorganic N nutrient (specifically NO 3 −) loading.

Modelling of Spirulina platensis growth in fresh water using response surface methodology

The influence of nutrient addition on the growth rate of Spirulina platensis in the Mangueira Lagoon water was studied in order to investigate the feasibility of using this water for biomass production. The addition of urea and sodium bicarbonate was studied through surface response methodology, over concentration ranges from 0.0 to 0.01170 M, and 0.0–19.70 gl−1 respectively. The growth of Spirulina platensis in Mangueira Lagoon water with no addition of nutrients was carried out and compared with the biomass growth after nutrient addition. The results indicated that the optimal level of nutrients was 0.00585 M urea and without the addition of sodium bicarbonate. The biomass concentration was 1.4 gl−1 in 780 h of cultivation and the doubling time (t d) was 3.85 days. In 300 h, the biomass concentration in the medium without nutrient addition was 0.9 gl−1, with a doubling time of 3.80 days.

Influence of nutrient additions on cadmium bioaccumulation by aquatic invertebrates in littoral enclosures

AbstractCadmium distribution and bioaccumulation were examined over a 2‐year period (1991–1992) in two nutrient‐enriched and two control littoral enclosures and in the littoral zone in Lake 382 (L382). Lake 382, a small oligotrophic lake, is located within the Experimental Lakes Area in northwestern Ontario, Canada, and received experimental Cd additions from 1987 to 1992. In the second year of this study, chlorophyll a and suspended C concentrations in the nutrient‐enriched enclosures increased by 6.6 and 3.4 times, respectively, compared to the controls. As a result of increased particulate produced by the nutrient additions, Cd concentrations in water from the nutrient‐enriched enclosures were higher (46–114 ng/L) compared to the controls (23–84 ng/ L). Estimated Cd/C concentrations in water were lower in the nutrient‐enriched enclosures relative to the controls because of higher particle concentrations. Effects on Cd bioaccumulation were limited even though mesotrophic to eutrophic conditions were reached in the nutrient‐enriched enclosures. Trends for lower Cd concentrations in mussels and crayfish from the nutrient‐enriched enclosures compared to the controls were observed; however, significant differences were rarely detected. Zooplankton and immature Chironomidae from the nutrient‐enriched enclosures had consistently higher Cd concentrations compared to the controls, but significant differences were not detected. Enhanced accumulation of Cd‐rich particulate matter by these organisms may account for this trend. Mussels and crayfish accumulated significantly more Cd when exposed in the lake compared to the enclosures. This observation is due to elevated Cd water concentrations in the lake compared to the enclosures because of continued Cd additions to the lake. These results suggest that the water route of exposure is an important pathway for Cd accumulation by these organisms.

The influence of nutrient addition on growth rates of phytoplankton groups, and microzooplankton grazing rates in a mesocosm experiment

The influence of nutrient addition on the growth and microzooplankton grazing rates of individual phytoplankton groups was investigated in a mesocosm experiment including nutrient manipulation and using the dilution technique. The nutrient addition caused phytoplankton biomass to increase; chlorophyll a was less than 3.5 μg l −l in the control enclosure, while chlorophyll a increased to 19 and 35 μg l −l in enclosures added nitrogen and phosphate (NP) and nitrogen, phosphate and silicate (NPSi), respectively. The growth and grazing rates were highly variable during the experimental period and the grazing rates were significantly correlated to the growth rates. Diatoms, prymnesiophytes, and dinoflagellates occasionally reached very high growth rates, up to 2.8 d −l. The phytoplankton in the NPSi enclosure consisted mostly of diatoms, which proved unsuitable for incubation, since they formed aggregates in the incubation bottles, and the dilution experiments carried out in this enclosure were consequently not successful. The addition of nutrients (N, P, Si, Mn, and Fe) to the dilution experiment caused an increase in the growth rates of the phytoplankton both in the control and the NP enclosures. In both the control and NP enclosures, the growth rates of the diatoms increased significantly owing to nutrient addition.

The effect of nutrient additions on bacterial activity in seagrass ( Posidonia oceanica) sediments

The influence of nutrient additions on benthic bacterial activity under seagrass meadows was tested by enriching five seagrass ( Posidonia oceanica) meadows with nutrients over one year. We found a highly significant response of benthic bacterial activity to nutrient additions, which was reflected in greater (about two-fold) ammonification rates and, to a smaller extent, a significant tendency for a greater exoenzymatic activity. Nutrient additions significantly raised bacterial activity, without altering the seasonal changes in bacterial activity. As a result of the increased bacterial activity, the organic content of the sediments declined significantly, by about 33%, after one year of nutrient addition. Hence, nutrient additions to the seagrass meadows enhance seagrass production but also accelerate bacterial decomposition of seagrass carbon, thereby reducing the capacity of the sediments to store organic carbon. These results demonstrate that sediment nutrient availability limits bacterial activity in these Posidonia oceanica meadows, and identify bacteria as important nutrient consumers in these systems.

Seasonal Changes in Nitrogen Compartments of Lakes Under Different Loading Conditions

To develop a better conceptual picture for nitrogen dynamics in lake ecosystems, the seasonal changes in the concentrations of nitrate, ammonia, dissolved organic and particulate nitrogen were monitored in the water contained in three limnocorrals located in the Bay of Quinte, Ontario. Following the decline in summer particulate N, there was an increase in ammonia. This was followed by an increase in nitrate throughout the winter suggesting that nitrification was a significant process. To assess the potential contribution of the sediments, ammonia, nitrate, and dissolved organic N were measured for pore waters and total N, exchangeable ammonia, and nitrate in the solid fraction. The influence of nutrient addition was evaluated by comparing corral I, receiving no nutrient additions, with corral II to which phosphate was added (0.92 g P/m2 per yr) and corral III which received the same amount of phosphate plus nitrate at an N:P weight ratio of 13. Increases and decreases in phosphorus, nitrogen, and chlorophyll a seemed to take place in all three corrals at the same time. There was a considerable delay in the response to nutrient enrichment, but the addition of nitrate and phosphate eventually resulted in a chlorophyll a level greater than that for phosphate enrichment alone. The importance of sediments as a net source of N for the planktonic community was insignificant, but the flux rate for nitrogen to and from the sediment was important. During the summer an input–output budget showed that nitrate loading plus N2 fixation was approximately equal to the net change in the total combined N in the water. This implied that denitrification was not important, but over 12 mo most of the nitrogen that entered the system was lost; hence denitrification must be important at certain times. A lake ecosystem tends to compensate for low or high levels of NO3 loading. Without the addition of nitrogen the requirement was partly met through nitrogen fixation and this can be enhanced by P enrichment. Key words: ammonia, nitrate, nutrient kinetics, nitrogen fixation, denitrification, sediments

Influence of nutrient additions and initial density of plants on production of waterhyacinth Eichhornia crassipes

Additions of nitrogen, potassium, and phosphorus greatly increased the biomass of waterhyacinths in ponds. Concentrations of nitrogen and phosphorus in dried waterhyacinths were generally greatest in plants from pond waters with the highest concentrations of these nutrients. When small waterhyacinths were stocked in enclosures, they produced vegetative offset until the enclosures were packed with plants. The plants grew rapidly in height after enclosures were packed. Accumulation of dry matter, nitrogen, and phosphorus was greatest when plants were growing in height.