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Nitrogen Enrichment (nitrogen + enrichment)
Selected AbstractsNITROGEN ENRICHMENT OF PORPHYRA PERFORATA THROUGH HIGH DOSE PULSE FERTILIZATIONJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Zertuche-González, J. A1., Chanes-Miranda L2., Carmona, R3., Kraemer G4., Chopin T.5 & Yarish, C3 1Universidad Autonoma de Baja California, Instituto de Investigaciones Oceanologicas, PO Box #453, C.P. 22830, Ensenada, Baja California, Mexico. 2CBTIS-41, Km 115 Carretera Transpeninsular, Ensenada, BC Mexico. 3University of Connecticut, Department of Ecology and Evolutionary Biology, 1 University Place, Stamford, CT, 06901-2315, USA. 4State University of New York, Purchase College, Div. of Nat. Sciences, Purchase, NY, 10577, USA. 5University of New Brunswick, Centre for Coastal Studies and Aquaculture and Centre for Environmental and Molecular Algal Research, P.O. Box 5050, Saint John, New Brunswick, E2L 4L5, Canada Porphyra perforata is a highly preferred seaweed used as fodder in abalone culturing due to its relatively high nutritional value. High growth rates of abalone, particularly in the early stages, are suspected to be due the high protein-aminoacid and low water content of the Porphyra. Also, high NO3 content may be important to improve the bacterial flora in the animals, which in turn may favor more efficient digestion. Changes in the composition of Porphyra, however, can occur rapidly due to environmental conditions decreasing the nutritional value of the plant. Short term N pulse fertilization were performed on P. perforata in order to evaluate the feasibility to increase its nutritional value. Enrichment was performed under low light conditions (<5 ,E m -2 s -1) to inhibit growth and promote higher N enrichment per unit of biomass. Tissue N in the form of NO3, NH4 and total organic N were measured, after 3,6,12 and 24 hrs, in tissue exposed to 500 ,M of N. Results indicated a rapid N tissue enrichment particularly in the form of NO3. Nitrate accumulation occurs continuously, up to 24 hrs. Total organic N is maximum after 12 hrs and tends to decrease after that. Fertilization with NH4 promotes NO3 accumulation. These results suggest the feasibility to improve the nutritional value of P. perforata by short-term pulse fertilization. The capacity of this species to uptake NH4 under low light conditions (similar to those use in abalone culturing) makes it also ideal for integrated aquaculture. [source] Where temperate meets tropical: multi-factorial effects of elevated CO2, nitrogen enrichment, and competition on a mangrove-salt marsh communityGLOBAL CHANGE BIOLOGY, Issue 5 2008KAREN L. McKEE Abstract Our understanding of how elevated CO2 and interactions with other factors will affect coastal plant communities is limited. Such information is particularly needed for transitional communities where major vegetation types converge. Tropical mangroves (Avicennia germinans) intergrade with temperate salt marshes (Spartina alterniflora) in the northern Gulf of Mexico, and this transitional community represents an important experimental system to test hypotheses about global change impacts on critical ecosystems. We examined the responses of A. germinans (C3) and S. alterniflora (C4), grown in monoculture and mixture in mesocosms for 18 months, to interactive effects of atmospheric CO2 and pore water nitrogen (N) concentrations typical of these marshes. A. germinans, grown without competition from S. alterniflora, increased final biomass (35%) under elevated CO2 treatment and higher N availability. Growth of A. germinans was severely curtailed, however, when grown in mixture with S. alterniflora, and enrichment with CO2 and N could not reverse this growth suppression. A field experiment using mangrove seedlings produced by CO2 - and N-enriched trees confirmed that competition from S. alterniflora suppressed growth under natural conditions and further showed that herbivory greatly reduced survival of all seedlings. Thus, mangroves will not supplant marsh vegetation due to elevated CO2 alone, but instead will require changes in climate, environmental stress, or disturbance to alter the competitive balance between these species. However, where competition and herbivory are low, elevated CO2 may accelerate mangrove transition from the seedling to sapling stage and also increase above- and belowground production of existing mangrove stands, particularly in combination with higher soil N. [source] Atmospheric nitrogen deposition has caused nitrogen enrichment and eutrophication of lakes in the northern hemisphereGLOBAL CHANGE BIOLOGY, Issue 4 2006ANN-KRISTIN BERGSTRÖM Abstract We compiled chemical data and phytoplankton biomass (PB) data (chlorophyll a) from unproductive lakes in 42 different regions in Europe and North America, and compared these data to inorganic nitrogen (N) deposition over these regions. We demonstrate that increased deposition of inorganic N over large areas of Europe and North America has caused elevated concentrations of inorganic N in lakes. In addition, the unproductive lakes in high N deposition areas had clearly higher PB relative to the total phosphorus (P) concentrations illustrating that the elevated inorganic N concentrations has resulted in eutrophication and increased biomass of phytoplankton. The eutrophication caused by inorganic N deposition indicates that PB yield in a majority of lakes in the northern hemisphere is (was) limited by N in their natural state. We, therefore, suggest that P limitation largely concerns lakes where the balance between N and P has been changed because of increased anthropogenic input of N. [source] Beyond biomass: measuring the effects of community-level nitrogen enrichment on floral traits, pollinator visitation and plant reproductionJOURNAL OF ECOLOGY, Issue 3 2010Laura A. Burkle Summary 1.,Nitrogen (N) limits primary productivity in many systems and can have dramatic effects on plant,herbivore interactions, but its effects on mutualistic interactions at the community level are not well-understood. The reproduction of many plants depends on both soil N and pollination, and N may affect floral traits, such as flower number or size, which are important for pollinator attraction to plant individuals and communities. 2.,Thus, N may influence plant biomass and reproduction directly as well as indirectly via changes in pollination. The degree to which the effects of N enrichment scale from plant individuals to assemblages through emerging community-level changes in species interactions, like pollination, is relatively unknown. 3.,For 4 years, we tested how N addition to subalpine plant assemblages in Colorado, USA, affected primary productivity and species diversity, floral traits and plant,pollinator interactions, and components of female and male plant reproduction. 4.,At the community level, we found that high-N addition favoured the biomass and seed production of grasses, whereas low-N addition promoted forb growth, flower production and pollinator visitation. However, using a pollen supplementation experiment, we found no evidence that N addition altered patterns of pollen limitation of seed production. Pollinators distributed themselves evenly across floral resources such that per-flower visitation rate did not differ among N treatments. Thus, individual plants did not incur any extra benefit or cost from community-level changes in plant,pollinator interactions that resulted from N enrichment, and the effects of N on forb reproduction were direct. 5.,Synthesis. Understanding how mutualistic and antagonistic species interactions influence individual and community responses to abiotic resources may provide insight to the dominant forces structuring communities and is especially important in the context of predicting the effects of environmental change. In this case, the direct effects of N addition on plants were stronger than the indirect effects mediated through plant,pollinator interactions, thus supporting the concept of bottom-up resource limitation controlling plant response. [source] | ||||||||||