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Effects of Global Change on Aquatic Lower Trophic Levels of Coastal South West Atlantic Ocean Environments
Published in Donat-P. Häder, Kunshan Gao, Aquatic Ecosystems in a Changing Climate, 2018
Macarena S. Valiñas, Virginia E. Villafañe, E. Walter Helbling
Several studies have also shown the influence of increased nutrient inputs on coastal phytoplankton of the SW Atlantic, either due to anthropogenic activity (domestic or industrial sewage) or increased riverine runoff, as well as aeolian transport due to changes in wind patterns. In coastal zones of Pernambuco in Brazil, Pereira et al. (2005) reported the dominance of some particular taxa (e.g., Gyrosigma balticum and Bacillaria paxillifera), low richness of species, diversity and equitability as indicators of eutrophication. In the hypereutrophic Recife harbor, Guenther et al. (2015) reported that phytoplankton production rates were seven times higher at present as compared to 20 years ago, and this was also tied to changes in size structure towards nanoplankton species. Also eutrophication was reported in the Guanabara Bay, through measurements of particulate and dissolved organic matter that were well above the average concentrations found in other less impacted coastal zones (Cotovicz Jr. et al. 2018). Studies carried out in Argentina also reported eutrophication effects on phytoplankton dynamics and structure. In this regard, López Abbate et al. (2015), in a two-year survey in two sites of the Bahía Blanca estuary with contrasting anthropogenic impact, found higher phytoplankton abundance dominated by smaller-sized, non-siliceous species in areas under severe eutrophication; also sewage pollution caused significant effects in the ecological stoichiometry, i.e., N and P excess with respect to Si, with potential consequences on the food web dynamics. Finally, in the Río de la Plata estuary, García and Bonel (2014) found signs of high eutrophication, i.e., with high picoplankton (chlorophytes and cyanobacteria) concentrations in the most polluted areas.
Effects of N and P fertilization on the biomass and ecological stoichiometric characteristics of Agropyron michnoi in sandy grasslands
Published in Chemistry and Ecology, 2020
Xiaoming Jin, Lixia Yang, Xiaogang Yang, Qingxin Guan, Zhansong Ma, Jing Pan, Xiaoyu Jiang, Haowen Hou
Ecological stoichiometry balances energy and multiple chemical elements and unifies the theories of various ecological disciplines; thus, it greatly advances our understanding of ecosystem dynamics and processes [16]. Carbon (C), N, and P, the three most basic elements within organisms, play crucial roles in biology [17]. N and P, the main elements limiting plant growth, affect plant productivity [18], photosynthesis rates [19] and other ecosystem functions [20]. The amount of N and P in plant tissues, especially in the leaves, has been studied in abundance, and the N:P ratio is considered an important indicator of nutrient limitation within individual species as well as within an ecosystem [21, 22]. In wetland ecosystems, the leaf N:P ratio is <14 under N-limiting conditions and >16 under P-limiting conditions [23]. However, in grassland ecosystems, the threshold value of the leaf N:P ratio is <21 under N-limiting conditions and >23 under P-limiting conditions [24]. Therefore, the amount of N and P is influenced by various biotic and abiotic factors, such as habitat, functional group, and growth stage [21, 22]. It is not yet clear how the C, N, and P stoichiometry of plants changes in response to exogenous N and P fertilisers in sandy grasslands.