The dynamics of a phytoplankton population growing in a chemostat under a periodic supply of nutrients is investigated with the model proposed by Droop. This model differs from the well-known Monod equations by incorporating nutrient storage by the cells. In spite of its nonlinearity and the time delays introduced by an internal nutrient pool, the model predicts a simple response to a periodic ...

A numerical model is developed to examine coastal groundwater processes in a sandy beach, including the effects of tidal fluctuations, saltwater intrusion into an aquifer, and dynamics in unsaturated layers. The simulation results indicate: 1) ‘Local circulation’ is clearly formed in the aquifer near the shoreline owing mainly to tidal oscillations. 2) The circulation induces a landward bending...

Phytoplankton populations and communities respond to nutrient inputs on time scales from days to weeks. This short-term variability is superimposed on the long-term seasonal, annual and interannual variability in estuarine biogeochemical cycling that together regulate food web dynamics and ecosystem responses to nutrient loadings. Quantifying this short-term variability within the context of lo...

The goal of the note is to document a method of solving nutrient dynamics in biogeochemical models. Specially it focuses on improving numerical solutions of biogeochemical models (specifically soil model) so that 1) negative nutrient concentrations are not simulated and 2) serial access (i.e. microbes have first access, then plants) to nutrients is not required by the different nutrient consume...

Predicting where state-changing thresholds lie can be inherently complex in ecosystems characterized by nonlinear dynamics. Unpacking the mechanisms underlying these transitions can help considerably reduce this unpredictability. We used empirical observations, field and laboratory experiments, and mathematical models to examine how differences in nutrient regimes mediate the capacity of macrop...

Eutrophication and hypoxia within aquatic systems are a serious international concern. Various management practices have been proposed to help alleviate nutrient loads transported to the Gulf of Mexico and other high-profile aquatic systems. The current study examined the nutrient mitigation capacity of a vegetated (V) and non-vegetated (NV) agricultural drainage ditch of similar size and landf...

The goal of the note is to document a method of solving nutrient dynamics in biogeochemical models. Specially it focuses on improving numerical solutions of biogeochemical models (specifically soil model) so that 1) negative nutrient concentrations are not simulated and 2) serial access (i.e. microbes have first access, then plants) to nutrients is not required by the different nutrient consume...

Mangrove forests are characterized by distinctive tree-height gradients that reflect complex spatial, within-stand differences in environmental factors, including nutrient dynamics, salinity, and tidal inundation, across narrow gradients. To determine patterns of nutrient limitation and the effects of nutrient availability on plant growth and within-stand nutrient dynamics, we used a factorial ...

Nutrients and phytoplankton dynamics in the traditional fishing grounds off Tiruchendur coast, Gulf of Mannar, India revealed a clear seasonal trend influenced by prevailing monsoon system in east coast of India. A total of 73 species of phytoplankton were identified from the fishing grounds, revealed higher abundance in summer months compared to other seasons. Among the three stations, maximum...

Eutrophication and contamination by toxic organic pollutants are the major problems in water quality management. Despite the fact that both problems have been subjected to extensive research and modelling, they have traditionally been treated separately. Because the models used are single-issue models, many interactions between nutrient cycles and organic contaminant fate and effect are missed....