How does agricultural pollution affect estuarine health in the United Kingdom?by Sven Mellaza and Matia Pavkovic
Published by the October 4, 2021 on 4:39 PM
Estuaries are among the most productive ecosystems on the planet. These habitats deliver many services to humankind. They are characterized by wide ranges of water salinity, currents power and turbidity. To their natural stressors are added human disturbances that affect the natural system.
The rivers, from their sources to the sea, follow a long path through land fields. In a period of important rainfall, a large part of the land pollution defined by Nitrates and Phosphates is collected by the rivers and transported to estuaries. Consequently, the enrichment of the system modifies the relation equilibrium in the food chain; a rich and complex link between the organisms is the base of a healthy resilient ecosystem. The management application is crucial, so estuarine ecosystems can continue to deliver services and host rich life diversity.
Impact analyses of the pollution on the ecosystem
In this study, the scientist aimed to asses estuarine health by considering the relation between all the organisms. They have analyzed two estuaries systems from the United Kingdom. Tamara estuary is a medium-size complex located on the south-west coast of England; it stretches from Gunnislake weir to Plymouth sound. The second estuary, Eden, is smaller compare to the first one. It is positioned between the village of Guardbrige and the town of St Andrews on the East coast of Scotland.
Since the 90’s, the two ecosystems have experienced major nutrient enrichment from the arable and livestock production. This pollution led to the ecosystem “eutrophication”, a biological phenomenon that can cause an increase of algal bloom and a decrease of oxygen concentration in habitats.
For this research, ecologists are using mathematical software called “Ecopath model”. The model is a widely used tool to identify and quantify major energy flow in the ecosystem, to visualize the important interaction between species, evaluate pollution and climate changes in aquatic ecosystems. This approach allows them to examine systems in their entirety to adjust management application.
The aim of this study is to analyze and compare food network structure of these two estuaries at different historical period of nutrient concentration. The results shows that Tamar estuary is 25% more active than Eden estuary in periods of high nutrients concentrations. The activity is defined by the number of matters flowing in the system. The scientists explain here the difference by the greater size and greater freshwater inputs from the rivers in Tamar estuary. The second indicator was the total biomass of the estuary. The productivity of the system decreases with the reduction of nutrients enrichment. Primary producer’s growth is stimulated by the extra nutriments, which improve their development and finally impact the upper trophic levels.
During pollution event, flow of nutrients increases, leading to degradation of the food-chain organization and structure. In addition, wider the estuaries are, slower it recovers from perturbations, especially looking at the trophic structure.
The Ecopath, Ecosim and Ecospace models are tools primely used to evaluate ecosystem impact of fisheries (Pauly et al. 2000). As it gets popular, these models are useful to evaluate trophic systems like estuaries. These well-known models can be useful to predict and analyze the effects of actual global changing. Nevertheless, a bunch of other models exist and are used to analyze trophic system like Bayesian-mixing model. Using different tools to study the same problematic permit comparison and can lead to different approaches.
