Aquatic Ecosystem Rehabilitation through Modelling

“Aquatic Ecological rehabilitation is an act of repairing or replacing primary aquatic ecosystem structure to its original state for the maintenance of ecological integrity of degraded habitats for the benefit of people and environment.”

Environment has severely impacted by human intervention through hydrological modifications (dams, weirs and canals), inputting pollutant loads and introducing invasive species. From the theory of evolution, survival of the fittest plays an important role in declining intolerant species population. A tolerant species can replace an intolerant species, including native species with changing the ecosystem. In such case, aquatic rehabilitation helps in recovering the riverine degraded condition and maintaining its resilience. Suitable habitat maintenance is very important for the recovery of aquatic ecosystems and maintaining species survival and diversity.

Several river habitat restoration projects are running to conserve threatened and endangered species. The success of any habitat restoration is defined by understanding the response of aquatic species to hydrologic, physical and chemical environments. Periodical assessment of the restoration progress is required to increase its success. With increasing research and understanding, habitat restoration process is not limited to a specific species and recruitment index, it is now extended to a multidisciplinary knowledge of biology, hydrology and ecology. To implement river rehabilitation in a better way, this requires a better connection of substantial scientific expertise, habitat type and complexity along with fish biological interaction. One such example is to monitor competition and predation for the improvement of their rehabilitation potential.

To simplify the complex approach, several scientists from multiple Universities and institutes in China, proposed an effective computing method (modelling approach) assessment of rehabilitation potential, based on the dominant fish species to their habitat environment. In this paper, an assessment model for restoration potential was prepared. This model is successfully linked to hydrological, physical and chemical habitat factors to fish assemblage. The fish assemblage attributes are collected from monitoring datasets on hydrology, water quality and fish assemblages at a total 144 sites in Jinan city, China (Fig.1).

Fig.1 Study site (Zhao et al., 2015)

Total 5084 fish were sampled and tested. Three sub-models were developed to study the spatial heterogeneity of the restoration potential of fish assemblages. The fish assemblages were based on gradient methods of habitat suitability index and ecological niche models. These models were validated by the two habitat parameters: river width and transparency. Where fish assemblages were positively influenced by the river width and negatively influenced by the transparency.

This model is based on a relatively simple theory of habitat gradient, habitat suitability and ecological niche, which requires only basic fish related information and expertise (like, fish assemblage numbers and fish species biomass). After recording fish attributes, model can help in linking habitat and environmental gradients to determine dominant species. From here a key habitat factor can be selected by the user and rehabilitation potential of the fish community can be assessed. The fig.2 is modified from the original article to provide better understanding.

Such models can help analysing rehabilitation potential and improve the success of aquatic ecosystem restoration by successfully linking hydrological, physical and chemical environment to fish assemblage attributes. Identification of environmental pressure gradients (most effective environmental factor) is key to restoration success. Selection of suitable indicators for habitat quality assessment before, during and after restoration is required to follow habitat rehabilitation potential. These types of models can help in identifying fish species responses even before beginning such rehabilitation projects. This can help in cost reduction by calculating results before applying them in field study and identify a focusing aspect to achieve success.

Reference:

Zhao, C.S., Yang, S.T., Liu, C.M., Dou, T.W., Yang, Z.L., Yang, Z.Y., Liu, X.L., Xiang, H., Nie, S.Y., Zhang, J.L., Mitrovic, S.M., Yu, Q., Lim, R.P. Linking hydrologic, physical and chemical habitat environments for the potential assessment of fish community rehabilitation in a developing city. Journal of Hydrology 523 (2015) 384–397.

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