Trophic functioning of a small, anthropogenically disturbed, tropical estuary

Area of Science:

• Ecosystem modeling
• Estuarine ecology
• Environmental science

Background:

• The Poonthura Estuary, a small estuary on India's southwest coast, faces significant anthropogenic impacts.
• Understanding the ecosystem's health and functioning is crucial for its conservation.

Purpose of the Study:

• To construct a trophic model for the Poonthura Estuary.
• To assess the ecosystem's health and functioning using ecological network analysis and ecosystem health indices.
• To identify key ecological groups and compare the estuary's trophic characteristics with other global estuaries.

Main Methods:

• Ecopath with Ecosim (EwE) software was used for trophic modeling based on data from 2016-2020.
• Ecological Network Analysis (ENA) and ecosystem health indices were employed to evaluate system structure and function.
• Key ecological parameters such as total system throughput, ascendancy, Finn's cycling index, and eco-exergy were calculated.

Main Results:

• The estuary exhibited low total system throughput, low ascendancy, high Finn's cycling index, low primary production/biomass, high mean transfer efficiency, and low eco-exergy.
• These indices indicated an immature, disorganized, and unhealthy ecosystem.
• A primary production/respiration ratio of 0.46 suggested significant organic pollution, with small benthic carnivores identified as keystone groups.

Conclusions:

• The Poonthura Estuary's ecological structure and functioning are severely impaired by anthropogenic stressors.
• The estuary's trophic functioning and food web structure differ from other estuaries with similar physical characteristics.
• This study provides a scientific basis for the management, monitoring, and restoration of the Poonthura Estuary and similar small, impacted estuaries worldwide.