Impact assessment of an invasive macrophyte community on ecosystem properties: A Mass Balance Approach for Chilika lagoon, India

Abstract

Phragmites karka (commonly known as Nala grass) is considered an invasive macrophyte, covering an area of 105.1 sq. km, hindering navigation and impacting the ecosystem functioning of Chilika Lagoon (1165 sq.km). The mass balanced models of three different scenarios of Chilika Lagoon were developed using Ecopath to assess the impact of the invasive macrophyte P. karka on the various ecological attributes of the ecosystem. The three different scenarios modelled were (1) a real-time scenario with 23 functional groups that includes P. karka as a group, (2) a virtual scenario with only 22 functional groups where the system is devoid of P. karka, and (3) a virtual scenario that has 22 groups but is devoid of the functional group seagrass and other macrophytes. The results of our study indicate that scenario-2, which is devoid of the macrophyte P. karka, was found to be a relatively mature and resilient ecosystem with the highest utilisation of primary production within the system. This scenario also possesses the highest overhead (67.47%) and Finn's cycling index (FCI) (4.226%) in comparison to the other two scenarios. The ecosystem indices showed a negative impact of P. karka on the trophic functioning of the Chilika Lagoon, which warrants an urgent need to remove the macrophyte to improve the resilience of the ecosystem.