Research

• Inflows and trophic level responses: My research agenda is to explore the impact of river inflows and nutrient loadings on estuaries and bays, specifically their influence on phytoplankton productivity and dissolved oxygen concentration. The research involved a compilation of historical data for multiple bay systems in the Western Gulf of Mexico, statistics-guided mathematical model formulation, and numerical simulation analyses using a coupled biophysical model. For this project, I developed spatially discrete biophysical circulation models that enable the study of the relationship between freshwater inflows and bay ecosystem health with temperature and salinity-dependent model parameters. The research was funded by the Texas Commission on Environmental Quality.

• Invasive species control: We are working on developing a sustainable control strategy to promote the growth of herbivorous fish in partially protected MPAs (Marine Protected Areas) affected by invasive fish. Using a suitable control strategy, our goal was to maximize the harvesting yield in MPAs without compromising the herbivore fish stock. For this, we explored a couple of control strategies to investigate how the control strategy aimed at MPAs help in increasing the diversity and richness of herbivorous fish in the surrounding unprotected areas. With harvesting as a plausible control of invasive species, we studied intermittent harvesting strategies governed by Filippov’s system of ODEs with right-hand discontinuities, where the density of the herbivores was chosen as an index to make decisions on when to discontinue harvesting. We observed that harvesting adult invasive fish is more efficient in promoting the population growth of the herbivorous fish compared to that of its juvenile species. Furthermore, we studied the efficacy of selective intermittent harvesting in reducing the invasive fish population. We compare the revenues corresponding to the harvest policies based on maximum sustainable yield, maximum economic yield, and optimal sustainable yield for inferring an ecologically sustainable and economically viable harvesting policy. We also studied sex-selective harvesting strategies and investigate the long-term stability of the exploited fish population. We proposed an intervention strategy to address the harvesting policy in preventing the fish population collapse even in the presence of high harvesting effort. We investigated the optimal implementation of an autocidal TYC (Trojan Y Chromosome) strategy to find the minimum viable injection rate of feminized supermale invasive species together with the minimum continuous supply time to eradicate the invasive species. We also investigated the efficacy of a control strategy that mimics the TYC strategy by harvesting females whilst stocking males.

• Coral reef conservation: In my early research years, I introduced novel modelling approaches to study coral reef ecosystems under natural and anthropogenic stresses by developing appropriate strategies to monitor and control the shift of regime from a coral-dominated one to a macroalgae-dominated coral-reef ecosystem. Using the concept of basin stability, I have studied the changes in the ecosystem resilience to develop early warning signals designed to forecast a possible catastrophic shift of regime in coral reef ecosystems due to toxic seaweed, invasive predators, and overfishing. I have investigated the dynamics of detoxifying organisms in coral reefs in the presence of marine toxicity.

I have developed an effective biological control strategy to eliminate invasive fish from marine protected areas (MPAs). The study involved finding the efficacy and cost-effectiveness of introducing genetically reversed supermales into an invasive population impacting the MPA (as a form of biological control), which over time would skew the male-female ratio of the invasive population to a point that drives the local population to extinction. I used spatially explicit models to investigate the effectiveness of intermittent stage-specific harvesting policy in MPAs, where the management outcome is to promote the growth of native fishes in the adjoining fishing zones. Further, I have explored the effects of macroalgal allelopathy and microbial diseases in coral-macroalgal phase shifts. In my subsequent investigations, I explored the effects of allelopathy on the competition between plasmid-bearing and plasmid-free organisms for multiple complementary nutrients in a chemostat using mathematical modelling.

• Social-ecological modelling: I have been working on developing social-ecological coupled systems to identify the harvest-mediated changes in the regime that are not present in the ecological subsystem in isolation. The sudden changes in the systems can be identified by studying the nature of bifurcation due to the changes in some parameter values.