Marine lakes in Indonesia: understanding shifts in biodiversity and food webs in tropical coastal ecosystems under increasing water temperature and terrestrial influence.

A major challenge in marine science is understanding how marine organisms of tropical coastal ecosystems will respond to environmental disruptions caused by increasing seawater temperature and high terrestrial effluent. Those elevated disturbance in tropical coastal ecosystems can lead to a decline in coral cover. Reduced coral coverage can result in a shift from coral dominated states to non-coral benthic group dominated states in reef ecosystems. Consequently, this may reduce biodiversity and disrupt interactions among various species within the ecosystem. Such disruptions can also impact the energy transfer between trophic levels via food chains and affect the structure of food webs within these ecosystems. A decrease in coral-dominated states in coral reef ecosystems can lead to lower diversity and, subsequently, less complex food web structures. These phenomena can harm fisheries, coastal protection, and other ecosystem services. I used marine lakes as model systems to understand the impact of changing environmental conditions on tropical coastal ecosystems. Marine lakes, small landlocked bodies of marine water, represent natural settings for various predicted environmental scenarios, including increased water temperature and low water quality. They also provide a platform for testing the Island Biogeography Theory's influence on biodiversity patterns. Island Biogeography Theory states that the closer the distance of the island from the mainland (species pool) resulting in a higher immigration rate, and the larger the size of the island due to more resources and space for species to live, resulting in lower extinction rate. This doctoral thesis investigates the potential impacts of increasing temperatures and terrestrial influences on the biological diversity, benthic community structure, and food web dynamics of tropical coastal ecosystems. Overall, the proposed PhD project will contribute to scientific knowledge on marine biodiversity and species community responses to projected future environmental conditions.