Madeline McKenzie
Cassiopea sp. as biomonitors of waters contaminated by herbicides/insecticides
My PhD, aims to investigate upside-down jellyfish, Cassiopea spp., as a model organism in a dynamic environment. This jellyfish is a sedentary benthic scyphozoan, and is particularly interesting because it has photosynthetic zooxanthellae in its tissues, similar to corals. These endosymbionts are the reason why they exhibit their ‘upside-down’ behaviour – they rest with their exumbrella against the substrate with their oral arms exposed to the light at the surface. The light allows the endosymbionts to perform their autotrophic duties, while the jellyfish’s pulse behaviour creates currents over its oral arms, facilitating heterotrophic feeding. They reside in shallow coastal marine systems in tropical and subtropical regions throughout the world. These systems are subject to various influences, such as terrestrial, riverine and tidal, and anthropogenic impacts. I plan to investigate the influence that certain anthropogenic contaminants, most deemed ‘contaminants of emerging concern’, have on Cassiopea spp. and their endosymbionts. Jellyfish will be exposed to xenobiotics (glyphosate, hydrocarbons, and microplastics) in isolation and as ‘cocktails’ in a series of field and laboratory experiments. Jellyfish have been shown to play an important role in inorganic nutrient recycling, and Cassiopea spp. in particular have been found to influence benthic oxygen and nutrient dynamics by their pulse behaviour. During my PhD I also plan to further explore this behaviour by investigating if it can also resuspend xenobiotics that have settled in the sediment, and if so, what influence this has on concentrations of xenobiotics in the water column.