Jellyfish

Pesticides have played a key role in the development and management of Australian landscapes over the last century. However, some management practices combined with non-target effects from pesticides and long-term persistence in the environment have impacted downstream freshwater and marine communities. Historically, monitoring of these effects on the GBR has been challenged by a range of issues including wide spatial and temporal variation in pesticide chemistries and variable catchment and land-use loads. This is further complicated by seasonal influences that drive pulse exposures. These influences combined with the topographic complexity of the reef shelf and associated variation in water movement and mixing, pesticide evolution, mixture synergies in both the water column and sediments, and very low biological-effect-concentrations make pesticide monitoring a challenge. Time-integrated measures of pesticide levels are needed to provide more accurate estimates of the potential impacts. Cassiopea jellyfish are a sensitive indicator of water quality and are found across a wide range of environments on the northeastern coast of Australia from river-mouth estuaries to seagrass meadows and coral reef lagoons. This genus hosts a symbiotic dinoflagellate algae and has been put forward as a model organism for understanding wider host-symbiont responses to environmental change. In this respect, it serves as a surrogate for reef-building corals. The adult medusae of Cassiopea spp. have an epibenthic habit and tend to remain within a relatively small range. They can influence local water mixing and bioturbation patterns, and associated bioaccumulation of environmental markers can discriminate very low concentrations of potential toxicants in both the water column and sediments. These factors suggest that the spatial distribution of pesticides and pesticide metabolites across the GBR and their risks to key biota can be mapped by Cassiopea sp. at both small and large scales.