Using eDNA to understand the impact of anthropogenic disturbance on tropical estuaries

Globally, estuaries are being subjected to an array of anthropogenic stressors, which are reshaping the communities and making them more susceptible to the introduction of non-indigenous species (NIS). The estuaries of Queensland’s Mackay-Whitsunday’s region are being exposed to high nutrient and pesticide loadings from intensive agriculture. Here we looked at the water column and sediment communities of four systems with varying levels of anthropogenic disturbance. To gain knowledge of community composition and the potential presence of NIS, DNA metabarcoding was used targeting two taxonomic groups; crustacea (16S mt rDNA) and metazoan (CO1). All systems were highly eutrophic at the time of sampling but only trace concentrations of pesticides were uncovered. The community composition showed to be distinct for each estuarine system. Differences in the crustacean water column communities showed to be mainly driven by dissolved oxygen (13.84%, P<0.001). While natural variation of metals and not anthropogenic inputs proved to drive variation in sediment communities for both crustacean and metazoan. This study highlights the potential of DNA metabarcoding as a powerful tool for biomonitoring of coastal systems and highlights the challenges of detecting ecological impacts within systems seasonally exposed to agricultural run-off.