Global transcriptomic profiling in barramundi Lates calcarcifer from rivers impacted by differing agricultural land-uses

Most catchments discharging into the Great Barrier Reef (GBR) lagoon have elevated loads of suspended sediment, nutrients, and pesticides, including photosystem II inhibiting herbicides, associated with upstream agricultural land use. To investigate potential impacts of declining water quality on fish physiology, RNASeq was used to characterize and compare the hepatic transcriptomes of barramundi (Lates calcarifer) captured from two of these tropical river catchments in Queensland, Australia. The Daintree and Tully Rivers differ in upstream land uses, and sediment, nutrient and pesticide loads, with the area of agricultural land use and contaminant loads being lower in the Daintree. In fish collected from the Tully River, transcripts involved in fatty acid metabolism, amino acid metabolism, and citrate cycling were also more abundant, suggesting elevated circulating cortisol concentrations, whereas transcripts involved in immune responses were less abundant. Fish from the Tully also had an increased abundance of transcripts associated with xenobiotic metabolism. Previous laboratory-based studies observed similar patterns in fish and amphibians exposed to the agricultural herbicide atrazine. If these transcriptomic patterns are manifested at the whole organism level, the differences in water quality between the two rivers may alter fish growth and fitness.