Joint School Research Group Seminar, Wednesday, 14th September
Nutrient enrichment from river discharge in the Great Barrier Reef and consequent effects: Loss of resilience for the future against a changing climate
Presented by Jon Brodie (TropWater, James Cook University, Townsville, Australia)
On Wednesday, 14th September 2016, Clayton Room, 1 - 2 pm
The degree of increased discharge of nitrogen and phosphorus from Great Barrier Reef (GBR) rivers, associated with agricultural development of the catchments in the last 200 years, varies greatly between the 35 individual major rivers. Changes to discharge in the far northern section of the GBR have been minimal while changes in the central and southern GBR have been of the order of 2 – 5 times increases in both nitrogen and phosphorus. Thus the degree of increased nutrient loading of communities such as coral reefs and seagrass meadows also varies spatially to a great degree, both from north (low loading) to central and south (high loading) as well as cross-shelf with higher loading to inshore systems and progressively less loading as distance from the coast and river mouths increase. The impacts of increased nutrient loading in the GBR include increased outbreaks of the crown of thorns starfish, a predator on coral; increased susceptibility of coral to bleaching in nutrient enriched conditions; decreased water clarity associated with increased suspended particulate matter and subsequent effects on phototrophic organisms such as coral and seagrass; and changes in the relationship between coral and macroalgae on coral reefs. Overall these impacts are manifest in the overall status of the ecosystems of the GBR with coral, seagrass and dugongs (which feed on seagrass) being in best condition in the far northern region of the GBR, including the Torres Strait section, but in poor condition in the central and southern GBR. While other factors such as climate change are also implicated in these differences it is well established that nutrient enrichment plays a major role. While a limited amount of progress has been made in reducing sediment and nutrient loadings at a considerable expense it is now clear that not enough load reduction has been made or is likely to be made to provide any significant amount of resilience for the GBR against the current climate change impacts occurring or those certain to occur in the next few decades.
All school research groups welcome to attend.