'Dredging stirs up a lot of mud, which takes time to settle. Nature also does this on a grander scale, but not continuously.' Wrong. Nature does it differently and it's not even the same thing. What nature cannot do - a suction cutter does.
'The outer reef is not at risk from dredging.' Is that so...
'If it was, then natural river outflows would have stopped it from ever forming in the first place.' Scientists have spent centuries trying to understand anthropogenic impacts on ecosystems - the monitoring of sediment discharge to reef ecosystems being no exception. It appears that we can discern an impact to the reef associated with changed land-uses, higher sediment loads and associated nutrient, pesticides, heavy metals runoff. Anything other than 'natural river outflows' might cause changes to the reef and that is indeed what many scientists have found.
'Inshore soft corals are much more tolerant of algae, and high nutrients. They are mostly phototrophs, so turbidity for too long blocks sunlight. Just like plants.' Every coral has different requirements - that some are more or less tolerant to changes in their environment (such as nutrient input) is not surprising.
'Sea grass and mangroves require plenty of nutrient. Thus you normally find dugongs in fairly turbid water. Mangroves are typically plentiful around river deltas.' Mangroves act to filter the water and stabilise sediments. They occur in locations of sediment accretion. The presence of mangroves or the fact that dugong live in marine environments characterised by dynamic coastal processes seems irrelevant.
Are you trying to claim that Dugongs are always exposed to waters that are highly turbid 'with anoxic contaminants such as ASS' which might typically be mobilised by dredging operations? Turbidity resulting from natural processes and dredging operations are not equivalent by any stretch.
To understand why ASS (Acid Sulfate Soil) and mobilisation of anoxic sediment is a risk to marine life - you need to consider sediment biogeochemistry. One important consideration is to note the prevalence of PASS (Potential Acid-sulfate soils) along east coast Australia.
Sediment biogeochemistry has been well described in the literature with respect to various underlying /parent geology and systems, and indeed much research has been undertaken around Port Curtis by the (former) Coastal CRC.
'Fertilizer runoff from farms needs to be looked at more competently ...... AIMS and JCU have neither the money nor the competence to perform such complex surveys over such large areas.' I cannot disagree with the premise that more research needs to be undertaken, or that such research (organisations committed to such research) is grossly underfunded.
