Assessing the effects of sediments and nutrients on coral reefs

There is an enormous literature on the effects of sediments and nutrients on reefs. Until recently, there were few clear guidelines that could easily be used by management to alleviate these stresses. Recent progress in our understanding of watershed dynamics has brought us much closer to being able to manage catchments so as to minimize sediment stress. Timing is everything — onset of sediment pulses, wave setup — and resuspension is key. There now exist a toolbox of techniques, some off-the-shelf and some still experimental, that should allow estimates of sediment and nutrient stress on reefs, not only in the present, but also retroactively. There is danger that much of this excellent work will have been in vain. Recent work on reef trajectories has indicated that it will be very difficult to sustain healthy reefs for more than a few decades from the present. Other recent work has shown that widespread reef extirpation was occurring before 1960, coincident with European occupation and development of the adjacent coastlines.