crashfrog, I find it interesting that most of those posting apparently doesn't feel nutrients are needed for corals, perhaps true but the food source, zooplankton growth is benefited, and while sunlight might not be needed for corals the food source needs sunlight, so depth affects their growth, that sunlight is needed for zooplanktons to grow, (this is the food source for the planktons for your corals to feed on, etc...)
I always thought that iron salts, aluminum salts and other factors in sea water salts is why there is no varves in the oceans sediments, and responsible for the silt coagulating so you don't have the silt layers, with this problem of silt affecting corals, unless of course massive clear cuttings, causing excess soil erosion, or excess herbicides in the runoff carrying over into the nutrient washed by the tides into the coral reefs, which could kill those fragile corals, the zooplanktons or both, etc...
P.S. I have no problem that the massive killoff of your Great Barrier Reef that sank 4,350 years ago, could of been killed off by the massive amounts of silts in the biblical flood waters, and only find it interesting that scientists admit the seas lowered, supports the hydro-plate theory, psalms 104:8, the oceans settling, the waters flowing to the settled oceans levels, etc...
Zooplankton
http://www.chesapeakebay.net/info/plankton.cfm
Zooplankton are planktonic animals that range in size from microscopic rotifers to macroscopic jellyfish. Their distribution within the Chesapeake Bay is governed by salinity, temperature and food availability. The smallest zooplankton can be characterized as recyclers of water-column nutrients and often "are closely tied to measures of (nutrient enrichment"). Larger zooplankton are important food for forage fish species and larval stages of all fish. They also link the primary producers (phytoplankton) with larger or higher trophic-level organisms. The zooplankton community is composed of both primary consumers, which eat phytoplankton, and secondary consumers, which feed on other zooplankton.