As pointed out above nutrients in reefs ssytems is a very complicated issue. I've always thought there's stuff we can't test for and chasing research done on reefs has helped quantify just how little we can actually test for as far as basic nutrients: Total carbon which includes Particulate, Dissolved Organic and Dissolved Inorganic (POC, DOC and DIC). Total Nitrogen which includes Particulate, Dissolved Organic and Dissolved Inorganic (PON, DON and DIN). Total Phosphorus which includes Particulate, Dissolved Organic and Dissolved Inorganic (POP, DOP and DIP). It's only the inorganic forms we can easily test for.
Long ago the assumption was made based only on testing for DIN and DIP that reefs systems are "nutrient deserts" and the idea we need to keep nutrients low became dogma. Unfortunately this was a very simplistic view and is best said by Charles Delbeek "Our crystal-clear aquaria do not come close to the nutrient loads that swirl around natural reefs. And so when we create low-nutrient water conditions, we still have to deal with the rest of a much more complex puzzle. Much like those who run their aquarium water temperature close to the thermal maximums of corals walk a narrow tight rope, I can't help but think that low-nutrient aquariums may be headed down a similar path." Charles Delbeck, Coral Nov/Dec 2010, pg 127
Over a decade ago research done by various researchers showing how complex and critical the nutrient web is on reef ssystems started filtering down to the hobbyest forums and reefers. This research show that we are dealing with species specific responses to feeding and levels eihter too high or too low can be critical for corals to thrive and compete with algae.
In particular, a long term research project at Southhampton University in England with coral maintianed in a reef system with typical filtration methods and mainteneance found a threshold level of .03 mg/l for PO4 (DIP) to prevent a phosphorus deficiency in corals. It is true corals are utilizing POP, DOP and DIP and as pointed out above a system may have enough and the corals in the system may be happy utilizing stuff we can't test for but not having any testable level can lead to coral death when growth or a stress event depletes what's available. What few aqauarists seem to be aware of is corals store phospholipids. Maintianing corals in low nutrient environments may prevent them from having enough to deal with stress events or competition from other corals and organisms weakening their immune systems leading to disease and death.
I realize this is a huge data bomb but here's links you may find informative;
"Coral Reefs in the Microbial Seas" This video compliments Rohwer's book of the same title (Paper back is ~$20, Kindle is ~$10), both deal with the conflicting roles of the different types of DOC in reef ecosystems. While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems
Changing Seas - Mysterious Microbes
Microbial view of Coral Decline
Nitrogen cycling in hte coral holobiont
BActeria and Sponges
Maintenance of Coral Reef Health (refferences at the end)
Optical Feedback Loop in Colorful Coral Bleaching
Richard Ross What's up with phosphate"
Phosphate Deficiency:
Nutrient enrichment can increase the susceptibility of reef corals to bleaching:
Increased dissolved inorganic nitrogen (DIN) concentrations in sea water have been linked to a reduction of the temperature threshold at which corals bleach, however, the mechanism underlying this change is not known. This phenomenon is now explained in terms of increased phosphatase activities...
www.nature.com
Ultrastructural Biomarkers in Symbiotic Algae Reflect the Availability of Dissolved Inorganic Nutrients and Particulate Food to the Reef Coral Holobiont:
Reef building corals associated with symbiotic algae (zooxanthellae) can access environmental nutrients from different sources, most significantly via the up...
www.frontiersin.org
Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates
Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with din…
www.sciencedirect.com
Effects of phosphate on growth and skeletal density in the scleractinian coral Acropora muricata: A controlled experimental approach
Phosphate contamination can negatively affect corals, modifying growth rates, skeletal density, reproduction, mortality, and zooxanthellae. We determi…
www.sciencedirect.com
High phosphate uptake requirements of the scleractinian coral Stylophora pistillata
SUMMARYSeveral untested aspects of the regulation of inorganic nutrient uptake were examined using nutrient depletion experiments with the symbiotic coral Stylophora pistillata. The total inhibition of phosphate uptake in artificial seawater lacking sodium indicates the involvement of a...
jeb.biologists.org
Phosphorus metabolism of reef organisms with algal symbionts
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therichross.com
Sponge symbionts and the marine P cycle
Marine sponges are ubiquitous colonizers of shallow, clear-water environments in the oceans (1, 2). Sponges have emerged as significant mediators of biogeochemical fluxes in coastal zones by virtue of respiring organic matter and facilitating both the consumption and release of nutrients (3, 4)...
www.pnas.org
Phosphorus sequestration in the form of polyphosphate by microbial symbionts in marine sponges
Coral reefs are highly productive ecosystems that raise a conundrum called “Darwin’s paradox”: How can high production flourish in low-nutrient conditions? We show here that in three abundant Caribbean sponges, the granules that have been commonly observed in sponge tissue for decades are...
www.pnas.org
What a great help!
