Hi,
You might wish to note that of the sources you listed, only Borneman actually is a scientist doing research on corals. Sprung owns a fish store and produces supplements, Delbeek is a technician at a commercial aquarium and Knop sells supplements.
The state of the art is this... no scientist working on coral in nature is going to waste his/her time on such a question. The reason for this is that there is a large body of evidence (mostly in the marine pollution literature) that shows, as with virtually all marine animals, that at almost any level over those amounts found in natural sea water virtually all trace elements are poisonous. Consequently, nobody in this publish or perish world is going to waste their time reproving the obvious.
Additionally, most of the "trace elements" can not be tested for in reef tanks, and in most sea water mixes the amounts are excessive.
Here are a few references to get you started. If you are interested in this topic, you will want to spend some time at your local large university and search through the back issues of "Marine Pollution Bulletin," "Environmental Toxicology," "Coral Reefs," and "Limnology and Oceanography." You will find a lot more than the few article listed below.
Alutoin, S., J. Boberg, M. Nyström, and M. Tedengren. 2001. Effects of the multiple stressors copper and reduced salinity on the metabolism of the hermatypic coral Porites lutea. Marine Environmental Researh 52: 289-299.
Breitburg, D. L., J. G. Sanders, C. C. Gilmour, C. A. Hatfield, R. W. Osman, G. F. Riedel, S. P. Seitzinger, and K. G. Sellner. 1999. Variability in responses to nutrients and trace elements and transmission of stressor effects through an estuarine food web. Limnology and Oceanography. 44: 837-863.
Carey, J. 1981. Nickel mining and refinery wastes in coral reef environs. Proceedings of the Fourth International Coral Reef Symposium, Australia. Volume 1. 137-146.
Cheung, S. G., K. K. Tai, C. K. Leung, and Y. M. Siu. 2002. Effects of heavy metals on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus (Powys). Marine Pollution Bulletin. In Press.
DiBacco, C. and L. A. Levin. 2000. Development and application of elemental fingerprinting to track the dispersal of marine invertebrate larvae. Limnology and Oceanography, 45: 871-880.
Gilbert, A. and H. E. Guzman. 2001. Bioindication potential of carbonic anhydrase activity in anemones and corals. Marine Pollution Bulletin. 42:742-744.
Goh, B. P. L. and L. M. Chou. 1992. Effect of low levels of zinc on zooxanthellae cells in culture. Proceedings of the Seventh International Coral Reef Symposium, Guam. Volume 1. 367-372.
Heyward, A. J. 1988. Inhibitory effects of copper and zinc sulphates on fertilization in corals. Proceedings of the Sixth International Coral Reef Symposium, Australia. Volume 2. 299-309.
Negri, A. P. and A. J. Heyward. 2001. Inhibition of coral fertilization and larval metamorphosis by tributyltin and copper. Marine Environment Research. 51:17- 27.