Last weekend I was asked to help out with a film crew who needed footage for two different documentaries on Howe Sound and Sponge Bioherms. A Bioherm is: An ancient organic reef of moundlike form built by a variety of marine invertebrates, including corals, echinoderms, gastropods, mollusks, and others; fossil calcareous algae are prominent in some bioherms. A structure built by similar organisms that is bedded but not moundlike is called a biostrome. Bioherms and biostromes occur in sedimentary rock strata of all geological ages, providing definitive information on paleoenvironments in the vicinity of their occurrence. [LINK]. For bioherm pics from Howe Sound, see my blog post on the Halkett Bioherm. In the case of Howe Sound, the bioherm's are silicate forms that are quite complex and there are only 4 that we can reach within recreational dive limits. This is why Glen built a drop cam and as you can see by the map to the left, the depth on the reef was at least 250ft. One of the reasons that these are so important is that they provide sheltered areas for rockfish nurseries. The hope is that one day these ancient forms are marine protected areas.