Definition. A fibroblast is a cell that manufactures and maintains connective tissue, the structural framework that supports the organs of all animals. Fibroblasts secrete fibrous proteins and ground substance, which together form the extracellular matrix that is the basis of connective tissue. fibroblast is a cell that manufactures and maintains connective tissue, the structural framework that supports the organs of all animals.
Therefore, there is very little chlorophyll in these tropical waters, keeping them clear. (As an aside, corals are symbioses where phytoplankton have evolved to survive in nutrient-poor tropical waters by living inside the bodies of the corals and obtaining nutrients directly from the waste products of the corals.
In the very clearest tropical waters the photic zone may extend to a depth of 600 meters, but a more typical value for the open ocean is 100 meters. In contrast, light typically penetrates the coastal waters in which we swim only to about 40 meters.