Morphological growth response of Stylophora Pistillata to in-situ manipulations of light intensity and water flow regime

Morphological and physiological phenotypic plasticity of Stylophora pistillata in response to environmental changes was studied, with the objective of evaluating the impact of light and water flow as environmental factors. An in-situ artificial manipulation of combined light intensity and water flow was conducted, and the responses of several colonies were followed, over a period of nine months, documenting changes in colony architecture and zooxanthellae attributes. The results suggest the existence of a light threshold level, above which light is sufficient for fulfilling the association's energy needs and below which water flow becomes more crucial for attaining resources. S. pistillata exhibited phenotypic plasticity, with a strong dependence on light intensity. A conceptual model explaining the main patterns of morphological change in response to different combinations of the two factors is proposed. The suggested model is based on the idea that morphology is not intended to serve as an a priori optimizer of the hermatypic organism's performance in a given environment, but rather reflects an a posteriori response of the symbiotic association's architecture, mediated by its physiological response, to availability of resources and their gradients.