Ecology and distribution of the sponge Aplysina aerophoba (Porifera, Demospongiae) in the Limski kanal (northern Adriatic Sea, Croatia)

The sponge Aplysina aerophoba Schmidt, 1862 (Demospongiae, Verongida, Aplysinidae) is one of the most common sponges in the Limski kanal. The family Aplysinidae Carter, 1875 is a potential source for natural bioactive products. The information about sponge distribution patterns and their dependence on light, depth, substrate and other factors could be very useful for in situ culture and can be utilized to improve in vitro maintenance conditions, because a sustainable growth has not yet been observed ex situ. A. aerophoba distribution along the Limski kanal has been studied on twelve locations on the northern and southern coastlines of a channel-like bay in the Istrian peninsula, Croatia. Several ecological gradients are present in the bay, making it a suitable model habitat for the distribution of this sponge. The sponges have been found most commonly near the surface, with a decreasing trend in number and size of specimens towards the depth. A. aerophoba presence is dependent on suitable, stable hard substrate like rocks or rocky walls. An observed decrease of its abundance can be explained with shading, by rocky notches close to the water surface, by the presence of benthic competitors (mainly algae) or by high sedimentation which increases towards the eastern end of the bay.