sea sponges in underwater caves in bulgaria, fauna of the black sea

black sea bulgaria fauna disidea animal benthal benthos bentos biofouling biological biology ecology exoskeleton filtration filtrations haliclona invertebrate invertebrates life marine nature organisms overgrown porifera saltwater sessile sponge sponges spongia water underwater world wild wildlife aqua colorful diving mediterranean scuba seaside spong spongea yellow zoological