Sponges Revealed: A Synthesis of Their Overlooked Ecological Functions Within Aquatic Ecosystems

While sponges are the oldest still living multicellular animals on this planet and omnipresent within aquatic ecosystems, they have not been studied nearly as much compared to the recognized ecosystem drivers in coral reefs: corals, algae, and fish. We therefore want to take this opportunity to illustrate the diversity, functionality, and sheer survivability of these ancient animals. Beyond its multitude of external shapes and colors, sponges hold a unique internal aquiferous system. This system of afferent and efferent canals is intricately linked to supply its key function as a filter feeder. By filtering both particulate and dissolved material, sponges fill a niche in nutrient cycling. Moreover, the survivability of sponges is demonstrated in the variety of habitats it resides in; from freshwater canals to polar deep seas. In formerly uninhabitable environments, sponges can potentially create biodiversity hotspots by providing habitat complexity and shelter from predators. This review will give insight into the early life history, morphology, diet, and reproduction of sponges. Furthermore, it is imperative to consider their function as habitat facilitator, nutrient cycler, and, last but not the least, their potential for future pharmaceuticals. The emphasis in the proceedings has been specifically put on the role of sponges as nutrient cycler as they play a role in the three essential elements: carbon, nitrogen, and phosphorous. With all this in mind, it should be clear that even though sponges are relatively overlooked marine invertebrates, they should be studied similarly to corals and respected as a key ecosystem driver in novel and established environments.