The basic biology of the sponge, outlined in this blog, demonstrates the unique nature of this animal. Sponges function as ecosystem engineers and tend to enhance the biodiversity of the surrounding area. As they are capable of colonising on many types of substrate, they can provide hard substrate in an otherwise sediment dominated environment. In this respect, deep-sea sponge communities have been described as oases. They facilitate the survival of many organisms by acting as an attachment site or as a refuge from predators. Sponges are also a source of food, albeit a toxic one for many organisms. Case studies have shown that the presence of sponges can extend the known depth ranges for deep-sea life.
Demospongia and Hexactinellidae are the most abundant types of sponge in the deep sea. Living at these abyssal depths involves challenges such as lack of light, low food levels and unpredictable water flow. To cope, some sponges have an alternative feeding strategy such as the carnivorous sponge Chondrocladia lyra. Glass sponge species, on the other hand, have adopted passive feeding which is extremely useful when water flow is low and active feeding is inefficient. This is seen in the Hyalonema sp. which bends under the influence of water flow to maximise efficient feeding. A characteristic that enables this is the bilateral symmetry of glass sponges which is often absent in Demospongia. Another adaptation of these glass sponges is their spicules that provide increased structural support such as in the Venus flower-basked (Euplectella).
Although this environment seems harsh when compared to shallower depths, the adaptations possessed by glass sponges allow them to thrive. This consequently facilitates a variety of other organisms that rely on sponge communities. The idea of this environment as “extreme” depends on point of view. Deep-sea sponges have adaptations that ameliorate the stresses of this environment, making it seem not so extreme after all.