Thanks to the work of Dr. Jasper de Goeij we’ve gained significant insight in the role that sponges play in nutrient cycling on coral reefs. This knowledge has the potential to influence the way we think about filtration, carbon dosing and biodiversity in the aquarium.
It was previously thought that sponges fed predominantly on plankton. But [...]
Thanks to the work of Dr. Jasper de Goeij we’ve gained significant insight in the role that sponges play in nutrient cycling on coral reefs. This knowledge has the potential to influence the way we think about filtration, carbon dosing and biodiversity in the aquarium.
It was previously thought that sponges fed predominantly on plankton. But now, it has been found that the diet of certain cave sponges is largely reliant on dissolved organic carbon (DOC)–in some cases over 90%. Dr. de Goeij saw this large influx of organic carbon going into the sponges, but they were not growing very quickly. The obvious question remaining was where is it going?
It turns out the majority of organic carbon intake was driving cell turnover which was identified by discarded choanocytes–the cells in sponges that help pump water into the animal to then be filtered. Much like we shed skin cells, sponges do the same thing at a very fast rate. Using a unique detection test, de Goeji found the chanocytes of one species (Halisarca caerulea) divided in just 5.4 hours! This in turn provides a food source for other animals and corals that cannot directly utilize dissolved organic carbon. De Goeji said,
“Sponges filter their food out of the water. Because they live in a nutrient-poor environment, they sometimes have to pump 100 liters of water a day. This increases the chances of a sponge coming into contact with all kinds of viruses, bacteria and poisonous substances. These things can cause permanent damage. In order to avoid this, the sponge constantly rejuvenates its cells.”
Organic carbon is largely ignored as a food source by most corals we keep in aquaria. In fact, they release considerable amounts through mucus and slime–one study estimates that 20% of DOC found on the reefs is the result of expelled coral mucus. This coral slime helps drive the food web, feeding bacteria which are then consumed and consumed again. A missing link in this DOC food web now appears to be these carbon recycling sponges.
In aquariums we don’t have the luxury of balanced food webs–we generally export, permanently rather than tightly shift and recycle nutrients as we see in the ocean. However, sponges may provide a unique filtration and natural food source for reef keepers to implement. Over the past few years the idea of cyrptic refugia for sponges, rather than macro algae, has been explored and it may have its merit.
The cryptic, sponge dominated refugium of GBD contributor Leonardo den Breejen. Leonardo utilizes various organic carbon sources, which may be a link with the impressive sponge growth seen here.
Much still needs to be understood regarding the care and aquaculture of marine sponges. In the past these beautifully colored mesohyl animals were doomed in aquaria–but now I am left wondering, with the rise in popularity of organic carbon dosing (e.g. ZEOvit, Vodka, VSV or the latest solid form–NP Bio Pellets) are we better able to provide what may be a crucial food source for these animals? I truly don’t know, but it’s something to be explored.
For more information see:
De Goeij, J. M., De Kluijver, A., Van Duyl, F. C., Vacelet, J., Wijffels, R. H., De Goeij, A. F. P. M., Cleutjens, J. P. M. and Schutte, B. Cell kinetics of the marine sponge Halisarca caerulea reveal rapid cell turnover and shedding. The Journal Of Experimental Biology, 212.
[Coral Science, Science Daily]
