For her research, De Voogd described three new species of sponges and examined the interactions of four sponge species with possible spatial competitors. She discovered that as soon as certain sponge species grow over corals, the coral develops necrotic tissue. From this she concluded that the sponges concerned produce their bioactive substances to defeat spatial competitors. This is important, as in an environment without spatial competitors, such as in a sponge culture, a lower concentration of the substances of interest to the pharmaceutical industry might be produced.
The researcher tried to rear 9 of the 151 species of sponge observed but was successful with only 3 species. Although the survival rates of these species were generally very high, the growth rates were very slow and unpredictable. Moreover, the reared sponges produced less of the biologically-active substances than their natural counterparts.
Although Indonesia has a very high diversity of sponge species, and therefore a large number of biologically-active substances with pharmaceutical potential, most of the species occur in relatively low densities compared to species in temperate areas. De Voogd discovered that as a result of this low natural density, surprisingly few Indonesian species are suitable for sea rearing.
Sedentary marine invertebrates such as sponges, are an important source for a large variety of biologically-active substances. Until more advanced techniques such as chemical synthesis, genetic modification and sponge cell culture are realised, rearing in the sea remains the most reliable and effective method for obtaining the large quantities of sponge biomass, necessary for developing drugs.
However, sea rearing can only be used for the large-scale production of useful substances if it can yield large quantities of the sponge species. Therefore, sea rearing would only seem to be a profitable option if the quantities of the substance needed are small or if the growth can be optimised in combination with other reared organisms.
Nicole de Voogd's research was funded by NWO.