Development of a new protocol for testing bath sponge quality

Abstract

Due to the diverse morphological variation that occurs in sponges between and within species, protocols for quantitative quality testing are required to select sponges and optimise conditions for the aquaculture of high quality bath sponges. A protocol was developed to assess the quality of sponges using mechanical engineering techniques. It quantified the physical properties of sponges (density, fibre width, fibre length, absorbency, and water retention efficiency) and their mechanical properties (firmness, compression modulus, compressive strength, tensile strength, elastic limit, elastic strain, modulus of elasticity, and modulus of resilience). To demonstrate these methods and provide a relative comparison, quality was measured for Rhopaloeides odorabile and Coscinoderma sp. and three commercial species, Hippospongia lachne, Spongia 1, and Spongia 2. There were significant differences between species for all quality parameters creating a unique profile for each species. R. odorabile was the firmest (37.8 ± 4.3 kPa), strongest (157.4 ± 17.3 kPa), and most rigid (838.7 ± 53.5 kPa) species tested, while Coscinoderma sp. was one of the softest sponges (7.3 ± 1.1 kPa) and had the highest elastic energy (30.5 ± 3.5 kJ/m3) and water retention efficiency (40.1 ± 1.4%) of all the species. Of the commercial species, H. lachne was the softest (3.2 ± 0.3 kPa), weakest (36.3 ± 3.1 kPa), and most absorbent sponge (31.0 ± 1.1), while Spongia 1 and Spongia 2 had intermediate quality characteristics for all measured parameters. These tests enable scientifically rigorous comparisons of quality between and within species regardless of origin or post-harvest treatment. Comparisons between species may be used to select species for aquaculture and as a marketing tool to promote aquaculture products for specific applications. Within species testing will allow quantification of differences in quality caused by genetic or environmental factors.