Pre-composting of the Invasive Macrophyte Rugulopteryx okamurae – Terrestrial Isopods to Recycle Their Massive Upwellings?

Since 2015, the invasive alga Rugulopteryx okamurae has triggered the most serious marine macrophyte invasion in Europe. The removal of its huge coastal biomass generates health problems, strong odors, impact on tourism and high clean-up costs. As a circular economy strategy we propose composting with native terrestrial isopods that has not been previously tested. Therefore, specimens of Porcellio laevis were captured in urban parks and kept for 5 years in terrariums with adequate humidity and temperature control. A sample of 150 adult specimens was divided into six batches of 25 animals. Three batches were fed with organic household waste (control) and three with a 50% diet of waste and algae (treatment). P. laevis consumed up to 1.5 times their weight per day on the algae diet with little or no weight loss, but there was high mortality in both mancas and adults. However, the results are promising and we propose to encourage research with isopods because of their great voracity, high prolificacy and rusticity for the recycling of invasive algae. It should be explored in further work what percentage of R.okamurae avoids mortality by the diterpenes of the algae.