Small but key to nature conservation: Small packed communities in a small lagoon from a biodiversity hotspot

1. Coastal lagoons are generally assumed to be naturally stressed environments. They are expected to be uniform ecosystems, dominated by r-strategist species. 2. There is increasing evidence that they are complex, with strong self-regulatory mechanisms and homeostatic capacity based on diversified trophic networks. 3. We here show a small coastal lagoon, with strong urban influences, yet with relatively complex communities enclosed in algal balls structured by Valonia aegagropila C. Agardh. 4. These balls were colonized by several algae and invertebrates living inside, constituting a biocenosis with a remarkable species richness and functional and structural diversity. 5. The results showed that the meiofaunal biomass from Valonia balls is not directly controlled by their size or total volume. Rather, the ability to produce its biomass and regulate its energy depends mainly on the characteristics of its diversity, either due to its species richness or the abundance of the fauna that inhabits this system. 6. Consequently, the biological productivity of the groups could be maintained in balance with the energy flow of the ecosystem in a context of a highly anthropized partially enclosed lagoon ecosystem.