Meiofauna in sandy back-reef platforms differently exposed to the monsoons in the Maldives (Indian Ocean)

Maldives comprise some of the most characteristic and significant atoll systems, but the meiobenthic assemblages of these islands are still largely unknown. A study on meiofauna was conducted on three Maldivian sandy back-reef platforms differently exposed to stronger westerly monsoons. Clear high energy effects of the waves causing currents and erosions were observed at the completely exposed and isolated offshore reef of Thoddoo Island. Wave energy of medium intensity was confirmed at Rasdhoo by depositional structures (finolhu), while a medium to low energy level was recorded at Gulhi on the basis of the presence of a low sandy bar. The meiofaunal assemblage counted 17 major taxa. Copepods and nematodes were dominant, followed by platyhelminthes and polychaetes. The nematode assemblage was rather rich and composed of 28 families and 84 genera. Desmodoridae were the most abundant family, followed by Draconematidae, Xyalidae, Epsilonematidae and Chromadoridae. The meiofauna resulted strongly affected by erosion effects, both in terms of abundance and richness, but we were not able to distinguish the two different sedimentation rates. Instead, the structure of the nematode community seemed to be more sensitive in distinguishing each type of hydrodynamic condition and energy level.