Grain size analysis and total organic matter and carbonate contents of sediments on Saya de Malha and Nazareth Banks

Abstract

The Mascarene Plateau is one of the least studied regions of the Western Indian Ocean. The aim of this paper is to describe the qualitative grain size characteristics and the total organic matter and carbonate contents of sediments on the two underwater banks known as the Saya de Malha and Nazareth Banks. Sediment samples were collected during the R/V Dr Fridtjof Nansen expedition in 2018, using a Video-Assisted Multi-Sampler (VAMS). Sieving techniques and GRADISTAT software were used for granulometric analysis and grain size statistics, respectively. Total organic matter and carbonate contents were determined with the sequential weight loss on ignition method. Grain size parameters from 15 stations (depths ranging from 37 to 381 m) are reported in this study. The results showed that sand was the dominant grain size on both banks. Eleven of the 15 stations had a mean grain size of coarse sand, three stations had a mean size of medium sand and one station had fine sand. The average total organic matter and carbonate contents on the Banks ranged from 2.1 to 7.7 % and from 53.9 to 58.3 %, respectively. This study provides baseline information that will help to classify benthic habitats and better understand the ecosystem functioning and dynamics on of the Saya de Malha and Nazareth Banks.