sinkholes

Background

The Saba Bank, west of the Caribbean island of Saba, is a large (2400 km2) submerged carbonate platform of 15-40m depth rising from 800-1000m depth and fringed with coral reefs along the eastern and southern sides. Saba Bank is the largest protected area of the Kingdom of the Netherlands and a hotspot of biodiversity. In 2018 during the NICO expedition we discovered that part of the Saba Bank, called the Luymes Bank, contains a number of large and deep sinkholes. In 2019 NIOZ and WMR returned to the bank to study these sinkholes and made some extraordinary discoveries.

Objectives

• To study the distribution and environmental conditions (e.g. nutrients, O2, particulate organic matter, water movement, CO2 chemistry) of benthic communities on the platform between sinkholes and in the sinkholes with emphasis on areas with regularly distributed pillar-like structures in sinkholes.

• To take high resolution pictures of the benthic communities with high-resolution camera system and NIOZ video frame in order to describe the benthic communities.

• To collect bottom samples in order to determine the species diversity of these communities.

• To collect pillars and assess the species consortia producing the pillars, their life history strategies, accretion rates and stratigraphic history.

• To survey and investigate the carbonate chemistry of sinkholes of different size and depth and detect the effects of possible stratification in sinkholes.

• To determine metagenomics and metabolomics in water samples from sinkholes of different size and depths.

• To investigate light-dark shifts in metagenomics and metabolomics in near bottom water samples in relation to nutrients, O2, carbonate chemistry and POM in shallow sinkholes (20-40m deep) with and without pillar-like structure and the platform community at approx. 80m depth.

• To collect plankton samples for closer studies of plankton communities over the Luymes Bank.