CTD transekt
We started our scientific data acquisition in the main working area, the Saya de Malha Bank, and on a north-south transect of stations along 65° east. Station work started on the morning of the 21th of September and continued until the 22nd. After 10 hours of transit towards the west, in approaching the platform, we deployed the reflection seismics. Everything worked fine, and we began a 400 nm seismic- and hydroacoustic survey that crosses the Saya de Malha platform in east-west direction. Aim of these lines is to gain insight into the large scale platform architecture, but also to provide a first overview on platform slope geometry. The survey ended on the 26th and since then, we are performing hydroacoustics and sedimentology on the eastern slope and platform top.
An important hypothesis to be tested during the expedition is whether the nature of the intermediate water masses (100-1000 m water depth) impinging on the slope and crest of the Saya de Malha platform presently precludes establishment and growth of colony-building corals on the underwater complex. The bank is situated in a mixing zone of water masses at intermediate depths, some of which are oxygen-poor and nutrient-and CO2-rich, and thus unfavourable for reef growth. We addressed this question by performing the first six of ten CTD casts along 65° from 7°S to 11°S, and in addition at a station directly near the steep eastern slope of the bank. The CTD (conductivity, temperature, depth) instrument is part of a rosette water sampler with 22 bottles and registers water properties (such as temperature, salinity, oxygen concentrations) in high resolution when it is lowered. Going up, water samples are taken by closing the bottles at depths representative of the different water mass types for further ship-based and shore-based analyses.
Highlights
