sensors to measure dissolved oxygen, a chlorophyll-a sensor and a SEABIRD bottle
release unit including a rosette water sampler. For the analysis and interpretation of
the measurements, the downcast raw data were processed with “SBE Data
Processing” software. For the visualization of the data we used “OCEAN DATA
VIEW (mp-Version 4.5.7. (https://odv.awi.de)). So-called yoyo (down ..up..
down. . .) CTD casts were performed (760 mbsl water depth) at 44
01.40
0 North
and 005
42.17
0 West, 1.8 nm North of the “Aguda de Fuero” High (Fig. 11.2). The
yo-yo CTD casts were conducted during the time when the lander was at the
seafloor. During these casts the research vessel remained at the selected position
for 8 h and after 9 h of other station work returned to the same spot for another 7 h
where we performed additional consecutive CTD casts. These two time windows
allowed for the reconstruction of one complete tidal cycle.
11.2.2 Mini-Lander Operations
The mini-lander system was deployed almost at the same locality at 44
01.414
0 1
North and 005
42.431
0 West at 762 mbsl water depth, to measure the physical
characteristics of bottom water dynamics. The deployment was performed fully
video-guided by a launching system that is equipped with a Posidonia system for
exact positioning on the seafloor and live camera system in order to first visually
explore the site and secondly, to select a suitable deployment position. The distance
between the yoyo-CTD and the mini-lander system was 4.17 cables. We decided to
keep a little distance between the yoyo site and the lander position in order to avoid
any interference with the in situ current measurements of the lander system.
The lander system was equipped with a Conductivity-Temperature-Depth
(CTD) profiler (RBR XR-420CTm) and a high precision pressure sensor with an
accuracy of 0.015% of the total water depth. The system also carried an ADCP
(Acoustic Doppler Current Profiler) to measure ocean currents above the system.
Measurement intervals on both instruments were set to 10 s. To release the system
from the seafloor we used a releaser from K.U.M. Umwelt- und Meerestechnik
GmbH, Kiel. In comparison to classical lander deployments (e.g. Mienis et al.
2009) the deployed system has the advantage of being a compact design with easy
handling and logistics, as well as sensors being closer to the sediment-water
interface. ADCP data were visualised by the MATLAB software package, tidal
analysis was performed by T_Tide Harmonic Analysis Toolbox (Pawlowicz et al.
2002).
11 Water Mass Measurements Around Benthic Communities: A Comparative Study. . .
187
release unit including a rosette water sampler. For the analysis and interpretation of
the measurements, the downcast raw data were processed with “SBE Data
Processing” software. For the visualization of the data we used “OCEAN DATA
VIEW (mp-Version 4.5.7. (https://odv.awi.de)). So-called yoyo (down ..up..
down. . .) CTD casts were performed (760 mbsl water depth) at 44
01.40
0 North
and 005
42.17
0 West, 1.8 nm North of the “Aguda de Fuero” High (Fig. 11.2). The
yo-yo CTD casts were conducted during the time when the lander was at the
seafloor. During these casts the research vessel remained at the selected position
for 8 h and after 9 h of other station work returned to the same spot for another 7 h
where we performed additional consecutive CTD casts. These two time windows
allowed for the reconstruction of one complete tidal cycle.
11.2.2 Mini-Lander Operations
The mini-lander system was deployed almost at the same locality at 44
01.414
0 1
North and 005
42.431
0 West at 762 mbsl water depth, to measure the physical
characteristics of bottom water dynamics. The deployment was performed fully
video-guided by a launching system that is equipped with a Posidonia system for
exact positioning on the seafloor and live camera system in order to first visually
explore the site and secondly, to select a suitable deployment position. The distance
between the yoyo-CTD and the mini-lander system was 4.17 cables. We decided to
keep a little distance between the yoyo site and the lander position in order to avoid
any interference with the in situ current measurements of the lander system.
The lander system was equipped with a Conductivity-Temperature-Depth
(CTD) profiler (RBR XR-420CTm) and a high precision pressure sensor with an
accuracy of 0.015% of the total water depth. The system also carried an ADCP
(Acoustic Doppler Current Profiler) to measure ocean currents above the system.
Measurement intervals on both instruments were set to 10 s. To release the system
from the seafloor we used a releaser from K.U.M. Umwelt- und Meerestechnik
GmbH, Kiel. In comparison to classical lander deployments (e.g. Mienis et al.
2009) the deployed system has the advantage of being a compact design with easy
handling and logistics, as well as sensors being closer to the sediment-water
interface. ADCP data were visualised by the MATLAB software package, tidal
analysis was performed by T_Tide Harmonic Analysis Toolbox (Pawlowicz et al.
2002).
11 Water Mass Measurements Around Benthic Communities: A Comparative Study. . .
187