*2.3. Benthic Landers*

Two seafloor monitoring lander systems were deployed at NK bank reef to study the topographical effect of the bank on the flow between May 2016 and April 2017. One of the landers (SLM) was deployed south of the CWC bank at 63.608◦ N 9.383◦ E at 211 m water depth, while the other one (MLM) was deployed on the CWC bank at 63.609◦N 9.382◦ E at 196 m water depth, ~125 m apart from each other (Figure 1C). Both landers were equipped with an Acoustic Doppler Current Profiler (ADCP, Teledyne RD Instruments) to measure water column flow speed and direction at 6-min intervals in between 3 to 30 m above the sea floor (with SLM) and from 5 m above the sea floor upward to the surface (with MLM). The landers were also equipped with a CTD system (SeaBird Electronics) combined with sensors to monitor dissolved oxygen, turbidity, fluorescence, and pH. Sampling intervals were set to 10 or 30 min. Processing of the raw CTD data was performed using the software package SBE Data Processing [63] and the raw ADCP data with the RDADCP Matlab package [64]. The accuracy and sensitivity of these instruments are shown in Table 2.


**Table 2.** Instrumentation details and metadata for landers deployed at Nakken bank reef area. Abbreviations: WD: water depth.

> Unfortunately, the lander on the NK CWC bank (MLM) tilted due to high flow velocities in mid-August. This resulted in a separation of the bottom weight and the buoyancy compartment that includes all sensors. Thus, the sensor head was released and floated upwards to ~100 m water depth after 3.5 months deployment time in mid-August, where it continued to measure all parameters. The SLM remained at deployment depth

until its recovery in April 2017. ADCP, CTD, oxygen, and SLM turbidity sensors provided reliable time-series data. pH and fluorescence sensors malfunctioned. The conductivity sensor had an instrumental drift that amounted to −0.5 g kg−<sup>1</sup> over the deployment period. This drift has been taken into account when the hydrographic variables (Θ, SA, σΘ) were calculated.
