The Signature range’s vertical-beam echosounding facility is also a valuable asset, previously used to image zooplankton and manta ray feeding in the Maldives (Figure 6).
“Nortek’s echosounding mode is key to providing echo intensity, helping us to understand the kind of particle transport occurring in response to observed internal waves,” he added.
Meanwhile, two Signature1000 ADCPs were deployed in the shallower waters over the summit to observe turbulence, sediment and biomass movements simultaneously. When processed and analyzed through Nortek’s Ocean Contour post-processing software, readings from these should help demonstrate the extent of trophic focusing of zooplankton over the summit of the seamount.
“The Signature1000 will help to comprehensively demonstrate that trophic focusing of zooplankton over the summit is occurring, hopefully tying the whole story together,” Dr. Hosegood says.
These primary moorings were interspersed with several Aquadopp Profilers (both the 400 kHz version and the 600 kHz version), which provide background information on the overall current regime of the seamount.
A unique vessel-mounted ADCP gives greater understanding
Despite the insights provided by means of moored ADCPs and vessel-mounted echosounder transects, the lack of a vessel-mountable ADCP capable of profiling over the seamount dropoff limited the extent to which researchers could prove the interaction between predators, prey and physical phenomena. By measuring currents and biomass over the entire seamount summit, Dr Hosegood’s team would be able to obtain a “snapshot” of the physical and biological interactions occurring at a given moment in time.
This requirement led to the development of the Signature VM Ocean, an adapted version of Nortek’s Signature100 ADCP. This new product is capable of profiling currents up to at least 330 m from the surface, allowing for a greater understanding of the deeper waters around the drop-off. The addition of a vertical multifrequency echosounder to the Signature100 will help to identify the movement of predators and prey in relation to the internal lee waves identified in previous studies.
Having their first vessel-mounted, combined current profiler/echosounder will allow Dr Hosegood and his team to employ the most up-to-date technology available in expeditions to previously understudied locations around the world.