Date of Award
2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Ocean Engineering
Department
Ocean Engineering
First Advisor
Brennan Phillips
Abstract
Science and technology are coupled disciplines. Breakthroughs in ocean science are often pertinent to the ability to observe physical, chemical, and biological processes at the right temporal and spatial scales, which typically involves the use of robots. Large, powerful, and extremely capable, the scientific work-class remotely operated vehicle (ROV) is the golden standard when observing fine temporal scale intricate processes in the full ocean stratum and has unraveled important discoveries in deep-sea biology and ecology. Sound, light, and hydrodynamic forces produced from these vehicles are sources of disturbances that may impact quantitative observations in the twilight zone, an environment absent of light. While 60 years of studies in the past have delved into the interactions between marine animals and oceanographic sampling equipment, only a handful of studies studied the potentially large effect ROVs can pose on the water column. There is a large gap on understanding the potential biases these vehicles pose and improving our methodology for future studies in the deep-sea are critical. Mechanisms of these disturbances and the complex interactions of these stimuli with these deep-sea animals are not well understood. This study adds new compelling evidence of avoidance and attraction of deep scattering layers during two scientific ROV transects from opportunistically taken hydro acoustic data. Characterization of sound and light produced from scientific ROVs are investigated from two opportunistic passive acoustic recordings and a compilation of potential light emissions from different science ROVs coupled with a theoretical light penetration over range model. Results show that ROVs produce sound pressure levels exceeding 80 dB ref 1μPa2 Hz-1 dominantly present at low frequencies (< 1 kHz), which is well within the hearing thresholds of several mesopelagic fishes. Furthermore, multiple ROVs can potentially produce > 150,000 lm of light, potentially affecting up to 50 m from the source based on calculations. Opportunistically taken ship-mounted split-beam echosounder data at 18 and 38 kHz was able to capture dispersion of mesopelagic deep scattering layers (DSL) in the presence of two different scientific ROVs from two distinct dives. These layers were seen to dynamically dissapate and aggregate when the vehicle was in proximity. Furthermore, to investigate further, a test case study in Bermuda 2023 was performed to observe mid-water animal’s response towards dynamically adjusting light intensity levels using a novel custom-built system. The system was unique and designed with an emphasis on producing no sound that allows for unobtrusive sampling. Observations were recorded synchronously using a low-light sensitive camera and multi-frequency active acoustics mounted on the vehicle and the ship. The assimilated acoustic data gave a unique and novel perspective when observing animal behavior. While the experiment had several technical shortcomings, preliminary results reveal an indication of the animals at closer distance to the system were attracted. However, artificial light intensity levels did not affect much of the behavior response based on statistical tests. There is also an indication of a particular aggregation of animals maintaining constant vertical distance from our system as seen from the ship-mounted acoustics. In summary, this new system will open new avenues of research while broadening our perspective on the deep-ocean environment that will be useful to the oceanographic community. Understanding previous methodology and new technological advances are required to answer many new scientific questions. Upcoming threats to our ocean e.g., global warming, industrialized deep-water fishing, and ocean mining potentially could harm and dynamically alter the delicate interactions that occur in epipelagic and mesopelagic on a global scale.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Sapiie, Rendhy Moreno, "TREADING CAREFULLY IN THE DEEP OCEAN: INSIGHTS INTO THE EFFECTS OF ARTIFICIAL LIGHT AND SOUND FROM ROBOTIC PLATFORMS ON PELAGIC ANIMAL SURVEYS USING ACTIVE ACOUSTICS AND LOW-LIGHT IMAGING TECHNIQUES" (2024). Open Access Dissertations. Paper 1682.
https://digitalcommons.uri.edu/oa_diss/1682