Project summary:

Between 2020-2024, we conducted four polar night field campaigns using UiTs research vessel RV Helmer Hanssen as well as the infrastructure in Ny-Ålesund, Svalbard. In addition to the field campaigns, we developed a light field model, used existing data to model vertical migration behavior, conducted laboratory experiments to measure activity and light sensitivity, and designed a mesocosm for broadband acoustics calibrations. The project also utilized data from the ArcLight Observatory in Ny-Ålesund. In addition to the core Deep Impact group, we closely collaborated with other projects and partners to optimize use of resources (ship time, autonomous sampling platforms) and involved a larger number of students and early career researchers (ECR). 

Overall, 34 peer reviewed articles and 18 datasets have been published, and Deep Impact partners have contributed to 6 book chapters.

24 presentation were given by Deep Impact partners presenting scientific results at national and international scientific conferences and meetings.

Result from Deep Impact have demonstrated that observations from optical and acoustic instruments using light sources with broad spectral composition in the 400–700 nm wavelengths do not capture the real state of the ecosystem and that they cannot be used alone for reliable abundance estimates or behavioural studies. This result has broad applications for the development and use of scientific instruments in marine environments. As a direct response to DI observations, Norwegian research vessels have installed red lights on deck, and the overall awareness in the research community to the effects of lights from ships and instruments and the potential bias on observations has been raised.

The light field model developed during the project is unique as it operates uninterrupted throughout the full year, able to calculate light fields from the sun above AND below the horizon as well as light from the moon and will be valuable for future studies beyond light pollution.

Deep Impact has demonstrated that marine animals are sensitive to very low light levels, far below what is currently measurable using commercially produced underwater light detectors. We have also demonstrated that the spectral distribution of light is critically important in determining animal responses. A key finding of the project is the outstanding need for development of higher sensitivity, spectrally resolved light sensors to measure underwater light fields for both ambient and artificially enhanced light regimes.

Furthermore, we have established that the light field produced by a research vessel is very heterogeneous, with extreme variations in light penetration in different directions. This poses a further measurement challenge that we expect will require development of remotely operated or autonomous platforms equipped with the highest sensitivity detectors and able to accurately position themselves in 3D relative to the position of a target vessel. The combination of extreme dynamic range, spectral response and positioning / directionality of the light field is a major challenge for which the consortium is continuing to develop new tools.

The mesocosm experiments for broadband target strength spectra measurements has advance our understanding of the potential for acoustic spectral-based species discrimination. This is an important step forward to discriminate between acoustic signals of different taxa, a subject of wide interest within fisheries research and management.