So far North, we have the Polar Night with 3 months of darkness from November to February and 3 month of light “midnight sun” from May to July. This variation in day length, light intensity and spectral composition of light defines what we call the light climate and is one of the major cues of life.
Picture of two young polar bears roaming on the sea ice sheet with the setting sun taken in March 2021, photo credit: Natalie Summers
Life under the ice
In this extreme environment, I am studying small micro algae that grows on the underside of the ice. Microalgae is found all over the world. They can be drifting in the ocean as part of the phytoplankton creating blooms when the conditions are right. These little organisms use energy from sunlight to turn water (H20) and carbon dioxide (CO2) to make glucose (a form of sugar they can use to grow). As a byproduct they release oxygen. These oceanic microalgae are responsible for releasing more oxygen into the atmosphere than the rainforests. In addition, algae are the basis of the food web providing food for many organisms.
Scientist on R/V Kronprins Haakon watching as we navigate through the ice. As the ice is breaking and ice chunks are flipping over, we noticed evidence of the ice algae bloom (brownish layer). Photo credit: Natalie Summers.
What is interesting about algae growing under the ice is that they somehow survive through the dark Polar Night during which time the water column gets mix. This mixing brings up nutrients from the deeper parts of the Arctic Ocean. So that when the sun starts appearing and can penetrate through the ice sheet, the algae suddenly blooms. The underside of the ice is then covered by a layer of microalgae. As the ice drifts south into warmer waters and melts, and the algae use up the nutrients they die, start sinking down the water column where they are food for many organisms.
Enabling technology for mapping algae
Despite their importance, ice algae are very challenging to study. Traditionally, research have used ice cores to get samples from the bottom of the ice. Alternative method requires scuba divers and a lot of safety logistics. Fortunately, we live in the age of technology. With the help of collaborators in the department of Marine Technology, I have been able to use a small remotely controlled vehicle (a type of robot) that can carry different instruments including an underwater hyperspectral camera. Using this system, I am trying to map macroalgae habitats as well as microalgae growing on the underside of the ice and gather some biological information about the health state of the algae growing under the ice.
Figure: the first version of the mini ROV-UHI system t we used during the Polar night to map the kelp forest. Where (A) shows the schematics of the mini ROV-UHI system with 1. Mini-ROV, 2. UHI, 3. Altimeter, 4. Underwater electronic housing, 5. Buoyancy tubes (PVC tubes filled with incompressible foam); (B) shows the front view of the mini ROV-UHI during kelp forest mapping; (C) and (D) show the side and aft view of the ROV-UHI system in action. From Summers et al. 2022, Credits: (A) by Malin Bø Nevstad, (B-D) by Geir Johnsen
A normal camera functions similar to our eye with red, blue and green receptors that then make up all the colors we see. With the hyperspectral camera we can get information that covers the whole light spectrum. This added layer of detail allows us to identify objects of interest based on their optical fingerprints. This novel mini-ROV-UHI system was first deployed in 2020 during the Polar Night to map the Kelp Forest in Kongsfjorden (Ny-Ålesund, Svalbard). We were able to differentiate between the three major alga groups: green, red, and brown macroalgae.
Figure showing the location of the kelp forest mapping during the Polar Night in Kongsfjorden. (A) Geolocalisation in Svalbard; (C) the study side in Kongsfjorden with the survey site represented as a red diamond; (D) the mini-ROV-UHI system just under the water surface where pancake ice is forming. From: Summers et al. 2022. Credits: (A- B) Modified from on (Johnsen et al 2021); (C) N. Summers (modified from https://geokart.npolar.no/) and (D) N. Summers
In May 2021 we went to the Barents Sea on R/V Kronprins Haakon as part of the Nansen Legacy spring cruise. Over the course of this three-week cruise, we deployed the mini-ROV-UHI system at three different locations to map the underside of the ice. With this data, we will get a better understanding of the light climate under the ice which includes light intensity (how much light gets through the ice) and wavelengths (which colours are available for the ice algae to use). In addition, we will get information about how much algae there is (biomass) and what are the major groups/species that are found.
Photo: Natalie Summers, sawing ice to make a hole in the ice for the ROV with R/V Kronprins Haakon in the background. Taken in May 2021. Photo credit: Natalie Summers
Photo: Jens Einar (PhD in Marine technology, NTNU) and Tore Mo Bjørklund (PhD in Marine Technology, NTNU) launching the mini-ROV-UHI system. Photo credit: Natalie Summers
Photo: The mini ROV-UHI system in action under the ice taken from a Blueye ROV. The brownish layer seen here is ice algae growing on the underside of the ice.
This work is very important. As the climate is warming, the Arctic is changing very fast. These organisms rely on sea ice as part of their life cycle. With the ice cover diminishing every year and a possible future of ice-free Arctic summer, we are in against time to learn and understand this ecosystem. Technology is advancing fast and allowing us to gather data in unprecedented speed and quantity. However, we need more biologists to make sense of this data. Interdisciplinary research such as this are crucial to advance our common knowledge about this planet. We need more large-scale interdisciplinary projects like the Nansen Legacy.