Algal Colonization of Young Arctic Sea Ice in Spring

Ilka Peeken,Pedro Duarte,Mats A Granskog,Hanna M Kauko,Mar Fernández-Méndez,Christopher J Mundy,Philipp Assmy,Alexey K Pavlov,Geir Johnsen,Lasse M Olsen

doi:10.3389/fmars.2018.00199

Abstract

The importance of newly formed sea ice in spring is likely to increase with formation of leads in a more dynamic Arctic icescape. We followed the ice algal species succession in young ice (≤0.27 m) in spring at high temporal resolution (sampling every second day for one month in May–June 2015) in the Arctic Ocean north of Svalbard. We document the early development of the ice algal community based on species abundance and chemotaxonomic marker pigments, and relate the young-ice algal community to the communities in the under-ice water column and the surrounding older ice. The seeding source seemed to vary between algal groups. Dinoflagellates were concluded to originate from the water column and diatoms from the surrounding older ice, which emphasizes the importance of older ice as a seeding source over deep oceanic regions and in early spring when algal abundance in the water column is low. In total, 120 taxa (80 identified to species or genus level) were recorded in the young ice. The protist community developed over the study period from a ciliate, flagellate and dinoflagellate dominated community to one dominated by pennate diatoms. Environmental variables such as light were not a strong driver for the community composition, based on statistical analysis and comparison to the surrounding thicker ice with low light transmission. The photoprotective carotenoids to Chl a ratio increased over time to levels found in other high-light habitats, which shows that the algae were able to acclimate to the light levels of the thin ice. The development into a pennate diatom-dominated community, similar to the older ice, suggests that successional patterns tend towards ice-associated algae fairly independent of environmental conditions like light availability, season or ice type, and that biological traits, including morphological and physiological specialization to the sea ice habitat, play an important role in colonization of the sea ice environment. However, recruitment of ice-associated algae could be negatively affected by the ongoing loss of older ice, which acts as a seeding repository.

Highlights

The Arctic icescape is changing rapidly, which affects the whole marine system (Meier et al, 2014)
The objectives of the study were to describe the succession of ice algal species and algal pigment concentrations in young sea ice formed in spring, identify the most important drivers for the algal succession, and compare the young ice community with the surrounding older ice and water column to identify the seeding source
Our study provides the first observations of algal species succession in newly formed sea ice in spring

Summary

Introduction

The Arctic icescape is changing rapidly, which affects the whole marine system (Meier et al, 2014). Primary production or algal species dynamics and habitats are altered for example by a shorter ice season (Arrigo and van Dijken, 2015) and likely by the reduction of multi-year ice (Lange et al, 2017; Olsen et al, 2017b). The sea ice is more dynamic and vulnerable to wind forcing (Itkin et al, 2017), which can alter the habitat of ice algae. An estimated 7.5% of annual Arctic primary production is attributed to ice algae (Dupont, 2012). Ice algae constitute a highly concentrated food source early in the growth season (e.g., Søreide et al, 2010), and are a crucial part of Arctic marine foodwebs

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