These are influential findings that also suggest tipping points, trophic cascades, and subsequent ecosystem changes.Īlgal responses to a changing light regime are well-acknowledged and studied in situ ( Sigler et al., 2014), by remote sensing ( Arrigo et al., 2008 Ji et al., 2013 Ardyna et al., 2014) and through biophysical modelling ( Slagstad et al., 2011 Jin et al., 2012). Sea ice reductions have been suggested to cause regime shifts in the community structure as benthic algae receive sufficient light to become abundant ( Kortsch et al., 2012) and to dominate the seabed community ( Clark et al., 2013). Benthic primary producers are similarly impacted ( Clark et al., 2013).
Lightscape meaning driver#
Light is the core driver of photosynthesis, and we know that less sea ice, and thereby more light entering the water column, can increase the primary production in the pelagic zone ( Arrigo et al., 2008) and alter its seasonal timing ( Ji et al., 2013). The current sea ice changes therefore also correspond to a massive and large-scale change in the light regime-most likely with profound effects on both pelagic and benthic ecosystems. Less ice means more light reaching the waters of high-latitude oceans because sea ice, particularly when snow covered, acts as a lid hindering light to reach the water column ( Grenfell and Maykut, 1977 Sturm and Massom, 2010). Substantial reductions in Arctic sea ice extent and thickness have been observed during the recent decades, and further reductions are predicted ( Stroeve et al., 2012). Mechanistic approaches to these topics offer insights beyond statistical correlations and extrapolations, and will help us understand how changing biophysical dynamics in the Arctic influence complex processes including production, predator–prey interactions, trait-evolution, and fisheries. Research efforts should focus on the dynamics of how less sea ice will affect the feeding ecology and habitat usage of fish, particularly the northern limits of distributions. Expanding distributions and greater visual predation may restructure ecological relationships throughout the Arctic foodweb and lead to regime shifts. Poleward shifts of boreal fish species have been predicted by many and to some extent observed, but a changing light environment has so far not been considered a driver. We combined this insight with mechanistic understanding of how light modulates visual prey-detection and predict that fish will forage more efficiently as sea ice diminishes and that their populations will expand to higher latitudes, at least seasonally. The results show a dramatic increase in the amount of light predicted to reach the future Arctic Ocean. We used the Norwegian Earth System Model estimates of past and future sea ice area and thickness in the Arctic and applied attenuation coefficients for ice and snow to estimate light intensity. Here we argue that there is a need to broaden the view to include light-driven effects on fish, as they depend on light to locate prey. Responses through primary production are so far well acknowledged. Less ice will therefore mean more light entering the water column, with profound effects on pelagic and benthic ecosystems. Sea ice, particularly when snow covered, acts as a lid hindering light to reach the waters underneath. Climate change has led to substantial reductions in sea ice extent and thickness in the Arctic Ocean. A gigantic light experiment is taking place in the Arctic.
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