Mathematical Modeling of Sea-Ice Extent and Primary Production Shows Changes in Pelagic-Benthic Coupling

Pelagic benthic coupling is one of the most important processes in the Arctic Ocean and relatively little has been done to investigate the effects of climate variability on it.  Pelagic-benthic coupling depends on vertical flux and is influenced by sea ice thickness, extent, and patterns of formation and melting.  Vertical flux is the distribution and transportation of nutrients throughout the water column.  It is determined by primary production, zooplankton feeding, and physical oceanography processes.  Three conceptual biogeochemical models were used to investigate future ecosystem scenarios in the European Arctic Corridor, a region crucial for carbon cycling in the Arctic.  The first looked at climate changes effects on the timing of sea ice formation and melting and the corresponding phytoplankton blooms taking into account water stratification.  The second looked at the same thing but factored in vertical export of the bloom.  The third took into account the three areas of Arctic Ocean: open ocean (alpha ocean), seasonal ice zone (beta ocean), and multiyear ice zone.  Climate change will affect the beta ocean the most, and some areas may even turn into alpha ocean.  There will a longer period with no sea ice overall, which will extend ice algae and phytoplankton blooms.  Primary production will decrease, and this will decrease the yields of fisheries because of less vertical flux. Smaller phytoplankton will flourish.  The remaining vertical flux will be less seasonal in nature because of the dissolution of traditional sea-ice cycles. —Katherine Recinos         
Wassmann, P., and M. Reigstad, 2011. Future Arctic Ocean seasonal ice zones and implications for pelagic-benthic coupling. Oceanography 24, 220–231.

Wassmann and Reigstad state that there has been an ongoing lack of research on the Arctic, especially about pelagic-benthic coupling.  This is because the Arctic is hard to access and pelagic-benthic coupling differs from region to region in the Arctic Ocean and is thus hard to accurately measure in one study.  However, mathematical models have been developed which take biological, physical, and chemical data and create an overall picture for environmental scenarios in the Arctic Ocean.  Wassmann and Reigstad advocate the use of these models, and use three in this paper.  These are either adapted from other studies, or created by the authors specifically for this study.
Climate change will affect the extent of sea-ice in the Arctic which is intrinsically linked to the growth of sea-ice algae.  The importance of this algae depends on the area of ocean in consideration, but it plays a role in vertical flux and as a food for benthic organisms.  If the amount of sea-ice decreases, the blooms of ice algae will shift, leading the water to become more stratified, subsequently decreasing primary production.  This may happen in the Barents Sea.
A lengthening of the season with no sea-ice will lead to earlier phytoplankton blooms as well as ice algae blooms.  This will shift traditional patterns of nutrient consumption by zooplankton and trigger earlier vertical flux.  The vertical flux will be stretched out over a greater time frame which will lead to less pulsed pelagic-benthic coupling but more steady overall levels.  There will not be an increase in nutrients.  
Wassmann and Reigstad discuss alpha, beta, and multiyear ice oceans in terms of a warming climate.  Beta oceans will undergo the greatest changes and possibly adopt the characteristics of alpha oceans.  Vertical flux and productivity will decrease due to stratification.  The authors give examples of further studies to be done including collecting remotely sensed data on phytoplankton distribution and temperature-dependant respiration in areas with slowly increasing temperature.     

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