Publication Date:
2022-03-30
Description:
Kelp forests are important habitats in the strongly environmentally and seasonally variable Arctic. There is a critical lack of
knowledge about how seasonal conditions and climate change scenarios influence survival and reproduction of kelp early
life stages. To better understand the regulation of kelp life cycle processes in this harsh environment we focused on the
physiological performance and reproductive success of early life stages in Alaria esculenta and Laminaria digitata from
Kongsfjorden, Spitsbergen. Gametophyte growth and survival during Arctic winter and subsequent sporophyte recruitment
under spring conditions were investigated. Winter conditions (2°C, complete darkness) halted gametophyte growth and
prevented the onset of gametogenesis in both species. The gametophytes of L. digitata but not A. esculenta became fertile
after returning to spring conditions, suggesting that sporogenesis, sexual reproduction and recruitment in A. esculenta must
occur successively during summer/autumn while in L. digitata a new generation of sporophytes could develop from overwintering
gametophytes. The effects of simulated canopy shading (offering protection against extreme irradiance stress,
particularly as sea ice retreats), present-day and projected Arctic summer seawater temperatures, and nutrient levels on
gametophyte survival, fertility and sporophyte recruitment success were also investigated in both species. A. esculenta
gametophytes had greater survival and reproductive success than L. digitata, except under very low light (simulating dense
canopy). In contrast, shading was required for reproductive success in L. digitata gametophytes. Predicted summer
temperatures of 9°C reduced sexual reproduction in both species. Interactions observed between these environmental
drivers probably reflect species-specific seasonal patterns of survival and reproduction. These differences between kelp
species in response to abiotic factors and light levels (simulated canopy shading) suggest that climate change could alter
community structure in the Arctic through effects on sexual reproduction and sporophyte recruitment success.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev