Impact of global warming on Antarctic and Arctic seaweeds - consequences for community structure and spatial distribution
Final Report Abstract
The Western Antarctic Peninsula (WAP) and the Arctic region are experiencing the fastest rates of global warming worldwide. Surface waters at the WAP have warmed by more than 1 °C since the 1950s and are predicted to warm further into the next century at both regions. In the Polar Regions brown seaweeds build highly complex and productive underwater forests, being an essential part of the polar ecosystem. The young developmental algal stages (propagules) are the most sensitive stage in a lifecycle of an alga, forming the bottle-neck for a successful survival of the species. Until now most studies focused on single factor experiments, there is a general lack of experimental designs testing the interplay of abiotic and biotic factors. To close this gap, multi-factorial experiments on propagules of ecologically important seaweed species and early successional communities at Potter Cove (WAP), Kongsfjorden (Spitsbergen) and in the home laboratories were carried out, in order to identify the most important drivers for successful recruitment. Finally, we combined the results from long-term field studies and multifactorial GIS-based habitat modeling to get a more precise picture of how the changing environmental conditions will alter the polar seaweed communities in an interdisciplinary approach (bundle project with K. Jerosch). Kongsfjorden, Spitsbergen: The macroalgal biomass at Kongsfjorden increased between 1996/1998 and 2012/2013. The entire zonation shifted upwards to shallower depth with significant effects on the associated fauna. - Higher temperatures affected the kelp Alaria esculenta more than Laminaria digitata and Saccharina latissima. - Sediment is the factor most severely affecting recruitment success of kelps but the presence of grazers can counteract this negative effect until a certain point. - Interspecific competition has transient effects during gametogenesis and is acting as resource competition during the development of young sporophytes. Temperature can alter the outcome of competition due to species-specific temperature optima for development. Potter Cove, WAP: Interspecific competition between the two main biomass builders D. menziesii and D. anceps play a minor role during summer while effects such as irradiance and temperature significantly affect the photosynthetic performance. - Both Desmarestia species are highly cold-water adapted. - The development of young Antarctic algal communities is driven by a variety of factors interacting with each other in a complex manner, showing similar patterns as for Arctic macroalgae. - Habitat modeling was used as a predictive tool for analyzing spatial shifts in Antarctic benthic macroalgae communities due to global climate change. An increased sedimentation of 50 % (compared to the current status) is predicted to reduce macroalgal primary productivity in Potter Cove by almost 90 %. Conclusions: Global warming has the potential to change macroalgal communities in both Polar areas due to: A reduced recruitment success (species-specific). Complex interactive effects between mayor drivers of algal recruitment such as temperature, sedimentation (abiotic), grazing and competition (biotic). Indirect effect of temperature increase resulting in an increased sediment run-off. Sedimentation is identified as one mayor driver of macroalgal recruitment in the Arctic and as well in Antarctica, a high sedimentation may lead to a reduced survival and cover.
Publications
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(2014) The susceptibility of spores and propagules of Antarctic seaweeds to UV and photosynthetically active radiation — Field versus laboratory experiments, Journal of Experimental Marine Biology and Ecology, 458, pp. 57-63
Zacher, K
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(2016) Effects of temperature and interspecific competition on growth and photosynthesis of two endemic Antarctic Desmarestia species, Algological Studies
Zacher K, Savaglia V and Bartsch I
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(2016) Photosynthetic light requirements and vertical distribution of macroalgae in newly ice-free areas in Potter Cove, South Shetland Islands, Antarctica, Polar Biology
Deregibus D, Quartino ML, Campana GL, Momo FR, Wiencke C and Zacher K
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(2016) Survival of early life history stages of Arctic kelps (Kongsfjorden, Svalbard) under multifactorial global change scenarios, Polar Biology 39
Zacher K, Bernard M, Bartsch I and Wiencke C
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(2017) Oxidative balance in macroalgae from Antarctic waters. Possible role of FE, Journal of Experimental Marine Biology and Ecology, 486: 379–386
González PM, Deregibus D, Malanga G, Campana GL, Zacher K, Quartino ML and Puntarulo S
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(2017) Succession of Antarctic benthic algae (Potter Cove, South Shetland Islands): structural patterns and glacial impact over a four year period, Polar Biology
Campana G, Zacher K, Deregibus D, Momo, F, Wiencke C and Quartino ML
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(2017) Understanding the link between sea ice, ice scour and Antarctic benthic biodiversity; the need for cross station and nation collaboration, Polar Record
Deregibus D, Quartino ML, Zacher K, Campana GL and Barnes DKA
