Efectos del calentamiento climatico y el pastoreo sobre una comunidad de algas marinas bentonicas Antarcticas, en etapas tempranas de sucesion


Contact
Katharina.Zacher [ at ] awi.de

Abstract

The Antarctic Peninsula is one of the regions most seriously affected by climate warming. Rising temperatures are considered a stress factor for the rather stenothermal benthic algae inhabiting in this region. Furthermore, it has also been associated to glacier retreat, which causes increased freshwater inflow and sedimentation into the water column, which consist of environmental changes that impose stress conditions for benthic organisms. Besides abiotic factors, grazing is one of the most important drivers of benthic algal communities, particularly at early stages of succession. The objective of the present study was to evaluate experimentally the effects of environmental perturbations ssociated to climate warming in the Antarctic region- such as increased temperature and sedimentation- and grazing, on benthic algal communities at early stages of succession. Artificial substrates (ceramic tiles, 25 cm2) were installed at a subtidal site in Potter Cove (25 de Mayo/King George Island, South Shetland Islands, Antarctica) and, after eleven months of colonization, a trifactorial experiment was performed to test the effects of temperature (2 °C and 6 °C), sediment load (with and without added sediment) and grazing by the gastropod Nacella concinna (ungrazed and grazed) on eveloped communities. Samplings were performed after 12, 14 and 36 days. Species composition and abundance of juveniles (>1mm) and early stages (>0.02mm) of macroalgae, the structure of diatom assemblages (taxonomic composition, density and ecological indexes), biomass and photosynthetic efficiency were assessed. Tiles were dominated by juvenile thalli of Palmaria decipiens and early stages of P. decipiens, Monostroma hariotii and Adenocystis utricularis, which are typical macroalgal species in early stages of succession at the Antarctic benthos. Nineteen diatom taxa were identified, mostly pennate and typically benthic forms. Increased temperature did not exert any effects on macroalgal cover nor on diatoms density. However, higher temperatures caused higher diversity and evenness in diatom assemblages probably due to changes in the relative abundance of species that are not sensitive to this factor. Sedimentation exerted positive or neutral effects on macroalgal cover and seems to protect the communities at short term, when early stages are more sensitive to high irradiance conditions. However, it negatively affected diatom evenness. Grazing by N. concinna controls diatom assemblages by reducing their density. These consumers can potentially counteract positive (or negative) sedimentation effects by removing the sediment cover. Over longer time scales, higher temperature and sedimentation may limit the photosynthetic efficiency of marine benthic algal communities in Antarctica. Early stages of succession are subject to complex interactions between abiotic and biotic factors in the Antarctic benthos. In a climate change context, the action of multiple changing factors can introduce alterations in the structure and functioning of the communities of Antarctic benthic algae, which play a central role in this system.



Item Type
Thesis (Master)
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Divisions
Primary Division
Programs
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Peer revision
Not peer-reviewed
Publication Status
Published
Eprint ID
52273
Cite as
Debandi, J. (2019): Efectos del calentamiento climatico y el pastoreo sobre una comunidad de algas marinas bentonicas Antarcticas, en etapas tempranas de sucesion , Master thesis,


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