Abiotic Changes Driving Microphytoplankton Functional Diversity in Admiralty Bay, King George Island (Antarctica)

Denise Rivera Tenenbaum,Fernanda Reinhardt Piedras,Domênica Teixeira de Lima,Marcos Vinícius Pereira Borges de Campos,Márcio Murilo Barboza Tenório,Thais de Oliveira Cornejo,Leticia Cotrim da Cunha,Gleyci Aparecida Oliveira Moser,José Juan Barrera-Alba

doi:10.3389/fmars.2019.00638

Abstract

Environmental gradients can provide habitat-specific scenarios for community functional diversity that determine the composition of populations on both spatial and temporal scales. The western shelf of the Antarctic Peninsula has experiencing increasing air temperatures while the climate is transitioning to a warm-humid sub-Antarctic-type of climate. As a consequence, abiotic changes are leading to alterations in the trophic web. Microphytoplankton functional diversity was analyzed across environmental gradients of sea surface temperature, salinity, meltwater percentage and nutrient availability in Admiralty Bay, South Shetland Islands, Western Antarctic Peninsula. Samples were collected during the austral summer from 2009 to 2011 and from 2013 to 2015, at Admiralty Bay for which functional diversity indices were calculated based on species traits. The amount of meltwater (MW) present in Admiralty Bay groups microphytoplankton into communities according to physiological and ecological tolerances, thus leading to a greater functional diversity. When meltwater dominated the bay (> 2.25% MW scenarios iii - 2013-14 and iv - 2014-15), diatoms and dinoflagellates were codominant. An increase in the dinoflagellate fraction of microphytoplankton can be considered a trigger for changes in the structure of the Antarctic food web. Our results suggest using Admiralty Bay as a model for studies on changes in microphytoplankton community composition and functional diversity.

Highlights

The climate of the western shelf of the Antarctic Peninsula (WAP) is undergoing a transition from a cold-dry polar-type climate to a warm-humid sub-Antarctic–type climate (Montes-Hugo et al, 2009)
Spatial Variation The abiotic variables and chlorophyll a (Table 1) differed among sampling stations, not significantly (ANOVA – Tukey Test p > 0.05), indicating that the spatial distribution of abiotic variables does not influence the response of the microphytoplankton community with regard to biomass
The hydrographic conditions, as well as the nutrient availability and variation in phytoplankton biomass, observed in this study resemble the gradients and variation reported in the literature for WAP at various temporal scales

Summary

Introduction

The climate of the western shelf of the Antarctic Peninsula (WAP) is undergoing a transition from a cold-dry polar-type climate to a warm-humid sub-Antarctic–type climate (Montes-Hugo et al, 2009). Microphytoplankton Diversity in Admiralty Bay of 0.56◦C decade−1 over the years analyzed (Turner et al, 2005) and a 2◦C increase in annual mean temperature (Ducklow et al, 2007). This regional increase has consequences for the dynamics of shelf and sea ice (Moline et al, 2004; Rozema et al, 2017; Aracena et al, 2018). Climate change in WAP (e.g., increase in temperature and environmental variables) has driven modifications in phytoplankton size (Barrera-Alba et al, 2012, 2015; Lange et al, 2014; Vanzan et al, 2015), composition, biomass and community structure (Kopczynska, 2008; Montes-Hugo et al, 2009; Piquet et al, 2011; Lange et al, 2014; Tenório et al, 2015; Mendes et al, 2018; Russo et al, 2018)

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