Variations in the summer phytoplankton community structure in Atlantic sub-Arctic and Arctic waters

TY - CONF

T1 - Variations in the summer phytoplankton community structure in Atlantic sub-Arctic and Arctic waters

AU - Small, Alison

AU - Bouman, Heather

AU - Hughes, Claire

PY - 2015/9

Y1 - 2015/9

N2 - The Arctic is currently experiencing a period of rapid environmental change, and has undergone substantial climatic warming over the last several decades. During this time there have been dramatic reductions in the extent and thickness of sea ice, a freshening of surface waters and an increase in cloud cover, which has led to changes in surface mixing, stratification and light. This change in the physical properties of the water column can potentially alter the main factors governing marine primary production: light, nutrients and temperature. The degree to which these changes will positively or negatively affect levels of primary production is a subject of much debate yet little certainty. In addition there is current uncertainty as to how changes in sea-ice conditions will impact the size and taxonomic structure of phytoplankton. Shifts in phytoplankton community structure serve not only as indicators of environmental change but also have implications for food-web interactions and biogeochemical cycles. The community structure of marine phytoplankton in sub-Arctic and Arctic waters was examined using 157 samples collected in the summer of 2013 along a latitudinal gradient spanning from 61.1 to 83.1 degrees N along the east coast of Greenland. Accessory pigment concentrations were used to infer information about the phytoplankton taxa present using CHEMTAX (CHEMical TAXonomy), an iterative MATLAB subroutine. The main algal classes found within the study region were diatoms, dinoflagellates, haptophytes, chlorophytes, cryptophytes and prasinophytes. Diatoms were present at nearly all stations and depths and were large contributors to the total pigment biomass for both ice and open water stations. Deeper samples were mainly dominated by diatoms and haptophytes. Surface sample communities were characterised by mixed assemblages, including dinoflagellates and chlorophytes although diatoms and haptophytes still comprised a significant portion of the pigment biomass. The differences in community structure were investigated in relation to the environmental conditions through multivariate statistical analysis (cluster and principle component analyses) in order to understand the factors influencing the spatial distribution of the various algal classes. Diagnostic pigment indices were also used to calculate the concentration of Chl-a attributed to three size classes (picophytoplankton 0.2-2µm, nanophytoplankton 2-20µm and microphytoplankton >20µm). These data were compared to a similar dataset from the same cruise where size fractionated Chl-a was separated by sequential filtration and quantified by fluorometric anaylsis. Size-fractionated Chl-a as measured directly by sequential filtration suggested a primarily mixed community across the study region. In contrast pigment based analysis suggested a strong dominance of larger cells and also resulted in the complete absence of picoplankton in some samples. These results suggest that diagnostic pigment indices may not be an accurate method of determining size classes in this region.

AB - The Arctic is currently experiencing a period of rapid environmental change, and has undergone substantial climatic warming over the last several decades. During this time there have been dramatic reductions in the extent and thickness of sea ice, a freshening of surface waters and an increase in cloud cover, which has led to changes in surface mixing, stratification and light. This change in the physical properties of the water column can potentially alter the main factors governing marine primary production: light, nutrients and temperature. The degree to which these changes will positively or negatively affect levels of primary production is a subject of much debate yet little certainty. In addition there is current uncertainty as to how changes in sea-ice conditions will impact the size and taxonomic structure of phytoplankton. Shifts in phytoplankton community structure serve not only as indicators of environmental change but also have implications for food-web interactions and biogeochemical cycles. The community structure of marine phytoplankton in sub-Arctic and Arctic waters was examined using 157 samples collected in the summer of 2013 along a latitudinal gradient spanning from 61.1 to 83.1 degrees N along the east coast of Greenland. Accessory pigment concentrations were used to infer information about the phytoplankton taxa present using CHEMTAX (CHEMical TAXonomy), an iterative MATLAB subroutine. The main algal classes found within the study region were diatoms, dinoflagellates, haptophytes, chlorophytes, cryptophytes and prasinophytes. Diatoms were present at nearly all stations and depths and were large contributors to the total pigment biomass for both ice and open water stations. Deeper samples were mainly dominated by diatoms and haptophytes. Surface sample communities were characterised by mixed assemblages, including dinoflagellates and chlorophytes although diatoms and haptophytes still comprised a significant portion of the pigment biomass. The differences in community structure were investigated in relation to the environmental conditions through multivariate statistical analysis (cluster and principle component analyses) in order to understand the factors influencing the spatial distribution of the various algal classes. Diagnostic pigment indices were also used to calculate the concentration of Chl-a attributed to three size classes (picophytoplankton 0.2-2µm, nanophytoplankton 2-20µm and microphytoplankton >20µm). These data were compared to a similar dataset from the same cruise where size fractionated Chl-a was separated by sequential filtration and quantified by fluorometric anaylsis. Size-fractionated Chl-a as measured directly by sequential filtration suggested a primarily mixed community across the study region. In contrast pigment based analysis suggested a strong dominance of larger cells and also resulted in the complete absence of picoplankton in some samples. These results suggest that diagnostic pigment indices may not be an accurate method of determining size classes in this region.

M3 - Poster

T2 - UK Arctic Science Conference

Y2 - 16 September 2015 through 18 September 2015

ER -