TY - JOUR
T1 - Pelagic microbial heterotrophy in response to a highly productive bloom of Phaeocystis antarctica in the Amundsen Sea Polynya, Antarctica
AU - Williams, C. M.
AU - Dupont, A.m.
AU - Loevenich, J.
AU - Post, A. F.
AU - Dinasquet, Julie Vanessa
AU - Yager, P. L.
PY - 2016
Y1 - 2016
N2 - Heterotrophic bacteria play a key role in marine carbon cycling, and understanding their activities in polar systems is important for considering climate change impacts there. One goal of the ASPIRE project was to examine the relationship between the phytoplankton bloom and bacterial heterotrophy in the Amundsen Sea Polynya (ASP). Bacterial abundance, production (BP), respiration, growth efficiency, and extracellular enzyme activity (EEA) were compared to nutrient and organic matter inventories, chlorophyll a (Chl a), viral and microzooplankton abundance, and net primary production (NPP). Bacterial production and respiration clearly responded (0.04-4.0 and 10-53 μg C L-1 d-1, respectively) to the buildup of a massive Phaeocystis antarctica bloom (Chl a: 0.2-22 μg L-1), with highest rates observed in the central polynya where Chl a and particulate organic carbon (POC) were greatest. The highest BP rates exceeded those reported for the Ross Sea or any other Antarctic coastal system, yet the BP:NPP ratio (2.1-9.4%) was relatively low. Bacterial respiration was also high, and growth efficiency (2-27%; median = 10%) was similar to oligotrophic systems. Thus, the integrated bacterial carbon demand (0.8-2.8 g C m-2 d-1) was a high fraction (25-128%; median = 43%) of NPP during bloom development. During peak bloom, activity was particle-associated: BP and EEA correlated well with POC, and size fractionation experiments showed that the larger size fraction (> 3 μm) accounted for a majority (-75%) of the BP. The community was psychrophilic, with a 5x reduction in BP when warmed to 20°C. In deeper waters, respiration remained relatively high, likely fueled by the significant downward particle flux in the region. A highly active, particle-associated, heterotrophic microbial community clearly responded to the extraordinary phytoplankton bloom in the ASP, likely limiting biological pump efficiency during the early season.
AB - Heterotrophic bacteria play a key role in marine carbon cycling, and understanding their activities in polar systems is important for considering climate change impacts there. One goal of the ASPIRE project was to examine the relationship between the phytoplankton bloom and bacterial heterotrophy in the Amundsen Sea Polynya (ASP). Bacterial abundance, production (BP), respiration, growth efficiency, and extracellular enzyme activity (EEA) were compared to nutrient and organic matter inventories, chlorophyll a (Chl a), viral and microzooplankton abundance, and net primary production (NPP). Bacterial production and respiration clearly responded (0.04-4.0 and 10-53 μg C L-1 d-1, respectively) to the buildup of a massive Phaeocystis antarctica bloom (Chl a: 0.2-22 μg L-1), with highest rates observed in the central polynya where Chl a and particulate organic carbon (POC) were greatest. The highest BP rates exceeded those reported for the Ross Sea or any other Antarctic coastal system, yet the BP:NPP ratio (2.1-9.4%) was relatively low. Bacterial respiration was also high, and growth efficiency (2-27%; median = 10%) was similar to oligotrophic systems. Thus, the integrated bacterial carbon demand (0.8-2.8 g C m-2 d-1) was a high fraction (25-128%; median = 43%) of NPP during bloom development. During peak bloom, activity was particle-associated: BP and EEA correlated well with POC, and size fractionation experiments showed that the larger size fraction (> 3 μm) accounted for a majority (-75%) of the BP. The community was psychrophilic, with a 5x reduction in BP when warmed to 20°C. In deeper waters, respiration remained relatively high, likely fueled by the significant downward particle flux in the region. A highly active, particle-associated, heterotrophic microbial community clearly responded to the extraordinary phytoplankton bloom in the ASP, likely limiting biological pump efficiency during the early season.
U2 - 10.12952/journal.elementa.000102
DO - 10.12952/journal.elementa.000102
M3 - Journal article
SN - 2325-1026
VL - 4
JO - Elementa
JF - Elementa
M1 - 000102
ER -
