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IT’S GOOD TO BE BIG—PHAEOCYSTIS ANTARCTICA COLONY SIZE UNDER THE INFLUENCE OF ZOOPLANKTON GRAZERS
Citation:
Tang, K. W., W. O. Smith, D. T. Elliott, AND A. R. SHIELDS. IT’S GOOD TO BE BIG—PHAEOCYSTIS ANTARCTICA COLONY SIZE UNDER THE INFLUENCE OF ZOOPLANKTON GRAZERS. Presented at 2008 Ocean Sciences Meeting; From the Watershed to the Global Ocean, Orlando, FL, March 02 - 07, 2008.
Impact/Purpose:
Presentation
Description:
The haptophyte Phaeocystis antarctica forms extremely dense accumulations in the Ross Sea, Antarctica, and accounts for over 60% of the seasonal primary production. Similar to the Phaeocystis species in the northern hemisphere, P. antarctica exists as solitary cells and mucilaginous colonies that differ by several orders of magnitude in size. Recent experiments with P. globosa suggested that colony formation is a defense mechanism against small grazers. As part of the ESCAP project we conducted incubation experiments at McMurdo Station during austral summer using natural P. antarctica and zooplankton assemblages. Dialysis bags were used to separate P. antarctica and zooplankton but allow exchange of dissolved chemicals. Geometric mean colony size decreased by 35% in the control, but increased by 30% in the presence of grazers even without physical contact. P. antarctica growth rate in terms of chlorophyll a or POC was unaffected, and it ranged 0.26 to 0.28 per d. While our observations support the notion that colony formation and enlargement is a defense mechanism against grazing, the cost of such mechanism, as predicted by defense theory, remains unknown.
