Response of an Antarctic Lake Ecosystem to Climate Variation: Linkages between Phytoplankton Species Dynamics and Streamflow Diane M. McKnight 1, Erin Von Maytre 1, John C. Priscu 2,W. Berry Lyons 3, and Michael Gooseff 1 1. Institute of Arctic and Alpine Research Boulder, CO 2. Dept. of Biology, Montana State University, Bozeman, MT 3. Byrd Polar Research Institute, Ohio State University, Columbus, OH

Background – Ice Covered Lakes Ice cover- 3-5 m thick, moat in summer Source- streamflow from glacial melt Loss- ablation of ice cover Water column- stable w/depth, some lateral circulation Light penetration about 1% or less

Main Phytoplankton Species Chlamydomonus intermedia Oscillatoria linenetica Chlamydomonas subcaudata

Main Phytoplankton Species Phormidium angustissimum Chroomonas lacustris Starburst protazoa

Dominant species occur in depth zones

Dry Valleys and Global Climate

Interannual variability in phytoplankton

Depth-wise Zonation Taxa Size(  m 3 ) Depths (m)% PAR : Oscillatoria sp Oscillatoria limnetica Cryptomonas sp Chroomonas lacustris Pyramimonas sp Phormidium angustissimum Chlamydomonas subcaudata 904various

Depth-wise Zonation cont’ Taxa Size(  m 3 ) Depths (m)% PAR Ochromonas nannos* 170* ** Chlamydomonas sp Cryptomonas sp Chroomonas lacustris Pyramimonas sp * Vincent, 1981 ** Vincent, 1988

stream gauge algal transect

NR

Chroomonas lacustris Biovolume

Chlamydomonas intermediaPhormidium angustissimum Oscillatoria limnetica Chroomonas lacustris Cryptomonas sp. Lake Fryxell Biovolume (  m 3 /mL) Nov. 18Dec. 29

Chlamydomonas intermedia Biovolume

Oscillatoria limnetica Biovolume

Phormidium angustisimum Biovolume

Phytoplankton species changes Species Low flow High flow Low flow Chroomonas lacustris dominantrareabundant Cryptomonas sp. presentdominantpresent Chlamydomona s subcaudata present?abundantrare Chlamydomona s intermedia present?rareabundant Phormidium angustisimum rare?present Oscillatoria limnetica rare?present>> present

Potential Factors Controlling Phytoplankton Light regime in summer Nutrients (N)- diffusion from below oxycline and input from streams Mixotrophy and overwinter persistence Microbial loop dynamics

Cyanobacterial mats in stream

Stream algal mat changes StreamHabitatMats Change from Canada pavementabundantnone Bowles pavementabundantnone Green pavementabundantnew green mats Delta (upper) pavementabundantnew moss Huey sandysparse more orange, new black Delta (lower) sandysparsenew orange Von Guerard sandysparsemore mats Lawson steepsparse more orange & moss

NR ND

QQ QQ NR ND

Summarizing - trends Streamflow- high flow followed by sustained low flow Major ions increased in upper water column Stream mats-recovery followed by decrease Stream nutrient fluxes- variable!!

Conclusions Phytoplankton response to changing climate occurs at the species level Patterns for chlorophytes and cryptophytes related to flow regime Increasing cyanobacterial abundance Potential factors include light regime, nutrient fluxes, mixotrophy, and major ion chemistry

A few words of Thanks: National Science Foundation Project No. OPP , McMurdo Dry Valleys LTER. MCMLTER colleagues Antarctic Support Associates staff