Western Antarctic Peninsula Glacial History and its Importance to Understanding Contemporary Marine Ecosystem Structure and Function William R. Fraser and Hugh W. Ducklow Palmer Station Long Term Ecological Research Program Photo by H. Ducklow

Outline Glacial History and Contemporary Ecosystem PropertiesGlacial History and Contemporary Ecosystem Properties Climate Setting and Climate MigrationClimate Setting and Climate Migration WAP Ecological ResponsesWAP Ecological Responses Conclusions and New DirectionsConclusions and New Directions

Breeding Distribution of Adélie Penguin Populations in the western Antarctic Peninsula (WAP) region Adélie penguins are flightless and incapable of foraging at night, which greatly limits the range over which they can search for prey in summer when feeding chicks and during winter when day length is short Hypothesis: winter and summer breeding Adélie distribution is as a consequence limited to regions where prey availability is predictable over ecological time scales (decades to centuries) Photo by H. Geisz, PAL LTER

Hypothesis Testing Adelaide Isl. Renaud Isl. Anvers Isl.

Adélie Breeding-Foraging Associations with Deep Bathymetry and Primary Production Contour of regions of low pCO 2 (highlighted in red), based on WAP January cruises D. Karl, unpublished

Adélie Breeding-Foraging Associations with Deep Bathymetry and Winter Polynyas SOGLOBEC, WINTER 2001.

Climate and its seasonality…key physical drivers of ecosystem evolution 0.107˚ C/year Significant at 0.05 ~5.4x global average Perennial Ice

One of the mechanisms by which climate change induces change in ecosystem structure is by disrupting the evolved life history strategies of component species. Rhodes & Odum 1996 Key Physical Variables are Changing Along a North to South Gradient New Paradigm…Climate Migration Sub-Antarctic Life History Groups are Replacing Antarctic Life History Groups WAP Ecosystem Structure is Changing in Fundamental and Possibly Unprecedented Ways

Key Physical Variables are Changing Along a North to South Gradient Climate Migration and Physical Changes Flooding of the shelf by UCDW and its effects on winter water formation mmmmmm Antarctic Circumpolar Current

Climate Migration and Ecosystem Response mmmmmm Adelaide Isl. Renaud Isl. Anvers Isl. Palmer Sta. WAP Ecosystem Structure is Changing in Fundamental and Possibly Unprecedented Ways Sub-Antarctic Life History Groups are Replacing Antarctic Life History Groups

Regional predator population changes -- avian top predators Habitat optimum hypothesis: Too much ice is as detrimental to Adélie penguins as too little ice. Fraser & Trivelpiece 1996, AGU ANVERS IS ADELAIDE IS On Anvers Island chinstrap and gentoo penguins, two sub-Antarctic species, are replacing Adélie penguins

Regional prey population changes -- Antarctic silverfish (Pleuragramma antarctica) ANVERS IS ADELAIDE IS Antarctic Life History Group

Regional prey population changes -- Lanternfish (Electrona antarctica) ADELAIDE IS Silverfish ANVERS IS Sub-Antarctic Life History Group Lanternfish

ANVERS IS Analyses of Anvers and Adelaide Island Krill Size-Frequency Data from Penguin Diet Samples: Log-linear model framework with residual analysis. Positive residuals > 2.0 are statistically significant (p<0.01) and indicate the cells had more krill than expected. ADELAIDE IS Regional prey population changes – Antarctic krill (Euphausia superba) Statistically significant north to south differences in recruitment frequency and population size structure

Regional changes in primary production (climatology, )

Conclusions and Future Direction Glacially incised, cross shelf canyons are focal points of physical and biological processes affecting WAP ecosystemsGlacially incised, cross shelf canyons are focal points of physical and biological processes affecting WAP ecosystems Climate migration is having an impact on a range of ecosystem properties, from key physical variables to food web structureClimate migration is having an impact on a range of ecosystem properties, from key physical variables to food web structure Trends indicate that the ice- dependent life history group that once populated the northern sectors of the LTER grid is being replaced by an ice- intolerant life history group over ecological time scales.Trends indicate that the ice- dependent life history group that once populated the northern sectors of the LTER grid is being replaced by an ice- intolerant life history group over ecological time scales. Future directions…Future directions… The WAP is the only location in Antarctica where the ACC is directly adjacent to the shelf break Ross Sea gyre Weddell gyre Amundsen Sea Bellingshausen Sea