Award: ANT-2040199

PROJECT OUTCOMES --- NSFGEO-NERC: “Collaborative Research – P2P: Predators to Plankton —Biophysical Controls in Antarctic Polynyas

 

In a USA-UK/NSF-NERC collaboration, to better understand food web dynamics and structure of a Southern Ocean trophic hotspot --- the Ross Sea Polynya marginal ice zone (MIZ) --- and to resolve a penguin population growth paradox (population increase despite compromised, significantly underweight fledglings), we 1) deployed acoustically-equipped gliders in a dense grid to assess size, location and density of prey, both inside and outside of the penguin intensive foraging area; thereby 2) quantifying preyscape-related biophysics using glider sensors (mixed-layer depth, stratification, irradiance, chlorophyll and particulate matter concentrations); but also 3) penguin biologging to quantify foraging area use as affected by preyscape and oceanographic characteristics; 4) penguin diet by direct and DNA/stable isotope analysis; and 5) quantification of the presence of competing whales and seals, using the passive glider as well as sea watches. We knew from previous work that abundant Adélie Penguins from one of the world’s largest colonies, Cape Crozier (9% of global population), alter the preyscape to the point they need to seasonally expand foraging area (to >150 km from colony), leading to smaller, infrequent feeds and in the end underweight fledglings, whose survival should be compromised. We thus sought to test the hypothesis that beyond foraging area limits in the absence of intense predation, fish and krill vertical distributions, i.e. prey patches, significantly differ (e.g., larger, more cohesive, and shallower) from those within. These patches are thus a ‘reservoir’ available once penguins are no longer constrained by central place foraging (repeated return to colony to feed chicks). We also sought to measure whether predator-induced changes in prey patterns would be affected by habitat quality, e.g. biophysical attributes such as water column stratification and chlorophyll. Findings ultimately will help to parameterize food web models in Antarctic coastal systems.

 

In November 2022 we deployed 3 gliders, two with active acoustics and one with passive acoustics (to detect whales). One of the active acoustic gliders was lost. We also had to alter our original sampling plan because the wind stopped and, therefore, the pack ice did not disappear as expected. More so, owing to logistics beyond our control, we had to pick up the gliders three weeks earlier than planned (mid-January 2023). Recent US government uncertainty affected our data analysis, impacting some of our co-PIs. Nevertheless, we managed to present preliminary results at a Ross Sea conference in Naples, Italy, in 2023; and at International Underwater Glider Conference in Gotenburg, Sweden, in 2024. We held a data analysis workshop there and in 2024 in US. We are working on the following publications, most of which were led by early career scientists, the titles of which provide a sense of what we thus far have learned. Data analysis and writing proceeds:

 

Portela et al. (2024) Unprecedented summer phytoplankton bloom in the Ross Sea. Geophysical Research Letters 52, e2024GL111264.

Meyer et al. (in press) Critical uncoupling between biogeochemical stocks and rates in Ross Sea springtime production–export dynamics. Ocean Sciences.

Ainley et al. (submitted) The importance of fish in the diet of Adélie penguins across multiple life stages. Antarctic Science.

Meyer et al. (in progress) The role of shallow eddies in foodweb disruption in the Ross Sea.

Trocars et al. (in progress) Occurrence patterns of cetaceans along the marginal ice zone of the southern Ross Sea.

 

Last Modified: 07/07/2025
Modified by: David G Ainley