Fig. 1: Spatiotemporal coverage of zooplankton sampling by the Palmer Long-Term Ecological Research program.

Changes in (a) sampling grid extent, (b) spatial resolution (crosses indicate subset of discontinued stations), (c) cruise dates, and (d) survey frequency have logistical and scientific costs and benefits. Under the original sampling regime (1993–2008) 52 grid stations were sampled on average. Currently, an average of 26 annual stations are sampled across a larger area. Over the first 28 years, mean survey start and end dates were 8 January and 2 February (vertical gray lines on timeline). Timing shifted earlier after 2020, and survey frequency was reduced to every other year beginning in 2024. Colors indicate latitudinal subregions. On the map, symbol size indicates whether a station is sampled in the current design, and shape indicates whether a station was part of the original survey design or added more recently. Gray shading indicates seafloor depth. Map made using data from the SCAR Antarctic Digital Database¹⁰⁶ and the International Bathymetric Chart of the Southern Ocean¹⁰⁷ under Creative Commons Attribution 4.0 International Licenses.