Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
  • Problem Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Project Information
• Funding

The primary data file of this dataset (985768_v1_ocean_conditions_at_seabird_colony_sites.csv) contains seasonally and spatially averaged stratification, mixed layer temperature, and chlorophyll-a around Northern Hemisphere seabird colonies.

The GLORYS12V1 global ocean reanalysis was used to characterize the marine environment of the study ecoregions and ecosystems. This high-resolution model (1/12° horizontal resolution, daily temporal resolution, 50 vertical depth levels) assimilates historical data from 1993 to 2019 and has been validated against independent observations. Environmental variables—including temperature, mixed layer depth, and salinity—were extracted for the upper 200 m to calculate coastal stratification using the Potential Energy Anomaly (PEA). The PEA, a robust metric for seasonal stratification, is particularly useful in shallow, coastal regions where permanent stratification may be disrupted by tidal and wind mixing. For full methodological details, see Killeen et al. (2025, in review).

Spatial and temporal averaging to provide ecoregional monthly values: Data within each ecoregion were extracted by masking the dataset with ecoregion polygons defined by the Marine Ecoregions of the World (MEOW). All values within a polygon were averaged to produce monthly ecoregion means for the period 1993 to 2019.

Monthly values for each variable were then averaged over the periods corresponding to the pre-breeding (on-colony arrival to mean egg-laying date) and breeding (mean egg-laying date to mean fledging date) seasons of seabird colonies in the Northern Hemisphere subset of the Global Seabird Breeding Success Dataset. The resulting joined dataset includes yearly seabird breeding success and productivity estimates per seabird time series, along with corresponding mixed layer temperatures, stratification, and chlorophyll-a content during the pre-breeding and breeding periods. Seasonal, ecoregional averages were then standardized by subtracting the mean and dividing by the standard deviation for each ecoregion. To examine seabird breeding responses to interannual variability in environmental variables, quadratic detrending was applied to temperature, stratification, and chlorophyll-a.

* Special characters have been removed from the parameters/column names in the primary data file (985768_v1_ocean_conditions_at_seabird_colony_sites.csv) and replaced with underscores ("_").
* Latitude and longitude values have been rounded to six decimal places.
* Originally, the primary data file only contained common name representations of observed species. Scientific names have been added to the data file, along with corresponding AphiaID and LSIDs from the World Register of Marine Species (WoRMS) database.

NSF Award Abstract:
Global warming is affecting the world’s oceans by altering marine habitats, yet the effects on marine life vary by ocean region. One factor that may explain these observations is that ocean surface waters have warmed faster than deeper waters. Temperature differences may act as a physical barrier to mixing, thereby impeding deeper nutrients from reaching the sunlit surface where they are used by ocean plants in photosynthesis. With less mixing, the upper layers of the ocean may have become less productive, which may in turn impact marine fish, bird, and mammal populations of economic and cultural (ecological) value to society. To conduct this study, the investigators are examining the effects of ocean warming by depth on the abundance of plankton, small fish, and the breeding success of marine birds across the world using existing long-term data. They are developing mathematical relationships to understand how ocean warming at various depths is linked to plankton, fish, and bird productivity. Results will provide key information for selecting which seabird species may be best suited as ecological indicators of change for different ecosystems across the globe, and therefore has implications for remote-ocean monitoring. The project will contribute new scientific understanding for upcoming United Nation assessment reports and enhance public awareness of ocean health through outreach materials centered on popular seabirds such as puffins and penguins. It will support early career and postdoctoral scientists.

Ocean thermal stratification is an important factor determining primary productivity in epipelagic zones of the world’s oceans. A recent global analysis showed declining trends in the breeding productivity of fish-eating seabirds that forage in the epipelagic zone, but increasing stratification has yet to be investigated as an explanatory factor. The primary objective of this project is to test the hypothesis that seabird species groups vary in their responses to increasing thermal stratification through the indirect effects of stratification on epipelagic food resource availability and/or prey use by the birds. The investigators are testing the prediction that thermal stratification has the largest effect on breeding productivity of piscivorous, surface-foraging species. They are integrating a new global database on seabird productivity with high-resolution data on thermal stratification available from the European GLORYS model, as well as satellite-based chlorophyll-a data from NASA. They are using Generalized Linear Mixed Models to test for variation between seabird groups and Structural Equation Models to test direct and indirect pathways of response from stratification through prey availability to seabird productivity, focusing on mid-to-high latitude ecosystems across ocean basins in both the northern and southern hemispheres. Results will improve understanding of how seabirds respond to increasing thermal stratification in relation to fundamental differences in seabird life history traits. The retrospective analysis will advance knowledge of how seabirds that feed on different prey, and in different epipelagic habitats of the world’s oceans, have responded to recent increases in stratification. More generally, the study will contribute insight into how physical changes in the upper ocean affect predators through the availability of food resources.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Location Description:
Data to be analyzed are from around the world and contributed from numerous local providers and other groups. The study area is the global ocean. Analysis will be done at the Farallon Institute, located in Petaluma, California.