Award: OCE-1948162

The aim of this project was to leverage existing samples—collected during previous NSF-funded research expeditions in the North Pacific and North Atlantic—to investigate how the abundance, diversity, and size distribution of midwater zooplankton vary with latitude and environmental conditions. Despite the disruptions caused by the COVID-19 pandemic, we made significant progress in understanding the factors shaping the vertical and latitudinal distribution and behavior of zooplankton.

One of our early published findings indicates that diel vertical migrators—organisms that ascend to surface waters at night to feed and descend to deeper layers during the day to avoid predators—are more ecologically flexible. These animals are less constrained by narrow environmental gradients, likely due to their ability to tolerate a wide range of conditions (e.g., temperature, salinity) encountered daily. This physiological flexibility may explain their broader latitudinal distribution.

As expected, we also observed differences between the Atlantic and Pacific communities. In the Pacific, the presence of a pronounced oxygen minimum zone (OMZ) at depth strongly influences community composition. In contrast, the Atlantic Ocean, where deep waters remain above suboxic thresholds, exhibits minimal latitudinal variation in zooplankton communities at depth. Further analysis of these patterns is ongoing and will continue in the coming years.

Zooplankton communities in the ocean are dominated by copepods, a diverse group of small crustaceans that form the primary link between oceanic primary producers and higher trophic levels such as fish. While copepods are often treated as a single group in ecological studies, the planktonic copepod community is primarily composed of two major clades: Calanoida and Cyclopoida. Calanoids are among the most ancient copepods and exhibit a broad range of sizes and morphologies. Cyclopoids, in contrast, are more evolutionarily derived and include both free-living and parasitic species.

Our research showed that these two groups exhibit distinct morphological-environmental relationships. For Cyclopoida, we observed a straightforward trade-off between depth, size, and transparency: only small, transparent species inhabit the upper photic zone, while larger and darker species dominate deeper layers. Calanoida displayed a more complex pattern. Although surface waters were generally dominated by transparent individuals, these were not always small. Highly transparent species were present in the upper layers regardless of size. However, when transparency decreased, the expected pattern emerged: small species occurred in shallower waters, while larger, darker species occupied deeper habitats. Notably, a subset of very large, dark Calanoids was also found near the surface. Understanding how these conspicuous individuals persist in surface waters remains an open question and is a topic for further investigation.

Building on our findings regarding transparency, we explored a key question: could transparency, rather than size, be the primary functional trait structuring zooplankton communities? Traditionally, size has been considered the “master trait,” influencing physiology (via allometric scaling), ecological niche, visibility to predators, and locomotion efficiency. However, recent research — including our own — suggests that transparency may be a better predictor of an organism’s ecological role, environmental sensitivity, and contribution to ocean biogeochemical cycles.

Our data from the North Pacific show that transparency may be a stronger determinant of both species distribution and diel vertical migration behavior than size. Migration activity was minimal among highly transparent individuals, increased with decreasing transparency, and then declined again among the darkest individuals, which tended not to migrate. This pattern may reflect the idea that dark individuals remain vulnerable to visual predators even if they migrate, reducing the benefits of vertical movement. A manuscript detailing these findings is currently under review for publication.

The High Dive into Ocean Data workshop, supported by this award, provided a hands-on, immersive experience for postsecondary educators to develop and implement data literacy modules grounded in authentic oceanographic and atmospheric research. Ten faculty members from community colleges and universities across ten U.S. states participated in a weeklong field and lab-based program at BIOS, where they engaged with real-time data, scientific research, and expert-led instruction on data management and interpretation. Participants were selected to represent a broad range of academic disciplines (chemistry, geology, environmental science) and educational contexts. The engagement continued after the workshop to build a community of practice to implement new data modules to ensure optimization that was informed by faculty and student feedback. The support for development of a new digital infrastructure continues to be scalable, supporting student-led data learning outcomes.

Last Modified: 05/14/2025
Modified by: Leocadio Blanco-Bercial