Award: OCE-2138465

Mysids are shrimp-like crustaceans which form a large, critical component of the aquatic zooplankton biomass across freshwater, marine and estuarine ecosystems. They are key consumers and producers in aquatic food webs, usually aggregating in dense swarms to facilitate feeding, reproduction, and predator avoidance. Despite this, they are relatively understudied compared to other major crustacean groups, e.g., euphausiids such as krill. Primarily, challenges with sampling are associated with their ‘patchy’ distributions, which render them difficult to locate. Additionally, in situ behavioral observations have been hampered by a lack of effective methods.

In this project, a novel stereoimaging system for mapping in situ observations of zooplankton behavior and aggregations was developed. The system was successfully validated across both lab and field experiments, highlighting its in situ observational capabilities. Data processing tools that allowed for computation of both individual and aggregation metrics, including but not limited to organism swimming speeds and acceleration, swarm/school densities, orientation, and nearest neighbor distances were developed.

Over the span of three years, a comprehensive study on the feeding ecology, spatial patterns, swarm dynamics, and animal-fluid interactions among the mysid species, Neomysis americana, was conducted in the Damariscotta estuary in Maine, USA. Along with standard net-based sampling, a state-of-the-art benthic instrumentation suite, consisting of the stereoimaging system and acoustic profilers, facilitated the simultaneous characterization of spatial patterns of mysid swarms and their interaction with the local flow, generating an invaluable database. Neomysis americana was found in the Damariscotta River estuary throughout the year, confirming that they do not migrate out of the estuary during winter months. Neomysis americana population density peaked in the summer and declined through the fall and winter with the lowest population density observed in early spring. When compared with other environmental and biological variables, temperature was the most important driver of Neomysis americana abundance. The stereoimaging data highlighted that mysids exhibited rheotactic behavior, i.e., aligned themselves into the flow, with more organized distributions occurring at higher flow rates.

Broader Impacts: A graduate student, fully supported through this project, was trained at the interdisciplinary interface of ocean engineering, biological oceanography and fluid mechanics. An annual three-day undergraduate workshop on Fluids and Marine Ecology was developed and held over the first three years of the project, with the location rotating across the three host institutions. Each year, 10 participants were selected to the workshop and participated in topical lectures, career path discussions, field surveys in estuarine and coastal environments, and interactions with scientists across the career spectrum. The participant feedback received was extremely positive and to the best of our knowledge, ~ 30% of the total cohort continued/are continuing to work on an advanced degree in a related field, highlighting the value of the workshop in STEM workforce retention. Finally, a large field dataset, consisting of several movies of Neomysis americana aggregations, was recorded in diverse flow and light conditions, representing the first such collection in a natural environment. This database is made available to the public and scientific community through the NSF BCO-DMO website. Additionally, the comprehensive observations enabled by the newly developed stereo-imaging system can offer valuable insights into complex behavioral patterns, social interactions, and predator–prey dynamics, highlighting how future applications in targeted studies could enhance our understanding of meso- and microzooplankton ecology.

 

Last Modified: 06/28/2026
Modified by: Aditya R Nayak