High-resolution sampling of a broad marine life size spectrum to examine shelf biophysical coupling

Adam T Greer1,2, Alexis C Hagemeyer3,4, John C Lehrter3,5, Malcolm McFarland6, Aditya R Nayak6, Nicole Stockley6, Benjamin Michael Binder7, Ana E Rice8, Kevin M Boswell7, Igor Shulman8, Sergio DeRada8 and Bradley Penta8, (1)The University of Southern Mississippi, Division of Marine Science, Stennis Space Center, MS, United States, (2)Skidaway Institute of Oceanography, Marine Sciences, Savannah, GA, United States, (3)Dauphin Island Sea Lab, Dauphin Island, AL, United States, (4)University of South Alabama, Marine Sciences, Mobile, AL, United States, (5)University of South Alabama / Dauphin Island Sea Lab, Dauphin Island, AL, United States, (6)Florida Atlantic University, Harbor Branch Oceanographic Institute, Fort Pierce, FL, United States, (7)Florida International University, Biological Sciences, North Miami, FL, United States, (8)Naval Research Laboratory, Stennis Space Center, MS, United States
Many biological sampling systems have been developed to describe organism distributions in response to oceanographic forcing over multiple spatiotemporal scales. While these systems are often compared to conventional net-based systems, the trade-offs among different high-resolution sampling systems are rarely evaluated (usually due to logistical constraints) even though this approach is critical for assessing data quality. The trade-offs among systems are related to spatial coverage (based on tow speed, direction, and sample volume) as well as target organism size, fragility or tissue density, swimming speed, and taxonomic level of identification. Near-simultaneous deployment of different sampling systems, with slight overlap in the target taxa traits (e.g., size or susceptibility to capture), can reveal sampling trade-offs and simultaneously assess the coupling of plankton distributions to fine-scale physical oceanographic processes. As part of the Intermediate Trophic Levels (InTro) sampling program on the shelf near Delaware Bay, we sampled organisms ranging in size from several microns to ~50 cm by deploying several high-resolution systems, including (in ascending order of target organism size) a CytoSense, HOLOCAM, In Situ Ichthyoplankton Imaging System (ISIIS), multi-frequency acoustics, and a suite of optical instruments, primary production measurements, and HPLC phytoplankton classifications. Despite relatively low temperature and salinity stratification, aggregations were common for different size classes of particles, including a ~300 m patch of bivalve larvae between 15-30 m depth that exceeded concentrations of 10,000 ind. m-3 and likely would have been missed with station-based sampling (5 nm resolution). Large particles near the surface tended to have an oblong shape, likely dominated by discarded appendicularian houses. The evaluation of each system’s “sampling wheelhouse” helps in identifying relevant data for different ecological processes and will aid in the design of efficient, hypothesis-driven sampling programs.