Shipboard Plankton Dilution Experiment Chlorophyll collected at the mid-Atlantic Bight Shelfbreak on R/V Neil Armstrong AR29, R/V Ronald H. Brown RB1904 and R/V Thomas G. Thompson TN368 to the New England Shelfbreak in April 2018 and and May/July 2019

As part of the Shelfbreak Productivity Interdisciplinary Research Operation at the Pioneer Array (SPIROPA) Project, twelve grazing experiments utilizing the two-point dilution technique were conducted during each of three research cruises (April of 2018, and May and July of 2019) in the Middle Atlantic Bight to estimate microzooplankton grazing rates and net phytoplankton growth rates. Stations where the dilution experiments were conducted were strategically located in one of three key cross-shelf water mass regimes: (1) at the shelfbreak front, (2) inshore of the front in continental shelf water and (3) offshore of the front in slope water. Grazing incubations were performed on water sampled from the chlorophyll maximum, when present, and conducted on the <200 µm fraction of water (what passed through a 200 µm sieve) in order to include only the microzooplankton grazers and avoid trophic cascades associated with mesozooplankton predators and grazers. The 2 dilution points were 10% and 100% of the < 200 µm sample water. All experiments were run in triplicate for 24 hours and consisted of a dark treatment incubation and a light treatment incubation at a simulated 30% E0.