Award: OCE-1433979

Many marine organisms have a planktonic larval stage in their life history, and their adults that often have limited mobility rely on their planktonic larvae for dispersal. It is fundamentally important to investigate the interaction between individual larva and its surrounding fluid, because such larva-fluid interaction significantly impacts larval survival and transport in the ocean. The major goal of this research is to quantify the fine-scale, both spatial and temporal, larva-fluid interaction by using a newly developed high-speed, micro-Particle Image Velocimetry (µPIV) technique. Such research is crucial for achieving a mechanistic understanding of larval morphology, behavior, and ability to perform key ecological functions, e.g., collecting particles, avoiding predators, and responding to immediate surrounding flow conditions. This understanding will, in turn, provide insights on the evolution of larval forms and behaviors, and inform factors that shape population dynamics of marine invertebrates. In this project, we conducted extensive high-speed microscale video observations of the fine-scale behavior and measured the flow imposed by a larva swimming freely inside a relatively large water vessel (in contrast to using a microscope to observe larvae held inside a tiny well as done previously). We have obtained a large amount of video data that visualize and quantify the behavior and imposed flow of larvae of a variety of size, morphology, and behavior. We provided previously unknown information on how larvae actually swim, feed, and generate flow at unprecedented spatial and temporal resolutions. We have used these data/information to shed light on several important research questions that cannot be addressed before: We characterized the size-dependent patterns in larval-fluid interaction by quantifying the trade-off between larval feeding/swimming performance and predation risk. We found the overall "tethering" mechanism by which a larva creates an efficient feeding current for suspension feeding. We also for the first time measured the inhalant and exhalent water currents generated by bottom-settled clam juveniles and revealed novel features that clam juveniles adapt to the challenges of suspension feeding at small scales. Our research has added significant new knowledge to marine larval ecology at the individual scales. As to the broader impact of this project, three graduate students and a visiting scholar have participated in this project and received training in using the µPIV technique for their research. We also constructed a project website to host sample videos and share with the general public: https://www2.whoi.edu/staff/hsjiang/research/larvae/ Last Modified: 01/26/2018 Submitted by: Houshuo Jiang