RUI: Collaborative Research: Exploring Barnacle Exoskeleton Development and Materials Properties as a Function of Growth Environment

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Non-Technical SummaryBarnacles have attracted the attention of explorers, scientists, and sailors for millennia. They are crustaceans, similar to shrimp, lobsters, and crabs, but unlike their freely moving relatives are encased in a hard outer shell and securely stuck to a surface. The barnacle outer shell is a biomineral, a composite material consisting of a mixture of proteins, chitin (fibrous strings of sugar molecules), and minerals, which in barnacles are largely calcium carbonate. Despite the fact that barnacles play a large ecological and economical role -as they stick to ships, hulls, amongst other surfaces, causing the ships to slow down and use more fuel- little is known about how the barnacle exoskeleton forms or if climate changes predicted in coming years will alter this formation process. The proposed work, done entirely by undergraduate students under the supervision of the two project PIs, focuses on determining how the exoskeleton forms by examining the very early stages of exoskeleton development. In addition, the project will explore how the formation process changes when barnacles are grown in warmer and more acidic waters. This work will not only provide information on the formation of an interesting and potentially useful material, but also how an economically and ecologically important organism will respond to predicted future ocean conditions. Beyond this basic knowledge, the project will provide invaluable training opportunities in STEM to undergraduates at both Colgate and TCNJ, as well as to high school students from underrepresented communities in New York. Technical SummaryThe barnacle exoskeleton is a robust biomineralized tissue, yet it is structurally disordered on the atomic to micrometer level. This is in contrast to most well-studied biomineralized tissues (e.g. vertebrate bone, mollusk shells) which have ordered, hierarchical structures. The goal of this project is to characterize the developmental process by which this disordered exoskeleton forms and the extent to which environmental conditions impact the exoskeletal material. The first objective is to identify the composition, structure, and materials properties of the barnacle exoskeleton during the time period immediately following metamorphosis through to full mineralization under ambient marine conditions. Juvenile barnacles will be tracked following metamorphosis from larval cyprids through a combination of techniques (confocal microscopy, scanning electron microscopy, Raman spectroscopy, x-ray photoemission electron microscopy (X-PEEM), micro-indentation, and nano-indentation), allowing determination on whether certain materials properties, such as fracture toughness, are linked to a disordered structure. The second objective is to examine how the composition, structure, and materials properties of the developing exoskeleton behave under decreased pH and increased temperature (mimicking predicted ocean conditions in the year 2100 with current climate change predictions). The results from these experiments will provide insight into the functionality of disordered biological materials, while also providing information into whether an ecologically and economically important organism will be impacted by impending environmental changes. In addition to the important fundamental knowledge derived from these experiments is the broader impact the proposed work will have on undergraduate and high school students. Undergraduate researchers, under the supervision of the two PIs, will conduct the entirety of the proposed work, participating in not only the research, but also conferences and manuscript preparation. A workshop for high school students from underrepresented communities in New York, in conjunction with Camp Fiver, will be based on the results of the proposed work, exposing and involving the high school students in scientific research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.