Award: OCE-1459706

Project objective: The objective of the funded project was to employ a multipronged approach to assessing the impact of ocean acidification (OA) and warming on the growth, biomineralization, and skeletal chemistry of high-latitude crustose coralline algae (CCA), and to use information archived in the skeletons of wild CCA to reconstruct paleo-environmental change. Funding from this award supported a wide range of experimental and field-based research projects in pursuit of these and related objectives, which are summarized below. (1) Sampled coralline algae from the Gulf of Maine (Clathromorphum compactum) and Aleutian Islands (Clathromorphum nereostratum) for OA-temperature experiments. (2) Sampled and analyzed the boron isotope composition and minor/trace element chemistry of two 300-1000 year old cold-water coralline algae rhodoliths (one from the Canadian Arctic and the other on the Labrador Coast, influenced by the Arctic Labrador Current) for paleo-pH and temperature reconstructions of these high-latitude ocean environments. (3) Conducted 90-day controlled laboratory experiments investigating the impact of ocean acidification and warming on net calcification rates and boron isotope signatures of two species of crustose coralline algae (Clathromorphum compactum - Gulf of Maine, Clathromorphum nereostratum - Aleutian Islands). (4) Conduct controlled laboratory experiments investigating the impact of CO2-induced ocean acidification and warming on urchin-coralline algae grazing dynamics on the coralline alga Clathromorphum nereostratum. (5) Analyzed the boron isotope composition of a branching tropical coralline algae (Neogoniolithon sp. - Atlantic ocean) cultured at 4 pCO2 conditions (400, 600, 900, 2850 ppm) and a cold-water crustose coralline alga (Clathromorphum compactum) cultured at 4 pCO2 conditions (280, 400, 900, 3000 ppm) crossed with three temperature conditions (6, 9, 12 deg C) to calibrate a boron isotope paleo-pH proxy for both species (6) Used the boron isotope composition of a branching tropical coralline alga (Neogoniolithon sp. - Atlantic ocean) cultured at 4 pCO2 conditions (400, 600, 900, 2850 ppm) and a cold-water crustose coralline alga (Clathromorphum compactum) cultured at 4 pCO2 conditions (280, 400, 900, 3000 ppm) to calibrate the boron isotope paleo-pH proxies for both species, to constrain the pH at the alga's site of calcification, and to assess how the alga's control of calcifying fluid pH is impacted by CO2-induced ocean acidification. (7) Investigated the impact of warming and CO2-induced ocean acidification on the dissolution kinetics of dead shell material produced by coralline red algae and a host of other marine calcifiers (e.g., corals, bivalves, gastropods, bryozoa, barnacles). (8) Performed multielemental analysis of a branching tropical coralline alga (Neogoniolithon sp.) cultured at 4 pCO2 conditions (400, 600, 900, 2850 ppm) and a cold-water crustose coralline alga (Clathromorphum compactum) cultured at 4 pCO2 conditions (280, 400, 900, 3000 ppm) crossed with three temperature conditions (6, 9, 12 deg C) to assess impact of ocean acidification and warming on elemental partitioning within coralline algal calcite. (9) Used the Mg/Li composition of the cold-water crustose coralline alga (Clathromorphum compactum) cultured at 4 pCO2 conditions (280, 400, 900, 3000 ppm) crossed with three temperature conditions (6, 9, 12 deg C) to calibrate a novel Mg/Li paleotemperature proxy for this species. (10) Use the novel d11B-based paleo-pH proxies and Mg/Li-based paleo-temperature proxies to reconstruct seawater pH and temperature in the Arctic and N. Atlantic, respectively, from 2 high-latitude rhodolith colonies spanning the past 600-1000 years. (11) Identified a suite of elements in the skeletons of the coralline algae C. compactum that show a strong linear response to temperature in controlled laboratory experiments. (12) Conducted a controlled laboratory experiment growing wild-collected C. compactum specimens at various temperatures and salinities to better constrain the potential multielemental paleothermometer for this species and evaluate the impacts of these factors on their calcification rates. (13) Deployed pH and temperature sensors in Arctic Bay, Canada, for 1 year adjacent to colonies of C. compactum to obtain year-long timeseries data to ground-truth the multielemental paleothermometer and d11B-based pH proxy and quantify intra-annual growth rates. The project supported the training of 4 undergraduate researchers, 1 Ph.D. student, and 3 postdoctoral researchers. Research results have been disseminated through 11 invited presentations at universities, 4 invited presentations at other private or public institutions, and 12 conference presentations. The funded research has resulted in 14 peer-reviewed publications (including 3 in review), 12 conference abstracts, and 1 Ph.D. thesis. Results were also widely disseminated to the public through various popular media outlets, the PI's professional website, and publicly accessible data registries. Last Modified: 04/13/2021 Submitted by: Justin B Ries