Euphausia pacifica (Pacific Krill) is a key species in ocean food webs. Krill are metabolically active and are regularly exposed to low pH water through their diel vertical migrations between the deep ocean and surface waters. These characteristics suggest krill may be more tolerant of chronic ocean acidification than other organisms.
My studies determined that E. pacifica is relatively tolerant of chronic acidification, showing no changes to survival or molting frequency, but slower growth at low pH. Slower growth was likely caused by reduced metabolism at low pH, as oxygen consumption, ingestion, and nutrient excretion rates all declined at low pH.
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Carbon dioxide dissolving into the world’s oceans is causing profound and rapid shifts in ocean chemistry, characterized by a drop in the pH of ocean waters, commonly referred to as ocean acidification (OA). Ocean acidification causes declines in calcification, growth and development in many organisms.
However, organisms differ in their tolerance of OA and this variability makes it difficult to predict how OA will shape marine communities in the future without a greater framework of what traits or mechanisms confer tolerance to OA.
I am interested in exploring what traits are associated with tolerance to OA to better predict the acclimation potential of organisms in the future.
Does exposure to variable pH conditions make krill more tolerant of chronic ocean acidification?
Calcareous algae (e.g., coralline algae, Halimeda) are essential on coral reefs: they bind the framework together, increase the strength of the reef, and help protect coastlines from heavy wave action. Coralline algae also facilitate the recruitment of larval corals and mollusks.
Coralline algae are very sensitive to low pH/low saturation water and experience reductions in recruitment, survival, growth, and ability to induce larval settlement.
I explored the potential for coralline algae to acclimate to OA over long time periods by surveying communities at naturally low-pH submarine springs off the coast of Puerto Morelos, Mexico.
Total percent cover, species richness and diversity of calcifying algae were all lower at low saturation levels, however tolerance of acidification varied across genera. Results provide mixed support for the hypothesis that early successional species, characterized by fast growing and thin thalli, are more sensitive to OA than later successional species with thicker thalli.