Response of seafloor ecosystems to abrupt global climate change

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 15; pp. 4684 - 4689
• Main Authors: Moffitt, Sarah E., Hill, Tessa M., Roopnarine, Peter D., Kennett, James P.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 14.04.2015; National Acad Sciences
• Subjects: Animals; Annelida; Annelida - physiology; Aquatic ecosystems; Arthropods - physiology; Biological oceanography; Biological Sciences; Climate Change; Echinodermata; Echinodermata - physiology; Ecosystem; Foraminifera; Fossils; Geologic Sediments; Global Warming; Invertebrates - classification; Invertebrates - physiology; Lucinoma aequizonatum; Marine; Metazoa; Mollusca - physiology; Mollusks; Oxygen; Oxygen - metabolism; Oxygen Isotopes; Pacific Ocean; Physical Sciences; Population Density; Radiometric Dating; Pacific Ocean; Pacific region; IE, Pacific; metazoans; seafloor ecosystems; deglaciation; abrupt climate change; oxygen minimum zone
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1417130112

Significance This investigation presents the first record to our knowledge of the disturbance and recovery of seafloor ecosystem biodiversity in response to abrupt climate change. Ocean sediments have been extensively studied using geochemical and microfaunal (e.g., Foraminifera) analyses; however, these traditional approaches produce limited interpretations of ecological and community-scale responses. We demonstrate here that ocean sediments harbor metazoan fossil material that can be used to reconstruct the response of seafloor biodiversity to global-scale climate events. We show that the last deglaciation, the most recent episode of climate warming, was accompanied by abrupt reorganizations of continental margin seafloor ecosystems through expansions and contractions of the subsurface low-oxygen zones. This archive reveals that global climate change disturbs seafloor ecosystems on continental margins and commits them to millennia of ecological recovery. Anthropogenic climate change is predicted to decrease oceanic oxygen (O ₂) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria ( Lucinoma aequizonatum ) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats ( Alia permodesta ). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L ⁻¹ [O ₂]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.