Projected expansion of Trichodesmium's geographical distribution and increase in growth potential in response to climate change. (18th September 2020)

• Record Type: Journal Article
• Authors: Boatman, Tobias G.; Upton, Graham J. G.; Lawson, Tracy; Geider, Richard J.
• Is Part Of: Global change biology. Volume 26:Number 11(2020)
• Page Start: 6445
• Page End: 6456
• Publication Date: 2020-09-18
• Subjects: CO2 -- cyanobacteria -- fundamental niche -- growth potential -- ocean acidification -- sea surface temperature -- Trichodesmium; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15324
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Estimates of marine N2 fixation range from 52 to 73 Tg N/year, of which we calculate up to 84% is from Trichodesmium based on previous measurements of nif H gene abundance and our new model of Trichodesmium growth. Here, we assess the likely effects of four major climate change‐related abiotic factors on the spatiotemporal distribution and growth potential of Trichodesmium for the last glacial maximum (LGM), the present (2006–2015) and the end of this century (2100) by mapping our model of Trichodesmium growth onto inferred global surface ocean fields of p CO2, temperature, light and Fe. We conclude that growth rate was severely limited by low p CO2 at the LGM, that current p CO2 levels do not significantly limit Trichodesmium growth and thus, the potential for enhanced growth from future increases in CO2 is small. We also found that the area of the ocean where sea surface temperatures (SST) are within Trichodesmium 's thermal niche increased by 32% from the LGM to present, but further increases in SST due to continued global warming will reduce this area by 9%. However, the range reduction at the equator is likely to be offset by enhanced growth associated with expansion of regions with optimal or near optimal Fe and light availability. Between now and 2100, the ocean area of optimal SST and irradiance is projected to increase by 7%, and the ocean area of optimal SST, irradiance and iron is projected to increase by 173%. Given the major contribution of this keystone species to annual N2 fixation and thus pelagic ecology, biogeochemistry and CO2 sequestration, the projected increase in the geographical range for optimal growth could provide a negative feedback to increasing atmospheric CO2 concentrations. Abstract : Between now and 2100, the ocean area of optimal SST and irradiance for Trichodesmium growth is projected to increase by 7%, and the ocean area of optimal SST, irradiance and iron is projected to increase by 173%. Given the major contribution of Trichodesmium to annual N2 fixation and thus pelagic ecology, biogeochemistry and CO2 sequestration, the projected increase in the geographical range for optimal growth could provide a negative feedback to increasing atmospheric CO2 concentrations.