Tracking coccolithophore productivity trends over the last 22,000 years: insights from sediments of IODP Expedition 385 in a high-productivity oceanic basin (Guaymas Basin)
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引用次数: 0
Abstract
We study sediment cores retrieved during International Ocean Discovery Program (IODP) Expedition 385 to gain a deeper understanding of the Guaymas Basin's (GB) response to climate fluctuations over the past 22,400 years by analyzing coccolithophore assemblages and estimating net primary productivity (NPP). Coccolithophore-based data and the NPP at IODP Hole 1549 A reveal that the GB consistently remained an area of high productivity throughout the studied time interval, with an average productivity value of 1288.25 mgC m−2 day−1, with a gradually declining trend towards the present.
Three main intervals are defined: (I) Cold, high productivity and vertically mixed surface waters during the Last Glacial Maximum and Heinrich Event 1 (22,400–15,320 cal yr BP), suggested by elevated net primary productivity (NPP), high abundance of Gephyrocapsa oceanica, and the presence of Coccolithus pelagicus subsp. braarudii. These conditions may be related to the incursion of the California Current Water into the GB. (II) Intermittent stratification with a deep position of the nutricline and thermocline during Bølling-Allerød, Younger Dryas, and broadly, the beginning of the Holocene (15,320–11,200 cal yr BP) indicated by an increase in relative abundance of Florisphaera profunda and the decrease in key coccolithophore taxa (notably G. oceanica and C. pelagicus subsp. braarudii). (III) Recurrent events of low productivity, warm surface water conditions with stratification since the beginning of the Holocene Climatic Optimum (11,200 cal yr BP-present), as suggested by the dominance of warm and oligo-mesotrophic water taxa (Helicosphaera spp., Calcidiscus leptoporus, Syracosphaera spp. and Umbilicosphaera sibogae) alongside a rise in F. profunda. From approximately 4900 cal yr BP to the present sustained stratification and declining NPP suggest the onset and intensification of modern monsoonal dynamics in the GB.
期刊介绍:
Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.