Interaction of sinking behaviour of Saharan dust and lithogenic and biogenic fluxes in the Canary Basin

Abstract

Saharan dust events are currently the predominant source of lithogenic particles in the Canary Basin. In order to quantify this input and its relationship with the biogenic fluxes, a sediment trap was deployed in a free-drifting system at 150 m depth, 50 km off the north coast of Gran Canaria (Canary Islands). The mineralogy of the lithogenic particles included illite, calcite, hematite quartz, barite and kaolinite. The biogenic matter was composed of chitin, transparent exopolymer particles, and carbonates from foraminifera and gastropod shells. The average Saharan dust flux over the ocean surface was approximately 5±4 mg m–2 day-1. The lithogenic, carbonate and chitin fluxes were 0.8±0.6, 6.0±7.4 and 154±386 mg m–2 day-1, respectively. A fairly strong Saharan dust event during sampling was observed in the trap, with a delay of three days in the peaks of lithogenic and biogenic fluxes. The theoretical settling velocity of the lithogenic particles associated with Saharan dust events at 150 m depth was vStokes=275 m day-1, and the experimental settling was about 50 m day-1. The associated sinking behaviour of particulate organic carbon and biogenic and lithogenic fluxes observed in this study may contribute to a more realistic prediction of these fluxes in carbon biological pump models.

The δ13C, δ18O and Δ47records in biogenic, pedogenic and geogenic carbonate types from paleosol-loess sequence and their paleoenvironmental meaning

“…The origin and time-integration of geogenic carbonate isotopic compositions may be more difficult to ascertain. Geogenic carbonates found in paleosol-loess sequences may record formation temperatures of minerals in the deflation area from which dust was sourced, where the minerals may have been formed through a variety of geological processes, including metamorphism (Catoni et al, 2012; Baez-Hernandez et al, 2019). Therefore, various carbonate types—even located in the same stratigraphic level in a paleosol-loess sequence—may record a mixture, but specific and potentially complementary environmental information based on differences in δ 13 C, δ 18 O, and Δ 47 values.…”

Plankton Community Changes From Warm to Cold Winters in the Oligotrophic Subtropical Ocean

“…The year 2010 was a period of more intense dust events in recent years , and March 2010 showed the highest deposition ( Figure 3A). Dust transported significant concentrations of iron, aluminum and manganese as measured during the same events (see Jaramillo-Vélez et al, 2016;Menéndez et al, 2017;Báez-Hernández et al, 2019) and promote some nutrient stress relief (Neuer et al, 2004). The strong stratification of the water column during winter 2010 limited the replenishment of nutrients to the euphotic layer.…”