Factors controlling the flux of organic carbon to the bathypelagic zone of the ocean

TLDR

Particle fluxes measured with time‑series sediment traps deployed below 2000 m at 68 world‑ocean sites were combined with satellite‑derived export production estimates to assess factors controlling particulate organic matter transfer from surface to deep water. Multiple linear regression derived an algorithm indicating that organic‑carbon transfer efficiency, defined as settling flux normalized to export production, increases with carbonate flux and decreases with water depth and seasonality. The algorithm explains over 80 % of the variability in transfer efficiency, revealing that carbonate ballasting enhances export while depth, seasonality, and the absence of opal ballasting reduce efficiency, resulting in higher remineralization in high‑latitude, opal‑dominated regions and greater deep‑sea export in warm, carbonate‑dominated low‑latitude areas.

Abstract

Particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite‐derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water. Multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon, defined as the settling flux of organic carbon normalized to export production, increases with the flux of carbonate and decreases with water depth and seasonality. The algorithm predicts >80% of the organic carbon transfer efficiency variability in diverse oceanic regions. The influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles. However, the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role. The adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events. In high latitude opal‐dominated regions with high f ‐ratios and seasonality, while a higher fraction of net production is exported, a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths. On the other hand, in warm, low latitude, carbonate‐dominated regions with low f ‐ratios and seasonality, a higher fraction of the exported organic matter sinks to the deep sea.