Sink or link? The bacterial role in benthic carbon cycling in the Arabian Sea's oxygen minimum zone

[摘要] The bacterial loop, the consumption of dissolved organic matter (DOM) bybacteria and subsequent transfer of bacterial carbon to higher trophiclevels, plays a prominent role in pelagic food webs. However, its role insedimentary ecosystems is not well documented. Here we present the resultsof isotope tracer experiments performed under in situ oxygen conditions insediments from inside and outside the Arabian Sea's oxygen minimum zone (OMZ)to study the importance of the microbial loop in this setting. Particulateorganic matter, added as phytodetritus, was processed by bacteria, protozoaand metazoans, while dissolved organic matter was processed only by bacteriaand there was very little, if any, transfer to higher trophic levels withinthe 7 day experimental period. This lack of significant transferof bacterial-derived carbon to metazoan consumers indicates that thebacterial loop is rather inefficient, in sediments both inside and outsidethe OMZ. Moreover, metazoans directly consumed labileparticulate organic matter resources and thus competed with bacteria forphytodetritus.

[学科分类] 地球化学与岩石