FILTERING EFFECT OF SUSPENDED MATTER AND ORGANIC CARBON BY THE LENA RIVER DELTA, RUSSIAN ARCTIC

The Arctic Ocean receives the main portion of water (525 km3/year) and suspended sediment (17.6 t6/year) through the Lena River, the eighth largest in the world in terms of water discharge. The Lena River is also responsible for transporting large amounts of dissolved and particulate material onto the Arctic. Of these important contributors of freshwater to the Arctic, the Lena also supplies major quantities of nutrients. From this point of view, understanding of the export of bio-related components to the Arctic is a critical but insufficiently understood component of global carbon cycles especially due to very limited data about real export of dissolved and particulate loads to the Arctic. Monitoring stations are usually located hundreds kilometers upriver and a very limited number of stations are situated near river’s terminus, while the export of bio-related components to the seas is largely affected by estuaries or deltas. Reference gauge at Kusur Village that is usually used for calculations of Lena River carbon and nutrients loads is located 300 km upstream. A huge delta, more then 200 km wide with numerous branches traps suspended matter and its export to the Arctic is still unknown (Ivanov, Piskun 1999).

Here, we present new results that reveal data about the filtering effect of Lena Delta on particulate loads. Seven ADCP, CTD and water stations were performed from a stationary gauge at Kusur down the major branches of the delta to river’s terminus at Bukovskyi Cape (12-13 July 2003). Based on our data we conclude that the concentrations and fluxes of suspended and dissolved bio-related components are not uniform down the delta and exhibit significant fluctuations. Final export of some components to the Arctic decreased or increased several times for comparison with the gauge at Kusur. The flux of total suspended matter increased to 1.26 times before entering to the Laptev Sea. Fluxes of phyaoephyptin increased to 3.5 times, while fluxes of particulate Norg, Pinorg, Porg, Corg decreased to 5.8, 3.3, 1.8, 1.3 times correspondently. Our data provides information for revision of the annual export of particulate and dissolved bio-related components from the Lena River to the Arctic.