Internal Controls of Carbon Dynamics in Lake Malawi

Session: 27. - Emerging Partnerships, Research, and Capacity in the African Great Lakes

Harvey Bootsma, University of Wisconsin-Milwaukee, [email protected]
Robert Hecky, Editor, Journal of Great Lakes Research, [email protected]
Maxon Ngochera, Monkey Bay Fisheries Research Station, [email protected]

Abstract

In deep, tropical lakes carbon and nutrient dynamics are regulated to a large degree by internal cycles. Understanding of these cycles is necessary for determining the productive capacity of these systems, their role in regional carbon budgets, and interpretation of their long sedimentary records.  We present data on the fluxes and distributions of carbon, nitrogen, phosphorus and silica obtained during a three-year study.  Nutrient profiles indicate that a large fraction of sinking particulate material is recycled within the deep hypolimnion.  However, the presence of an oxic/anoxic interface at ~220 m inhibits the upward flux of both N and P, due to denitrification and P precipitation.  This nutrient “trap” appears to more efficiently remove N than P, but high external N:P loading ratios prevent the lake from becoming strongly N limited.  Within the anoxic hypolimnion, P appears to be recycled more efficiently than C, and sediment C:P ratios suggest that the lake is very efficient at utilizing P to form organic C.  Nutrient profiles and sediment C:P:Si ratios suggest that organic C burial rates may be dictated by Si availability.

1. Keyword
Africa

2. Keyword
Lake Malawi

3. Keyword
carbon

4. Additional Keyword
phosphorus

5. Additional Keyword
nitrogen

6. Additional Keyword
silica