Mechanisms for Organic Matter and Phosphorus Burial in Sedimentsof a Shallow, Subtropical, Macrophyte-Dominated Lake |
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| Authors: | Mark Brenner David A Hodell Barbara W Leyden Jason H Curtis William F Kenney Binhe Gu Jana M Newman |
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| Institution: | (1) Department of Geological Sciences and Land Use and Environmental Change Institute (LUECI), University of Florida, Gainesville, Florida 32611, USA;(2) Department of Geological Sciences, University of South Florida, Tampa, Florida 33620, USA;(3) Everglades Division, South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, Florida 33406, USA |
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| Abstract: | We studied the role that submersed aquatic vegetation (SAV) plays in the sedimentation of organic matter (OM) and phosphorus
(P) in Lake Panasoffkee, Florida (USA), a shallow, hard-water, macrophyte-dominated water body. Carbon/Nitrogen ratios (C/N)
and stable isotope signatures (δ13C and δ15N) in algae, higher plants, and surface sediments were measured to identify sources of OM to the lake mud. Pollen, plant macrofossils,
and geochemistry in sediment cores indicated that primary productivity and SAV abundance in Lake Panasoffkee increased in
the late 1800s, probably as a response to increased P loading from human settlement and forest clearance. SAV and associated
periphyton served as temporary sinks for soluble P, maintaining relatively clear-water, low-nutrient conditions in the lake.
P accumulation in Lake Panasoffkee sediments increased together with indicators for greater SAV presence. This suggests that
SAV and associated epiphytes promote P burial and retention in sediments. Although it might be assumed that rooted submersed
macrophytes are directly responsible for P uptake from water and transfer to sediments, C/N and stable carbon isotope results
argue for the importance of other macrophyte growth forms, and perhaps epiphytic algae, in permanent OM and P sequestration.
For instance, high rates of photosynthesis by epiphytes in hard-water systems consume CO2 and promote CaCO3 precipitation. Sloughing of accumulated carbonates from macrophyte leaves transfers epiphytes and associated P to the sediment.
Our paleolimnological findings are relevant to restoration efforts in the Florida Everglades and support the claim that constructed
SAV wetlands remove P from waters effectively. |
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| Keywords: | Macrophytes Nutrients Organic matter Phosphorus Sediment Shallow lakes Stable isotopes Submersed aquatic vegetation |
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