Lacustrine

Lacustrine – Stocks

 

The conceptual models were compiled by researchers in collaboration with a wide range of stakeholders from Natural Resource Management groups, universities and government agencies and based on available scientific information[2].

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• Overview
• Inputs
• Processes
• Stocks
• Outputs
• Effects
• Management
• Links and References

Nitrogen (N) stocks in lacustrine wetlands (lakes) are relatively low to intermediate, and are mostly concentrated at the edges of the lake, where macrophytes are present or in the form of floating macrophytes, which can form very dense clusters, or stored as sediment in the bottom of the lake. Nitrogen can be stored in phytoplankton but this is highly variable depending on the trophic status of the lake.

Soils and sediments

The N stock in lakes is primarily in the sediments at the bottom of the lake and has been reported at approximately 6,111 (0-31,300) kg/ha^*[4].

Vegetation

Macrophytes can account for a significant N stock in vegetated portions of the lake (32 (2-62) kg/ha)^*[1], especially in lakes that contain weeds where they can have up to 288 kgN/ha[2]. The biofilm on top of the macrophytes can account for about 2% of the total N stock[2]. The N stocks in lakes however, are highly variable, as they can be flushed out of the system, or die and decompose in the bottom of the lake, so they can only be considered a short-term N sink.

Trees surrounding the lake will provide long-term storage, but most of the vegetation storage of nitrogen will be at the edges of the lake, in the shallower parts.

Biota

Lakes are likely to have variable stocks of N, in part, due to the mobility of fauna, including crocodiles (in north Queensland), turtles, fish and birds, which store nitrogen in their tissues.

Water

Dissolved N in the water column is rapidly taken up and processed by microbes (a microbial loop) and doesn't form a long-term stock. See vegetation above[3].

^*_{Nitrogen quantities are displayed as an average followed by a minimum and maximum (range), e.g. “average (min. of range - max. of range) units”.}

References

1. ^ Finlayson, CM (1991), 'Production and major nutrient composition of three grass species on the Magela floodplain, Northern Territory, Australia', Aquatic Botany, vol. 41, pp. 263-280, Elsevier.
2. ^ a b Houston, WA & Duivenvoorden, LJ (2002), 'Replacement of littoral native vegetation with the ponded pasture grass Hymenachne amplexicaulis: effect on plant, macroinvertebrate and fish biodiversity of backwater in the Fitzroy River, Central Queensland, Australia', Marine and Freshwater Research, vol. 53, pp. 1235-1244.
3. ^ Lewis, WM (1996), 'Tropical lakes : how latitude makes a difference', Perspectives in Tropical Limnology, p. 43, SPB Academic Publishing, Amsterdam, The Netherlands, eds. F Schiemer & K T Boland.
4. ^ Waterhouse, J, Schaffelke, B, Bartley, R, Eberhard, R, Brodie, J, Star, M, Thorburn, P, Rolfe, J, Ronan, M, Taylor, B & Kroon, F (2017), 2017 Scientific Consensus Statement. Land use impacts on Great Barrier Reef water quality and ecosystem condition, Australia.

Last updated: 2 August 2021