Mangrove

Mangrove – Effects

 

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[5].

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• Inputs
• Processes
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The effects of nitrogen (N) on a wetland mangrove forest can vary depending on the inputs, processes, stocks and outputs of the wetland.

General

Nitrogen effects content can be found on Pressures page.

Mangrove specific

Increases of N in mangroves will cause increases in N processing, with higher denitrification rates[6][1]. Increase of N loads does not necessarily increase decomposition in mangrove soils[4][2]. However, tipping points of N enrichment in mangroves may result in changes in microbial communities and the reduction of the forest function in mitigating N pollution[6].

Estuarine wetlands have a relatively high capacity for nutrient retention in low and medium flood events and can play a role in protecting the marine environment from land-derived nutrient pollution. However, in the long term, nutrient enrichment may have negative consequences affecting vegetation structure and composition and reducing their capacity for nutrient retention.

Estuarine wetlands are usually limited by nitrogen and/or phosphorus, and nutrient enrichment can enhance plant growth. However, in mangroves, the benefits of increased growth in response to increased nutrient levels can be offset by high mortality rates and slow recovery rates during periods of drought and after tropical storms. This is because nutrients, especially nitrogen, stimulate the growth of shoots at a faster rate than the roots, which causes physical instability of the mangrove trees. The decrease in root biomass can also enhance subsidence of soils, decreasing the capacity of the forest to keep pace with sea level rise[5].

Given the response of mangroves to nitrogen, high nutrient loads delivered in floodwaters to the Great Barrier Reef could be a contributor to the localised dieback of mangrove forests when followed by periods of low rainfall and high salinity or after tropical storms. Nutrient enrichment also has the potential to favour algal blooms in estuarine wetlands, which can smother pneumatophores and seedlings and result in the shift of primary production from a macrophyte to an algae-dominated system. Nutrient enrichment can also change the microbial community in estuarine sediments[3][5].

References

1. ^ Adame, Franklin, H, Waltham, NJ, Rodriguez, S, Kavehei, E, Turschwell, MP, Balcombe, SR, Kaniewska, P, Burford, MA & Ronan, M (2019), 'Nitrogen removal by tropical floodplain wetlands through denitrification', Marine and Freshwater Research, vol. doi.org/10, no. September.
2. ^ Adame, MF, Reef, R, Herrera-Silveira, J & Lovelock, C (2012), 'Sensitivity of dissolved organic carbon exchange and sediment bacteria to water quality in mangrove forests', Hydrobiologia, vol. 691, no. DOI 10.1007/s10750-012-1071-7, pp. 239-253.
3. ^ Eberhard, R, Thorburn, P, Rolfe, J, Taylor, B, Ronan, M, Weber, T, Flint, N, Kroon, F, Brodie, J, Waterhouse, J, Silburn, M, Bartley, R, Davis, A, Wilkinson, S, Lewis, S, Star, M, Poggio, M, Windle, J, Marshall, N, Hill, R, Maclean, K, Lyons, P, Robinson, C, Adame, F, Selles, A, Griffiths, M, Gunn, J & McCosker, K (2017), Scientific Consensus Statement 2017: A synthesis of the science of land-based water quality impacts on the Great Barrier Reef, Chapter 4: Management options and their effectiveness.. [online], State of Queensland, Queensland. Available at: https://www.reefplan.qld.gov.au/about/assets/2017-scientific-consensus-statement-summary-chap04.pdf.
4. ^ Keuskamp, JA, Schmitt, H, Laanbroek, HJ, Verhoeven, JTA & Hefting, MM (2013), 'Nutrient amendment does not increase mineralisation of sequestered carbon during incubation of a nitrogen limited mangrove soil', Soil Biology and Biochemistry. [online], vol. 57, pp. 822-829. Available at: http://dx.doi.org/10.1016/j.soilbio.2012.08.007.
5. ^ a b Lovelock C.E., Ball M.C., Martin K.C. & Feller I.C. (2009), 'Nutrient Enrichment Increases Mortality of Mangrove', PLoS ONE, vol. 4, no. 5, Public Library of Science.
6. ^ a b Molnar, N, Welsh, DT, Marchand, C, Deborde, J & Meziane, T (2013), 'Impacts of shrimp farm effluent on water quality, benthic metabolism and N-dynamics in a mangrove forest ( New Caledonia )', Estuarine, Coastal and Shelf Science. [online], vol. 117, no. 2, pp. 12-21. Available at: http://dx.doi.org/10.1016/j.ecss.2012.07.012.

Last updated: 31 July 2021