Comparison of carbon production and decomposition, benthic nutrient fluxes and denitrification in seagrass, phytoplankton, benthic microalgae- and macroalgae-dominated warm-temperate Australian lagoons
Comparison of carbon production and decomposition, benthic nutrient fluxes and denitrification in seagrass, phytoplankton, benthic microalgae- and macroalgae-dominated warm-temperate Australian lagoons
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DOI：
10.3354/meps229043
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发表时间：
2002-01-01
影响因子：
2.5
通讯作者：
Ferguson, AJP
中科院分区：
文献类型：
--
作者：
Eyre, BD;Ferguson, AJP
代表不同阶段的富营养化的海洋植物碳的分解和生产，底栖营养盐通量和反硝化作用的影响进行了研究，在4浅暖温带澳大利亚泻湖。碳生产和分解的差异，在整个泻湖的数量和质量的底栖营养盐通量和氮的相对比例，通过反硝化损失的主要监管机构。例如，泻湖沉积物以N-2形式再循环氮的效率（即反硝化效率：N-2-N/（N-2-N+DIN））随着碳分解速率的增加而降低，某些植物-沉积物系统中矿化有机物的C：N比远高于占主导地位的碳供应的化学计量学所预期的。暗DON通量也非常高，在所有的植物沉积物系统（30至80%的总氮通量）。我们提供了2个替代的解释所观察到的沉积物和底栖通量特征：（1）低暗C：N比的矿化有机质可能是由于暗吸收底栖微藻和可能的其他植物。大DON流出物是新鲜产生的原位有机材料的水解产物或/和与底栖微藻的放牧。这种解释具有重要意义的重要性，底栖微藻类作为氮汇。(2)或者，高C：N比的矿化有机物可能已直接关系到大溶解有机氮（DON）流出;大DON流出低C：N比增加C：N比的有机物在表层沉积物中，这反过来又会导致氮的吸收和积累的细菌由于微生物分解的N-限制。生产的所有植物组底栖营养盐通量有显着的影响，在黑暗周期和吸收在光周期期间的流出的典型模式。因此，沉积物的生产力/呼吸（P/R）的比率是一个主要的控制（最好的指标）净底栖无机和有机营养盐通量，似乎是一个关键的变化发生在浅水沿海泻湖，因为这些成为富营养化。这具有重要的管理意义，表明需要维持底栖动物自养和异养的平衡。的鲁棒性的反硝化效率和沉积物P/R的关系，在这样一个不同的范围内的植物-沉积物系统，代表不同阶段的富营养化表明，这些可能是有用的，在合成反硝化和底栖生物通量数据在浅水海岸系统，并在定义合适的碳负荷率。
The influence of marine plants representing different stages of eutrophication on carbon decomposition and production, benthic nutrient fluxes and denitrification was examined in 4 shallow warm-temperate Australian lagoons. Differences in carbon production and decomposition across the lagoons were the main regulators of the quantity and quality of benthic nutrient fluxes and the relative proportion of nitrogen lost through denitrification. For example, the efficiency with which the lagoon sediments recycled nitrogen as N-2, (i.e. denitrification efficiency: N-2-N/(N-2-N+DIN), decreased as carbon decomposition rates increased, C:N ratios of the remineralised organic matter in some of the plant-sediment systems were much higher than expected from the stoichiometry of the dominant carbon supply. Dark DON fluxes were also very high in all the plant-sediment systems (30 to 80% of the total nitrogen flux). We offer 2 alternative explanations for the observed sediment and benthic flux characteristics: (1) The low dark C:N ratios of the remineralised organic matter may have been due to dark uptake by benthic microalgae and possibly other plants. The large DON effluxes were either the hydrolysis product of freshly produced in situ organic material or/and associated with the grazing of benthic microalgae. This explanation has important implications regarding the importance of benthic microalage as a sink for nitrogen. (2) Alternatively, the high C:N ratios of the remineralised organic matter may have been directly related to the large dissolved organic nitrogen (DON) effluxes; large DON effluxes with a low C:N ratio increase the C:N ratio of organic matter in the surface sediments, which in turn causes an uptake and accumulation of nitrogen by bacteria due to N-limitation of the microbial decomposition. Production by all the plant groups had a significant influence on benthic nutrient fluxes, with a typical pattern of an efflux during the dark cycle and an uptake during the light cycle. As such, the sediment productivity/respiration (p/r) ratio was one of the major controls on (best indicators of) net benthic inorganic and organic nutrient fluxes and appears to be one of the key changes which occur in shallow coastal lagoons as these become eutrophic. This has important management implications, demonstrating the need to maintain the balance of benthic autotrophy and heterotrophy. The robustness of the denitrification efficiency and sediment p/r relationships across such a diverse range of plant-sediment systems that represent the different stages of eutrophication suggests that these may be useful in synthesising denitrification and benthic flux data across shallow coastal systems and in defining suitable carbon loading rates.