Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa
Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa
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大型野生动物的有机物和养分输入影响非洲马拉河的生态系统功能
DOI：
10.1002/ecy.2509
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发表时间：
2018
期刊：
影响因子：
4.8
通讯作者：
Post, David M.
中科院分区：
文献类型：
--
作者：
Subalusky, Amanda L.;Dutton, Christopher L.;Njoroge, Laban;Rosi, Emma J.;Post, David M.
动物可以成为资源跨越生态系统边界移动的重要载体。动物主要通过排泄、排泄和身体向生态系统增加资源，这些输入的化学计量和生物有效性可能与接受者生态系统的特征相互作用，以确定它们对生态系统功能的影响。我们在肯尼亚马拉河研究了河马排泄和角马身体的影响，以及它们与排泄的相互作用。我们测量了野生动物输入的营养物质的溶解和分解速率，输入对河流中营养物质浓度和营养限制的影响，以及输入对两个实验溪流和河流中输入的梯度的生物膜生长和功能的影响。我们发现，河马的排泄增加了河水中的氨氮和粗颗粒有机物，角马的身体增加了氨氮、可溶性活性磷和总磷。水体中溶解碳和营养物质的浓度随着野生动物输入的梯度和低排放期间的增加而增加，尽管颗粒碳的浓度在低排放期间由于沉积在河底而下降。自养生物受到氮的限制，异养生物受到碳的限制，氮和磷在动物投入物的上游受到限制，但在投入物的下游没有营养限制。在实验溪流中，河马和角马的投入共同增加了生物膜总初级生产力(GPP)和呼吸(R)。这些结果在河流中有所不同，低浓度的河马投入增加了生物膜的总初级生产力(GPP)和呼吸(R)，但高浓度的河马投入和角马投入降低了GPP。我们的研究表明，来自大型野生动物的投入缓解了马拉河的营养限制并刺激了生态系统的新陈代谢，这些投入对生态系统的补贴程度受到河流生态系统投入和排放的数量和质量的调节。因此，动物投入物为这条河流提供了重要的生态补贴，在大型野生动物广泛灭绝之前，动物投入物在许多其他河流中可能也很重要。
Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion, and carcasses, and the stoichiometry and bioavailability of these inputs likely interact with characteristics of the recipient ecosystem to determine their effects on ecosystem function. We studied the influence of hippopotamus excretion/egestion and wildebeest carcasses, and their interactions with discharge, in the Mara River, Kenya. We measured nutrient dissolution and decomposition rates of wildlife inputs, the influence of inputs on nutrient concentrations and nutrient limitation in the river and the influence of inputs on biofilm growth and function in both experimental streams and along a gradient of inputs in the river. We found that hippopotamus excretion/egestion increases ammonium and coarse particulate organic matter in the river, and wildebeest carcasses increase ammonium, soluble reactive phosphorus, and total phosphorus. Concentrations of dissolved carbon and nutrients in the water column increased along a gradient of wildlife inputs and during low discharge, although concentrations of particulate carbon decreased during low discharge due to deposition on the river bottom. Autotrophs were nitrogen limited and heterotrophs were carbon limited and nitrogen and phosphorus colimited upstream of animal inputs but there was no nutrient limitation downstream of inputs. In experimental streams, hippo and wildebeest inputs together increased biofilm gross primary production (GPP) and respiration (R). These results differed in the river, where low concentrations of hippo inputs increased gross primary production (GPP) and respiration (R) of biofilms, but high concentrations of hippo inputs in conjunction with wildebeest inputs decreased GPP. Our research shows that inputs from large wildlife alleviate nutrient limitation and stimulate ecosystem metabolism in the Mara River and that the extent to which these inputs subsidize the ecosystem is mediated by the quantity and quality of inputs and discharge of the river ecosystem. Thus, animal inputs provide an important ecological subsidy to this river, and animal inputs were likely important in many other rivers prior to the widespread extirpation of large wildlife.