They Ng H, Amado André M, Cotner James B
Graduate Program in Ecology, Limnology Laboratory, Department of Oceanography and Limnology, Universidade Federal do Rio Grande do NorteNatal, Brazil.
Department of Biology, Universidade Federal de Juiz de ForaJuiz de Fora, Brazil.
Front Microbiol. 2017 Aug 8;8:1505. doi: 10.3389/fmicb.2017.01505. eCollection 2017.
The canonical Redfield C:N:P ratio for algal biomass is often not achieved in inland waters due to higher C and N content and more variability when compared to the oceans. This has been attributed to much lower residence times and higher contributions of the watershed to the total organic matter pool of continental ecosystems. In this study we examined the effect of water residence times in low latitude lakes (in a gradient from humid to a semi-arid region) on seston elemental ratios in different size fractions. We used lake water specific conductivity as a proxy for residence time in a region of Eastern Brazil where there is a strong precipitation gradient. The C:P ratios decreased in the seston and bacterial size-fractions and increased in the dissolved fraction with increasing water retention time, suggesting uptake of N and P from the dissolved pool. Bacterial abundance, production and respiration increased in response to increased residence time and intracellular nutrient availability in agreement with the growth rate hypothesis. Our results reinforce the role of microorganisms in shaping the chemical environment in aquatic systems particularly at long water residence times and highlights the importance of this factor in influencing ecological stoichiometry in all aquatic ecosystems.
与海洋相比，由于内陆水体中碳和氮含量较高且变异性更大，藻类生物量的经典雷德菲尔德碳氮磷比往往无法实现。这归因于大陆生态系统中水体停留时间短得多，以及流域对总有机质库的贡献更大。在本研究中，我们研究了低纬度湖泊（从湿润地区到半干旱地区的梯度）的水体停留时间对不同粒径级分中悬浮颗粒元素比的影响。在巴西东部一个降水梯度较大的地区，我们使用湖水比电导率作为停留时间的替代指标。随着水体停留时间的增加，悬浮颗粒和细菌粒径级分中的碳磷比下降，溶解级分中的碳磷比上升，这表明从溶解态库中吸收了氮和磷。细菌丰度、生产力和呼吸作用随着停留时间和细胞内养分可利用性的增加而增加，这与生长率假说一致。我们的结果强化了微生物在塑造水生系统化学环境中的作用，特别是在水体停留时间长的情况下，并突出了这一因素在影响所有水生生态系统生态化学计量学方面的重要性。
