Photosynthetic and bacterial production rates of 20 study ponds

Table 2. 
Photosynthetic and bacterial production rates of 20 study ponds. Mean values (n = 4) with SD in brackets.
Abstract We compared planktonic primary and secondary production across twenty meltwater ponds on the surface of the McMurdo Ice Shelf in January 2007, including some ponds with basal brines created by meromictic stratification. Primary production ranged from 1.07 to 65.72 mgC m−3 h−1 in surface waters. In stratified ponds primary production was always more than ten times higher in basal brines than in the corresponding mixolimnion. Regression tree analysis (r2 = 0.80) identified inorganic nitrogen (as {\mathrm{NH}}_{4}^{+}) as the main factor limiting planktonic primary production. However, there was also evidence of inorganic carbon co-limitation of photosynthesis in some of the more oligotrophic waters. Neither C nor N limited carbon fixation at [NH4–N] > 50 mg m−3, with photoinhibition the factor most likely limiting photosynthesis under such conditions. Primary production was the only factor significantly correlated to bacterial production and the relationship (r2 = 0.56) was non-linear. Nitrogen limitation and tight coupling of planktonic primary and bacterial production is surprising in these ponds, as all have large pools of dissolved organic carbon (1.2–260 g m−3) and organic nitrogen (all >130 mg m−3). The dissolved pools of organic carbon and nitrogen appear to be recalcitrant and bacterial production to be constrained by limited release of labile organics from phytoplankton.

表 2. 20 个研究池塘的光合作用和细菌生产速率。均值（n=4）及其标准差（SD）列于括号内。
摘要：本研究于 2007 年 1 月在麦克默多冰架表面的 20 个融水池塘中，对比了浮游生物初级和次级生产率，其中部分池塘因层状分层作用形成了底层卤水。初级生产率在表层水中波动于 1.07 至 65.72 mgC m−3 h−1 之间。在分层池塘中，底层卤水的初级生产率始终高于对应混合层十倍以上。通过回归树分析（r2=0.80），无机氮（以NH4+计）被确认为限制浮游生物初级生产的主要因素。然而，在一些较为贫营养的水体中，也出现了无机碳对光合作用的共限制的证据。当 [NH4–N] > 50 mg m−3 时，碳固定不受 C 或 N 的限制，光抑制可能是这种条件下限制光合作用的因素。初级生产率是唯一与细菌生产率显著相关的因素，其关系（r2=0.56）呈非线性。在这些池塘中，氮限制以及浮游生物初级与细菌生产的紧密耦合令人惊讶，因为所有池塘都拥有大量的溶解有机碳（1.2–260 g m−3）和有机氮（所有 >130 mg m−3）。溶解的有机碳和氮库似乎具有抗性，而细菌生产则受到从浮游植物中有限释放易变性有机物的制约。