Elemental Acquisition in Humic Lakes Implications for Ecosystem Structure and Function

ELEMENTAL ACQUISITION IN HUMIC LAKES IMPLICATIONS FOR ECOSYSTEM STRUCTURE AND FUNCTION 

Bacteria are known to outcompete algae for the uptake of available P in P-limited systems (Currie and Kalff, 1984). The greater ability of the bacterial community to acquire P has also been demonstrated in a small humic lake (Salonen et al., 1994). Bacteria tend to dominate in terms of both biomass and production in humic lakes (Tranvik, 1989 Hessen, 1992) and are likely the most important mobilizers of both Fe and P in these systems. 

Given how the DOM-Fe-P complex influences ecosystem structure, it is also likely that the DOM-Fe-P complex influences humic lake ecosystem function in terms of C metabolism. First, the bacterial conversion of dissolved C into biomass it is quite low, with an average of 25 % across a trophic gradient (del Giorgio et al., 1997). And despite the evidence that bacteria may be better equipped to acquire the Fe and P bound to DOM, the added energetic expenditure in acquiring these elements may result in a significant 

The authors thank Drs. Stuart Findlay, Bob Sinsabaugh, and Robert Wetzel for encouragement. Special thanks is extended to Dr. Michael Pace for useful discussions and helpful criticism. Comments from an anonymous reviewer were also greatly appreciated. RM and MJP were supported by postdoctoral fellowships from NSERC of Canada and the NSF Earth Sciences division, respectively. 

Anderson, M. A., and F. M. M. Morel. 1980. Uptake of Fe (II) by a diatom in oxic culture medium. Marine Biology Letters 1 263—268. 

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