Hu Chunxiang

Utilization of phosphorus in four forms of the three dominant Microcystis morphospecies in Lake Taihu

Microcystis is the most common bloom-forming cyanobacteria in freshwater. Its ability in phosphorus utilization is considered as a major factor for their dominance. This study chose three dominant Microcystis morphospecies( Microcystis flos-aquae,Microcystis wesenbergii and Microcystis aeruginosa) in the blooms of Lake Taihu,and compared their growth and phosphorus utilization of orthophosphate( K2HPO4),polyphosphate( Na5P3O10),glucose-6-phosphate( G-6-P) and lecithin. The results showed that the three morphospecies represented differences to phosphorus of four forms. Under the concentration of 0. 2 mg / L,M. flos-aquae grew fastest in K2HPO4,while M. wesenbergii had the highest growth rates in Na5P3O10and lecithin. M. aeruginosa showed the lowest growth rates. On contrary,M. flos-aquae had the highest growth rates under the concentration of 2. 0 mg / L. Furthermore, M. wesenbergii showed the highest dissolved inorganic phosphorus rates and photosynthetic activity in terms of Fv/ Fmin both phosphorus concentrations. These results implied that there were variations in phosphorus utilization among the three morphospecies. M. flos-aquae had advantages in phosphorus utilization of different forms under phosphorus-replete conditions,while M. wesenbergii showed advantages at low phosphorus concentration. M. aeruginosa represented the lowest adaptability to phosphorus of different forms. Therefore,the adaptability to available phosphorus of different forms was the competitive strategy for part of Microcystis morphospecies.

On the terrestrialization situation and its driving factors in Lake Nansi

In order to comprehend the terrestrialization situation and its driving factors in Lake Nansi,the whole Lake Nansi and 21 inlets of the rivers entering the lake were sampled and investigated in August 2008,June 2009,August 2009,June 2010 and August 2010.The results showed that only 4 sites located in the Natural Reserve of Weishan Island and the inlet of Jiehe River with dense shipping belonged to no terrestrialization,2 sites lying the inlet of Laowanfu River with busy transport and the open water region of Nanyang Lake to slight terrestrialization,other 6 sites were moderate terrestrialization,12 sites severe terrestrialization and 1 site heavy severe terrestrialization among the 25 sampling sites.The degree of terrestrialization was significantly positively correlated to vegetation types,depth and organic matter content of silt,negatively correlated to pH and dissolved oxygen;the abundance of vegetation was close negatively correlated to depth of water,pH and dissolved oxygen;the silting level was positively to total nitrogen,total phosphorus,organic matter of sediment,negatively to chemical oxygen demand.So apparently the import of exogenous contamination and increase of trophic level promoted the terrestrialization speed,and the unreasonable development in the whole drainage area further accelerated this progress.