菹草种群内外水质日变化

对菹草(Potamogeton crispus)种群内外水体进行了昼夜连续监测,分析菹草种群内外水质的日变化趋势.结果显示,种群内DO自日出后增加,日落后持续下降,且与水温变化一致,于19:30左右出现1次明显低谷,后略有恢复,后一直降至日出前后；开阔水域DO变化与水温呈现一定相关性,但变化幅度较小；交界处DO含量兼有种群内与开阔水域的变化特点.种群内水体pH值自日出前后升高,日落时达最高值,后开始下降,直至次日出前后；交界处与种群变化趋势一致；开阔水域pH总体变化幅度较小,白天高于夜间,总体DO含量及pH分布:种群区＞交界处＞开阔水域.种群及交界处TN含量均在日出前后达最高,日出后递减,开阔水域夜间含量较高,日出前后达最高；各点NH+4-N变化规律不显著；种群内水体TP含量夜间较高,日出前后达最高值,日出后递减,日落后递增；开阔水域TP含量夜间较高,白天略低；交界处正午前后达最低值,傍晚达最高值,TN、TP总体分布:种群＜交界处＜开阔水域.菹草种群存在对水体DO、pH等环境因子均产生重要影响,继而影响水体内源性氮磷的迁移,其中对pH影响较小,其变化未能影响水体氮磷迁移,而DO昼夜变化较大,对水体内源性氮磷的迁移起重要影响.

Diurnal variation of water quality around Potamogeton crispus population

A nychthemeron monitoring was performed around the Potamogeton crispus population in order to study the diurnal variation of water quality around Potamogeton crispus population. Result showed that, within the waters containing Potamogeton crispus population, the dissolved oxygen (DO) concentration increased from sunrise and droped continuously after sunset, following the water temperature variation. DO declined particularly apparently in the evening around 19:30, experienced a short-term recovery and then decreased until sunrise. The DO concentration within the open waters significantly correlated with water temperature variation; the DO variation tendency in the the boundary waters had the characters of that both for population-contained and open waters.The pH value within the population area increased after sunrise, and reached the highest at sunset, and then declined until sunrise on the following day, which was similar with that in the boundary waters; the pH values in the open waters area showed unobvious diurnal tendency. The DO concentration and pH value distribution followed this pattern: population area > boundary area > open waters. The total nitrogen (TN) content in the population and boundary area was highest around the sunrise and then decreased gradually, while the TN content at the open waters in the night was higher than in the day, and the highest TN content appeared at sunrise. The NH₄⁺-N content variation showed no significant diurnal changes. The total phosphorus (TP) content with the population-contained area was more in the evening than in the day. The TP content reached the highest value at the sunrise, dropped rapidly, and then increased after sunset. The TP content in the open waters is higher in the evening than that in the day, with the lowest value appearing at the midday and highest value at dusk. Both TN and TP showed following distribution patterns: population area < boundary area < open waters. Potamogeton crispus had an important impact on DO, pH, and other water environmental factors, which in turn affected the migration of the endogenous nitrogen and phosphorus. Potamogeton crispus population had no significant effect on both pH value and the migration of nitrogen and phosphorus. Moreover, diurnal variation of DO had greater impact on the migration of endogenous nitrogen and phosphorus compared to photosynthesis.