Restoration of an ecosystem in the eutrophicated shallow estuary -dynamics of environments and benthic fauna at the experimental artificial tidal flat-

本文于2000年6月至2003年9月在日本大阪湾汉南二区人工潮滩和南子鸟类保护区北塘对底栖动物区系和氮、悬浮物、叶绿素a等物质的平衡进行了研究。汉南二区人工滩地底栖生物种类和数量随着时间的推移而增加，与日本河口富营养化的其他人工和（或）天然滩地相比，底栖生物的种类和数量趋于相当或丰富。南湖鸟类保护区北塘向海岸水体输出的悬浮物量大于向塘内输入的悬浮物量，而叶绿素a则通过潮汐交换在塘内被截留。进入池塘的溶解无机氮被暂时吸收到生物量中，然后以溶解有机氮的形式出口。2001年夏季，颗粒态氮作为一种含氮养分资源在沿海水体中较为丰富。这些现象被认为与底栖动物、海藻和微藻的摄食、固定和分解等生物活动有关。2000 ~ 2003年，汉南二区人工潮滩的净氮交换发生了显著变化。2000年9月，在人工潮滩建成仅5个月后，氮以5.39 kg N/d的速率从人工潮滩向邻近水域释放。人工潮滩在2001年9月和2002年9月对海藻生长表现出氮汇的作用，而在2003年10月对海藻减少表现出氮源的作用。结果表明，优势种海藻在2001年9月和2002年9月对氮的吸收量分别达到4.8和3.3 kgN/d，分别占人工潮滩一天总固氮量的102和92%。

Benthic fauna and budgets of materials such as nitrogen, suspended solids and chlorophyll a were studied from June 2000 to September 2003 at the north pond of Nanko Bird Sanctuary and at an artificial tidal flat of Hannan Second District, Osaka Bay, Japan. Species and numbers od benthic organisms increased with time course at the artificial tidal flat of Hannan Second District, and its fauna became equivalent or rich compared to other artificial and/or natural tidal flats of the eutrphicated estuary of Japan. At the north pond of Nanko Bird Sanctuary, the output of suspended solids to coastal water exceeded its input to the pond, while chlorophyll a was intercepted within the pond through the tidal exchange. Dissolved inorganic nitrogen imported into the pond was temporally incorporated into the biomass and was then exported in the form of dissolved organic nitrogen. Particulate nitrogen was abundant as a resource of nitrogenous nutrients to coastal water in the summer of 2001. These phenomena are thought to be correlated with biological activities such as feeding, fixation and decomposition by benthic animals, seaweeds and microalgae. At the young artificial tidal flat, Hannan Second District, the net exchange of nitrogen significantly changed between 2000 and 2003. In September 2000 only five months after its construction, nitrogen was released from the artificial tidal flat to the adjacent waters at a rate of 5.39 kg N/day. In contrast, the artificial tidal flat functioned as a site of sink for nitrogen in relation to the growth of seaweeds in September of 2001 and 2002, but played as a source of nitrogen in accordance with seaweed decrese in October 2003. As a result, nitrogen uptake by the dominant species of seaweeds in Septembers 2001 and 2002 reached 4.8 and 3.3 kgN/day which accounted for 102 and 92% of the total nitrogen fixed at the artificial tidal flat within one day.