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A comparative study of materials flows between seagrss-and seaweed-based ecosystemes in tropical lagoon.

热带泻湖海草和海藻生态系统物质流的比较研究。

基本信息

批准号：
06041028
负责人：
KOIKE Isao
金额：
$ 10.88万
依托单位：
University of tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

The Purpose of this study is to evaluate the cycling of carbon and nitrogen and their coupling with the metabolisms of biological communities in seagrass beds and in seaweeds in tropical lagoon. We made an extensive field observation in the tropical lagoon located at south of Suva, Fiji from 1994-1996. In the lagoon, there is a dense Syringodium seagress bed and also Halimeda population around the seagrass bed. Following are the some outcomes from the field survey.(1) Combing with the available data of aero-photographs and our field observation, the seagrass bed near the Dravuni Island expanded their size to about 6 times during the last 20 years. This increase in size was also confirmed for the latest 3 years field observation, indicating 22m expansion of seagrass bed to the shore side. The island has a population of some 100 peoples, which is rather stable during the last 20 years. But, the village equipped water supply system from the well about 5-6 years ago. Possible reason for th … More e seagrass increase is the change of nutrients load from the island due to the increase of water usage.(2) Together with the change of seagrass bed, we found the change of epibenthic community distribution such as Ascidians and Lagenophyra. Some of those animals harbor symbiotic alage, which are significant primary producers in the tropical lagoon. The symbiotic character of those animals seems to be important factor controlling the small scale distribution with in seagrass bed and Halimeda communities.(3) Stable isotope analyzes of 15-N and 13-C in various biological communities and suspended organic materials in the seagrass bed and its vicinity gave some interesting insight of food web structure in this ecosystem. Using the significant difference in both 13-C and 15-N rations in seagrass and their epiphytic algae, which are partially due to the nitrogen fixation by blue green algae, filamentous algae was suggested as a primary food source of epibenthic and other benthic animals. Active nitrogen fixation by filamentous blue green was also confirmed experimentally using C2H2 method. Less

本研究旨在探讨热带泻湖海草床和海藻中碳氮的循环及其与生物群落代谢的耦合关系。1994-1996年，我们在斐济苏瓦南部的热带泻湖进行了广泛的实地观测。在泻湖中，有密集的海草床和海草床周围也有海蝇种群。以下是实地调查的一些结果。(1)结合航空摄影资料和野外观测资料，近20年来，德拉武尼岛海草床面积扩大了约6倍。最近3年的野外观测也证实了这种规模的增加，表明海草床向岸边扩展了22米。该岛人口约有100人，在过去20年中相当稳定。但是，该村在大约5-6年前从井中安装了供水系统。海草增加的可能原因是由于用水量的增加，岛上的营养负荷发生了变化。(2)随着海草床的变化，海鞘类和绳生类等底栖生物群落的分布也发生了变化。其中一些动物体内有共生藻类，它们是热带泻湖中重要的初级生产者。这些动物的共生特征似乎是控制其在海草床和海藻类群落中小尺度分布的重要因素。(3)对海草床及其附近各生物群落和悬浮物中的15-N和13-C的稳定同位素分析，对该生态系统的食物网结构提供了一些有趣的认识。根据海草及其附生藻类中13-C和15-N含量的显著差异（部分原因是蓝绿藻的固氮作用），丝状藻类可能是附生动物和其他底栖动物的主要食物来源。采用C2H2法也证实了丝状蓝绿的活性固氮作用。少