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

本研究的目的是评估热带泻湖海草床和海藻中碳和氮的循环及其与生物群落代谢的耦合，我们在斐济苏瓦南部的热带泻湖进行了广泛的实地观察。 1994-1996年间，泻湖内有茂密的紫丁香海床，海草床周围也有海藻种群。(1)结合现有的航空照片和我们的实地观测数据，近3年的实地观测也证实了德拉乌尼岛附近海草床的面积在过去20年中扩大了约6倍。海草床向岸边扩展了22m，岛上人口约100人，在过去20年里相当稳定，但该村配备了井供水系统约5-6年。以前海草增加的可能原因是由于用水量的增加而导致岛上营养负荷的变化。（2）随着海草床的变化，我们发现海鞘等表底生物群落分布的变化。其中一些动物含有共生藻类，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海草床和哈利梅达小规模分布的重要因素。 (3) 各种生物群落中的 15-N 和 13-C 稳定同位素混合物以及海草床及其附近的悬浮有机物质利用这两种 13 的显着差异，为该生态系统中的食物网结构提供了一些有趣的见解。海草及其附生藻类中的 C 和 15-N 定量，部分归因于蓝绿藻的固氮作用，丝状藻被认为是海洋生物的主要食物来源底栖动物和其他底栖动物的丝状蓝绿的活性固氮作用也通过 C2H2 方法得到了实验证实。