Effect of artificial disturbance on coral reef communities : A case study in the Gulf of Thailand

对泰国湾最内侧珊瑚礁的群落结构进行了分析，并与1884年和1987年的考察结果进行了比较，以明确人为干扰的影响。硬底珊瑚群落结构没有明显变化，但以前在软底大量存在的几种孤立珊瑚物种消失了。在下潮间带沙粒明显堆积的区域周围，可以看到大量的死牡蛎壳。在沙滩上，发现沙粒消失了。这些现象似乎是人类活动的结果。河水带来了大量的悬浮物，低盐度效应也很明显。珊瑚礁群落在雨季低潮时盐度为-25，涨潮时为正常海水。定量地估计了低盐度海水和悬浮物对生物活动的影响，其中悬浮物的来源不仅是河水，还有附近的港口建设等。在受人类活动影响的地区和清澈的水域，分析了海绵、被囊类或其他无脊椎动物中积累的有毒物质。分析了有毒物质对珊瑚群落结构的影响，认为低盐度水体中悬浮物较多是珊瑚群落的控制因素，并推测一些人为活动导致悬浮物的增多和水流格局的改变影响了珊瑚群落的结构。

Community structure of the coral reefs in the innermost part of the Gulf of Thailand was analyzed and the results were compared with those collected by our previous expeditions in 1884 and 1987 in order to make clear the effect of anthropogenic disturbance. No marked changes were found in the structure of coral community on hard bottom, but several solitary coral species which had been very abundant on the soft bottom before were observed to disappear. A large number of dead oyster shells were seen around the area where accumulation of sandy particles was conspicuous on the lower intertidal. On a sandy beach, disappearance of the sandy particles was found. These phenomena seemed to be results of some human activities.River water brought huge amount of suspended materials and low salinity effect was also conspicuous. Coral reef communities were covered with <25 of salinity at low tides in the rainy season, while with normal sea water at high tides.Effect of low salinity sea water and suspended materials, of which sources were not only river water but also areas of the construction of a harbor etc.nearby, on biological activities such as filtration by suspension feeders and sediment removal by corals was quantitatively estimated.Toxic materials accumulated in sponges, tunicates or other invertebrates were analyzed in the areas affected by human activities and clear waters. Species composition of these species was different in these areas and effect of toxic materials on coral community structure was discussed.Low salinity water containing much suspension was considered to control the community and it was also speculated that increase of suspended materials and change in current pattern caused by some anthropogenic activities affected its structure.