Analysis of Aquatic Ecosystem Response for Zone Management of Ban Pho Town, Chachoengsao Province, Thailand

Abstract

This research was carried out in the Ban Pho Town ship, Chachoengsao Province in the eastern part of Thailand, an important area for aquaculture. The objectives of the study were to assess the aquatic status and its potential carrying capacity for pollution and to understand the ecosystem response to human and natural impacts leading to a proposal for an appropriate zone management approach for sustainable utilization of the area. Information on community-based utilization patterns was obtained through surveys using questionnaires. Field conditions were monitored by 2-monthly surveys from August 2004 to August 2005. The survey areas covered 12 stations in the middle zone of the Bangpakong River, 12 stations at adjacent canal mouths that received pollution loads from a nearby community and 29 stations at pollution point sources. Results indicated that Bangpakong River was eutrophic all year round. High nutrient loads from Ban Pho community continuously flow into the aquatic environment.
The highest concentration of NH4⁺ nutrients came from crocodile farms (5,408 mg/m³), whereas maximum total loads (299×10⁹ mg) during the year were from domestic sources. Total nutrient loads varied temporally and were different among zones. Almost all nutrient levels were high during highloading periods while the remediation potential was generally low. Land remediation potential with respect to NH4⁺ and PO₄^3- was inexcess of 30 times more efficient in areas with comparatively high flow rates and more mangrove vegetation. In terms of river-water remediation potential, the efficiency of NH4⁺ elimination was less during the dry period. It was observed that the Na Lang, Nong Bua and Yai Loy canals were affected by some human and environmental impacts. These areas needed more attention with regard to monitoring and management. In addition, focus should also be given to the areas around the Pra Wet canal because of their low remediation potential during the dry period. Results of multivariate analysis on the ecosystem responses indicated that functions of NH4⁺ and total suspended solids in the aquatic system significantly influenced chlorophyll a changes. Based on the overall results, area zonation of the Ban Pho Town was being proposed and problems were being prioritized. Moreover, the application of integrated models suggested the need for better water quality control and/or management.