Abstract:
The objectives of this research were to monitor water quality and study the phytoplankton biodiversity and periphyton in the vicinity of the Lotus Museum, Rajamangala University of Technology Thanyaburi. Water samples, phytoplankton and periphyton were collected monthly from May 2011 to May 2012 (during which flood disaster occurred in October 2011). Samples were collected from 3 sampling sites: Sampling site 1  the large-size lotus pond, Sampling site 2  the medium-size lotus pond, and Sampling site 3  the small-size lotus pond. The physico-chemical and biological parameters, biovolume of phytoplankton and periphyton were applied to monitor water quality in the Lotus Museum and improved the water quality to be suitable for the lotus growth.
Concerning the study of phytoplankton and periphyton biodiversity, 49 species in 7 divisions of phytoplankton, 39 species in 6 divisions of periphyton that attached to the lotus, and 44 species in 6 divisions of periphyton that attached to Hydrilla vercillata were found in Sampling site 1. 54 species in 6 divisions of phytoplankton, 47 species in 6 divisions of periphyton that attached to the lotus and 45 species in 6 divisions of periphyton that attached to Hydrilla vercillata were found in Sampling site 2, while fifty-eight species in 7 divisions of phytoplankton, 39 species in 6 divisions of periphyton that attached to the lotus and 44 species in 7 divisions of periphyton that attached to Hydrilla vercillata were found in Sampling site 3. The dominant species of phytoplankton were: Oscillatoria limosa C. Agardh ex Gomont, Cylindrospermopsis raciborskii (Wolosz) Seenayya & Subba Raju, Cyclotella meneghiniana Kützing, Lepocinclis acus (O.F. Müller) Marin & Melkonian, Gymnodinium sp., Peridinium sp., Closterium sp. and Botryococcus braunii Kützing. The dominant species of periphytic algae that attached to the Lotus were: Pseudanabaena limnetica (Lemmemann) Komárek, Cylindrospermopsis raciborskii (Wolosz) Seenayya & Subba Raju, Oscillatoria limosa C. Agardh ex Gomont, Nitzschia palea (Kützing) Smith, Cyclotella meneghiniana Kützing, Pseudanabaena galeata Böcher, Chlorella sp. and Gymnodinium sp. and periphyton that attached to Hydrilla vercillata the dominant species of periphyton that attached to the lotus were Pseudanabaena limnetica (Lemmemann) Komárek, Cylindrospermopsis raciborskii (Wolosz) Seenayya & Subba Raju, Oscillatoria limosa C. Agardh ex Gomont, Nitzschia palea (Kützing) Smith, Chlorella sp. And Pseudanabaena sp.1. It was also found that the differential habitat of aquatic plants did not affect the amount of algae cells at the statistically significant level of 0.05.
The comparison of water quality from the three Sampling sites of the lotus pond was investigated. It was found that the water quality of the three sites was Meso-Eutrophic Status from May to September 2011, and the nutrients were suitable for the growth of the lotus. However, after the flood disaster from November 2011 to March 2012, the water quality was Eutrophic Status and the amount of ammonia  nitrogen was higher than the standard amount determined by the Thai Government for Surface Water (classified as the fourth category), which was not suitable for the growth of various kinds of lotuses causing the stem, the root and the leaf of the lotus to be rotten and dead. Furthermore, this status resulted in the rapid growth of algae and eutrophication that hindered light penetration and photosynthesis affecting the lotus to be rotten. The lotuses were also wrapped around by the filaments of algae and could not grow to the water surface. After April 2012, nutrient levels decreased. The temperature of the water and pH were in the range appropriate for the growth of the lotus.