Shettapong Meksumpun

Influence of size and density on filtration rate modeling and nutrient uptake by green mussel (Perna viridis)

This study investigates green mussel filtration rates based on variation of the mussel size and density, and attempts to correlate these with the amount of Chaetoceros calcitrans consumed by kinetic modeling. The filtration rates were found to be more effective in small mussels and with greater volumes of seawater/mussel which represent low mussel densities in the mussel farms. Under field condition, the first order kinetic model is useful for evaluation of mussel filtration rate. However, the composite exponential kinetic model was determined to better describe filtration rates in a close system. Higher ratios of seawater volume L/g DW mussel tissue, resulted in an increasing filtration rate until a maximum plateau was reached at 10.37 L/h/g DW tissue as determined by first order kinetics. Based on the filtration rate, carbon, nitrogen, and phosphorus uptake by green mussels were found to be 2128.72, 265.41, and 66.67 mg/year/indv, respectively.

Province-based self-remediation efficiency of the Tha Chin river basin, Thailand.

The Tha Chin River Basin located in the great central basin of Thailand is used for water supply, aquaculture, transportation, and recreation as well as a sink for wastewater discharges. Because of gradual deterioration of water quality and fishery resources, this study aimed to explain recent status of the river self-remediation efficiency that was influenced by nutrient inputs and outputs from the river system. Field surveys were carried out during May 2007 (early rainy season) and October 2007 (late rainy season) within the Tha Chin River located in 4 provinces; Chainat, Suphan Buri, Nakhon Pathom, and Samut Sakhon. The nutrient budgets in each province section were analyzed. Results indicated that the river was in eutrophic condition all year round. High nitrogen and phosphorus loads from surrounding agricultural land use, agro-industry, and community continuously flew into the river system. Those nutrient concentrations were higher in the early rainy season than the late rainy season. The lowest river zone (in Samut Sakhon province) indicated highest dissolved inorganic nitrogen (DIN) and orthophosphate phosphorus (P) discharges of 145.54 and 36.14 tons/day, respectively. The highest remediation efficiency of the river (ca 60% of the total input) was found in the uppermost area of Suphan Buri province. The lowest remediation efficiency (ca 12%) was found in Samut Sakhon province. From the overall view, long term monitoring of river and estuarine DIN and P should be conducted. To make better condition of aquatic environment and fishery resource in each province-based section, the controls of DIN and P remediation efficiencies (e.g. by effective management of flow speed) at 20 and 50%, respectively, were recommended.

Integration of aquatic ecology and biological oceanographic knowledge for development of area-based eutrophication assessment criteria leading to water resource remediation and utilization management: a case study in Tha Chin, the most eutrophic river of Thailand.

This research was carried out in Tha Chin Watershed in the central part of Thailand with attempts to apply multidisciplinary knowledge for understanding ecosystem structure and response to anthropogenic pollution and natural impacts leading to a proposal for an appropriate zonation management approach for sustainable utilization of the area. Water quality status of the Tha Chin River and Estuary had been determined by analyzing ecological, hydrological, and coastal oceanographic information from recent field surveys (during March 2006 to November 2007) together with secondary data on irrigation, land utilization, and socio-economic status.Results indicated that the Tha Chin River and Estuary was eutrophic all year round. Almost 100% of the brackish to marine areas reflected strongly hypertrophic water condition during both dry and high-loading periods. High NH(4)(+) and PO(4)(3-) loads from surrounding agricultural land use, agro-industry, and community continuously flew into the aquatic environment. Deteriorated ecosystem was clearly observed by dramatically low DO levels (ca 1 mg/l) in riverine to coastal areas and Noctiluca and Ceratium red tide outbreaks occurred around tidal front closed to the estuary. Accordingly, fishery resources were significantly decreased. Some riverine benthic habitats became dominated by deposit-feeding worms e.g. Lumbriculus, Branchiura, and Tubifex, while estuarine benthic habitats reflected succession of polychaetes and small bivalves. Results on analysis on integrated ecosystem responses indicated that changing functions were significantly influenced by particulates and nutrients dynamics in the system.Based on the overall results, the Tha Chin River and Estuary should be divided into 4 zones (I: Upper freshwater zone; II: Middle freshwater zone; III Lower freshwater zone; and IV: Lowest brackish to marine zone) for further management schemes on water remediation. In this study, the importance of habitat morphology and water flow regimes was recognized. Moreover, nearshore extensive shrimp culture ponds, irrigation canals, and surrounding mangrove habitats belonging to local households seemed to act as effective natural water treatment system that can yet provide food resources in turns. These remediation-production integrated functions should be deserved depth considerations for water quality development of the Tha Chin areas.

Observations on Embryonic Development of Black-Spot Jorunna, Jorunna Funebris (Kelaart, 1859) (Gastropoda: Nudibranchia)

ABSTRACT Jorunna funebris is one of the nudibranch species with the largest distribution worldwide, but there is lack of information about its life history. To provide more information on embryonic development, 19 adult nudibranchs ranging in length from 1.3–6.5 cm were collected from the Gulf of Thailand for examination of embryonic development under laboratory conditions. The seawater conditions in the broodstock aquaria were as follows: temperature range, 22.3–26.3°C; salinity, 27.9–34.0 psu; dissolved oxygen, 7.0–8.3 mg/L; and pH, 7.2–8.9. Each nudibranch laid only 1 egg mass after culturing for 1–3 days. The egg masses of J. funebris ranged from 17.1–48.0 cm in length, and between 0.4 cm and 0.7 cm in width. The density of egg capsules varied from 27–64 egg capsules/mm2 of egg mass (n = 4), and each egg capsule had 1–4 larvae inside (n = 9). The embryonic period (expressed as the mean ± SD) was 7.3 ± 1.0 days (n = 7 egg masses). Based on the results of uncleaved embryonic diameter, embryonic period, and shell pattern, the development mode of J. funebris could be defined as “planktotrophic development.”

Impacts of nutrients and related environmental factors on distribution and size structure of Noctiluca scintillans populations of the Eutrophic Tha Chin Estuary, Thailand

This study aimed to analyze the impacts of nutrients and related aquatic factors on changes in the Noctiluca population of the Tha Chin estuary, a nutrient-rich estuary located in the inner Gulf of Thailand. Field surveys were carried out at 30 stations during November 2009 to August 2010. The results indicated high levels of dissolved inorganic nitrogen (DIN; 13.89-46.99 μmol/L) and PO(4)(3-)-P (0.20-3.05 μmol/L) where the Noctiluca red tide occurred, particularly during the high-loading period. Dense populations were usually found in the outer part of the estuary with comparatively high salinity (25-29 psu). The highest Noctiluca density was 72,333 cells L(-1) and the cell diameters ranged between 360 and 460 μm. Proportions of small-sized cells (P(s); less than 300 μm) varied over time. In this study, P(s) showed a positive correlation with levels of PO(4)(3-)-P, while the total population density was significantly affected by levels of NH(4)(+)-N and DIN (p < 0.05). Overall, PO(4)(3-)-P influenced the development of the Noctiluca red tide, with the limitation of PO(4)(3-)-P levels to below 1 μmol/L suggested for controlling Noctiluca red tide outbreaks at their origin. To support environmental conservation and maintain sustainable production in the estuary, the levels of PO(4)(3-)-P should be considered for the further effective development of water quality standards in estuarine zones.