The Influence of Water Temperature and Salinity on Filtration Rates of the Hard Clam, Meretrix petechialis

말백합의 연령별 여과율에 미치는 수온과 염분의 영향

This study was performed to describe the influence of water temperature and salinity on the filtration rate of the hard clam, Meretrix petechialis. The filtration rates of hard clams showed significant differences depending on both water temperature and age group (two-way ANOVA, p < 0.001). The filtration rate of all the hard clams, aged from 1 to 4 years, was generally reduced in low temperature range ( $5-15^{\circ}C$). As the water temperature increased, the filtration rate increased exponentially. The filtration rate was relatively high in $20-30^{\circ}C$ water temperature range, but rapidly decreased again at around $35^{\circ}C$. Variations in the data for filtration rates of hard clams, relative to age and changing water temperature, were used to determine the temperature coefficient $Q_{10}$ in each water temperature range. In $5-15^{\circ}C$ temperature range, every age group showed the highest $Q_{10}$ figure. It was found that on the whole, the higher the water temperature was, the lower the number of $Q_{10}$ was. Regardless of age, the number of $Q_{10}$ was higher in the lower water temperature range. In $25-35^{\circ}C$ temperature range, the number of $Q_{10}$ was less than 1.00 in all age groups, implying that this is the range in which the filtration rate decreased. Variations in the filtration rate also showed very clear differences (two-way ANOVA, p < 0.001) according to changing salinity and age. All the age groups, from 1 to 4 year olds, showed low filtration rates at both low salinity (10-15 psu) and high salinity (40 psu). The highest filtration rate was recorded at 30 psu, and relatively high filtration rates were found around 30 psu. However, the Student-Newman-Keuls post hoc multiple comparison test found that the hard clams in the 1-year group showed high filtration rates in a relatively narrower salinity range compared to those in the 2, 3, and 4 year groups. In other words, hard clams in the 2, 3, and 4 year groups showed high filtration rates at higher levels of salinity.

본 연구는 말백합, Meretrix petechialis의 기초 생리, 생태학적 정보를 파악하기 위한 일환으로 수온 및 염분의 변화가 이들의 여과율에 어떠한 영향을 미치는지 파악하고자 수행되었다. 말백합은 전라북도 김제시 거전리 갯벌에서 채집하였고, 먹이생물은 Phaeodactylum tricornutum(KMCC B-128)을 실내에서 단일종 배양하여 사용하였으며, 여과율 측정은 Coughlan(1969)의 간접측정법을 사용하였다. 먹이생물의 농도는 혈구계산판을 이용하여 광학현미경하에서 직접 계수하였다. 전체적인 실험과정은 Shin and Lim(2003)과 동일하였다. 수온별 말백합의 여과율 변동의 경우 연령에 관계없이 $25-30^{\circ}C$에서 대체적으로 높은 여과율을 나타내었고, 전반적으로 $5^{\circ}C$에서 최소 여과율을 나타내는 경향이었다. 염분별 말백합의 여과율 변동의 경우 전반적으로 20-35 psu의 염분구간에서 비교적 높은 여과율을 나타내는 경향이었다. 연령별 여과율 변동의 경우 대체적으로 연령이 낮을수록 건중량당 여과율은 상대적으로 높은 경향이었다. $Q_{10}$ 값의 경우 전반적으로 낮은 수온 구간($5-15^{\circ}C$)에서 높은 값을 나타내는 경향이었다.