Abstract â We examined the respiration rate of Aurelia aurita medusae at 20°C and 28°C to evaluate minimum metabolic demands of medusae population in ...
Ocean Sci. J. (2012) 47(2):155-160 http://dx.doi.org/10.1007-012-0015-5
Available online at www.springerlink.com
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Estimation of the Minimum Food Requirement using the Respiration Rate of Medusa of Aurelia aurita in Sihwa Lake Chang-hoon Han1, Jinho Chae2*, Jonghyeok Jin1, and Wonduk Yoon1 1
Fishery and Ocean Information Division, NFRDI, Busan 619-705, Korea Korea Environmental Research Center for Hydrosphere, Ansan 426-862, Korea
2
Received 21 May 2012; Revised 31 May 2012; Accepted 12 June 2012 © KSO, KIOST and Springer 2012
Abstract − We examined the respiration rate of Aurelia aurita medusae at 20 °C and 28 °C to evaluate minimum metabolic demands of medusae population in Sihwa Lake, Korea during summer. While weight specific respiration rates of medusae were constant and irrespective to the wet weight (8-220 g), they significantly varied in respect to temperatures (p90%). The DO concentration of the seawater in the chamber was measured using a Clark-type electrode (OX-MR, Unisence) connected to a picoammeter over 1 h. The electrode used in the measurement was calibrated by air bubbling (100%) and 0.1 M NaOH/ ascorbate solution (0%) prior to the experiment. The respiration chamber rested in a water bath connected to a water temperature controller (EYELA, NCB 2000). During measurement, the chamber was equipped with a magnetic stirrer rotating at 150 rpm to prevent oxygen gradient development. Each medusa was protected from the stirrer’s interference by a polystyrene mesh divider (mesh size: 5 mm). After the DO measurement, the wet weight and bell diameter of the medusa were measured. DO concentrations (ml O2 L-1) in the chamber were gained at 2 sec intervals and expressed by a linear regression line. Then, oxygen consumption rates of medusae were determined by the slope of decrease in DO concentration. Respiration rate of medusae (R, ml O2 medusa-1 d-1) at two different temperatures (i.e. 20 °C and 28 °C) was expressed by an allometric function of the wet weight of medusae as: R=aWb where W is the wet weight of medusa (g), a is a constant specific to the species and temperature, and b is the exponent coefficient. For control experiment, the DO concentrations of the chamber without medusa were measured in the same condition for 2 h. Differentiation between the weight specific respiration rates of medusae at two different temperatures was tested using t-test (SPSS 12.0). Q10 values were determined according to the van’t Hoff equation:
R Q10 = ⎛ -----2⎞ ⎝ R1⎠
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10 ⎞ ⎛ ---------------⎝T – T ⎠ 2
1
, where R2 and R1 are wet weight normalized respiration rates and T2 and T1 are the different temperatures for the experiments. Population minimum food requirement (PMFR, mg C m-3d-1) can be estimated as: k × R × RQ × B PMFR = ---------------------------------A×W , where k is carbon conversion coefficient (0.536 mg C ml-1 O2), R is respiration rate of medusae at a specific temperature, RQ is respiratory quotient [assuming 0.85, (Schneider 1989a, b)], A is assimilation efficiency [assuming 0.8, (Schneider 1989a)], W is average wet weight of medusae (g), and B is biomass of medusae (g m-3).
3. Results Abundance and growth Aurelia aurita medusae proliferated rapidly in June to a maximum abundance (3.22±0.8 medusae m-3) and biomass (246.1±59.9 g m-3, Fig. 2a). After the peak, they gradually decreased in abundance and biomass from July (abundance: 0.94±1.08 medusae m-3, biomass: 62.16±71.35 g m-3), and then were not observed in September. Increase of bell diameter and wet weight of the medusae stagnated during June and July (both p=1, specific growth rate: -0.056 d-1) when they appeared abundantly (abundance >0.9 medusae m-3, Fig. 2b). Significant increase of bell diameter and wet weight of the medusae was observed during July and August (both p0.96, p
