Daylight Period Research Articles

Interannual Ecosystem CO2 Dynamics in The Alpine Zone of The Eastern Alps, Austria

ABSTRACTInformation about the annual carbon fluxes of fen and meadow ecosystems in alpine environments is rare. We studied the influence of photosynthetic active radiation (PAR), plant green area index (GAI), soil temperature, and water-filled pore space (wfps) on the net CO2 emission at four alpine sites (one meadow and three fen sites) differing in water balance and plant community. Measurements over two years were made in the Eastern Alps, Austria, including two snow-free periods and two snow periods. During snow-free periods, net CO2 gain during daylight periods (NEElight , PAR > 0) depended on PAR and GAI. The net CO2 emission rate at night (Rtot , PAR = 0) was positively related to soil temperature, while low wfps reduced the carbon loss via Rtot of the meadow and driest fen study site but reinforced carbon loss of the wetter fen sites. Daily average ecosystem net CO2 gain (NEEday ) during snow-free periods (averaged over both years) at the meadow was 3.5 g CO2 m−2 d−1 and ranged from 1.5 to 3.4 g CO2 m−2 d−1 at the fen sites. Mean average daily wintertime CO2 emission was low, being only −0.9 g CO2 m−2 d−1 for meadow and between −0.2 and −0.7 g CO2 m−2 d−1 for all fen sites. All sites function as significant annual net carbon sinks, with a net carbon gain from 50 to 121 g C m−2 a−1 (averaged over both years) irrespective of water balance. Our results indicate that these alpine fen sites that have built up a large carbon stock in the past do not gain a further carbon surplus compared with the meadow under the current climate.

Plunging Behaviour in Chick-rearing Brown Boobies

ABSTRACT Brown Boobies (Sula leucogaster) obtain prey by plunge dives. In order to investigate the foraging behaviour of Brown Boobies underwater, we attached acceleration data loggers to chick-rearing Brown Boobies at Nakanokamishima Island in Japan. We documented, for the first time, Brown Boobies performing many rapid and shallow V-shaped dives and some W-shaped dives during the daylight period. The average and maximum dive depth and duration were 1.03 m and 3.81 m and 1.83 s and 21 s, respectively. Furthermore, Brown Boobies used buoyancy to ascend to the water surface. Our data suggest that Brown Boobies mainly depend on shallow-plunging, contrary to the pursuit divers such as gannets, due to their ecological and/or physiological constraints.

Above-ground thermal energy storage rates, trunk heat fluxes and surface energy balance in a central Amazonian rainforest

The thermal (physical) energy storage rates (ESR) of the above-ground components of a “terra firme” forest site in central Amazonia, Brazil, were determined for a set of typical days during the dry season of 2003 and the wet season of 2004, and their relevance to the surface energy balance was studied. To obtain the ESR for the above-ground part of the biomass (trunks, branches and litter), the temperatures of one trunk of a dominant tree species of the forest site were measured at three height levels and several radial depths. To compute the ESR in the other parts of the above-ground biomass (twigs, leaves and small size components such as palms and lianas) and the ESR atmospheric fraction, the temperature of the air was measured at four different heights inside and above the forest. The air, trunks and other biomass components contributed 35%, 40% and 25% to the total daily ESR of the forest respectively. For the hourly values during the morning, the total ESR was usually observed to be between 30 and 70 W m −2, but with maxima that can exceed 90 W m −2; during rain events minima as low as −200 W m −2 were observed. During the night and at dawn and dusk, the total ESR may constitute a sizable fraction of the net radiation, on some occasions equaling, or even exceeding it. On a daily basis, values of the total ESR were observed to be between −40% and 5% of the net radiation, depending on the weather conditions during the day. Further, the inclusion of the ESR to compute the surface energy balance improves its closure, mainly during the daylight period and, particularly, during the morning hours; but the best closure occurs for the days in which the daily balance of the total ESR is positive. Finally, simplified expressions are presented for those components of the ESR which do not depend on trunk temperature.

Spatial and temporal variations of Cocconeis placentula var. euglypta (Ehrenb.) 1854 Grunow, 1884 in drift and periphyton

Spatial and temporal variations of Cocconeis placentula var. euglypta in drift and periphyton were studied in mountain streams of the Córdoba Province (Argentina). The sampling program was conducted in study sites located on a confluence between different order streams during an annual cycle. Samples were also taken every two hours during the daylight period in high and low water conditions. The relationship between drift and cellular reproduction was evaluated by valve length biometrics analysis. C. placentula var. euglypta drift was continuous; its density was not always dependent on periphyton density in each locality. C. placentula var. euglypta drift could be related to abiotic factors such as temperature and flow during the annual cycle. There were significant differences between periphyton and drift valve lengths. Moreover, drift can be associated with cellular reproduction because density was higher when valve lengths were shorter at different hours of the day. C. placentula var. euglypta epiphytims on Cladophora glomerata also influenced drift density and size distribution, modifying the relationship between periphyton and drift during the late spring when C. placentula var. euglypta was detached from senescent mats.

INFLUENCE OF MINING ON BEHAVIOR OF BIGHORN SHEEP

Abstract Mining has been cited as detrimental to bighorn sheep (Ovis canadensis), but little research exists that has demonstrated those effects. We compared behavior of bighorn sheep while individuals were inside and outside of an active copper mine to determine if individual animals were altering their behavior relative to the active mine. We conducted this study in the Silver Bell Mountains, Arizona, from December 2003 to January 2005. We observed 3 radiocollared subadult males, 4 adult males, and 5 females, and recorded behavior throughout the daylight period. After accounting for differences by sex-age class (i.e., subadult male, adult male, female) and season (i.e., breeding, non-breeding), bighorn sheep fed less (6%) while inside the mine perimeter. Other behaviors (e.g., bedding, standing, alert, and interacting) were observed for similar amounts of time while within and outside the mine perimeter. Within sex-age classes, there were few differences in behavior. Subadult males fed less (mean differ...

Time budgets and habitat use of White-naped Cranes Grus vipio in the Ulz river valley, north-eastern Mongolia during the breeding season

AbstractHabitat loss and degradation are critical threats for the globally threatened White-naped Crane Grus vipio. We estimated the size of the area used per day and the time budgets of parental and non-parental White-naped Crane pairs in north-eastern Mongolia during 2000 and 2001. Six parental crane pairs used an area of 11–155 ha per day. The maximum distance of a focal parental crane from the roosting-site was 3,030 m. Habitat conservation measures for breeding White-naped Cranes need to be targeted to within at least 3 km of the roosting-site or nest-site. Parental cranes spent 79.6 ± 4.8% of the daylight period foraging and had reduced preening and resting behaviour to 4.4 ± 1.9%. Pairs without juveniles showed a pronounced period of resting and preening behaviour during midday, which was absent in parental cranes. This indicates that parental cranes may be time-stressed. We conclude that increases in feeding-related activities (e.g. caused by a decrease in food availability) are likely to be at the expense of parental vigilance. Conversely, increases in vigilance (due to e.g. increased disturbance) may have a negative impact on feeding-related activities. Both increases can potentially negatively affect reproductive success in this Vulnerable species.

The effects of latitude and day length on fattening strategies of wintering coal tits Periparus ater (L.): a field study and aviary experiment

1. Cyclic daily fattening routines are very common in wintering small wild birds, and are thought to be the consequence of a trade-off between different environmental and state-dependent factors. According to theory, these trajectories should range from accelerated (i.e. mass increases exponentially towards dusk) when mass-dependent predation costs are the most important cause of mortality risk, to decelerated (i.e. the rate of mass gain is highest at dawn and decreases afterward) when starvation is the greater risk. 2. We examine if geographically separate populations of coal tits, wintering in Scotland and central Spain under contrasting photoperiods, show differences in their strategies of daily mass regulation. We describe population differences in wild birds under natural conditions, and experimentally search for interpopulation variation in diurnal body mass increase under common, manipulated, photoperiod conditions (LD 9 : 15 h vs. 7 : 17 h), controlling for temperature, food availability, predator pressure and foraging arena. 3. Winter diurnal mass gain of wild coal tits was more delayed towards the latter part of the daylight period in central Spain (i.e. the locality with longer winter days) than in Scotland. In both localities, the pattern was linked to the average mass at dawn, with mass increasing more rapidly in lighter birds. However, under the controlled photoperiod situation the pattern of daily mass gain was similar in both populations. Diurnal body mass gain was more accelerated at the end of the day, and the increase in body mass in the first hour of the day was considerably lower under the long (9 h) than under the short (7 h) photoperiod in both populations. 4. Wintering coal tits show patterns of mass gain through the day that are compatible with current theories of the costs and benefits of fat storage, with birds at lower latitudes (with longer winter days) having a greater tendency to delay mass gain until late in the day. The experimental study revealed that these patterns are plastic, with birds responding directly to the photoperiod that they experience, suggesting that they are continually making fine-scale adjustments to energy reserves on the basis of both inherent (e.g. state-dependent) and extrinsic cues.

Somatic embryogenesis in strawberry (Fragaria sp.) through callus culture

Somatic embryogenesis was achieved from callus from leaf and nodal segments of strawberry clone pbgel-2000. The highest percent of cultures with somatic embryos was achieved on MS medium supplemented with 1.0 mg/l 2,4-D, 0.5 mg/l BAP and 50% proline. Darkness was the best condition for incubation with daily light periods over 6 h reducing the frequency of embryogenesis. Regenerated plants (90–95%) were successfully transferred to soil, showed normal morphology and produced fruit four months after planting.

Avian apolipoprotein A-V binds to LDL receptor gene family members

Apolipoprotein A-V (apoA-V) affects plasma triglyceride (TG) levels; however, the properties of apoA-V that mediate its action(s) are still incompletely understood. It is unclear how apoA-V, whose plasma concentration is extremely low, can affect the pronounced TG differences observed in individuals with various apoA-V dysfunctions. To gain novel insights into apoA-V biology, we expanded our previous studies in the chicken to this apolipoprotein. First, we characterized the first avian apoA-V, revealing its expression not only in liver and small intestine but also in brain, kidney, and ovarian follicles and showing its presence in the circulation. Second, we demonstrate directly that galline apoA-V binds to the major LDL receptor family member (LR) of the laying hen and that this interaction does not depend on the association of the apolipoprotein with lipid or lipoproteins. We propose that a direct interaction with LRs may represent a novel, additional mechanism for the modulation of TG levels by apoA-V.

Determination of lower limits for irrigation management using in situ assessments of apparent crop water uptake made with volumetric soil water content sensors

In situ approaches for determining lower limit (threshold, refill) values for irrigation management using continuously monitored data from volumetric soil water content (SWC) sensors were evaluated. Four indices were derived from SWC data: (i) apparent daily crop water uptake (ADCWU), the reduction in SWC during daylight periods; (ii) daily soil water loss (DSWL), the reduction in SWC during 24 h periods; (iii) previous overnight redistribution (POR), overnight drainage; and (iv) ADCWU normalised for reference evapotranspiration (ADCWU:ET o). Indices were calculated for 0–20 and 20–40 cm soil depths in four drying cycles applied to melon and to autumn and spring tomato crops. In each drying cycle, there were well-watered and un-watered irrigation treatments. In drying soil, values of ADCWU and DSWL followed a decay curve with three phases: (1) of rapid decline when drainage occurred; (2) of a much slower decline, after drainage ceased, with smaller values influenced by climatic factors; and (3) of constantly very low values not influenced by climate. The actual commencement of crop water stress was indicated by the first statistically significant difference in midday Ψ leaf between un-watered and well-watered plants. A protocol was developed to identify commencement of crop water stress using ADCWU or DSWL in un-watered plants. POR was used to identify cessation of internal drainage. Then, the first reduction in ADCWU or DSWL while climatic variables (solar radiation, VPD) indicated a constant or increasing atmospheric evaporative demand was considered an “indication” of crop water stress, the second such reduction as “confirmation”. In the four cycles studied, “indications” of crop water stress using both ADCWU and DSWL for 0–20 cm soil were 1 (twice), 2 and 6 d after commencement of water stress. When there was not appreciable climatic variation during phase 2, ADCWU and DSWL detected crop water stress within 1–2 d of Ψ leaf. Generally, climate-mediated fluctuations in ADCWU and DSWL during phase 2 delayed identification of the commencement of water stress. Normalising ADCWU for ET o reduced effects of climatic fluctuation. Using a 25% relative reduction in ADCWU:ET o as a threshold, this parameter was more sensitive than ADCWU or DSWL using the proposed protocols for detecting commencement of water stress. “Breaking points” in the rate of reduction of SWC, and variations in stem diameter were also compared for detecting commencement of crop water stress. This study suggested that reductions in SWC in drying soil can be used to identify lower limits for irrigation management using SWC sensors, and that stable climatic conditions are required to optimise these approaches.

WEDDELL SEAL UNDERWATER CALLING RATES DURING THE WINTER AND SPRING NEAR MAWSON STATION, ANTARCTICA

AbstractUnderwater vocalization monitoring and surveys, both on ice and underwater, were used to determine if Weddell seals (Leptonychotes weddellii) near Mawson Station, Antarctica, remain under the fast ice during winter within close range of breeding sites. Daytime and nighttime underwater calling rates were examined at seven breeding sites during austral winter and spring to identify seasonal and diel patterns. Seals rarely hauled out at any of the sites during winter, although all cohorts (adult males, females, and juveniles) were observed underwater and surfacing at breathing holes throughout winter (June–September) and spring (October–December). Seal vocalizations were recorded during each sampling session throughout the study (n= 102 daytime at seven sites collectively, and n= 5 24‐h samples at each of two sites). Mean daytime calling rate was low in mid‐winter (July) (mean = 18.9 ± 7.1 calls/min) but increased monthly, reaching a peak during the breeding season (November) (mean = 62.6 ± 15.7 calls/min). Mean nighttime calling rate was high throughout the winter and early spring (July–October) with mean nocturnal calling rate in July (mean = 61.8 ± 35.1 calls/min) nearly equal to mean daytime calling rate in November (during 24‐h daylight). Reduced vocal behavior during winter daylight periods may result from animals utilizing the limited daylight hours for nonvocal activities, possibly feeding.

Daily and seasonal variation of water relationship in sugar apple ( Annona squamosa L.) under different irrigation regimes at semi-arid Brazil

In the northeast of Brazil the drought period determines the yield period of the sugar apple ( Annona squamosa L.). As a result, the use of irrigation is essential to stagger production over the course of the year. The results shown here represent an analysis of water status levels in sugar apples in daylight and seasonal periods in semi-arid regions. Two plant groups were studied: one without irrigation and the other with irrigation during drought months. This study showed that younger leaves displayed greater stomatal conductance and transpiration. In drought months, even in irrigated plants, the high air moisture deficit had a strong influence on the stomatal closure, which did not translate into a reduction in transpiration. Over the same period, the leaf water potential was −1.8 and −2.9 MPa at mid-day in irrigated and non-irrigated plants, respectively, and only the irrigated plants could recover their leaf hydration level at night. With a water deficit, plants showed greater control of transpiration through stomatal closure, with a linear relationship between stomatal conductance and transpiration.

Primary Infection, Lesion Productivity, and Survival of Sporangia in the Grapevine Downy Mildew Pathogen Plasmopara viticola

ABSTRACT Several aspects of grapevine downy mildew epidemiology that are fundamental to model predictions were investigated. Simple rainfall-, temperature-, and phenology-based thresholds (rain > 2.5 mm; temperature > 11 degrees C; and phenology > Eichorn and Lorenz [E&L] growth stage 12) were evaluated to forecast primary (oosporic) infection by Plasmopara viticola. The threshold was consistent across 15 years of historical data on the highly susceptible cv. Chancellor at one site, and successfully predicted the initial outbreak of downy mildew for 2 of 3 years at three additional sites. Field inoculations demonstrated that shoot tissue was susceptible to infection as early as E&L stage 5, suggesting that initial germination of oospores, rather than acquisition of host susceptibility, was probably the limiting factor in the initiation of disease outbreaks. We also found that oospores may continue to germinate and cause infections throughout the growing season, in contrast to the widely-held assumption that the supply of oospores is depleted shortly after bloom. Lesion productivity (sporangia/lesion) did not decline with age of a lesion in the absence of suitable weather to induce sporulation. However, the productivity of all lesions declined rapidly through repeated cycles of sporulation. Extremely high temperatures (i.e., one day reaching 42.8 degrees C) had an eradicative effect under vineyard conditions, and permanently reduced sporulation from existing (but not incubating) lesions to trace levels, despite a later return to weather conducive to sporulation. In fair weather, most sporangia died sometime during the daylight period immediately following their production. However, over 50% of sporangia still released zoospores after 12 to 24 h of exposure to overcast conditions.

Synchronization and leadership in switches between resting and activity in a beef cattle herd—A case study

The mechanisms of activity synchronization in group living ungulates are not well understood. In a case study on herd of 15 Gasconne beef cows with calves observed during a total of 25 summer daylight periods in 2004 and 2005, we examined whether cows similar to each other in body weight or in reproductive status were more synchronized and whether the timing of activity switches were determined by specific leading animals. We calculated the synchronization of all possible pairs of cows in the herd and tested the effects of similarity in body weight and in reproductive status (lactating versus non-lactating) on synchronization in the pair. Further, we assessed whether any specific individuals, and especially the dominant cows, were more able, through their own activity switch, to incite another cow to follow shortly with her switch in activity. We found that body weight differences had a negative influence on pair synchronization (GLMM, F 1,65 = 6.79; p < 0.05), but reproductive status did not affect the synchronization. Cows’ individual identity explained only a small proportion (<2%) of variability in intervals between switches of subsequent cows. Furthermore, dominance status of an individual cow did not correlate with mean interval between her activity switches and activity switches of the next cow (lying down: Spearman correlation, r s = −0.16, n = 14, p > 0.10; standing up: Spearman correlation, r s = −0.38, n = 14, p > 0.10), indicating that there were no leading animals initiating switches in activity in our herd.

Diurnal exchanges of CO 2 and CH 4 across the water–atmosphere interface in a water chestnut meadow ( Trapa natans L.)

CH 4 and CO 2 fluxes across the water–atmosphere interface were measured over a 24 h day–night cycle in a shallow oxbow lake colonized by the water chestnut ( Trapa natans L.) (Lanca di Po, Northern Italy). Only exchanges mediated by macrophytes were measured, whilst gas ebullition was not considered in this study. Measurements were performed from 29 to 30 July 2005 with short incubations, when T. natans stands covered the whole basin surface with a mean dry biomass of 504 ± 91 g m −2. Overall, the oxbow lake resulted net heterotrophic with plant and microbial respiration largely exceeding carbon fixation by photosynthesis. The water chestnut stand was a net sink of CO 2 during the day-light period (−60.5 ± 8.5 mmol m −2 d −1) but it was a net source at night (207.6 ± 6.1 mmol m −2 d −1), when the greatest CO 2 efflux rate was measured across the water surface (28.2 ± 2.4 mmol m −2 h −1). The highest CH 4 effluxes (6.6 ± 1.8 mmol m −2 h −1) were determined in the T. natans stand during day-time, whilst CH 4 emissions across the plant-free water surface were greatest at night (6.8 ± 2.1 mmol m −2 h −1). Therefore, we assumed that the water chestnut enhanced methane delivery to the atmosphere. On a daily basis, the oxbow lake was a net source to the atmosphere of both CO 2 (147.1 ± 10.8 mmol m −2 d −1) and CH 4 (116.3 ± 8.0 mmol m −2 d −1).

Estimation of Reference Evapotranspiration by an Energy Balance Approach

The sustainability of irrigated agriculture depends primarily on efficient water use. Efficient irrigation decisions can be expressed as a function of potential atmospheric demand, which is expressed by reference evapotranspiration (ETo) governing either the ideal amount of water taken up by the plants or irrigation frequency of agronomic crops at a given site. All ETo estimation methods refer to daily values including night evaporation losses. Night time losses are only substantial for a few days after rain or irrigation. A method is proposed for estimating ETo based on the local energy balance from limited meteorological data monitored in an automated weather station throughout daylight periods. To validate the current method, climatic data and lysimetric measurements from Piracicaba, Sao Paulo, Brazil were used. Regression analyses revealed that a modified Bowen method provided results similar to the Penman–Monteith method and similar to measurements made by weighing lysimeters with load cells. The modified balance energy approach tended slightly to overestimate evapotranspiration by about 5%, whereas the Penman–Monteith method tended to underestimate atmospheric demand at a rate close to 7%. Given the high coefficients of determination and ease of estimation, the method based on daily net radiation, mean air temperature and relative humidity is recommended for assessment of crop water use for the region studied. Further investigations are required to examine the performance of the modified Bowen approach at other specific sites under different climatic conditions.

Mobile mRNA Makes Potatoes

Tuber formation in potato plants is promoted when plants are exposed to short-day photoperiods and inhibited in plants that experience summerlike long periods of daylight. This process requires that a signal be passed from the leaves to the growing tuber underground. Banerjee et al . report a series of experiments that implicate specific mRNAs as the molecules that carry the signal. The mRNA encodes a transcription factor called St BEL5 that acts with another transcription factor, POTH1, to control hormone concentrations in the tuber that regulate growth. The authors used laser microdissection of specific cell types and reverse transcription polymerase chain reaction amplification to pinpoint specific mRNAs in phloem and other cell types. When a leaf-specific promoter was used to drive expression of St BEL5 RNA, exposure to short days enhanced mobility of the RNA to the root region. Overexpression of the St BEL5 transcript enabled transgenic plants to undertake tuber formation even when exposed to long photoperiods. The authors propose that the mRNA transport reflects light-dependent changes in the abundance of RNA-binding proteins that facilitate transport and targeting of mRNA to specific cells. A. K. Banerjee, M. Chatterjee, Y. Yu, S.-G. Suh, W. A. Miller, D. J. Hannapel, Dynamics of a mobile RNA of potato involved in a long-distance signaling pathway. Plant Cell 18 , 3443-3457 (2006). [Abstract] [Full Text]

Environmental controls on the CO2 exchange in north European mires

Net CO2 exchange measured under well-mixed atmospheric conditions in four different mires in Sweden and Finland were used to analyse which factors were controlling photosynthesis and respiration. The parameters of a light response function showed strong seasonal variations with similar behaviour for all mires. The half-monthly nighttime respiration rates in the central part of the growing season were about two times higher in the southernmost, warmest site, Fåje, as compared to the northernmost, coldest site, Kaamanen. However, Kaamanen had high photosynthesis rates, and this in combination with the long daylight periods in the middle of the summer caused Kaamanen to have the largest net ecosystem exchange (NEE) during the summer period. Fåje that showed the highest productivity had also the highest respiration and therefore, the lowest NEE during summer. Correlation between half-monthly components and different environmental variables showed the highest correlation between the components themselves. Thereafter came temperature except for Fåje where water table depth (WTD) explained most of the variance both for detrended and temperature-normalized components. All sites showed dependencies between WTD and the respective components during drying up periods. Temperature sensitivity was higher for productivity than for respiration indicating that CO2 uptake would increase during global warming.

Comparison of Heat Pumps for Permanent Lunar Base

A permanent lunar habitat will require a heat pump to elevate waste heat from ∼298 K to ∼340-360 K to reject it from a reasonably sized radiator array because the effective sink temperature is 265 K for horizontal radiators at noon of the 336 h lunar daylight period. Because launch cost is proportional to mass, the figure of merit is overall mass of the external thermal control system: compressor, power source, radiators, heat exchangers, pumps, and piping. Previous investigations involved very detailed optimizations for electromechanical compressors. This investigation expands upon those by conducting a comprehensive assessment of thermally driven sorption heat pumps: absorption (liquid-vapor), adsorption (solid-vapor), and chemisorption (thermally reversible reaction between binder and refrigerant). The lowest mass alternative is a new design for an adsorption (carbon-methanol) heat pump with an overall system mass of 652 kg, as compared with 726 kg for an electromechanical compressor.

돌돔, Oplegnathus fasciatus 치어의 절식시 산소 소비율에 미치는 수온과 광주기의 영향

돌돔 치어의 사육 관리 및 생체역학 모델 결정을 위한 기초자료를 수집하기 위해 수온과 광주기에 따른 산소 소 비율을 조사하였다. 절식한 돌돔(평균 무게 <TEX>$21.5{\pm}1.9g$</TEX> 총 180마리) 치어를 대상으로 네 가지 수온(10, 15, 20, <TEX>$25^{\circ}C$</TEX> 세 가지 광주기(24L:0D, 12L:12D, 0L:24D)에 따라 유수식 형태의 호흡실을 이용하여 24시간 동안 5분 간격으로(3반복) 산소 소비율을 측정하였다. 수온과 광주기 그리고 두 인자의 상호작용 모두가 돌돔 치어의 산소 소비율에 유의한 영향을 미쳤다.(P<0.001). 각 광주기 조건에서 수온 상승에 따라 산소 소비율은 유의적으로 증가하였다(P<0.001). 10, 15, 20그리고 <TEX>$25^{\circ}C$</TEX>에서의 시간당 평균 산소 소비율은 각각 <TEX>$202.1{\sim}403.4,\;306.7{\sim}502.2,\;536.7{\sim}791.0$</TEX> 그리고 <TEX>$879.9{\sim}1,077.4mg\;O_2\;kg^{-1}h^{-1}$</TEX>였으며, <TEX>$Q_{10}$</TEX> 값은 <TEX>$10{\sim}15,\;15{\sim}20,\;20{\sim}25^{\circ}C$</TEX>에서 각각 <TEX>$1.58{\sim}2.30,\;2.44{\sim}3.06,\;1.86{\sim}2.69$</TEX>이었다. 모든 수온 조건에서 연속 명기(24L:0D)일 때 산소 소비율은 연속 암기(0L:24D)일 때보다 유의하게 높았다(P<0.001). l2L:12D의 명기에서의 산소 소비율은 같은 조건의 암기 때보다 유의하게 높은 산소 소비율을 보였다(P<0.001). 결론적으로, 돌돔 치어 사 육시 고수온 및 긴 낮 시간이 유지될 때 사육수의 산소 결핍 현상에 주의를 기울여야 한다. The effect of water temperature and photoperiod on the oxygen consumption of the fasted juvenile parrot fish, Oplegnathus fasciatus was investigated to provide empirical data for the early-stage culture management and bioenergetic growth model of the species. The mean body weight of the juvenile used for the experiment was <TEX>$21.5{\pm}1.9g$</TEX>, and the oxygen consumption rate was measured under four water temperatures (10, 15, 20 and <TEX>$25^{\circ}C$</TEX>) and three photoperiods (24L:0D, 12L:12D and OL:24D) with an interval of 5 minutes for 24 hours using a continuous flow-through respirometer. In each treatment three replicates were set up and 15 juveniles were totally involved. The oxygen consumption rates increased with increasing water temperature under all photoperiod treatments (P<0.001). Mean oxygen consumption rates at 10, 15, 20 and <TEX>$25^{\circ}C$</TEX> ranged <TEX>$202.1{\sim}403.4,\;306.7{\sim}502.2,\;536.7{\sim}791.0\;and\;879.9{\sim}1,077.4mg\;O_2\;kg^{-1}h^{-1}$</TEX>, respectively. <TEX>$Q_{10}$</TEX> values ranged <TEX>$1.58{\sim}2.30$</TEX> between 10 and <TEX>$15^{\circ}C,\;2.44{\sim}3.06$</TEX> between 15 and <TEX>$20^{\circ}C\;and\;1.86{\sim}2.6y9$</TEX> between 20 and <TEX>$25^{\circ}C$</TEX>, respectively. Mean oxygen consumption rates of O. fasciatus were the highest in continuous light (24L:0D) followed by 12L:12D and 0L:24D (P<0.001). The oxygen consumption of fish exposed to the 12L:12D photoperiod was significantly higher during the light phase than during the dark phase under all temperature treatments (P<0.001). In summary, oxygen consumption rates of the juvenile parrot fish increase with increasing water temperature and lengthening daylight period; and, thereby, changes in water quality resulted from the depletion of oxygen under high temperature and long daylight photoperiod conditions should be monitored.