• 한국해양학회지:바다
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• 제12권4호
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• pp.262-272
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• 2007

갯벌을 이용하는 대형 및 초대형저서동물의 단기 변화양상(조석 및 주야변화)을 파악하기 위하여 2000년 6월 8일과 9일 양일 간에 걸쳐 변형된 오터트롤을 이용하여 현장조사를 실시하였다. 대형 및 초대형저서동물은 총 60종, 6,309개체, 67,835.46 gWWt이 채집되었다. 조사 결과, 대형 및 초대형저서동물의 분포 패턴은 주야와 조석 주기에 따라 변화하였다. 조석에 따라서는 크게 2개로 양분되어 간조 시기와 만조 시기로 구분되었다. 2개의 조석형태에 따른 생물량의 차이를 보면, 간조 시기$(13^h30',\;16^h30',\;01^h30',\;04^h30')$의 생물량은 만조 시기$(19^h30',\;21^h30',\;10^h30',\;13^h00')$의 그것과 비교하여 상대적으로 높았다. 한편, 주야에 따라서는 크게 3개의 범주로 구분할 수 있었다. 즉, 1)야간에 주로 출현하는 종군(자주새우와 보리새우과의 새우류, 꽃게과의 게류, 볼락과의 어류), 2)주간에 주로 출현하는 종군(참꼴뚜기과의 두족류와 멸치과의 어류), 마지막으로 3)주야에 따른 일정한 분포패턴을 보이지 않는 종군(민태과, 쥐노래미과, 참서대과의 어류, 분지성게과의 성게류) 등이었다. 장봉도 갯벌을 이용하는 대형 및 초대형저서동물의 주야 및 조석 주기에 따른 변화를 조사한 결과, 갯벌을 이용하는 대형 및 초대형저서동물은 주야보다는 조석 주기에 밀접한 연관성을 가지는 것으로 나타났다.

• Ocean Science Journal
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• 제42권1호
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• pp.1-8
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• 2007

Acoustic volume backscattering strength data were collected and Conductivity Temperature Depth (CTD) measurements were conducted in the southern Yellow Sea in summer 2005 and 2006. The high temporal and vertical resolution acoustic data measured with a 307 kHz Acoustic Doppler Current Profiler (ADCP) and a 250 kHz acoustic Doppler profile (ADP) had dominant diel variation, which resulted from vertical migration of sound scatterers. Some scatterers congregating in the bottom layer in the daytime migrated upward at dusk, and migrated downward into the bottom layer at dawn. The migration speeds were estimated. More than 33 days data show that the diel migration varies with time. The feature of migration measured with ADCP and ADP is consistent to some extent with what is described in the study on vertical migration of zooplankton in the southern Yellow Sea with conventional net samples.

• Ocean and Polar Research
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• 제39권4호
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• pp.257-267
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• 2017

Although Pacific mackerel (Scomber japonicus) is an important commercial species in Korea, its recruitment mechanism remains largely unknown. Diel vertical positioning of larvae in the water column, which is affected by their specific gravity and the surrounding water density, may help to provide an understanding on recruitment success through predator avoidance and prey availability. The specific gravity measurement on Pacific mackerel eggs and larvae would seem to be essential information necessary to learn about the transport process from spawning to nursery grounds, and consequently the recruitment success. Eggs were artificially fertilized, and larvae were fed with rotifer when their mouths opened 3-4 days after hatching. We conducted the experiment using a density gradient water column to measure the ontogenetic changes in specific gravity from fertilization to 10 days after hatching. Egg specific gravity was stable during most of the embryonic period, but a sudden increase to $1.0249g\;cm^{-3}$ happened just before hatching. However, the specific gravity of newly hatched larvae was much lighter ($1.0195g\;cm^{-3}$), and specific gravity tended to increase continuously after hatching. Comparison of specific gravity with seawater density reveals that eggs and newly hatched larvae can float in the surface layer of the ocean. For the later period of the experiment, the specific gravity showed a cyclic diel pattern: the highest in the evening while the lowest at dawn. The fullness of larval stomach may be responsible for the observed differences in specific gravity, because stomach fullness was lower (40-60%) at midnight, and higher (80-85%) in evening. The diel pattern of specific gravity might provide clues regarding how larvae match the diel vertical migration of prey organisms.

• 생태와환경
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• 제34권3호통권95호
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• pp.175-184
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• 2001

방류수내 남조류 세포의 밀포와 종조성 및 독소의 계절별, 일일 변화를 일본 중심에 위치하고 있는 Suwa호의 수문에서 1998년 5월부터 10월까지 조사하였다. Microcystis의 높은 세포밀도가 M. ichthyoblabe가 우점했던 7월과 M. viridis가 우점종으로 나타난 9월에 관찰되었다. Microcystis의 종조성과 총 세포밀도는 3종류의 microcystin의 정성${\cdot}$정량적인 변화와 관련이 있었다. M. ichthyoblabe가 우점했던 7월 동안에는 MC-RR과MC-LR만이 검출되었으나 M. aeruginosa의 개체수 증가와 함께 M. viridis가 우점종으로 나타난 8월부터 10월까지는 MC-YR을 포함한 3종류의 microcystin 모두 검출되었다. 방류수내 Microcystis의 세포밀포와 microcystin의 함량의 일 변화는 바람의 일 변화에 큰 영향을 받았다. 아침에 비해 오후에 바람이 강하게 부는 풍속주기의 조건에서 Microcystis의 세포밀도와 독소의 함량은 아침에 증가하고 오후에 감소하는 경향을 나타냈다. 본 연구의 결과들은 수문이나 취수탑에서 방류시기의 조절은 부영양 호수에서 물을 취수하여 이용함에 있어 원수내 조류의 생물량을 저감할 수 있는 유효한 방법임을 제시한다.

• 생태와환경
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• 제38권spc호
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• pp.31-38
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• 2005

Diel change in urea decomposition activity of epiphytic algae on Phragmites stems and phytoplankton in a shallow littoral reed zone in the south basin of Lake Biwa was investigated with an in situ technique using $^{14}C$-labelled urea. The daily rates of urea decomposition (sum of urea carbon incorporation rate and $CO_2$ liberation rate) by epiphytic and planktonic algae were calculated as 180 ${\mu}$ mole urea surface shoot area $m^{-2}\;day^{-1}$ and 210 ${\mu}$ mole urea $m^{-3}\;day^{-1}$. The chlorophyll a specific urea decomposition rates of epiphytic and planktonic algae were 4.7 to 6.4 and 4.4 to 6.2 ${\mu}$ mole urea mg chl. $a^{-1}$ incubation $time^{-1}$ in daytime and 4.2 to 5.7 and 2.4 to 3.5 ${\mu}$ mole urea mg chl. $a^{-1}\;time^{-1}$ in nighttime, respectively. High values were obtained during 12:00 ${\sim}$ 18:00 and low values during 00:00 ${\sim}$ 06:00 for both epiphytic and planktonic algal communities. A clear diel periodicity in the urea decomposing activity of the planktonic algae was observed. The activity of the epiphytic algae, on the other hand, showed no destinctive variation during a day. The present results indicate that epiphytic algae are one of the significant urea decomposers in a reed zone, and that the diel patterns are quite difference between both algal communities.

• 한국어류학회지
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• 제22권4호
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• pp.267-272
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• 2010

문치가자미 Pleuronectes yokohamae의 RNA/DNA비 일주기 변화를 조사하기 위하여 부화후 89일, 전장 $23.2{\pm}0.2mm$의 치어를 48시간 동안 일정한 시간 간격으로 채집하였다. RNA/DNA비는 주간(0800, 1100, 1400, 1700)에 높았고 야간(2000, 2300, 0200, 0500 hours)에는 낮게 나타났다. 이번 연구결과에서 문치가자미의 생화학적 일주기 변화를 확인하였고, 이와 같은 RNA/DNA비의 일주기적 변화를 고려하여 시료 채집시간 결정을 포함한 시료채집 계획작성과 data분석이 필요할 것으로 생각된다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권5호
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• pp.82-89
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• 2011

Understanding snowmelt movement to the watershed is crucial for both climate change and hydrological studies because the snowmelt is a significant component of groundwater and surface runoff in temperature area. In this work, a new energy balance budget algorithm has been developed for melting snow from a snowpack at the Central Sierra Snow Laboratory (CSSL) in California, US. Using two sets of experiments, artificial rain-on-snow experiments and observations of diel variations, carried out in the winter of 2002 and 2003, we investigate how to calculate the amount of snowmelt from the snowpack using radiation energy and air temperature. To address the effect of air temperature, we calculate the integrated daily solar radiation energy input, and the integrated discharge of snowmelt under the snowpack and the energy required to generate such an amount of meltwater. The difference between the two is the excess (or deficit) energy input and we compare this energy to the average daily temperature. The resulting empirical relationship is used to calculate the instantaneous snowmelt rate in the model used by Lee et al. (2008a; 2010), in addition to the net-short radiation. If for a given 10 minute interval, the energy obtained by the melt calculation is negative, then no melt is generated. The input energy from the sun is considered to be used to increase the temperature of the snowpack. Positive energy is used for melting snow for the 10-minute interval. Using this energy budget algorithm, we optimize the intrinsic permeability of the snowpack for the two sets of experiments using one-dimensional water percolation model, which are $52.5{\times}10^{-10}m^2$ and $75{\times}10^{-10}m^2$ for the artificial rain-on-snow experiments and observations of diel variation, respectively.

• 한국환경과학회지
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• 제22권2호
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• pp.215-223
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• 2013

The objective of this study was to evaluate fish passage efficiency, based on fish-trap monitoring methodology, in the fishway of Seungchon Weir, which was constructed on the lower region of Yeongsan River in 2011. Seasonal patterns and diel variations of fish movements, fish fauna, and compositions in the fishway were analyzed in relation to the current velocity and location of the trap-setting in the fishway. For the analysis, we conducted seven times surveys in 2012 on the fishway and also conducted intensive monitoring of the fishway as 3 hrs interval for the diel variations of fish fauna and compositions in the fishway. According to the fish-trap monitoring methodology, the total number of fish species was 13 species, which was a 43.3% of the total. Most dominant fish used the fishway was Squalidus chankaensis tsuchigae and the relative abundance of the species used the fishway was 33.5% of the total. The season and time zone (in diel variation) observed most frequently in the fishway were July and 18:00-21:00 PM, respectively. The fish movements and use-rates of fishway varied depending on the locations of trap-setting; Fish biomass and the number of species were statistically (p < 0.05) greater in the most right or left-sided traps than in the mid-traps. Also, fish movements and use-rates of fishway were influenced by current velocity on the fishway; fish in the fishway preferred the low current velocity (mean 0.71 m/sec) than the high current velocity (mean 1.13 m/sec). Further long-term studies should be monitored for the efficiency evaluations of the fishway.

• 생태와환경
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• 제45권1호
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• pp.34-41
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• 2012

The variation of dissolved oxygen (DO) was monitored with high frequency by an automatic data-logging sensor in a eutrophic urban stream (the Anyang Stream) located in a metropolitan area of Seoul, South Korea. In general, DO showed the diel variation of increase in daytime and decrease at night, implying that primary production is a major mechanism of oxygen supply in this ecosystem. The fluctuation of oxygen was determined by rainfall. DO depletion was most obvious after a rainfall resulting in an anoxic condition for a day, which is thought to be caused by scouring of periphyton and organic ooze at the stream bottom. Seasonally DO was higher in winter and frequently depleted in warm seasons. DO depletion was often at a dangerous level for fish survival. Fish survey showed that little fish was living at the study site and oxygen depletion may be the major stress factor for aquatic animals. From the results it can be suggested that a high frequency monitoring of oxygen should be established for the proper assessment of aquatic habitats and better management strategy.

• 한국해양학회지
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• 제21권3호
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• pp.146-155
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• 1986

1984년 5월 50m수층과 1985년 10월 수온구조에 따른 여러 층에서 채집한 동 물플랑크톤 시료를 분석한 결과, 현존량은 춘계에 평균 538 inds/㎥, 추계에는 전 수층 평균과 표층이 각기 267inds/㎥와 508inds/㎥ 를 나타낸다. 양 계절에 동정된 분류군은 각기 55종류, 104종류였으며 연구해역의 서식 분류군은 123종류에 이른다. 동물플랑크톤 군집에서의 우점종의 순위는 양 계절 공히 copepods를 필두로 protozoans, appendicularians 이다. 표층에서의 아열대성 종과 현존량의 분포는 동 계에 있어 대마해류 및 북한한류수의 영향을 반영하는 것으로 사료되는 반면, 춘계 에는 현존량만이 식별할 수 있는 변화를 보인다. 1985년 추계에는 전 수층에 걸쳐 영구 수온약층의 저부인 120m 수심이 중층 냉수종의 분포에 대한 장벽으로서 중요 한 역할을 한다. 1985년 10월에 연속 채집한 시료의 분석결과, 식별할 수 있는 주야 수직이동은 나타나지 않는데, 이는 동물플랑크톤 가운데 진정한 심해종의 결핍으로 심층에서의 생체량이 아주 빈곤하고 따라서 동해에서의 수직이동이 미약하다는 이 론을 입증하는 것으로 사료된다.