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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Insight from the Depths of the Straits of Florida: Assessing the Utility of Atlantic Deep-water Coral Geochemical Proxy Techniques

Rosenberg, Angela D 04 May 2011 (has links)
This thesis addresses the utility of deep-water coral geochemistry and its potential to reconstruct oceanographic conditions in the Straits of Florida. Through stable isotope and elemental analyses of the carbonate skeletons and use of available geochemical proxy calibration equations, present and past environmental parameters were determined. Over the last several years, scientific expeditions to the bottom of the Straits of Florida have revealed hundreds of deep-water coral mounds and led to the collection of extensive oceanographic data, sediment samples, and deep-water coral specimens. In 2005-2006, an Autonomous Underwater Vehicle (AUV) was used to map the coral mound fields at five sites with the use of geophysical imaging technology, and the manned Johnson-Sea-Link II submersible was deployed for further exploration and sample collection. The AUV and the submersible CTD also measured numerous environmental parameters, including temperature and salinity. With the goal of reconstructing environmental parameters across the Straits of Florida, Scleractinian and gorgonian deep-water coral specimens were selected from three sites spanning the Straits. Each coral was sampled at the highest resolution possible and analyzed for stable isotopes and elemental concentrations. Resulting geochemical data, specifically d18O, d13C, Sr/Ca, and Mg/Ca, was then used with previously published and newly developed calibration equations to calculate temperature, salinity, and seawater density. Kinetic and vital effects were also examined and taken into account while reconstructing environmental parameters using the coral geochemistry. Additional reconstructions using stable isotopic values from benthic foraminifera corroborated the geochemical reconstructions, and analyses of pteropods and surface sediment samples provided further insight into the oceanographic conditions at the bottom of the Straits of Florida. Results from geochemical reconstructions agreed with in situ data, indicating that slightly warmer bottom temperatures exist on the eastern side of the Straits and salinity variability among the three sites is minimal. This suggests that the deep-water coral skeletons are sensitive recorders of the environmental conditions in which they lived. Ultimately, in situ measurements and reconstructed parameters showed that there is little variability across the bottom of the Straits and that Antarctic Intermediate Water (AAIW) is the only apparent water mass in the area at that depth. Moreover, comparison of the coral habitat from this study with others from around the world demonstrated that certain conditions are required for deep-water coral growth, and that these same parameters are common to deep-water reef systems throughout the globe. Further sampling and geochemical analyses of deep-water corals in the region may be used to gain additional insight into the oceanographic conditions surrounding the coral mounds both presently and in the past. As with other previously studied deep-water coral systems, this highlights the potential for the reconstruction of paleo environmental records from deep-water corals in the Straits of Florida.
212

Ulva fasciata protein disulfide isomerase and thioredoxin expression in response to hypersaline stress

Lee, Ju-Chien 06 September 2007 (has links)
This research has investigated the gene expression of protein disulfide isomerase (PDI; EC 5.3.4.1) and thioredoxin (Trx) in the marine macroalga Ulva fasciata Delile in response to hypersaline (90‰) for 1 h. 90‰ induced H2O2 accumulation, reflecting the occurrence of oxidative stress. The contents of free and protein-bound SH were increased by 90‰. Trx transcripts increased in response to 90‰. PDI transcripts and enzyme activities increased in response to 90‰. H2O2 accumulation under 90‰ condition was increased by putrescine (Put) but decreased by spermidine (Spd) and spermine (Spm). By treatment of spermidine and spermine, the contents of free SH was increased and the contents of protein-bound SH decreased, showing that spermidine and spermine can increase free SH against oxidative stress. The gene expression and activity of PDI were further increased by Spd and Spm. Overall, the gene expression of PDI and Trx were responded to 90‰ for 1 hour and were adjusted protein¡VSH in polyamines treatment.
213

Radium Isotope Geochemistry in Groundwater Systems: The Role of Environmental Factors

Vinson, David Stewart January 2011 (has links)
<p>Prior studies of groundwater systems have associated increasing salinity and anoxic conditions with increasing radium (Ra) activities in water due to the decreasing effectiveness of Ra removal processes. However, the components of salinity (e.g. Ca vs. Na and SO<sub>4</sub><sup>2-</sup> vs. Cl<sup>-</sup>-dominated waters), and the relative importance of salinity-sensitive vs. redox-sensitive processes for Ra mobilization, are less well understood. In this research, the response of Ra to hydrochemical change was examined using a multiple tracer approach to obtain detailed information on divalent cation and Ra mobility. A range of salinity and redox conditions was examined in five field-based studies in the United States and Morocco: (1) fresh waters in fractured crystalline rocks in the Piedmont region of North Carolina; (2) the Willcox Basin, an oxic alluvial basin-fill aquifer in southeastern Arizona; (3) the Jordan sandstone aquifer, a carbonate-cemented quartz sandstone in southeastern Minnesota; (4) an unconfined coastal aquifer undergoing salinization in the city of Agadir, Morocco; and (5) the confined, fresh to saline Cretaceous and Pliocene aquifers of the Atlantic Coastal Plain in North Carolina.</p><p> </p><p>In addition to analysis of major element concentrations, trace metal concentrations, and <sup>224</sup>Ra, <sup>226</sup>Ra, and <sup>228</sup>Ra activities, complementary isotope systems were applied to gain insights on the relative stability of chemical processes that remove radium and other alkaline earth metals: (1) strontium isotope ratios (<sup>87</sup>Sr/<sup>86</sup>Sr) trace divalent cation release from sources such as clay and carbonate minerals in the aquifer solids and also indicate conditions in which divalent cation release (rather than uptake) is dominant; (2) boron concentrations and isotopes (&delta;<sup>11</sup>B) coincide with the opposite condition in freshening conditions of the Atlantic Coastal Plain, in which divalent cations are removed in exchange for Na; and (3) sulfur and oxygen isotopes (&delta;<sup>34</sup>S, &delta;<sup>18</sup>O) of sulfate trace sulfate sources and provide information on sulfate-reducing conditions, which can inhibit barite (BaSO<sub>4</sub>) from removing Ra by coprecipitation. In addition, other isotopic and ion measurements trace salinity sources and groundwater residence time, including &delta;<sup>2</sup>H, &delta;<sup>18</sup>O, <sup>3</sup>H, Br<sup>-</sup>/Cl<sup>-</sup>, Na/Cl<sup>-</sup>, and Ca/Na.</p><p>This dissertation documents correlations between salinity and radium in the brackish to saline North Carolina coastal plain aquifer with total dissolved solids (TDS) up to ~18,000 mg L<sup>-1</sup> and to some degree in the Moroccan coastal aquifer, but even the lower-salinity waters (TDS <3000 mg L<sup>-1</sup>) exhibit a range of Ra activities spanning approximately 3 orders of magnitude. Among these low-TDS waters, the highest Ra activities were observed in the anoxic Jordan sandstone aquifer and the lowest were observed in the oxic Willcox Basin aquifer. Although the main control on radium activities in fresh groundwater is the U- and Th-series radionuclide content of the aquifer solids, important secondary controls include the stability of redox-sensitive radium adsorption sites (Mn and Fe oxides), the relative dominance of divalent vs. monovalent cations (e.g. the Ca/Na ratio), formation of the uncharged RaSO<sub>4</sub><sup>0</sup> complex, and/or the saturation state with respect to barite. These processes interact in varied ways in the field-based studies. Increasing radium activities and decreasing <sup>222</sup>Rn/<sup>226</sup>Ra ratios in the North Carolina fractured crystalline rock groundwater system are correlated with increasing Ba, Mn, and Fe concentrations and decreasing dissolved oxygen concentrations, related to weathering and/or organic carbon oxidation. Radium activities in the oxic, neutral to slightly basic Willcox Basin are very low (median <sup>226</sup>Ra activity 2 mBq L<sup>-1</sup>), probably due to a combination of effective Ra removal processes including adsorption to Mn and/or Fe oxides and the overall removal of divalent cations during groundwater evolution in this system. These are the same surface charge conditions that release arsenic, of regional water concern, in this pH range. Radium in Jordan aquifer groundwater is dependent on local variations in solid-phase radionuclide levels, probably hosted in the carbonate cement phase. Also, Ra is inefficiently adsorbed to the aquifer solids in the aquifer's anoxic conditions, resulting in the highest radium levels reported in this dissertation (<sup>226</sup>Ra up to 420 mBq L<sup>-1</sup>) despite apparent barite precipitation that partially removes Ra. Radium-224 activity in the Moroccan coastal aquifer is associated with salinity, but Ra overall is apparently controlled by barite, indicated by conditions near BaSO<sub>4</sub> saturation. Radium activity in the saline waters of the Atlantic Coastal Plain aquifers is associated with TDS concentrations, but the cation exchange properties of the aquifer may provide a major mechanism of Ra removal in the Na-HCO<sub>3</sub><sup>-</sup> and Na-Cl<sup>-</sup> waters. Overall, the complex interaction between groundwater chemistry and Ra-removing processes implies that in waters with TDS below approximately 3,000 mg L<sup>-1</sup>, dissolved solids concentration alone does not fully describe radium's response to hydrochemical conditions, but rather that aquifer-specific examination of Ra removal mechanisms is needed.</p> / Dissertation
214

Contributrion to the improvement of the soil moisture and ocean salinity (SMOS) sea surface salinity retrieval algorithm

Talone, Marco 22 November 2010 (has links)
The European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite was launched on November, 2, 2009 from the Russian cosmodrome of Plesetsk. Its objective is to globally and regularly collect measurements of soil moistre and Sea Surface Salinity (SSS). To do that, a pioneering instru- ment has been developed: the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS), the rst space-borne, 2-D interferometric radiometer ever built; it operates at L-band, with a central frequency of 1.4135 GHz, and consists of 69 antennas arranged in a Y shape array. MIRAS' output are brightness temperature maps, from which SSS can be derived through an iterative algorithm, and using auxiliary information. For each overpass of the satellite an SSS map is produced, with an estimated accuracy of 1 psu (rmse). According to the Global Ocean Data Assimilation Experiment (GODAE) the mission requirement is instead speci ed as 0.1 psu after av- eraging in a 10-day and 2 2 spatio-temporal boxes. In previuos works ((Sabia et al., 2010), or more extensively in Dr. Sabia's Ph.D. thesis (Sabia, 2008)) the main error sources in retrieving SSS from SMOS measurements were determined as: 1. Scene-dependent bias in the simulated measurements, 2. L-band forward modeling de nition, 3. Radiometric sensitivity and accuracy, 4. Constraints in the cost function, and 5. Spatio-temporal averaging. This Ph.D. thesis, is an attempt of reducing part of the aforementioned errors (the relative to the one-overpass SSS (1 - 4)) by a more sophisticated data processing. Firstly, quasi-realistic brightness temperatures have been simulated using the SMOS End-to-end Performance Simulator (SEPS) in its full mode and an ocean model, as provider for geophysical parameters. Using this data set the External Brightness Temperature Calibration technique has been tested to mitigate the scene-dependent bias, while the error introduced by inaccuracies in the L-band forward models has been accounted for by the application of the External Sea Surface Salinity Calibration. Apart from simulated brightness temperatures, both External Brightness Temperature Calibration and External Sea Surface Salinity Calibration have been tested using real synthetic-aperture brightness temperatures, collected by the Helsinki University of Technology HUT-2D radiometer during the SMOS Calibration and Validation Rehearsal Campaign in August 2007 and ten days of data acquired by the SMOS satellite between July 10 and 19, 2010. Finally, a study of the cost function used to derive SSS has been performed: the correlation between measurement mis ts has been estimated and the e ect of including it in the processing have been assessed. As an outcome of a 3-month internship at the Laboratoire LOCEAN in Paris, France, a theoretical review of the e ect of the rain on the very top SSS vertical pro le has been carried out and is presented as Appendix.
215

Seasonal dynamics of planktonic pteropod assemblages in the waters of Liu-chiu Yu Island, Taiwan

Ko, Ju-hsuan 08 September 2010 (has links)
This study investigates the tempo-spatial distribution in species composition and abundance of planktonic pteropods in relation to hydrography in the waters around Liu-chiu Yu Island, southwestern Taiwan from February 2006 to October 2007. In total, we recognized 25 pteropod species belonging to 12 genera and six families, with a mean abundance of 7348 ¡Ó 994 ind./ 1000m3. The five most dominant species were Limacina inflata, Creseis virgula var. conica, Creseis acicula, Limacina trochiformis and Creseis clava, together they accounted for 78.7 % of the total pteropods. The surface sea water temperature, salinity, and phytoplankton concen- tration in the waters around Liu-chiu Yu Island were significantly higher in 2006 than in 2007. Pteropod abundance was higher in spring than in other seasons, and higher in deeper waters than in surface waters. Species number of pteropods was significantly higher in 2007 than in 2006, generally higher in summer and lower in autumn, and higher in deeper waters than in surface waters. Species diversity index of pteropods was generally higher in summer and lower in autumn. Cluster analysis of hydrography included 4 clusters (e.g., 2007 summer, summer and autumn, spring and winter, spring), the 2007 summer cluster was different from other seasons. Pteropod assemblage showed apparent difference between seasons, the variation of pteropod assemblages between stations in spring was higher than other seasons. Linear regression showed that the species number (p < 0.01) and diversity index (p < 0.05) were positively correlated with abundance of fish larvae. Abundance of most dominant species of pteropods was significantly and positively correlated with abundance of fish larvae (e.g., Limacina inflata; Creseis virgula var. conica and Limacina trochiformis) and significantly and negatively correlated with phytoplankton abundance (e.g., Limacina inflata, p < 0.001). In addition to the hydrographic factors, the distribution of pteropods might also be affected by predatory fish larvae and phytoplankton supplement.
216

Impacts of Natural Salt Pollution on Water Supply Capabilities of River/Reservoir Systems

Lee, Chi Hun 2010 May 1900 (has links)
Salinity is a major determinant of where and how water resources are used worldwide. Natural salt pollution severely constrains the beneficial use of large amounts of water in Texas and neighboring states. High salinity loads in several major river/reservoir systems, including the Brazos River, originate largely from salt seeps and springs in isolated areas of the upper river basins located in the Permian Basin geologic region. Research objectives were (1) to improve salinity simulation capabilities of the Water Rights Analysis Package (WRAP) modeling system, and (2) to develop a better understanding of the occurrence, transport, and impacts of salinity in the Brazos River and Lakes Possum Kingdom, Granbury, and Whitney. Water volume budgets and total dissolved solids load budgets were developed for five river reaches covering 405 miles of the upper Brazos River. Methodologies were developed for creating and applying WRAP salinity input datasets. The WRAP modeling system was expanded and applied to the entire Brazos River Basin to investigate alternative modeling premises and impacts of salinity and salinity control measures on water supply capabilities. Water and salinity budget analyses of the Brazos River system based primarily on measured stream flow, reservoir storage, and total dissolved solids data compiled by the U.S. Geological Survey were performed to explore the characteristics of flow and storage volumes and salinity loads and concentrations in the river/reservoir system. WRAP salinity input datasets were developed based on results from the salinity budget study. One dataset was designed and applied specifically for testing salinity routing methods and calibrating salinity routing parameters. A second complete basin salinity dataset was developed and applied to simulate the Brazos River Basin for alternative management strategies. The results of the simulations demonstrate, for example, that previously proposed salt control impoundments can significantly reduce salinity loads and concentrations in the three reservoirs and at all locations on the Brazos River from the impoundments downstream to the Gulf of Mexico. The WRAP salinity simulation features are designed to provide flexibility in combining water quantity simulation datasets from the Texas Water Availability Modeling System or other sources, which may be very complex, with available salinity data which varies in extent and format between different river basins. The modeling capabilities demonstrated by the Brazos River Basin study can be applied in other river basins as well.
217

Hydrographic Characteristics of the Love River

Tsai, Jr-wei 16 September 2004 (has links)
In this study, twenty-seven experiments of transport and hydrographic observations were conducted at 9 bridges along the Love River during the period between 2001/12/20 and 2003/9/10. In each experiment repeated measurements were made at each bridge every two hours for a total period of 12 hours. An additional experiment (the 28th experiment) was conducted at 2004/6/16 in the Chihsien Bridge which consists of continuous measurements of velocity, depth and turbidity with a total length of 27 hours. Our results indicate that the Love River is influenced by the incoming tides from the river mouth up to the Dingxin Bridge. The tidal range is approximately 1m during spring tides (10cm during neap tides) at river mouth. The velocity at the Chihsien Bridge has a high frequency variation with a period of approximately 1 hour and amplitude of 20 cm/s during the 28th experiment. Salinity variations are in phase with tides, while turbidity and tides are out of phase. Harmonic analysis of depth, velocity, salinity and turbidity data all indicate that K1 is the principal tidal constituent followed by M2. River transport in the lower estuary is mainly comprised of two parts: tide and river discharge. The tidal induced transport is estimated to be ¡Ó30 CMS and net river discharge is about 1~9 CMS. The upper estuary is affected by two transport mechanisms: agricultural runoff and rain precipitation. After analyzing the measurement results, the transport of the upper branches is estimated to be 0~0.5 CMS during dry seasons and 1~5 CMS during rainy seasons. The agricultural transport reaches its maximum value in January with an estimated rate of 1~2.8 CMS. For the upper branches of Love River, the ratio£\between the hydraulic depth D and hydraulic radius R is found to reach a constant value of 0.9~1.0 when the transport Q is less than 2CMS, and£\is 0.8~0.9 when Q is greater than 2 CMS. The relationship between Q and the section factor TaDb, where T is the channel width, is found to be TD5/3=7.171Q (Dingxin Bridge) and TD5/3=0.744Q (Hougang Bridge) based on Manning formula. Finally, the relationship between Q and D is found to be D=1.811Q0.2981 (Longxin bridge) and D=0.266Q0.256 (Hougang Bridge).
218

Effect of environmental factors on the spawning, egg hatching and metamorphosis of nauplius of the shrimp Acetes intermedius (Omori, 1975)

Chen, Yung-Hui 31 July 2000 (has links)
The planktonic shrimp Acetes intermedius is an ecologically and commercially important species. Since it was described by Omori(1975) as a new species, there have been relative few studies focused on the reproduction of this species. The aim of this study is to examine the spawning, egg hatching, larval development of A. intermedius and the related environmental factors. The newly released eggs of Acetes intermedius were round, 200 um in diameter in average, transparent, demersal and were usually green in color. The cleavage pattern of developing egg is holoblastic. Larval stages could be divided into four stages: nauplius, protozea, zoea and postlarva. Nauplius, protozoea and zoea can be further divided into 4, 3 and 2 substages, respectively. At water temperature 30 ¢J and salinity 25 psu, hatching of nauplius was around 10-11 h after spawning while protozoea, zoea and postlarva occurred around 29h, 5-6 and 7 days after spawning, respectively. Newly released eggs were introduced directly into different temperature-salinity combinations. The results revealed that eggs failed to hatch at 15¢J at all salinities tested and at salinities 0 to 10 psu at all temperatures examined. Hatching success started to decrease at salinity 15 psu at 30¢J and at 20 psu at both 25¢J and 20¢J. When salinity was not lower than 25 psu, the hatching success reaches nearly 90 % in average and is generally similar among temperatures tested. Hatching started at about 10, 14 and 28h after spawning at temperatures 30, 25, 20¢J, respectively. At salinity 25 psu, hatching time was the shortest at both 25 and 30¢J, whereas it was similar among salinities at 20¢J. Eggs and nauplii I hatched at 30 ¢J, 30 psu were incubated in the different temperature-salinity combinations. It took eggs incubated at salinities ranging from 20 to 35 psu about 28, 45 h and 5 days to develop into protozoea I at 30, 25 and 20 ¢J, respectively. Nauplii usually started to metamorphose earlier at 25 and 30 psu than at 35 and 20 psu at 25 and 30¢J while no significant trend in metamorphosis time was found among different salinities at 20¢J. Nearly 90% of nauplii metamorphosed into protozoea I at 25 and 30¢J while the metamorphosis rate of nauplii was greatly reduced at 20¢J. The metamorphosis rate was usually higher around 20-25 psu and lower at 15 and 35 psu in all temperatures examined. While spawning, the gravid females swam near the water surface and were rapidly beating pleopods. The eggs were directly released into water. Spawning usually took place at night but the timing is generally peaked around midnight. The gravid females spawned in the early spring before midnight while they spawned after midnight in summer. The spawning timing is delayed at low temperature (24¢J) while it is not affected by high temperature (30¢J). The salinity did not show any effects on spawning but the hatching success of eggs released at 15 and 35 psu was significantly lower than those at 20-30 psu. The gravid females were tended to be endogenous timed to spawn in the night since spawning was not affected by absence of presence of light.
219

Treatment of salty wastewater by constructed wetlands--A case study of Datan Wetland Park, Dapeng Bay, Taiwan

Wu, Cheng-Ying 10 June 2008 (has links)
The Dapeng Bay National Scenic Area will be planned as an interna-tional level tourism site. In order to improve the water quality in bay area, the administration authority has removed oyster farm. However, sewage and aquaculture wastewater from the communities and fish ponds around the bay area were still discharged continuously. After careful assessment, The Dapeng Bay National Scenic Area Administration authority decided to use constructed wetlands to treat such kinds of wastewater. In this study, the treatment efficiencies of Datan Constructed Wetland Park were investigated. According to the experimental results, we found that the remove efficiencies of SS, Chl-a, and TOC were not good enough, while the other parameters, such as OP, TP, NO2-, and NO3- their all re-moval efficiencies were all above 40¢H.The removal efficiencies of NH3, TKN and TN were all above 60%. However, the removal efficiencies of turbidity and BOD were found equal to 30%. Generally, TN was removed by the process as of nitrification and denitrification, but the nitrification of the subsurface flow¡]SSF¡^part of wetland was perforated worse, which caused the org-N and NH4+-N was not availably to become the NH3, NO2- and NO3-. Because of this reason, the removal effect of Org-N was not very significant. The parameter of TOC was affected by the fixation of CO2 through photosynthesis of autotrophs, and the respiration and denitrification of heterotrophs. The sediment also could provide organic carbon source for denitrification. Photosynthesis and carbon source would cause the re-moval efficiency of TOC become worse than synthesis. In the wetland, the decrease rate of salinity was found above 20¢H.
220

Effects of temperature, light intensity and salinity on asexual reproduction of the scyphozoan, Aurelia aurita (L.) in Taiwan

Liu, Wen-Cheng 06 February 2009 (has links)
Jellyfish blooms create problems worldwide, which may increase with global warming, water pollution, and over-fishing. Benthic polyps (scyphistomae) asexually produce buds and small jellyfish (ephyrae), and this process may determine the population size of the large, swimming scyphomedusae. Environmental factors that affect the asexual reproduction rates include food, temperature, salinity, and light. In the present study, polyps of Aurelia aurita (L.), originated from Tapong Bay, southwest Taiwan, were studied in different combinations of temperatures (T), light intensities (L), and salinities (S). In the T (20, 25, 30¢XC) ¡Ñ L (372, 56, and 0 lux) experiment which was with a 12 h light-12 h dark photoperiod, production of new buds decreased with warmer temperatures and stronger light intensity. Warm temperatures accelerated strobilation and increased the daily production of ephyrae. The proportion of ephyrae to total asexual reproduction (new buds + ephyrae) increased dramatically in warmer temperatures and stronger light. Survival period was reduced at the highest temperature. Strobilation did not occur at the lowest temperature in darkness. All measures of total asexual reproduction indicated that medium to high temperatures would lead to faster production of more jellyfish; however, continuous high temperatures might result in high polyp mortality. Light intensity affected asexual reproduction less than did temperature, only significantly accelerating the strobilation rate. Because the interactive effects of light and temperature were significant for polyp survival time and the production of jellyfish per polyp, combined light and temperature effects are likely important for strobilation in situ. In the T (27, 31, 35¢XC) ¡Ñ S (25, 30, and 35) experiment which was in dark environment, production of new buds decreased with higher temperatures and salinity. The proportion of ephyrae to total asexual reproduction (new buds + ephyrae) increased with warmer temperatures, but survival period was reduced at the highest salinity, and strobilation was substantially reduced, even though the temperature was warmer compared to the T ¡Ñ L experiment. Salinity affected asexual reproduction less than did temperature, only significantly affecting production of new buds, and slightly affecting survival period and the proportion of ephyrae to total asexual reproduction. According to these two experiments, warmer temperature may accelerate strobilation in light condition and lead to better yield of swimming jellyfish, however continuously warm temperature would reduce the yield by decreasing budding and higher mortality. Complete dark led to much less strobilation, especially at low temperatures, suggesting that the existence of light might be more important than light intensity. The effects of salinity on asexual reproduction were not as conspicuous as that of temperature and light.

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