scholarly journals Varietal Differences in Seedling Traits under the Low Dissolved Oxygen Level in Water-Seeded Rice

2000 ◽  
Vol 3 (4) ◽  
pp. 375-376 ◽  
Author(s):  
Jong Gun Won ◽  
Tomohiko Yoshida
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Level ◽  
Varietal Differences ◽  
Low Dissolved Oxygen ◽  
Seedling Traits

scholarly journals Screening Cultivars at Low Dissolved Oxygen Level for Water-seeded Rice

2000 ◽  
Vol 3 (2) ◽  
pp. 112-113 ◽  
Author(s):  
Jong Gun Won ◽  
Tomohiko Yoshida
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Level ◽  
Low Dissolved Oxygen

Some Effects of Temporary Exposure to Low Dissolved Oxygen Levels on Pacific Salmon Eggs

1958 ◽  
Vol 15 (2) ◽  
pp. 229-250 ◽  
Author(s):  
D. F. Alderdice ◽  
W. P. Wickett ◽  
J. R. Brett
Keyword(s):  
Oxygen Consumption ◽  
Dissolved Oxygen ◽  
Oxygen Demand ◽  
Oxygen Availability ◽  
Oncorhynchus Keta ◽  
Hatching Rate ◽  
Oxygen Level ◽  
Low Oxygen ◽  
Low Dissolved Oxygen ◽  
Oxygen Levels

Eggs of the chum salmon (Oncorhynchus keta) were exposed to various constant levels of dissolved oxygen for a period of seven days. The procedure was repeated with fresh egg samples at various developmental stages. Temperatures were constant at 10 °C. from fertilization to hatching. Estimates of oxygen consumption uninhibited by low dissolved oxygen levels were obtained at various stages of egg development for whole eggs and also on the basis of the weight of larvae, excluding the yolk. Eggs were most sensitive to hypoxia between 100–200 Centigrade degree-days and compensated for reduced oxygen availability by reducing the oxygen demand and rate of development. Very low oxygen levels at early incubation stages resulted in the production of monstrosities. At about the time the circulatory system becomes functional the compensatory reduction in rate of growth under hypoxial conditions is reduced, but eggs no longer survive extreme hypoxial conditions. Eggs subjected to low dissolved oxygen levels just prior to hatching hatch prematurely at a rate dependent on the degree of hypoxia. The maximum premature hatching rate corresponded approximately with the median lethal oxygen level. Estimated median lethal levels rose slowly from fertilization to hatching. Oxygen consumption per egg rose from fertilization to hatching while the consumption per gram of larval tissue declined from a high to a low level at about the time of blastopore closure. Subsequently, a slight rise in the rate occurred up to a level which was more or less constant to hatching. "Critical" dissolved oxygen levels were calculated and they appear to define the oxygen level above which respiratory rate is unmodified by oxygen availability. Critical levels ranged from about 1 p.p.m. in early stages to over 7 p.p.m. shortly before hatching.

A study of water quality in an urban river and potential improvement using a prototype instream aerator

1989 ◽  
Vol 16 (3) ◽  
pp. 308-316 ◽  
Author(s):  
C. A. Town ◽  
D. S. Mavinic ◽  
B. Moore
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Data Base ◽  
Chlorophyll A ◽  
Late Summer ◽  
Urban River ◽  
Agricultural Activity ◽  
Fish Kills ◽  
Low Dissolved Oxygen ◽  
Oxygen Levels

Urban encroachment and intensive agricultural activity within the Serpentine–Nicomekl watershed (near Vancouver, B.C.) have caused a series of fish (salmon) kills on the Serpentine River since 1980. Low dissolved oxygen was responsible for these kills. This field project investigated some of the dynamic chemical and biological relationships within the river, as well as the use of an instream aerator as a temporary, in situ, water quality improvement measure. Weekly sampling for a 6-month period during the latter half of 1985 established a solid data base for deriving and interpreting meaningful interrelationships. A strong correlation between chlorophyll a and dissolved oxygen levels before the algae die-off supported the hypothesis that algae blooms dying in the fall could create a serious oxygen demand. Because of these environmental conditions, the river is unable to sustain healthy dissolved oxygen levels during this period. As such, a prototype, 460 m artificial aeration line was designed, installed, and monitored to evaluate its potential for alleviating low dissolved oxygen conditions and improving overall water quality during the critical fall period.The instream aerator ran continuously for over 2 months, starting in September 1985. Despite better-than-expected weather conditions (i.e., cool, wet weather) and relatively high dissolved oxygen levels during the fall of 1985, the data base appeared to support the use of this prototype aeration unit as a means of "upgrading" a stretch of an urban river subject to periodic, low dissolved oxygen levels. As a result, a 2-year follow-up study and river monitoring was initiated. In both 1986 and 1987, late summer and early fall river conditions resulted in the potential for serious salmon kills, due to higher-than-normal river temperatures and very low dissolved oxygen. In both instances, the instream aerator prevented such fish kills in a key stretch of the river. Expansion of the system to include other critical stretches of the Serpentine and other urban river systems, near Vancouver, is being considered. Key words: algae, aerator, chlorophyll a, eutrophic, fish kills, instream aeration, river improvement, urban river.

Effects of Low Dissolved Oxygen Events on the Macrobenthos of the Lower Chesapeake Bay

Estuaries ◽  
1992 ◽  
Vol 15 (3) ◽  
pp. 384 ◽  
Author(s):  
Daniel M. Dauer ◽  
Anthony J. Rodi ◽  
J. Ananda Ranasinghe
Keyword(s):  
Dissolved Oxygen ◽  
Chesapeake Bay ◽  
Low Dissolved Oxygen
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