Changes In Seawater Temperature Research Articles

Reverse osmosis seawater desalination for power plant

The Miyazu Energy Research Center of the Kansai Electric Power Company in Kyoto prefecture has an electric power generating facility of 750,000 kW. As it is located in a small peninsula of a remote area, fresh water cannot easily be obtained and almost all of the fresh water required is provided by seawater desalination. The seawater desalination facility consists of two trains of the reverse osmosis (RO) equipment which produce 1600 m 3/d fresh water. For the RO membrane, spiral-type polyether composite membranes (PEC-1000) made by Toray were adopted; there are 300 modules (60 vessels). The pretreatment, the dual-media filter and the single-medium filter are equipped in series and ferric chloride and sodium hypochlorite are injected for the removal of suspended particles in the raw seawater and the prevention of bacterial growth in the equipment. Before feeding the seawater to the membrane modules, the residual chlorine and dissolved oxygen are removed completely by vacuum declaration and addition of sodium bisulfite. Then the seawater is pressurized to 66 kg/cm 3 and fed to the membrane modules. The seawater temperature changes from 9–37°C according to the season, and it causes the fluctuation of the fresh water production. In order to avoid scale formation on the membrane surface, the maximum recovery ratio was set at 45% (1800 m 3/d). Therefore, the number of the membrane modules in operation is changed by the seawater temperature to keep the fresh water production between the minimum (1600 m 3/d). The permeated water is decarbonated, and sodium hydroxide is added to adjust the pH between 6.5–7.5. The concentrated brine is discharged after oxidizing sodium bisulfite by aeration. The facility was constructed in 1988 and has been operating smoothly without serious problems since then. The outline of the operational results is reported in the paper.

The effects of salinity and temperature on the density and sinking velocity of eggs of the calanoid copepod Acartia tonsa Dana

The potential effects of changes in seawater salinity and temperature on the density and sinking velocity of the eggs of the coastal/estuarine calanoid copepod Acartia tonsa Dana were evaluated in the laboratory using the Percoll density gradient centrifugation method. The developmental stage of the eggs also was investigated to determine if the density and sinking velocity of the eggs changed as the eggs developed. Results of developmental stage experiments for A. tonsa eggs spawned in seawater at a salinity of 15%. and a temperature of 20 °C indicated no statistically significant differences in measured mean egg densities or calculated sinking velocities between the different developmental stage groups (range of egg densities of 1.083 to 1.088 g/ml). Results of salinity experiments indicated that, for eggs spawned at a salinity of 15%. and a temperature of 20 °C, the measured mean egg density was 1.066 g/ml, while for eggs spawned at a salinity of 31%. and 20 °C, mean egg density was 1.086 g/ml. Measured mean egg densities and calculated sinking velocities were significantly different between the two experimental salinity conditions. Salinity crossover experiments, designed to investigate the effects of post-spawning changes in seawater salinity on the density or sinking velocity of the eggs, demonstrated a statistically significant change in density and sinking velocity for eggs which were exposed to different experimental salinities post-spawning. These results indicate osmoregulation by the eggs. Results of the temperature experiments demonstrated that the mean densities and sinking velocities of eggs spawned at a temperature of 20 or 30 °C (salinity of 31%.) were significantly different. For these experiments, eggs spawned at a temperature of 20 °C and 31%. salinity exhibited a mean egg density of 1.087 g/ml. Eggs spawned at a temperature of 30 °C and a salinity of 31%. exhibited a mean egg density of 1.077 g/ml. The results of the salinity and temperature experiments demonstrated that both salinity and temperature significantly affected the density and sinking velocity of the eggs of A. tonsa. At temperatures ≥20 °C, typical sinking velocities

Bathymetric and isotopic evidence for a short-lived Late Ordovician glaciation in a greenhouse period

The end Ordovician glaciation is distinct among Phanerozoic glaciations in that CO 2 , levels were generally high, yet major continental ice sheets accumulated on the Gondwana supercontinent. New oxygen isotopic data indicate substantial changes in sea-water temperatures and ice volume coinciding with glacio-eustatic changes in sea level reflecting the growth and decay of the Gondwana ice cap. Major glaciation was apparently confined to the Hirnantian and was 0.5-1 m.y. long, rather than the 35 m.y. of earlier estimates. Carbon isotope values indicate significant changes in carbon cycling as the oceans changed from a state with warm saline bottom waters to a state with cold deep-water circulation and then back again. We believe that the changes in the carbon cycle effected a reduction in P CO 2 levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world.

九十九里海域におけるダンベイキサゴの産卵期

The reproductive cycle of the sand snail Umbonium (Suchium) giganteum was investigated on the basis of samples taken monthly during the period from December 1986 to June 1988. Seasonal changes in the gonadal index, size-frequency distribution of the ovarian egg, and the results of a spawning experiment in the laboratory were analyzed to determine the spawning season.The gonadal index was low in August and September, but high during the period from December to June; the index values show a bimodal type of distribution with peaks in November-December and April. This is highly correlated to the seasonal changes in seawater temperature. As indicated from the period of maximum ripeness of gonad and the spawning observed in the laboratory, it is concluded that the spawning of U. (S.) giganteum occurs twice a year, i.e. in winter (December and January) and in late spring to early summer (April, May and June), and that the latter is the main spawning season.

Diurnal periodicity of spore-shedding in some red algae of Visakhapatnam coast

Experiments were conducted for 2yr from September 1976 to August 1978 on the diurnal periodicity of spore-discharge in Gelidium pusillum (Stackhouse) Le Jolis, Pterocladia heteroplatos (Boergesen) Umamaheswara Rao & Kaliaperumal, and Gelidiopsis variabilis (Greville) Schmitz, growing in the intertidal region of Visakhapatnam. Regular diurnal periodicity of spore-shedding was found with peak output of spores during night-time in Gelidium and during daytime in Gelidiopsis. The pattern of diurnal curves for these two species varied seasonally with a 4-h delay in the peak shedding of spores during December to February–March. Results obtained with Pterocladia were irregular without any seasonal fluctuations in the daily liberation of spores. The variation in the diurnal rhythm of spore-shedding in Gelidium and Gelidiopsis may be due to seasonal changes in sea-water temperature.

SEASONAL PHOTOSYNTHETIC PERFORMANCE OF MACROCYSTIS INTEGRIFOLIA (PHAEOPHYCEAE)1

ABSTRACTThe seasonal photosynthetic performances of three age classes of blades of Macrocystis integrifolia Bory were estimated by studying their photosynthetic rate vs. irradiance curves and pigment contents for 15 months. All blade types were irradiance‐saturated between 25 and 70 μE · m−2· S−1. Young and mature blade tissues had higher photosynthetic maxima and initial slopes on an area basis than older blade tissue. The latter, however, had pigment concentrations similar to those in mature blade tissues. All these parameters varied on a seasonal basis. The photosynthetic maxima ranged from 0.1–0.8 μmol · C · cm−2· h−t and showed two peaks, one in late summer‐early fall and the other in late winter. Changes in initial slope and pigment concentrations in the blade tissues suggest that, changes in the size or efficiency of electron transfer in the photosynthetic unit occur. These data are discussed in relation to changes in seawater temperature and nitrate concentrations.

Avoidance behaviour of Asterias rubens to extracts of Mytilus edulis, solutions of bacteriological peptone, and selected amino acids

The effect of some homogenates, peptones and amino acids upon the positive rheotactic behaviour of Asterias rubens L. is studied. It was found that homogenates of Mytilus edulis, solutions of bacteriological peptone L 37, L-glutamic acid and a mixture of 10 common amino acids acted as “repellents” and altered the positive rheotactic behaviour of A. rubens. The experimental evidence suggests that the active compound(s) of the homogenates of M. edulis and of the solution of L 37 is a heat stable substance whose molecular weight is lower than ca. 30,000. It was found that A. rubens sensed L-glutamic acid in concentrations of the part per million range. Sinergistic interaction was found between L-glutamic acid and a mixture of one or more other 9 common amino acids. It is shown that the sensitivity of A. rubens to one of the “repellents”, bacteriological peptone L 37, changes during the year. Among other factors, seasonal changes in sea-water temperature could account for this.

Acquisition and loss of cold-tolerance in adult barnacles (Balanus balanoides) kept under laboratory conditions

In the laboratory, Balanus balanoides (L.) barnacles maintained without food at 5°C over the winter to summer period remained cold-tolerant. Winter animals maintained at 5°C and fed Artemia nauplii under a controlled light-dark regime until mid-summer lost this cold-tolerance. Summer animals, maintained without food at 5° or 15°C until midwinter, became cold-tolerant. Summer and winter animals subjected to increased (or decreased) ambient salinity for 48 h showed a small decrease (or increase) in their lower median lethal temperature (MLT—defined as the temperature at which 50% of the animals die after 18 h exposure to air). Summer animals subjected to desiccation for 48 h also showed a small decrease in their lower MLT. It is concluded that the seasonal changes in cold-tolerance of adult barnacles are probably induced by a combination of environmental factors including food availability, light intensity, day-length and changes in ambient sea-water temperatures. Development of cold-tolerance in the winter did not depend upon fertilisation. Changes in intra-cellular solute concentration which accompany adaptation to changes in ambient salinity or desiccation do not appear to be related to the seasonal changes in cold-tolerance.