Physiological performance of three calcifying green macroalgae Halimeda species in response to altered seawater temperatures

The effects of seawater temperature on the physiological performance of three Halimeda species were studied for a period of 28 d.Five treatments were established for Halimeda cylindracea,Halimeda opuntia and Halimeda lacunalis,in triplicate aquaria representing a factorial temperature with 24°C,28°C,32°C,34°C and 36°C,respectively.The average Fv/Fm of these species ranged from 0.732 to 0.756 between 24°C and 32°C but declined sharply between 34°C(0.457±0.035)and 36°C(0.122±0.014).Calcification was highest at 28°C,with net calcification rates(Gnet)of(20.082±2.482)mg/(g·d),(12.825±1.623)mg/(g·d)and(6.411±1.029)mg/(g·d)for H.cylindracea,H.opuntia and H.lacunalis,respectively.Between 24°C and 32°C,the specific growth rate(SGR)of H.lacunalis(0.079%–0.110%d–1)was lower than that of H.cylindracea(0.652%–1.644%d–1)and H.opuntia(0.360%–1.527%d–1).Three Halimeda species gradually bleached at 36°C during the study period.Malondialdehyde(MDA)and proline levels in tissues of the three Halimeda were higher in 34–36°C than those in 24–32°C.The results indicate that seawater temperature with range of 24–32°C could benefit the growth and calcification of these Halimeda species,however,extreme temperatures above 34°C have negative impacts.The measured physiological parameters also revealed that H.cylindracea and H.opuntia displayed broader temperature tolerance than H.lacunalis.

Hydro-environmental Characteristics of Seawater around Boubyan Island,Kuwait Using Annual Variations of Seawater Temperature,Salinity and Tide Fluctuations

The temporal and spatial variations of seawater temperature,salinity,and tidal fluctuations are important parameters for understanding the hydrodynamic,water quality,and marine biological activity in the seawater.It is also important to study and understand the probability and statistical aspects of these parameters for the planning and implementation of different types of marine projects.These parameters were measured at five different locations around Boubyan Island,Kuwait,for a span of almost one year during 2015-16.Based on the analysis of the measured data,it is found that the seawater salinity has varied from 34.14 to 48.31 ppt.The seawater temperature is also found to vary from 10.83 oC to 35.67 oC.The seawater level has varied from-2.694 m to 2.378 m with respect to the mean sea level.It is found that the peak of the probability density of seawater level is flat valued,whereas the probability density of salinity and seawater temperature is multimodal.A comparison of present and past measured seawater temperatures revealed that in Khor Al-Sabiya,the seawater temperature is increasing at the rate of 0.034 oC/year,which clearly indicates the effect of global warming.A similar study reveals that the annual average increase in salinity at Khor Al-Sabiya is 0.38 ppt,which clearly indicates a significant reduction of freshwater flow from Shatt Al-Arab into the Arabian Gulf.Since Kuwait is investing in many projects around the Boubyan Island,the results of this study will be useful for the integrated and sustainable development of Boubyan and Failaka Islands in Kuwait.

Experimental Research on Temperature Sensing of Seawater Based on Three Interferometers Incorporated With Bow Tie Fiber

Three interferometers(the Sagnac sensor,the linear polarization interferometer,and the reflecting polarization interferometer)incorporated with the bow tie fiber are proposed to detect the seawater temperature.Bow tie fiber,a kind of polarization maintaining fiber,has stress induced birefringence.The three interferometers are categorized as transmission and reflection types to analyze the sensing principles.Related experiments are performed to explore the influence of the wavelength and length of the bow tie fiber on the sensitivity and free spectral range(FSR).The sensitivity and FSR both increase with the wavelength increasing.The sensitivity fluctuates in a small range and FSR decreases with the length increasing.The reflecting polarization interferometer has the bigger sensitivity of–1.19 nm/℃than the other two.And it has the advantages of easy fabrication,simple operation,and good stability,so it is applicable in real ocean exploration.Our work can provide a reference to researchers who do oceanographic research.