Temperature stratification and photosynthetically active radiation distribution in the Zostera noltii Hornemann canopy under shallow water conditions at different solar elevation angles (the Black sea)

2020 ◽  
pp. 160-178
Author(s):  
Александр Васильевич Празукин ◽  
Юрий Константинович Фирсов ◽  
Александр Александрович Латушкин ◽  
Анна Алексеевна Чепыженко
Keyword(s):  
Black Sea ◽  
Photosynthetically Active Radiation ◽  
Light Availability ◽  
Temperature Stratification ◽  
The Black Sea ◽  
Shallow Waters ◽  
Zostera Noltii ◽  
Active Radiation ◽  
Solar Elevation ◽  
Radiation Distribution

Морские травы экологически важны, но чрезвычайно уязвимы перед антропогенными изменениями в прибрежных зонах, которые влияют на доступность света в этих экосистемах. При разной высоте Солнца над горизонтом в зондирующем режиме проводилось одновременное измерение значений температуры воды и интенсивности фотосинтетически активной радиации (IPAR) по профилю полога Zostera noltii Hornemann (высота полога 32 см.) в мелководной части Казачьей бухты (г. Севастополь, Черное море, 44°57′26″ с.ш., 33°40′33″ в.д.). Для полога Z. noltii характерен одномодальный тип вертикального распределения биомассы с максимумом (65,7 г (сухой массы) / м2) в его нижней части. Рассматривается изменение температурной стратификации и распределения IPAR по профилю растительного полога Z. noltii в течение светового дня. Seagrass is environmentally significant but extremely vulnerable in coastal areas to anthropogenic changes, which affect light availability. Simultaneous measurements of water temperature and photosynthetically active radiation (PAR) intensity in the sounding mode were taken at different solar elevation angles for the Zostera noltii Hornemann canopy (canopy height 32 cm) in shallow waters of the Cossack Bay (Sevastopol, the Black Sea, 44°57′26″ с.ш., 33°40′33″ в.д.). Z. noltii canopy is characterized by a unimodal type of biomass vertical distribution with its maximum (65,7 g (dry matter)/m2) in the lower part. Temperature stratification and IPAR distribution changes within the Z. noltii vegetation canopy profile during daylight hours are considered.

scholarly journals New considerations regarding underwater noise in Black Sea

2018 ◽  
Vol XIX (1) ◽  
pp. 381-392
Author(s):  
Pricop M
Keyword(s):  
Black Sea ◽  
Sea Water ◽  
Coherence Function ◽  
Measurement Techniques ◽  
Measuring System ◽  
The Black Sea ◽  
Shallow Waters ◽  
Underwater Noise ◽  
Noise Sources ◽  
Acoustic Signature

The development and standardization of measurement techniques for underwater noise sources are important to both military and civil fields regarding the reduction of sound emitted by commercial and military ships. This paper presents new analysis of the acoustic signature of a small vessel during a voyage in the Black Sea. The measurements were made when the ship was moored in shallow waters. The measuring system had 3 hydrophones that were positioned at different depths. Using the coherence function, it was determined the correlation between the recordings. The results were analysed to determine the acoustic signature of the ship. Thermal variations of sea water and effects of sound reflection from the bottom of the sea were taken into account. Conclusions have been made regarding the utility of this type of analysis and the levels of underwater noise in the shallow waters of the Black Sea.

scholarly journals Effects of Photosynthetically Active Radiation on Vegetative Growth of Texas Wild Rice and Consequences for Population Augmentation

HortScience ◽  
2020 ◽  
Vol 55 (7) ◽  
pp. 1000-1004
Author(s):  
Michele L. Crawford ◽  
Paula S. Williamson ◽  
Tina M. Waliczek ◽  
David E. Lemke ◽  
Thomas B. Hardy
Keyword(s):  
Photosynthetically Active Radiation ◽  
Vegetative Growth ◽  
Wild Rice ◽  
Light Availability ◽  
Ex Situ ◽  
Control Group ◽  
Ambient Light ◽  
Active Radiation ◽  
San Marcos ◽  
The Impact

As urbanization and urban sprawl increases, habitat for native flora and fauna often becomes threatened. Reestablishing wildlife habitats within designed landscapes has become increasingly popular with horticultural consumers, who are becoming more aware of the benefits of using native plants and the threats of invasive species. Texas wild rice (Zizania texana Hitchc.) is a federally endangered aquatic plant known to occur only in the San Marcos River, Hays County, TX. The objective of this study was to experimentally test the impact of light availability on the vegetative growth of Texas wild rice (TWR) ex situ. The effect of photosynthetically active radiation (PAR) was tested by establishing treatment and control groups of plants in a river raceway located on the campus of Texas State University, San Marcos, TX. At the onset of the experiment, baseline growth data were collected on a random sample of 15 plants to determine starting conditions. The 75 plants within the control and treatment groups were also randomly selected. Two sequential experimental trials were designed involving the same treatment of PAR reductions with 15 TWR plants in the control group (100% of ambient PAR conditions) and 15 within each of four experimental treatment units. Treatments included a reduction in ambient light values at each of the following rates: PAR reduced by 10% (90% ambient light), 20% (80% ambient light), 40% (60% ambient light), and 80% (20% ambient light). Results of the study indicated high shade areas contained reduced areal coverage or complete lack of TWR. There was a significant decrease in both above and below ground biomass, with an 80% reduction in available PAR (20% available ambient light), and other growth parameters of TWR were negatively impacted by reductions in PAR greater than 40% (60% ambient light availability) during the short-term early establishment growth period. Therefore, light availability is a critical environmental factor that must be given consideration when deciding areas of the river to plant TWR for population augmentation.

scholarly journals Divergent symbiont communities determine the physiology and nutrition of a reef coral across a light-availability gradient

2020 ◽  
Vol 14 (4) ◽  
pp. 945-958 ◽  
Author(s):  
Christopher B. Wall ◽  
Mario Kaluhiokalani ◽  
Brian N. Popp ◽  
Megan J. Donahue ◽  
Ruth D. Gates
Keyword(s):  
Photosynthetically Active Radiation ◽  
Light Availability ◽  
Reef Coral ◽  
Carbon Assimilation ◽  
Montipora Capitata ◽  
Active Radiation ◽  
Reef Corals ◽  
Species Specific ◽  
First Time ◽  
Symbiont Species

AbstractReef corals are mixotrophic organisms relying on symbiont-derived photoautotrophy and water column heterotrophy. Coral endosymbionts (Family: Symbiodiniaceae), while typically considered mutualists, display a range of species-specific and environmentally mediated opportunism in their interactions with coral hosts, potentially requiring corals to rely more on heterotrophy to avoid declines in performance. To test the influence of symbiont communities on coral physiology (tissue biomass, symbiont density, photopigmentation) and nutrition (δ13C, δ15N), we sampled Montipora capitata colonies dominated by a specialist symbiont Cladocopium spp. or a putative opportunist Durusdinium glynnii (hereafter, C- or D-colonies) from Kāne‘ohe Bay, Hawai‘i, across gradients in photosynthetically active radiation (PAR) during summer and winter. We report for the first time that isotope values of reef corals are influenced by Symbiodiniaceae communities, indicative of different autotrophic capacities among symbiont species. D-colonies had on average 56% higher symbiont densities, but lower photopigments per symbiont cell and consistently lower δ13C values in host and symbiont tissues; this pattern in isotope values is consistent with lower symbiont carbon assimilation and translocation to the host. Neither C- nor D-colonies showed signs of greater heterotrophy or nutritional plasticity; instead changes in δ13C values were driven by PAR availability and photoacclimation attributes that differed between symbiont communities. Together, these results reveal Symbiodiniaceae functional diversity produces distinct holobionts with different capacities for autotrophic nutrition, and energy tradeoffs from associating with opportunist symbionts are not met with increased heterotrophy.

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