Heat-stress and light-stress induce different cellular pathologies in the symbiotic dinoflagellate during coral bleaching

Coral bleaching is a significant contributor to the worldwide degradation of coral reefs and is indicative of the termination of symbiosis between the coral host and its symbiotic algae (dinoflagellate; Symbiodinium sp. complex), usually by expulsion or xenophagy (symbiophagy) of its dinoflagellates. Herein, we provide evidence that during the earliest stages of environmentally induced bleaching, heat stress and light stress generate distinctly different pathomorphological changes in the chloroplasts, while a combined heat- and light-stress exposure induces both pathomorphologies; suggesting that these stressors act on the dinoflagellate by different mechanisms. Within the first 48 hours of a heat stress (32°C) under low-light conditions, heat stress induced decomposition of thylakoid structures before observation of extensive oxidative damage; thus it is the disorganization of the thylakoids that creates the conditions allowing photo-oxidative-stress. Conversely, during the first 48 hours of a light stress (2007 µmoles m−2 s−1 PAR) at 25°C, condensation or fusion of multiple thylakoid lamellae occurred coincidently with levels of oxidative damage products, implying that photo-oxidative stress causes the structural membrane damage within the chloroplasts. Exposure to combined heat- and light-stresses induced both pathomorphologies, confirming that these stressors acted on the dinoflagellate via different mechanisms. Within 72 hours of exposure to heat and/or light stresses, homeostatic processes (e.g., heat-shock protein and anti-oxidant enzyme response) were evident in the remaining intact dinoflagellates, regardless of the initiating stressor. Understanding the sequence of events during bleaching when triggered by different environmental stressors is important for predicting both severity and consequences of coral bleaching

Effect of combined thyroxine and cortisol treatment on hatching of eggs, post-embryonic growth and survival of larvae of Heteropneustes fossilis

In order to record the effects of thyroxine and cortisol (individual/combined) on hatching, post-embryonic growth and survival of larvae of Heteropneustes fossilis, newly fertilized eggs were given bath immersion treatments of L-thyroxine (T sub(4); 0.05 mg/l), cortisol (0.50 mg/l) and T sub(4)+ cortisol (0.05 mg/l+0.50 mg/l) for 15 days. Hatching of eggs, growth and survival of the larvae improved significantly (P<0.001) in the hormone treated groups as compared to those of control. The frequency of deformities was reduced in the combined hormone treatment group. The present observations suggest that the advanced digestive function probably induced by T sub(4)+cortisol treatment might have resulted in improvement in food utilization during the critical phases of first feeding and promoted vital developmental processes resulting in uniform growth, decreased mortality, better survival and transformation of larvae to juveniles. This combined hormone therapy appears to have practical utility in fish hatchery practice for better success in larval rearing.

Comparison of effectiveness of heat and cold shocks applied in the induction of gynogenesis in Clarias gariepinus (Burchell)

An experiment was conducted to optimize the procedure of gynogenesis in African catfish, Clarias gariepinus by suppressing meiotic and mitotic cell divisions in fertilized eggs. Gynogensis was conducted by fertilizing normal eggs with UV-irradiated sperm followed by either heat or cold shocking Irradiation of spermatozoa was given for a duration of 1 min and the eggs were fertilized in vitro. Cold shock at a temperature of 3± 1°C for a duration of 30 and 60 min and heat shock at a temperature of 39± 1°C for a duration of 1 and 2 min was applied to induce diploidy. Higher percentage of hatching (68.66) was observed for meiotic gynogens at a shock temperature of 39± 1°C for a duration of 1 min, 5 min after fertilization (af). Higher percentage of mitotic gynogenetic induction (15.33) was observed at a temperature shock of 39± 1°C for a duration of 1 min, 30 min af.

The Gjerstad kiln: a combined hot and cold smoking kiln

A combined hot and cold smoking kiln has been constructed for use at Lake Turkana, Kenya. Used for cold smoking, the kiln's main advantages over the traditional kilns used in this area are its greater smoking capacity and lower firewood consumption. Having the option of using the same smoke house for cold and hot smoking reduces the total construction costs for an operator producing both types of smoke cured product. The hot smoking process was found to require markedly less firewood than cold smoking, a fact of considerable importance in desert or semi-desert areas with sparse vegetation.

Seasonal changes of heat and moisture fluxes from the Caspian Sea surface and its effect on synoptic systems with heavy rainfalls in southern shores of the sea during 2005-2010

Caspian Sea with its unique characteristics is a significant source to supply required heat and moisture for passing weather systems over the north of Iran. Investigation of heat and moisture fluxes in the region and their effects on these systems that could lead to floods and major financial and human losses is essential in weather forecasting. Nowadays by improvement of numerical weather and climate prediction models and the increasing need to more accurate forecasting of heavy rainfall, the evaluation and verification of these models has been become much more important. In this study we have used the WRF model as a research-practical one with many valuable characteristics and flexibilities. In this research, the effects of heat and moisture fluxes of Caspian Sea on the synoptic and dynamical structure of 20 selective systems associated with heavy rainfall in the southern shores of Caspian Sea are investigated. These systems are selected based on the rainfall data gathered by three local stations named: Rasht, Babolsar and Gorgan in different seasons during a five-year period (2005-2010) with maximum amount of rainfall through the 24 hours of a day. In addition to synoptic analyses of these systems, the WRF model with and without surface flues was run using the two nested grids with the horizontal resolutions of 12 and 36 km. The results show that there are good consistencies between the predicted distribution of rainfall field, time of beginning and end of rainfall by the model and the observations. But the model underestimates the amounts of rainfall and the maximum difference with the observation is about 69%. Also, no significant changes in the results are seen when the domain and the resolution of computations are changed. The other noticeable point is that the systems are severely weakened by removing heat and moisture fluxes and thereby the amounts of large scale rainfall are decreased up to 77% and the convective rainfalls tend to zero.

Heat budget studies of the north Arabian Sea during summer and winter seasons, 1992

In this study heat budget components and momentum flux for August and January 1992 over the north Arabian Sea are computed. The marine meteorological data measured on board during the cruises of PAK-US joint project (NASEER) are used for the computation. Significant differences were found in the heat budget components as well as in the momentum flux during different monsoon periods over the north Arabian Sea. The latent heat flux was always positive and attributed to the large vapour pressure gradient. The computed moisture and latent heat fluxes in January were higher than August The highest value of latent heat flux 309 W/m2 at station 8 was evaluated. These higher latent heat fluxes were due to the large vapour pressure gradient, air-sea temperature difference, the wind speed, and the prevailing wind direction (from north and northeast). Negative values of sensible heat fluxes in both seasons indicate that the heat transfer was from the atmosphere to the ocean. The negative values of net heat gain indicate that the sea surface field became an energy sink: or the sea surface supplied more energy to the atmosphere than it received from it. Large variation in the momentum flux mainly attributed to the variation in the wind speed. Aerial averages of heat and momentum fluxes were also computed.