جستجوی مقالات مرتبط با کلیدواژه « global warming » در نشریات گروه « زیست شناسی »

The phenomenon of climate change due to the expansion of human industrial activities is rapidly advancing, and via disrupting ecological processes and destroying the habitats, has caused extinction of many fishes and reducing the biodiversity of aquatic ecosystems. This study predicts the distribution of Ponticola gorlap under two climate scenarios (RCP 2.6 and RCP 8.5) for the years 2050 and 2080 using the MaxEnt model. Five climatic and environmental variables, including annual mean temperature, annual precipitation, annual temperature range, flow accumulation, and slope, were utilized for forecasting. The model demonstrated excellent performance (AUC criterion: 0.969) in predicting species distribution. Annual temperature range identified as the most influential variable (importance score: 57/5) in determining the species' distribution. Moreover, the study forecasts a significant decrease in the distribution of P. gorlap under both optimistic and pessimistic scenarios for the years 2050 and 2080. As climate change intensifies and suitable habitat ranges diminish, the species faces an elevated risk of extinction in the future. Hence, experts and policy-makers should focus more on conservation measures.

Understanding the relationship between climate-based habitat conditions and survival is key to maintaining biodiversity in the face of rapid climate change. Water is a limiting habitat variable for amphibians because larvae must metamorphose before wetlands or ponds dry up. Changes in precipitation and temperature patterns globally affect the amount of water available, but the impact of these changes on amphibian growth, development, and survival is poorly understood. In this study, the effect of water level reduction on the growth, metamorphosis, and survival of Levant green frog (Pelophylax bedriagae) larvae in three treatments (control, moderate, and rapid water level reduction) was investigated for 129 days. In each tank, 50 larvae were subjected to the same diet with 4 replications. The results of the experiment showed that reducing the water level increases the growth rate. Treatments with moderate and rapid water reduction showed a decrease in the size of metamorphosis, a decrease in the duration of metamorphosis, and a decrease in survival compared to the control treatment. The statistical results showed that the effect of these treatments on metamorphosis time and metamorphosis size is significant but insignificant on growth rate and survival. This information can provide insight into the plasticity of this species under climate change.

Since the Persian Gulf is a semi-closed water ecosystem, climate change has more severe impacts on organisms, especially on non-motile ones. The harmful effects on organisms can be studied at all biological levels of morphology, anatomy, physiology, to cellular and molecular levels. The collapse of the symbiotic relationship between coral and its symbiont algae can result in bleaching and it is the first effect of changing favorable conditions on hard coral. The cells produce Heat Shock Proteins (hereinafter referred to as HSP) in response to heat stress. The rate and way of HSP production in corals depend on the expression of the genes encoding these proteins. In this study, we investigated the expression of heat shock gene HSP70 in response to elevated temperature in Acropora downingi (Wallace, 1999) coral reef. After sampling hard corals in March 2018 and adapting them to laboratory conditions, their ambient water temperature increased to 9 °C (from 25 °C to 34 °C). The samples were adapted to laboratory conditions for 2 weeks after being transferred to the laboratory. The water temperature was 25 °C under control conditions, which was increased to 34 °C to create thermal stress. The expression of the gene Hsp70 was evaluated at control time and also 24 h and 48 h after temperature rise. The study showed that gene expression was significantly increased 24 h after stress and it decreased at 48. However, the corals were bleached, which could be due to the deterioration and reduced resistance to heat shock.

Accumulated Gas Hydrates in seafloor sediments can be released in the atmosphere and the greenhouse effect of methane can exacerbate global warming. It is possible to estimate the stability of methane hydrate in the different physicochemical conditions by using physicochemical equations. In this study, by using a physicochemical equation and data of 641 points, stability of methane hydrate in different depth and locations of the Caspian Sea were calculated and potential maps of gas hydrate formation were presented. In the next stage, methane hydrate stability was measured in the different conditions in that the mean temperature of the Caspian Sea is increased 0.6 to 2 oC by global warming and then the thickness changing of the methane hydrate zones was calculated. Then, based on the calculated thickness variations and geophysical evidences of gas hydrate in the Caspian Sea, released gas in the atmosphere for different scenarios were estimated. Result showed that a huge amount of methane gas, maybe around 369×1012 to 984×1012 m3, can be released in the atmosphere.