Potential impact of rising seawater temperature on copepods due to coastal power plants in subtropical areas

The major objective of this study is to understand the upper thermal limits and potential impact of temperature elevation on copepods caused by coastal power plants. Laboratory experiments were designed to evaluate the upper incipient lethal temperature (UILT) and critical thermal maximum (CTMax) of eight coastal copepod species collected from a subtropical bay in spring and summer. The 48h-UILT of copepods acclimatized at 16.0, 20.0, 28.0 °C were 26.4-29.1, 27.3-30.1, 32.9-36.9 °C, respectively. And the CTMax of copepods acclimatized at 28.0 °C was 35.80-41.03 °C. The UILT of copepods increased significantly with rising acclimatization temperatures, but the difference values between UILT and acclimatization temperatures decreased, which indicated that the seawater temperature elevation induced the growing mortalities of copepods with increasing natural seawater temperatures from the thermal addition of power plants. The results also showed that estuarine copepods had more tolerances to the thermal stress than those from other more stable marine environments. As to the calanoid copepod species, there was a significant negative correlation between the CTMax and body length (p < 0.01). So it seemed that the copepod species with large body size were more sensitive to the thermal addition than the smaller ones. Thus, owing to the temperature increase, the copepod species diversity might reduce and the composition of copepod communities might tend to be small-sized in natural sea areas close to the coastal power plants.     

The activity of antioxidative enzymes in three strawberry cultivars related to salt-stress tolerance

Effects of salt stress on the time course of stomatal behaviors and the activity of antioxidative enzymes such as catalase (CAT) (EC 1.11.1.6), ascorbate peroxidase (APX) (EC 1.11.1.11), and glutathione reductase (GR) (EC. 1.6.4.2) were studied in three strawberry cultivars. The responses of the cultivars ‘Camarosa’, ‘Tioga,’ and ‘Chandler’ were compared when they were irrigated with nutrient solution containing 0, 8.5, 17.0, and 34.0 mM sodium chloride (NaCl) for 30 days. A significant reduction in stomatal conductance (g_s) was seen particularly on the 30th day of the salt treatments only in Camarosa, which is parallel to transpiration rate (E). CAT activities decreased in all of the salt treatments only in Tioga, while it remained almost unchanged or slightly increased depending on the period in Camarosa and Chandler. APX activity sharply increased in 17.0 and 8.5-mM NaCl treatments for 30 days in Camarosa and Tioga, respectively, whereas it linearly increased based on the NaCl treatments in Chandler. On the other hand, only Camarosa demonstrated a sharp increase in GR activity induced by salinity applied for 30 days. All the data indicated that control of the stomatal behavior, the higher salt-stress tolerance (LT₅₀) and higher constitutive activity of antioxidant enzymes made Camarosa and Tioga relatively salt-tolerant cultivars.     

A comparison of low temperature tolerance traits between closely related aphids from the tropics, temperate zone, and Arctic

The survival of aphids exposed to low temperatures is strongly influenced by their ability to move within and between plants and to survive exposure to potentially lethal low temperatures. Little is known about the physiological and behavioural limitations on aphid movement at low temperatures or how they may relate to lethal temperature thresholds. These questions are addressed here through an analysis of the thermal ecology of three closely related aphid species: Myzus persicae, a ubiquitous temperate zone pest, Myzus polaris, an arctic species, and Myzus ornatus, a sub-tropical species. Lower lethal temperatures (LLT₅₀) of aphids reared at 15 °C were similar for M. persicae and M. polaris (range: −12.7 to −13.9 °C), but significantly higher for M. ornatus (−6.6 °C). The temperature thresholds for activity and chill coma increased with rearing temperature (10, 15, 20, and 25 °C) for all clones. For M. polaris and M. ornatus the slopes of these relationships were approximately parallel; by contrast, for M. persicae the difference in slopes meant that the difference between the temperatures at which aphids cease walking and enter coma increased by approximately 0.5 °C per 1 °C increase in rearing temperature. The data suggest that all three species have the potential to increase population sizes and expand their ranges if low temperature limitation is relaxed.