Interactions of temperature, salinity and diesel oil on antioxidant defense enzymes of the limpet Nacella concinna

The influence of ocean acidification and warming on responses of Scylla serrata to oil pollution: An integrated biomarker approach

Anthropogenic activities primarily combustion of fossil fuel is the prime cause behind the increased concentration of CO₂ into the atmosphere. As a consequence, marine environments are anticipated to experience shift towards lower pH and elevated temperatures. Moreover, since the industrial revolution the growing demand for petroleum-based products has been mounting up worldwide leading to severe oil pollution. Sundarbans estuarine system (SES) is experiencing ocean warming, acidification as well as oil pollution from the last couple of decades. Scylla serrata is one of the most commercially significant species for aquaculture in coastal areas of Sundarbans. Thus, the prime objective of this study is to delineate whether exposure under ocean warming and acidification exacerbates effect of oil spill on oxidative stress of an estuarine crab S. serrata. Animals were separately exposed under current and projected climate change scenario for 30 days. After this half animals of each treatment were exposed to oil spill conditions for 24 h. Oxidative stress status superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), lipid peroxidation (LPO level) and DNA damage (Comet assay) were measured. Augmented antioxidant and detoxification enzyme activity was noted except for SOD but failed to counteract LPO and DNA damage. The present results clearly highlighted the detrimental combined effect of OWA and pollution on oxidative stress status of crabs that might potentially reduce its population and affect the coastal aquaculture in impending years.

Effect of temperature changes on antioxidant enzymes and oxidative stress in gastropod Nerita oryzarum collected along India's first Tarapur Atomic Power Plant site

Temperature can be considered as pro-oxidant factor that favor the generation of ROS on the species with lower antioxidant efficiency may leads to affect the level of tolerance. So the basic antioxidant enzyme activity (LPO, CAT, SOD, GPx and GST) of gastropod Nerita oryzarum was evaluated at six stations which located between the thermal effluent discharges points from Tarapur Atomic Power Station, India. The antioxidant enzyme activity was shown that all enzyme at discharge point (SII station) where the maximum temperature of heated effluent released. The average maximum values of enzyme activity recorded for LPO, CAT, SOD, GPx and GST were 1.88 ± 0.12, 1.52 ± 0.14, 22.57 ± 0.89, 1.98 ± 0.2 and 17.22 ± 0.63 respectively. The results were inferred the level water temperature directly proportional to the oxidative stress by ROS generation in Nerita oryzarum. Similar results were observed at laboratory experiment under the condition i.e., Treatment 1 (30⁰C), Treatment 2 (35⁰C), Treatment 3 (40⁰C) and Control (25⁰C). The present prima facie work clearly indicated the physiological response of N. oryzarum with respect to antioxidant enzyme activity against the heated effluent released, which will be useful as baseline information for future research work.

Occurrence and distribution of legacy and emerging pollutants including plastic debris in Antarctica: Sources, distribution and impact on marine biodiversity

Since the first explorers reached Antarctica, their activities have quickly impacted both land and sea and thus, together with the long-range transport, hazardous chemicals began to accumulate. It is commonly recognized that anthropogenic pollution in Antarctica can originate from either global or local sources. Heavy metals, organohalogenated compounds, hydrocarbons, and (more recently) plastic, have been found in Antarctic biota, soil sediments, seawater, air, snow and sea-ice. Studies in such remote areas are challenging and expensive, and the complexity of potential interactions occurring in such extreme climate conditions (i.e., low temperature) makes any accurate prediction on potential impacts difficult. The present review aims to summarize the current state of knowledge on occurrence and distribution of legacy and emerging pollutants in Antarctica, such as plastic, from either global or local sources. Future actions to monitor and mitigate any potential impact on Antarctic biodiversity are discussed.

An Integrated and Multibiomarker approach to delineate oxidative stress status of Bellamya bengalensis under the interactions of elevated temperature and chlorpyrifos contamination

Synergistic effects of warming on bioconcentration and receptiveness of pollutants are still poorly unravelled in conjunction with cellular and molecular responses. The present study addressed the impact of an environmental relevant dose of chlorpyrifos (organophosphate pesticide), under control (25 °C) and elevated levels of temperature (30 °C, 35 °C) in Bellamya bengalensis, a freshwater gastropod for 60 days across various endpoints. Multiple levels of biomarkers were measured: growth conditions (organ to flesh weight ratio, condition index), oxidative stress status (SOD, CAT, GST, LPO) and DNA damage (Comet assay-3^rd, 30^th and 60^th days only) after acute (24, 48 and 72 h) and long-term exposures (10^th, 20^th, 30^th, 40^th, 50^th and 60^th days). An integrated biomarker response (IBR) strategy was adapted to amalgamate results generated from various biomarkers to assess organism's vulnerability to pesticide pollution and how it may shift with warming climate. Significant changes were observed in growth conditions under longer exposure periods. Acute as well as long-term exposures enhanced the antioxidant and detoxification enzyme activity. DNA damage was extensive under longer exposure to stress howbeit was also significantly escalated under acute severe warming. Antioxidant and detoxification mechanisms fell short in counteracting cellular level damage. The IBR results indicated long-term acclimation of B. bengalensis to elevated temperatures and pesticide contamination lead to an improved tolerance level howbeit, acute stress was more detrimental. This study provided evidence for the efficiency of employing an integrated biomarker approach for B. bengalensis in future bio-monitoring studies.

Acute exposure to water-soluble fractions of marine diesel oil: Evaluation of apoptosis and oxidative stress in an ascidian

To understand the mechanisms involved in organisms' responses to toxicity from oil pollution, we studied the effect of acute exposure (24 h) to the marine water-soluble fraction of diesel oil (WFDO) on the ascidian Styela plicata. We evaluated the mortality and behavior by means of the siphon reflex, and the response of blood cells (hemocytes) contained in the pharynx, by means of the production of nitric oxide (NO) and reactive oxygen species (ROS), in addition to the activity of the antioxidant enzyme catalase (CAT). We also correlated oxidative stress with the activation of apoptotic pathways. No mortality occurred 24 h after the ascidians were exposed to 5% and 10% marine WFDO; however, the siphon reflex, a behavioral test based on the time that the animals took to close their siphons, increased. We also observed an inflammatory response, as estimated by the increase in the number of hemocytes in the pharynx. NO and ROS production and CAT activity were reduced, whereas caspase-3, a signaling molecule involved in apoptosis, was activated. This suggests that in ascidians acutely exposed to oil, another mechanism can occur in addition to oxidative stress. Another possibility is that WFDO may directly interact with cellular macromolecules and activate caspase-3, independently of generating oxidative stress. The results showed that components of diesel oil affected a marine organism, which showed reduced ROS production in the pharynx cells, including hemocytes, and activation of apoptotic pathways.

Bacterial communities and chemical parameters in soils and coastal sediments in response to diesel spills at Carlini Station, Antarctica

A diesel spill occurring at Carlini Station (King George Island (Isla 25 de Mayo), South Shetland Islands) in 2009 started the study of the fate of the hydrocarbons and their effect on the bacterial communities of the Potter Cove ecosystem. Soils and sediments were sampled across the 200-meter long diesel plume towards Potter Cove four and 15months after the spill. The sampling revealed a second fuel leakage from an underground pipeline at the spill site. The hydrocarbon fraction spilt over frozen and snow-covered ground reached the sea and dispersed with the currents. Contrary, diesel that infiltrated unfrozen soil remained detectable for years, and was seeping with ground water towards coastal marine sediments. Structural changes of the bacterial communities as well as hydrocarbon, carbon and nitrogen contents were investigated in sediments in front of the station, two affected terrestrial sites, and a terrestrial non-contaminated reference site. Bacterial communities (16S rRNA gene clone libraries) changed over time in contaminated soils and sediments. At the underground seepage site of highest contamination (5812 to 366μgg^-1_dw hydrocarbons from surface to 90-cm depth), communities were dominated by Actinobacteria (18%) and a betaproteobacterium closely related to Polaromonas naphthalenivorans (40%). At one of the spill sites, affected exclusively at the surface, contamination disappeared within one year. The same bacterial groups were enriched at both contaminated sites. This response at community level suggests that the cold-adapted indigenous microbiota in soils of the West Antarctic Peninsula have a high potential for bioremediation and can support soil cleaning actions in the ecosystem. Intensive monitoring of pollution and site assessment after episodic fuel spills is required for decision-making towards remediation strategies.

The role of stochastic thermal environments in modulating the thermal physiology of an intertidal limpet, Lottia digitalis

Much of our understanding of the thermal physiology of intertidal organisms comes from experiments with animals acclimated under constant conditions and exposed to a single heat stress. In nature, however, the thermal environment is more complex. Aerial exposure and the unpredictable nature of thermal stress during low tides may be critical factors in defining the thermal physiology of intertidal organisms. In the fingered limpet, Lottia digitalis, we investigated whether upper temperature tolerance and thermal sensitivity were influenced by the pattern of fluctuation with which thermal stress was applied. Specifically, we examined whether there was a differential response (measured as cardiac performance) to repeated heat stress of a constant and predictable magnitude compared with heat stress applied in a stochastic and unpredictable nature. We also investigated differences in cellular metabolism and damage following immersion for insights into biochemical mechanisms of tolerance. Upper temperature tolerance increased with aerial exposure, but no significant differences were found between predictable treatments of varying magnitudes (13°C versus 24°C versus 32°C). Significant differences in thermal tolerance were found between unpredictable trials with different heating patterns. There were no significant differences among treatments in basal citrate synthase activity, glycogen content, oxidative stress or antioxidants. Our results suggest that aerial exposure and recent thermal history, paired with relief from high low-tide temperatures, are important factors modulating the capacity of limpets to deal with thermal stress.