RESUMO
This review examined one of the effects of climate change that has only recently received attention, i.e., climate change impacts on the distribution and toxicity of chemical contaminants in the environment. As ecosystem engineers, earthworms are potentially threatened by the increasing use of pesticides. Increases in temperature, precipitation regime changes, and related extreme climate events can potentially affect pesticide toxicity. This review of original research articles, reviews, and governmental and intergovernmental reports focused on the interactions between toxicants and environmental parameters. The latter included temperature, moisture, acidification, hypoxia, soil carbon cycle, and soil dynamics, as altered by climate change. Dynamic interactions between climate change and contaminants can be particularly problematic for organisms since organisms have an upper and lower physiological range, resulting in impacts on their acclimatization capacity. Climate change variables such as temperature and soil moisture also have an impact on acidification. An increase in temperature will impact precipitation which might impact soil pH. Also, an increase in precipitation can result in flooding which can reduce the population of earthworms by not giving juvenile earthworms enough time to develop into reproductive adults. As an independent stressor, hypoxia can affect soil organisms, alter bioavailability, and increase the toxicity of chemicals in some cases. Climate change variables, especially temperature and soil moisture, significantly affect the bioavailability of pesticides in the soil and the growth and reproduction of earthworm species.
RESUMO
The hepatotoxic effects of sub-lethal concentrations of atrazine (2.5, 25, 250, and 500 µg L-1) on Clarias gariepinus juveniles were assessed for 28 days in a quality-controlled laboratory procedure. The study was designed to determine the effects of atrazine on selected liver function biomarkers: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin (ALB) and total protein (TP), and to analyze the liver tissues of the fish using a quantitative and qualitative histology-based health assessment protocol. The levels of ALB and TP in exposed specimens were observed to decrease with increasing concentrations of atrazine. However, the activities of ALT, AST, and ALP showed significant (p < 0.05) increase with increasing concentrations of atrazine. Hepatic assessment of the liver tissues revealed marked histopathological alterations, including structural changes (necrotic/apoptotic liver tissue, poor hepatic cord structure, and loss of normal architecture) in 52.2% of the liver tissues in the treatment groups; plasma alterations (vacuolation or fat inclusions, 22.9%) of hepatocytes; hypertrophied hepatocyte (55.2%); nuclear alterations (52.1%); focal necrosis (16.7%); complete degeneration of hepatocytes (60.45%); sinusoids congested with red blood cells or vascular congestion (70.8%); and karyolysis of the nucleus (18.8%). Findings from this study suggest that atrazine interferes with liver function markers and disrupts the normal architectural and structural components of the liver resulting in noninfectious liver injury. This condition resulted in repeated cycles, cell deaths, and inflammation, which could result in the eventual death of the exposed fish if exposure duration was prolonged.
