Oysters are experiencing numerous environmental shifts as the threat of climate change intensifies. Rapid adaptive response is required for these organisms to survive and manage these environmental stressors. It is becoming increasingly critical to understand not only the immediate response to stress, but how the previous environment may influence this response. This concept is known as within-generation carryover effects. However, the mechanisms behind carryover effects remain largely unexplored. Here, we look at DNA methylation as a response to environmental stress. This epigenetic mark can be more sensitive to environmental change than broader phenotypic measures. Additionally, DNA methylation is believed to facilitate adaptive responses in invertebrates.
In a fully factorial experiment, we exposed juvenile oysters to two phases of water treatments (two treatment options; no stress and diel-cycling hypoxic water, <2 mg/L) to simulate climate change predictions. After the second exposure to environmental stress, whole body tissue samples were collected and processed for MethylRAD-sequencing. Our findings reveal context-dependent methylation patterns (Fig. 1), meaning methylation is not a uniform response, but specific to the environment experienced. Additionally, we found that the timing of environmental stress influences the oyster methylome. These results suggest that the methylated response is influenced by previous exposure and emphasizes the importance of studying multiple stress events. Enhancing our understanding of these processes can provide insights to efficient and effective management practices to ensure the persistence of oyster populations in a changing climate.