Diverse Transcriptome Responses to Salinity Change in Atlantic Cod Subpopulations.

Area of Science:

• Fisheries ecology and management
• Environmental adaptation
• Genomics and molecular biology

Background:

• Global climate change is altering marine environments, notably reducing ocean salinity in areas like the Baltic Sea.
• Atlantic cod (Gadus morhua) populations in the Baltic Sea, divided into western and eastern subpopulations, are declining, with salinity identified as a key environmental stressor.
• Understanding cod's adaptive mechanisms to salinity changes is vital for the conservation of this ecologically and economically important species.

Purpose of the Study:

• To investigate the molecular mechanisms underlying differential adaptation to salinity fluctuations in Baltic cod subpopulations.
• To identify specific genes and pathways affected by salinity changes in western and eastern Baltic cod.
• To explore subpopulation-specific responses to environmental variation in Atlantic cod.

Main Methods:

• An oligonucleotide microarray was used to analyze gene expression in gill tissues of Baltic cod.
• An exposure experiment involved manipulating salinity levels (elevation and reduction) to simulate environmental changes.
• Differential gene expression analysis was performed to identify genes responding to salinity stress in a subpopulation-dependent manner.

Main Results:

• Approximately 400 differentially expressed genes (DEGs) were identified between the two Baltic cod subpopulations.
• Affected genes were primarily involved in immune response, metabolism, programmed cell death, cytoskeleton, and extracellular matrix functions.
• A clear subpopulation-dependent pattern in gene expression responses to salinity changes was observed.

Conclusions:

• Baltic cod subpopulations exhibit distinct molecular responses to salinity fluctuations, indicating complex osmoregulation strategies.
• These findings highlight the importance of considering subpopulation-specific adaptations in fisheries management and conservation efforts under climate change.
• The identified DEGs provide insights into the genetic basis of salinity tolerance in Atlantic cod.