Nutrient Loading Fosters Seagrass Productivity Under Ocean Acidification

Area of Science:

• Marine Biology
• Ecology
• Climate Change Science

Background:

• Global climate change causes ocean acidification, a significant stressor for marine ecosystems.
• The interaction between ocean acidification and local stressors like nutrient loading is poorly understood.
• Seagrasses, like Posidonia oceanica, are vital marine foundation species facing multiple environmental challenges.

Purpose of the Study:

• To investigate how nutrient enrichment modifies the effects of ocean acidification on Posidonia oceanica and its epiphyte community.
• To assess the combined impacts of low pH and varied nutrient levels on seagrass physiology and gene expression.
• To understand the role of local environmental factors in mediating the response of marine ecosystems to global stressors.

Main Methods:

• Utilized natural CO2 vents to simulate low pH conditions.
• Exposed Posidonia oceanica to three nutrient levels at both ambient and low pH sites for 16 months.
• Assessed plant response through gene expression analysis, growth measurements, photosynthetic pigment quantification, and epiphyte loading.

Main Results:

• Nutrient addition at low pH enhanced Posidonia oceanica growth and photosynthetic pigment synthesis.
• Overexpression of nitrogen transporter genes indicated increased nutrient uptake by seagrass under low pH and high nutrients.
• Elevated nutrient levels reduced antioxidant gene expression in low pH conditions and increased epiphyte cover across pH levels.

Conclusions:

• The impact of ocean acidification on Posidonia oceanica is significantly influenced by local nutrient availability.
• Combined stressors can lead to complex responses in seagrasses, affecting both the plant and its associated community.
• Understanding localized environmental contexts is critical for predicting the effects of global climate change on marine systems.