Warmer temperature increases mercury toxicity in a marine copepod

Area of Science:

• Marine biology
• Environmental toxicology
• Climate change science

Background:

• Marine ecosystems face simultaneous threats from ocean warming and mercury pollution.
• Understanding the molecular mechanisms of these combined stressors is crucial for predicting ecosystem responses.

Purpose of the Study:

• To investigate the effects of elevated temperature and mercury exposure on the marine copepod Pseudodiaptomus annandalei.
• To determine the molecular mechanisms underlying mercury bioaccumulation and toxicity under combined stress conditions.

Main Methods:

• A 24-hour cross-factored experiment exposing P. annandalei to different temperatures (22°C, 25°C) and mercury concentrations (0, 118 μg/L).
• Analysis of mercury accumulation, subcellular fractions, and gene expression (SOD, GPx, mt1, hsp70, hsp90, hk, pk).

Main Results:

• Combined exposure to warming and mercury significantly increased mercury bioaccumulation and storage in metal-sensitive fractions.
• Warming alone induced thermal stress, indicated by increased mt1, hsp70, hsp90, and hk gene expression.
• Mercury exposure alone and combined exposure altered gene expression related to oxidative stress and energy metabolism, with combined exposure showing distinct patterns.

Conclusions:

• Ocean warming exacerbates mercury toxicity in marine copepods.
• This interaction affects molecular pathways, potentially impacting marine ecosystem health.
• Findings enhance projections of marine ecosystem responses to climate change and metal pollution.