Biomarkers as Indicators of Environmental Stress in Animals

Abstract

Environmental stress arising from climate change, habitat loss, pollution, infectious agents, and human activities represents a growing threat to animal health in both terrestrial and aquatic ecosystems. Factors such as temperature fluctuations, ocean acidification, heavy metals, pesticides, and emerging pathogens can disturb physiological balance, weaken immune responses, and negatively affect growth and reproduction. Conventional health assessment methods often identify problems only after visible symptoms develop, highlighting the importance of early and sensitive detection tools. In this context, biomarkers serve as reliable early indicators by revealing subtle biological changes at molecular, cellular, biochemical, and physiological levels before clinical damage becomes apparent. This review compiles and evaluates major categories of biomarkers used in environmental health studies. Among these are signs of oxidative stress (like lipid peroxidation and antioxidant enzyme activity), stress and endocrine hormones, immune-related parameters, genotoxicity markers (including DNA damage assays), metabolic enzymes, and behavioral responses. Their relevance across diverse animal groups, including wildlife, livestock, and aquatic sentinel species, is discussed along with their advantages and limitations in ecological risk assessment. Furthermore, the review explores recent advances such as omics-based technologies, non-invasive sampling strategies, and integrated multi-biomarker approaches, which offer promising tools for improving environmental monitoring, conservation planning, and predictive assessments of animal health under changing environmental conditions.