Table 2. Definition, justification, interpretation of used biomarkers with zooplankton examples from literature.

AO = antioxidant, OD = oxidative damage, O₂^- = superoxide radical, H₂O₂ = hydrogen peroxide.

	Biomarker	Definition	Justification	Interpretation ↑ or ↓	Example of species and study area	Reference
GSH: GSSG	Reduced: oxidised glutathione ratio	OD	Assays glutathione redox state [29]	Low ratio or increase in GGSG indicate stress	Limnocalanus macrurus, Baltic Sea, FI	[16]
GR	Glutathione reductase	AO	Reduces GSSG back to GSH [30]	↑ indicates more AO	L. macrurus, Baltic Sea, FI	[16]
GST	Glutathione S-transferase	AO	Catalyzes reactions that detoxify harmful compounds [31]	↑ indicates more AO	L. macrurus, Baltic Sea, FI; Eurytemora affinis, Seine estuary, FR	[16, 27]
SOD	Superoxide dismutase	AO	Part of enzymatic defense to remove O2- [31]	↑ indicates more AO	L. macrurus, Baltic Sea, FI	[16]
CAT	Catalase	AO	Part of enzymatic defense to remove H2O2 [31]	↑ indicates more AO	Boeckella gibbosa, Mixodiaptomus laciniatus, Lake Los Cantaros, ARG; Lake La Caldera, ESP	[32]
ORAC	Oxygen reactive absorbance capacity	AO	Assesses antioxidant capacity [33]	↑ indicates more AO	Acartia bifilosa, Baltic Sea, FI	[21]
LPX	Lipid peroxidation	OD	Oxidative degradation of lipids in cell membrane, resulting in cell damage [33]	↑ indicates stress	L. macrurus, Baltic Sea, FI	[16]