. 2022 Mar 7;8(3):e09069. doi: 10.1016/j.heliyon.2022.e09069

Table 2.

Average results (± standard deviation) of biometric measurements; PAS-reaction in the gills; oxidative stress related enzymes' activities (catalase – CAT, glutathione peroxidase – GPx, and glutathione reductase – GR) and metabolic related enzymes’ activities (cholinesterase – ChE, aspartate aminotransferase – ASAT, alanine aminotransferase – ALAT, and lactate dehydrogenase – LDH) in the digestive glands (U/mg protein); and DNA damage (percentage of DNA in the tail of the comet (tail intensity – TI%)) in the hemocytes; and the integrated biomarker response (IBR) values of mussels from different sampling sites in Bulgaria.

	Reference site	Sampling sites
	Reference site	Zhrebchevo	Kardzhali	Studen Kladenets
Biometric indices

CI total	25.57 ± 1.50^a	22.78 ± 2.04^a	25.57 ± 2.10^a	24.29 ± 3.31a
CI 2	62.10 ± 10.99^a	39.49 ± 1.57^a	51.17 ± 8.28^a	51.95 ± 6.84a
CI 3	419.63 ± 24.72^a	330.43 ± 13.15^a	329.13 ± 58.60^a	255.94 ± 38.17b
CI 4	61.97 ± 4.15^a	71.70 ± 0.81^a	66.35 ± 3.73^a	65.94 ± 2.99a
CI 5	0.0030 ± 0.0003^a	0.0027 ± 0.0001^a	0.0025 ± 0.0003^a	0.0024 ± 0.0004a
Histochemical alterations in gills

Intensity of PAS-reaction	++	+	+/-	+/-
Oxidative stress related enzymes in digestive gland

CAT	25.79 ± 2.99^a,c	17.74 ± 2.52^a	34.23 ± 7.59^c	104.75 ± 5.06^b
GPx	0.68 ± 0.19^a	0.74 ± 0.18^a	0.93 ± 0.23^a,b	1.27 ± 0.29^b
GR	0.31 ± 0.11^a	0.49 ± 0.09^a	0.86 ± 0.28^b	1.10 ± 0.25^b
Metabolic related enzymes in digestive gland

ChE	31.82 ± 3.73^a	30.39 ± 2.46^b	5.98 ± 2.76^d	14.52 ± 3.18^c
ASAT	84.35 ± 2.97^a	72.19 ± 3.00^b	24.98 ± 2.54^d	65.18 ± 2.79^c
ALAT	47.07 ± 3.64^a	46.12 ± 2.70^a	34.41 ± 1.72^b	35.32 ± 2.85^b
LDH	147.28 ± 16.22^a	52.28 ± 6.70^b	140.81 ± 8.76^a,c	125.43 ± 9.16^c
DNA damage in haemocytes

Tail inensity, TI%	5.54 ± 0.92^a	13.23 ± 1.31^b	21.84 ± 2.60^c	25.79 ± 1.58^d
Integrated biomarker response (IBR)

IBR	0	0.50	7.51	4.38

^a,b,c The values with different letters in the same row are significantly different (Tukey's test, p < 0.05).

CI total = weight of soft tissue (g)/total weight (g) x 100. CI 2 = weight of soft tissue (g)/shell weight (g) x 100. CI 3 (state index) = weight of soft tissue (g)/shell length (cm) x 100. CI 4 (shell component index) = shell weight (g)/(shell weight (g) + meat weight (g)) x 100. CI 5 (condition factor) = weight of soft tissue (g)/shell lengthˆ3 (mm) x 100.