Biological Monitoring of Gamasiab River using Biomarkers of Acetylcholinesterase Enzyme and Metallothionein Protein in two Species of Onchorhynchus mykiss and Cyprinus carpio

Abstract

Introduction: Metallothionein protein and acetylcholinesterase enzyme are among the most
important biomarkers in evaluating the health of aquatic ecosystems and have been introduced
as one of the defense mechanisms of aquatic organisms in the face of various pollutants.
Therefore, the aim of this study was to evaluate and biologically monitor the organic and
mineral pollution of Gamasyab River using the biomarkers of acetylcholinesterase enzyme and
metallothionein protein in two species of rainbow (Onchorhynchus mykiss) and common carp
(Cyprinus carpio).
Materials & methods: Sampling was done from five rainbow trout farms and eight common
carp farms along the Gamasiab River, and the samples were quickly frozen in liquid nitrogen
and transported to the laboratory. The amount of metallothionein (MT) was measured based
on spectrophotometric method and the analysis of cholinesterase enzyme (AchE) in fish brain
was performed based on Elman's method.
Results: The findings showed that there was a statistically significant difference between
different sampling locations in terms of the average values and effects of AchE and MT in two
fish species (P<0.05). In addition, the average values of total AchE and MT in carp fish are
equal to 3.42 μm/min/g and 707.75 μg/g, respectively, and in rainbow trout it is equal to 1.33
μm/min/g and μg, respectively. /g was 3105.7 and the comparison of the average amount of
AchE and MT between two species of carp and rainbow trout showed that the amount of MT
in rainbow salmon is higher than that of carp, And the amount of AchE activity in carp was
higher than that of rainbow trout.
Conclusion: The differences in the level of MT and AchE biomarkers can be caused by
exposure of fish species exposed to different levels of pollutants due to differences in their
feeding habits and behavior as well as differences in sampling points with environmental
conditions and the entry of polluting sources are different. In this study, the application of 2
specific biomarkers to investigate the presence and effects of two groups of organic and
inorganic pollutants in the Gamasiab River were determined without conducting any type of
chemical analysis. In other words, Gamasiab River is directly exposed to the simultaneous
entry of organic and mineral pollutants due to the extent and dispersion of different human
uses on its margins, which can be detected by tracking specific biomarkers in indicator species
(including rainbow trout and carp) to be a basis for monitoring the pollution of ecosystems.