Microplastics alter digestive enzyme activities in the marine bivalve, Mytilus galloprovincialis

Area of Science:

• Marine Biology
• Environmental Toxicology
• Biochemistry

Background:

• Microplastics are pervasive environmental contaminants.
• Filter-feeding invertebrates like mussels ingest microplastics.
• Ingested microplastics can persist in digestive tracts, interacting with enzymes.

Purpose of the Study:

• To investigate the effects of microplastic polymer type, size, and concentration on key digestive enzymes in the marine mussel Mytilus galloprovincialis.
• To determine which digestive enzymes are affected by microplastic ingestion.

Main Methods:

• Mussels were exposed to spherical microplastics of varying polymer types, sizes, and concentrations.
• The activities of seven key digestive enzymes (amylase, xylanase, cellulase, laminarinase, lipases, lipolytic esterases, and proteases) in the digestive gland were measured.
• Enzyme activity was quantified spectrophotometrically.

Main Results:

• Polymer type significantly influenced carbohydrase activity: polystyrene reduced amylase and xylanase but increased cellulase.
• High microplastic concentrations (5 × 10^4 particles L⁻¹) led to a 2.5-fold increase in total protease activity.
• Laminarinase, lipases, and lipolytic esterases activities remained unaffected by microplastic exposure.

Conclusions:

• Microplastic ingestion alters digestive enzyme function in Mytilus galloprovincialis.
• Changes in enzyme activity, particularly protease and carbohydrase, can impair energy acquisition from food.
• These alterations may lead to reduced energy reserves in mussels, impacting their overall health and survival.