Microplastic (MP) pollution of the marine environment is now a growing global concern posing a threat to a
variety of species through the ingestion and transfer within food webs. This is considered a potential toxicological
threat to marine species due to the chemical additives used to make many plastic products, or the
persistent organic pollutants that may accumulate on them while residing in the environment. While the presence
of MPs in the marine environment is widely documented, there are no other review articles providing a
summary of published effect studies of MPs on the immune and reproductive systems of marine species. This
manuscript reviews reproductive and immune-system changes in response to MPs in 7 and 9 species, respectively.
Some species such as Mytilus galloprovincialis and oyster Crassostrea gigas were investigated in multiple
papers. Most studies have been conducted on invertebrates, and only 3 studies have been performed on vertebrates,
with exposure times ranging between 30 min and 60 days. A review of the literature revealed that the
most common MPs types studied in relation to adverse impacts on immune system and reproductive success in
marine species were polystyrene (PS) and polyethylene (PE). The immune system’s responses to MPs exposure
varied depending on the species, with altered organismal defense mechanisms and neutrophil function observed
in fish and changes in lysosomal membrane stability and apoptotic-like nuclear alterations in phagocytes reported
in invertebrate species. Reproductive responses to MPs exposure, varied depending on species, but
included significant reduction in gamete and oocyte quality, fecundity, sperm swimming speed, and quality of
offspring. The lack of published data means that developing a clear understanding of the impact across taxonomic
groups with different feeding and behavioral traits is often difficult. Further work is required to better
understand the risk MPs pose to the immune and reproductive syst