Plastic litter colonization in a brackish water environment.

Transitional waters, including coastal ponds, represent unique environments. These distinct ecosystems are often among the most severely polluted systems due to intensive human activities. Our study marks the first evaluation of aquatic invertebrates associated with plastic litter in two brackish ponds. We collected 43 items of plastic litter (including bottles and disposable plastics) during the winter and spring of 2022. Most of plastic litter (76.8 %) was colonized by aquatic invertebrates. A total of 495 individuals were observed on the plastic litter, with the number of individuals ranging from 1 to 54 (average = 13.4). The most abundant taxa were from the families Gammaridae, Serpulidae, and Sphaeromatidae. Invertebrates colonized both the external and internal surfaces of the plastic bottles. Plastic bottles trapped 25 % of the total biota. The internal entrapped taxa were mainly represented by gammarids, molluscs egg mass, and sphaeromatids. Open bottles could potentially serve as temporary or permanent traps for invertebrates colonizing their internal surfaces. We argue that the dispersal of species driven by plastics is possible but limited, just as water exchanges with the seas are limited. These brackish lakes could be transit areas, but more importantly, they could be hotspots for plastic litter.

Microplastic ingestion by Atlantic horse mackerel (Trachurus trachurus) in the North and central Moroccan Atlantic coast between Larache (35°30'N) and Boujdour (26°30'N).

Horse mackerel is a semi-pelagic species found in abundance in the Moroccan coasts and occupies the first ranks in the catches landed by the coastal fleet. In this study, we investigated the ingestion of Polyamide, Acrylic and Polystyrene by Atlantic horse mackerel, in the Moroccan Atlantic coastal area located between Larache (35°30'N) and Boujdour (26°30'N). The objective is to map the spatial distribution of horse Mackerel containing microplastics (MPs) in their stomachs and identify hot spot areas. We also aim to verify the most ingested polymer by this fish characterized by significant daily vertical migrations. The results show that the three studied polymers were detected in the stomach contents of more than 73% of studied fishes. The hot spot areas are located more in the northern part where urbanization and fishing activity are important. Polyamide, the densest polymer, is the most abundant (86% of cases), followed by acrylic. These two polymers were found in association in 47% of cases. No correlation between the presence of MPs in the stomach contents and the size of the individual fishes was noted. Interestingly, the group of mature specimens ingested more MPs than the immature group.

Ingestion of microplastics by pelagic fish from the Moroccan Central Atlantic coast.

As in the rest of the world, plastics are the most dominant marine litter category in Moroccan Atlantic waters. This work aims to identify the presence of microplastics in the stomach contents of three small pelagic species of the Central zone of the Atlantic, located between Cape Cantin (33°N) and Cape Boujdor (26°N): Scomber spp., Truchurus truchurus and Sardina pilchardus; Also, to map the spatial distribution of the investigated species. A total of 251 individuals were examined, composed by 118 Scomber spp, 82 Sardina pilchardus and 51 Trachurus trachurus. The characterization of microplastics ingested by those species was identified by FTIR. The results showed the presence of three polymers: Polyamide (PA), Acrylic (PC) and Polystyrene (PS), in 26% of the individuals studied. The presence of polymers was accumulated in Atlantic horse mackerel (Truchurus truchurus) with 30%, then in mackerels (Scomber spp.) with 27%, and European pilchardus (Sardina pilchardus) (9%). Fish containing microplastics in their stomachs are concentrated, mainly in the northern part of the study area. This zone has significant artisanal fishing activity and large rivers that can be source of microplastics.