Microplastic ingestion in key fish species of food webs in the Southwest Atlantic (Marine Protected Area Namuncurá / Burdwood Bank).

Microplastics (MPs) are currently one of the main problems of marine pollution, being found in all environmental matrices. Due to their size, they can be ingested by organisms directly (from the environment) or indirectly (with their prey). The objective of this study was to analyze the occurrence, abundance, concentration, and chemical nature of MPs present in the gastrointestinal tract of two fish species, Patagonotothen guntheri and Patagonotothen ramsayi, both of which are key in the food web of the Marine Protected Area Namuncurá/ Banco Burdwood (MPA N/BB). The analyzed species presented high values of MPs per individual (MPs/ind.) and occurrence compared to other studies. P. guntheri tended to have a lower number of MPs/ind. and occurrence than P. ramsayi (P. guntheri: 2.50 ± 1.93 MPs/ind., 82.50  %; P. ramsayi: 3.93 ± 2.91 MPs/ind., 90.60  %). While fibers were the predominant MPs in both species, P. ramsayi had a greater number of fragments and a greater variety of MPs chemical composition than P. guntheri. The prevailing chemical composition was cellulosic material (cellulose and cellulose mixed with polyamide and polyester). Synthetic fibers and fragments such as polyester (PET), alkyd resin, polyurethane, polyethylene, polyacrylic fiber and poly(ethylene-co-vinyl acetate-co-vinyl chloride) were also found. Although both species have a generalist diet, the differences found may be due to the fact that P. guntheri has benthopelagic feeding habits while P. ramsayi has demersal-benthic. Our study is the first report on the presence and characterization of MPs in organisms relevant to food webs in the Southwest Atlantic.

Brooding in the Southern Ocean: The Case of the Pterasterid Sea Star Diplopteraster verrucosus (Sladen, 1882).

Diplopteraster verrucosus is a sea star that incubates its offspring in nidamental chambers. The offspring rely exclusively on maternally provided nutrition. The retention of the embryonic stages allows the allocation of nutritional supplies from the female to the brooded juveniles during the brooding period. The main objectives of this study are, first, to quantify the reproductive investment of D. verrucosus and, second, to describe the morphology, energetics, and oxidative metabolism throughout early ontogenetic stages. A skewed sex ratio of 2:1 females:males was found, and 17 of 39 females were brooding. Both brooding and non-brooding females showed higher energy density and total antioxidant capacity in their gonads than males. We identified three cohorts of offspring being retained within the female body simultaneously. Energy density and reactive oxygen species increased significantly with the offspring's volume throughout ontogeny. Moreover, we found evidence of at least two key events during ontogeny. First, the depletion of antioxidants, the increase of reactive oxygen species, and the development of a complete digestive system appear to trigger feeding on the mothers's pyloric caeca. Second, another oxidative imbalance appears to be associated with the release of the brooded juveniles to the environment. Therefore, oxidative balance and energetic variances may be associated with development of autonomous feeding and juvenile release in D. verrucosus.