Marine turtles as bio-indicators of plastic pollution in the eastern Mediterranean.

The loggerhead turtle (Caretta caretta) has been suggested as a bio-indicator species for plastic pollution. However, detailed investigations in the eastern Mediterranean are limited. Here, we present data from loggerhead turtles (2012-2022; n = 131) of which 42.7 % (n = 57) had ingested macroplastic (pieces ≥ 5 mm). Frequency of occurrence (%) was not found to have changed over time, with body size (CCL cm), between stranded or bycaught turtles, or with levels of digesta present. The characteristics of ingested plastic (n = 492) were largely sheetlike (62 %), clear (41 %) or white (25 %) and the most common polymers identified were Polypropylene (37 %) and Polyethylene (35 %). Strong selectivity was displayed towards certain types, colours and shapes. Data are also presented for posthatchling turtles (n = 4), an understudied life stage. Much larger sample sizes will be needed for this species to be an effective bio-indicator, with the consideration of monitoring green turtles (Chelonia mydas) for the eastern Mediterranean recommended allowing a more holistic picture to be gathered.

Determination of tetrodotoxin (TTX) levels in various tissues of the silver cheeked puffer fish (Lagocephalus sceleratus (Gmelin, 1789)) in Northern Cyprus Sea (Eastern Mediterranean).

Lagocephalus sceleratus from the family Tetraodontidae, which is originated from the Red Sea, started to migrate to Mediterranean waters after the opening of the Suez Channel in 1869. Since they do not have any predators in the Mediterranean Sea, their population increased in number very fast. Different tissues of L. sceleratus have tetrodotoxin (TTX). TTX is a non-protein, heat resistant molecule which binds to voltage-gated sodium channels of musculatory and nervous system. Ingestion of the fish can cause a wide variety of effects from mild toxications to death. This study is the first toxicity report of L. sceleratus for Cyprus. Due to the lack of data on toxicity levels of L. sceleratus, and some cases of poising after the ingestion of the fish were the reasons for the start of this work. 24 L. sceleratus were sampled from 3 different areas to represent Northern Cyprus, during one year period. 16 fish samples selected and grouped into 4 fishes per season for toxicity assay. TTX levels from liver, gonad, intestine, muscle and skin tissue homogenate were analyzed with TTX ELISA. Totally 80 tissues were analyzed, 40% of them were above the toxic limit (2.2 µg/g). Most toxic tissue, according to the seasonal average, was found in the summer season and was determined as; Liver = 13.48 µg/g. Most toxic three fishes were found to be female with a length of 45-60 cm. TTX distribution among tissues have similarities with previously published studies from different regions.