Variability in microplastic color preference and intake among selected marine and freshwater fish and crustaceans

YOSHIFUMI HORIE; KENSUKE MITSUNAGA; SOICHI HIROKAWA; KAZUYO YAMAJI; UACIQUETE DORCAS LINDA ERNESTO; JUAN MANUEL RÍOS; CHEE KONG YAP; HIDEO OKAMURA

Discover Oceans

Springer

Lugar: Switzerland; Año: 2024

The microplastic ingestion test, previously described by Okamoto et al. [16], involved a microplastic exposure con-centration of 17.5 mg/L for each color (total concentration, 87.5 mg/L), determined based on maximum microplastic ingestion observed in a previous study [16]. Typically, seven aquatic organisms (discrepancies described below) were placed in each 5 L glass tank (width, 20 cm; depth, 20 cm; height, 20 cm), containing 4 L of freshwater or artificial marine water, 24 h before microplastic exposure. Test conditions were as follows: 25℃ ± 2℃, light photoperiod, and (for marine fish) salinity at 33 ± 1 PSU. Artificial marine water was produced using Marine ART Hi (Osaka Yakken Co. Ltd., Osaka, Japan).Given their wild-collected nature, there were variations in the numbers of test organisms. Specifically, each tank contained seven aquatic organisms, with some discrepancies: 13 replicate tanks (12 tanks containing 7 fish and 1 tank containing 6 fish) for C. cyanea; 9 replicate tanks (each containing 7 fish) for H. tsurugae; 9 replicate tanks (8 tanks contain-ing 7 fish and 1 tank containing 3 fish) for P. japonicus; 13 replicate tanks (12 tanks containing 7 fish and 1 tank containing 6 fish) for R. ocellatus; 13 replicate tanks (12 tanks containing 7 fish and 1 tank containing 5 fish) for P. parva; 11 replicate tanks (10 tanks containing 7 fish and 1 tank containing 6 fish) for M. anguillicaudatus; and 14 replicate tanks (13 tanks containing 7 crustaceans and 1 tank containing 4 crustaceans) for N. denticulate.To ensure gastrointestinal tract emptiness after transfer to the 5 L glass tanks, no feed was provided to the aquatic organisms for 24 h. Subsequently, they were exposed to a mixture of five different colored microplastics at a total con-centration of 87.5 mg/L for 4 h (until feeding behavior ceased) under light conditions. Exposure time was determined based on the feeding behavior duration observed in a previous study (Okamoto et al. [16]). During exposure, mixture of five different colored microplastics were circulated by aeration. After 4 h of microplastic exposure, the aquatic organ-isms were anesthetized using 200 mg/L MS-222, and their gastrointestinal tracts were dissected. Microplastic color and number in the gastrointestinal tract were assessed under a stereomicroscope (SZ61, Olympus).