Bioconcentration and lethal effects of gas-condensate and crude oil on nearshore copepod assemblages

<p>&nbsp;To assess the toxicity of petroleum pollutants on copepod assemblages, we conducted microcosm experiments simulating slick scenarios at five different concentrations (0, 50, 250, 500, 100 ppm) of gas-condensate and crude oil. We collected natural zooplankton from a coastal station (32&deg;51'07.1 N 34&deg;59'26.2 E) on July 18, 2021 (&ldquo;gas-condensate experiment&rdquo;) and July 27, 2021 (&ldquo;crude oil experiment&rdquo;) by two horizontal Bongo net tows (200 and 65 &micro;m mesh size; 300 &micro;m mesh size), and surface seawater (sieved through a 50 &micro;m mesh). The seawater was enriched with the collected zooplankton (65 &micro;m - 2 mm size fraction) and incubated in 10 L polycarbonate container microcosms for 48 hours. After incubation, a subsample of 5 L was taken from each experimental microcosm using a hand pump. Each sample was sieved through a 50 &micro;m mesh, rinsed with 0.2 &mu;m filtered seawater, and concentrated in 200 ml in a glass beaker. The samples were examined under the stereomicroscope (SZX16, Olympus, Japan) and the number of dead (not swimming and/or not moving) and live individuals (swimming and/or moving after being gently touched with tweezers) of calanoid and cyclopoid copepods were counted for estimating survival. e data included the counts of the dead and live individuals (copepods, including calanoid and cyclopoid copepods). Survival (%) was estimated for each treatment as the live/dead ratio at the end of each incubation (48h).</p>