Plastic pollution in a coral reef climate refuge: Occurrence of anthropogenic debris, microplastics, and plasticizers in the Gulf of Aqaba.

The Gulf of Aqaba in the northern Red Sea, considered a coral reef refuge from the negative effects of climate change, is however being subjected to increasing amounts of plastic contamination. We quantified the levels of benthic plastic debris, microplastics, and plasticizers within the coral reef's surrounding seawater and sediment over time. Our results indicate that the coral reefs of the GoA have relatively lower levels of plastic pollution compared to reefs in other regions. The measured benthic debris in the Red Sea reefs was found to be 0.093 ± 0.091 item/m2 and fell within the reported levels found in other tropical coral reefs, with boating and fishing materials being the most abundant type. Deep mesophotic reefs were found to have significantly higher levels of benthic plastic debris compared to the shallower reefs. Microplastic levels in the surrounding seawater of the reef were 0.516 ± 0.317 microplastics/m3. These concentrations in the reef's surrounding waters are comparable to the levels observed in surface waters from the central Red Sea. The target plasticizers appeared infrequently in samples, and the concentrations for the majority of them were below the level of quantification (LOQ = 14.7 ng/l for water and 14.7 ng/g for sediment). The findings from this study provide a valuable scientific basis for shaping regional policies and implementing management strategies aimed at controlling and mitigating plastic pollution. Such policies can ensure the long-term protection of the reefs in the northern Red Sea, turning them into a secure coral refuge shielded from both global and local anthropogenic stressors.

Limited effects of environmentally-relevant concentrations in seawater of dibutyl phthalate, dimethyl phthalate, bisphenol A, and 4-nonylphenol on the reproductive products of coral-reef organisms.

Plastic additives (PAs) are chemical compounds incorporated into the plastic during the manufacturing process. Phthalate acid esters, bisphenols, and nonylphenols are all PAs found in marine environments and associated with endocrine-disrupting processes. However, our knowledge regarding the impact of endocrine-disrupting PAs on coral-reef organisms is limited. As reef population structure is directly linked to reproduction and larval settlement processes, interference with hormonal systems can impact coral-reef community structure, particularly if the effects of PAs differ among species. In the current study we exposed the reproductive products of four tropical coral-reef invertebrates to environmentally-relevant concentrations of four prevalent PAs in seawater: dibutyl phthalate (DBP), dimethyl phthalate, (DMP), 4-nonylphenol (4-NP), and bisphenol A (BPA), as well as to 103 higher laboratory concentrations of these PAs. Our results revealed that apart from the significant negative effect of the 1 µg/L of 4-NP on the settlement of the soft coral Rhytisma fulvum, none of the other tested materials demonstrated a significant effect on the exposed organisms at environmentally-relevant concentrations in seawater. The 4-NP high laboratory concentration (1000 µg/L), however, had significant negative effects on all the examined species. The high laboratory BPA concentration (1000 µg/L) significantly reduced fertilization success in the solitary ascidian Herdmaniamomus, up to its complete failure to reproduce. Moreover, the high laboratory DMP concentration (100 µg/L) had a significant negative effect on planulae settlement of the stony coral Stylophora pistillata. Our findings demonstrate the negative and selective effects of PAs on the development and reproduction of coral-reef organisms; and, specifically, the significant effect found following exposure to 4-NP. Consequently, if we aim to fully understand the impact of these contaminants on this endangered ecosystem, we suggest that the actual concentrations within the living organism tissues should be tested in order to produce relevant risk assessments for brooding-coral species.

Using solitary ascidians to assess microplastic and phthalate plasticizers pollution among marine biota: A case study of the Eastern Mediterranean and Red Sea.

The interaction of microplastic (MP) with marine organisms is crucial for understanding the significant effect that MP and its additives may have on marine environments. However, knowledge regarding the magnitude of these pollutants in the Eastern Mediterranean Sea and the tropical Red Sea is still scarce. Here we examined the levels of phthalate acid esters (PAEs) and MP in Herdmania momus and Microcosmus exasperatus sampled along the Mediterranean and Red Sea coasts of Israel. High levels of dibutyl phthalate (DBP) and bis (2­ethylhexyl) phthalate (DEHP) were found in ascidians at the majority of sampling sites, and MP particles were found in ascidians at all sites. As efficient filter-feeders and being widely-distributed, invasive ascidians present fundamental opportunities for the environmental monitoring of microplastic and its additives worldwide. The high levels of pollutants revealed emphasize the need for further research into the magnitude and effects of MP and PAEs in these regions.