Search

Coral reef ecosystem, which is one of the most important marine ecosystems, is suffered from serious degradation due to climate change (such as global warming and ocean acidification) and human activities (such as overfishing, chemical pollution). Organic ultraviolet absorbents (OUVs) are a kind of emerging "pseudo-persistent" organic pollutants. Previous studies indicated that OUVs have an importantly negative influence on coral health and are ubiquitous in various coral reef regions. To systematically understand the toxicity mechanism and ecological risk of OUVs to corals, this paper reviewed the toxicological effects of OUVs on corals from the perspectives of toxicological experiment design and toxicological effect endpoint. The results show that OUVs are toxic to corals at individual, tissular and molecular levels, with the toxicological endpoints of lethality, bleaching, tentacle retraction, [ABSTRACT FROM AUTHOR]

Reconstructing the precise timing of sea level fall is important for understanding earth system during the geologic time. However, previous studies are limited by the absence of effective indicators for sea level fall. To overcome this limitation, we investigated the 87Sr/86Sr and petrologic features of carbonate strata in a 928.75-m-long coral reef core (CK2) from Xisha Islands, northern South China Sea and their relationship to sea level fluctuations. Ten exposed surfaces were identified by their petrologic features. The Mn and Sr content, Mn/Sr, Sr/Ca and δ18O suggest that most of the coral reef carbonate in the CK2 core preserved the original seawater 87Sr/86Sr except at intervals of 672–616, 596–575, 521–491, 423–414, and 192.5–161 m, which suffered alteration of meteoric water and showed higher 87Sr/86Sr during low sea level period. The 160 carbonate 87Sr/86Sr showed a continuously increasing trend, which is consistent with that of seawater over the same period. The continuously increasing 87Sr/86Sr curve of CK2 was divided into seven units by six 87Sr/86Sr hiatuses. Inconsistency between the sedimentation rate of CK2 and tectonic subsidence rate in the Xisha area suggest that the continuously increasing 87Sr/86Sr was controlled by the coupled effect of tectonic subsidence and sea level change, and the hiatus and higher 87Sr/86Sr interval in the 87Sr/86Sr curve were controlled by sea level fall. The higher 87Sr/86Sr usually produced during low sea level (<5 m), 87Sr/86Sr hiatus usually produced when sea level changed from deeper to shallower. The depth of hiatuses and higher intervals of 87Sr/86Sr correspond well with the exposed surface in CK2 core, verifying that the hiatuses and higher intervals of 87Sr/86Sr in the coral reef carbonate succession provide an effective indicator of sea level fall. Using this indicator and the CK2 87Sr/86Sr profile, we identified eleven large-scale sea level falls and three dramatic regressions during 19.6–0.2 Ma and constrained the age based on strontium isotope stratigraphy. These interpreted sea level falls are mostly consistent with other records of global sea level changes, confirming the reliability of our records. The 87Sr/86Sr profile of a coral reef carbonate is an efficient indicator of past sea level falls, including their timing. • 87Sr/86Sr ratios of carbonate in a coral reef core from Xisha Islands. • The core indicated five hiatuses and six anomalously high ratios in Sr isotope. • Hiatus and high ratios in reef carbonate Sr isotope were produced by sea level fall. • Eleven major lower sea level and three dramatic regressions found during 19.6–0.2 Ma. • This method provides an effective indicator of past sea level fluctuation. [ABSTRACT FROM AUTHOR]

We have previously shown that the coralline algal assemblages (CAAs) of the South China Sea may indicate post-Pliocene paleo-water depth changes; however, the pre-Pliocene coralline algal compositions and related sea-level significance remain to be elucidated. In the present study, we explore the Miocene coralline algal compositions and their role in recording the sea level, and show the distribution, classification, type, abundance, and diversity of Miocene coralline algae from 213 petrologic thin sections using a coral-reef carbonate sequence from the northern South China Sea. The diversity and abundance of coralline algae in the early and late Miocene are higher than those in the middle Miocene. Eleven genera were identified and grouped into seven CAAs, showing a water depth range from <5 m to >25 m. At 18.67–17.98 Ma, the coral reef was in a stagnation/drowning stage, with rising sea levels exceeding the development of the coral reef. At 17.98–16.78 Ma, the coral reef was in a rapid development during a rapid rise in sea level. Additionally, at 16.78–14.79 Ma, low coralline algal abundance was observed, and the corals were sporadically distributed at a relatively stable sedimentation rate, suggesting a decline in coral reef development. At 14.79–10 Ma, the coral reef development was remarkably slow or stagnant. Furthermore, at 10–5.3 Ma, the coral reefs developed slowly, indicating a gradual rise in the sea level. The sea-level changes indicated by coral reef development are consistent with the long-term global sea-level changes, indicating that the composition and assemblage of Miocene coralline algae can be used to accurately relay the sea-level history. • Eleven coralline algal genera were identified in a Miocene carbonate sequence. • Miocene coralline algae were divided into 7 coralline algal assemblages (CAAs). • Sea-level changes due to coral reef development were consistent with global values. [ABSTRACT FROM AUTHOR]

Most studies on coral bleaching alerts use common Degree Heating Week (DHW) thresholds; however, these may underestimate historical patterns of heat stress for coral reef ecosystems. Taking an optimized DHW threshold for coral bleaching alerts for Coral Reef Watch (CRW) and Coral Reef Temperature Anomaly Database (CoRTAD) products, we analyzed the precise spatial and temporal pattern of heat stress on China's coral reefs from 2010 to 2021 in the South China Sea (SCS) and the Beibu Gulf (BG). We compared acute heat stress using common and optimized thresholds. Results indicated that the ocean warming rate in 2010–2021 was approximately 0.43 ± 0.22 °C/10a, showing a significant increase in the northern SCS and the BG. More severe bleaching events were predicted by the optimized thresholds and the high-frequency areas were mainly in the northern SCS. The number and intensity of years with severe heat stress anomalies was in the order 2020 > 2014 > 2010 > 2015. Heat stress duration was the longest in the Xisha Islands among offshore archipelagos, and longest in 2020–2021 in Weizhou Island in BG in the relative high-latitude inshore reefs. These abnormal events were mainly caused by El Niño, but La Niña was also involved in 2020. • The most intense severe heat stress anomaly years were 2010 > 2014>2020 > 2015. • The anomaly duration of offshore islands was Xisha > Dongsha > Zhongsha > Nansha Islands. • High-latitude reefs were predicted not to be future thermal refuges for SCS reefs. • The optimized DHW threshold more accurately predicted spatiotemporal heat stress. [ABSTRACT FROM AUTHOR]