The impact of coastal upwelling on coral reef ecosystem under anthropogenic influence: Coral reef community and its response to environmental factors

Abstract

Mass coral bleaching is a severe threat to coral reefs in the era of global warming, and upwelling areas may serve as thermal refugia for coral reefs by mitigating the effects of heating anomalies. This study seeks to examine the impact of the Qiongdong upwelling (QDU) on the coastal coral reefs of the Hainan Island. The environmental variables (i.e., physiochemical parameters, coastal land use) differed significantly in upwelling and non-upwelling areas. In particular, the presence of colder and more saline water was the important indicator of coastal upwelling. In the QDU, turf algae and macroalgae dominated the algae communities, but habitat-specific environment and coastal development contributed to lower calcified algae, coral larvae replenishment and live corals cover. Lower abundance of coral reefs fishes could be attributed to the disappearance of live corals, increase of algae coverage, low habitat complexity and strong wave exposure at upwelling stations. Upwelling-related environmental parameters, wave exposure, land use and potential local stressors were revealed as major driving factors related to significant spatial changes in stony coral and fish communities. Overall, the present findings suggest that the Qiongdong upwelling has the potential to provide thermal refuge for coral reefs, but is severely affected by local anthropogenic activities.

Coastal Upwelling Under Anthropogenic Influence Drives the Community Change, Assembly Process, and Co‐Occurrence Pattern of Coral Associated Microorganisms

“…It is well known that moderately rich nutritional conditions promote the growth of Symbiodiniaceae and increase their density, and ammonium (NH 4 + ) is the preferred inorganic nitrogen source for algal symbionts (Ezzat et al., 2015). Both terrestrial input and upwelling can increase the concentration of dissolved inorganic nutrients in coastal areas (Dobson et al., 2021; Zhu et al., 2022b), which explains why in this study the Symbiodiniaceae density of the upwelling zone was higher but not significantly higher. Symbiont density and Symbiodiniaceae type are related to the ability of the coral hosts to produce energy, and higher Symbiodiniaceae density is beneficial to maintaining the coral hosts and storing energy substances in the form of lipids or proteins (Jung et al., 2021).…”

“…Land use legacies of the past often have an important effect on the current biological diversity, community structure, and ecosystem function (K. Chen & Olden, 2020; Perring et al., 2016), and upwelling‐related environmental parameters and land use are major driving factors that co‐shape specific coral reef communities in QDU coast (Zhu et al., 2022b). The land use distribution in the 6 × 6 km area upstream of each sampling site were categorized into grassland, woodland, cultivated land, construction land, and unused land (Zhu et al., 2022b) using Landsat 8 remote sensing images of 2021 (United States Geological Survey, USGS, http://earthexplorer.usgs.gov/).…”

“…The Qiongdong upwelling (QDU) is a typical seasonal coastal upwelling driven by the summer monsoon that occurs from June to September at the east coast of the Hainan Island in the northwest of the South China Sea (Zhu et al., 2022b). Although the impact of upwelling on coral reef microbiome remains to be further studied (G. Zhou et al., 2017), the upwelling in the South China Sea is known to affect the growth of phytoplankton (Hu et al., 2021), composition of seawater microorganism (X. Liu et al., 2021; Zhu et al., 2022a), and coral community (X. Li et al., 2015; Zhu et al., 2022b).…”

Adaptive changes of coral Galaxea fascicularis holobiont in response to nearshore stress

“…Each sample was subsampled and divided into two parts, one for physiological measurements and the other for DNA extraction. General environmental parameters, including water temperature, salinity, dissolved oxygen, pH, and turbidity, were determined according to the standard methods described in our previous study ( Zhu et al, 2022a ). Seawater samples were collected near coral samples, filtered immediately (Whatman GF/F), and stored at low temperatures.…”

“…Therefore, they provide a unique opportunity to investigate the relationship of coral holobionts to environmental disturbances. Galaxea fascicularis is widely distributed in the Indo-Pacific region, and it is an essential ecological and dominant species in the SCS ( Zhou et al, 2017 ; Zhu et al, 2022a ). Due to its resistance to environmental changes and stress, it can be used as an important model organism to study the response mechanism of coral holobionts to the environment.…”