Spatial distribution of benthic algae in the South China Sea: Responses to gradually changing environmental factors and ecological impacts on coral communities

Abstract

Aim: In this study, we investigated whether environmental factors can effectively control the spatial distribution of various benthic algae and examined the critical ecological impacts of algae on corals across the South China Sea (SCS). Relationships between benthic algae and environmental factors were assessed, and potential ecological impacts of algae on coral communities were evaluated across spatial scales.Location: A total of 104 sites at 12 coral reefs in four coral reef regions (CRRs) of the SCS (latitude range of 9-22° N).Taxa: Turf algae, macroalgae (including fleshy macroalgae and Halimeda), crustose coralline algae (CCA), coral and juvenile coral.Methods: Using diver-based surveys (2015-2018), we investigated four CRRs with different reef distance to mainland (RDM) across the SCS. We obtained field data on benthic algal composition and cover, coral cover and diversity, and juvenile coral density. We also measured and collected the environmental factors (including seawater environmental parameters and reef fish diversity). Results:The cover of turf algae and CCA gradually decreased and increased, respectively, with an increase in RDM, which had a strong relationship with the gradually changing environmental factors. Random forest models suggested that nutrients, reef fish diversity, seawater transparency and temperature were the most important factors for predicting turf algae and CCA cover. Linear regression analyses showed a significant relationship between the turf algae, macroalgae, and CCA covers, and juvenile coral density. Main conclusions:Our results showed that gradually changing environmental factors were correlated with the spatial distributions of turf algae and CCA. However, the natural biophysical relationships between macroalgae and environmental factors may be disrupted by turf algal overgrowth and nutrient subsidies. Increases in all benthic algal groups significantly impacted coral recruitment, highlighting the critical role of benthic algae in determining the recovery trajectory of the Indo-Pacific reefs that are threatened by human activities.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Microbiome of juvenile corals in the outer reef slope and lagoon of the South China Sea: insight into coral acclimatization to extreme thermal environments

“…Juvenile corals are good candidates for studying extreme thermal environmental acclimatization (Holbrook et al ., 2018; Liao et al ., 2021). Global corals are rapidly degraded due to local and global disturbance, and juvenile coral recruitment is critical to the persistence and resilience of coral reefs (Albright et al ., 2010).…”

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

“…The overgrowth of turf algae and the increased in nutrients may disrupt the natural biophysical relationship between macroalgae and environmental factors (Liao et al, 2021). Consequently, although the QDU creates a suitable condition for the growth of macroalgae, they still cannot dominate inshore coral reefs on the east coast of the Hainan Island (Liao et al, 2021). In addition, the QDU and the non-upwelling waters both had very low coverage of calcified algae and coral larvae, far lower the survey in 2010.…”

“…On the other hand, coral reefs along the coast are seriously threatened by eutrophication, fisheries, and other anthropogenic impacts (Alcıvar-Mendoza et al, 2021), all of which reduced the diversity of macroalgae and increase the coverage of turf algae. The overgrowth of turf algae and the increased in nutrients may disrupt the natural biophysical relationship between macroalgae and environmental factors (Liao et al, 2021). Consequently, although the QDU creates a suitable condition for the growth of macroalgae, they still cannot dominate inshore coral reefs on the east coast of the Hainan Island (Liao et al, 2021).…”

Insights Into the Environmental Impact on Genetic Structure and Larval Dispersal of Crown-of-Thorns Starfish in the South China Sea

“…The low nutrition resistance of COTS larvae may be associated with maternal nutrition (Caballes et al, 2016). Previous studies have shown that the coral cover of Acropora was decreased with the increasing of the latitude in the SCS, and the abundance of Acropora in FTS and PS was higher than that in DI and BR (Zhao et al, 2013(Zhao et al, , 2016Li et al, 2019;Liao et al, 2021). Acropora was as preferred coral prey for COTS, which may provide high quality and quantity of food to female COTS in the FTS and PS, which might promote COTS larvae to tolerate low nutrient availability and to progress to more advanced stages faster (Caballes et al, 2016).…”