Coral community changes in response to a high sedimentation event: A case study in southern Hainan Island

Xiubao Li,Jianhui Yang,Yongqiang Chen,Liangmin Huang,Cheng Ye,Jiansheng Lian,Hui Huang

doi:10.1007/s11434-012-5601-5

Abstract

A high sedimentation event caused by dredging and dumping of sediment was recorded on Xiaodonghai Reef in Yulin Bay, southern Hainan Island, China. Significantly high sedimentation and constant light shading were observed during the sediment dumping event (SD Event). Using long-term video transects, we quantified coral community changes and responses to the SD Event between 2008 and 2010. The SD Event caused severe coral mortality on Xiaodonghai Reef at a depth of 6 m, while corals at 3 m were less affected. Total live coral cover at 6 m decreased from 54.3% to 14.8%, and Diploastrea heliopora replaced Galaxea fascicularis as the dominant coral species at 6 and 9 m. The density of juvenile corals also declined after the SD Event, especially for the genera Galaxea and Platygyra. However, the density of juvenile Porites and Pocillopora spp. slightly increased. Monitoring for 11 months after the SD Event indicated no recovery of coral communities on Xiaodonghai Reef. Long-term video transect data also revealed that mean live coral cover dramatically declined, from 30.5% in 2008 to 9% in 2010, while the dominant corals in Yulin Bay shifted to more tolerant coral species, such as massive Porites spp. and D. heliopora. The rapid coral community degradation in Yulin Bay between 2008 and 2010 was probably caused by high sediment deposition resulting from intensive dredging and land-clearing activities. These results highlight the necessity for an integrated watershed management to control sediment deposition on near-shore coral reefs.

Highlights

Scleractinian corals, as the major reef-building organisms, play a key role in maintaining the stability and function of coral reef ecosystems [1]
Long-term video transect data revealed that mean live coral cover dramatically declined, from 30.5% in 2008 to 9% in 2010, while the dominant corals in Yulin Bay shifted to more tolerant coral species, such as massive Porites spp. and D. heliopora
2.1 Environmental variables and coral community changes between 2008 and 2010 on Xiaodonghai Reef High sediment accumulation rates and constant light shading were recorded on Xiaodonghai Reef during the SD Event (Figure 4)

Summary

Introduction

Scleractinian corals, as the major reef-building organisms, play a key role in maintaining the stability and function of coral reef ecosystems [1]. Dredging is an extreme event causing high sedimentation and is associated with construction of hotels, runways, roads, harbors, and military installations, as well as with beach replenishment [17,18] It has been considered as a high-risk event because of its likely deleterious effects to the marine environment and is one of the biggest potential sources of reef degradation resulting from human activities, being an especially severe risk in developing countries [17,19]. An acute sedimentation event was recorded on Xiaodonghai Reef during September–November 2009 due to dredging and dumping of sediment in Yulin Bay, southern Hainan Island This provided us with a study site for the investigation of coral community changes before and after a high sedimentation event. We investigated coral community changes between 2008 and 2010 in Yulin Bay and discuss the main causes

Methods

Results

Discussion

Conclusion