Topography of the Ganquan Plateau in the Xisha area of the South China Sea was studied using multibeam bathymetric data. The top of the Ganquan Plateau was flat with slopes generally less than 1°, but the topography was a three-level terrace tilting toward the southwest with water depth ranging from 550–700 m. At water depth of 600–850 m, submarine terraces commonly developed with up to 5 levels recognized, and the terraces in the west were more developed than those in the east of the Ganquan Plateau. It is preliminarily believed that the top and peripheral terrace topography of the Ganquan Plateau was a result of the combined effects of the global sea level change at the time scale of glacial-interglacial cycle and the crust subsidence of the South China Sea. These two influencing factors might control the development of the other coral reefs in the South China Sea as well. Talus topography developed at the periphery of the Ganquan Plateau at water depth between 850 and 1 300 m, which is speculated to result from deposits of coral fragments transported from the top of reefs. The more developed talus topography in the northwest compared to that in the southeast might be directly related to the southwest tilt of the top of the Ganquan Plateau.
Coralline algae are common in calcified red algal groups and an essential component of coral reefs. In addition, they play an important role in the process of coral reef development: 1) Coralline algae provide calcium for building the reef body; 2) coralline algae have strong binding and gluing ability to glue the broken biological fragments together and build coral reefs that can withstand strong winds; 3) coralline algae’s hard calcareous surfaces provide rigid basements for coral larvae to attach and grow; 4) coralline algae promote energy flow in coral reef ecosystems through photosynthesis; 5) coralline algae’s high primary productivity helps to maintain the efficiency of material cycle in coral reef ecosystems. Current research on coralline algae is focused on coralline algae’s responses to environmental stresses such as global warming and ocean acidification, and on the relations between the community structure, species diversity and spatial and temporal variations of coralline algae and environment changes. Further studies will be conducive to reveal the multiple functions of coralline algae in coral reef ecosystems.
In this article, Reef Check (coral reef health survey procedure) and factor analysis of coral reef ecosystem health index were used to evaluate the health status of the coral reefs at three sites (Zhuzheliao, Gongshan and Niubeikeng) of the Weizhou Island, Beihai, Guangxi Province from 2001 to 2012, focusing on fishes, invertebrates and reef substrates. The investigation results indicated that, during the nine years, coral reef ecological conditions showed big differences in different peripheral regions of the Weizhou Island. Although coral reef coverage was stable in Zhuzheliao and Niubeikeng, dominant population changed. But in Gongshan, coral death has occurred over a large area since 2002 and has not recovered up till now. Invertebrates were at extremely low levels, and fishes were also poor in both population quantity and diversity. This indicated that in this region, the coral reef ecosystem bore a heavy pressure from human activities.
The coral reefs in the Weizhou Island (WZR) are located at the northern margin of the tropical zone, and have been developing on the volcanic rocks for at least 7000 years. This paper reviewed the related studies on the coral reefs and summarized the characteristics of WZR as follows: 1) The living coral covers of WZR have substantially declined over the past two decades. For example, the coral cover reduced by 51.6% in the north (2009–2010), by 42.42% in the southeast (1991–2010), and by 71.55% in the southwest (1991–2010); 2) the relatively high-latitude Weizhou Island is an ideal site for testing the refuge hypothesis that, under the background of global warming, corals are migrating from low-latitude areas to high-latitude areas; 3) as the basement rocks of WZR are volcanic rocks, this is an excellent case for testing Darwin’s atoll origin hypothesis; 4) the Weizhou Island is experiencing heavy anthropogenic activities, thus it is a natural laboratory to study the interactions between human and coral reefs and how this relatively high-latitude coral reef responds to the global warming, extreme climatic events and anthropogenic stresses. Therefore, as an important resource, the WZR are not only of vital ecological and environmental significance as other coral reefs, but also of unique scientific value and deserve close attention for effective protection.
Coral reefs are degraded rapidly by the global warming and large-scale human activities around the world, especially in the South China Sea (SCS). Coral reef restoration has caught the attentions of researchers and volunteers in recent years. Related theories and technologies are to be developed, but undoubtedly, the most important strategy is to protect the eco-environment of coral reefs to avoid further damage. For coral reef restoration, coral transplantation is a promising way. After corals are transplanted, the damaged tissues can be repaired in a few days, the immune system can be rebuilt, and the symbiont (zooxanthellae) community structure can be changed to enhance coral’s adaptation to the new environment. Gardening and captive breeding are effective ways to provide transplantation materials while artificial reefs are an important means to help establish coral development base. Creating and maintaining the growth environment for corals can help to raise the efficiency of ecological restoration. Spread and survival of coral larva can be promoted with the help of favorable water flow, chemical induction and microtopography. The environment-tolerant capacity and recovery potential of corals and they symbiotic zooxanthellae can be improved using molecular technologies. Coral restoration technologies including coral transplantation, gardening, artificial reefs, coral repair and captive coral breeding can be employed effectively in lots of areas.
