Jiansheng Lian

Benthic community changes following the 2010 Hainan flood: Implications for reef resilience

Abstract In the future, coastal coral reefs in Southeast Asia will be exposed to both climate change and more severe and frequent floods associated with heavy rainfall. Floodwaters have caused severe coral mortality in many near-shore coral reefs throughout the world. However, previous studies have largely ignored the effects of floodwaters on macroalgae and calcified algae and the indirect effects on benthic community interactions following flood events. In October 2010, heavy rainfall of more than 1600 mm in 9 days caused the largest flood on record in eastern Hainan Island. Long-term video transects indicate that the floodwater was responsible for severe benthic community mortality in Wenchang, northeast Hainan Island. Mean live coral cover decreased from 15.2% to 9.8% and showed strongest degradation at stations proximal to areas with a high density of aquaculture ponds (i.e. stations 3S–4S decreasing from 15.0% to 0.8%). Branching corals (Acropora and Pocillopora damicornis) were the most sensitive, while massive corals (e.g. Porites, Galaxea, Platygyra and Favia) were most tolerant of floodwaters. Calcified algae were almost completely removed at all stations; coverage decreased from 28.1% to 1.7%, while macroalgae were not influenced by floodwaters. Thus, remnant coral communities that survived the flooding in Wenchang are likely to be subject to increased competition with macroalgae and benefit less from calcified algae promoting juvenile coral recruitment.

Community structure of coralline algae and its relationship with environment in Sanya reefs, China

Coralline algae are an important functional group in coral reef ecosystems. Despite the importance of coralline algae, little is known about their abundance and community structure, especially within Sanya reefs. It was fundamental to study coralline algae species abundance and distribution, and evaluate the effects of environmental factors on the species composition and abundance in Sanya reefs. A total of 24 species in 10 genera were identified based on 11 sampling stations, with the family Corallinaceae being dominant within the study area. The 7 dominant species, which constituted 62.4% of the overall collection, were Amphiroa ephedraea (16.8%), Mesophyllum simulans (11.1%), Porolithon onkodes (9.8%), Neogoniolithon fosliei (7.5%), Mesophyllum mesomorphum (6.6%), Pneophyllum conicum (6.6%) and Hydrolithon boergesenii (4.0%). There was significant spatial variability in the species composition and abundance of coralline algae (ANOSIM: R = 0.356, P = 0.013). The correlation analysis between biotic and abiotic variables indicated that the turbidity had a negative effect and salinity had a positive correlation on the pattern of coralline algae assemblages (global ρ = 0.486, BIOENV analysis). The living cover of coralline algae was greater in deep water than in shallow water at the same sites. This suggests that physical disturbance, either natural or anthropogenic, is more important in regulating the coralline algae community structure in Sanya reefs.