Variations in the coral community at the high-latitude Bailong Peninsula, northern South China Sea.

High-latitude coral communities have attracted much attention due to their potential as refuges during global climate change. However, this function is being constrained by the combined pressure of global climate and anthropogenic activities. To determine how the reef has developed, we conducted a long-term monitoring study on coral communities along the Bailong Peninsula in the northern South China Sea. The results showed that the distribution area of corals was 3.67 km2 and that corals extended about 4.7 km along the coastline. The coral distribution pattern is scattered and uneven. Our results showed that the growth of reef-building corals and coral recruitment are improving, indicating that coral recruitment plays an important role in regulating the structure of adult coral populations and promoting the development of coral communities. Bailong Peninsula is expected to become a refuge for corals provided that human activities impacting coral restoration potential are controlled.

New Insights into the Microplastic Enrichment in the Blue Carbon Ecosystem: Evidence from Seagrass Meadows and Mangrove Forests in Coastal South China Sea.

Microplastics were recently found to aggregate in the blue carbon ecosystems (BCEs), which are known for their ability to store carbon by slowing down the water flow. However, evidence is largely lacking on how the accumulation of microplastics is related to carbon sequestration in BCEs and if this trap effect is driven by its biological characteristics. In this study, the trap effect of microplastics by BCEs was evaluated for various seagrasses (Zostera japonica, Halophila ovalis, and Halophila beccarii) and mangroves (Aegiceras corniculatum and Avicennia marina). Significant accumulation was found in the seagrass meadow dominated by H. beccarii and the mangrove forest dominated by A. marina, with microplastics enriched by 1.3 to 17.6 times compared to their corresponding unvegetated sites. The abundance of microplastics varied greatly from 17.68 ± 8.10 to 611.75 ± 81.52 particles per kg of dry sediment, with the highest abundance in A. marina mangrove sediments. A strong positive correlation was found between the abundance of microplastics and the particulate organic carbon content at all study sites (Pearson, R = 0.86, p < 0.01). Higher diversity of microplastic colors and size was found in the H. beccarii meadow, and higher diversity of shapes was found in the A. marina forest. Our results added new insights to the understanding of the mechanism of microplastic trapping by BCEs and coupled the behavior of microplastics with the organic carbon in the sediment.

Seagrass beds store less carbon but support more macrobenthos than mangrove forests.

Seagrass beds (SG) have powerful ecosystem functions, but some seagrasses, e.g., Halophila beccarii, have been neglected because of their tiny plant structure and narrow and restricted distribution in the intertidal zone. In this study, we compared ecosystem structure and function between H. beccarii SG and adjacent coastal habitats through: (i) vegetation composition, (ii) carbon storage, and (iii) macrobenthic community. The vegetation carbon storage was only 0.1% of that in mangrove forests (MG). The sediment carbon storage (0-60 cm) of SG (67.4 ± 20.2 MgCorg·ha-1) was 74.31% of MG (90.7 ± 12.9 MgCorg·ha-1) and 13.51% higher than unvegetated flats (UnV) (55.1 ± 17.7 MgCorg·ha-1). The macrobenthic abundance, biomass and secondary productivity in SG were significantly higher than those in MG, indicating that SG support more macrobenthos than MG. However, SG experienced more disturbances than MG and UnV. Therefore, it is necessary to strengthen the protection of H. beccarii SG to preserve their essential functions and services.

Changes in carbon storage and macrobenthic communities in a mangrove-seagrass ecosystem after the invasion of smooth cordgrass in southern China.

The exotic smooth cordgrass (Spartina alterniflora) has invaded intertidal wetlands near the Ronggenshan tidal flats of Beihai, Guangxi, China, where historically seagrasses and mangroves coexisted. We investigated sediment organic carbon (SOC) storage and macrobenthic community structure in the existing mangroves (MG), S. alterniflora (SA), seagrass bed (SG), and unvegetated flat (UnV) habitats following the S. alterniflora invasion. SOC storage increased after S. alternifolia invasion in the SG and UnV habitats. Spartina alterniflora invasion changed the dominant species of the macrobenthos in the original habitats and reduced the diversity of macrobenthos in SG and UnV habitats. Clearly, S. alternifolia invasion can change the ecological functioning of south China's coastal ecosystems by altering carbon sequestration and affecting biodiversity.