Evaluation of the ecological status of shallow-water coral reefs in China using a novel method and identification of environmental factors for coral decline.

Coral reefs worldwide have faced extensive damage due to natural catastrophes and anthropogenic disturbances.The decline can cause their widespread collapse and an inability to recover from natural disturbances, highlighting the urgent need for their protection. This study conducted an extensive ecological condition assessment of seven coral reef regions in China's offshore. Our findings revealed the presence of 204 species of scleractinian corals belonging to 16 families. Massive corals were the predominant reef-building corals in all regions. The degradation of coral reef ecosystems was apparent in the present compared to historical reef conditions. The ecosystem suffered varying degrees of damage in surveyed regions according to a novel assessment approach, impling more effective measures should be taken to mitigate the local pressures. Our research establishes a baseline for understanding the status of coral reefs that can be used in future and provides a crucial foundation to designate protective zones for their conservation.

Characteristics of Phytoplankton Biomass, Primary Production and Community Structure in the Modaomen Channel, Pearl River Estuary, with Special Reference to the Influence of Saltwater Intrusion during Neap and Spring Tides.

In recent decades, increasing frequency and intensity of saltwater intrusion in the Modaomen Channel has threatened the freshwater supply in the surrounding cities of the Pearl River Estuary, and ulteriorly changed the environmental conditions of the estuarine waters. Phytoplankton biomass, primary production (PP) and species composition, as well as hydrological and chemical parameters were examined along a downstream transect in the Modaomen Channel during neap tide (NT) and spring tide (ST), when a strong saltwater intrusion event occurred in late September, 2011. A total of 46 species phytoplankton were identified, including Bacillariophyta (25 species), Dinoflagellate (14 species), Chlorophyta (4 species), Cyanophyta (2 species) and Euglenozoa (1 species). The dominant species were shifted from freshwater diatoms (e.g., Melosira granulata and Melosira granulata var. angustissima) in the upper reaches to saline water diatoms (e.g., Skeletonema costatum and Coscinodiscus sp.) in the river mouth. Generally, phytoplankton density, biomass (chl-a) and PP decreased from the upper to lower reaches along the channel, and were significantly higher in NT than those of ST. There was a shift from large-sized phytoplankton (>20 µm) in the upper reaches to relative small-sized cells (5-20 µm) in the lower reaches. Compared to NT, low discharge and flow velocity, coupled with strong easterly winds during ST specially aggravated saltwater intrusion further to the upstream (~50 km from the estuary). The intruded saltwater diluted nutrients, N/P ratios, chl-a, and phytoplankton abundances, and thereby led to a decline in PP during ST.