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The seasonal and individual variations (between holdfast, basal, middle, upper blade regions and receptacles) of mannitol in Sargassum siliquastrum collected monthly over a 30-month period were investigated using HPLC. Seasonal variations of mannitol ranged from about 1 to 17% of algal dry weight. The mannitol content was found to increase with growth and peaked during the active growing stage from September (10.81 ± 4.87 g mannitol (100 g)−1 dw) to October (13.17 ± 5.60 g mannitol (100 g)−1 dw). Declining mannitol content was recorded at the start of the reproductive period in December and remained stable thereafter. A dramatic decrease occurred after the reproductive period in February (4 g mannitol (100 g)−1 dw) followed by an increase in the middle of the slow growth stage in April that ranged from 5.69 ± 2.11 in 2005 to 17.87 ± 7.46 g mannitol (100 g)−1 dw in 2006, suggesting that the surplus produced during the slow growth period may be used to maintain the perennial holdfast or to develop new shoots for the next season. On an individual level, more mature basal part of the thallus (i.e. holdfast and basal blade region) contained higher levels of mannitol when compared with the younger middle and upper blade regions. Receptacles of S. siliquastrum displayed the lowest mannitol content, which appeared to match their low photosynthetic activity. The disproportionally high level of mannitol in the photosynthetically less active holdfast suggested that mannitol may be diffused from the basal blades down to the holdfast to be utilized for the development and elongation of new shoots. © 2023, The Author(s), under exclusive licence to Springer Nature B.V.

Despite widespread climate-driven reductions of coral cover on tropical reefs, little attention has been paid to the possibility that changes in the geographic distribution of coral recruitment could facilitate beneficial responses to the changing climate through latitudinal range shifts. To address this possibility, we compiled a global database of normalized densities of coral recruits on settlement tiles (corals m-2) deployed from 1974 to 2012, and used the data therein to test for latitudinal range shifts in the distribution of coral recruits. In total, 92 studies provided 1253 records of coral recruitment, with 77% originating from settlement tiles immersed for 3-24 mo, herein defined as long-immersion tiles (LITs); the limited temporal and geographic coverage of data from short-immersion tiles (SITs; deployed for

Coral reefs are significant ecosystems. The ecological success of coral reefs relies on not only coral-algal symbiosis but also coral-microbial partnership. However, microbiome assemblages in the South China Sea corals remain largely unexplored. Here, we compared the microbiome assemblages of reef-building corals Galaxea (G. fascicularis) and Montipora (M. venosa, M. peltiformis, M. monasteriata) collected from five different locations in the South China Sea using massively-parallel sequencing of 16S rRNA gene and multivariate analysis. The results indicated that microbiome assemblages for each coral species were unique regardless of location and were different from the corresponding seawater. Host type appeared to drive the coral microbiome assemblages rather than location and seawater. Network analysis was employed to explore coral microbiome co-occurrence patterns, which revealed 61 and 80 co-occurring microbial species assembling the Galaxea and Montipora microbiomes, respectively. Most of these co-occurring microbial species were commonly found in corals and were inferred to play potential roles in host nutrient metabolism; carbon, nitrogen, sulfur cycles; host detoxification; and climate change. These findings suggest that the co-occurring microbial species explored might be essential to maintain the critical coral-microbial partnership. The present study provides new insights into coral microbiome assemblages in the South China Sea.