Anthozoa

About: Anthozoa is a research topic. Over the lifetime, 591 publications have been published within this topic receiving 24179 citations.

Flexibility in algal endosymbioses shapes growth in reef corals

Abstract: The relation between corals and their algal endosymbionts has been a key to the success of scleractinian (stony) corals as modern reef-builders, but little is known about early stages in the establishment of the symbiosis. Here, we show that initial uptake of zooxanthellae by juvenile corals during natural infection is nonspecific (a potentially adaptive trait); the association is flexible and characterized by a change in (dominant) zooxanthella strains over time; and growth rates of experimentally infected coral holobionts are partly contingent on the zooxanthella strain harbored, with clade C-infected juveniles growing two to three times as fast as those infected with clade D.

Metagenomic analysis of the microbial community associated with the coral Porites astreoides.

Abstract: The coral holobiont is a dynamic assemblage of the coral animal, zooxanthellae, endolithic algae and fungi, Bacteria,Archaea and viruses Zooxanthellae and some Bacteria form relatively stable and species-specific associations with corals Other associations are less specific; coral-associated Archaea differ from those in the water column, but the same archaeal species may be found on different coral species It has been hypothesized that the coral animal can adapt to differing ecological niches by 'switching' its microbial associates In the case of corals and zooxanthellae, this has been termed adaptive bleaching and it has important implications for carbon cycling within the coral holobiont and ultimately the survival of coral reefs However, the roles of other components of the coral holobiont are essentially unknown To better understand these other coral associates, a fractionation procedure was used to separate the microbes, mitochondria and viruses from the coral animal cells and zooxanthellae The resulting metagenomic DNA was sequenced using pyrosequencing Fungi, Bacteria and phage were the most commonly identified organisms in the metagenome Three of the four fungal phyla were represented, including a wide diversity of fungal genes involved in carbon and nitrogen metabolism, suggesting that the endolithic community is more important than previously appreciated In particular, the data suggested that endolithic fungi could be converting nitrate and nitrite to ammonia, which would enable fixed nitrogen to cycle within the coral holobiont The most prominent bacterial groups were Proteobacteria (68%), Firmicutes (10%), Cyanobacteria (7%) and Actinobacteria (6%) Functionally, the bacterial community was primarily heterotrophic and included a number of pathways for the degradation of aromatic compounds, the most abundant being the homogentisate pathway The most abundant phage family was the ssDNA Microphage and most of the eukaryotic viruses were most closely related to those known to infect aquatic organisms This study provides a metabolic and taxonomic snapshot of microbes associated with the reef-building coral Porites astreoides and presents a basis for understanding how coral-microbial interactions structure the holobiont and coral reefs

Chronic nutrient enrichment increases prevalence and severity of coral disease and bleaching.

Abstract: Nutrient loading is one of the strongest drivers of marine habitat degradation. Yet, the link between nutrients and disease epizootics in marine organisms is often tenuous and supported only by correlative data. Here, we present experimental evidence that chronic nutrient exposure leads to increases in both disease prevalence and severity and coral bleaching in scleractinian corals, the major habitat-forming organisms in tropical reefs. Over 3 years, from June 2009 to June 2012, we continuously exposed areas of a coral reef to elevated levels of nitrogen and phosphorus. At the termination of the enrichment, we surveyed over 1200 scleractinian corals for signs of disease or bleaching. Siderastrea siderea corals within enrichment plots had a twofold increase in both the prevalence and severity of disease compared with corals in unenriched control plots. In addition, elevated nutrient loading increased coral bleaching; Agaricia spp. of corals exposed to nutrients suffered a 3.5-fold increase in bleaching frequency relative to control corals, providing empirical support for a hypothesized link between nutrient loading and bleaching-induced coral declines. However, 1 year later, after nutrient enrichment had been terminated for 10 months, there were no differences in coral disease or coral bleaching prevalence between the previously enriched and control treatments. Given that our experimental enrichments were well within the ranges of ambient nutrient concentrations found on many degraded reefs worldwide, these data provide strong empirical support to the idea that coastal nutrient loading is one of the major factors contributing to the increasing levels of both coral disease and coral bleaching. Yet, these data also suggest that simple improvements to water quality may be an effective way to mitigate some coral disease epizootics and the corresponding loss of coral cover in the future.

Different algal symbionts explain the vertical distribution of dominant reef corals in the eastern Pacific

Abstract: Symbiotic reef corals occupy the entire photic zone; however, most species have distinct zonation patterns within the light intensity gradient. It is hypothesized that the presence of specific symbionts adapted to different light regimes may determine the vertical distribution of particular hosts. We have tested this hypothesis by genetic and in situ physiological analyses of the algal populations occupying two dominant eastern Pacific corals, over their vertical distribution in the Gulf of California. Our findings indicate that each coral species hosts a distinct algal taxon adapted to a particular light regime. The differential use of light by specific symbiotic dinoflagellates constitutes an important axis for niche diversification and is sufficient to explain the vertical distribution patterns of these two coral species.