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The ocean is the largest carbon reservoir and plays a crucial role in regulating atmospheric CO2 levels, especially in the face of climate change. In coral reef ecosystems, the complexity and importance of the carbonate system must be better appreciated as atmospheric CO2 concentrations continue to rise. This study measured p CO2 over time and space in Nanwan Bay, a coral reef ecosystem in Southern Taiwan, to identify factors that influence its variation. The results showed that mean p CO2 values varied seasonally, with values of 394 µatm in spring, 406 µatm in summer, 399 µatm in fall, and 367 µatm in winter. These seasonal differences (Δ p CO2) were -2, 14, 7, and -29 µatm, respectively. These findings suggest that the Nanwan Bay coral reef ecosystem acts as a sink for atmospheric CO2 during the spring and winter, with an average sea-air gas flux of -1 gC m-2 year-1 and a net annual uptake of -29 t. The carbonaceous parameters of the surface water in this high-biodiversity sub-tropical marine ecosystem were influenced not only by seasonal temperature variation but also by vertical mixing, intermittent upwelling, and biological effects. [ABSTRACT FROM AUTHOR] more...

Ocean warming and marine heatwaves caused by climate change are adversely affecting the health, structure, and function of coral reefs globally. As seawater temperature continues to rise, and with the intensity and duration of heat stress events expected to increase, it is pertinent to understand the environmental drivers of variability in coral thermal tolerance under both chronic and acute warming. We assessed the performance of three species of corals, Acropora nana, Pocillopora acuta, and Porites lutea, sourced from reefs with distinct thermal regimes (variable vs. stable) in southern Taiwan, when exposed to chronic long-term temperature conditions (12 weeks at 26 °C or 30 °C) and then, using a subset of corals, subsequently exposed to acute short-term elevated temperature conditions (8 days at 32 °C). Under chronic temperature exposure we found clear species-specific responses, and some differences between reef sites and temperature treatments. Despite being perceived as relatively thermally sensitive, A. nana had the most stable maximum quantum yield (Fv/Fm), consistent growth, and the highest survival among the study species. Survival of P. acuta under chronic warming showed the clearest reef site effect and was lower in coral nubbins sourced from the thermally stable reef than the thermally variable reef. Porites lutea showed the greatest decline in Fv/Fm and lowest overall growth under chronic temperature exposure. All coral species, regardless of source reef site or previous chronic temperature exposure, experienced substantial bleaching (50–100% of all nubbins) upon acute exposure to elevated temperature. We found that, overall, corals were able to tolerate chronic warming above seasonal mean temperatures, but that bleaching occurred after acute exposure to a temperature ~ 2 °C above their mean summer maxima. [ABSTRACT FROM AUTHOR] more...

Global warming and anthropogenic pressures present serious threats to coral reefs. Various stressors caused by human activities have been shown to negatively influence coral reproduction and recruitment. Because these threats are unlikely to abate in the immediate future, conservation projects involving larval release monitoring programmes are needed. Therefore, we measured larval release from captive colonies of a common Indo-Pacific reef coral, Seriatopora caliendrum, between October 2018 and December 2019. The largest larvae release event occurred in May 2019, and the smallest one occurred in September 2019. Several coral reproductive features demonstrated a close connection with seawater temperature. In contrast to prior studies conducted at the same institute with corals belonging to the same genus, of the same average size, originating from the same site, and cultured under the same conditions, we documented decreased fecundity of Seriatopora corals ex situ in 2018–2019. Various types of disturbance influence the study site from which corals were originally collected. We propose that local human activities and large-scale physical disturbances have negatively affected coral fecundity in southern Taiwan. [ABSTRACT FROM AUTHOR] more...

Coral reefs are of global concern in the face of increasing anthropogenic disturbance. Much research has focused on the negative factors associated with coral reef decline, but few have documented the positive factors in relation to recovering coral reefs. Here, we report a positive quantitative association between sea urchins (diadematids), coral recruitment and coral recovery, recorded along Taiwanese coral reefs. We monitored coral cover change, juvenile coral density, herbivore density (fishes, sea urchins, gastropods) and macroalgal cover, along three reefs between 2012 and 2015. Multivariable regression analyses revealed that sea urchin (diadematids) density was the primary (positive) driver, explaining 74% of variation in coral cover change and 89% in coral juvenile density among sites and years. The relationship between sea urchin density and coral juvenile density was especially evident for four common coral genera: Acropora, Dipsastraea, Pocillopora and Porites. These results suggest that diadematid urchins enhance coral recovery on these reefs by promoting the recruitment of corals. The density of juvenile corals was also found to explain 67% of variation in coral cover change, highlighting the potential use of coral juvenile density as a proxy for coral recovery potential in coral resilience studies. [ABSTRACT FROM AUTHOR] more...

Fine sediments, which account for the majority of total fluvial sediment flux, have been suggested to degrade coral reefs on a global scale. Furthermore, sediment impacts can be exacerbated by extreme rainfall events associated with global climate change and anthropogenic nutrient enrichment. We report the findings from a series of mesocosm experiments exploring the effects of short-term sedimentation and nutrient enrichment on the interactions between the hard coral Acropora muricata, the sea anemone Mesactinia ganesis, and the green macroalga Codium edule. Mesocosms were manipulated to simulate either unimpacted reefs or reefs exposed to elevated levels of fine sediments for 10 or 14 days to simulate the effects of heavy rainfall. The first and second experiments were aimed to examine the effects of inorganic and organic sediments, respectively. The third experiment was designed to examine the interactive effects of nutrient enrichment and elevated sediment loads. Neither inorganic nor organic sediment loadings significantly affected the physiological performance of the coral, but, importantly, did reduce its ability to compete with other organisms. Photosynthetic efficiencies of both the green macroalga and the sea anemone increased in response to both sediment loadings when they were simultaneously exposed to nutrient enrichment. While organic sediment loading increased the nitrogen content of the green macroalga in the first experiment, inorganic sediment loading increased its phosphorus content in the second experiment. The coral mortality due to sea anemones attack was significantly greater upon exposure to enriched levels of organic sediments and nutrients. Our findings suggest that the combined effects of short-term sedimentation and nutrient enrichment could cause replacement of corals by sea anemones on certain coral reefs. [ABSTRACT FROM AUTHOR] more...

Abstract: Before 2001, the ecological protection area in the Kenting National Park (KTNP), southern Taiwan, was poorly described. In this study, a set of four-year data (2001–2004) of seawater qualities at 19 sampling sites around the Nanwan Bay in the KTNP was used to explore anthropogenic impacts to ecological environment, especially coral reefs. The parameters of water quality were analyzed immediately after collection. The results showed that higher values of nutrients and suspended solids were attributed to the higher run-off around Nanwan Bay. The fluxes of nutrients and suspended solids were consistently correlated to rainfall. Hence, equations were developed to calculate nutrient fluxes and suspended solids by using only rainfall data. Our results show that suspended solids and ammonia were the dominant factors leading to the drop in coral coverage. In summary, the water quality in the intertidal zone of Nanwan Bay has been degraded and required greater attention. [Copyright &y& Elsevier] more...

Southern Taiwan's Kenting National Park is a popular retreating place for many domestic and international tourists, with increasing tourist numbers potentially over-burdening the coastal ecosystems. To better understand human impacts, a long-term ecological research program was initiated in 2001 to track water quality at 14 coral reef-abutting sites throughout the park since then. Extracting the data from this 20-year survey, we found that increasing in the nutrient levels during the summer rainy season, together with the drops in salinity led by freshwater inputs (land- & rainfall-derived), was the main impact to coral reef ecosystem of Kenting. Cluster analysis further confirmed the nutrient influx was mainly attributed to the local discharge outlets with dense of villages and hotels at upstream. Therefore, more efforts are needed to input to control tourist number, treat waste water discharge and strengthen land protection facilities. [ABSTRACT FROM AUTHOR] more...