Seagrass Patch Complexity Affects Macroinfaunal Community Structure in Intertidal Areas: An In Situ Experiment Using Seagrass Mimics

Seagrasses, as key ecosystem engineers in coastal ecosystems, contribute to enhancing diversity in comparison with nearby bare areas. It has been proved mainly for epifauna, but data on infauna are still scarce. The present study addresses how seagrass structural complexity (i.e., canopy properties) affects the diversity of infaunal organisms inhabiting those meadows. Canopy attributes were achieved using seagrass mimics, which were used to construct in situ vegetation patches with two contrasting canopy properties (i.e., shoot density and morphology) resembling the two seagrass species thriving in the inner Cadiz Bay: Zostera noltei and Cymodocea nodosa. After three months, bare nearby areas, two mimicked seagrass patches (‘Zostera’ and ‘Cymodocea’), and the surrounding natural populations of Zostera noltei were sampled in a spatially explicit way. Shifts in organism diets were also determined using 15N and 13C analyses in available food sources and main infaunal organisms, mixing models, and niche metrics (standard ellipse area). Seagrass-mimicked habitats increased the species richness (two-fold), organism abundance (three to four times), and functional diversity compared with bare nearby areas. The clam Scrobicularia plana (deposit/filter feeder) and the worm Hediste diversicolor (omnivore) were dominant in all of the samples (> 85%) and showed an opposite spatial distribution in the reconstructed patches: whilst S. plana accumulated in the outer-edge parts of the meadow, H. diversicolor abounded in the center. Changes in the isotopic signature of both species depending on the treatment suggest that this faunal distribution was associated with a shift in the diet of the organisms. Based on our results, we concluded that facilitation processes (e.g., reduction in predation and in bioturbation pressures) and changes in food availability (quality and quantity) mediated by seagrass canopies were the main driving forces structuring this community in an intertidal muddy area of low diversity.

Effects of different light wavelengths on mold growth in tomb

The Second Mausoleum of the Southern Tang Dynasty have a history of more than 1,000 years in China. Since its opening in 1984, the building materials and murals inside the tomb have been severely damaged by mold. Field investigation found that the mold growth on the wall illuminated by the light in the tomb was more flourishing than that in the area without the light. Lighting in the tomb is inevitable for the exhibition. Therefore, the purpose of this study is to clarify the effects of different light wavelengths on the growth of mold in the tomb, and provide the theoretical basis for the lighting design in the tomb chamber. This study is divided into two parts, including in-situ experiment and laboratory experiment. In the in-situ experiment, four kinds of light wavelengths (white, red, blue, and green) were set in the tomb chamber to observe the difference of mold growth on the mural wall. The concentration of phototrophs propagules on different auricular walls was estimated in the laboratory. The results showed that different light sources had different effects on microbial community composition in the tomb site and the red light had better inhibition effect on fungi and actinobacteria.

Effects of Different Particle Sizes of Hydroxyapatite on the Distribution and Migration of Trace Elements (Copper and Cadmium) in a Smelter-Impacted Soil

To study the remediation effect of hydroxyapatite with different particle sizes, a field in situ experiment was carried out by adding conventional hydroxyapatite (0.25 mm) and microhydroxyapatite (3 μm) and nanohydroxyapatite (40 nm) to the contaminated soil and planting Elsholtzia splendens. The distribution and migration of copper (Cu) and cadmium (Cd) in soil were investigated after 4 years. The results show that the application of three different particle sizes of hydroxyapatite significantly raise the soil pH, total phosphorus, and soil organic carbon. Moreover, the addition of hydroxyapatite can reduce the EXC fraction of Cu and Cd by 73.7%–80.1% and 20.8%–35.2%, respectively. In addition, the concentrations of Cu and Cd in >2 mm, 0.25–2 mm, 0.053–0.25 mm, and <0.053 mm aggregate are significantly increased. This improvement indicates that there are risks which may cause the increasing of total Cu and Cd in the soil where the pollution sources still exist. Furthermore, the content of soil colloid is significantly increased, and the colloidal Cu and Cd distribution percentage have been significantly increased by 49.9%–120% and 30.3%–181%. This result illustrates that the application of hydroxyapatite may greatly increase the possibility of colloid and dust migration of Cu and Cd.

Emersion-Associated Responses of an Intertidal Coral and Its Suitability for Transplantation to Ecologically Engineer Seawalls

There is a growing interest in transplanting corals onto the intertidal section of artificial coastal defences (e.g., seawalls) as an ecological engineering strategy to enhance biodiversity on urban shores. However, this inevitably results in exposure to the harsh environmental conditions associated with emersion (aerial exposure). Although the effects of a multitude of environmental stressors on corals have been examined, their photophysiological and gene expression responses to emersion stress remain understudied, as does the among-genotype variation in these responses. In this study, we conducted an in situ experiment to test the effects of increased daily emersion duration on a locally common intertidal coral, Dipsastraea cf. lizardensis. Coral fragments (n = 3) from five genotypically distinct colonies were subjected to two treatments: (1) increased daily emersion duration (~4.5 h d−1) and, (2) control (~3 h d−1) for three consecutive days during spring low tide. We examined the post-experimental photophysiological responses and expression level of a stress-associated gene, Hsp16. Relative to the controls, coral fragments that were exposed to longer daily emersion duration displayed significantly reduced effective quantum yield, while endosymbiont density varied significantly among genotypes across the experimental conditions. We found no significant differences in chlorophyll a concentration and Hsp16 gene expression level, suggesting that changes in these processes may be gradual and the duration of treatment that the corals were subjected to is likely within their tolerance limits. Taken together, it appears that D. cf. lizardensis displays substantial capacity to cope with sup-optimal conditions associated with emersion which makes it a promising candidate for transplantation onto intertidal seawalls. However, within-species variation in their stress response indicates that not all genotypes respond similarly to emersion, and this should be taken into account when selecting donor colonies for transplantation.

Effect of terrigenous sediments on macroalgae functional-form groups of coral reefs in Capurganá, Colombian Caribbean

Increased sedimentation in the marine environment has been described as a key factor in the degradation of coral reefs. One of the most important biological components of coral reefs is macroalgae. The objective of this study was to determine whether the effects of terrigenous sediments on macroalgae affect the current state of the coral reef ecosystem. In an in situ experiment in Capurganá Bay, terrigenous sediments were added to artificial plates and the impact on the recruitment and growth of the macroalgae was examined. In this experiment, three treatments were used: sediment addition and two natural conditions, one up to 10 m distance from the sediment addition (control 1) and one between 15 and 20 m distance from the sediment addition (control 2). The results indicated a high complexity and variability in the response of reef algae to the effects of sedimentation depending on the sediment grade size deposited. The addition had a positive effect on the recruitment and growth of filamentous algae, primarily red algae, whereas it had a negative effect on coralline algae. The sediments found on the plates did not significantly change the macroalgal structure (P>0.05). However, a trend was observed in the change of the algal cover in each treatment. These results indicate that there is a wide range of response of the algae depending on the functional groups and the nature of the sediment.

Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom water conditions, phosphorus release from the sediment is elevated, which further stimulates primary production. It is commonly assumed that re-oxygenation could break this “vicious cycle” by increasing the sedimentary phosphorus retention. Recently, a deep-water inflow into the Baltic Sea created a natural in situ experiment that allowed us to investigate if temporary re-oxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this 3-year study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment, likely due to an increase in organic matter supply to the deeper basins, potentially combined with a transient stimulation of the mineralisation efficiency. As a result, the net sedimentary DIP release per m2 was 56 %–112 % higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.