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Anaerobic ammonium oxidation (anammox) plays an important role in nitrogen removal in coastal seas, and ladderanes, as specific biomarkers of anammox bacteria, can be used to indicate the anammox activity. However, the origins of ladderanes and their controlling factors in the coastal seas influenced by anthropogenic activities are still not well constrained. To address this, we reported ladderanes, long-chain n-alkanols (terrestrial biomarker) and sterols (marine biomarker) in suspended particulates from the estuaries and inner area of Laizhou Bay in North China, to study ladderane sources and its distribution patterns. This study proposed a novel index, Rlad, using ladderane ratio of ladderane III to ladderane IV, and by correlating this index with other biomarker distributions to evaluate the source of ladderanes. High Rlad values (> 0.9) indicated biosynthesis by terrestrial anammox bacteria Ca. Brocadia and Ca. Kuenenia, while low Rlad values (< 0.9) indicated biosynthesis by marine anammox bacteria Ca. Scalindua. High Rlad values and high ladderane concentrations in particulates from the estuaries and nearshore area of Laizhou Bay revealed sources from the terrestrial input via riverine inflow as well as in situ production in oxygen-depleted estuaries, supported by high concentrations of terrestrial biomarkers; Low Rlad values and low ladderane concentrations in particulates from offshore area indicated sources from marine environment via the cold hypoxia water input by the Bohai circulation. Comparison of ladderane concentrations of our study with previously published results from a wide range of environments with human influences from Chinese coastal area revealed that high ladderane concentrations synthesized by terrestrial anammox bacteria could contribute significantly to coastal seas, and the anammox process in river-estuary-bay system might be underestimated. This study provides new understandings about the evaluation of the source and distribution of ladderanes under anthropogenic influences in coastal seas.

Mass coral bleaching is a severe threat to coral reefs in the era of global warming, and upwelling areas may serve as thermal refugia for coral reefs by mitigating the effects of heating anomalies. This study seeks to examine the impact of the Qiongdong upwelling (QDU) on the coastal coral reefs of the Hainan Island. The environmental variables (i.e., physiochemical parameters, coastal land use) differed significantly in upwelling and non-upwelling areas. In particular, the presence of colder and more saline water was the important indicator of coastal upwelling. In the QDU, turf algae and macroalgae dominated the algae communities, but habitat-specific environment and coastal development contributed to lower calcified algae, coral larvae replenishment and live corals cover. Lower abundance of coral reefs fishes could be attributed to the disappearance of live corals, increase of algae coverage, low habitat complexity and strong wave exposure at upwelling stations. Upwelling-related environmental parameters, wave exposure, land use and potential local stressors were revealed as major driving factors related to significant spatial changes in stony coral and fish communities. Overall, the present findings suggest that the Qiongdong upwelling has the potential to provide thermal refuge for coral reefs, but is severely affected by local anthropogenic activities.

The spatial and seasonal distributions of stable carbon and nitrogen isotopes (δ13C and δ15N) in dominant zooplankton groups were investigated in Jiaozhou Bay. Zooplankton δ13C values ranged from −22.89‰ to −15.86‰, and δ15N values ranged from 3.18‰ to 13.57‰, respectively. The δ13C and δ15N values generally followed the order of small zooplankton < large calanoids < small Sagitta < large Sagitta. Spatial distribution patterns of zooplankton δ13C and δ15N values varied in different seasons. Our results suggested that the spatial variation of δ13C was mainly controlled by terrigenous organic matter (OM) input and phytoplankton biomass, but water temperature may have played a key role in the seasonal variation of δ13C. In spring, the high phytoplankton biomass might increase the δ13C value of small zooplankton in the inner bay. During other seasons, the δ13C values of zooplankton generally increased from the inner bay to the outer bay, which might be associated with the influence of 13C-depleted terrigenous OM carried by the river discharge. Small zooplankton stable isotope values were significantly correlated with that of particulate organic matter (POM). The influence of anthropogenic nutrient input on isotopic baseline can be cascaded to the zooplankton, and the effect might be weak at higher trophic levels. The Bayesian standard ellipse areas of dominant zooplankton groups were generally smallest in the winter, suggesting a narrow niche width during that time. The niche partition between small zooplankton, large calanoids, and Sagitta was most distinct in winter, and followed by summer. The relative trophic level of Sagitta ranged from 2.23 to 4.01, which generally declined from the inner bay to the outer bay during the spring, autumn, and winter seasons. High anthropogenic nutrient loading might reduce the difference in trophic niches among zooplankton groups. This study provided detailed information on the distribution of zooplankton δ13C and δ15N in a coastal bay, which will be useful for understanding the anthropogenic influence on the ecosystem structure and function.

The 2011 Great East Japan Earthquake and tsunami wiped out over 1200 shellfish and ascidian culture long-lines and ∼120 salmon farm cages that comprised the entire aquaculture installations in Onagawa Bay, Japan, and severely altered the associated ecosystem. A year later, we launched a coordinated monitoring program to measure the extent of the damage caused by the disaster and monitor the change in the state of the marine ecosystem. As part of this effort, we conducted multi-seasonal sampling to characterize spatio-temporal variation in benthic macrofaunal community and a range of environmental parameters across Onagawa Bay between March 2012 and January 2018. The 492 total macrofaunal species recorded included Polychaeta (38.8%), Bivalvia (13.2%), Amphipoda (10.8%), Decapoda (9.6%), Gastropoda (9.3%), and Echinodermata (4.3%). At the outermost reference site, macrofaunal abundance, biomass, and species diversity were all consistently high throughout the study period. Inside Onagawa Bay, macrofauna metrics increased steadily from the lowest values at the beginning of the study to the highest over time. During the same period, the spatial extent of aquaculture facilities for long-lines and fish cages recovered steadily to within 60.8% and 74.8% of the original state, respectively. The significant variables identified by multivariate analysis to explain spatio-temporal variability in benthic macrofaunal communities were: (1) proximity to the nearest aquaculture facilities; (2) wind fetch length (exposure); (3) sediment grain size; and (4) the total area of aquaculture facilities. This study suggests that coastal aquaculture operations may strongly influence the occurrence and distribution of benthic macrofaunal communities and thereby influence the recovery of seafloor biota at ecosystem scales following a catastrophic natural disaster.