Mangrove swamp expansion controlled by climate since 1988:a case study in the Nanliu River Estuary,Guangxi,Southwest China

In the Nanliu River Estuary of Guangxi, China, the naturally expanding process of a mangrove swamp（primarily consist of Aegiceras corniculatum） over past decades is studied by satellite images. From 1988 to2013, the area of studied mangrove swamp increased significantly from 60 hm2 to 134 hm2. The expanding process is not gradual and the significant expansion only took place in some special periods. To reveal the dynamic of mangrove swamp expansion, the evolution of tidal flat elevation and the climate change in past decades are studied respectively. The hydrodynamic condition and nutrient supply are also analysed. The study results show that the climate factors of typhoon intensity and annual minimum temperature are crucial for controlling mangrove expansion. A large number of mangrove seedlings on bare tidal flats can survive only in special climate optimum periods, which are continuous years of low typhoon intensity and high annual minimum temperature. In past decades, the scarcity of climate optimum periods resulted in a non-gradual process of mangrove expanding and a time lag of 30 years between the elevation reaching the low threshold for mangrove seedling survival and the eventual emergance of the mangrove. Compared with the climate factors,the hydrodynamic condition and nutrient supply are not important factors affecting mangrove expansion. In the future, combined with global warming, the enhanced frequency and energy of landing typhoons will most likely restrain the further expansion of this mangrove swamp.

Diverse foraging strategies of breeding Swinhoe's Storm-petrel in the productive marginal sea of the Northwest Pacific

Understanding the foraging behavior is essential for investigating seabird ecology and conservation,as well as monitoring the well-being of the marine environment.Breeding seabirds adopt diverse foraging strategies to maximize energy gains and cope with the intensified challenges of parenting and self-maintenance.Such tradeoff may stem from the heterogeneity of food resources and the constraints of central place foraging.Nevertheless,abundant marine productivity could alleviate the energy limitation for seabirds,resulting in a consistent foraging approach.Here,we investigated the foraging strategy during the breeding season of a cryptic small-sized seabird,Swinhoe’s Storm-petrel(Hydrobates monorhis),in the Yellow Sea,a productive marginal sea of the Northwest Pacific.Using GPS tracking,we evaluated habitat preference,quantified the foraging strategy,and tested if environmental conditions and individual traits influence foraging trips.We found that Swinhoe’s Storm-petrels preferred nearshore areas with shallow water and engaged in primarily short foraging trips.Distinctive southeastward and southwestward strategies emerged when combining trip metrics,including foraging direction,duration,and maximum distance.The bathymetry,proximity to the coastline,and sea surface temperature differed in two foraging strategies.Foraging strategies exhibited flexibility between individuals,potentially explained by wing morphology,in which longer-winged birds are more likely to embark on longer-distance foraging trips.These findings highlight the impact of environmental factors and individual traits on seabirds’foraging decisions in productive marginal sea ecosystems.Our study also provides valuable insights into the foraging ecology of this Asian endemic storm-petrel.

Mangroves at the Intersection of Ecological Protection and Targeted Poverty Alleviation

Mangroves are woody trees or shrubs that guard the coastlines and offer shelters for a plethora of living things.They bear the brunt of strong ocean waves and thrive despite twice-daily flooding by ocean tides.However,we have witnessed a vast loss of mangrove forests due to human causes,mainly the need to improve people’s livelihoods.It is becoming increasingly urgent to balance the need for economic development and ecological protection of mangrove forests.After all,it is a shame if our next generation loses the chance to lay eyes upon such beautiful sights.

The reverse sediment transport trend between abandoned Huanghe River(Yellow River) Delta and radial sand ridges along Jiangsu coastline of China——an evidence from grain size analysis

To reveal the sediment transporting mechanism between the abandoned Huanghe River （Yellow River） Delta and radial sand ridges, “End Member” Model and grain size trend analysis have been employed to separate the “dynamic populations” in the surficial sediment particle spectra and to determine the possible sediment transporting pathway. The results reveal four “dynamic subpopulations”（EM1 to EM4） and two reverse sediment transporting directions： a northward transport tend from the radial sand ridges to mud patch, and a southward transport trend in deep water area outside the mud patch. Combined with the published hydrodynamic information, the transporting mechanism of dynamic populations has been discussed, and the main conclusion is that the transporting of finer subpopulations EM1 and EM2 is controlled by the “anticlockwise residual current circulation” forming during tidal cycle, which favor a northward transporting trend and the forming of mud patch on the north of radial sand ridges, while the transporting of coarser EM3 is mainly controlled by wind driven drift in winter, which favors a southward transporting direction.

Long duplication of 18S ribosomal DNA in Cynoglossus lineolatus(Pleuronectiformes： Cynoglossidae)： novel molecular evidencefor unequal crossing over model

Although 18 S r DNA sequence is extremely conservative, the polymorphism still has been found in few species.In the present study, three types(Type A, B and C) of 18 S r DNA sequence coexisted in Cynoglossus lineolatus genome, suggesting a non-concerted evolution process, rather than a strictly concerted evolution fashion.Based on the differences of sequence variation, GC content, secondary structure and minimum free energy,Types A and B were speculated as the potential pseudogenes. Additionally, a fascinating finding was a 189-bp duplication of 18 S r DNA in Type A sequence. To our knowledge, this is the first report on such a long duplication in teleostean ribosomal DNA. Compared with several theories accounting for the formation of tandem repeats, the unequal crossing over model was thought to be the most likely mechanism to generate the189-bp duplication of 18 S r DNA. These results not only provide a novel molecular evidence for the unequal crossing over model, but also benefit for the further study on 18 S r DNA in fishes.

Identification of coastal wetlands of international importance for waterbirds:a review of China Coastal Waterbird Surveys 2005–2013

Background:China's coastal wetlands belong to some of the most threatened ecosystems worldwide.The loss and degradation of these wetlands seriously threaten waterbirds that depend on wetlands.Methods:The China Coastal Waterbird Census was organized by volunteer birdwatchers in China's coastal region.Waterbirds were surveyed synchronously once every month at 14 sites,as well as irregularly at a further 18 sites,between September 2005 and December 2013.Results:A total of 75 species of waterbirds met the 1 % population level Ramsar listing criterion at least once at one site.The number of birds of the following species accounted for over 20 % of the total flyway populations at a single site:Mute Swan(Cygnus olor),Siberia Crane(Grus leucogeranus),Far Eastern Oystercatcher(Haematopus osculans),Bar-tailed Godwit(Limosa lapponica),Spotted Greenshank(Tringa guttifer),Great Knot(Calidris tenuirostris),Spoon-billed Sandpiper(Calidris pygmeus),Saunders' s Gull(Larus saundersi),Relict Gull(Larus relictus),Great Cormorant(Phalacrocorax carbo),Eurasian Spoonbill(Platalea leucorodia),Black-faced Spoonbill(Platalea minor) and Dalmatian Pelican(Pelecanus crispus).A total of 26 sites supported at least one species of which their number met the1 % criterion.Forty-two species met the 1 % criterion in the Yellow River Delta,Shandong;29 at the Cangzhou coast,Hebei and 26 species at the Lianyungang coast,Jiangsu.Conclusions:The results highlight the international importance of China's coastal wetlands for waterbirds.This study also demonstrates that participation of local birdwatchers in waterbird surveys results in data that are invaluable not only for understanding the current status of waterbirds in China's coastal regions but also for waterbird conservation and management.

Effects of temperature and salinity on the asexual reproduction of Aurelia coerulea polyps

Aurelia coerulea polyp is an important stage in the outbreaks of this species.To test the combined effects of salinity and temperature on the survival and asexual reproduction of polyps,we maintained 864 polyps at various salinities(15,25,33,and 40)and temperatures(9,12,15,18,21,and 24℃).Polyps could mostly survive in all treatment combinations except in salinity 15 treatments with low temperatures(9-15℃).Budding occurred at all temperatures(9-24℃),while strobilation only occurred at the low temperatures(9-15℃).The range of 12-15℃was suitable for strobilation and ephyrae release.The optimal range of salinity for asexual reproduction was 25-33.Low(15)or high(40)salinity could significantly reduce the numbers of new buds or ephyrae,and low salinity of 15 retarded and even prevented strobilation at low temperatures.The optimal treatment for budding and strobilation was 21℃-salinity 25 and 12℃-salinity 33,respectively.Salinity had less of an impact than temperature on asexual reproduction,except for the polyps in high or low osmotic pressure conditions.

Polyp-Canal Reconstruction Reveals Evolution Toward Complexity in Corals

Modern scleractinian corals are classified into robust,complex,and basal clades through comparative molecular studies.However,only few morphological or biological criteria can systematically determine the evolutionary trajectories of these major scleractinian coral clades.Here,we obtained the structural information of 21 scleractinian coral species representing robust and complex clades:High-resolution micro-computed tomography was used to reconstruct the polyp-canal systems in their colonies and to visualize the dynamic polyp growth processes.We found that the emergence of mesh-like canals may distinguish representatives of complex and robust clades.The differences in polyp-canal connections suggest distinct evolutionary trajectories among coral species:The formation of the canal network promoted the development of more complex coral structures,and coral polyps within this network formed calices of very similar volume,following precise axial growth directions.The influence of individual polyps on the coral colony becomes less significant as coral structures become more complex,and coral species with more complicated polyp-canal systems occupied niches more efficiently.This work supplements current evolutionary studies on reef-building corals,providing insight for further studies on coral growth patterns.

Aboveground biomass and its spatial distribution pattern of herbaceous marsh vegetation in China

Herbaceous marsh is the most widely distributed type of marsh wetland ecosystem,and has important ecological functions such as water conservation,climate regulation,carbon storage and fixation,and sheltering rare species.The carbon sequestration function of herbaceous marsh plays a key role in slowing climate warming and maintaining regional environmental stability.Vegetation biomass is an important index reflecting the carbon sequestration capacity of wetlands.Investigating the biomass of marsh vegetation can provide a scientific basis for estimating the carbon storage and carbon sequestration capacity of marshes.Based on field survey data of aboveground biomass of herbaceous marsh vegetation and the distribution data set of marsh in China,we analyzed the aboveground biomass and its spatial distribution pattern of herbaceous marsh on a national scale for the first time.The results showed that in China the total area of herbaceous marsh was 9.7×10^(4) km^(2),the average density of aboveground biomass of herbaceous marsh vegetation was 227.5±23.0 g C m-2(95%confidence interval,the same below),and the total aboveground biomass was 22.2±2.2 Tg C(1 Tg=1012 g).The aboveground biomass density of herbaceous marsh vegetation is generally low in Northeast China and the Tibetan Plateau,and high in central North China and coastal regions in China.In different marsh distribution regions of China,the average biomass density of herbaceous marsh vegetation from small to large was as follows:temperate humid and semi-humid marsh region(182.3±49.3 g C m^(-2))<Tibetan Plateau marsh region(243.9±26.6 g C m-2)<temperate arid and semi-arid marsh region(300.5±73.2 g C m-2)<subtropical humid marsh region(348.4±59.0 g C m-2)<coastal marsh region(675.4±73.8 g C m-2). Due to the different area of herbaceous marsh, the total aboveground biomass of herbaceous marsh vegetation in different marsh distribution regions was the largest in the temperate humid and semi-humid marsh region(9.6±2.6 Tg C), and was the smallest in the coastal marsh region(1.1±0.1 Tg C). The spatial distribution of aboveground biomass of herbaceous marsh vegetation in China has obvious non-zonality characteristics, but also presents certain zonality in some regions. The aboveground biomass of herbaceous marsh vegetation in the Tibetan Plateau decreased with the increase of altitude. With the aggravation of drought, the aboveground biomass of herbaceous marsh vegetation in temperate humid and semi-humid regions and temperate arid and semi-arid regions decreased first and then did not obviously change. The aboveground biomass of herbaceous marsh vegetation in temperate humid and semi-humid regions was relatively larger in the regions with higher average annual temperature. The results can provide scientific basis for accurately evaluating the adjustment action of wetland ecosystems on climate, and provide decision support for adaptive management of wetland ecosystems.