Response of marine microalgae,heterotrophic bacteria and their relationship to enhanced UV-B radiation

Ozone depletion in the stratosphere has enhanced solar UV-B radiation reaching the Earth surface and has brought about significant effects to marine ecosystems. The effects of enhanced UV-B radiation on marine microalgae, heterotrophic bacteria and the interaction between them are discussed. The effects on marine microalgae have been proved to occur at molecular, cellular and population levels. Enhanced UV-B radiation increases microalgal flavonoid content but decreases their chlorophyll content and pho-tosynthesis rate; this rachation induces genetic change and results in DNA damage and change of protein content. There have been fewer studies on the effects of UV-B radiation on marine heterotrophic bacteria. Establishment of a nucroalgal ecological dynamic model at population and community levels under UV-B radiation has gradually become a hotspot. The effects of enhanced UV-B radiation on microalgae communities, heterotrophic bacterial populations and interaction between them will become a focus in the near future. This paper will make an overview on the studies concerning the effects of enhanced UV-B radiation on marine microal-gae and heterotrophic bacteria and the interaction between them.     

Effects of different light conditions on repair of UV-B-induced damage in carpospores of Chondrus ocellatus Holm

We evaluated the effects of ultraviolet-B(UV-B) radiation and different light conditions on the repair of UV-B-induced damage in carpospores of C hondrus ocellatus Holm(Rhodophyta) in laboratory experiments. Carpospores were treated daily with different doses of UV-B radiation for 48 days,when vertical branches had formed in all treatments; after each daily treatment,the carpospores were subjected to photosynthetically active radiation(PAR),darkness,red light,or blue light during a 2-h repair stage. Carpospore diameters were measured every 4 days. We measured the growth and cellular contents of cyclobutane pyrimidine dimers(CPDs),chlorophyll a,phycoerythrin,and UV-B-absorbing mycosporine-like amino acids(MAAs) in carpospores on Day 48. Low doses of UV-B radiation(36 and 72 J/m 2) accelerated the growth of C. ocellatus. However,as the amount of UV-B radiation increased,the growth rate decreased and morphological changes occurred. UV-B radiation significant damaged DNA and photosynthetic pigments and induced three kind of MAAs,palythine,asterina-330,and shinorine. PAR conditions were best for repairing UV-B-induced damage. Darkness promoted the activity of the DNA darkrepair mechanism. Red light enhanced phycoerythrin synthesis but inhibited light repair of DNA. Although blue light,increased the activity of DNA photolyase,greatly improving remediation efficiency,the growth and development of C. ocellatus carpospores were slower than in other light treatments.     

Effects of UV-B radiation on tetraspores of Chondrus ocellatus Holm (Rhodophyta), and effects of red and blue light on repair of UV-B-induced damage

We evaluated the effects of red and blue light on the repair of UV-B radiation-induced damage in tetraspores of Chondrus ocellatus Holm. Tetraspores of C. ocellatus were treated with different UV-B radiation levels(0,36,72,108,144 and 180 J/m2),and thereafter subjected to PAR,darkness,or red or blue light during a 2-h repair stage,each day for 48 days. The diameters and cellular contents of cyclobutane pyrimidine dimmers(CPDs),chlorophyll a(Chl a),phycoerythrin,and UV-B-absorbing mycosporinelike amino acids(MAAs) contents of the tetraspores were determined. Our results show that low doses of UV-B radiation(36 and 72 J/m 2) promoted the growth of C. ocellatus; however,increased UV-B radiation gradually reduced the C. ocellatus growth(greater than 72 J/m2). The MAAs(palythine and asterina-330) in C. ocellatus were detected and analyzed by LC/MS. Our results suggest that moderate red light could induce the growth of this alga in aquaculture. In addition,photorepair was inhibited by red light,so there may be some other DNA repair mechanism activated by red light. Blue light promoted the activity of DNA photolyase,greatly improving remediation efficiency. Red and blue lights were found to reduce the capacity of C. ocellatus to form MAAs. Therefore,PAR,red light,and blue light play different roles during the repair processes for damage induced by UV-B radiation.     

Overview on seagrasses and related research in China

Seagrass research in China is still in its infancy. Even though there has been progress recently, there is still a great deal of research needed to gain a better understanding of seagrass. In this article we review and discuss the advances in seagrass research in China from two aspects: (1) seagrass species and their distribution; (2) seagrass research in China, including studies on their taxonomy, ecology, photosynthesis, applications in aquaculture, salt-tolerance mechanisms and other research topics. A total of 18 seagrass species belonging to 8 genera are distributed in nine provinces and regions in China (including Hong Kong and Taiwan), as well as the Xisha and Nansha Archipelagos. They can be divided into two groups: a North China Group and a South China Group. Based on the seagrass distribution, the Chinese mainland coast can be divided into three sections: North China Seagrass Coast, Middle China Seagrass Coast, and South China Seagrass Coast. Ecological studies include research on seagrass communities, nutrient cycling in seagrass ecosystems, genetic diversity, pollution ecology and research in the key regions of Shandong, Guangdong, Guangxi, and Hainan. Seagrass species and their locations, community structure, ecological evaluation, epiphytes, ecological functions and threats in the key regions are also summarized. Other studies have focused on remote sensing of seagrass, threatened seagrass species of China, and pollen morphology of Halophila ovalis.     

Photochemical production of dissolved inorganic carbon from suwannee river humic acid

The photochemical mineralization of dissolved organic carbon(DOC) to dissolved inorganic carbon(DIC) is a key process in carbon cycling.Using a Suntest CPS solar simulator,Suwannee River humic acid(SRHA) was photooxidated to examine the effects of O2 levels,the wavelength of incident light,and the concentration of Fe on the photoproduction of DIC.Increasing the O2 abundance enhanced photodegradation of SRHA.The rate of DIC photoproduction under air saturation in the first 24 h(4.40 μmol/(L h)) was increased...     

Microplastic pollution and enrichment of distinct microbiota in sediment of mangrove in Zhujiang River estuary,China

The microbial communities colonized on microplastics (MPs) have attracted widespread attention. However, few studies focused on the MPs impacts on mangrove ecosystems, particularly on bacterial communities. We investigated the MPs pollution in mangrove of Zhujiang (Pearl) River estuary (ZRE). To study the potential risk posed by MPs to the mangrove ecosystems, the differences in bacterial communities, functions, and complexity between MPs and sediment samples were reported for the first time. Microplastics (2 991±1 586 items/kg dry weight (dw)) in sediment were mainly fibers and polyethylene, mostly transparent, and in size less than 0.5 mm. Bacterial communities and functions significantly differed from MPs in mangrove sediment. Compared with sediment, MPs significantly enriched members of Proteobacteria, Bacteroidetes, and Actinobacteria, as well as the bacteria associated with plastic-degrading and human diseases on their surface, suggesting that microbial communities on MPs may promote MPs degradation and the spread of diseases, posing potential risk to mangrove ecosystems and human health. Although bacteria on MPs exhibited a lower diversity, the co-occurrence network analysis indicated that network of bacteria colonized on MPs was bigger and more complex than those of mangrove sediment, illustrating that MPs can act as a distinct habitat in this special ecosystem. This study provides a new perspective for increasing our understanding of microplastic pollution in mangrove ecosystems.

     

Photobehaviors ofthe calanoid copepod Calanus sinicus from the Yellow Sea to visible and UV-B radiation as a function of wavelength and intensity

The effects of wavelength-specific visible light,white light,and ultraviolet-B(UV-B,280-31 5 nm)on selected behaviors,grazing rate,spawning rate,and hatching rate of the marine copepod Calanus sinicus collected from the Yellow Sea were studied.Calanus s inicus placed in a partitioned experimental sy stem responded positively phototaxis to blue-cyan and yellow light but negatively to orange light and UVB.No obvious dodge activity was found among C.s inicus irradiated with0.005 mW/cm~2 UV-B.Under0.20,0.30 and 0.50 mW/cm~2 UV-B radiation,the lethal half times of individuals were 30.47,2.86,and1.96 h,respectively.Grazing of C.sinicus was restrained at0.10 mW/cm~2 UV-B,whereas yellow-red light stimulated grazing.Egg production rate was highest at a white-light intensity of 1.58 mW/cm~2,with an average rate of 10.04 eggs/(female d).These results are consistent with the observed phenomenon that C.sinicus in the Yellow Sea mostly spa.wn near dawn.Our results indicate that light intensity and spectrum are important factors affecting the diel vertical migration of C.sinicus under natural conditions in the Yellow Sea.     

Advance and application of lake optics research

The mainstreams of lake optics research in recent decades include optical properties of lakewater,observation, transmission and calculation of underwater radiation, determination of absorption coefficient S of yellow substance, influence of UV-B radiation of lake primary productivity by bio-optical model. Major lake optics applications, such as calculation of lake primary productivity and chl-a, analysis of factors restricting eutrophication, and protection against lake eutrophication are summarized.     

Effects of UV-B irradiation on isoforms of antioxidant enzymes and their activities in red alga Grateloupiafilicina （Rhodophyta）

Macroalgae in a littoral zone are inevitably exposed to UV-B irradiance.We analyzed the effects of UV-B on isoenzyme patterns and activities of superoxide dismutase(SOD),peroxidase(POX),catalase(CAT),and ascorbate peroxidase(APX) of red algae Grateloupia filicina(Lamour.) C.Agardh.The activities of SOD,CAT,and APX changed in response to UV-B in a time- and dose-dependent manner.POX activity increased significantly under all three UV-B treatments.The enzymatic assay showed three distinct bands of SODⅠ(Mn-SOD),SODⅡ(Fe-SOD),and SODⅢ(CuZn-SOD) under a low(Luv) and medium(Muv) dose of UV-B irradiation,while SODⅠ and SODⅢ activities decreased significantly when exposed to a high dose of UV-B irradiation(Huv).The activity of POX isoenzymes increased significantly after exposure to UV-B,which is consistent with the total activity.In addition,a clear decrease in activity of CATIV was detected in response to all the three doses of UV treatments.Some bands of APX isoenzyme were also clearly influenced by UV-B irradiation.Correspondingly,the daily growth rate declined under all the three exposure doses,and was especially significant under Muv and Huv treatments.These data suggest that,although the protection mechanisms of antioxidant defense system are partly inducible by UV-B to prevent the damage,G.filicina has incomplete tolerance to higher UV-B irradiation stress.     

Comparative Evaluation on Combined Ecotoxic Effects of Nitrofurazone and NH_4Cl Using Two Ciliated Protists as Model Organisms: Population Dynamics and Growth Rates

Ecotoxic effects of antibiotics or ammonium have been confirmed independently in aquatic animals,but few studies have investigated their combined effects.In aquaculture ecosystems,these pollutants frequently coexist,and often in high concentrations.In this study,the combined effects of antibiotic nitrofurazone and NH4 Cl on the population dynamics and growth rates of two species of ciliated protists,Euplotes vannus and Pseudokeronopsis rubra,were investigated.Profiles of the dose-responses were visualized,and interactions between the two pollutants were quantified by the response surface method(RSM).Results showed that 1)the dynamics of the population growth differed significantly between the testd ciliates and varied with the concentrations of the pollutants;2)the relative growth rate(RGR)of both ciliates decreased significantly with increased pollutant concentrations,while the difference in RGR between the two ciliates was not significant;3)RSM analysis demonstrated an additive effect of nitrofurazone and NH4 Cl on the RGR in both ciliates.In brief,ecotoxic effects can be caused by nitrofurazone and ammonium independently on the two test ciliates,and such effects can be strengthened when they present at the same time.These findings offer a valuable reference for evaluating combined ecotoxic effects caused by multiple pollutants in aquaculture ecosystems.     

Scale issues of wetland classification and mapping using remote sensing images: A case of Honghe National Nature Reserve in Sanjiang Plain,Northeast China

Wetland research has become a hot spot linking multiple disciplines presently. Wetland classification and mapping is the basis for wetland research. It is difficult to generate wetland data sets using traditional methods because of the low accessibility of wetlands, hence remote sensing data have become one of the primary data sources in wetland research. This paper presents a case study conducted at the core area of Honghe National Nature Reserve in the Sanjiang Plain, Northeast China. In this study, three images generated by airship, from Thematic Mapper and from SPOT 5 were selected to produce wetland maps at three different wetland landscape levels. After assessing classification accuracies of the three maps, we compared the different wetland mapping results of 11 plant communities to the airship image, 6 plant ecotypes to the TM image and 9 landscape classifications to the SPOT 5 image. We discussed the different characteristics of the hierarchical ecosystem classifications based on the spatial scales of the different images. The results indicate that spatial scales of remote sensing data have an important link to the hierarchies of wetland plant ecosystems displayed on the wetland landscape maps. The richness of wetland landscape information derived from an image closely relates to its spatial resolution. This study can enrich the ecological classification methods and mapping techniques dealing with the spatial scales of different remote sensing images. With a better understanding of classification accuracies in mapping wetlands by using different scales of remote sensing data, we can make an appropriate approach for dealing with the scale issue of remote sensing images.     

Comparison and effects of different climate-vegetation models in areas of complex terrain under climate change

Identifying the impacts of climate change is important for conservation of ecosystems under climate change, particularly in mountain regions. Holdridge life zone system and K?ppen classification provide two effective methods to assess impacts of climate change on ecosystems, as typical climate-vegetation models. Meanwhile, these previous studies are insufficient to assess the complex terrain as well as there are some uncertainties in results while using the given methods. Analysis of the impacts of the prevailing climate conditions in an area on shifts of ecosystems may reduce uncertainties in projecting climate change. In this study, we used different models to depict changes in ecosystems at 1 km × 1 km resolution in Sichuan Province, China during 1961–2010. The results indicate that changes in climate data during the past 50 years were sufficient to cause shifts in the spatial distribution of ecosystems. The trend of shift was from low temperature ecosystems to high temperature ecosystems. Compared with K?ppen classification, the Holdridge system has better adaptation to assess the impacts of climate change on ecosystems in low elevation(0–1000 m). Moreover, we found that changed areas in ecosystems were easily affected by climate change than unchanged areas by calculating current climate condition.     

Practice and research progress on ecosystem conservation in transboundary areas

Many ecosystems extend across national or political boundaries. The consistent and effective protection of these ecosystems in transboundary areas(ETAs) is an important global research focus. Previous research on the protection of such areas can be categorized into seven themes: 1) ecological conservation of a single ETA; 2) investigation of the effects of a single conservation measure on a specific ETA; 3) determination of species-level effects due to ETA conservation; 4) comparison of the same protection measures between different ETAs; 5) introduction of a single conservation measure to a specific ETA; 6) understanding the relationship between conservation and sustainable development; and 7) generalization across multiple ETA conservation cases. The protection of ETAs involves various considerations, including funding support, demand and will for collaboration, community and public participation, historical and cultural factors, political backgrounds, uniqueness of biological resources, formulation of laws and regulations, founding of specialized administrative departments, non-governmental organizations, and fairness. Here, we briefly explain the research themes and considerations related to ETA conservation. The most important finding is that most major research themes do not focus on the challenges of ETA conservation. We use two nature reserves located between China and North Korea as examples to identify specific ways to improve ETA conservation on Changbai Mountains. The efficiency of ETA administration still remains low. The study of ETA conservation should focus on concrete regional information and aim to improve existing measures through the accumulation of experience.     

Study on wetland biodiversity in China

Wetland biodiversity means mainly the types of wetland ecosystem and biological species diversity. Biodiversity includes all species of plants, animals and microbes, all gene possessed by them and all ecosystems consisting of them and environment. According to the origin and genesis, China’s wetlands can be divided into natural wetland ecosystems including mires, lakeshores, bottomland, seashore, wet meadow, etc., and artificial wetland ecosystem including paddy field. Then based on geomorphological type, these ecosystems can be divided into 15 subsystems, then based on soil substrata and ecological niche conditions, they can be subdivided into 15 classes, finally according to construction species of plants, several types can be divided into. They are not only the expression of ecosystem diversity, but also the base for biological communities subsistence. This peculiar ecological niche provides a complex and perfect special habitat for various animal and plant communities. In this special habitat, there exist various biological types from monomolecular microbes to higher plants and animals, especially some endangered and rare plants and animals. According to the statistics, there are more than 300 species of birds in China wetlands, making up one-third of the total number of China’s birds. Wetlands not only good place for waterbirds living, but also the important environment on which wild animals and plant rely for existence. There are 65 species of mammals, 50 species of reptiles, 45 species of amphibious animals, 1040 species of fish, 825 species of higher plants, 639 species of angiosperm, 10 species of gymnosperm, 12 species of pteridophyte and 164 species of bryophyte investigated in China’s wetlands.     

Comparison of Two Methods to Assess the Size Structure of Phytoplankton Community Assemblages,in Liaodong Bay,China

Liaodong Bay is one of the largest semi-enclosed bays located in Bohai Sea, in northeast China. It is an important feeding and spawning place, even wintering and breeding migration base for many marine organisms. The size structure of phytoplankton communities is a key feature of marine ecosystems and can be used as an indicator for algae disaster, but the methods to evalute is still challenging. Here, we compared the size-fractionated chlorophyll-a method with a high-throughout sequencing method in an evaluation of the size structure of phytoplankton assemblages in Liaodong Bay, China, in 2014. The proportion of picophytoplankton was estimated at just 19% according to the results based on size-fractionated chlorophyll-a, which likely represents a severe underestimation. The sequencing method confirmed that many kinds of phytoplankton species appeared in more than one size-fractionated filter membrane, with some even dominating where the filter membrane pore size was greater than the individual phytoplankton size. According to the sequencing method, the phytoplankton assemblages in Liaodong Bay were dominated by picophytoplankton(average proportion = 44%), followed by the nanophytoplankton(average 32%), a composition that is more consistent with other studies. The sequencing method provides a more robust way to assess the size structure and taxonomic diversity of marine phytoplankton communities.     

Archaeal community structure in sediments from a seamount in the Mariana Volcanic Arc

Seamounts are subsurface mountains in the ocean.Examination of the abundance and distribution of Archaea in seamount ecosystems may provide a better understanding of their ecological functions.Most studies of marine archaeal assemblages in seamount area have focused on hydrothermal vents or ferromanganese crusts.We investigated the archaeal communities from a seamount of the Mariana Volcanic Arc,in the tropical western Pacific Ocean by using high-throughput sequencing.Thaumarchaeota was dominant in the sediments of all sample stations.Community diversity and species richness were greatest at stations near the top of the seamount,and lowest at the deepest station.One sample station on the steep southeast slope that faced the Yap-Mariana trench had a unique composition of Archaea.In summary,depth has an important influence on archaeal community structure,and the geographic properties and sediment characteristics may explain the unique distribution patterns of Archaea in this seamount.This study provides a foundation for future research on Archaea in seamounts.     

Observations and modeling of incoming longwave radiation to snow beneath forest canopies in the west Tianshan Mountains,China

Forest canopy reduces shortwave radiation and increases the incoming longwave radiation to snowpacks beneath forest canopies. Furthermore, the effect of forest canopy may be changed by complex topography. In this paper, we measured and simulated the incoming longwave radiation to snow beneath forest at different canopy openness in the west Tianshan Mountains, China(43°16'N, 84°24'E) during spring 2013. A sensitivity study was conducted to explore the way that terrain influenced the incoming longwave radiation to snow beneath forest canopies. In the simulation model, measurement datasets, including air temperature, incoming shortwave radiation above canopy, and longwave radiation enhanced by adjacent terrain, were applied to calculate the incoming longwave radiation to snow beneath forest canopy. The simulation results were consistent with the measurements on hourly scale and daily scale. The effect of longwave radiation enhanced by terrain was important than that of shortwave radiation above forest canopy with different openness except the 20% canopy openness. The longwave radiation enhanced due to adjacent terrain increases with the slope increase and temperature rise. When air temperature(or slope) is relatively low, thelongwave radiation enhanced by adjacent terrain is not sensitive to slope(or air temperature), but the sensitivity increases with the decrease of snow cover area on sunny slope. The effect of longwave radiation is especially sensitive when the snow cover on sunny slope melts completely. The effect of incoming shortwave radiation reflected by adjacent terrain on incoming longwave radiation to snow beneath forest canopies is more slight than that of the enhanced longwave radiation.     

Microbial ecological associations in the surface sediments of Bohai Strait

Microbial communities play key roles in the marine ecosystem. Despite a few studies on marine microbial communities in deep straits, ecological associations among microbial communities in the sediments of shallow straits have not been fully investigated. The Bohai Strait in northern China(average depth less than 20 m) separates the Bohai Sea from the Yellow Sea and has organic-rich sediments. In this study, in the summer of 2014, six stations across the strait were selected to explore the taxonomic composition of microbial communities and their ecological associations. The four most abundant classes were Gammaproteobacteria, Deltaproteobacteria, Bacilli and Flavobacteriia. Temperature, total carbon, depth, nitrate, fishery breeding and cold water masses influenced the microbial communities, as suggested by representational dif ference and composition analyses. Network analysis of microbial associations revealed that key families included Flavobacteriaceae, Pirellulaceae and Piscirickettsiaceae. Our findings suggest that the families with high phylogenetic diversity are key populations in the microbial association network that ensure the stability of microbial ecosystems. Our study contributes to a better understanding of microbial ecology in complex hydrological environments.     

Stabilization versus decomposition in alpine ecosystems of the Northwestern Caucasus: The results of a tea bag burial experiment

Mountainous areas exhibit highly variable decomposition rates as a result of strong local differences in climate and vegetation type. This paper describes the effect of these factors on two major determinants of the local carbon cycle: litter decomposition and carbon stabilization. In order to adequately reflect local heterogeneity, we have sampled 12 typical plant communities of the Russian Caucasus. In order to minimize confounding effects and encourage comparative studies, we have adapted the widely used tea bag index (TBI) that is typically used in areas with low decomposition. By incubating standardized tea litter for a year, we investigated whether (1) initial litter decomposition rate (k) is negatively correlated with litter stabilization (S) and (2) whether k or S exhibit correlations with altitude and other environmental conditions. Our results show that S and k are not correlated. Altitude, pH, and water content significantly influenced the stabilization factor S, while soil-freezing had no influence. In contrast, none of these factors predicted the decomposition rate k. Based on our data, we argue that collection of decomposition rates alone, as is now common practice, is not sufficient to understand carbon input to soils and can potentially lead to misleading results. Our data on community-specific decomposition and stabilization rates further constrain estimates of litter accumulation in subalpine communities and the potential effects of climate change.     

Plant diversity as a good indicator of vegetation stability in a typical plateau wetland

Biotic indicators have been widely used to monitor wetland health. However, few studies have explicitly evaluated if plant diversity could serve as a useful community-level indicator of wetland stability, especially when wetlands are confronted with anthropogenic perturbations. Based on three-year record of wetland plant species abundance in Napahai plateau wetland, Shangri-la under the influence of varying anthropogenic perturbation types, our study tests the impact of such perturbations on plant richness and the relationship between ecosystem temporal stability and plant richness, and further assesses the effectiveness of using plant diversity indicator to probe ecosystem temporal stability of Napahai plateau wetland and the potential mechanisms. The results showed that anthropogenic perturbations could have contributed significantly to realistic variation in plant diversity, and further demonstrated that ecosystem temporal stability was positively related to realistic variation in plant diversity. In particular, communities with high levels of diversity might have better capacity to dampen perturbation impacts than communities with low levels of diversity, and statistical averaging could have played an important role in causing greater stability in more diverse communities. Also, asynchrony might have a stabilizing effect on community stability, and diversity could have stabilized communities through both species asynchrony and population stability propagation. Therefore, our results suggest that plant diversity could be used as a useful indicator of the stability conditions of plateau wetland ecosystems confronted with anthropogenic perturbations, and the preservation of plant communities at sufficient abundance and diversity is necessary for maintaining healthy plateau wetlands and for sustaining their essential ecosystem functions and services.