Illumina Sequencing of 16S rRNA Tag Revealed Spatial Variations of Bacterial Communities in a Mangrove Wetland

The microbial community plays an essential role in the high productivity in mangrove wetlands. A proper understanding of the spatial variations of microbial communities will provide clues about the underline mechanisms that structure microbial groups and the isolation of bacterial strains of interest. In the present study, the diversity and composition of the bacterial community in sediments collected from four locations, namely mudflat, edge, bulk, and rhizosphere, within the Mai Po Ramsar Wetland in Hong Kong, SAR, China were compared using the barcoded Illumina paired-end sequencing technique. Rarefaction results showed that the bulk sediment inside the mature mangrove forest had the highest bacterial α-diversity, while the mudflat sediment without vegetation had the lowest. The comparison of β-diversity using principal component analysis and principal coordinate analysis with UniFrac metrics both showed that the spatial effects on bacterial communities were significant. All sediment samples could be clustered into two major groups, inner (bulk and rhizosphere sediments collected inside the mangrove forest) and outer mangrove sediments (the sediments collected at the mudflat and the edge of the mangrove forest). With the linear discriminate analysis scores larger than 3, four phyla, namely Actinobacteria, Acidobacteria, Nitrospirae, and Verrucomicrobia, were enriched in the nutrient-rich inner mangrove sediments, while abundances of Proteobacteria and Deferribacterias were higher in outer mangrove sediments. The rhizosphere effect of mangrove plants was also significant, which had a lower α-diversity, a higher amount of Nitrospirae, and a lower abundance of Proteobacteria than the bulk sediment nearby.     

Lack of correlation between surface macrofauna,meiofauna, erosion threshold and biogeochemical properties of sediments within an intertidal mudflat and mangrove forest

This article describes the relationship between 10 selected properties of the sediments (chlorophyll a and b, colloidal and total carbohydrate, water concentration, sediment type, organic matter, erosion threshold and erosion rate) and meio- and macrofauna within and among three different habitats in an urbanized intertidal mudflat/mangrove forest in Tambourine Bay, Sydney Harbour, Australia. Many of the biogeochemical variables were significantly different among habitats, often grading from mudflat to mangrove canopy. In contrast to previous studies, patterns of distribution of macrofauna among habitats were weak. For the meiofauna, only copepods showed any significant difference among habitats, with the greatest numbers in the open mudflat habitat and least under the mangrove canopy. There was a gradient in fauna among the habitats; overall macrofauna abundances were greatest under the mangrove canopy and least on the mudflat, while meiofauna abundance was greatest in the pneumatophore habitat and least under the canopy. Correlations between fauna and properties of sediment were generally weak. When the habitats were analysed separately, some correlations were strengthened but relationships were inconsistent. Thus, while some taxa vary significantly among habitats there was not a strong relationship between biogeochemical properties and either macro- or meiofauna. This suggests that localised factors other than the measured properties of the sediments are driving patterns in fauna at these small scales, which requires further investigation to be unravelled.     

福建漳江口红树林湿地沉积物中四种重金属的空间分布特征

对漳江口红树林湿地沉积物中4种重金属(Pb、Cd、Ni、Fe)含量空间分布的研究表明,漳江口红树林湿地沉积物中Pb、Fe含量较高,Cd、Ni含量相对较低;林内沉积物的Pb、Cd含量显著高于林外沉积物;在垂岸方向上,表层沉积物中除Ni外其它三种元素含量均表现出从林外到林内增加的趋势;在垂直梯度上,四种元素含量均随着沉积物深度增加而逐渐降低。     

Weak diurnal changes in the biochemical properties and benthic macrofauna of urbanised mangrove forests and mudflats

Diurnal changes in the biochemical properties and the benthic macrofaunal assemblage of sediments in urbanised mangrove forests and their adjacent mudflats in Sydney Harbour were investigated. Behavioural and physiological changes in the microphytobenthos between day and night were predicted to cause diurnal changes in the micro-scale depth distribution of chlorophylls a and b and colloidal carbohydrate. In addition, because macrofauna can alter sediment properties, diurnal changes in the macrofaunal assemblages were investigated. The microphytobenthos at the study sites were predominantly filamentous green algae, although diatoms were present. Samples for biochemical analysis were collected from the top 2 mm of sediment using mini-cryolanders, during low tide in the day and at night. Three biochemical properties of the sediments were measured spectrophotometrically: chlorophylls a and b (surrogate for microphytobenthos biomass) and colloidal carbohydrate. The amount of chlorophylls tended to be less at night than during the day, but site to site variability was large and these differences were generally small and not significant. Depth profiles indicated that there was some redistribution of pigments in the surface 2 mm between day and night, possibly due to migration of microphytobenthos or physiological changes. There was no significant difference in chlorophylls between the mangrove forest and adjacent mudflat, with the exception of chlorophyll b at one sampling time, which was larger in the mangrove forest than on the mudflat. Colloidal carbohydrate was significantly larger in the mangrove forest and significantly less on the mudflat during the day at one site at one time, but otherwise showed no significant differences between day and night or between the mangrove forest and mudflat. Whilst there were some differences in the benthic macrofaunal assemblages between day and night, these differences were only significant for spionids and polychaetes at one time. There were, however, significant differences in assemblages of benthic macrofauna between the mangrove forest and mudflat, probably due to structural differences between these habitats such as the presence of pneumatophores, shade and leaf litter. In summary, there was some minor diurnal variation in the measured biochemical properties of the sediment, but not in the macrofaunal assemblage. Diurnal changes should, therefore, be considered when investigating biochemical properties in these habitats, but they are not a major influence. These findings contrast to previous studies on diatom dominated mudflats in Europe, where stronger diurnal changes in biochemical properties were found. Diurnal changes in the macrofauna assemblages were largely insignificant and therefore could not explain the changes in the biochemical properties. Diurnal effects on the macrofauna in these habitats are more likely to be via altered behaviours and this requires further investigation.     

Spatial and temporal variability in benthic processes along a mangrove-seagrass transect near the Bangrong Mangrove,Thailand

Benthic primary production and nutrient dynamics were examined along a transect in the Bangrong mangrove forest in Thailand. Six stations were established extending from a high-intertidal site within the mangrove forest to low-intertidal flats and seagrass beds in front of the mangrove forest. Benthic processes (O₂ and CO₂ fluxes) and nutrient dynamics (mineralization, sediment-water fluxes, pore water and sediment pools) were measured under light and dark conditions during wet and dry seasons over a 2-yr period. The sediments were mostly autotrophic, only the mangrove forest sites were net heterotrophic during the wet season. Maximum daily net primary production was found at the non-vegetated tidal flats (40–75 mmol O₂ m^-2d^-1), where light and nutrient availability were highest. The variation in benthic mineralization along the transect was minor (1.6–4.3 mmol CO₂ m^-2h^-1) and did not reflect the large changes inorganic matter content (organic carbon: 0.7–4.2% DW) and quality (C:N ratio varied from 25 to 100), suggesting that the mineralizable pool of organic matter was of similar magnitude at all sites. There was only minor seasonal variation in rates of mineralization. The net primary production showed more variation with lower rates in the mangrove forest (reduced with 74%) and higher rates at the tidal flats (increased with 172%) and in the seagrass beds (increased with 228%) during the wet season. The nutrient pools and fluxes across the sediment-water interface were generally low along the transect, and the sediments were efficient in retaining nitrogen in the nutrient limited mangrove/seagrass environment. Pools and fluxes of phosphorus were generally very low suggesting that benthic primary production was phosphorus limited along the transect. This revised version was published online in July 2006 with corrections to the Cover Date.     

福建洛阳河口潮间带大型底栖甲壳动物群落及其功能群研究

2013年8月、2013年10月、2014年1月和2014年4月分别在洛阳河口潮间带选取5种生境(红树林区Q1,Q2,Q3;光滩Q4,林缘光滩Q5)开展调查,以探讨不同生境间甲壳动物群落结构及功能群差异和影响因素。调查共获得甲壳动物18科35种,优势种和重要种有弧边招潮(Uca arcuata)、薄片蜾蠃蜚(Sinocorophium lamellatum)、宁波泥蟹(Ilyoplax ningpoensis)和秀丽长方蟹(Metaplax elegans),以穴居型植食者为主;不同生境间优势种存在明显变化,游泳型甲壳动物主要出现在生境Q1、Q2和Q3。洛阳江红树林生境Q1、Q2、Q3底栖甲壳动物物种多样性和功能群复杂性高于林缘光滩和光滩生境,而生物量和栖息密度则相反。通过对5种不同生境的物种数、生物量、密度、功能群、物种多样性指数进行生境-季节间双因素方差分析发现,不同生境间与季节间甲壳动物物种数、栖息密度、功能群、均匀度指数与多样性指数存在显著差异;生物量在生境间差异不显著,丰富度指数在季节间差异不显著;生境Q1、Q2和Q3差异不显著。而底栖甲壳动物群落相似性和非度量多维度标序(n MDS)分析表明林缘光滩Q5的甲壳动物群落结构与Q1、Q2、Q3的相似度高,与光滩生境相似度较低,这可能是因为红树林、林缘光滩、光滩三者生境的复杂程度、食物丰富程度和食物来源存在差异有关。综合分析表明生境复杂程度与季节是影响洛阳河口潮间带大型底栖甲壳动物分布的主要因素。     

Restoration of Shorebird‐Roosting Mudflats by Partial Removal of Estuarine Mangroves in Northern Taiwan

Expansion of the monospecific mangrove, Kandelia obovata, has converted intertidal mudflats and other habitats into mangrove forests, thus reducing estuarine biodiversity in the Danshuei River estuary, northern Taiwan. Dense mangrove vegetation was removed to create a small patchwork of mudflats and a tidal creek in February 2007. Subsequent changes in sediment properties and biodiversity of the macrobenthos and avian communities were examined. The results showed that the creation of different habitats led to changes in sediment properties and biodiversity. The water content and sorting degree of the sediments differed significantly among the restored mudflat, the tidal creek, and the mangrove control site. Silt/clay, organic carbon content, and chlorophyll a concentrations varied seasonally, but not among sites. The abundance of polychaetes in the creek was greater than that in the mudflat or the mangrove (12.5 vs. 5.3 and 2.2 individuals/m², respectively), suggesting preferential colonization of infaunal polychaetes in habitats with prolonged submersion. Crabs showed seasonal changes in density, with higher densities in summer than in autumn and winter. The species richness of wintering shorebirds on the created mudflat increased dramatically from 2002 to 2007. The transformation of a vegetated area into an open mudflat appeared to benefit shorebirds by providing roosting habitat. Our study demonstrated that controlling the spread of estuarine mangrove forests could increase biodiversity, and could particularly benefit the migratory shorebird community.     

Diversity and abundance of molluscs in Thalassia testudinum prairie of the Bay of Mochinma, Mochima National Park, Venezuela

The diversity and abundance of benthic malacological communities associated to Thalassia testudinum beds was studied at four localities of Mochima Bay, Sucre state, Venezuela. At each locality, samples were taken monthly on perpendicular transect at different depths (0-4 m), from January 1991 to December 1991, using a quadrate (0.25 m2) for collecting mollusks and sediments. A total of 2,988 organisms of infauna and epifauna belonging to 81 species of the classes Gastropoda (41) and Bivalvia (40) were collected. More abundant species were Anadara notabilis, Codakia orbicularis, Cerithium litteratum, Cerithium eburneum, Batillaria minima, Modiolus squamosus, Modulus modulus, Chione cancellata, Turritella variegata, Arca zebra, y Laevicardium laevigatum. There were significant differences in number of organisms between depth and month at La Gabarra which presented the highest value of total (4.51 bits/ind) and monthly diversity (2.71-3.90 bits/ind). Biomass and abundance were low in the Mochima Bay while Varadero station presented the highest value. The bivalve A. notabilis and gastropod M. modulus were species common to the four stations.     

粤东沿海红树林物种组成与群落特征

南海地区是全球红树林分布的中心区域之一。粤东沿海位于南海地区的北界,红树林物种组成和群落结构具有边缘性。利用卫星影像解译辅助技术,对筛选的23处红树林群落进行样地调查,记录了真红树植物12种,半红树植物6种,伴生植物7种。各群落平均高度为1.50—8.60 m,林相以灌丛、小乔木林为主。红树林群落Shannon-Wiener多样性指数为0.533—1.239,均匀度指数为0.662—0.957,天然林和人工林之间数值差异不显著。等级聚类分析将粤东沿海的红树林划分为演替早期人工林、演替早期天然林、演替中期天然林和演替后期天然林4个类别,各群落立地条件差异较大,沉积物总有机碳、盐度、总氮含量与群落分布状况的相关性较高。与1985年的报道相比,尽管该地区记录的红树林植物种类从20种增加至24种,但个别伴生植物消失以及半红树植物种群萎缩说明该地区红树林面临较大的环境压力。在物种多样性和均匀度均方面,粤东沿海红树林群落低于成熟红树林。过去数十年的围垦导致天然红树植物种群萎缩、生境破碎化是主要因素。基于该地区红树林群落的现状,未来人工林和残次天然林的优化改造是红树林恢复重建的重点,红树林恢复和保育的重点区域包括深圳湾的福田、范和港的蟹洲和韩江口的六合围。     

Site-to-site variability in abundance of meiobenthic copepods along a tidal gradient over 24 hours

As part of a larger study on the effects of juvenile fish predation on meiobenthic copepods, we collected meiofauna every two hours for 24 hours at three muddy sites along a transect through vegetated marsh, to unvegetated intertidal to unvegetated subtidal habitats. The vegetated marsh (Spartina alterniflora) site harbored significantly more copepods over the combined sampling period than the other two sites. Some species were distributed along the entire transect, but several species were much more abundant at one site than the others. For example, Microarthridion littorale was most abundant at the intertidal site, and Enhydrosoma propinquum was most abundant at the unvegetated sites. The most abundant subtidal species included Pseudobradya pulchella and Paronychocamptus wilsoni. Three species were most abundant in the vegetated marsh (Stenhelia (D.) bifidia, Nannopus palustris, and Diarthrodes aegidius). Maximum total copepod abundance occurred during the daytime low tide at all three sites. Of the four species more abundant in the light than at night, three were subtidal. Most of the time there were no detectable differences between high and low tide abundances, suggesting that there was little exchange of individuals between habitats as tidal levels changed. Without samples from additional transects or the ability to obtain samples for all possible combinations of light and tide levels, we could not detect significant interactions between these two environmental factors. Based upon the species composition of copepods in the gut contents of motile fish predators, the existence of distinct copepod species assemblages at sites along the transect may allow inferences about where fish had fed.Contribution No. 695 from the Bell W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina.     

Macrobenthic infauna of mangroves and surrounding beaches at Gazi Bay,Kenya

Twelve sites around Gazi Bay, Kenya, were examined for macrobenthic infauna. Stations differed in human disturbance, vegetation, and sediment type (sandflat, beach, denuded and virgin mangrove sites, with Sonneratia, Rhizophora, Avicennia, Ceriops or Bruguiera vegetation).Sixteen higher taxa were counted; Isopoda, Amphipoda, Polychaeta, Cumacea and Tanaidacea were determined to family level (sometimes to genus or species). Total densities of infauna ranged from 265 to 6025 ind m^–2.Gazi mangals had higher macrobenthos densities than other mangrove sediments described in literature and than the Gazi sandflats. The densities found in Gazi sandflats were comparable to similar habitats elsewhere.Virgin mangrove sediments were rich in mud and organic material, and were characterized by high densities of macro-Oligochaeta and Mollusca. Sandflats, beaches, exploited (denuded) and less dense mangroves or mangroves higher in the tidal zone (Bruguiera) were much more sandy and had a high abundance of Polychaeta and Nemertini.Structural patterns in the macrobenthos were only vaguely associated with vegetation type. Human impact (cutting) has resulted in a drastic decrease in densities of macro-infauna, possibly related to a reduction of organic material in the sediment.     

Variation in fish density,assemblage composition and relative rates of predation among mangrove,seagrass and coral reef habitats

We tested the hypothesis for several Caribbean reef fish species that there is no difference in nursery function among mangrove, seagrass and shallow reef habitat as measured by: (a) patterns of juvenile and adult density, (b) assemblage composition, and (c) relative predation rates. Results indicated that although some mangrove and seagrass sites showed characteristics of nursery habitats, this pattern was weak. While almost half of our mangrove and seagrass sites appeared to hold higher proportions of juvenile fish (all species pooled) than did reef sites, this pattern was significant in only two cases. In addition, only four of the six most abundant and commercially important species (Haemulon flavolineatum, Haemulon sciurus, Lutjanus apodus, Lutjanus mahogoni, Scarus iserti, and Sparisoma aurofrenatum) showed patterns of higher proportions of juvenile fish in mangrove and/or seagrass habitat(s) relative to coral reefs, and were limited to four of nine sites. Faunal similarity between reef and either mangrove or seagrass habitats was low, suggesting little, if any exchange between them. Finally, although relative risk of predation was lower in mangrove/seagrass than in reef habitats, variance in rates was substantial suggesting that not all mangrove/seagrass habitats function equivalently. Specifically, relative risk varied between morning and afternoon, and between sites of similar habitat, yet varied little, in some cases, between habitats (mangrove/seagrass vs. coral reefs). Consequently, our results caution against generalizations that all mangrove and seagrass habitats have nursery function.     

Size structure and distribution of Ovassiminea brevicula (Gastropoda) in a Thai mangrove swamp

Ovassiminea brevicula (Pfeiffer) (Assimineidae: Gastropoda) was oneof the most abundant and representative benthic invertebrates in the SamutSongkhram mangrove swamp, Thailand. It lived mainly in the mangrove forest with high average densities ranging from 44 to 340 snails·m^-2and abundant in the sites where much litter, dead branches and seedlingswere present. Average shell length in the mature forest ranged from 4.73to 5.74 mm (range: 2.26–8.30 mm) and size structures showeddifferent patterns among the stations. In the seaward mudflat, O. breviculaappeared immediately after the saplings of Avicennia alba Blume1826 were planted. Thereafter, its densities increased with the growth of A. alba trees, probably due to provision of favourable microhabitats underthe canopies. In the mudflat with only small saplings and outside the canopyof the young forest 2 years after planting, mean shell lengths were 3.45 and3.19 mm respectively. Under the canopy of the young forest, however,mean shell length was 4.34 mm with a few larger snails. Three cohortswere separated for snail populations in the mature forest and larval recruitmentseemed to occur from February to May.     

Spatial distribution and abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in mangrove sediments

We investigated the diversity, spatial distribution, and abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in sediment samples of different depths collected from a transect with different distances to mangrove forest in the territories of Hong Kong. Both the archaeal and bacterial amoA genes (encoding ammonia monooxygenase subunit A) from all samples supported distinct phylogenetic groups, indicating the presences of niche-specific AOA and AOB in mangrove sediments. The higher AOB abundances than AOA in mangrove sediments, especially in the vicinity of the mangrove trees, might indicate the more important role of AOB on nitrification. The spatial distribution showed that AOA had higher diversity and abundance in the surface layer sediments near the mangrove trees (0 and 10 m) but lower away from the mangrove trees (1,000 m), and communities of AOA could be clustered into surface and bottom sediment layer groups. In contrast, AOB showed a reverse distributed pattern, and its communities were grouped by the distances between sites and mangrove trees, indicating mangrove trees might have different influences on AOA and AOB community structures. Furthermore, the strong correlations among archaeal and bacterial amoA gene abundances and their ratio with NH₄⁺, salinity, and pH of sediments indicated that these environmental factors have strong influences on AOA and AOB distributions in mangrove sediments. In addition, AOA diversity and abundances were significantly correlated with hzo gene abundances, which encodes the key enzyme for transformation of hydrazine into N₂ in anaerobic ammonium-oxidizing (anammox) bacteria, indicating AOA and anammox bacteria may interact with each other or they are influenced by the same controlling factors, such as NH₄⁺. The results provide a better understanding on using mangrove wetlands as biological treatment systems for removal of nutrients.     

Frequency distribution studies of epipelic diatoms along an intertidal shore

Live and dead cell counts of epipelic diatoms were analysed at 16 sites along a transect crossing a saltmarsh, sandflat, and mudflat at Berrow Flats, Somerset, U.K. Replicate monthly samples were taken from January 1982 to June 1984. The ratio of dead to live cells varied according to position along the transect. Temporal changes of the ratios did not display a cyclic seasonal pattern. The clustered mosaic of live cells and empty frustules on surface sediments was quantitatively assessed. Graphing variance against seasonal mean cell counts showed that the variance was proportional to the square of the mean. The Neyman Type A equation is suggested as a possible model to explain this relationship.     

海南岛东寨港红树林群落甲烷通量研究

 采用静态箱法对海南东寨港4个站位的5个红树林群落的土壤甲烷通量进行了研究,结果表明林地土壤平均甲烷通量为0.81mg·m-2·d-1。利用聚乙烯袋密闭法测定了6种红树植物叶片的甲烷通量,发现红树植物叶片具有吸收大气甲烷的效应。通过海莲(Bruguiera sexangula)红树林的研究还表明,林地土壤甲烷通量的日变化与林内潮水淹浸状况有关。海莲林不同滩面土壤甲烷通量的差异与土壤含水量有关。土壤甲烷通量的季节差异因植被类型或土壤性质不同而表现为两种形式。     

Modern pollen rain in mangroves from San Andres Island, Colombian Caribbean

The precise characterisation of present-day mangrove ecosystems from modern pollen rain facilitates the accurate use of fossil pollen data for late Quaternary sea level and environmental reconstructions. Here, we investigate whether the analysis of pollen rain data corroborates existing floristic and structural characterisation of different mangrove types at the Caribbean island of San Andrés, Colombia. At 82 plots along 20 transects of four distinct mangrove types, samples were obtained of (i) surface sediments for pollen analysis, and (ii) a range of environmental parameters (including inundation levels, salinity and pH). This information was compared to previously sampled mangrove composition and tree basal area. In surface sediment samples 82 pollen taxa were found, from which 19 were present in the vegetation plots. However, because pollen may be transported by wind and/or watercourses, the overall floristic composition of the different forest types may not necessarily be reflected by the pollen spectra. Local vegetation (i.e. mangroves and beach) represented > 90% of the pollen spectra, while the regional one (i.e. hinterland forests) represented < 5% of it. Unlike the four mangrove types that were previously described in the vegetation, the analysis of pollen samples suggested only three distinct types of forest.The groups were characterised based on (i) the dominance of at least one of the true mangrove species from pollen data ordination and the presence of associated species, and (ii) their relationship with environmental parameters. Rhizophora was present in all plot samples, but did not contribute to forest type separation. In fact, just three true mangrove species proved reliable indicators of (i) high salinity and fringe mangroves (i.e. Avicennia), (ii) high pH levels and landward mangroves (i.e. Conocarpus), and (iii) natural or anthropogenic caused disturbance of forest stands (Laguncularia and associated Acrostichum fern). Hence our study confirms that mangrove pollen spectra can be accurately used to describe different mangrove environments for fossil based palaeoecological reconstructions.     

Diatom, chrysophyte and protozoan distributions along a latitudinal transect in Fennoscandia

Diatoms, chrysophyte scales and cysts, and the siliceous plates of thecoamoebae were studied from the surface sediments of 20 freshwater habitats in Fennoscandia The study sites are distributed along a latitudinal transect extending from southern Finland to northern Norway, spanning boreal forest through arctic tundra vegetational zones Diatom assemblages were usually dominated by acidophilic, periphytic members of the genera Achnanthe, Fragilaria and Navicula Marked shifts in diatom assemblage composition were recorded along the latitudinal transect, whereas scaled chrysophytes were rare in all study sites Meanwhile, siliceous protozoa were common, but did not exhibit any noticeable trends in assemblage composition with changing latitude A comparison of the Fennoscandian diatom assemblages with those recorded from freshwater sites near Yellowknife (central Northwest Territories, Canada) revealed similar trends in diatom assemblage composition with changing ecoclimatic zones in both regions Moreover, canonical correspondence analysis showed that diatom assemblages in cold, dilute tundra sites were effectively separated from sites with forested catchments from both the Fennoscandian and Canadian transects The general similarity between the two regions suggests that autecological data and the resulting environmental transfer functions based on diatom assemblages may eventually be joined from North American and European regions     

西门岛人工秋茄林恢复对大型底栖生物的影响

选择乐清湾西门岛海域相同高程断面不同造林时间的人工红树林(秋茄林)、光滩和互花米草丛,采用空间代替时间的方法,分析我国分布最北界人工红树林造林过程对大型底栖生物的影响.大型底栖动物生活型分布基本表现为幼林(1、4、8a秋茄林)以底上附着型为主,而在光滩、50a秋茄林和互花米草中底下生活类群相对增加.并且穴居型动物只出现在发育成熟的生态系统内.各项指标显示50a老林群落生态稳定性较好,光滩和互花米草丛次之,但优于发育中的秋茄幼林.与以往研究结果不同,50a老林的大型底栖动物生物种类的丰度及群落的物种多样性最高,并不与红树林的发育状况呈负相关,也不比邻近光滩低.结合50a林下滩涂底泥情况,西门岛50a红树林林下滩涂的底质发育要落后于国内天然红树林土壤.这可能与当地红树林造林规模小以及强潮差海域有关.此外,红树林恢复过程中,大型底栖动物生物多样性与生态稳定性之间的线性关系,其适用的系统面积和演替时间的尺度范围有必要做更加深入的探讨.     

Structure of Benthic Diatom Assemblages from a Mangrove Environment in a Mexican Subtropical Lagoon1

The taxonomic list and the structure of benthic diatom assemblages occurring in fine sediments (silt and sand) from the mangrove forest of the Balandra lagoon in Baja California Sur, Mexico was determined based on seasonal samplings for one year. Assemblage structure was analyzed using several ecological indices for estimating diversity (H'), dominance (REDI), equitability, and similarity. A total of 230 diatom taxa were identified and include 109 new records for the Baja California peninsula coast. Taxa representative of highly productive and hypersaline environments were common. Assemblages were characterized by a few abundant species and many uncommon or rare taxa. High diatom diversity estimates at all sampling sites during all seasons suggest that diatom assemblages in sediments of the Balandra lagoon represent a quasi-pristine environment.