Pleistocene reef environments, constituent grains, and coral community structure: Curaçao, Netherlands Antilles

We investigated the degree to which component grains vary with depositional environment in sediments from three reef habitats from the Pleistocene (125?ka) Hato Unit of the Lower Terrace, Curaçao, Netherlands Antilles: windward reef crest, windward back reef, and leeward reef crest. The windward reef crest sediment is the most distinctive, dominated by fragments of encrusting and branching coralline red algae, coral fragments and the encrusting foraminiferan Carpenteria sp. Windward back reef and leeward reef crest sediments are more similar compositionally, only showing significant differences in relative abundance of coral fragments and Homotrema rubrum. Although lacking high taxonomic resolution and subject to modification by transport, relative abundance of constituent grain types offers a way of assessing ancient skeletal reef community composition, and one which is not limited to a single taxonomic group. The strong correlation between grain type and environment we found in the Pleistocene of Curaçao suggests that constituent grain analysis may be an effective tool in delineating Pleistocene Caribbean reef environments. However, it will not be a sufficient indicator where communities vary significantly within reef environments or where evolutionary and/or biogeographical processes lead to different relationships between community composition and reef environment. Detailed interpretation of geological, biological, and physical characteristics of the Pleistocene reefs of Curaçao reveals that the abundance of the single coral species, Acropora palmata, is not a good predictor of the ecological structure of the ancient reef coral communities. This coral was the predominant species in two of the three reef habitats (windward and leeward reef crest), but the taxonomic composition (based on species relative abundance data) of the reef coral communities was substantially different in these two environments. We conclude that qualitative estimates of coral distribution patterns (presence of a key coral species or the use of a distinctive coral skeletal architecture), when used as a component in a multi-component analysis of ancient reef environments, probably introduces minimal circular reasoning into quantitative paleoecological studies of reef coral community structure.     

Relative Importance of Coral Cover,Habitat Complexity and Diversity in Determining the Structure of Reef Fish Communities

The structure of coral reef habitat has a pronounced influence on the diversity, composition and abundance of reef-associated fishes. However, the particular features of the habitat that are most critical are not always known. Coral habitats can vary in many characteristics, notably live coral cover, topographic complexity and coral diversity, but the relative effects of these habitat characteristics are often not distinguished. Here, we investigate the strength of the relationships between these habitat features and local fish diversity, abundance and community structure in the lagoon of Lizard Island, Great Barrier Reef. In a spatial comparison using sixty-six 2m² quadrats, fish species richness, total abundance and community structure were examined in relation to a wide range of habitat variables, including topographic complexity, habitat diversity, coral diversity, coral species richness, hard coral cover, branching coral cover and the cover of corymbose corals. Fish species richness and total abundance were strongly associated with coral species richness and cover, but only weakly associated with topographic complexity. Regression tree analysis showed that coral species richness accounted for most of the variation in fish species richness (63.6%), while hard coral cover explained more variation in total fish abundance (17.4%), than any other variable. In contrast, topographic complexity accounted for little spatial variation in reef fish assemblages. In degrading coral reef environments, the potential effects of loss of coral cover and topographic complexity are often emphasized, but these findings suggest that reduced coral biodiversity may ultimately have an equal, or greater, impact on reef-associated fish communities.     

Degradation succession of heterotrophic flagellate communities in microcosms

Degradation succession of heterotrophic flagellate communities was studied in samples of detritus and water from a small swamped lake in the environs of the settlement Borok, Yaroslavl province. Three stages of succession with different species composition of the heterotrophic flagellate community were clearly recognized. Cumulative properties of the community change with time. Maximum species richness, diversity, and abundance were observed on the fourth day of succession; their values gradually decreased later. The trophic and taxonomic community structure was most diverse at the earlier stages of succession. Primordial food (bacteria) concentration affects only the size of peak community properties, but has no influence on the pattern of succession changes. The influence of predators considerably reduced heterotrophic flagellate abundance and can shift the time of the stage with maximum species diversity in the course of succession.     

Recovery without resilience: persistent disturbance and long-term shifts in the structure of fish and coral communities at Tiahura Reef, Moorea

Disturbances have a critical effect on the structure of natural communities. In this study long-term changes were examined in the reef community at Tiahura Reef, on the northern coast of Moorea, which had been subject to many and varied disturbances over the last 25 years. Tiahura Reef was subject to an outbreak of crown-of-thorns starfish (Acanthaster planci) in 1980–1981, causing significant declines in the abundance of scleractinian corals and butterflyfishes. By 2003, the abundance of corals and butterflyfishes had returned to former levels, but despite this apparent recovery, the species composition of coral communities and butterflyfish assemblages was very different from those recorded in 1979. Ongoing disturbances (including further outbreaks of crown-of-thorns starfish, cyclones, and coral bleaching events) appear to have prevented recovery of many important coral species (notably, Acropora spp.), which has had subsequent effects on the community structure of coral-feeding butterflyfishes. This study shows that recurrent disturbances may have persistent effects on the structure and dynamics of natural communities.     

Spatial structure of coral reef fish communities at Kudaka Island (Ryukyu Archipelago), Japan

The present study aimed to investigate the spatial structure of fish communities at juvenile and adult stages on coral reefs at Kudaka Island (Ryukyu Archipelago, Japan) and to relate spatial patterns in the structure of the fish communities to gradients in environmental variables. Diurnal visual censuses allowed us to record 2,602 juveniles belonging to 60 species and 1,543 adults belonging to 53 species from October to December 2005. The distribution of species highlighted that the juvenile community was organised into three distinct assemblages, rather than exhibiting gradual change in community structure along the cross-reef gradient. Correlations between spatial patterns of juvenile community and environmental variables revealed that the most significant factors explaining variation in community structure were coral rubble and coral slab. In contrast, the adult community was organised into one assemblage, and the most significant variation factors in community structure were depth, live coral in massive form, live coral in branched form, dead coral and sand. Overall, the present study showed that most juvenile and adult coral reef fish at Kudaka Island exhibited striking patterns in their distribution and depth and some biological factors (e.g., abundance of live coral, dead coral and coral rubble) might exert considerable influence on the distribution of fishes.     

长白山红松阔叶林不同演替阶段优势种的变化

以皆伐后长白山红松阔叶林4个不同演替阶段的林分为对象,分析其群落和优势树种的变化特征.结果表明:在长白山红松阔叶林不同演替阶段中,乔木树种的丰富度、Shannon多样性和Simpson优势度变化较小,多度和均匀度变化较大.随着演替的进程,群落的优势树种组成发生变化,种数逐渐减少,优势种的胸高断面积加和和最大重要值逐渐增加,说明不同演替阶段群落的优势种地位不断提高.长白山红松阔叶林的演替过程是白桦、山杨、黄檗、春榆等阳性或半阴性树种不断减少,而紫椴、水曲柳、红松、色木槭等阴性树种不断增加的过程.     

Multiple modes in a coral species abundance distribution

Species abundance distributions are an important measure of biodiversity and community structure. These distributions are affected by sampling, and alternative species-abundance models often make similar predictions for small sample sizes. Very large samples reveal the relative abundances of rare species, and thus provide information about species relative abundances that small samples cannot. Here, we present the species-abundance distribution for a sample of > 40,000 coral colonies at a single site, exceeding existing samples of coral local assemblages by over an order of magnitude. This abundance distribution is multimodal when examined on a logarithmic scale. Four different model selection procedures all indicate that the underlying community abundance distribution has at least three modes. We show that the multiple modes are not caused by mixtures of species with different habitat preferences. However, spatial aggregation partially explains our results. We inspect published work on species abundance distributions, and suggest that multimodality may be a common feature of large samples.     

内蒙古准格尔旗对臼沟本溪组及腕足动物群落

介绍了内蒙古准格尔旗对臼沟本溪组含腕足动物地层,对该地区本溪组腕足动物群和性质特点进行了分析。并在识别腕足动物群落的基础上,从种的分异度,种的相对丰度,群落空间分布与能量分配等角度探讨了该腕足动物群落的一些结构模式,指出Ｅｃｈｉｎｏｃｏｃｈｕｓ ｅｌｅｇａｎｓ－Ｏｈｏｒｉｓｔｉｔｅｓ ｗｅｉｎｉｎｇｅｎｓｉｓ腕足动物群落已基本属于演替阶段中的顶极群落。     

The Community Dynamics of the Forest Secondary Succession in Heishiding Natural Reserve of Guangdong Province

Studying on the community structure, species composition and species diversities of the secondary succession of lower subtropical forest in Heishiding Natural Reserve, Guangdong Province, the following results were obtained. In 2 ~4 years of restored stage the seedlings of pioneer species, heliophytes and mesophytes occur simultaneously. In 10 years of restored stage pioneer species are superior as heliophytes maintain stable and mesophytes are being decreased. In the stage of mixed forest pioneer species are on the decreasing and heliopytes are on the increasing trend. In the stage of evergreen broad-leaved forest dominated by heliophytes pioneer species are being declined, heliophytes are dominant and mesophytes are being increased. In the stage of evergTeen broad-leaved forest dominated by mesophytes heliophytes are being declined and mesophytes are superior. The vertical structure, horizontal structure, the structure of species composition determine stability of communities in secondary succession process. The vertical structure of community is building up in the stage of restoration. The community is composed of the stands under the third class. The forest canopy is not stratified. The individual density is stable. From restored stage to mixed forest the vertical structure of community is diversified. There are the third and forth class stands in community. The tree layer is divided into three sub-layers. The individual density declines rapidly because of self-thinning. In the mixed forest the vertical stmcture is relatively stable. The abundance of the fifth class stands and area of breast height reach the first peak in the succession serial. The individual density increases rapidly. In stage of evergreen broad-leaved forest dominated by heliophytes, the vertical structure changes largely. The abundance of the fifth class and area of breast height decline rapidly, but the individual density changes slowly. In the stage of evergreen broad-leaved forest dominated by mesophytes, the vertical structure of community is stable and the composition of every stand class becomes more stable. The area of breast height is the biggest in the succession serial. When succession develops, the coverage of communities increases gradually but the turnover rate of species declines. The species composition tends to be stabilized. The diversity of species and community evenness increase gradually thus, the ecological dominance declines gradually.     

Dynamic analysis of phytoplankton community characteristics in Daya Bay, China

Daya Bay is a large bay along the southern coast of China. The composition, abundance, community structure and diversity of phytoplankton in Daya Bay were investigated to assess its status in different seasons in 2002, and a total of 48 genera and 114 species of phytoplankton were identified. The cell abundance of phytoplankton varied from 5.79 × 10⁴ cells/m³ to 5.37 × 10⁶ cells/m³ with an average of 1.14×10⁶ cells/m³. The largest community was Bacillariophyta containing 84 taxa, and its average abundance was 1.08 × 10⁶ cells/m³. Annual abundance variations show a typical one-peak cycle, with the highest peak recorded during summer and the lowest recorded during autumn. The ecotypes of phytoplankton were mostly alongshore warm-water species; however, marine warm-water species and eurytopic species during winter and autumn are more abundant than during the other seasons. The dominant species were diverse and varied with seasons. The species diversity index of phytoplankton in Daya Bay was low during summer, especially near the nuclear power station (NPS) and the aquaculture farms during summer and autumn. Community structure and cell abundance were categorized in relation to monsoon, current and anthropological activities. It is presented that the temperature and hydrodynamics in conjunction with the pattern of nutrients (DIN, DIP and N/P) availability and depletion affect the composition, abundance, community structure, community succession and diversity of phytoplankton.     

涠洲岛造礁石珊瑚群落变化特征及其环境影响因子

以涠洲岛造礁石珊瑚群落为研究对象,分析其群落物种组成、多样性、Raunkiaer频度和种间Spearman轶相关,探讨群落组成与水环境因子的相关性,并结合近10年来涠洲岛造礁石珊瑚变化情况,找出涠洲岛造礁石珊瑚群落的主导影响因素。结果表明：（1）近10年来涠洲岛造礁石珊瑚覆盖率显著降低,珊瑚形态组成趋于块状化,尽管珊瑚群落多样性较高,但群落分布较松散,群落结构较不稳定,部分优势种种间竞争较激烈。（2）悬浮物含量是影响石珊瑚群落最显著的环境因子。石珊瑚优势种群在不同水深中分布差异显著,泥沙覆盖率、营养盐对不同石珊瑚种群影响差异较大,大型海藻覆盖率在局部区域对优势珊瑚形成较强的竞争关系。（3）营养盐和泥沙沉积物的增加与涠洲岛近海养殖业及生活排污、海岸工程及海岸侵蚀密切相关。     

Reef fish assemblages in north-western Sri Lanka: distribution patterns and influences of fishing practises

The distribution and abundance of reef fishes in relation to habitat structure were studied within Bar Reef Marine Sanctuary (BRMS) and on an adjacent reef, disturbed by destructive fishing techniques, in north-western Sri Lanka, by visually censusing 135 species groups using fifty metre belt-transects. Two types of continental shelf patch-reefs are found in the study area: coral reefs and sandstone reefs, which are divided into distinct habitats, four for the coral reef (shallow reef flat, shallow patch reef, deep reef flat and Porites domes) and two for the sandstone reef (structured sandstone-reef and flat sandstone-reef). Fish assemblages varied in structure between reef types and among habitats within reef types. Functional aspects of habitat structure and composition, such as available food and shelter, seemed to be important factors influencing distribution patterns. The strongest separation in the organisation of fish assemblages in BRMS was between reef types: 19% of all species were confined to the coral-reef patches while 22% were restricted to the sandstone reef patches and 59% were represented on both reef types. In terms of distribution among habitats, 21% of all species were restricted to one habitat while only 1.5% were present in all. The highest density of fish was in the coral reef habitats while highest species diversity was found in the most structurally complex habitat: the structured sandstone-reef. This habitat also had the highest proportion of species with restricted distribution. Planktivores were the most abundant trophic group in BRMS, and the species composition of the group varied among habitats. The comparison of the disturbed reef with BRMS suggested that habitat alteration caused by destructive fishing methods has strongly influenced the fish community. Within the fished area the structure of the fish assemblages was more heterogeneous, fish abundance was lower by an order of magnitude and species numbers were lower than in BRMS.     

Dynamic analysis of phytoplankton community characteristics in Daya Bay, China

Daya Bay is a large bay along the southern coast of China. The composition, abundance, community structure and diversity of phytoplankton in Daya Bay were investigated to assess its status in different seasons in 2002, and a total of 48 genera and 114 species of phytoplankton were identified. The cell abundance of phytoplankton varied from 5.79 × 10⁴ cells/m³ to 5.37 × 10⁶ cells/m³ with an average of 1.14×10⁶ cells/m³. The largest community was Bacillariophyta containing 84 taxa, and its average abundance was 1.08 × 10⁶ cells/m³. Annual abundance variations show a typical one-peak cycle, with the highest peak recorded during summer and the lowest recorded during autumn. The ecotypes of phytoplankton were mostly alongshore warm-water species; however, marine warm-water species and eurytopic species during winter and autumn are more abundant than during the other seasons. The dominant species were diverse and varied with seasons. The species diversity index of phytoplankton in Daya Bay was low during summer, especially near the nuclear power station (NPS) and the aquaculture farms during summer and autumn. Community structure and cell abundance were categorized in relation to monsoon, current and anthropological activities. It is presented that the temperature and hydrodynamics in conjunction with the pattern of nutrients (DIN, DIP and N/P) availability and depletion affect the composition, abundance, community structure, community succession and diversity of phytoplankton.     

Tree diversity drives diversity of arthropod herbivores,but successional stage mediates detritivores

The high tree diversity of subtropical forests is linked to the biodiversity of other trophic levels. Disentangling the effects of tree species richness and composition, forest age, and stand structure on higher trophic levels in a forest landscape is important for understanding the factors that promote biodiversity and ecosystem functioning. Using a plot network spanning gradients of tree diversity and secondary succession in subtropical forest, we tested the effects of tree community characteristics (species richness and composition) and forest succession (stand age) on arthropod community characteristics (morphotype diversity, abundance and composition) of four arthropod functional groups. We posit that these gradients differentially affect the arthropod functional groups, which mediates the diversity, composition, and abundance of arthropods in subtropical forests. We found that herbivore richness was positively related to tree species richness. Furthermore, the composition of herbivore communities was associated with tree species composition. In contrast, detritivore richness and composition was associated with stand age instead of tree diversity. Predator and pollinator richness and abundance were not strongly related to either gradient, although positive trends with tree species richness were found for predators. The weaker effect of tree diversity on predators suggests a cascading diversity effect from trees to herbivores to predators. Our results suggest that arthropod diversity in a subtropical forest reflects the net outcome of complex interactions among variables associated with tree diversity and stand age. Despite this complexity, there are clear linkages between the overall richness and composition of tree and arthropod communities, in particular herbivores, demonstrating that these trophic levels directly impact each other.     

云南松林次生演替阶段土壤细菌群落的变化

土壤细菌多样性是维持森林生态系统功能的关键因子,森林演替是影响其动态变化的重要因素.研究云南松林不同演替阶段土壤细菌群落结构及其多样性的变化规律,有助于深入理解森林生态系统恢复过程的驱动机制.本研究以云南省永仁县皆伐后形成的针叶林、针阔混交林和常绿阔叶林为对象,基于Illumina Hiseq高通量测序技术,分析森林演...     

Relationships between structural complexity,coral traits,and reef fish assemblages

With the ongoing loss of coral cover and the associated flattening of reef architecture, understanding the links between coral habitat and reef fishes is of critical importance. Here, we investigate whether considering coral traits and functional diversity provides new insights into the relationship between structural complexity and reef fish communities, and whether coral traits and community composition can predict structural complexity. Across 157 sites in Seychelles, Maldives, the Chagos Archipelago, and Australia’s Great Barrier Reef, we find that structural complexity and reef zone are the strongest and most consistent predictors of reef fish abundance, biomass, species richness, and trophic structure. However, coral traits, diversity, and life histories provided additional predictive power for models of reef fish assemblages, and were key drivers of structural complexity. Our findings highlight that reef complexity relies on living corals—with different traits and life histories—continuing to build carbonate skeletons, and that these nuanced relationships between coral assemblages and habitat complexity can affect the structure of reef fish assemblages. Seascape-level estimates of structural complexity are rapid and cost effective with important implications for the structure and function of fish assemblages, and should be incorporated into monitoring programs.     

Community Characteristics of Early Recovery Vegetation on Abandoned Lands of Shifting Cultivation in Bawangling of Hainan Island, South China

Shifting cultivation is a major form of agricultural practice in most parts of tropical regions worldwide. In places where the bush fallow period is excessively shortened or the period of cultivation is extended for too long, the rate of vegetation recovery and biodiversity on abandoned lands of shifting cultivation would decline. The recovery of the secondary plant communities could even be inhibited for a prolonged period because of grass occupancy. Because of the vital significance of the early recovery communities to secondary succession, we studied the community characteristics of early recovery vegetation on abandoned lands of shifting cultivation in Bawangling of Hainan Island. Measurements were made of the community composition and structure of early recovery vegetation. The sprouting abilities of different functional groups and different species in the same functional group, and the effect of the grass functional group on the composition and quantitative characteristics of tree and shrub functional groups were analyzed. Results indicated that only a few families, genera, or species apparently dominated in the early recovery vegetation on the abandoned lands of shifting cultivation and that deciduous species occurred with a rather high percentage in this early recovery community compared with the natural secondary or old growth forests. Smallsized individuals dominated the woody community. The abundance and basal area of sprouting stems for species in the tree functional group were greater than those of seeder stems, whereas the abundance and basal area of resprouters and seeders for species in the shrub functional group did not differ. The total abundance of stems for the community, stem abundances for species in tree or shrub functional groups, and for seeder or resprouter stems were all negatively correlated with coverage of the grass functional group. The mean sprouting ability in the tree functional group was greater than in the shrub functional group. The sprouting ability for different species in the same functional group was also significantly different.     

What determines emergence and net recruitment in an early succession plant community? Disentangling biotic and abiotic effects

Question: How do different regeneration scenarios shape species composition at two stages of plant community establishment (emergence and net recruitment) in an early succession? Location: Northern Spain. Methods: In a recently ploughed field, we created eight regeneration scenarios with light, water and nitrogen availability (five replicates each). Seedlings of all species were monitored from emergence to death during one year. Abiotic and biotic variables were measured per quadrat, i.e. soil texture, nutrient contents, seed bank densities and composition, neighbour plant species densitiy and cover. We used partial ordination methods in order to separate the effect of each environmental variable on species composition during emergence and adult net recruitment. Results: Light treatment determined annual plant density at time of emergence and recruitment, while water addition controlled the recruitment of perennials. Resource levels explained the emerged species composition; this effect was not translated into the recruited species composition. N‐addition and N + water addition were strongly associated to species abundances at the time of emergence. Seedling composition in summer was correlated with seed abundance of Cerastium spp. Neighbour species density and cover (mainly Arrhenatherum bulbosum, Agropyron repens and Picris echioides) explained significant fractions of species composition in the emergence and recruitment of the different cohorts. Interactions between species seem to vary in intensity among cohorts and in the key plant species that determined species abundance along succession. Conclusions: Our scenarios exerted contrasting and multilevel effects on the development of our early succession community. Resource availability differently affected plant density and species composition at different life stages. It is relevant to consider different life stages in plant community studies. However, regeneration conditions and other abiotic factors are not enough to explain how community composition varies.     

Community structure and habitat associations of parrotfishes on Oahu,Hawaii

Despite their ecological importance as bioeroders and their economic importance in commercial, artisanal, and recreational fisheries, there have been relatively few studies on parrotfish (Scaridae) ecology in Hawaii. Belt transects were conducted around the island of Oahu to survey current parrotfish distributions, size structure, species composition and associated habitats. Scarid communities in this heavily fished region are dominated by smaller species and smaller individuals within all species. Specific habitat characteristics such as rugosity, substrate diversity, and percent live coral cover were positively correlated with scarid numerical abundance. Scarids, however, were patchily distributed and were often absent from preferable habitats, suggesting that intense fishing pressure may be an important factor preventing these fish from fully exploiting available habitats. This study is the first thorough, broad-scale investigation of scarid community structure in Hawaii, and provides important information that has management and conservation implications for parrotfish in Hawaii and throughout tropical coral reef ecosystems.     

Effects of grazing by Diadema antillarum Philippi (Echinodermata: Echinoidea) on algal diversity and community structure

In Discovery Bay, Jamaica W.I., densities of Diadema antillarum Philippi were experimentally manipulated over a range of 0–64 individuals · m^?2 with the aid of enclosures in shallow water. The effects of grazing by this echinoid on the algal community structure of a coral reef were compared under conditions of primary and post-primary succession.Algal biomass decreased as Diadema density was increased, particularly under primary succession conditions. A similar response was noted under post-primary conditions, but here biomass was also dependent on species composition and abundance of algae prior to experimental alterations of Diadema density. Peyssonnelia sp. was found to be particularly resistant to echinoid grazing, surviving even the most intense grazing. Within 11 months, algal diversity decreased significantly in an exponential fashion as Diadema density increased. This occurred under conditions of both primary and post-primary succession. Diversity, irrespective of index, was not maximized at intermediate grazing pressures. No single species of alga dominated the benthic community at even the lowest Diadema densities.Species composition of algae in the benthic community prior to changes in grazing pressure and lack of successful recruitment of a potential dominant were found to have a major influence on the response of the algal community to the treatments. Each of these factors can influence both the relationship between algal diversity and grazing pressure and the rate at which the community approaches an initial plateau of diversity in its earliest stages of succession.