Community Dynamics In Relation Research Articles

PHYTOPLANKTON COMMUNITY DYNAMICS RELATED TO CERTAIN PHYSICAL AND CHEMICAL VARIABLES IN ARDIÇTEPE RESERVOIR (BALIKESIR, TURKEY)

Ardıçtepe Reservoir (Balıkesir, Turkey) was sampled seasonally at three stations between October 2018 and August 2019 to determine the phytoplankton community dynamics in relation to water temperature, speciffic conductance (SC), total dissolved solids (TDS), pH, oxidation-reduction potential (ORP) and Secchi disk depth. A total of 43 phytoplankton species were identified, 27 from Bacillariophyta, 4 from Charophyta, 6 from Chlorophyta, 5 from Cyanobacteria and 1 from Euglenozoa. Bacillariophyta made 76% total number of species, Cyanobacteria 11%, Chlorophyta 6%, Charophyta 4% and Euglenozoa 3%. Aulacoseria granulata, Aulacoseira granulata var. angustissima, Cyclotella meneghiniana and Ulnaria ulna from Bacillariophyta and Anabaena circinalis from Cyanobacteria dominanted phytoplankton during the study. The CCA explained 90.8% of the cumulative variance in the relationships of dominant species-environment. The CCA also showed that water temperature, TDS, ORP and pH had significant effects on the phytoplankton community of Ardıçtepe Reservoir (Monte Carlo test, p 0.05)

Sequence-based identification of soil fungi in different habitats on Surtsey

Studies on primary succession and biological surveys in Surtsey have described the presence of different organisms including plants, soil fauna and fungi. However, since the last fungal census of 2008, based on visual observations, no further studies on fungal communities on the island have been published. In the present study, we aimed to expand the knowledge of the fungal communities of Surtsey using Internal Transcribed Spacer (ITS2) metabarcode sequencing to survey soil samples from 23 permanent plots, within and outside a gull colony. Additionally, we related fungal community composition to soil and ecosystem environmental variables that have been analyzed from these plots previously. We report at least 18 new genera and 44 new species for Iceland and 56 new species for Surtsey in this metabarcode survey, likely representing a combination of established organisms as well as those that may be present as dormant propagule bank. Our data indicate that fungal communities differ in areas with and without sea gulls as well as those that differ in soil substrate. Further, the community composition correlates with the number of gull nests, vegetation cover, ecosystem respiration, total N and exchangeable P. This survey provides new insights on the fungal community dynamics in relation to other biotic and abiotic factors. These findings complement what available data on soil biosphere on Surtsey and improve our understanding of primary succession.

Sequence-based identification of soil fungi in different habitats on Surtsey

ABSTRACT Studies on primary succession and biological surveys in Surtsey have described the presence of different organisms including plants, soil fauna and fungi. However, since the last fungal census of 2008, based on visual observations, no further studies on fungal communities on the island have been published. In the present study, we aimed to expand the knowledge of the fungal communities of Surtsey using Internal Transcribed Spacer (ITS2) metabarcode sequencing to survey soil samples from 23 permanent plots, within and outside a gull colony. Additionally, we related fungal community composition to soil and ecosystem environmental variables that have been analyzed from these plots previously. We report at least 18 new genera and 44 new species for Iceland and 56 new species for Surtsey in this metabarcode survey, likely representing a combination of established organisms as well as those that may be present as dormant propagule bank. Our data indicate that fungal communities differ in areas with and without sea gulls as well as those that differ in soil substrate. Further, the community composition correlates with the number of gull nests, vegetation cover, ecosystem respiration, total N and exchangeable P. This survey provides new insights on the fungal community dynamics in relation to other biotic and abiotic factors. These findings complement what available data on soil biosphere on Surtsey and improve our understanding of primary succession.

Tracking the effect of temperature in marine demersal fish communities

Under current levels of global warming most demersal species in the Northeast Atlantic are experiencing tropicalization, meridionalization or borealization of their distributions, leading to profound changes in demersal communities. We explore these changes using the Community Weighted Mean Temperature (CWMT), an index to link the thermal preference of demersal fish communities and temperature. The CWMT is calculated as the summation of the mean temperature of each fish species distribution weighted by its relative abundance in the community. The relative abundance is based on the community composition data obtained by the International Bottom Trawl Surveys (IBTS) in the Southern Bay of Biscay between 1983 and 2015. Our analyses show that the CWMT responds to the actual temperature of the water column reproducing its space–time trends in the study area: (i) an increase from SW to NE, towards the inner Bay of Biscay, (ii) a decrease with depth, except in the SW area characterized by an intense upwelling, (iii) a general increase along the time series. Applying a k-means classification to the CWMT data we identified warm-, temperate- and cold-communities over the shelf and slope and their spatial changes in the last decades. The area occupied by warm communities has expanded 268.4 km2/yr since the 80 s, while the cold communities have retracted at a speed of −155.4 km2/yr. The CWMT was able to capture the community dynamics in relation to environmental temperature at different temporal and spatial scales, highlighting the potential of this index to explore and anticipate the effects of climate change in demersal communities under different scenarios of global warming.

Microbial communities associated with distance- and density-dependent seedling mortality in a tropical rainforest

The high levels of diversity within tropical rainforest communities has been linked to non-random patterns of seedling mortality with several studies implicating pathogenic plant–microbe interactions in driving mortality processes. Despite the proposed importance of microorganisms in maintaining rainforest diversity, few studies have investigated soil community dynamics in relation to non-random mortality processes. A mechanistic understanding of microbial processes that help create rainforest diversity is critical for the conservation of these ecosystems. This study investigated microbial community dynamics that may underpin distance- and density-dependent mortality in the long-term forest dynamics plot, Davies Creek, in tropical Far North Queensland using community fingerprinting. We hypothesized that: (1) microbial involvement in distance-dependent seedling mortality would result in an increase in community similarity or the presence of predictor OTUs in conspecific adult tree rhizospheres, relative to physically nearby heterospecifics; (2) on average, plant species identified as having a history of distance dependent seedling mortality would exhibit more similar microbial communities among their conspecific individuals, than those that did not; and (3) dense patches of conspecific seedlings would promote the assembly of distinct soil microbial communities, which may be involved in density-dependent seedling mortality. We found no evidence of rhizosphere community similarity amongst adult plant rhizospheres. However, the presence of densely germinating seedlings altered the soil communities relative to seedling-sparse soils, enriching different OTUs depending on the patch location.

Dynamics of a Perturbed Microbial Community during Thermophilic Anaerobic Digestion of Chemically Defined Soluble Organic Compounds.

Knowledge of microbial community dynamics in relation to process perturbations is fundamental to understand and deal with the instability of anaerobic digestion (AD) processes. This study aims to investigate the microbial community structure and function of a thermophilic AD process, fed with a chemically defined substrate, and its association with process performance stability. Next generation amplicon sequencing of 16S ribosomal RNA (rRNA) genes revealed that variations in relative abundances of the predominant bacterial species, Defluviitoga tunisiensis and Anaerobaculum hydrogeniformans, were not linked to the process performance stability, while dynamics of bacterial genera of low abundance, Coprothermobacter and Defluviitoga (other than D. tunisiensis), were associated with microbial community function and process stability. A decrease in the diversity of the archaeal community was observed in conjunction with process recovery and stable performance, implying that the high abundance of specific archaeal group(s) contributed to the stable AD. Dominance of hydrogenotrophic Methanoculleus particularly corresponded to an enhanced microbial acetate and propionate turnover capacity, whereas the prevalence of hydrogenotrophic Methanothermobacter and acetoclastic Methanosaeta was associated with instable AD. Acetate oxidation via syntrophic interactions between Coprothermobacter and Methanoculleus was potentially the main methane-formation pathway during the stable process. We observed that supplementation of Se and W to the medium improved the propionate turnover by the thermophilic consortium. The outcomes of our study provided insights into the community dynamics and trace element requirements in relation to the process performance stability of thermophilic AD.

Plant community change in three Mongolian steppe ecosystems 1994–2013: applications to state‐and‐transition models

AbstractInteracting effects of climate change and livestock grazing on semi‐arid grassland ecosystems have not been well studied, especially on a long‐term basis. This paper analyzes changes in plant community composition in relation to grazing intensity and climate change based on repeated monitoring along long‐term grazing intensity gradients in three Mongolian ecological zones over 20 yr. We synthesized our findings into state‐and‐transition models of vegetation change, contributing to our understanding of ecological dynamics in relation to management and environmental change, and to the development of tools for resilience‐based rangeland management. In the mountain steppe (MS), community composition was driven largely by climate, and transitions from one community to another were associated with climate change or combined climate and grazing effects. The MS experienced the largest number of long‐term transitions (14 of 15 plots) over 20 yr. In the steppe (ST), grazing intensity was the strongest influence on community composition, but transitions between communities from the early 1990s to 2013 were most strongly correlated with climate change. Ten of the 15 ST plots transitioned to other communities over 20 yr. Community composition in the desert steppe (DS) was unrelated to either grazing intensity or climate change and only six of 15 plots transitioned permanently over 20 yr. The MS appears most vulnerable to climate‐induced community change, as others have suggested. Some degraded ST communities are resilient to climate change, while ST communities on drier sites are vulnerable to grazing‐induced community changes. Our findings illustrate the utility of state‐and‐transition models as a means to synthesize and depict plant community dynamics in relation to climate and management factors. These models identify communities that may be growing rarer or more common under the combined effects of climate change and grazing, and highlight species and communities that may be useful conservation targets or indicators of climate‐ or grazing‐induced change.

Soil bacterial and fungal community dynamics in relation to Panax notoginseng death rate in a continuous cropping system.

Notoginseng (Panax notoginseng), a valuable herbal medicine, has high death rates in continuous cropping systems. Variation in the soil microbial community is considered the primary cause of notoginseng mortality, although the taxa responsible for crop failure remains unidentified. This study used high-throughput sequencing methods to characterize changes in the microbial community and screen microbial taxa related to the death rate. Fungal diversity significantly decreased in soils cropped with notoginseng for three years. The death rate and the fungal diversity were significantly negatively correlated, suggesting that fungal diversity might be a potential bioindicator of soil health. Positive correlation coefficients revealed that Burkholderiales, Syntrophobacteraceae, Myrmecridium, Phaeosphaeria, Fusarium, and Phoma were better adapted to colonization of diseased plants. The relative abundance of Fusarium oxysporum (R = 0.841, P < 0.05) and Phaeosphaeria rousseliana (R = 0.830, P < 0.05) were positively associated with the death rate. F. oxysporum was a pathogen of notoginseng root-rot that caused seedling death. Negative correlation coefficients indicated that Thermogemmatisporaceae, Actinosynnemataceae, Hydnodontaceae, Herpotrichiellaceae, and Coniosporium might be antagonists of pathogens, and the relative abundance of Coniosporium perforans was negatively correlated with the death rate. Our findings provide a dynamic overview of the microbial community and present a clear scope for screening beneficial microbes and pathogens of notoginseng.

Insect community dynamics in relation to climate change in Mongolia

In recent years, many research revealed plant-insect interactions are becoming unstable because of climate change, human activities and grazing effect. In this work, it is aimed to disclose that how climate of two different years is influencing on insect community at certain locality in Mongolia. The data on the insect community are collected, covering full flowering season from June to August in 2014 and 2015. In order to include all species of insects in Udleg Station, data was collected in three different sites. One of them was around edge of forest, another one was in ungrazed area or inside the fence that has been kept for more than 9 years and last one was in grazed area. Weather was a perceptible difference during two year's study. This climate differences significantly influenced on the insect community. In 2014, overall 305 insect species were recorded, in which 124 insect species in order of Diptera, 44 in Lepidoptera, 33 in Coleoptera, 31 in Hemiptera, and 73 in Hymenoptera were determined. But in 2015, these number of species noticeably decreased, and total 150 insect species were recorded, in which 58 in Diptera, 26 in Lepidoptera, 13 in Coleoptera, 12 in Hemiptera, and 41 in Hymenoptera were determined.

The VENUS cabled observatory as a method to observe fish behaviour and species assemblages in a hypoxic fjord, Saanich Inlet (British Columbia, Canada)

Studies reporting processes that may shape marine benthic communities under the seasonal scale are rare at depths &gt;50 m. In this study, the use of the VENUS multidisciplinary cabled observatory provided 2-month high-resolution data combining quantitative biology and environmental data in Saanich Inlet, a seasonally hypoxic fjord located on Vancouver Island (British Columbia, Canada). An ecological module equipped with a camera acquired a 3 min video clip every half hour during 2 months at 97 m depth in the oxygen fluctuation zone of the fjord. Results highlighted the role of the tidal cycle on species activity rhythms and confirmed the influence of oxygen fluctuations on benthic assemblage structure and species behaviour. However, environmental variables considered only explained a small proportion of the total variance in species data. This study demonstrates how seafloor observatories can be used to study species behaviour and community dynamics in relation to abiotic conditions by providing continuous access to multidisciplinary data.

Fungal community dynamics in relation to substrate quality of decaying Norway spruce (Picea abies [L.] Karst.) logs in boreal forests

Decaying wood plays an important role in forest biodiversity, nutrient cycling and carbon balance. Community structure of wood-inhabiting fungi changes with mass loss of wood, but the relationship between substrate quality and decomposers is poorly understood. This limits the extent to which these ecosystem services can be effectively managed. We studied the fungal community and physico-chemical quality (stage of decay, dimensions, density, moisture, C : N ratio, lignin and water or ethanol extractives) of 543 Norway spruce logs in five unmanaged boreal forest sites of southern Finland. Fungi were identified using denaturing gradient gel electrophoresis and sequencing of DNA extracted directly from wood samples. Macroscopic fruiting bodies were also recorded. Results showed a fungal community succession with decreasing wood density and C : N ratio, and increasing moisture and lignin content. Fungal diversity peaked in the most decayed substrates. Ascomycetes typically colonized recently fallen wood. Brown-rot fungi preferred the intermediate decay stages. White-rot fungi represented approximately one-fifth of sequenced species in all decay phases excluding the final phase, where ectomycorrhizal (ECM) fungi became dominant. Lignin content of logs with white-rot fungi was low, and ECM fungi were associated with substrates containing abundant nitrogen. Macroscopic fruiting bodies were observed for only a small number of species detected with molecular techniques.

Palaeozoological insights into management options for a threatened mammal: southern Africa’s Cape mountain zebra (Equus zebra zebra)

AbstractAim  Promoting population growth of genetically distinct subpopulations of Cape mountain zebra (Equus zebra zebra) is crucial to the survival of the subspecies. Several important Cape mountain zebra reserves are dominated by fynbos vegetation, and population growth is limited by a lack of grassland habitat. A fossil ungulate sequence spanning the last c. 18,000 years is examined to understand the long‐term history of this conservation challenge.Location  Boomplaas Cave (BPA), South Africa.Methods  The fossil sequence from BPA is examined to reconstruct ungulate community dynamics in relation to climate and vegetation change over the last 18,000 years.Results  Ungulates from 18,000 to 12,000 years ago suggest an expansion of open grasslands that supported a grazing ecosystem dominated by an extinct caprine antelope and equid remains attributed to E. zebra and E. quagga. At the onset of the Holocene, the grazing ungulate community disappears and small browsers and mixed feeders dominate the assemblage, indicating the loss of open grassland vegetation. Several open‐habitat grazers go extinct at this time, and Equus persists at much lower abundances. This shift can be explained by global climate change across the Pleistocene–Holocene transition.Main conclusions  The fossil sequence supports contemporary observations indicating that access to open grassland is crucial to maintaining large Cape mountain zebra subpopulations. Although fynbos is abundant throughout the historic range of the Cape mountain zebra, fossil evidence suggests that such vegetation is unlikely to support dense populations. It has been suggested that the acquisition of agricultural lands that were historically converted to open grasslands for livestock could promote Cape mountain zebra population growth. Results presented here support this management option, as the open grasslands in these converted landscapes likely approximate the vegetation structure during latest Pleistocene, when grasslands were widespread and grazing ungulates abundant.

Microbial community dynamics in a seasonally anoxic fjord: Saanich Inlet, British Columbia

Dissolved oxygen concentration plays a major role in shaping biotic interactions and nutrient flows within marine ecosystems. Throughout the global ocean, regions of low dissolved oxygen concentration (hypoxia) are a common and expanding feature of the water column, with major feedback on productivity and greenhouse gas cycling. To better understand microbial diversity underlying biogeochemical transformations within oxygen-deficient oceanic waters, we monitored and quantified bacterial and archaeal community dynamics in relation to dissolved gases and nutrients during a seasonal stratification and deep water renewal cycle in Saanich Inlet, British Columbia, a seasonally anoxic fjord. A number of microbial groups partitioned within oxygen-deficient waters including Nitrospina and SAR324 affiliated with the delta-proteobacteria, SAR406 and gamma-proteobacteria related to thiotrophic gill symbionts of deep-sea clams and mussels. Microbial diversity was highest within the hypoxic transition zone decreasing dramatically within anoxic basin waters and temporal patterns of niche partitioning were observed along defined gradients of oxygen and phosphate. These results provide a robust comparative phylogenetic framework for inferring systems metabolism of nitrogen, carbon and sulfur cycling within oxygen-deficient oceanic waters and establish Saanich Inlet as a tractable model for studying the response of microbial communities to changing levels of water column hypoxia.

Macrozooplankton Community Dynamics in Relation to Environmental Variables in Willapa Bay, Washington, USA

Willapa Bay is a large, economically and ecologically important estuary on the Washington coast, USA for which the zooplankton community has not previously been studied. Thus, in 2006 and 2007, six stations within Willapa Bay were sampled biweekly for macrozooplankton, chlorophyll, and various abiotic variables to elucidate the processes underlying community composition and dynamics. Non-metric multidimensional scaling identified water temperature and upwelling values as major factors defining two distinct temporal communities. High densities and a community dominated by oceanic species (Calanus pacificus, Centropages abdominalis) marked the winter season, while summer (or the upwelling season) was dominated by estuarine species (Palaemonidae, Clevelandia ios). Smaller scale changes in the community were characterized by variation in chlorophyll a concentration and salinity and were marked by the presence of other taxa (Neotrypaea californiensis, Mysidae). These results point to the importance of physical processes, including the import of marine organisms and retention of estuarine organisms, in the structuring of the macrozooplankton community in Willapa Bay.

Zooplankton community dynamics in relation to the seasonal cycle and nutrient inputs in an urban tropical estuary in Brazil

Micro- and mesozooplankton were studied in the Sergipe estuary, northeastern Brazil, in order to assess the temporal variability in abundance and biodiversity under stressed conditions (urban pollution). Zooplankton samples and abiotic data were collected at one station during a full tidal cycle in July 2001 and in February 2002, corresponding to the rainy and dry seasons, respectively. The salinity regime was euhaline-polyhaline. Phosphate and dissolved oxygen were higher in July 2001, and nitrite, nitrate and ammonia in February 2002. Chlorophyll-a concentrations were low as a result of light limitation, with 1.18 +/- 0.88 microg x m(-3) in February and 1.53 +/- 1.48 microg x m(-3) in July. Fifty-nine zooplankton taxa were identified. Microzooplankton were abundant, mainly the tintinnid Favella ehrenbergii, and ranged from 18,649 ind x m(-3) in July to 678,009 ind x m(-3) in February. Mesozooplankton ranged from 1,537 ind x m(-3) in July to 37,062 ind x m(-3) in February and were dominated by barnacle nauplii in July and by copepods in February. The cluster analysis by taxa revealed the existence of three distinct groups: resilient species, characteristic of estuarine areas and occurring during all the year; species mainly more abundant in July (indicators of a healthier environmental condition); and species more abundant in February (tolerant to poor water quality).

Ants show the way Down Under: invertebrates as bioindicators in land management

The sight of land managers poring over ant checklists is a regular occurrence in Australia, where ant monitoring has been successfully applied to a wide range of land-use situations. The robustness of ants as ecological indicators has been consistently demonstrated, and is supported by an extensive understanding of their community dynamics in relation to disturbance. Despite the widespread recognition of the value of terrestrial invertebrates as bioindicators, the use of ants represents one of the few examples where invertebrates are widely adopted in land management as indicator organisms, as opposed to being consigned to the “too hard” basket. The use of invertebrates as bioindicators in land management will always require specialist expertise and a substantial investment in resources. However, research in Australia shows that invertebrate monitoring does not require comprehensive surveys, and that it is possible to simplify sampling and processing without compromising indicator performance. This should...

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Phytoplankton biomass and community dynamics in the lake pont‐chartrain estuary of southeast louisiana, usa: effects of light and nutrients upon seasonal and spatial patterns

A yearlong study (2002–2003) was conducted in the Lake Pontchartrain Estuary (LPE) of Southeast Louisiana in order to examine the temporal and spatial variability of phytoplankton biomass and community dynamics in relation to nutrients, light climate and other abiotic parameters. Variability was assessed through a north‐south transect across the estuary and at five of the major tributaries of the LPE at bi‐weekly intervals. Phytoplankton pigmentation was analyzed by HPLC and used to calculate biomass (as chlorophyll a) and to determine the relative abundances of phylogenetic groups and taxa (via CHEMTAX). Microscopic analyses of select samples were used to verify the efficacy of the CHEMTAX method in the waters of the LPE. Water‐column up‐/down‐welling irradiance (PAR) and colored dissolved organic matter (CDOM) measurements were used to characterize the light climate. Results indicate that LPE phytoplankton biomass and community composition are: 1) highly variable at the spatial and temporal scales of this study, 2) can significantly impact the light field of the LPE, and 3) are influenced by macro‐nutrient ratios.

A three-year time series of elemental and biochemical composition of organic matter in subtidal sandy sediments of the Ligurian Sea (northwestern Mediterranean)

Variations in organic matter composition and microphytobenthic biomass were examined in the surface sandy sediments at a water depth of 10 m in the Gulf of Marconi (NW Mediterranean Sea) over a three year period. Seasonal changes in elemental (organic C and total N) and biochemical (lipids, proteins, carbohydrates) composition of sediment organic matter as well as Chla were assessed in order to provide information about the origin and fate of sedimentary organic matter, the contribution of microphytobenthic biomass, seasonal and interannual variations of food quantity and quality, and factors related to food availability. Data obtained in this three-year study revealed that organic matter determined with a muffle furnace is clearly an overestimate of the organic content of the sediment and is thus of little significance for benthic ecologists studying community dynamics in relation to food availability. Labile organic matter, utilized to estimate the food potentially available for benthic consumers, accounted for only a small percentage (on average less than 10%) of total organic C. The highest labile fraction was observed in spring, whereas minima were recorded in winter. Analysis of elemental and biochemical composition of organic matter showed an inverse relationship between amount of organic matter and its potential availability to consumers; small quantities of high-quality organic matter were replaced by large quantities of refractory material. The labile portion was mostly microphytobenthic (65% of the labile carbon). Protein: carbohydrate ratios were low and confirmed the role of proteins as a potentially limiting factor for consumers. Significant differences in nutritional quality of the sediment organic matter were observed from year to year, changes due to the increase in specific labile compound content.

Community dynamics in relation to management of heathland vegetation in Scotland

The paper describes studies of post-fire succession in heathland vegetation in N.E. Scotland, dominated by Calluna vulgaris. A preliminary model (Legg, 1978) suggested good agreement between simulation of succession on the basis of a Markov chain and observations of stands at different stages of development after burning, at least in the earlier stages. Vegetation transitions are currently being recorded in permanent plots on burnt areas. First results confirm the view that (a) the post-fire succession has the properties of a Markov process, (b) this type of model remains valid when constructed from records of actual transitions, rather than data obtained by inference from evidence of transition. Comparing successional events in stands where, at the time of burning, the Calluna population was in pioneer-, building-, mature-and degenerate phases, shows that transition matrices generally agree with the Markov hypothesis, but not in the case of stands where Calluna was degenerate when burnt. The composition of establishing vegetation 1 year after fire is not confined to species normally associated with the early stages of succession, but reflects the composition of the stand before burning. Redevelopment after fire is described in terms of an initial floristic composition of species with strategies permitting early re-establishment, selected by the recurrence of the fire factor. Subsequent transitions represent changes in their relative abundance due to differing growth properties and competitive interactions. This interpretation applies only under conditions of recurrent incidence of fire (normally once in 10–15 yr). If fire does not recur, Calluna stands pass into the degenerate phase, where changes in the nature of relay floristics may come into play (e.g. with tree colonization).