Pristine Communities Research Articles

Restoration of Zoobenthic Communities and Water Quality in the River Ecosystem after a Decrease in the Level of Organic Pollution

The development of principles and methods for restoring ecological systems that have undergone intense anthropogenic impacts is one of the most important tasks of modern ecology. This work is devoted to studying the regularities of the influence of organic pollution on the structure and functional characteristics of zoobenthic communities and the degree of restoration of the pristine communities of bottom animals and the quality of the waters of the small Izhora River by bioindication characteristics. For this, the results of studies from the 1970s and 2000s were compared. Intensive organic-matter pollution influenced the structure and functioning of zoobenthos, increasing biomass and energy flow through the bottom animal communities. At the same time, the role of oligochaeta worms in the bottom communities sharply increased, the role of larvae of amphibiotic insects decreased, the species richness and biological diversity of zoobenthos declined, and the efficiency of energy transfer between trophic levels of primary and secondary consumers fell. Water quality in accordance with the values of the integrated index IPʹ corresponded to the fifth highest class of pollution (dirty). Downstream, due to self-purification processes, the water quality and ecosystem state improved slightly, but this improvement was not very significant, which indicated that the river ecosystem was not able to process excess organic matter entering the river. The introduction of wastewater treatment from organic pollutants at sewage treatment plants contributed to the restoration of the structural and functional organization of zoobenthic communities and significantly improved the state of the river ecosystem. However, a complete restoration of water quality did not occur: it improved to moderately polluted.

Organic enrichment simplifies marine benthic food web structure

AbstractFood web structure is a key determinant for community functioning and stability. Still, the architecture of trophic interactions is often ignored in assessments of stressor‐ or disturbance‐induced changes in ecological communities. We established anthropogenic structuring of trophic networks by revisiting the Pearson‐Rosenberg paradigm on changing benthic communities along gradients of organic enrichment. Using monitoring data from two sites with point‐source organic loading, acknowledging associated changes in, e.g., water chemistry, we studied network topology of soft‐sediment macroinvertebrate communities. We found that organic enrichment led to a progressive simplification of food web structure. The simplification manifested both horizontally and vertically in the web, and networks at impacted sites consisted of fewer nodes, fewer links, and had lower linkage density than more pristine communities. Contrary to our expectation, organic enrichment did not change the directed connectance of the networks, nor affect proportions of top‐level species and carnivorous taxa in the assemblages. There were, however, changes in the proportions of basal‐level and intermediate‐level nodes, which together with decreasing mean trophic height further reveal a disintegration of the trophic network. We suggest the Pearson‐Rosenberg model is expanded to include a progressive simplification of benthic food webs. Adding a dimension of interactions (in this case feeding links) to existing biodiversity assessments enhances our understanding of the consequences of environmental degradation.

The mechanistic basis of changes in community assembly in relation to anthropogenic disturbance and productivity

AbstractAnthropogenic disturbance often causes changes in communities. However, the mechanistic basis of these changes remains elusive. As all patterns in community ecology can be understood as a result of four processes (speciation, selection, drift, and dispersal), the effect of disturbance should depend on how disturbance disrupt these processes. We studied the effects of disturbance and productivity on species richness, community composition, and community dispersion (i.e., variation in community composition) in the vegetation of 120 boreal peatlands using null‐model approach to determine whether community assembly processes differ between pristine and disturbed sites. Sites represented three peatland ecosystem types, each with two levels of productivity. Half of the sites were disturbed by drainage and half are pristine. Pristine and disturbed sites showed similar species richness. However, their community composition differed indicating a directional selection due to disturbance, whereas dispersion of disturbed and pristine communities did not differ suggesting no change in the relative strength of selection and drift. Our results suggest that understanding the combination of landscape level community changes and local selection pressures is important when restoration of degraded ecosystems is undertaken.

Marine reserve recovery rates towards a baseline are slower for reef fish community life histories than biomass.

Ecological baselines are disappearing and it is uncertain how marine reserves, here called fisheries closures, simulate pristine communities. We tested the influence of fisheries closure age, size and compliance on recovery of community biomass and life-history metrics towards a baseline. We used census data from 324 coral reefs, including 41 protected areas ranging between 1 and 45 years of age and 0.28 and 1430 km(2), and 36 sites in a remote baseline, the Chagos Archipelago. Fish community-level life histories changed towards larger and later maturing fauna with increasing closure age, size and compliance. In high compliance closures, community biomass levelled at approximately 20 years and 10 km(2) but was still only at approximately 30% of the baseline and community growth rates were projected to slowly decline for more than 100 years. In low compliance and young closures, biomass levelled at half the value and time as high compliance closures and life-history metrics were not predicted to reach the baseline. Biomass does not adequately reflect the long-time scales for full recovery of life-history characteristics, with implications for coral reef management.

Comparative metagenomics reveals impact of contaminants on groundwater microbiomes.

To understand patterns of geochemical cycling in pristine versus contaminated groundwater ecosystems, pristine shallow groundwater (FW301) and contaminated groundwater (FW106) samples from the Oak Ridge Integrated Field Research Center (OR-IFRC) were sequenced and compared to each other to determine phylogenetic and metabolic difference between the communities. Proteobacteria (e.g., Burkholderia, Pseudomonas) are the most abundant lineages in the pristine community, though a significant proportion ( >55%) of the community is composed of poorly characterized low abundance (individually <1%) lineages. The phylogenetic diversity of the pristine community contributed to a broader diversity of metabolic networks than the contaminated community. In addition, the pristine community encodes redundant and mostly complete geochemical cycles distributed over multiple lineages and appears capable of a wide range of metabolic activities. In contrast, many geochemical cycles in the contaminated community appear truncated or minimized due to decreased biodiversity and dominance by Rhodanobacter populations capable of surviving the combination of stresses at the site. These results indicate that the pristine site contains more robust and encodes more functional redundancy than the stressed community, which contributes to more efficient nutrient cycling and adaptability than the stressed community.

Structural and functional recovery of microbial biofilms after a decrease in copper exposure: Influence of the presence of pristine communities

The present study aimed at assessing the recovery of phototrophic and heterotrophic biofilm communities after a decrease in copper exposure. An original experiment was designed to evaluate the possible influence of non-exposed (i.e. pristine) communities (e.g. via immigration processes) in recovery dynamics. Laboratory channels were used to study the structural and functional changes in microbial communities after a 4-week Cu exposure period in the presence and absence of pristine biofilms. When pristine biofilms were present, phototrophic communities recovered within 6 weeks, both in terms of biomass, structure and photosynthetic activity. Recovery processes were also detected using the PICT approach. In contrast, in the absence of pristine communities, all of the Cu-induced changes recorded in the phototrophic communities remained throughout the recovery period.Regardless of the presence or absence of pristine biofilms, the decrease in Cu exposure did not abolish Cu-induced changes in bacterial community structure, whereas functional recovery (based on beta-glucosidase activity) was complete in both recovery contexts.These results revealed that microbial community response to a decrease in Cu exposure differs between phototrophic and heterotrophic communities. The presence of pristine communities greatly influences the structural and functional recovery of phototrophic communities, suggesting an important role of microbial immigration processes, but have far less influence on the recovery trajectory of heterotrophic communities.

Interaction of landscape and life history attributes on genetic diversity, neutral divergence and gene flow in a pristine community of salmonids

Landscape genetics holds promise for the forecasting of spatial patterns of genetic diversity based on key environmental features. Yet, the degree to which inferences based on single species can be extended to whole communities is not fully understood. We used a pristine and spatially structured community of three landlocked salmonids (Salvelinus fontinalis, Salmo salar, and Salvelinus alpinus) from Gros Morne National Park (Newfoundland, Canada) to test several predictions on the interacting effects of landscape and life history variation on genetic diversity, neutral divergence, and gene flow (m, migration rate). Landscape factors consistently influenced multispecies genetic patterns: (i) waterfalls created strong dichotomies in genetic diversity and divergence between populations above and below them in all three salmonids; (ii) contemporary m decreased with waterway distance in all three species, while neutral genetic divergence (theta) increased with waterway distance, albeit in only two taxa; (iii) river flow generally produced downstream-biased m between populations when waterfalls separated these, but not otherwise. In contrast, we expected differential life history to result in a hierarchy of neutral divergence (S. salar > S. fontinalis > S. alpinus) based on disparities in dispersal abilities and population size from previous mark-recapture studies. Such hierarchy additionally matched varying degrees of spatial genetic structure among species revealed through individual-based analyses. We conclude that, whereas key landscape attributes hold power to predict multispecies genetic patterns in equivalent communities, they are likely to interact with species-specific life history attributes such as dispersal, demography, and ecology, which will in turn affect holistic conservation strategies.

The effects of nitrate loading on the invasive macrophyte Hydrilla verticillata and two common, native macrophytes in Florida

Rising nitrate concentrations in the water column and the spread of invasive, non-native macrophytes are two major threats to Florida's oligotrophic, freshwater ecosystems. We used a replicated mesocosm experiment to test the effects of elevated nitrate concentrations in the water on the growth of the invasive macrophyte Hydrilla verticillata and two common, native submerged macrophytes Vallisneria americana and Sagittaria kurziana. Results from this study indicate that nitrate concentrations of 1.0 mg L −1 NO 3-N in the water increased the final dry-weight biomass of H. verticillata by 2.75 times, while having no statistical effect on the growth of the two native species. Additionally, H. verticillata grew at a faster rate than the two native species in the low nitrate treatments accounting for 82% of the total biomass, indicating that it may have the capacity to invade relatively pristine communities. In waters where nitrate concentrations continue to rise, the cost of control efforts for H. verticillata may substantially increase in the future.

Shifts in species traits among North American freshwater fish assemblages: ecological homogenization?

&#x0D; &#x0D; &#x0D; &#x0D; This study examines whether the processes of species invasion and extirpation have produced distinct shifts in mean species traits of North American freshwater fish assemblages. An analysis of 54 species (29 invaders, 25 extirpated taxa) in 7 drainages revealed significant differences in maximum length, native latitudinal range size, habitat specificity, and migratory behaviour. Results suggest a pattern in which extirpated species are being replaced by larger, more environmentally tolerant species capable of occupying a broader range of habitats. Freshwater fish assemblages containing introduced generalist species may have a selective advantage over pristine communities as human-dominated landscapes continue to replace natural systems.&#x0D; &#x0D; &#x0D; &#x0D;

Invasibility of four plant communities in the Llobregat delta (Catalonia, NE of Spain) in relation to their historical stability

Presence and cover of alien plants were analysed in relation to recent naturalness changes (1956–1999) in the Llobregat delta by means of GIS techniques and field surveys. Two land cover maps of 1956 and 1999 were generated by photo-interpretation of orthoimages and they were then reclassified into naturalness classes, defined as the degree of preservation of the pristine state. The resulting naturalness maps were combined in order to obtain a naturalness change map, which was used to design field sampling in four pristine communities: reedbeds, rushbeds, halophilous scrubs and fixed dune communities. Two study areas were selected for each community and three stability regimes (stable, semi-stable and non-stable) obtained from the naturalness change map. Five vegetation inventories were performed on average in each of these areas using the classical sigmatist method. Results showed a negative relationship between stability and invasibility, with several variations between communities. No alien species were found in stable areas of all communities. Alien species number, species percentage and relative cover increased from semi-stable to non-stable regimes in reedbeds and dune communities, indicating that reversion towards the climax reduces opportunities for alien establishment in these communities. In contrast, halophilous habitats such as rushbeds and scrubs did not exhibit significant differences between semi-stable and non-stable plots, probably because saline stress makes their invasion by alien plants difficult, even under disturbance.

A reference framework for the restoration of riparian vegetation in the Western Cape, South Africa, degraded by invasive Australian Acacias

Riparian vegetation, which normally differs structurally and compositionally from surrounding vegetation, has been degraded in many parts of the fynbos biome by several species of invasive Australian Acacia . Systematic clearing of dense stands of these alien trees was initiated in 1995, and information is urgently needed to guide the restoration of riparian habitats. A problem is that degradation of these communities is so advanced and widespread that in many cases managers do not know what species to use in restoration, or what kinds of target communities to aim for. This study's aim was to provide baseline information on riparian plant community structure and composition from non-transformed habitats. Species and environmental data were recorded from 76 sites located along the headwater systems of six rivers in the southwestern part of the Western Cape province. Analysis of the data, applying multivariate classification (TWINSPAN) and ordination (Detrended Correspondence Analysis) techniques, identified four prospective plant communities: 1) a Nivenia corymbosa - Brachylaena neriifolia Community; 2) a Leucadendron salicifolium - Berzelia lanuginosa Community; 3) a Cliffortia ruscifolia - Metrosideros angustifolia Community; and 4) a Kiggelaria africana - Brabejum stellatifolium Community. These formed a continuum with only the Leucadendron and Kiggelaria communities separating in ordination space. Soil pH differed between the latter two communities, reflecting different geology. It was found that many riparian specialist species are relatively widespread. For the study area, it is concluded that where information on the historical composition of riparian communities is lacking, target communities for restoration can be defined from pristine communities with similar geology, and secondly, altitude. In all cases the target community will comprise a large proportion of widespread, predominantly resprouting, riparian species.

Diversity of Geobacteraceae species inhabiting metal-polluted freshwater lake sediments ascertained by 16S rDNA analyses.

The abundance, distribution, and phylogenetic diversity of members of the Fe(III)-reducing family Geobacteraceae were studied along a gradient of metal contaminants in Lake Coeur d'Alene, Idaho. Partial 16S rRNA gene fragments were amplified by PCR using primers directed toward conserved regions of the gene within the family Geobacteraceae. Analysis of amplicons separated by denaturing gradient gel electrophoresis (DGGE) suggested within-site variation was as great as between-site variation. Amplicons were cloned and grouped by RFLP type and DGGE migration distance and representatives were sequenced. Grouping clones with 3% or less sequence dissimilarity, 15 distinct phylotypes were identified compared to 16 distinct DGGE bands. Only 1 phylotype was recovered from all sites. This clone, B14, is most closely related to Geobacter metallireducens and constituted a greater portion of the pristine community than of the contaminated communities. A second phylotype, Q2, predominated in the contaminated communities and was notably absent from the pristine libraries. Clone Q2 presents a high degree of sequence similarity to two Geobacter spp. previously isolated from this region of Lake Coeur d'Alene. Six phylotypes were unique to the contaminated sediments, whereas two were found only in the pristine sediments. Indices of diversity (Shannon and Simpson) were consistently higher when calculated with DGGE data than when clone library data were used. Most-probable-number PCR and real-time PCR suggested that the Geobacteraceae phylotypes were spread relatively evenly across all three sites along the gradient. Our data indicate that the Geobacteraceae are diverse and abundant in Lake Coeur d'Alene sediments, regardless of metals content. These results provide insight into the ability of dissimilatory Fe(III)-reducing bacteria to colonize habitats with elevated metal concentrations, and they have important implications for the management and remediation of metal-contaminated sites.

Occurrence of Four Major Perennial Grasses in Relation to Edaphic Factors in a Pristine Community

Highlight: The ecology and phytosociology of a virgin grassland community (Virginia Park, Canyonlands National Park, Utah) have been investigated. Based on the use of C x F index, Hilariajamesii and Stipa comata are the most abundant of the four major perennial grasses. Oryzopsis hymenoides and Sporobolus cryptandrus are less abundant in decreasing order. The sites dominated by Hilaria are characterized by soils with finer texture, slightly warmer average temperature and higher surface K+ and organic matter compared to sites dominated by Stipa comata. In addition, frequency of both vascular and cryptogamic species is greater on sites dominated by Hilaria.