Changes In Nematode Communities Research Articles

Nematodes as bioindicators of soil health in different land uses in the São Francisco River Valley, Brazil

Summary Brazilian Caatinga is one of the most diverse, seasonally dry, tropical forests of the world and is threatened by strong land use pressure and poor protection. One way of understanding changes in the soil conditions caused by anthropogenic activities is using the nematode assemblages as potential bioindicators. This study analysed changes in nematode communities in three different types of land use (natural forest-CA, natural area with accumulation of salts-SS, and agricultural growing areas, such as cover crops-CC for cattle and fruit trees-IC) in the Caatinga, in the sub-median region of the São Francisco River Valley (SFRV), Pernambuco, northeastern Brazil. We recorded a total of 63 262 nematode individuals, representing 42 genera, belonging to 23 families. Nematode abundance, diversity and maturity indices were highest in the CC and lowest in the SS. Among the nematode trophic groups, bacterivores, omnivores + predators and plant parasites were significantly affected by type of land use. Different soil properties were related to the differences in taxonomic composition among the natural and agricultural areas, accounting for 26.6% of the total variation. In general, our results indicate that soil salinisation and desertification in the natural areas, as well as soils subjected to cover crops and fruit tree production, significantly influenced the composition of nematode communities in the São Francisco River Valley.

Effects of Experimental Warming and Canada Goldenrod Invasion on the Diversity and Function of the Soil Nematode Community

Both global warming and alien plant invasion can affect the biotic communities in the soil. Most studies are focused on the soil microbial community, but little is known about how global warming, along with alien plant invasion, affects the diversity and function of the soil nematode community. In this study, the individual and interactive effects of experimental warming and Canada goldenrod (Solidago canadensis L.) invasion on soil nematode communities were measured. Experimental air warming, in combination with different levels of S. canadensis invasion, were applied. The results showed that S. canadensis invasion significantly increased chao1, maturity, and structure indexes of the nematode community by 31.44%, 25.57%, and 329.3%, respectively, and decreased the basal index by 48.70% (all p < 0.05). Only the Simpson index was affected by the interaction between warming and S. canadensis invasion. Warming enhanced the S. canadensis invasion effect on the soil nematode community. The changes in nematode community were correlated with shifts in nutrient availability and resource stoichiometry, as well as microbes in the soil. These findings demonstrated that global warming and S. canadensis invasion may, directly and indirectly, alter the soil nematode community, which may considerably affect the functioning of underground food webs.

Soil nutrient and nematode community changes in response to hardwood charcoal application

ABSTRACT A one-time, large application of biochar (charcoal) could increase soil carbon (C) content and improve overall soil quality. It is known that nematodes have effects on soil organic matter and nutrient cycling and are plant diseases; moreover, nematodes affect nutrient mobilization in C-rich soil conditions; however, information is scant on the effect of biochar addition on nematode communities. Therefore, the objective of this field study was to evaluate the influence of sugar maple hardwood biochar on soil nematode communities and assess the relation among soil nematode communities and soil nutrient concentrations. Nematode communities were sampled and identified in soils without biochar application and soil amended with an application of 8% by weight (equivalent to 160 Mg ha−1). The application of 8% biochar did not change the abundance of nematodes but affected some nematode communities. Compared to the unamended soil, biochar-amended soil had lower plant-parasitic nematode populations and higher abundance of predatory nematodes. The Shannon diversity index (H’) was lower, and the maturity index (MI) was higher with a mean value of 2.38 with biochar addition compared to 2.21 in unamended plots. Higher soil acidity and addition of substantial amounts of magnesium, calcium, potassium, and manganese in the biochar-amended soils were recorded after biochar application.

Functional organization of soil nematode communities of spruce in primary ecosystems

Based on the study of the structural and functional organization of nematode communities of primary ecosystems, it is possible to determine the degree of transformation of secondary ecosystems, because anthropogenic activity leads to changes in their formation. Nematode communities of indigenous ecosystems have preserved their evolutionary-formed structural and functional organization and the ratio of trophic groups. This ensures the integrity and stability of biogeocenoses. Therefore, such groups have a significant bioindication role. The research was conducted within the Skolivski Beskydy National Nature Park. A mixed beech forest was selected as the reference plot. For two years, we have been taking samples of litter and soil under the spruce canopy. Nematodes were separated from the soil using the Berman method on a Kempson device. De Man indices were used to determine species. Based on the division of nematodes into trophic groups according to G. Yeats, we calculated the part of each of them in the litter and soil. 
 The number of nematodes in the litter increases from the upper horizon to the humus. In freshly fallen leaves the variety of nematodes (horizon L) is the least. In 2014 and 2015 in the upper horizon of the litter at different times of the year, the number of phytonematodes varied from 22 to 28 %, in the enzymatic horizon from 30 to 35 %, and in the humus horizon from 38 to 47 % of the total number of phytonematodes. The three litter horizons have the largest number of omnivorous nematodes, which is about two-thirds of the total number of the community with the largest quantity in summer. The part of predatory nematodes in spring and autumn is about 10 %, and in summer increases to 15 %. Bacteriovorus nematodes make about 18 % in spring, 25 % in summer, and 22 % in autumn, with a predominance in the F-horizon of litter. The part of fungivorous nematodes in all horizons of litter is approximately 5 %, with a predominance of the total number of this trophic group in the enzyme horizon.
 Omnivorous nematodes are represented mainly by species of the genus Eudorylaimus and Aporcelaimellus, carnivorous nematodes belong to the genera Prionchulus, Iotonchus, Tripyla, and bacteriophages are dominated by nematodes of the genera Plectus and Acrobeloides, and the group of fungivorous is mainly represented by species of the genus Aphelenchoides. Our results were later used to compare changes in nematode communities in derived ecosystems.

Taxonomic profiling of individual nematodes isolated from copse soils using deep amplicon sequencing of four distinct regions of the 18S ribosomal RNA gene.

Nematodes are representative soil metazoans with diverged species that play crucial roles in nutrient recycling in the pedosphere. Qualitative and quantitative information on nematode communities is useful for assessing soil quality, and DNA barcode-mediated taxonomic analysis is a powerful tool to investigate taxonomic compositions and changes in nematode communities. Here, we investigated four regions (regions 1–4) of the 18S small subunit ribosomal RNA (SSU) gene as PCR targets of deep amplicon sequencing for the taxonomic profiling of individual soil nematodes. We determined the sequence variants (SVs) of 4 SSU regions for 96 nematodes (total 384 amplicons) isolated from copse soils and assigned their taxonomy using the QIIME2 software with dada2 or deblur algorithm and the SILVA database. Dada2 detected approximately 2-fold more nematode-derived SVs than deblur, and a larger number of SVs were obtained in regions 1 and 4 than those in other regions. These results and sufficient reference sequence coverage in region 4 indicated that DNA barcoding using a primer set for region 4 followed by dada2-based analysis would be most suitable for soil nematode taxonomic analysis. Eighteen SSU-derived operational taxonomic units (rOTUs) were obtained from 68 isolates, and their orders were determined based on the phylogenetic trees built by four regional sequences of rOTUs and 116 nematode reference species as well as the BLASTN search. The majority of the isolates were derived from three major orders Dorylaimida (6 rOTUs, 51.5% in 68 isolates), Rhabditida (4 rOTUs, 29.4%), and Triplonchida (7 rOTUs, 17.6%). The predicted feeding types of the isolates were fungivores (38.2% in total nematodes), plant feeders (32.4%), and 14.7% for both bacterivores and omnivores/predators. Additionally, we attempted to improve the branch structure of phylogenetic trees by using long nucleotide sequences artificially prepared by connecting regional sequences, but the effect was limited.

Using high-throughput sequencing quantitatively to investigate soil nematode community composition in a steppe-forest ecotone

The analysis of nematode community composition by high throughput sequencing (HTS) has attracted much attention because of its advantage for throughput, high resolution and coverage. However, we are still not clear whether the sequenced data will result in similar estimates in the absolute abundance and biomass of the nematode community as shown by morphological analysis. To better compare these two methods, we investigated the nematode community structure and composition from a steppe-forest ecotone. Based on high-throughput sequencing and morphological identification approaches, we compared the abundance and biomass of total nematodes as well as different feeding groups in meadow steppe, transition ecotone and forest ecosystems. Our results suggested that the absolute abundance conversion from the relative abundance obtained by HTS present the same ecological conclusions in the nematode community composition and trophic structure with that of the morphological analysis. The plant-parasite index was significantly higher in meadow-steppe than those in the transition ecotone and the forest ecosystems. The Shannon-Wiener diversity, evenness and the observed richness obtained by the two methods showed similar patterns (MS > TS > FS) among the three ecosystems. The observed richness obtained by HTS was higher than that of morphological analysis. However, the biomass of bacterivores obtained by the two methods exhibited a weak correlation. Despite the limitations both approaches have, our results suggested that HTS can be used quantitatively to understand changes in nematode communities in the steppe-forest ecotone from the abundance aspect. The improvement of the database used by the HTS may further enhance the accuracy of ecological information obtained by molecular techniques.

Changes in Nematode Communities and Functional Diversity With the Conversion of Rainforest Into Rubber and Oil Palm Plantations

Focusing on nematodes and their well-developed indices of community, ecosystem structure and function, we investigated the effects of the conversion of rainforest into rubber and oil palm plantations in Sumatra, Indonesia. Land use did not affect the total abundance of litter- and soil-dwelling nematodes, neither in riparian nor in well-drained sites. However, the rainforest nematode community differed from communities in plantations, with differences in litter being more pronounced compared to soil. In litter, fungivores and nematodes with short generation time (c-p2) increased in monoculture plantations, while that of bacterivores, herbivores, and nematodes with longer generation time and higher sensitivity to disturbances (c-p3) decreased. This indicates higher environmental pressure on nematodes in monoculture plantations than in rainforest. In soil of monoculture plantations, bacterivores and c-p3 nematodes decreased while herbivores increased. This suggests that the damage of plants by nematodes in oil palm plantations exceeds that in rainforest. Overall, nematode functional diversity indices suggest that the stability of the decomposer community is higher in rainforest compared to monoculture plantations. Importantly, functional diversity indices were much more meaningful than nematode abundance. Further, changes with land use manifested more in litter than in soil, reflecting that nematode communities in soil are buffered against changes in land use and associated environmental conditions. Therefore, to fully assess changes in the structure and functioning of decomposer systems with changes in land use, the litter layer, which often receives little attention, requires more careful consideration.

How does an invasive Heracleum sosnowskyi affect soil nematode communities in natural conditions?

Summary We analysed the effect of the invasive perennial plant Heracleum sosnowskyi on soil nematode communities and diversity, and plant species composition, by comparing invaded and non-invaded (control) areas in natural conditions. Invasion of H. sosnowskyi caused significant shifts in plant species composition, which subsequently modified nematode assemblages. Stress-sensitive omnivores, fungivores and root-biomass-dependent obligate plant parasites best reflected changes in soil nematode communities under the influence of H. sosnowskyi invasion. The negative effect of H. sosnowskyi was most evident on Aphelenchus, Tylencholaimus, Geocenamus, Helicotylenchus, Pratylenchus, Tylenchorhynchus and Aporcelaimellus. Our results indicate that significant changes in the herbaceous layer after H. sosnowskyi invasion in ecosystems where H. sosnowskyi eventually became dominant impacted soil nematode communities but did not affect nematode diversity. This was in contrast to the habitats where a solitary plant of H. sosnowskyi grew and no significant changes in nematode communities were observed.

Windstorms as mediator of soil nematode community changes: Evidence from European spruce forest

Summary Nematode communities in a Norway spruce forest in High Tatra National Park, Slovakia were monitored for the period of several years (2006 and 2013). Unfortunately, in May 2014 natural windstorm damaged the forest. This disastrous event, together with preliminary obtained results allowed us to compare the direct impact of windstorm damage of forest habitat on soil nematode assemblages. The forest destruction by windstorm had a significant effect on the total nematode abundance, the abundance of omnivores and herbivores, as well as the nematode species diversity. The most dominant species, representing 55 % of the total nematode fauna, in the plot studied were Acrobeloides nanus followed by Malenchus exiguus, Filenchus vulgaris, Plectus communis, Plectus parvus and Tylencholaimus mirabilis. The abundance of bacterivorous signifi cantly increased after the windstorm, meanwhile the abundance of omnivores, fungivores, and herbivores ectoparasites and epidermal/root hair feeders showed an opposite trend. Of the evaluative indicators, Shannon species diversity (H’spp), maturity index (MI), maturity index 2-5 (MI2-5), sigma maturity index (ΣMI), enrichment index (EI) and structure index (SI) decreased significantly after windstorm. The EI and SI indexes characterized soil ecosystems before windstorm (2006 - 2013) as maturing with low or moderate disturbance, but soil ecosystems shortly after the windstorm (2014) were degraded and nutrient depleted. This also corresponded with graphical display of metabolic footprints characteristics of soil food web. Overall, the nematode communities differed significantly before and after forest damage. These results suggest the role of nematode communities as indicators of environment condition quality or its disruption.

Fertilization influences the nematode community through changing the plant community in the Tibetan Plateau

Fertilization greatly impacts grassland ecosystems as it alters plant communities, soil fauna, and microbiota although few studies have looked at these interactions on the Tibetan plateau. Soil nematodes are ideal bioindicators for the status of below-ground ecosystems. To explore how nematode communities are impacted by the use of fertilization, we studied the top layer of soil in land that had been fertilized annually with diammonium phosphate for over 10 years. We tested effects of long term fertilization treatment at 300, 600 kg ha−1 yr−1 (F300, F600) compared to unfertilized control (F0) on soil nematode community at the 0–15 cm depth. Soil samples for analysis of nematode community were collected on September 2012 and on September 2013. We show that fertilization was associated with increased plant and microbial biomass, and decreased plant biodiversity. Fertilization increased microbial biomass C and N; grass biomass and total plant biomass, but decreased plant species richness, plant community biodiversity and the biomass of sedges, legumes and forbs. Fertilization increased nematode communities increased over the entire course of the study. We show that the amount of fertilizer used and the duration of its use significantly impacted the dynamics and composition of nematode communities. The changes in nematode community were associated with both changes in soil factors and shifts in the plant community that were caused by fertilization. According to the structural equation model (SEM), fertilization had strong effects on soil microorganisms and plant community composition, whereas plant community was the main determinant of nematode community changes. Our findings highlight the importance of soil fertilization in regulating both plant and soil fauna communities, and provide a better understanding of the responses of plants and soils to fertilization and the linkages between structure and functioning of above-ground and below-ground in the Tibetan Plateau.

Organic farming practices result in compositional shifts in nematode communities that exceed crop-related changes

Intensification of conventional agriculture has resulted in a decline of soil ecosystem functioning. Organic agriculture intends to manage soil biota in a manner that is more geared towards adequate cycling of nutrients with minimal losses. Ecological interpretation of agricultural practices-induced shifts in primary decomposers, bacteria and fungi, is non-trivial due to their enormous biodiversity. Bacterivorous and fungivorous nematodes feed selectively on these microorganisms, and we intended to test whether farming system effects are mirrored in compositional changes in nematode communities. Therefore, we analysed the impact of three farming systems, conventional (ConMin), integrated (ConSlu) and organic (Organic), on nematode communities in the southeastern part of The Netherlands on a sandy soil with 3–5% organic matter. Effects of each farming system were assessed for four different crops (barley, maize, pea or potato) by a series of taxon-specific quantitative PCRs (qPCR). Changes in community structure analysed by nonmetric multidimensional scaling (NMDS) showed that organic farming resulted in specific shifts in nematode community composition exceeding crop-related assemblage shifts. Three out of thirteen quantified nematode taxa showed significant farming system effects. Strongest effects were observed for the (putative) bacterivore Prismatolaimus, which was relatively common in Organic fields and nearly absent in ConMin and ConSlu fields. A reverse effect was observed for Pristionchus; this necromenic bacterivore and facultative predator made up about 21% and 7% of the total nematode community in respectively ConMin and ConSlu fields, whereas it was nearly absent from Organic fields. The observed farming system effects suggest that specific nematode taxa might be indicative for the impact of farming practices on soil biota.

Changes in nematode communities in different physiographic sites of the condor seamount (north-East atlantic ocean) and adjacent sediments.

Several seamounts are known as ‘oases’ of high abundances and biomass and hotspots of biodiversity in contrast to the surrounding deep-sea environments. Recent studies have indicated that each single seamount can exhibit a high intricate habitat turnover. Information on alpha and beta diversity of single seamount is needed in order to fully understand seamounts contribution to regional and global biodiversity. However, while most of the seamount research has been focused on summits, studies considering the whole seamount structure are still rather poor. In the present study we analysed abundance, biomass and diversity of nematodes collected in distinct physiographic sites and surrounding sediments of the Condor Seamount (Azores, North-East Atlantic Ocean). Our study revealed higher nematode biomass in the seamount bases and values 10 times higher in the Condor sediments than in the far-field site. Although biodiversity indices did not showed significant differences comparing seamount sites and far-field sites, significant differences were observed in term of nematode composition. The Condor summit harboured a completely different nematode community when compared to the other seamount sites, with a high number of exclusive species and important differences in term of nematode trophic diversity. The oceanographic conditions observed around the Condor Seamount and the associated sediment mixing, together with the high quality of food resources available in seamount base could explain the observed patterns. Our results support the hypothesis that seamounts maintain high biodiversity through heightened beta diversity and showed that not only summits but also seamount bases can support rich benthic community in terms of standing stocks and diversity. Furthermore functional diversity of nematodes strongly depends on environmental conditions link to the local setting and seamount structure. This finding should be considered in future studies on seamounts, especially in view of the potential impacts due to current and future anthropogenic threats.

The effect of cover crops on plant parasitic-nematodes of sugarcane

Plant-parasitic nematodes cause significant yield losses to sugarcane crops in South Africa. The currently available chemicals for nematode control are both expensive and potentially detrimental to the environment. Various alternative crops have been reported to reduce the numbers of plant-parasitic nematodes. Mindful of this, we evaluated 27 cover crops in pot trials to assess their host status to important plant-parasitic nematodes of sugarcane. All of the crops tested in pots hosted significantly lower numbers of Pratylenchus than did sugarcane. Crops such as cowpeas, tomato and grazing vetch were good hosts for Meloidogyne and would not be good choices as part of a sugarcane rotation system in heavily-infested soils. Conversely, crops such as oats, wheat, forage peanuts and marigolds reduced numbers of Meloidogyne. Velvet beans increased the abundance of Helicotylenchus, a beneficial nematode genus. A field trial was also conducted to study the effect of different cover cropping sequences. Our results show that changes in nematode communities occurred within three months of growing these crops and often remained low for the duration (the remaining 15 months) of the crops' growth. Nematodes such as Pratylenchus and Tylenchorhynchus were significantly lowered and remained so for the duration of the trial.

Spatial variation in biodiversity and trophic structure of soil nematode communities in a subtropical savanna parkland: Responses to woody plant encroachment

Woody plant encroachment into grasslands generally increases spatial heterogeneity of soil properties and processes and creates “islands of fertility” beneath woody canopies. However, little is known regarding the potential for these changes to influence spatial variation in soil fauna. We quantified population sizes, biodiversity, and trophic structure of soil nematode communities in a savanna parkland where woody plant clusters developed in grassland during the past century. Total nematode density was constant across transects from centers of woody clusters into grasslands. Family richness and Simpson's Dominance Index indicated nematode communities in grasslands and grassland/cluster edges were significantly more diverse than positions within the woody clusters. Relative densities of all nematode trophic groups changed significantly along the transect. Bacterivores nearly doubled in relative density from grassland (35%) to cluster centers (60%), apparently in response to higher concentrations of soil microbial biomass in wooded areas. Relative densities of plant parasitic nematodes decreased along transects from grasslands (35%) to centers of woody clusters (10%), implying decreased nematode herbivory in woody clusters despite much higher root biomass there. The structure index indicated nematode communities within woody clusters were more simplified than those in grassland and edge communities due to reductions in densities of omnivores and predators. Although nematode densities were lower at 10–20 than 0–10 cm, nematode community characteristics were generally similar between soil depths. Changes in nematode community and trophic structure described here could influence biogeochemical processes, species interactions, and successional processes in regions where woody plants are encroaching into grasslands.

Soil nematode community changes associated with compost amendments

Abstract Five composts (C1: fresh olive pomace, straw, chicken manure, urea; C2: fresh olive pomace, lettuce residues, cow manure, straw, sawdust; C3: sewage sludge, municipal green residues; C4: grass, leaves, tree branches, soil; C5: by-product from penicillin production (mycelium), straw and sawdust) were tested in a pot experiment to investigate their short-term effect on the nematode community of a grassland soil. Composts were mixed with soil at the rates of 10, 25, 50 and 100 g (kg soil)–1 and barley was sown in each potting mixture after a 2-month decomposition period. Nematodes were extracted from each pot 5 months after barley sowing, identified at genus level and grouped into bacterial, fungal and root fungal feeders, predators, omnivores and plant parasites. Bacterial feeders, predators and omnivores were favoured by amendments with composted penicillin substrate and partly by compost from olive pomace, whereas composts from green wastes and sewage sludge suppressed these trophic groups except for predators. All compost treatments suppressed fungal feeders as well as significantly reducing the density of plant-parasitic nematodes compared with non-amended soil. The highest suppressiveness on plant-parasitic nematodes was found for the composts from urban green residues, penicillin substrate and olive pomace plus cow manure. Suppressive effect was hypothesised to be related to ammoniacal nitrogen content of the composts. Composts from fungal mycelium or olive pomace seem to be the most suitable for application in nematode management strategies due to their low impact on beneficial trophic groups.

Soil nematode community changes associated with windfall and wildfire in forest soil at the High Tatras National Park, Slovak Republic

Abstract The paper presents research findings on the influence of windfall and wildfire on nematode communities in Lariceto-Piceetum forest in the High Tatras in Slovakia. Comparison was made of an intact (REF), affected and extracted (EXT), non-extracted (NEX) and burnt (FIR) forest stand. A total of 55 species belonging to 36 genera were found. The EXT locality harboured the majority of the identified species, but the highest abundance of nematodes was observed in the FIR locality. Bacterial feeders were the dominant trophic group in all investigated plots. In the REF bacterial feeders were followed by root-fungal feeders, fungal feeders and omnivores, in the EXT by omnivores and plant parasites, in the FIR by omnivores and root-fungal feeders and in the NEX by fungal feeders and omnivores. The MI and SI were higher in the REF and the EXT compared to those in the FIR and the NEX, the highest B/F ratio was observed in the FIR and the highest EI was found in the REF. We can conclude that disturbance of forest vegetation and soil has had a clear and demonstrable impact on nematode communities.

Soil nematode community succession in stabilised sand dunes in the Tengger Desert, China

In order to examine how nematodes respond to sand dune succession after stabilisation and reclamation techniques, nematode communities were investigated in sand dunes stabilised for 0, 16, 26, 43, and 51 years in the Tengger Desert, China. Our results revealed that the abundance of nematodes; the proportion of fungivores, omnivores, and predators; maturity index (MI); Shannon index; evenness; and structure index (SI) were affected significantly by the age of stabilised sand dunes, and were correlated with soil physical and chemical properties to different degrees. There were differences in nematode abundance, the proportion of fungivores, Shannon index, and evenness between the shifting dunes and the stabilised dunes, but not within the different succession stages of the stabilised dunes. MI showed a tendency to increase with dune age and SI increased significantly with dune age. MI, and especially SI, could act as robust indicators of stabilised sand dune succession. Redundancy analysis using data on nematode community composition showed that shifting sand dunes were clearly separated from stabilised sand dunes, and younger sand dunes stabilised for 16 and 26 years were also separated from older dunes stabilised for 43 and 51 years to a lesser degree. The results indicated that changes in nematode communities could predict initial sand dune stabilisation due to the planting of artificial vegetation, and clearly differentiate sand dune succession accompanied by vegetation succession and variation of soil properties.

Impacts of ocean acidification and burrowing urchins on within-sediment pH profiles and subtidal nematode communities

Rising carbon dioxide levels in the atmosphere will affect the ocean carbonate system, resulting in a predicted future decrease in the pH of seawater by 0.3-0.5 units. To investigate whether the presence of a burrowing urchin, Echinocardium cordatum, might influence the impact of ocean acidification on subtidal sediment pH profiles and nematode community structure an experiment was conducted using subtidal sediment, with urchins present or absent and seawater at either pH 8.0 (ambient) or 7.5. The presence of urchins, and a reduction in pH, both had significant effects on within-sediment pH profiles. Where urchins were present sediment profiles were more consistent and sediment pH was lower than that of the overlying seawater. There were significant differences in nematode abundance between treatments. The primary effect was a higher abundance of nematodes in replicates with urchins in natural seawater. All treatments had similar nematode community structure and diversity. Ocean acidification could therefore lead to changes in nematode communities in subtidal sediments affected by burrowing urchins.

Short-term changes in nematode communities from an abandoned intense sand extraction site on the Kwintebank (Belgian Continental Shelf) two years post-cessation

We investigated short-term changes (two years) in nematode communities (density, diversity, biomass and community composition) in an area on the Kwintebank (Belgian Continental Shelf) that was closed for sand extraction activities and compared these patterns to nematode community characteristics from another area on the Kwintebank were sand extraction was still ongoing. Six stations were sampled in 2003 and 2004 and nematode community composition and univariate measures of diversity were compared with values obtained during the extraction period and with a “pre-impact situation” sampled in 1978. Although nematode density, diversity and biomass did not change two years after cessation of the exploitation, nematode community composition did and was more stable than in the extracted site. This is attributed to the absence of continuous disturbances associated with the extraction activities such as the creation and filling up of dredge furrows. As a consequence of the typical life history traits of nematodes, recovery seems to follow different pathways when compared to macrobenthic recovery from the same impact.

Changes in nematode communities at the long-term sand extraction site of the Kwintebank (Southern Bight of the North Sea)

We investigated the long-term effects of sand extraction activities on the nematode communities from the Kwintebank. Although changes in nematode community composition cannot be completely uncoupled from natural processes, we suggest that the morphological changes in the sandbank and physical disturbance associated with the dredging activities indeed affected nematode community composition. Nematode diversity did not change since the start of the extraction activities but nematode community composition changed significantly. The SIMPER routine identified predatory nematodes to be important for the within group similarity at the start of the exploitation, while similarity in 1997 and 2001 was determined by the contribution of deposit feeding nematodes. In addition, long nematodes, vulnerable to physical disturbance became less important. These changes are attributed to long term changes in sediment characteristics in combination with additional short-term disturbances by the creation and filling of dredge furrows which are related to the extraction activities.