Macrofaunal Abundance Research Articles

Hydrodynamic Conditions Effects on Soft-Bottom Subtidal Nearshore Benthic Community Structure and Distribution

This study assesses the impacts of wave action and freshwater outflow on soft-bottom benthic macrofauna spatial distribution and temporal stability along the highly exposed French Basque coast. Sediment characteristics and macrofauna abundance have been seasonally investigated during two years for nine stations located at the same (6 m) depth and spread over three subtidal sites showing distinct exposure levels. Wave climate has been determined through an operational numerical model. A total of 121 taxa were recorded, gathered in three main faunal assemblages, as revealed by classification and ordination methods. Non-parametric multivariate multiple regression (distance-based linear model) showed that the variations in macrofaunal distribution can be explained by hydrodynamic conditions. Wave exposure strongly linked to estuarine inputs were the most relevant abiotic factors influencing distributional patterns and functional structure as described by biological traits analysis. Despite the influence of these abiotic variables affecting sedimentary dynamics, seasonal stability was observed in macrobenthic assemblages composition suggesting an ability to recover from natural disturbances such as (e.g.) winter storms. In this way, these results provide baseline knowledge for future ecosystem and resource management in shallow subtidal areas strongly exposed to swell and freshwater outflow where soft-bottom macrozoobenthic communities are less frequently studied.

Soil macrofauna associated with cover crops in an Oxisol from the southwest of Piauí state, Brazil

ABSTRACT: The soil macrofauna is fundamental for the maintenance of soil quality. The aim of this study was to characterize the soil macrofauna under different species of cover crops, including monoculture or intercropping associated to two types of soil management in the southwest region of Piauí state. The study was carried out in an Oxisol (Latossolo Amarelo, according to Brazilian Soil Classification System) in the municipality of Bom Jesus, Piauí, distributed in 30 m2 plots. Testing and evaluation of the soil macrofauna were conducted in a 9 × 2 strip factorial design, with combinations between cover crops/consortia and soil management (with or without tillage), with four replications. Soil monoliths (0.25 × 0.25 m) were randomly sampled in each plot for macrofauna at 0‒0.1, 0.1‒0.2, and 0.2‒0.3 m depth, including surface litter. After identification and counting of soil organims, the relative density of each taxon in each depth was determined. The total abundance of soil macrofauna quantified under cover crops in the conventional and no-tillage system was 2,408 ind. m-2, distributed in 6 classes, 16 orders, and 31 families. The results of multivariate analysis show that grass species in sole cropping systems and no-tillage presents higher macrofauna density, in particular the taxonomic group Isoptera. No-tillage also provided higher richness of families, where Coleoptera adult were the second more abundant group in no-tillage and Hemiptera in conventional tillage.

Soil macrofauna diversity and population dynamics in Indian Himalayan agroecosystems

Soil macrofauna diversity in Himalayan mountain agroecosystems has received negligible attention despite people’s dependence on soil fertility that determines crop yield for their sustenance. This study was carried out with the objective to determine differences in soil macrofauna taxonomic groups and abundance with soil depth (0–30 cm) in irrigated and non-irrigated wheat and rice crops of two dominant Himalayan mountain agroecosystems. At both the sites, a total of 11 macrofauna groups and 23 families were recorded. Macrofauna population across both crop seasons for non-irrigated fields was significantly greater (P < 0.05) than in irrigated fields. Macrofauna population significantly differed (P < 0.001) with soil depth and significantly declined with increasing soil depth (P < 0.001). The top soil (0–10 cm depth) contributed over 80% of the total macrofauna population. Macrofauna diversity in non-irrigated fields (H′ = 2.10) was greater than in irrigated fields (H′ = 1.86), but β diversity was greater in irrigated fields (1.67 vs 1.76). The two agroecosystem types significantly differed (P < 0.05) with soil depth and crop season. On the basis of presence or absence, the macrofauna groups were categorised as (i) present in soil year-round but exhibiting high density during warm and wet rainy season and (ii) present in soil only during the warm and wet rainy season. The non-irrigated fields had greater abundance of Coleoptera, Dermaptera, Hemiptera and Isoptera than the irrigated fields. This study highlights that the Himalayan mountain crop fields host a rather diverse and abundant macro-invertebrate community that should be efficiently used to promote soil fertility.

Influence of organic and mineral fertilizers on edafic fauna in Luvisol cultivated with sesame

The aim of this study was to evaluate the abundance and diversity of soil macrofauna under the influence of organic fertilization with goat manure compared to NPK fertilization in a Luvisol with two sesame cultivars. The experiment was conducted in Alagoinha - PB, under field conditions at the Experimental Station of the State Enterprise for Agricultural Research of Paraiba SA (Empresa Estadual de Pesquisa Agropecuária da Paraíba S.A. - EMEPA), approximately 1.24 miles away from the city. The design utilized was in random blocks with the treatment groups: T1: goat manure as organic source in BRS 196 cultivar (CNPA G4), T2: goat manure as organic source in BRS Seda cultivar, T3: mineral fertilizer with NPK in BRS 196 cultivar (CNPA G4), T4: mineral fertilizer with NPK in BRS Seda cultivar, T5: No fertilization in BRS 196 cultivar (CNPA G4) and T6: No fertilization in BRS Seda cultivar, with these fertilizers based on soil analysis, totaling 24 experimental units. In assessing the ecological behavior of soil macrofauna, it was measured the total number of individuals (abundance) and wealth of faunistic groups and communities comparisons were made using the Shannon biodiversity indices (H and equitability of Pielou (e). The treatment groups with organic fertilization were more abundant and rich as well as the faunistic group Hymenoptera had the highest abundance and lower diversity and uniformity, independently of the treatment groups studied and the samplings collected. The treatment groups studied did not influence the diversity and uniformity of edafic macrofauna.

Promoting soil health in organically managed systems: a review

Soil health is an old concept receiving renewed attention. Defined as a soil’s capacity to function, soil health is composed of physical, chemical, and biological attributes. The improvement and maintenance of soil health is considered a cornerstone of organic agriculture. Although there are numerous studies that compare organic systems with conventional systems, fewer studies compare organic systems with each other to determine how best to improve soil health metrics. In this review, we focused on nine indicators of soil health (aggregate stability, water holding capacity, infiltration/porosity, erosion/runoff, nutrient cycling, organic carbon, microbial biomass, macrofauna abundance, and weed seed bank). We found 153 peer-reviewed, published studies that measured these soil health indicators in two or more organic treatments. Overall, published research focused on four key practices: (1) cover crops, (2) organic amendments, (3) rotation diversity and length, and (4) tillage. Of these, 26 studies focused on cover crops, 77 on organic amendments, 32 on crop rotations, 40 on tillage, and 22 included more than one practice. Eighty percent of the studies were conducted in the USA and Europe. We found strong agreement in the literature that roll-killed cover crops suppressed weeds better than disking and that weed suppression required high levels of cover crop biomass. Combinations of organic amendments such as composts, manures, and vermicomposts improved soil health metrics compared to when applied alone. Including a perennial crop, like alfalfa, consistently improved soil carbon (C), nitrogen (N), and aggregate stability. Soil health metrics were improved under shallow, non-inversion tillage strategies compared with conventional tillage. Despite their importance for climate change mitigation and adaptation, the effect of practices on aggregate stability and water dynamics were under-studied compared with other soil health metrics. There is a great deal of variety and nuance to organic systems, and future research should focus on how to optimize practices within organic systems to improve and maintain soil health.

Drought effects on tropical estuarine benthic assemblages in Eastern Brazil

Climate change will increase the frequency and intensity of extreme weather events with potential effects in coastal and estuarine ecosystems. During drought periods, higher salinity and temperature can directly impact estuarine benthic assemblages through physiological stress and alteration of sedimentary habitats, but these effects are poorly evaluated to date. Here we report a 14-month monitoring of benthic assemblages in a tropical estuary in the Eastern Brazil Marine Ecoregion during the severe drought period of 2015/2016. The drought in Eastern Brazil resulted in a decrease of estuarine mean sediment particle size and concurrent changes in macrofaunal benthic assemblages during the driest months. We also observed a 3-fold reduction on macrofaunal abundance with dominance of surface-dwelling Magelonid, Sternaspid, Capitellid and Oligochaeta annelids. The changes in macrofaunal structure during the severe drought also decreased the community bioturbation potential (BPc) by 5-fold, if compared to pre-drought periods. We argue that the projected increases in the frequency and severity of climatic events, such as observed during severe droughts worldwide, will greatly change the benthic fauna and their ecological functions in tropical estuarine ecosystems.

Benthic Fauna of Oga Bay (Novaya Zemlya, Kara Sea)

The benthic fauna of Oga Bay (Kara Sea, Novaya Zemlya archipelago) was studied in 2015–2016 during the R/V Akademik Mstislav Keldysh expeditions. Five grab stations at depths of 70–140 m were sampled (three grabs per station). Three macrobenthic communities consecutively replacing each other from the inner near-glacier part of the bay toward the outer slope were revealed. Concentration of suspended matter in the water column and in the near-bottom layer, caused by powerful sedimentation from the Goluboi (Oga) glacier was the main factor determining the macrobenthic communities distribution. An overall decrease in abundance, biomass and diversity of macrofauna was found in the area of glacier discharge. The community dominated by bivalve Portlandia arctica inhabits the main part of the bay. The peculiarities of the benthic communities of the Arctic glacial bays and fjords are discussed.

Influence of Seabird Colonies on Soil Macrofauna Communities at the Black Sea Coast Forests

A seabird (Phalacrocorax carbo) colony overwintering for three consecutive years in a pine forest near the Black Sea coast caused severe damage to the vegetation. The impact of excessive nutrients input from this colony increased soil acidity, N, P, Cu and S-content in soil and might therefore affect soil macrofauna. We compared the abundance of main functional trait guilds and the total abundance of soil macrofauna within impact and control pine forests. No significant difference between the sites was noted in taxonomic richness, total macrofauna abundance and abundance of mobile, belowground, phytophagous and predatory invertebrates. However, the abundance of poorly mobile, poorly mobile epibiontic, and these both traits of saprophagous macrofauna guilds was significantly higher in the control sites. We conclude that three-year wintering of a seabird colony in forest can lead to drastic changes in the macrofauna communities structure due to allochthonous input of nutrients.

Soil Macrofauna Responses to Sugarcane Straw Removal for Bioenergy Production

Sugarcane (Saccharum officinarum) residue (straw) has been identified as a promising feedstock for bioenergy production, but excessive straw removal may impair soil macrofauna and related ecosystem services. To quantify straw removal effects on abundance, richness, and diversity of soil macrofauna, four experiments were conducted in Sao Paulo state, Brazil, under different edaphoclimatic conditions. A secondary goal was to evaluate seasonal changes on soil macrofauna and identify linkages between those changes and soil chemical and physical attributes. Four straw removal treatments (NR, no removal, LR, low removal, HR, high removal, and TR, total removal) were evaluated. Macrofauna and other soil attributes were sampled within the 0- to 0.30-m depth increment. Soil macrofauna were impaired by TR with the magnitude of response being related to both edaphoclimatic conditions and management practices. Numerous interactions among seasons, straw removal rates, and soil macrofauna were found, especially for total abundance and diversity of organisms. Partial straw removal (HR and LR) may be a strategy to protect soil health and increase bioenergy production with minimal effects on soil macrofauna, although long-term experiments are needed to confirm our hypothesis. The NR treatment generally had better soil quality as indicated by greater soil moisture, macropore number, soil organic carbon (SOC) content, and soil fertility, which led to a higher abundance of most macrofauna organisms. Total removal resulted in greater soil compaction and decreased macrofauna abundance, especially in clay soils. Our findings confirm that an integrated approach using soil indicators as guidelines should be adopted to better predict sustainable straw management practices for sugarcane in Brazil.

Efectos de la calidad del agua y del sustrato blando sobre la macrofauna bentónica de la zona intermareal en la Playa Pochomil, San Rafael del Sur

Se realizó un estudio espacial y temporal de la macrofauna bentónica en la zona intermareal de la Playa Pochomil, Nicaragua, en tres sitios denominados S.A (sitio arenoso), SRR (sitio rocoso con río) y S.R (sitio rocoso), respectivamente. Al final del estudio se contabilizaron un total de 596 individuos pertenecientes a cuatro Filos (Molusca, Anélida, Artrópoda y Equinodermata). La diversidad de macrofauna bentónica calculada mediante el índice de Shannon-Weaver, refleja valores de diversidad muy bajos durante todas las épocas de muestreo. Mediante el índice de Jaccard y Morisita-Horn, se evidenció que hubo baja similitud de especies. Además, se comprobó que la temporalidad no tuvo efecto directo significativo sobre la abundancia y distribución de la macrofauna bentónica, sino que ésta fue influenciada principalmente por las características físicas de los sitios de muestreo

Motile macrofauna associated with pelagic Sargassum in a Mexican reef lagoon

Buildup of decaying pelagic Sargassum on the beaches and coasts of the Mexican Caribbean during the massive arrivals of 2015 and 2018 had detrimental impacts on the environment and tourist industry. To avoid ecological and economic impacts from massive beaching of Sargassum, it would be better to remove the pelagic algal masses while still at sea. However, out at sea, pelagic Sargassum rafts constitute an ecosystem with a diversified associated fauna and their removal could impact this fauna. We conducted a survey on the motile macrofauna associated to pelagic Sargassum rafts in the Puerto Morelos reef lagoon, Mexican Caribbean. Pelagic Sargassum was sampled with nets at 2 m, 50 m and 500 m from shore, at four sites during the months of September, October and November 2018. The 108 samples contained 10,296 individuals belonging to 32 taxa distributed over eight Phyla. The main phyla were Arthropoda (48%), Annelida (41%) and Mollusca (15%). Fish abundance was low (10 individuals) with only five species, of which three are typically associated with Sargassum rafts and two are common in seagrass meadows and coral reefs. Species composition and abundance of motile macrofauna varied with month and zone; the nearshore zone had the lowest abundance but there was no difference in the abundance of the fauna associated with rafts 50 or 500 m offshore. Three of the four most abundant species (together accounting for 89% of the individuals) were species typically associated with pelagic Sargassum, and the fourth was an amphipod that was only registered once near shore. Although more studies over larger time and spatial scales are required, these results suggest that the removal of pelagic Sargassum within the reef lagoon may not have a significant effect on local populations of motile macrofauna.

Natural and anthropogenic factors influencing abundance of the benthic macrofauna along the shelf and slope of the Gulf of Guinea, a large marine ecosystem off West Africa

Summary The West African continental margin belongs to the least known areas in terms of the ecology of benthic ecosystems. At the same time, this region is influenced by various threats associated with human activities, including industrialisation and oil excavation. Here, we analyse the abundance and distribution patterns of macrozoobenthic communities along the coast of Ghana. The material was collected in 2012 on nine transects at depths ranging from 25 to 1000 m. Over 200 quantitative samples were collected using a 0.1-m2 van Veen grab. Generally, the mean density of macrozoobenthos decreased gradually from the shallow zone (25 m: 231.4 ± 262.2 ind./0.1 m2) down to bathyal depths (1000 m: 55.4 ± 51.4 ind./0.1 m2), but we observed intermediate scale variability in distribution patterns among the transects along the Ghanaian coast. Analysis of environmental factors showed no evidence of substantial pollution, although levels of hydrocarbons, barium and some other toxic metals show some local increases at particular stations, especially on the continental slope. Cluster analysis based on Bray–Curtis similarity and abundance of higher taxonomic groups of macrofauna yielded five groups of stations, while SIMPER analysis demonstrated that polychaetes and amphipods contributed most significantly to within-group similarity. Canonical Correspondence Analysis demonstrated that PAH, THC and toxic metal levels (Ba, Cd, Pb), as well as oxygen concentration, were the most important factors structuring benthic communities.

Benthic macro-faunal abundance and diversity and sediment distribution in Akhziv submarine canyon and the adjacent slope (eastern Levant Basin, Mediterranean Sea)

The Israeli coastline is generally characterized by a broad and shallow continental shelf. Akhziv submarine canyon (ASC), in its northern reach, creates a locally unique marine ecosystem. The present study is the first to investigate the benthic macro-fauna of ASC, in order to assess its importance as a potential productivity ‘hotspot’ within its ultra-oligotrophic surroundings. Seven research cruises were conducted during 2010-2013, along ASC’s two channels and at iso-bathic control sites on the adjacent slope (AS), encompassing 8 sampling stations, at depths of 40-450 m. Bottom samples were collected by a Van Veen Grab, gravity corer and a GOMEX box corer. The infauna (≥500 µm) were counted and identified to the lowest possible taxonomic level. Sediments were analysed for grain size & composition and total organic carbon concentration. Mean benthic macro-faunal abundance (individuals/500ml ± SD) was higher inside the canyon (13.0±19.4) compared to the AS (2.9±3.3) (p=0.004), as was estimated true taxon richness (Chao1): 42.2 versus 10, respectively. Sediments’ mode grain size was found to be significantly higher in ASC’s eastern channel compared to AS (p=0.028), along with sand enrichment of up to 36%. The higher macrofaunal abundance and taxon richness may relate to a more heterogeneous sea bed provided by the higher diversity in grain size existing inside ASC. A relatively rich benthic realm, such as that observed in the ASC, may serve as a refuge for certain species and by hosting a relatively diverse assemblage, stands a better chance of adapting to changing conditions such as climate change.

Ecosystem functioning along gradients of increasing hypoxia and changing soft-sediment community types

Marine ecosystems world-wide are threatened by oxygen deficiency, with potential serious consequences for ecosystem functioning and the goods and services they provide. While the effects of hypoxia on benthic species diversity are well documented, the effects on ecosystem function have only rarely been assessed in real-world settings. To better understand the links between structural changes in macro- and meiofaunal communities, hypoxic stress and benthic ecosystem function (benthic nutrient fluxes, community metabolism), we sampled a total of 11 sites in Havstensfjord and Askeröfjord (Swedish west coast) in late summer, coinciding with the largest extent and severity of seasonal hypoxia in the area. The sites spanned oxic to anoxic bottom water, and a corresponding gradient in faunal diversity. Intact sediment cores were incubated to measure fluxes of oxygen and nutrients (NO3−, NO2−, NH4+, PO43−, SiO4) across the sediment-water interface. Sediment profile imaging (SPI) footage was obtained from all sites to assess structural elements and the bioturbation depth, and additional samples were collected to characterise sediment properties and macro- and meiofaunal community composition. Bottom-water O2 concentration was the main driver of macrofauna communities, with highest abundance and biomass, as well as variability, at the sites with intermediate O2 concentration. Meiofauna on the other hand was less sensitive to bottom-water O2 concentration. Oxygen was the main driver of nutrient fluxes too, but macrofauna as well meiofauna were also significant predictors; DistLM analyses indicated that O2 concentration, macrofaunal abundance or biomass, and meiofaunal abundance collectively explained 63%, 30% and 28% of the variation in sediment O2 consumption, NH4+flux and PO43− flux, respectively. The study provides a step towards a more realistic understanding of the link between benthic fauna and ecosystem functioning, and the influence of disturbance on this relationship, which is important for management decisions aimed at protecting the dwindling biodiversity in the coastal zones around the world.

Patterns and environmental drivers of diversity and community composition of macrofauna in the Kveithola Trough (NW Barents Sea)

The Kveithola Trough located in the NW Barents Sea is a peculiar system characterized by distinct geomorphological and environmental features which are expected to exert an important role on the distribution of benthic assemblages. In the present study we investigated for the first time the distribution of macrofaunal abundance, biomass and diversity along the Kveithola Trough. Our analysis reveals major differences of the macrofaunal assemblages along the Kveithola Trough related not only to the different morpho-depositional features but also to differences in trophic conditions. The inner part of the Kveithola Trough was characterized by the presence of opportunistic species such as Levinsenia gracilis and Maldane sarsi among polychaetas, Mendicula cf. pygmea and Yoldiella sp. among bivalves, which are known to inhabit oxygen-depleted environments and organic-enriched sediments. Results reported in this study suggest that the peculiar environmental conditions of the Kveithola Trough along with the occurrence of methane seepage in the neighbouring Storfjorden Trough in association to the Knølegga fault may exert a major selective effect on macrofaunal organisms.

A rapid, non-invasive population assessment technique for marine burrowing macrofauna inhabiting soft sediments

Population assessment techniques for soft-sediment infauna (invertebrates within the substrate) requires excavation of specimens, damaging or killing the specimen and surrounding habitat, while being time-consuming and costly. Rapid population assessments of some marine burrowing decapods have been possible by counting burrow openings to estimate abundance, and while they may be used as indicator species, these decapods are not ubiquitous to environments requiring monitoring. Additionally, the presence of other burrowing macrofauna (invertebrates living in the sediment and retained on 1 mm mesh such as clams or large worms) may reduce the efficacy of burrow openings in estimating macrofauna abundance. As such, we assessed mudflats along the north coast of British Columbia, Canada, during summer 2017 to determine if macrofauna abundances could be estimated from burrow openings on the sediment surface in regions of low (n = 1 species) and high (n = 8 species) biodiversity. Abundance could not be estimated at the low diversity sites where only one macrofaunal species created burrows. At the high diversity site, species-specific models estimating abundance from burrow openings could not be constructed; however, the total number of burrow openings observed was useful in estimating total infaunal community abundance. As such, burrow openings may not be an effective tool in assessing species-specific abundances, but may be appropriate to estimate overall community changes.

Experimental harvest in a tropical seagrass meadow leads to shift in associated benthic communities

Seagrass meadows represent key ecosystems in coastal areas worldwide, hosting a great biodiversity of associated communities and thereby providing a large range of ecosystem services. In this study we present an experimental approach to investigate the effects of seagrass losses on related macrofauna assemblages. Over a three year period, seagrass canopies were removed in experimental plots and changes in epifauna, infauna and respective functional groups were recorded. The experimental removal of seagrass leaves resulted in a decline of 74% of overall macrofaunal abundance and the loss of several taxa. The immediate response of associated communities was followed by the establishment of an alternative assemblage, characterized by an increased number of bioturbators and deposit feeders. The colonization of disturbed seagrass plots by burrowing shrimps (Callianassidae) might have hindered the reestablishment of seagrass after the removal. Our findings highlight the important role of seagrasses as habitat forming species that provide relevant functioning and services in coastal ecosystems.

Response of the soil macrofauna abundance and community structure to drought stress under agroforestry system in southeastern Qinghai-Tibet Plateau

ABSTRACTSoil macrofauna is vital for soil functions and soil-mediated processes in all ecosystems. However, environmental perturbations, such as drought, that threaten both the abundance and function of soil macrofauna remain mostly unexplored, particularly in an agroforestry system. We investigated the effects of drought on soil macrofauna abundance and vertical distribution under three different planting systems including two intercropping systems, comprising Chinese prickly ash (Zanthoxylum bungeanum) intercropped with soybean (Glycine max) (Z-G) or bell pepper (Capsicum annuum) (Z-C), and one monoculture system, comprising only Z. bungeanum (Z). Soil samples were collected at depths of 0–10, 10–20, and 20–30 cm, and soil macrofauna and chemical properties were analyzed. Soil dryness negatively affected soil macrofauna in all planting systems. Drought reduced the total macrofauna density, biomass, genera richness, and Pielou’s evenness. Additionally, drought significantly decreased density and biomass of Drawida and Eisenia but had no effect on Carabid beetles. Soil macrofauna density was highest in the Z-G intercropping system and higher at 0–10 cm than at other soil depths. These results indicate that intercropping soybean rather than bell pepper increases the abundance and biomass of soil macrofauna, and drought remarkably impacts the response of soil macrofauna to planting systems.

Mechanisms of soil macrofauna community sustainability in temperate rice-growing systems

Rice growing requires highly destructive and highly invasive field management negatively affecting soil biota and its functions. We aimed to compare taxonomic and functional trait compositions of soil macrofauna at different stages of rice cropping cycles in the three temperate rice-growing regions in Russia. Samples were collected in 2016 at four different biotopes in each region: flooded rice paddies; upland crops planted one year after flooded rice; rice paddy bunds; and relatively undisturbed seminatural control grasslands. Collected soil macrofauna were allocated to different traits according to their feeding preferences, vertical distribution, mobility and flood tolerance. The lowest macrofaunal abundance across all regions was observed in rice paddies. Cultivation of upland crops after paddy flooding consistently decreased the abundance of resident macrofauna, but not that of mobile soil macrofauna. In the upland crops, the abundance of belowground and mobile belowground macrofauna was significantly higher than that in control grasslands. The abundance of aboveground phytophages was significantly lower in the upland crops than in control sites. Flood-associated taxa showed low colonization ability after the paddies were drained. In contrast, representatives of other traits recorded in flooded fields increased their abundance at the next stage of crop rotation, demonstrating high resilience within an entire rice-growing system, including bunds. This finding indicates a high potential of seminatural grasslands and especially bunds as sources of rapid restoration of soil macrofauna functional diversity in rice-growing agroecosystems, thus maintaining the sustainability of soil food webs in the rice paddies.

Anthropogenic impact of oyster farming on macrofauna biodiversity in an eelgrass (Zostera marina) ecosystem of the English Channel

Abstract Zostera marina flourish along the west coast of Cotentin, in cohabitation with extensive oyster cultivation. In 2016, seasonal sampling was carried out based on five combinations of conditions involving vegetated and unvegetated areas, presence or absence of oyster tables and a control station without either eelgrass or oyster cultivation. The sediments consisted of muddy sandy gravel and no significant difference of sediment composition was observed between stations and seasons. A total of 147 taxa and 8404 individuals were recorded over a period of the one year with a sampling effort of 5 m2. The effects of oyster farming are relatively limited, and are not a handicap for the extension of Zostera meadows in this part of the English Channel. Nevertheless, low Taxonomic Richness and abundances characterize the tractor pathway. Macrofauna abundances, biomasses and number of eelgrass shoots are similar to those reported at other sites in the English Channel and from the North-eastern Atlantic.