Macrofaunal Abundance Research Articles

Effect of Temporarily Opening and Closing the Marine Connection of a River Estuary

The lower Rio Grande is a river-dominated estuary that serves as the border between Texas, USA, and Tamaulipas, Mexico. River estuaries encompass the section of the river influenced by tidal exchange with the Gulf of Mexico, but the connection with the Rio Grande is intermittent and can be temporarily open or closed. During the 4.8-year study period, the river mouth was closed 30% of the time, mostly during average or dry climatic conditions, with the temporary closing of the river mouth being linked to hydrology. When the Rio Grande estuary is closed, salinity is low (1.5 psu compared to 4.8 psu when open), nitrate plus nitrite are low (4.4 μM compared to 31.5 μM when open), and ammonium is high (9.6 μM compared to 4.3 μM when open), but chlorophyll is similar (20 μg/L compared to 21 μg/L when open). Benthic macrofaunal abundance and biomass are higher when the river mouth is closed: 16,700 individuals m−2 and 3.3 g m−2 compared to 8800 individuals m−2 and 2.4 g m−2 when the Rio Grande river mouth is open. Benthic macrofaunal community structure is divided into two groups: chironomid larvae and Oligochaeta dominated when the river mouth was closed, whereas polychaetes Mediomastus ambiseta and Streblospio benedicti dominated when the river mouth was open. The implications of these results for managing freshwater flows are that the open and closed conditions each have a characteristic benthic macrofaunal community that is strongly influenced by system hydrology.

Patterns of seasonal population dynamics of soil macrofauna in meadow phytocenoses in the volga-kama reserve

The aim of our study was to reveal patterns of soil macrofauna abundance variation during vegetation season. The studies were carried out in Russia, Volga-Kama reserve. The latter is divided into two part – Raifa (55.900330, 48.723119) and Saraly (55.308186, 49.239262). We sampled macrofauna their in 4 biotopes. Additionally buffer zone was investigated: 2 biotopes under anthropogenic impact. In each biotope, the spring and autumn abundance was estimated for three years. In the Saralinskii section of the reserve, in most cases, it differed insignificantly. In the Raifa section earthworms abundance declined toward autumn slightly. In buffer zone, there was a tendency to decrease in abundance by autumn, which, apparently, is associated with anthropogenic influence.

Persistent organic pollutants influence the marine benthic macroinvertebrate assemblages in surface sediments of Nayband National Park and Bay, Northern Persian Gulf, Iran.

Macroinvertebrate communities have been influenced by chemical substances, originated from petrochemical developments, that caused many problems in the marine biota. This study investigated the surface sediments of Nayband National Park and Bay (northern Persian Gulf) for polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) in terms of their distribution, source, and impacts on benthic macroinvertebrate assemblages. To this end, a total of 180 surface sediment samples from 20 stations were collected using Van-Veen grab sampler during winter 2018. The concentration of PAHs, TPHs, total organic carbon (TOC). and total organic matter (TOM) were evaluated, and grain size measurements were conducted on sediment samples in this study. Benthic macroinvertebrates were then identified in terms of presence and distribution. The results indicated that coarse granulometric fractions of sands were prevalence in all samples stations. The total concentration of PAHs ranged from 47.57 to 657.68ng/g and TPHs 5.72 to 42.16µg/g dw. The risk of ΣPAHs and TPHs in the sediments was relatively low to moderate according to the sediment quality guidelines. Analysis of the results revealed a significant negative correlation between ΣPAHs (R-value = - 0.917; P < 0.01), TPHs (R-value = - 0.849; P < 0.01) and macrofaunal abundance. Findings demonstrated that the species richness and abundance were at the lowest levels in stations where concentrations of PAHs, TPHs, TOC, and TOM were in the highest values, suggesting that these contaminants could negatively influence the benthic organisms in Nayband National Park and Bay. The results of correspondence analysis (CA) and principal component analysis (PCA) analysis showed that sedimentary habitats in Nayband National Park and Bay are being negatively affected by PAHs and TPHs, released from Pars Special Economic Energy Zone (PSEEZ). Moreover, the marine biotic index (AMBI) and Shannon-Weiner Diversity (H') results suggest that Nayband National Park and Bay can be classified as slightly to moderate polluted area. In conclusion, Northern Persian Gulf is significantly affected by oil industry developments and petrochemical activities. The unique ecosystem like Nayband National Park and Bay has been in a cautious status in terms of the PSEEZ pollutants and the levels of PAHs and TPHs concentration, warning that urgent environmental programs should be considered to protect the diversity and ecology of this valuable marine systems.

Cumulative effects of long-term anthropogenic impacts on resident fish communities in subarctic fishing harbours

Ecosystems perceived to have sustained historical human pressure from multiple stressors are often considered to be degraded. Diversity and abundance of marine macroflora and macrofauna were observed at 17 harbour sites in Newfoundland (Canada) over four consecutive years (2008–2011), to determine cumulative effects of long-term anthropogenic impacts on coastal marine biota in small fishing harbours. A Principal Component Analysis was applied to evaluate the relative effects of physical harbour characteristics (harbour shape, size, and orientation), and those directly associated with anthropogenic influence (current and historical human population size, human landscape “footprint”, and operating capacity of the local fishing industry), on marine vegetation, fish, and invertebrate macrofauna. The first three principal components explained 77% of the cumulative variance of the physical harbour and anthropogenic variables. PC1 was dominated by variables associated with human use, and site depth; PC2 was associated with physical site orientation and the cumulative wharf length; and PC3 was associated with long-term use and harbour area. The densities of cod (Gadus spp.) and crab species increased significantly along the gradient of human impact metrics, while winter flounder (Pseudopleuronectes americanus), cunner (Tautogolaborus adspersus) and shorthorn sculpin (Myoxocephalus scorpius) decreased. Sessile fauna diversity and density, and flora percent cover correlated with long-term use and harbour area. Species densities changed in response to cumulative effects of long term human settlement near harbours, but prominent species were ubiquitous in these coastal ecosystems.

Ecosystem function responses to nutrient enrichment mediated by mud content in soft sediment habitats

ABSTRACT Estuaries are threatened with increasing sedimentation and nutrients, however research is limited on the interaction of these stressors on ecosystem functions. A field experiment adding nitrogen (N) fertiliser at high (600 g N m−2) and medium (150 g N m−2) concentrations and control plots was established in two sandy and two muddy sites (mud content 0–15%) to investigate context dependency of nitrogen enrichment on nutrient cycling and primary production. There was a significant interaction of mud x treatment on ammonium (NH4 +) fluxes. High N-addition plots had 133x greater dark NH4 + efflux than controls in muddy sediments, compared to 17x greater dark NH4 + efflux in sandy sediments. Net primary production increased with mud content, while photosynthetic efficiency of the microphytobenthos (GPPchl-a ) decreased above 4% mud. Mud content also affected the bivalve, Austrovenus stutchburyi (>30 mm), macrofaunal abundance and functional groups, and their influence on nutrient cycling. Thus minor increases in mud can alter the ecosystem response to nutrient enrichment directly through changes in sediment properties and indirectly by affecting the bivalves and macrofauna that influence these processes. This study highlights how multiple stressors interact to predispose estuaries to tipping points.

Land-use intensification reduces soil macrofauna biomass at the community but not individual level

Land-use intensification and climate change are main threats to the abundance and diversity of soil macrofauna. However, little is known about their biomass in response to these concurrent drivers. Here, we investigated the biomass responses of soil macrofauna along a land-use intensity gradient of five land-use regimes (i.e., from extensively-used grassland to conventional cropland) under two climate scenarios (ambient vs. future). We found that land-use intensification (but not climate change) significantly reduced soil macrofauna biomass at the community rather than individual level. Further, the community structure of soil macrofauna based on total biomass data varied with land-use type (i.e., grasslands vs. croplands). Collectively, our findings suggest that land-use intensification can negatively shift the community biomass patterns of soil macrofauna consistently under both ambient and future climates in agroecosystems.

The impact of cumulative stressor effects on uncertainty and ecological risk

To enable environmental management actions to be more effectively prioritized, cumulative effects between multiple stressors need to be accounted for in risk-assessment frameworks. Ecological risk and uncertainty are generally high when multiple stressors occur. In the face of high uncertainty, transparent communication is essential to inform decision-making. The impact of stressor interactions on risk and uncertainty was assessed using generalized linear models for additive and multiplicative effect of six anthropogenic stressors on the abundance of estuarine macrofauna across New Zealand. Models that accounted for multiplicative stressor interactions demonstrated that non-additive effects dominated, had increased explanatory power (6 to 73 % relative increase between models), and thereby reduced the risk of unexpected ecological responses to stress. Secondly, 3D-plots provide important insights in the direction, magnitude and gradients of change, and aid transparency and communication of complex stressor effects. Notably, small changes in a stressor can cause a disproportionally steep gradient of change for a synergistic effect where the tolerance to stressors are lost, and would invoke precautionary management. 3D-plots were able to clearly identify directional shifts where the nature of the interaction changed from antagonistic to synergistic along increasing stressor gradients. For example, increased nitrogen load and exposure caused a shift from positive to negative effect on the abundance of a deposit-feeding polychaete (Magelona). Assessments relying on model coefficient estimates, which provide one effect term, could not capture the complexities observed in 3D-plots and are at risk of mis-identifying interaction types. Finally, visualising model uncertainty demonstrated that although error terms were higher for multiplicative models, they better captured the uncertainty caused by data availability. Together, the steep gradients of change identified in 3D-plots and the higher uncertainty in model predictions in multiplicative models urges more conservative limits to be set for management that account for risk and uncertainty in multiple stressor effects.

Fast improvement of macrofauna communities and soil quality in plantain crops converted to agroecological practices

Plantain (Musa paradisiaca AAB) is one of the main staple food crops in tropical areas, particularly in the Caribbean region. Therefore, supporting a sustainable production of plantain in this zone is crucial to secure food and to provide income to millions of people. We hypothesized that agroecological practices based on multi-functionality and biodiversity and that preserve soil should i) increase macrofauna abundance, ii) enhance soil chemical fertility, iii) improve soil physical structure, iv) reduce plant infestation by parasitic nematodes, and v) immediately achieve similar yield as in conventional systems. For this purpose, we compared plantain conventional and agroecological systems at the farm scale. The agroecological system consisted in a combination of three innovations: i) inputs of vermicompost to replace mineral fertilizers, ii) use of healthy planting material and iii) use of a mulching of living crop to control weeds. Ten months after the plantation, soil macrofauna abundance had doubled and taxonomic richness had increased by 45% in the agroecological system. In addition, soil structure was improved in the agroecological system (52% of biogenic aggregates in the agroecological system vs. 21 % in conventional systems), as well as the abundance of free-living nematodes associated to plantain roots increased by 73 % in the agroecological system. The abundance of Radopholus similis, one of main plant parasitic nematodes, decreased in the agroecological system. Moreover, the agroecological system achieved similar crop yield level than conventional systems. Agroecological practices are thus an efficient option to allow a fast transition from conventional to environmentally friendly cropping systems.

Soil macrofauna and microbial communities respond in similar ways to management drivers in an irrigated maize system of Colorado (USA)

The adoption of conservation agriculture has gained considerable attention due to growing interest in managing soil biological diversity and overall soil health. However, there is limited understanding of how practices such as conservation tillage and residue retention affect soil biota across different spatial scales and are associated with alterations to other soil properties. In this study, we examined changes in soil physicochemical properties, soil macrofauna, and microbial communities at two soil depths (0–10 cm, and 10–20 cm) in a 6-year field experiment manipulating tillage and maize residue management. The following treatments were included in the experiment: no-till with residue retention; no-till with residue harvest; conventional tillage with residue retention; and conventional tillage with residue harvest. Macrofauna taxa were identified and estimated visually, while bacterial and fungal communities were identified and analyzed using high throughput sequencing and multivariate statistics including non-metric dimensional scaling and indicator species analysis. Soil physicochemical properties measured include soil carbon and nitrogen, soil moisture, permanganate oxidizable carbon, available soil phosphate, pH, electrical conductivity and aggregate stability. Residue retention increased macrofauna abundance and diversity across soil depths and tillage treatments. Fungal diversity was also highest under residue retention in the topsoil (0–10 cm), while bacterial diversity was generally higher under conventional tillage. Residue retention was the main driver of macrofauna and microbial community composition, while an interaction between tillage and residue management indicated that the effect of tillage on microbial communities was most pronounced when residues were retained. Soil carbon and nitrogen, aggregate stability, permanganate oxidizable carbon, soil moisture content, available soil phosphate and soil electrical conductivity were all enhanced under residue retention in the topsoil. Indicator species analysis suggested that macrofauna taxa belonging to Annelida, Aranaea and Chilopoda together with bacterial phyla Fibrobacteres and fungal phyla Rozellomycota were indicators for no-till combined with residue retention, while Coleoptera, Spirochaetae and Basidiomycota were indicators for conventional tillage with residue retention. Multivariate analyses suggested that total macrofauna abundance, soil carbon and pH were strongly associated with bacterial and fungal community composition in the topsoil layer. Co-inertia analysis indicated significant covariation between soil physicochemical, macrofauna, bacterial and fungal datasets, suggesting a strong association between different soil parameters and cascading effects of management on multiple soil properties. Our findings demonstrate that residue retention enhances soil biological, physical and chemical properties and that communities of soil macro- and microorganisms tend to respond in similar ways to these management interventions.

Land use effects on soil macrofauna communities in a mountainous region of southwest Guizhou, China

An experiment to compare the effects of land use types on soil and macrofauna characteristics was conducted in a mountainous region of southwestern China. Soil physical and chemical properties and soil macrofauna were investigated in four land use types: natural grassland, mixed pasture of Dactylis glomerata L. and Trifolium repens L., mixed pasture of Holcus lanatus L. and Trifolium repens L., and cropland planted with annual Brassica napus L. and Zea mays L. rotation. The results showed that natural grassland, mixed pasture and cropping increased soil pH (23.0%–36.0%), soil organic matter (69.1%–73.9%, except the cropland with a decrease of 18.9%), total nitrogen (346.2%–738.5%), available nitrogen (389.9%–482.7%), available phosphorus (61.9%–303.6%) and available potassium (326.2%–481.4%). The taxonomic richness of macrofaunal communities was lower in the mixed pasture and cropped land than in natural grassland, with the Shannon’s index and Menhinick index being negatively related to soil organic carbon content. The mixed pasture maintained the abundance and diversity of soil macrofauna. The short-term cessation of utilization and management facilitated the restoration of soil macrofaunal communities. This study shows that pasture/grazing or leaving fallow for a year after cropping were able to better sustain macrofaunal communities in this mountainous region.

Community Structure of Benthic Macrofauna and the Ecological Quality of Mangrove Wetlands in Hainan, China

Few studies have systematically assessed the ecological status of mangrove wetlands following the stress of anthropogenic activities in China. This study investigated the spatial and seasonal distribution of benthic macroinvertebrate communities and assessed the ecological quality of mangrove habitats on an island scale in Hainan, China (containing the third largest mangrove area of China and the highest mangrove species richness). For the benthic macrofauna community structure, a total of 102 macrobenthic taxa belonging to 50 families were identified, with Crustaceans, Molluscs, Polychaetes, and Oligochaeta having relative abundances of 52.3%, 36.1%, 10.8%, and 0.8%, respectively. Decapoda and Gastropoda dominated the benthic community abundance. Non-metric multidimensional scaling and an analysis of similarities revealed significantly different macroinvertebrate assemblages among the regions during the two seasons. The South mangroves had the lowest macrofauna species numbers, biodiversity, richness, and abundance. The macrofaunal species richness, Shannon index, Margalef index, abundance, and biomass markedly affected by region and season. As indicated by the biotic indices AMBI (AZTI’s Marine Biotic Index) and M-AMBI, more than half of the mangrove habitats on Hainan Island were slightly to heavily disturbed and had poor to moderate ecological quality. Our results recommend long-term monitoring for evaluating the quality status of mangrove wetlands and avoiding extensive land-use conversion of mangroves. Holistic approaches considering ecological characteristics and combining information on both floral and faunal functionality would contribute to the effective management and conservation of mangroves in disturbed areas.

Positive effects of the decrease of hydraulic dredging due to the SARS-CoV-2 pandemic on benthic fauna and clam harvesting in the northern Adriatic (Mediterranean Sea)

The Northern Adriatic Sea is historically subjected to intensive bottom trawling and hydraulic dredging for clam harvesting, which are known to have deleterious effects on benthic habitats. In order to gather information on the destructive impact of hydraulic dredging, we investigated the abundance and assemblage composition of soft-bottom macrofauna in a coastal area of the North Adriatic Sea (Mediterranean Sea), by comparing the year before and the year after the reduction of the fishing effort imposed by the SARS-CoV-2 pandemic. Our results indicate that macrofaunal assemblages changed significantly in abundance and composition. While bivalves doubled their abundance, other opportunistic scavenger taxa decreased or disappeared. Despite dredging intensity decreased more than 50% in 2020, the harvesting of Chamelea gallina increased from 18,706 tons in 2019 to 19,092 tons in 2020. Overall, it could be concluded that the decrease in clam fishing effort imposed by the lockdown resulted in an increase of the yearly clam harvesting. Our study points out that the recovery of soft-bottom macrofaunal assemblages due to the long-term decrease of clam harvesting has potentially important benefits, and that the establishment of long fishing stops, or of fishery restricted areas / marine protected areas could lead to a more sustainable fishery and the potential increase of the clam fishery yields.

The macrofaunal metropolis in the sediments around the first‐ever deep‐sea alligator fall

AbstractThe maintenance of high diversity in deep‐sea sediments is often hypothesized to be a result of heterogeneity in disturbance and carbon availability creating long‐lived patches of unique communities. Deep‐sea food falls are known to contribute to this patchiness, influencing the beta‐diversity of soft‐bottom communities through varying effects of enrichment and disturbance. Previous food fall work has centered on large (&gt;1000 kg, e.g., whales) or small (0–10 kg, e.g., kelp, fish, wood) food parcels, leading to the hypothesis that only the largest persist long enough to impact sediment communities. The effect of intermediately sized (10–1000 kg) carcasses on sediment macrofauna communities remains poorly understood. Here, we deployed an individual Alligator mississippiensis carcass (19.5 kg) as organic enrichment to an otherwise food‐poor landscape at 2034 m in the northern Gulf of Mexico. Sediment cores collected at three distances from the alligator fall following decomposition were used to describe changes in macrofauna abundance and alpha‐ and beta‐diversity. We found that the carcass enriched nearby sediments with up to three times more carbon than background sediments. This carbon enrichment near the carcass did not influence species richness but did correlate with higher abundance and a suite of species unique from background communities. Our findings suggest that the food fall size threshold above which enrichment of local sediments occurs may be lower than previously thought, as we demonstrate that an intermediately sized (19.5 kg) food fall can contribute carbon and promote beta‐ and thus gamma‐ diversity of the infaunal benthos.

Impact of hypersaline brines on benthic meio- and macrofaunal assemblages: A comparison from two desalination plants of the Mediterranean Sea

Growing water demands and decreasing water supplies are exacerbating water scarcity, which is one of the challenges for sustainable development. Desalination is expanding worldwide, particularly in the Mediterranean region and plants discharge at sea large amounts of hypersaline brines, which might have consequences on marine life. We report the results of the effects of brine discharge on sediments' biogeochemistry and benthic fauna (meiofaunal and macrofaunal abundance, diversity, taxonomic composition) of two desalination plants of the Mediterranean Sea, characterized by different desalination capacity and different environmental conditions. Brine discharge causes accumulation of organic matter and alteration of its biochemical composition in sediments downstream of the discharge point and along the direction of the main current, but only within few meters. The responses of faunal assemblages depend on the characteristics of the plants, the brine discharged and the consequent changes in the amount and quality of trophic resources. We conclude that direct and indirect impacts of desalination on benthic fauna, although of local interest, can reach a larger spatial scale depending on the amount of the brine produced and the hydrodynamic conditions. Therefore, future plants to be truly eco-sustainable should assess case-by-case the potential impacts of brine discharge on marine habitats.

Benthic macrofauna of Spartina alterniflora marshes and nearby unvegetated tidal flats of Paranagua Bay (SE Brazil)

The composition and distribution of benthic macro fauna in Spartirui alterniflora marshes and nearby unvegetated tidal flats of Paranagua Bay (SE, Brazil) were investigated. Samples were taken along a salinity and physical gradient, from the inner to the outer bay. The bay was divided into sectors according to its physico-chemical and faunal characteristics. Salt marshes were affected by the gradient, with the tallest formations developing in the mesohaline sector and the lowest ones in the euhaline sector. Macrobenthic associations were also affected, with the mesohaline sector presenting a low species richness of predominantly epibenthie forms. In this sector, the composition and abundance of benthic macrofauna of the salt marshes and unvegetated flats were distinct. Species richness of the polyhaline sector, particularly of the infaunal taxa, was higher than that of the mesohaline sector. Differences between the fauna of marshes and flats became increasingly evident towards the euhaline, high energy sector, characterized by the highest species richness along the bay. Benthic associations from marshes and unvegetated flats were clearly structured by the salinity and physical gradient. Although salt marsh and flats present a relative homogeneity in physico-chemical parameters, the composition and abundance of associated benthic fauna can vary widely, particularly in poly- and euhaline sectors.

Soil Macrofauna Abundance and Taxonomic Richness under Long-Term No-Till Conservation Agriculture in a Semi-Arid Environment of South Africa

Soil macrofauna are a critical component for ecosystem function and strongly affect production sustainability. The effect of fertiliser management practices, in different cropping systems, on soil macrofauna communities remains poorly understood in semi-arid to arid regions. The objective of this study was to investigate the effect of tillage practices i.e., no-till (NT), rotational tillage (RT) and conventional tillage (CT) and nitrogen fertiliser application rates (0, 100 and 200 kg/ha N) (urea) on abundance and order diversity of soil macrofauna in a maize continuous monocropping system. The sampling of macrofauna in the trial was conducted in April 2019, August 2019 and March 2020 using 25 cm × 25 cm × 25 cm steel monoliths in randomly selected positions, and this was replicated four times. The study found a significant (p &lt; 0.05) increase in the abundance of soil macrofauna in NT (127 ind/m2) and RT (110 ind/m2) compared to CT (51 ind/m2) treatment. The abundance of macrofauna was also negatively affected by increasing the rate of fertiliser, with 0, 100 and 200 kg/ha resulting in 133, 94 and 62 ind/m2. Orders Haplotaxida and Diplopoda were found to be sensitive to increases in the fertiliser application rate. Haplotaxida (48.4%) was the most abundant order, followed by Coleoptera (18.2%). Other orders included Diplopoda (9.2%), Gastropoda (6.3%), Isoptera (4.7%), Chilopoda (4.7%), Araneae (4%), Hymenoptera (3.2%), Orthoptera (0.9%) and Dermaptera (0.3%). No-till (NT) and rotational tillage (RT) with mulch favoured the establishment of various macrofauna communities in the studied cropping system.

Macrofauna and Nematode Abundance in the Abyssal and Hadal Zones of Interconnected Deep-Sea Ecosystems in the Kuril Basin (Sea of Okhotsk) and the Kuril-Kamchatka Trench (Pacific Ocean)

The Kuril Basin and the Kuril-Kamchatka Trench are two interconnected deep-sea ecosystems both located in one of the most highly productive regions of the world’s oceans. The main distinguishing features of these deep-sea ecosystems are the low oxygen concentration in the near-bottom water in the Kuril Basin, and the high hydrostatic pressure in the trench. We investigated the abundance of meio- and macrobenthic nematodes and macrofauna on the Kuril Basin floor (depths of 3,300–3,366 m) and in the Kuril-Kamchatka Trench area (depths of 3,432–9,539 m), as well as the influence of some environmental factors on the quantitative distribution of bottom fauna. This was not studied so far. The study also focused on the species composition and quantitative distribution of Polychaeta and Bivalvia, which were dominant in abundance among macrofaunal samples. The main factors influencing the quantitative distribution of macrofauna and nematodes were depth, oxygen concentration, and structure of bottom sediments. The Kuril Basin bottom communities are characterized by a high abundance of nematodes and macrofauna, a high species richness of polychaetes, and a pronounced dominance of small-sized species of Polychaeta and Bivalvia, which are probably more tolerant to low oxygen concentrations. Compared to the Kuril Basin, the Kuril-Kamchatka Trench area (at depths of 3,432–5,741 m) had a more diverse and abundant macrofauna, and a very high abundance of meio- and macrobenthic nematodes. In the trench (at depths more than 6,000 m), the diversity of macrofauna and the abundance of macrobenthic nematodes decreased, while the abundance of macrofauna increased with increasing depth. On the trench floor, the macrofaunal abundance was highest due to the high density of populations of several bivalve and polychaete species, apparently adapted to the high hydrostatic pressure on the trench floor. Obviously, the high primary production of surface waters supports the diverse and abundant deep-sea bottom fauna in the studied areas of the northwestern Pacific. Furthermore, a large number of animals with chemosynthetic endosymbiotic bacteria were found in the bottom communities of the Kuril Basin and the Kuril-Kamchatka Trench. This suggests a significant contribution of chemosynthetic organic carbon to functioning of these deep-sea ecosystems.

Influence of Structure of Detrital Food Webs on Fusarium Head Blight of Winter Wheat

Conventional methods for Fusarium head blight (FHB) control are ineffective. A better understanding of the mechanisms linking the abundance of Fusarium species in soil before winter wheat flowering and mycotoxin content in mature grain may help to improve the effectiveness of methods for FHB control. In this study, we established a field experiment aimed to trace the impact of three types of organic mulch with different C:N ratios on the structure of detrital food webs and the manifestation of winter wheat FHB. T2-toxin content in grain was significantly higher in N-poor treatment (52.1 ± 0.2 µg g−1) compared to N-rich treatment (40.4 ± 1.6 µg g−1). The structure of detrital food webs in the studied treatments changed significantly after mulch addition; the abundance of soil saprophages and mycophages increased up to 50%. Based on the results of mixed-effects modeling, the abundance of herpetobionts and soil mesofauna were positively associated with an increase in Fusarium biomass in grain. The increase in the content of T2-toxin in the grain was associated with an increase in the abundance of earthworms and phytophagous macrofauna in the soil. Results suggest the existence of a previously undescribed mechanism for FHB infection by transfer of pathogenic spores by soil invertebrates, while the content of mycotoxins in grain can be triggered by the grazing activity of soil phytophagous invertebrates.

COVID-19 Pandemic Lockdown: An Excellent Opportunity to Study the Effects of Trawling Disturbance on Macrobenthic Fauna in the Shallow Waters of the Gulf of Gabès (Tunisia, Central Mediterranean Sea).

This study describes for the first time in the central Mediterranean Sea the effects of bottom trawling on macrobenthic fauna in tidal channels of the Kneiss Islands in the Gulf of Gabès, Tunisia. Following a BACI protocol, two control stations (protected by artificial reefs) and two trawled stations (impacted stations) were sampled during a period with the absence of bottom trawling activity (the COVID-19 pandemic lockdown period from March to May 2020) and during a trawled period. Although bottom trawling had no impact on sediment composition, this anthropogenic activity reduced the concentration of dissolved oxygen and had a noticeable effect on water column turbidity. The absence of trawling led to a significant increase in biomass, number of species, and abundance of total macrofauna. This illustrated the negative effect of trawling activity in shallow waters and the high resilience of macrobenthic communities of the tidal ecosystem of the Kneiss Islands. In the future, it would be very important to control the use of this destructive fishing gear due to its negative impact on the marine habitat and macrofauna, which represents essential prey for fishes and birds living in this protected area.

Influence of scattered trees in grazing areas on soil properties in the Piedmont region of the Colombian Amazon.

Trees dispersed in grazing areas are contribute to the sustainability of livestock systems. The interactions between trees and soil are ecological processes that allow the modification of the biology, fertility, and physics of the soil. This study was aimed to assess the influence of dispersed trees in pastures on soil properties in grazing areas for dual-purpose cattle systems in the Piedmont region of the Colombian Amazon. The work was done in grazing areas with scattered trees at the Centro de Investigaciones Amazónicas CIMAZ–Macagual in Florencia—Caquetá—Colombia. We evaluated the effect of five tree species, Andira inermis, Bellucia pentámera, Guarea Guidonia, Psidium guajava and Zygia longifolia, on soil properties (up to 30 cm soil depth) under and outside the influence of the crown. Under the tree crown, three points were systematically taken in different cardinal positions. This was done at a distance corresponding to half the radius of the tree crown. The sampling points in the open pasture area (out of crown) were made in the same way, but at 15 m from the crown border. The ANOVA showed significant interaction (P < 0.0001) between tree species and location for macrofauna abundance up to 30 cm soil depth. For this reason, we performed the comparison between locations for each tree species. Chemical soil variables up to 10 cm soil depth only showed interaction of tree species-location for exchangeable potassium (P = 0.0004). Soil physical soil characteristics up to 30 cm soil depth only showed interaction of tree species-location at 20 cm soil depth (P = 0.0003). The principal component analysis for soil properties explained 61.1% of the total variability of the data with the two first axes. Using Monte Carlo test, we found crown effect for all species. Trees help to control exchangeable mineral elements that can affect the soil, potentiate basic cations such as magnesium and potassium, increase the abundance of soil macrofauna; but some trees with high ground level of shade in grazing areas could increase soil compaction due to the greater concentration of cattle in these areas.