Faunal Density Research Articles

沼液施用对海岸带围垦麦田土壤中小型节肢动物群落的影响

土壤节肢动物群落结构是反映土壤动物多样性及土壤质量的重要指标。沼液施用对土壤结构与肥力的改变, 可能对土壤节肢动物群落的特征产生显著影响。以江苏东台海岸带连续施用沼液5年的围垦麦田为例, 研究沼液不同用量(0、100、200、300 m³/hm²)及沼液替代(0%、33%、66%、100%)化肥对土壤中小型节肢动物群落结构的影响。结果表明：各施肥管理下麦田土壤中小型节肢动物的优势类群均为前气门亚目、甲螨亚目和弹尾目, 平均分别占总捕获量的52.09%-53.33%、22.42%-23.86%和13.14%-16.51%。当沼液用量从0增加到300 m³/hm²时, 土壤动物密度增加了94%, 类群数增加约2个, 优势度指数增加9.4%(P < 0.05)。沼液66%替代化肥时, 土壤动物密度、类群数和优势度指数最高。因此, 施用沼液显著增加了土壤中小型节肢动物的密度、类群数与优势度指数。当沼液替代化肥的比例为66%时, 促进效应最佳。主成分分析表明, 无论单施沼液还是沼液替代化肥, 弹尾目、前气门亚目与甲螨亚目的响应最为敏感, 可将其作为土壤中小型节肢动物对施肥响应的指示指标。;The high dependence on chemical fertilizers driven by crop yields has posed huge risks and challenges to soil quality and ecosystem balance for decades. The reduction and substitution of chemical fertilizers has now become a national strategy for high-quality agricultural development. The organic matter of livestock and poultry manure is converted into methane under highly anaerobic conditions, and the liquid by-products (biogas slurry) and solid residues (biogas residue) are also produced. The biogas slurry is rich in nitrogen, amino acids, and various mineral nutrient elements, being an efficient alternative to chemical fertilizers. Previous studies on the application of biogas slurry mainly focused on the effects of dosage and usage on crop yield and soil properties. The impact on soil fauna communities was insufficient yet. Soil arthropods participate in soil biochemical cycles, stimulating the metabolism of fungi and bacteria and maintaining the balance of the soil ecosystem. Due to their sensitive response to habitat changes, soil arthropods are used as important indicators to reflect soil health and stability. However, there is no investigation on the changes of soil arthropod communities under the condition of biogas slurry instead of chemical fertilizers. In the present study, the effects of different dosage of biogas slurry (0, 100, 200, and 300 m³/hm²) and substitution of biogas slurry (0%, 33%, 66%, and 100%) to chemical fertilizers on soil small- and medium-sized arthropod communities were investigated in coastal reclaimed wheat fields with repeated application of biogas slurry for 5 years in Dongtai city, Jiangsu, China. The results showed that the predominant soil fauna groups in wheat field were Prostigmata, Oribatida and Collembola, accounting for 52.09%-53.33%, 22.42%-23.86% and 13.14%-16.51% of the total catches, respectively. When the amount of biogas slurry increased from 0 to 300 m³/hm², the density of soil fauna increased by 94%, the number of groups increased by about 2, and the dominance index increased by 9.4% (P < 0.05). The density of soil fauna, number of groups and dominance index arrived the highest when using 66% of biogas slurry to replace chemical fertilizers. Therefore, the application of biogas slurry could significantly increase the density, group number, and dominance index of small- and medium-sized arthropods in the soil. When the ratio of biogas slurry to replace chemical fertilizer was 66%, the promotion effect was the best. In addition, principal component analysis showed that Collembola, Prostigmata and Oribatida were much sensitive to biogas slurry application alone or biogas slurry in place of chemical fertilizers. They could be used as indicators of the response of soil small- and medium-sized arthropods to fertilization.

Megabenthic biodiversity in culturally and ecologically important coastal regions of Northern Labrador

Labrador Inuit have expressed concern about the impacts of climate change on their health and well-being and their future access to marine resources, including fisheries. This study filled important knowledge gaps identified by the Nunatsiavut Government and Inuit communities regarding benthic biodiversity and habitat structure within major geomorphology features. Marine benthic surveys were conducted in three areas of ecological, cultural, and historical significance: Hebron Fjord, Okak Fjard, and the Nain archipelago, inclusive of a polynya, using a camera sled and a baited remote underwater video system. We documented the spatial extent of megabenthic diversity components and the high densities of dominant taxa, notably tube-dwelling anemones (cerianthids), brittle stars (ophiuroids), soft corals (<em>Gersemia</em> sp.), and bristle worms (polychaetes). Species accumulation curves indicated that new species records are likely to be discovered. Vulnerable marine ecosystem (VME) indicator species and other key taxa provide seafloor structure for mobile species and important ecosystem functions, such as energy cycling, especially in the deeper areas of the fjord and fjard that are dominated by soft sediment. The sites with the highest benthic diversity, including the greatest densities of scallops and fish fauna, were in the archipelago and polynya, areas frequently used by Inuit for traditional harvesting. These findings were suggestive of a more direct linkage between these areas and trophic levels of greatest importance to Labrador Inuit. Understanding these patterns from the combined perspectives of Inuit and Western science in Nunatsiavut marine waters will guide resource management and protected area decisions, including those in the Nunatsiavut Government’s Imappivut Marine Planning Initiative.

Influence of different Eucalyptus hybrids on soil macrofauna.

The present work aimed to evaluate the influence of different eucalyptus hybrids on the edaphic macrofauna community. It is hypothesized that the density and diversity of edaphic fauna are influenced by the quantity and quality of the litter deposited by the different hybrids on the soil surface. The study area is in the city of Vitória da Conquista (BA) and consists of seven eucalyptus hybrids, one from sexual reproduction (seminal) and six from asexual (clonal) reproduction. Sampling of the soil macrofauna was performed by the Tropical Soil Biology and Fertility method. All visible invertebrates were collected and identified at the level of large taxonomic groups. The relative density, group richness, and diversity index were calculated. Hybrids did not influence the total density and richness of the soil macrofauna. However, it was possible to observe changes in litter accumulation and composition, and as a result in the diversity indexes and in the presence or absence of macrofauna groups. Among the studied hybrids, those from Eucalyptus urophylla (seminal, 1335 and 1249) promote greater macrofauna diversity and favor the occurrence of detritivores organisms, suggesting the occurrence of better quality and more palatable litter for the edaphic fauna.

ECOSYSTEM FUNCTION OF SOIL INVERTEBRATES AND RELATIONSHIPS OF SOIL PROPERTIES FROM DIFFERENT AGRICULTURE FIELD IN UNIVERSITY CAMPUS AND PRIVATE FARM IN PENINSULAR MALAYSIA

The invertebrate species play different roles above and below ground in a soil ecosystem. They are also responsible for a complex interaction, which is manifested in soils as self-organized systems of different sizes and functions. These invertebrates are sensitive to any changes in land management activities and soil physio-chemical properties. Therefore, the current study aims to examine the ecosystem functions of soil invertebrates from different agriculture fields and establish the relationships of soil physio-chemical properties. Soil samples were collected from four different fields: three are from the main campus, namely Universiti Putra Malaysia (Center of Environmental and Forensic Studies (CEFS), papaya and organic farm), and one is from Nilai, Negeri Sembilan. The soil physical properties, such as moisture, temperature, particle size, bulk density, and soil porosity, were recorded. Soil chemical properties (EC, pH, total C&amp;N, C/N ratio, organic matter, extractable P, Ca, Mg, K, and Na, CEC) were also determined. Pitfall traps and Berlese funnel were used as sampling methods. The invertebrates were stored in 70% ethanol and identified using soil invertebrate morphological classification, which was classified based on body size and biological functional groups. Macrofauna composition in the papaya farm was abundant from other sites at 80.44%, and ecosystem engineers comprised 39.56%. By contrast, mesofauna was abundant with 43.22% in organic farms, and litter transformers were abundant in CEFS at 54.05%. Meanwhile, microfauna was high in organic farms at 2.85%. Predatory populations were also high in Nilai farm at 49.29%. The CCA analysis showed that the physical and chemical properties of soil influence soil fauna density and diversity. The present finding concludes that the activities of ecosystem functions of soil invertebrates were considerably affected by agricultural and management activities

A comparison of sedimentological, environmental and fauna between two regions, NW of the Arabian Gulf

Marine environment is considered one of the richest environments in fauna of benthic marine micropaleontology because of the suitable conditions for living requirements like food, oxygen, sediment texture and salinity. In the current study, a fauna and their distribution were studied according to the depths of subsurface marine sediments from two regions at the NW Arabian Gulf, the first region at Khor Shytanah (Core 1) at the north of the study area representing a sever environment with high currents, and contain more than 95% sand grains, it is of light color, large size, rounded to sub-rounded grains and clean due to the continuous washing and water movement, whereas the second region was near the oil Basrah Port (Core 2) at the south of the study area, where the quite environment with weak currents and fine sand of dark color due to the activity of non-anaerobic bacteria , the region has angular to sub-angular grains. The type of sediment texture was determined at each depth and consisted of silt, sand silt, sand and silty sand. On the other hand, the percentage of calcium carbonate was determined in the sediments to correlates that with the size and density of fauna that live in this area.

Identifying Black Corals and Octocorals From Deep-Sea Imagery for Ecological Assessments: Trade-Offs Between Morphology and Taxonomy

An increased reliance on imagery as the source of biodiversity data from the deep sea has stimulated many recent advances in image annotation and data management. The form of image-derived data is determined by the way faunal units are classified and should align with the needs of the ecological study to which it is applied. Some applications may require only low-resolution biodiversity data, which is easier and cheaper to generate, whereas others will require well-resolved biodiversity measures, which require a larger investment in annotation methods. We assessed these trade-offs using a dataset of 5 939 images and physical collections of black and octocorals taken during surveys from a seamount area in the southwest Pacific Ocean. Coral diversity was greatly underestimated in images: only 55 black and octocoral ‘phototaxa’ (best-possible identifications) were consistently distinguishable out of a known 210 species in the region (26%). Patterns of assemblage composition were compared between the phototaxa and a standardized Australian classification scheme (“CATAMI”) that uses morphotypes to classify taxa. Results were similar in many respects, but the identities of dominant, and detection of rare but locally abundant, coral entities were achieved only when annotation was at phototaxon resolution, and when faunal densities were recorded. A case study of data from 4 seamounts compared three additional classification schemes. Only the two with highest resolution – phototaxon and a combined phototaxon-morphological scheme – were able to distinguish black and octocoral communities on unimpacted vs. impacted seamounts. We conclude that image annotation schemes need to be fit-for-purpose. Morphological schemes such as CATAMI may perform well and are most easily standardized for cross-study data sharing, but high resolution (and more costly) annotation schemes are likely necessary for some ecological and management-based applications including biodiversity inventory, change detection (monitoring) – and to develop automated annotation using machine learning.

A comparative study on the density and seasonal variations of rotifer and copepod fauna in a pond of Tripura, India with a note on water quality parameters

A Comparative study was carried out in a pond of Tripura to observe the density and seasonal succession of rotifer and copepod fauna and the observation recorded 26 species of rotifer and 6 species of copepod fauna. Percentage composition of different families as well as percentage composition of each species in the recorded total rotifer and copepod fauna was also noted. Rotifer fauna showed maximum density in the winter and minimum density during summer. On the contrary, copepod fauna showed maximum density in the summer and minimum density in monsoon season. Rotifer fauna showed significant positive correlation with water temperature, free carbon dioxide, total alkalinity, nitrate-nitrogen, phosphate phosphorus and negative correlation with transparency. On the contrary, copepod fauna showed positive correlation with water temperature and pH and negative correlation with dissolved oxygen, total alkalinity and nitrate nitrogen. The observation infers that the densities of rotifer and copepod fauna varies with seasons which might be the dynamic nature of the aquatic ecosystem and might also be due to optimal condition in the water quality parameters of the studied pond ecosystem.

Biodiversity of Associated Megabenthic Invertebrate of Corall Reef Ecosystem of Petong Island Batam Indonesia

sGlobal warming and climate changes were of the main environmental concern of marine scientist in the last three decade. As a biodiversity hotspot, marine coastal ecosystem faced an environmental threat because of increasing sea surface temperature (SST) and land base effluent, which in turn had an impact on the biodiversity of megabenthic faunal on coral reef community. The present paper studied the current condition of reef ecosystem as well as biodiversity of megabenthic community in Petong Island, a core zone of Batam Marine Management Area (BMMA), Riau Archipelago Province. Gradual changes of physical and chemical properties of seawater originated from coastal activities presumably has caused an effect on benthic faunal community structure. It revealed that benthic lifeform coral cover account for 30,53%, categorized into fairly good, whereas abiotic sand cover of 16,53%. The lifeform consists of Acropora (AC)1.73% and non-Acropora 28,80%. Death coral with algae (DCA) account for 40,40% and death corall (DC) 2,80%, Soft Corall (SC) 1,20%, fleshy seaweed (FS) 0,07%, other fauna (OT) 1,47%, and rubble (R) 7,00%. Apparently, only 4 of target species megabenthic fauna from eight, were eccounterred including; seaurchin (Diadema sp.), topshell (Drupella sp.), giant clam (Tridacna sp.), trochus (Trochus sp.), with density of each megabenthic fauna calculated 5929, 1857, 71 and 71 ind/ha, respectively. It appeared that sea urchin were the highest density and followed by topshell (Drupella sp). Sea urchin were noted as a bioindicator of reef ecosystem health. High density of sea urchin may indicate that reef in unhealthy state. The presence of Diadema Sitosum indicate that dead coral were present and it feed on algae growing in dead coral. High density of sea urchin may indicate that reef in unhealthy state

Salinity as a Key Factor on the Benthic Fauna Diversity in the Coastal Lakes.

Simple SummarySalinity is a stress factor for benthic invertebrates. Based on a 2-year study of 9 coastal lakes along the southern Baltic Sea, representing freshwater, transitional, and brackish ecosystems, we have shown that benthic fauna was structured by sea water intrusion (=fluctuation of salinity). The increase in salinity gradient resulted in a decreasing trend in the richness and abundance of benthic species, while the diversity showed a slightly positive trend, but below statistical significance (p < 0.05). The abundance of benthic organisms was the highest in brackish costal lakes, where the marine component of fauna was identified. Due to the greatest instability of environmental conditions in lakes periodically linked with the sea (transitional), we found the lowest species number, α-diversity, and abundance, regardless of the season. Salinity appears as a key factor in controlling the functioning of the ecotone (coastal lakes, lagoons) between the marine and terrestrial environments. Salinity is a prerequisite for the proper assessment of the ecological status of coastal lakes and the development of effective methods of protecting coastal lakes.Benthic communities were studied in nine Polish coastal lakes of the Baltic Sea; representing three levels of hydrological connection with the sea (isolated, periodically connected, and permanently connected), with resultant differences in salinity (freshwater, transitional, and brackish). The lakes classified in this way allowed us to investigate biodiversity in relation to the degree of environmental pressure. Stress intensity in coastal water bodies, resulting from contrasting marine and terrestrial influences, varied from mild to severe. Spatial variation in environmental predictors affected species richness more strongly than seasonal fluctuations. The broader the spatial salinity gradient, the smaller the species number recorded. Differences in the intensity of natural instability only slightly affected species number and α-diversity. In Baltic coastal lakes, characterized by low salinity (max. 7.5 PSU), benthic faunal communities were dominated by large populations of opportunistic species. This applied primarily to closed systems and those periodically influenced by seawater intrusion. The marine component of fauna played a more important role in increasing the diversity of benthos in permanently open water bodies (brackish). The highest density of benthic fauna was recorded in them, whereas low values were associated with the strongest instability, observed in lakes periodically linked with the sea (transitional).

Environmental Drivers of Macroinvertebrate Assemblages within Peat Pool Habitat-Implication for Bioassessment

Macroinvertebrates are a crucial component of wetland trophic webs. Many taxa are used as bioindicators of ecosystem change. However, relationships between macroinvertebrates and the environmental factors in peat pool habitats are still not well recognized. The present study shows the results of long-term studies during the years 2010–2020, on the responses of macroinvertebrates to the changes of environmental variables in a peat pool habitat formed as a result of peat exploitation on continental raised bog. The RDA analysis significantly explained 87.3% of the variance in macroinvertebrates abundances. Assemblages of most taxa (Anisoptera, Chironomidae, Ceratopogonidae, Coleoptera, Hydrachnidia and Tabanidae) showed a strong relationship with N-NO3 and pH. Moreover, densities of Chaoboridae larvae were explained by chlorophyll-a concentrations. Dominant taxon, Chironomidae, constituted from 48% to 87% of total faunal density. The highest proportions showed larvae of Psectrocladius sp. (gr. sordidellus) and Chironomus sp. Changes in the composition of macroinvertebrate fauna over a period of 10 years reflect the eutrophication process of the peat pool and deterioration of habitat conditions.

Diversity of Deep-Sea Scale-Worms (Annelida, Polynoidae) in the Clarion-Clipperton Fracture Zone

The polymetallic nodules lying on the seafloor of the Clarion-Clipperton Fracture Zone (CCFZ) represent over 30 billion metric tons of manganese. A single mining operation has potential to directly impact approximately 200 km2 of the seabed per year. Yet, the biodiversity and functioning of the bentho-demersal ecosystem in the CCFZ remain poorly understood. Recent studies indicate a high species diversity in a food-poor environment, although the area remains poorly sampled. Undersampling is aggravated by a combination of low densities of fauna and high habitat heterogeneity at multiple spatial scales. This study examines the Polynoidae, a diverse family of mobile polychaetes. Sampling with an epibenthic sledge and a remotely operated vehicle was performed during the cruise SO239 within the eastern CCFZ. Five areas under the influence of a sea surface productivity gradient were visited. Specimens were identified using morphology and DNA: (i) to provide a more comprehensive account of polynoid diversity within the CCFZ, (ii) to infer factors potentially driving alpha and beta diversity, and (iii) to test the hypothesis that epibenthic polychaetes have low species turnover and large species range. Patterns of species turnover across the eastern CCFZ were correlated with organic carbon fluxes to the seafloor but there was also a differentiation in the composition of assemblages north and south of the Clarion fracture. In contrast to the previous studies, patterns of alpha taxonomic and phylogenetic diversity both suggest that polynoid assemblages are the most diverse at Area of Particular Environmental Interest no. 3, the most oligotrophic study site, located north of the Clarion fracture. Without ruling out the possibility of sampling bias, the main hypothesis explaining such high diversity is the diversification of polynoid subfamily Macellicephalinae, in response to oligotrophy. We propose that macellicephalins evolved under extremely low food supply conditions through adoption of a semi-pelagic mode of life, which enabled them to colonise new niches at the benthic boundary layer and foster their radiation at great depths.

Medium-term monitoring reveals effects of El Niño Southern Oscillation climate variability on local salinity and faunal dynamics on a restored oyster reef.

Human activities and regional-scale climate variability drive changes in the ecology of coastal and marine ecosystems. Ecological restoration has emerged as a best-management practice to combat habitat degradation and restore lost ecological functions. However, relatively short project monitoring timeframes have limited our understanding of the effects of interannual climate cycles on water quality and restoration dynamics. We collected measurements on a 23-ha oyster reef constructed in the Gulf of Mexico to determine the relationship between El Niño Southern Oscillation (ENSO)-driven climate variability and local salinity patterns, and to evaluate the effects of this climate variability and salinity on oyster population dynamics and faunal community composition over a medium-term (five-year) timeframe. The role of ENSO-driven climate variability on local salinity patterns (primarily from changes in precipitation and evaporation) and faunal dynamics was investigated using the Oceanic Niño Index (ONI). Salinity was negatively correlated with ONI with an approximately 4-month lag. Higher ONI values (El Niño periods) were followed by reductions in salinity, increases in oyster recruitment and density, and reductions in resident motile fauna density and species richness. Lower ONI values (La Niña periods) had higher and less variable salinities, and higher areal coverage of restoration substrates by large oysters. ENSO-driven salinity reductions in the second year after reef construction coincided with a shift in resident motile faunal community composition that was maintained despite a second strong salinity reduction in year 5. Our results indicate that it is important to expand the typical monitoring timeframes to at least five years so that resource managers and restoration practitioners can better understand how both short-term environmental variability and longer-term climate cycles can affect the outcomes of restoration actions.

Fauna associated with non-native Sargassum muticum (Fucales, Phaeophyceae) vary with thallus morphology and site type (sounds and bays)

ABSTRACT The invasive brown alga Sargassum muticum was first recorded in Norway in 1988 and is presently common in the sublittoral fringe on the sheltered coast in South Norway. Here, results from a study on mesofauna associated with S. muticum in an archipelago on the southwest coast of Norway are presented, with two stations placed in sounds exposed to tidal currents and two in sheltered bays. Sargassum muticum occurred with a patchy distribution and an estimated density of less than 7 individuals m−2 at three of the stations (two in sheltered bays and one in a sound) and 42 individuals m−2 at the fourth station (placed in a sound). A total of 102 distinct faunal taxa were identified, with an average of 31 taxa per sample. Crustacea and Gastropoda constituted around half of the identified taxa. Fauna richness showed no relation to site type but had a curvilinear correlation with habitat size (dry weight of thallus). Total and sessile fauna richness showed a significant negative correlation with branching density. Vagile faunal density showed a curvilinear correlation with weight of epiphytes and was significantly related to site type with higher densities in the bays. The community composition of vagile fauna reflected this and was significantly related to site type, but not to epiphyte weight or branching density. When including sessile taxa in a community analysis the stations became less separated, and the community was significantly influenced by branch density. Thus, both site characteristics and morphology of S. muticum influenced the associated fauna community.

Soil Fauna Community Diversity and Response to Wetland Degradation in Nanniwan Wetland

This study is to investigate the soil fauna community characteristics in the Nanniwan wetland, as well as their responses to changed environmental factors. Soil fauna from six representative habitats in the Nanniwan wetland were studied, in the spring, summer, autumn, and winter of 2016. Soil fauna community composition, density, and distribution were investigated. The relationships between soil fauna distribution and soil physicochemical properties were also analyzed. Overall, 3285 individuals were harvested, which belonged to 4 phyla, 10 classes, and 26 orders. The soil fauna density and group numbers differed among these habitats. The structure of the reclaimed wetland soil fauna community was the simplest among all these habitats. Wetland reclamation and degradation reduced the density and diversity of soil fauna, and changed the functional groups of soil fauna, resulting in decreased saprozoic soil fauna and increased predacity soil fauna. The total organic carbon content and the soil pH value represented the main influencing factors of soil fauna distribution. The soil fauna density was positively correlated with the soil total organic carbon and total nitrogen contents, while the soil fauna density was negatively correlated with the pH value. The soil fauna density is closely associated with the environmental factors in the Nanniwan wetland. These findings would help to quantitatively predict and evaluate the ecological function of soil fauna in the Nanniwan wetland.

Effects of Phyllostachys pubescens expansion on underground soil fauna community and soil food web in a Cryptomeria japonica plantation, Lushan Mountain, subtropical China

In order to determine the interactive effect of Phyllostachys pubescens (moso bamboo) expansion to adjacent coniferous forest (Cryptomeria japonica, Japanese cedar) on soil fauna communities and soil food web, we conducted a tangible investigation combined with natural abundance isotope analysis to examine how moso bamboo expansion process affects soil faunal composition and underground soil food web in Lushan mountain, southeast China. Exact treatments are as follows: (1) moso bamboo forest, (2) ecotone area and (3) Japanese cedar forest. We collected 74 arthropod groups from the field. The groups of Acari and Collembola were the two main soil fauna taxa with the highest abundance which accounted for 18.86–98.9% of the relative total abundance among various habitats. Peak of soil faunal density in moso bamboo and Japanese cedar forests appeared in May and November. Soil fauna community in ecotone was more similar to that in moso bamboo forest, indicating that the expansion process was still in infancy stage, and there was no significant difference in soil fauna community diversity index among the three forest types. Moso bamboo expansion did not affect the nutrient level of Collembola and Oribatida, but decreased that of Megsostigmata. The nutrient level of Hymenoptera and Coleoptera increased in ecotone, and Diptera kept in the third nutrient level in all three forest types, while the Hemiptera, Araneida and Pseudo-scorpionidea remained at a high level. The results demonstrated that in moso bamboo expansion process, soil fauna groups with low nutrient levels were more affected, while the soil faunas with high nutrient level were less affected.

Anthropogenic-induced environmental changes in the Nile-delta and their consequences on molluscan biodiversity and community structure

Global climate changes and anthropogenic pressures have altered many coastal ecosystems worldwide. To understand the consequences of these perturbations on the community structure of the benthic communities, the fauna and the sediments retrieved from a short core in the Manzala Lagoon, which is largest in the Nile Delta, were quantitatively analyzed. The 120 cm long-core represents 170 years. A significant ecosystem shift took place in the upper 41 cm of the lagoon sediments were attributed to hydrodynamic changes, associated with the construction of Aswan High-Dam, where heavy metals concentrations, Pollution Load Index (PLI), and fine-grain sediments were increased. Consequently, the community structure of the benthic fauna was dramatically changed. Currently, the benthic community is dominated by brackish and opportunistic taxa (e.g., Fulvia fragilis, Pirenella conica, Corbicula fluminalis, and Melanoidestuberculata). In contrast, the pre-impact community contains equilibrium freshwater species. These salinity-controlled communities were better characterized on both Bray-Curtis -based Constrained Clustering (CC) and non-Metric Multidimensional Scaling (nMDS). The faunal density and Dominance Index are higher in the top samples, which point either to anthropogenic disturbance or taphonomic (mechanical or chemical) distortion with depths. However, higher species richness in lower samples suggested that the mechanical distortion has not altered the original communities and point to anthropogenic drivers of the diversity loss. Further declining or even extinction of the equilibrium species in the future is expected if no restoration programs implemented soon. Furthermore, nMDS and RMA regression models showed that the distribution of benthic fauna is governed by abiotic factors (e.g., water salinity, metal concentrations, and sediment grain-size). The latter indicates that biotic traits of benthic fauna such as feeding-mode and life-habit are highly sensitive to minor environmental changes and thus can be used as a robust indicator in paleoenvironmental reconstructions.

Regionalization of benthic hard-bottom communities across the Pourtalès Terrace, Florida

The Pourtalès Terrace is an exposed hard-bottom platform located south of the Florida Keys in 200–450 m depth with a diverse deep-sea coral ecosystem dominated by stylasterid hydrocorals, octocorals, and sponges that supports recreational and commercial fisheries. Portions of the Terrace have been designated as managed areas in the absence of detailed habitat maps, which hampers identifying ecological benefits derived from such management actions. Here we report analyses of historic Terrace physiographic and geologic data with more recent high-resolution bathymetric and benthic data to statistically derive a benthic community characterization across the Terrace. Multivariate analyses of faunal density from 42 standardized sites showed spatially distinct communities: East Terrace, West Terrace, Upper Terrace Edge, Sinkholes and Lophelia Coral Mound (the southernmost record of this habitat in the continental U.S.). These corresponded to physiographic divisions into an Upper Terrace comprised of Central and Karst-like regions, and Lower Terrace. A detailed description of these communities is provided. This study presents new insights into the Terrace benthic community spatial arrangement and is a necessary step towards facilitating benthic mapping. Our recommendations highlight the information needed for benthic habitat map creation and collecting data to determine if current conservation boundaries match management goals.

Recovery of hydrothermal vent communities in response to an induced disturbance at the Lucky Strike vent field (Mid-Atlantic Ridge)

So far, the natural recovery of vent communities at large scales has only been evaluated at fast spreading centers, by monitoring faunal recolonisation after volcanic eruptions. However, at slow spreading ridges, opportunities to observe natural disturbances are rare, the overall hydrothermal system being more stable. In this study, we implemented a novel experimental approach by inducing a small-scale disturbance to assess the recovery potential of vent communities along the slow-spreading northern Mid-Atlantic Ridge (nMAR). We followed the recovery patterns of thirteen Bathymodiolus azoricus mussel assemblages colonising an active vent edifice at the Lucky Strike vent field, in relation to environmental conditions and assessed the role of biotic interactions in recolonisation dynamics. Within 2 years after the disturbance, almost all taxonomic richness had recovered, with the exception of a few low occurrence species. However, we observed only a partial recovery of faunal densities and a major change in faunal composition characterised by an increase in abundance of gastropod species, which are hypothesised to be the pioneer colonists of these habitats. Although not significant, our results suggest a potential role of mobile predators in early-colonisation stages. A model of post-disturbance succession for nMAR vent communities from habitat opening to climax assemblages is proposed, also highlighting numerous knowledge gaps. This type of experimental approach, combined with dispersal and connectivity analyses, will contribute to fully assess the resilience of active vent communities after a major disturbance, especially along slow spreading centers targeted for seafloor massive sulphide extraction.

A chemosynthetic ecotone—“chemotone”—in the sediments surrounding deep‐sea methane seeps

AbstractEcotones have been described as “biodiversity hotspots” from myriad environments, yet have not been studied extensively in the deep ocean. While physiologically challenging, deep‐water methane seeps host highly productive communities fueled predominantly by chemosynthetic pathways. We hypothesized that the biological and geochemical influence of methane seeps extends into background habitats, resulting in the formation of a “chemotone” where chemosynthesis‐based and photosynthesis‐based communities overlap. To investigate this, we analyzed the macrofaunal assemblages and geochemical properties of sediments collected from “active,” “transition” (potential chemotone), and “background” habitats surrounding five Costa Rican methane seeps (depth range 377–1908 m). Sediment geochemistry demonstrated a clear distinction between active and transition habitats, but not between transition and background habitats. In contrast, biological variables confirmed the presence of a chemotone, characterized by intermediate biomass, a distinct species composition (including habitat endemics and species from both active and background habitats), and enhanced variability in species composition among samples. However, chemotone assemblages were not distinct from active and/or background assemblages in terms of faunal density, biological trait composition, or diversity. Biomass and faunal stable isotope data suggest that chemotones are driven by a gradient in food delivery, receiving supplements from chemosynthetic production in addition to available photosynthetic‐based resources. Sediment geochemistry suggests that chemosynthetic food supplements are delivered across the chemotone at least in part through the water column, as opposed to reflecting exclusively in situ chemosynthetic production in sediments. Management efforts should be cognisant of the ecological attributes and spatial extent of the chemotone that surrounds deep‐sea chemosynthetic environments.

Stable isotopic signatures of sediment carbon and nitrogen sources and its relation to benthic meiofaunal distribution in the Arctic Kongsfjord

AbstractThe present study investigated the relationship of sediment attributes to meiofaunal composition pattern and its food source in the Kongsfjord. Sediment in the fjord is dominated with silty clay fractions. Ten meiofaunal groups contributed to the meiofaunal composition in the fjord with the dominance of foraminiferans, nematodes and tintinnids. The total density of fauna ranged from 1 ind./10 cm2 to 1,560 ind./10 cm2 whereas the biomass ranged from 0.06 ± 0.002 μg/10 cm2 to 605.1 ± 7.19 μg/10 cm2. On comparing with previous studies, our data exhibited a significant decrease in the overall density and biomass of the meiofauna. Sediment δ13C values were relatively low in the fjord that varied from −21.6‰ to −22.9‰, and this could be due to low CO2 concentrations in the ambient environment. The isotopic value proves that the carbon supply in the fjord sediment is linked to the marine source largely from single‐celled phytoplankton in the photic zones. Isotope value of δ15N increases in the fjord system when marine productivity is relatively high; that also varies from 4.6‰ to 6.8‰, further suggesting that the origin of fjord sediment nitrogen is supplied from the nutrient‐rich warm Atlantic water masses contributing to high marine production in the fjord. TOC/TN values in the fjord were lower than 10%, which also supports our hypothesis that Kongsfjord sediment organic matter was received mainly from marine source.