Macrofaunal Biodiversity Research Articles

Succession of soil macro-faunal biodiversity in forests converted from croplands after long-term coastal reclamation

The long-term succession of the soil macro-faunal community after reclamation at coastal areas is not well understood, especially at the time scale of centuries. The objective of this work was to analyze soil development by measuring its principal physico-chemical properties and study the macro-faunal biodiversity succession along the successional trajectory created by intermittent reclamation. We hypothesized that soil macro-faunal taxonomic and functional diversity, richness, and density would increase after long-term reclamation, and that macro-faunal succession was related to dike age. In July 2014, sites of varying dike age (30, 50, 100, and 200 years) were used to represent a successional trajectory of Fluvisol soils at a reclaimed coast at Yancheng, China. The selected habitats were planted with 14–17 years old poplar (Populus euramericana) or dawn redwood (Metasequoia glyptostroboides) trees. With increasing dike age, soil nutrient status improved over the successional trajectory, as indicated by the increased soil organic carbon (SOC) concentration, total nitrogen (TN), and total phosphorous (TP). Soil salt concentration (SSC), pH, and carbon-nitrogen (C/N) ratio continuously decreased, as did soil bulk density (BD), the latter of which had a smaller coefficient of variation than the other properties did. Over the first 100 years of macro-faunal succession, taxonomic richness, abundance, Margalef’s richness index, and the Shannon-Weaver diversity index increased significantly, but did not differ significantly between the habitats with dike ages of 100 and 200 years. Significant differences in the measured communities’ characters were detected between forests planted with different trees when the dike age was 50 years but not when it was 30 years. Differences in macro-faunal community structure were primarily related to SOC and SSC, which were considerably related to dike age. The taxonomic richness and abundance of functional groups varied significantly among habitats and was related to changes in food resources in the soil environment. The abundance and taxonomic richness of phytophagous and saprophagous species increased with increasing dike age; no significant differences were noted in taxonomic richness of omnivorous species and predator abundance. The results thus supported our hypotheses. In conclusion, long-term macro-faunal community succession was affected by dike age, land use, and soil development after reclamation, and the soil macro-faunal biodiversity tended to increase with increasing dike age.

Temperature Driven Changes in Benthic Bacterial Diversity Influences Biogeochemical Cycling in Coastal Sediments.

Marine sediments are important sites for global biogeochemical cycling, mediated by macrofauna and microalgae. However, it is the microorganisms that drive these key processes. There is strong evidence that coastal benthic habitats will be affected by changing environmental variables (rising temperature, elevated CO2), and research has generally focused on the impact on macrofaunal biodiversity and ecosystem services. Despite their importance, there is less understanding of how microbial community assemblages will respond to environmental changes. In this study, a manipulative mesocosm experiment was employed, using next-generation sequencing to assess changes in microbial communities under future environmental change scenarios. Illumina sequencing generated over 11 million 16S rRNA gene sequences (using a primer set biased toward bacteria) and revealed Bacteroidetes and Proteobacteria dominated the total bacterial community of sediment samples. In this study, the sequencing coverage and depth revealed clear changes in species abundance within some phyla. Bacterial community composition was correlated with simulated environmental conditions, and species level community composition was significantly influenced by the mean temperature of the environmental regime (p = 0.002), but not by variation in CO2 or diurnal temperature variation. Species level changes with increasing mean temperature corresponded with changes in NH4 concentration, suggesting there is no functional redundancy in microbial communities for nitrogen cycling. Marine coastal biogeochemical cycling under future environmental conditions is likely to be driven by changes in nutrient availability as a direct result of microbial activity.

Functional trait responses to sediment deposition reduce macrofauna-mediated ecosystem functioning in an estuarine mudflat

Abstract. Human activities, among which dredging and land use change in river basins, are altering estuarine ecosystems. These activities may result in changes in sedimentary processes, affecting biodiversity of sediment macrofauna. As macrofauna controls sediment chemistry and fluxes of energy and matter between water column and sediment, changes in the structure of macrobenthic communities could affect the functioning of an entire ecosystem. We assessed the impact of sediment deposition on intertidal macrobenthic communities and on rates of an important ecosystem function, i.e. sediment community oxygen consumption (SCOC). An experiment was performed with undisturbed sediment samples from the Scheldt river estuary (SW Netherlands). The samples were subjected to four sedimentation regimes: one control and three with a deposited sediment layer of 1, 2 or 5 cm. Oxygen consumption was measured during incubation at ambient temperature. Luminophores applied at the surface, and a seawater–bromide mixture, served as tracers for bioturbation and bio-irrigation, respectively. After incubation, the macrofauna was extracted, identified, and counted and then classified into functional groups based on motility and sediment reworking capacity. Total macrofaunal densities dropped already under the thinnest deposits. The most affected fauna were surficial and low-motility animals, occurring at high densities in the control. Their mortality resulted in a drop in SCOC, which decreased steadily with increasing deposit thickness, while bio-irrigation and bioturbation activity showed increases in the lower sediment deposition regimes but decreases in the more extreme treatments. The initial increased activity likely counteracted the effects of the drop in low-motility, surficial fauna densities, resulting in a steady rather than sudden fall in oxygen consumption. We conclude that the functional identity in terms of motility and sediment reworking can be crucial in our understanding of the regulation of ecosystem functioning and the impact of habitat alterations such as sediment deposition.

Single-tree selection system effects on forest soil macrofauna biodiversity in mixed oriental beech stands

Hyrcanian temperate forests are of importance due to their genetic variation, biodiversity, commercial productions and many other ecosystem services. Over the past decades the selection silvicultural system (mostly single-tree selection) has been the dominant method to manage and utilize these forest ecosystems. This study aimed to assess the effect of single-tree selection silvicultural system on mixed beech stands of eastern Hyrcanian temperate forests using soil macrofauna as bioindicator. Therefore 91 forest treefall gaps have been selected of which 36 gaps were natural gaps in managed stands, 41 gaps were human created gaps and 14 gaps were natural gaps in virgin stands. In each gap 3 soil profiles and in each profile 3 soil samples were taken at 3 depths, including litter layer, shallow (0–10cm) and deep (10–20cm) soil. Macrofauna of all soil samples were extracted and identified to class level and weighed. Diversity (Shannon and Simpson) and evenness indices were calculated for all soil samples. Results showed that most important macrofauna based on biomass were Clitellata, Gastropoda, Chilopoda and Diplopoda in the study area. In the litter layer of all gaps Gastropoda (snails) have the most amount of biomass followed by Chilopoda (millipedes), while in shallow and deep soil Clitellata (earthworms) and Chilopoda were the main classes based on biomass. There was no significant difference in diversity and evenness indices among the three gap groups (virgin, natural and artificial) which indicates that the single-tree selection system has not intensive and irrecoverable effects on the soil macrofauna of the studied forest stands after about 10 years.

Spatial relationship between soil macrofauna biodiversity and trees in Zagros forests, Iran

One major factor in determining the spatial distribution pattern of soil macrofauna diversity in forest ecosystems is the close relationship with tree species. Information about the spatial relationship between soil macrofauna and tree diversity is scarce, especially at regional scales. To assess soil macrofauna distribution and evaluate the spatial relationships between macrofauna diversity and tree cover properties at the regional scale, a study was conducted in the Zagros forests of Iran. To investigate properties of tree cover, 83 plots (100m2) in a 100m×100m sampling grid were established. In each plot, soil macrofauna were extracted from 50cm×50cm×10cm soil monoliths located in the center of the plots. We classified soil macrofauna into two categories as total macrofauna (earthworm plus other taxa) and only earthworms. Data were analyzed using geostatistics (variograms and cross-variograms) in order to describe the spatial dependence of macrofauna and their relation to tree cover properties. Macrofauna abundance and diversity were distributed at geostatistical large range (3110 and 2110m), whereas, earthworm abundance had spatial autocorrelation at small range (691m). Macrofauna abundance and diversity were spatially related to tree cover density, diversity and evenness of tree species in addition to the density of Pyrus syriaca and Crataegus pontica at small ranges. Our results showed that tree density and diversity could be the key drivers of the spatial patterning of soil macrofauna diversity in this area. These results might be related to the conditions provided by the tree species in the surrounding environment. According to our results tree species diversity changed within a small distance (149m) creating patches that could lead to the heterogeneity of resources and microhabitats, promoting beneficial habitats for soil macrofauna. These microhabitats can provide the suitable conditions (light, moisture and litter quality) for determining the macrofauna distribution.

Biodiversity, feeding habits and reproductive strategies of benthic macrofauna in a protected area of the northern Adriatic Sea: a three-year study

The macrozoobenthic community at a sublittoral station located in the Marine Protected Area of Miramare, Gulf of Trieste (Italy) was investigated monthly from June 2002 to July 2005. Community variables were studied and related to food sources (particulate, total and biopolymeric carbon contents, benthic microalgae and meiofauna). In addition, the macrofaunal response to a heatwave that occurred in summer 2003 in the area was also explored. Univariate and multivariate analyses highlighted that the macrozoobenthic community structure shifted towards the end of the study. Diversity remained fairly stable throughout the study, despite the high turnover values. From a dominance of short-lived invertebrates related to irregular fresh organic matter inputs, the community shifted toward long-lived taxa, principally related to an increase of biopolymeric C and microalgal biomass. Semelparous invertebrates seem to be less resistant to high temperatures compared to iteroparous ones. The latter proved to be capable competitors since they prevailed over the semelparous species towards the end of the study.The community exhibited a certain degree of resistance to high temperature, due to the adaptation of the macrofaunal invertebrates to this particular stress, induced by the wide natural fluctuations in temperature that occur on a seasonal basis in the Gulf of Trieste. This study highlights the importance of long datasets to assess the state and ecological processes of the macrofaunal communities.

Exploring the Relationship between Macrofaunal Biodiversity and Ecosystem Functioning in the Deep Sea

The global scale of the biodiversity crisis has stimulated research into the relationship between biodiversity and ecosystem functioning (BEF). Even though the deep sea is the largest biome on Earth, BEF studies in deep-sea benthic ecosystems are scant. Moreover, the small number of recent studies, which mostly focus on meiobenthic nematodes, report conflicting results that range from a very clear positive relationship to none at all. In this BEF study, the deep-sea macrofauna were used as a model to investigate the structural and functional diversity of macrofauna assemblages at three depths (1200, 1900, and 3000 m) in seven open-slope systems from the North-Eastern Atlantic Ocean to the Central-Eastern Mediterranean Sea. The presence and nature of BEF relationships were studied considering two spatial scales, the large and the basin scale, in different environmental settings. Total benthic biomass and macrofaunal predator biomass were used as proxies to assess ecosystem functioning. Ecosystem efficiency was expressed as macrofaunal biomass to biopolymeric carbon content ratio, macrofaunal biomass to prokaryotic biomass ratio, macrofaunal biomass to meiofaunal biomass ratio, and meiofaunal biomass to prokaryotic biomass ratio. On both large and basin spatial scales, some significant relationships between macrofaunal diversity and ecosystem functioning and efficiency were reported. When significant, the nature of BEF relations was positive and exponential or linear supporting the general idea that a higher diversity can enhance ecosystem functioning. Other BEF relationships were explained by the effect of environmental variables. More data from different deep-sea systems are needed, to better elucidate the consequences of biodiversity loss on the ocean floor.

The Community Structure of Deep-Sea Macrofauna Associated with Polymetallic Nodules in the Eastern Part of the Clarion-Clipperton Fracture Zone

Deep-sea areas characterized by the presence of polymetallic nodules are getting increased attention due to their potential commercial and strategic interest for metals such as nickel, copper and cobalt. The polymetallic nodules occur in areas beyond national jurisdiction, regulated by the International Seabed Authority (ISA). Under exploration contracts, contractors have the obligation to determine the environmental baseline in the exploration areas. Despite a large number of scientific cruises to the central east Pacific Ocean, few published data on the macrofaunal biodiversity and community structure are available for the abyssal fields of the Clarion-Clipperton Fracture Zone (CCFZ). This study focused on the macrofaunal abundance, diversity and community structure in three physically comparable, mineable sites located in the license area of Global Sea Mineral Resources N.V., at ~ 4500 m depth. A homogeneous but diverse macrofaunal community associated with the sediment from polymetallic nodule areas was observed at a scale of 10s to 100s of km. However, slight differences in the abundance and diversity of Polychaeta between sites can be explained by a decline in the estimated flux of particulate organic carbon (POC) along a southeast-northwest gradient, as well as by small differences in sediment characteristics and nodule abundance. The observed homogeneity in the macrofaunal community is an important prerequisite for assigning areas for impact and preservation reference zones. However, a precautionary approach regarding mining activities is recommended, awaiting further research during the exploration phase on environmental factors structuring macrofaunal communities in the CCFZ. For instance, future studies should consider habitat heterogeneity, which was previously shown to structure macrofauna communities at larger spatial scales. Acknowledging the limited sampling in the current study, a large fraction (59-85%; depending on the richness estimator used and the macrofaunal taxon of interest) of the macrofaunal genus/species diversity from the habitat under study was characterized.

Digging for historical data on the occurrence of benthic macrofaunal species in the southeastern Mediterranean

BackgroundThe benthic macrofaunal biodiversity of the southeastern Mediterranean is considerably understudied compared to other Mediterranean regions. Monitoring biodiversity in this area is crucial as this region is particularly susceptible to biological invasions and temperature alteration. Historical biodiversity data could provide a useful baseline for monitoring potential changes and provide informarion to support a better understanding of the possible effects of anthropogenic activities on marine benthic communities.New informationIn this study, performed under the LifeWatchGreece Research Infrastructure, we present historical benthic occurrence data obtained from the sampling expedition carried out in 1933 by Adolf Steuer in the coastal area around Alexandria, Egypt, eastern Mediterranean. The occurrences were geo-referenced to more than 170 stations, mostly located in the area of Alexandria, and the nearby coasts and lakes. All records were digitized and species names were cross-checked and taxonomically updated using the World Register of Marine Species. The outcome clearly shows that such initiatives can reveal an unexpected amount of highly valuable biodiversity information for “data-poor” regions.

Caracterização da macrofauna edáfica em sistemas de produção de grãos no Sudoeste do Piauí

Resumo O objetivo deste trabalho foi caracterizar a macrofauna edáfica em sistemas de produção de grãos sob plantio direto e convencional no Sudoeste do Piauí, na região de Matopiba. Amostras de solo foram coletadas nas camadas de 0,0-0,1, 0,1-0,2 e 0,2-0,3 m, com serrapilheira, em áreas cultivadas predominantemente com milho e soja, sob preparo convencional e plantio direto, em solos com diferentes texturas. Remanescentes de vegetação nativa adjacentes foram amostrados como referência. A macrofauna edáfica nos diferentes sistemas de uso do solo foi identificada até o nível de famílias, as quais foram agrupadas de acordo com suas funções ecológicas. Os grupos mais abundantes nas áreas amostradas foram Isoptera, Hymenoptera e Coleoptera, este com o maior número de famílias. A análise de componentes principais revelou que os grupos funcionais geófago/bioturbador, fitófago/praga e predador/parasita estão associados a solos de textura argilo-siltosa; enquanto o grupo detritívoro/decompositor, a solos mais arenosos. Os sistemas de manejo do solo alteram a estrutura da comunidade de macroinvertebrados edáficos em relação à condição natural de Cerrado. O plantio direto proporciona maior abundância e riqueza de espécies que o preparo convencional, e minimiza o impacto de sistemas agrícolas sobre a biodiversidade da macrofauna edáfica.

English

Soil macrofauna organisms are recognized as ecological indicators of soil management practices. Sugarcane monoculture can have negative impacts on soil, including biodiversity loss, which should be evaluated. In that sense, the aim of this was to determine the diversity macrofauna under sugarcane (Saccharum spp.) annual growth cycle (2012-2013) comparing two different natural vegetation areas (Sandbank and Atlantic forest). The study areas are located at Usina Santa Teresa in Goiana municipality, in Zona Mata Norte of the Pernambuco State (Brazil). Soil macrofauna samples were collected in January, April and August 2013. In order to collect soil macrofauna samples, 5 pitfall traps were placed in the field for 7 days. Descriptive statistics and biodiversity indices were used to carry out data analysis. The presence and biodiversity indices were affected by the hydrological regime. Sugarcane harvest with straw burning initially promoted soil macrofauna taxa better adapted to system drastic changes. Moreover, as sugarcane growth year went by, soil macrofauna biodiversity indices similar to those reported at natural vegetation areas (Sandbank and Atlantic Forest) were observed.   Key words: Bioindicator, burnt sugarcane, functional groups, soil macrofauna.

Methane seepage effects on biodiversity and biological traits of macrofauna inhabiting authigenic carbonates

Authigenic carbonate rocks at methane seeps are recognized as hosting diverse and abundant invertebrate assemblages, with potential forcing from fluid seepage and hydrography. Mensurative studies of carbonate macrofauna (>0.3mm) at Hydrate Ridge, OR revealed little effect of water depth and overlying oxygenation (at 600m and 800m) but a large influence of seepage activity on density, taxonomic composition, diversity, and biological traits (feeding, lifestyle, motility, size and calcification). Rocks exposed to active seepage had 3–4× higher total macrofaunal densities than under inactive conditions. Assemblages exhibited higher species richness and reduced evenness (greater dominance) under active seepage than inactive conditions, but no difference in H′ or rarefaction diversity. Actively seeping sites were characterized by errant (motile), bacterial grazing, small- and medium-sized, heavily calcified species, whereas inactive sites exhibited a greater diversity of feeding modes and more burrowers, sessile, large and lightly calcified species. Active rocks supported more exogonid (Syllidae), ampharetid, and cirratulid polychaetes, provannid snails, pyropeltid limpets, nemerteans, and sponges; whereas inactive rocks supported higher densities of ophiuroids, isopods, gammarid amphipods, hydroids, Typosyllis (Syllidae) and tanaids. Transplant experiments, in which rocks were transferred between active and inactive sites at Hydrate Ridge North (600m), revealed that assemblages respond within 13months to increase or cessation of seepage, taking on the feeding, size and calcification characteristics of the background fauna at the new site. Lifestyles and motility patterns shifted more slowly as the sessile, attached species did not track seepage as quickly. Provannid snails and pyropeltid limpets rapidly colonized rocks transplanted to active sites and disappeared when transplanted to inactive sites. Given the known variability of fluid fluxes and rapid community response, a mosaic of communities changing in space and time is hypothesized to generate the relatively high species diversity at methane seeps.

Microhabitat heterogeneity enhances soil macrofauna and plant species diversity in an Ash – Field Maple woodland

The high biodiversity of soil ecosystems is often attributed to their spatial heterogeneity at multiple scales, but studies on the small-scale spatial distribution of soil macrofauna are rare. This case study of an Ash – Field Maple woodland partially converted to conifer plantation investigates differences between species assemblages of soil and litter invertebrates, and plants, using multivariate ordination and indicator species analysis for eleven microhabitats.Microhabitats representing the main body of uniform litter were compared with more localised microhabitats including dead wood and areas of wet soil. Species accumulation curves suggest that for this site it is more efficient to sample from varied microhabitats of limited spatial scale rather than the broad habitat areas when generating a species inventory. For comparative work sampling the main body of uniform litter is more appropriate, given that microhabitats vary from woodland to woodland and would make standardisation problematic.Vegetation showed more distinctive microhabitat-specific species assemblages than soil and leaf litter invertebrates and was strongly associated with environmental variables. Microhabitats with distinct assemblages included dead wood habitats, which had a high proportion of saproxylic species; a highly disturbed microhabitat with distinct plant and soil species characteristic of ruderal habitats and seeps with earthworm species rarely sampled in standard soil biodiversity surveys.The leaf litter in the conifer plantation area was species poor and the biodiversity quantified was considerably enhanced by the sampling from the additional microhabitats - illustrating the importance of small-scale heterogeneity for increasing plant and soil macrofauna biodiversity at this site.

Abundance and Diversity of Soil Macrofauna in Native Forest, Eucalyptus Plantations, Perennial Pasture, Integrated Crop-Livestock, and No-Tillage Cropping

Intensive land use can affect macrofaunal biodiversity, which is a property that can be used as a soil quality indicator. This study evaluated the abundance and diversity of soil macrofauna and its relation to soil chemical and physical properties in five land use systems (LUS) in the eastern region of Santa Catarina. The following LUS were studied: native forest (NF), eucalyptus plantations (EP), perennial pasture (PP), integrated crop-livestock (ICL), and no-tillage cropping (NT). The macrofauna was quantified in 0.25 × 0.25 m monoliths and sampled in the 0.00-0.20 m layer in the summer (Jan/2012) and winter (Jul/2012). For each LUS, nine points were sampled, distributed in a 30 × 30 m sampling grid. After screening the edaphic macrofauna organisms, the individuals were counted and identified at the species level when possible, or in major taxonomic groups. The Shannon diversity indices were calculated and the macrofaunal groups together with the physical and chemical properties were subjected to principal component (PCA) and redundancy analysis (RDA). The abundance and diversity of macrofaunal groups are affected by the LUS. The properties of organic matter, macroporosity, bulk density, cation exchange capacity at pH 7.0, base saturation, potential acidity, and exchangeable Al were related to the abundance of soil macrofaunal groups. The stability and biodiversity of soil macrofauna were highest in the LUS of NF, PP, and EP.

Ecotoxicological evaluation of sediments applied to environmental forensic investigation.

The present study aimed to evaluate the potential for using toxicity assays with sediment samples for the detection of water pollution caused by the discharge of tannery effluents into water bodies and its application to environmental forensic investigation. The study included ecotoxicological evaluation of sediments, survey of benthic organisms in the field, as well as chromium, cadmium and lead dosage which provided data for a sediment quality triad evaluation. The sediment samples showed acute and chronic toxicity to the bioindicators, low biodiversity of benthic macrofauna and high chromium concentration, reaching up to 4365 mg.Kg-1. A close relationship was observed between the separate results of ecotoxicological sediment evaluation and the sediment quality triad. The sediment ecotoxicological assessment proved to be applicable to tracking sources of contamination related to tanneries and similar activities in environmental forensics.

Relationship between Soil Macro fauna Biodiversity and Trees and Shrubs in Riparian Forest of Maroon River in Khuzestan Province

Relationship between Soil Macro fauna Biodiversity and Trees and Shrubs in Riparian Forest of Maroon River in Khuzestan Province

Deep-sea meiofauna and macrofauna diversity and functional diversity: are they related?

Meiofauna and macrofauna are closely linked by numerous types of interactions, but comparative studies are rare. It has been postulated that meiofauna and macrofauna diversities are related, and that a higher functional diversity of meiobenthic and/or macrobenthic organisms can enhance a higher functional diversity. A simultaneous study of the deep Mediterranean sea meiobenthic and macrobenthic communities was conducted, from the west to central-eastern basin and from 1,200 to 2,700 m depth. We posed the following questions: 1) are meiofauna and macrofauna diversities related? 2) Does a higher diversity enhance a higher functional diversity? and 3) Does the relationship between diversity and functional diversity change considering different benthic size classes and taxa? In order to answer to our questions, the biodiversity and functional diversity of meiofauna and macrofauna were analysed, with a focus on three target groups: meiobenthic nematodes, macrobenthic nematodes and polychaetes. Meiobenthic nematodes and macrofaunal diversity appeared to be related only in terms of turnover diversity. A cross-taxon analysis on macrobenthic nematode and polychaete diversity and meiofauna diversity revealed a positive relationship in all cases that were studied. Considering functional diversity, many relationships emerged between the two benthic components. A higher meiobenthic nematode diversity did not enhance a higher functional diversity. A higher macrofauna diversity enhanced a higher functional diversity, but not for all macrobenthic taxa (i.e., nematodes). We can conclude that the diversity–functional diversity relationship changed across different size classes, even when the same taxon was considered. The diversity–functional diversity relationship changed across taxa even if they belonged to the same size class.

Biodiversity and seasonal variation of benthic macrofauna in Minicoy Island, Lakshadweep, India

From the Indian coast only limited data are available on the benthic fauna of the seagrass communities. In this study, seasonal variation in the distribution of macrobenthos and influence of environmental parameters was explored at four seagrass beds and two mangrove stations along the Minicoy Island, Lakshadweep, India, from September 1999 to August 2001. A total of 160 macrobenthic species from eight major groups represented the macrofauna of the Minicoy Island. Of the identified taxa, molluscs 70 (gastropods 41.46%, bivalves 7.5%), polychaetes 27 (16.88%), crustaceans 30 (18.75%), echinoderms 11 (6.88%) and remaining others. Average seasonal abundance of benthic macrofauna ranged from 219 to 711 ind./m2, species diversity varied from 1.45 to 3.64 bits per individual, species richness index ranged from 4.01 to 26.17, evenness 0.69 to 1.66. In general, the higher abundance and species diversity was noticed in southern seagrass stations and northern seagrass stations, but in the mangrove stations comparatively low species diversity was observed. Three-way analysis of variance indicated that all communities resulted as being significantly different between seagrass and mangrove station, mainly when the seasonal interaction was considered. Multivariate analyses were employed to help define benthic characteristic and the relationship between environmental parameters at the six monitoring stations. Results of cluster analyses and multidimensional scale plot suggest that for mangrove region, different physiographic provinces, lower salinity, dissolved oxygen and sediment biotic structure have a higher influence on the species composition and diversity than other oceanographic conditions.

Biodiversity and community composition of sediment macrofauna associated with deep-sea Lophelia pertusa habitats in the Gulf of Mexico

Scleractinian corals create three-dimensional reefs that provide sheltered refuges, facilitate sediment accumulation, and enhance colonization of encrusting fauna. While heterogeneous coral habitats can harbor high levels of biodiversity, their effect on the community composition within nearby sediments remains unclear, particularly in the deep sea. Sediment macrofauna from deep-sea coral habitats (Lophelia pertusa) and non-coral, background sediments were examined at three sites in the northern Gulf of Mexico (VK826, VK906, MC751, 350–500m depth) to determine whether macrofaunal abundance, diversity, and community composition near corals differed from background soft-sediments. Macrofaunal densities ranged from 26 to 125 individuals 32cm−2 and were significantly greater near coral versus background sediments only at VK826. Of the 86 benthic invertebrate taxa identified, 16 were exclusive to near-coral habitats, while 14 were found only in background sediments. Diversity (Fisher’s α) and evenness were significantly higher within near-coral sediments only at MC751 while taxon richness was similar among all habitats. Community composition was significantly different both between near-coral and background sediments and among the three primary sites. Polychaetes numerically dominated all samples, accounting for up to 70% of the total individuals near coral, whereas peracarid crustaceans were proportionally more abundant in background sediments (18%) than in those near coral (10%). The reef effect differed among sites, with community patterns potentially influenced by the size of reef habitat. Taxon turnover occurred with distance from the reef, suggesting that reef extent may represent an important factor in structuring sediment communities near L. pertusa. Polychaete communities in both habitats differed from other Gulf of Mexico (GOM) soft sediments based on data from previous studies, and we hypothesize that local environmental conditions found near L. pertusa may influence the macrofaunal community structure beyond the edges of the reef. This study represents the first assessment of L. pertusa-associated sediment communities in the GOM and provides baseline data that can help define the role of transition zones, from deep reefs to soft sediments, in shaping macrofaunal community structure and maintaining biodiversity; this information can help guide future conservation and management activities.

Temperature–parasitism synergy alters intertidal soft-bottom community structure

The abundant amphipod Corophium volutator is an ecosystem engineer in soft-bottom intertidal communities due to its grazing and bioturbation activity. However, the amphipod commonly serves as second intermediate host for detrimental microphallid trematodes. This host–parasite association is potentially very sensitive to climate change as the transmission rate of larval trematodes (cercariae) from first intermediate hosts (mud snails) to amphipods, and hence infection intensity-dependent amphipod mortality, generally accelerates with increasing temperature. Given the ecosystem engineering role of C. volutator, we hypothesized that elevated temperature, indirectly through increased parasite-induced amphipod mortality, significantly affects the structure of the surrounding benthic community. To test this, we performed a three-month outdoor mesocosm experiment exposing a natural soft-bottom community of benthic plants and animals to four different treatments: relatively low mean water temperature (18°C) with low (<4%) and high (c. 31%) trematode prevalence in the snail population, and relatively high mean water temperature (22°C) with low and high trematode prevalence. Both temperature and snail parasitism had a significant impact on amphipod abundance and resulted in their almost complete eradication at the warm temperature with high parasitism. Aside from the amphipod hosts, increased temperature affected the abundance of eight faunal species out of 22 in total (36%), whereas increased level of parasitism or the parasite–temperature interaction influenced the density of three species (14%). The treatment-determined Corophium abundance played an isolated role for several species, particularly the polychaetes Hediste diversicolor (positive) and Polydora ligni (negative). Regarding primary producers, the overall frequency distribution of 21 species of benthic diatoms differed between all four treatments. Species-specific effects were few and weak, however, and microalgal abundance (chlorophyll-a) was statistically unaffected by treatments, together suggesting a rather resilient plant community towards the experimental perturbations. At the community level, the non-host macrofaunal diversity decreased with temperature in the low parasitism treatments whereas it increased with temperature in the high parasitism treatments. This suggests that sufficiently high levels of parasitism may turn a negative effect of elevated temperature on macrofaunal biodiversity into a positive effect. Hence, our experiment demonstrates that the synergy between parasitism and a relevant temperature increase, e.g. in lieu of climate oscillations or global warming, may have broad ecological consequences for the organization and function of soft-bottom communities, in part through elevated parasite-induced mortality of a central community member.