Daniela Zeppilli

Is the meiofauna a good indicator for climate change and anthropogenic impacts

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research.

Seafloor heterogeneity influences the biodiversity-ecosystem functioning relationships in the deep sea.

Theoretical ecology predicts that heterogeneous habitats allow more species to co-exist in a given area. In the deep sea, biodiversity is positively linked with ecosystem functioning, suggesting that deep-seabed heterogeneity could influence ecosystem functions and the relationships between biodiversity and ecosystem functioning (BEF). To shed light on the BEF relationships in a heterogeneous deep seabed, we investigated variations in meiofaunal biodiversity, biomass and ecosystem efficiency within and among different seabed morphologies (e.g., furrows, erosional troughs, sediment waves and other depositional structures, landslide scars and deposits) in a narrow geo-morphologically articulated sector of the Adriatic Sea. We show that distinct seafloor morphologies are characterized by highly diverse nematode assemblages, whereas areas sharing similar seabed morphologies host similar nematode assemblages. BEF relationships are consistently positive across the entire region, but different seabed morphologies are characterised by different slope coefficients of the relationship. Our results suggest that seafloor heterogeneity, allowing diversified assemblages across different habitats, increases diversity and influence ecosystem processes at the regional scale, and BEF relationships at smaller spatial scales. We conclude that high-resolution seabed mapping and a detailed analysis of the species distribution at the habitat scale are crucial for improving management of goods and services delivered by deep-sea ecosystems.

Cosmopolitanism and Biogeography of the Genus Manganonema (Nematoda: Monhysterida) in the Deep Sea

Simple Summary The deep sea comprises more than 60% of the Earth surface, and likely represents the largest reservoir of as yet undiscovered biodiversity. Nematodes are the most abundant taxon on Earth and are particularly abundant and diverse in the deep sea. Nevertheless, knowledge of their biogeography especially in the deep sea is still at its infancy. This article explores the distribution of the genus Manganonema in the deep Atlantic Ocean and Mediterranean Sea providing new insights about this apparently rare deep-sea genus. Abstract Spatial patterns of species diversity provide information about the mechanisms that regulate biodiversity and are important for setting conservation priorities. Present knowledge of the biogeography of meiofauna in the deep sea is scarce. This investigation focuses on the distribution of the deep-sea nematode genus Manganonema, which is typically extremely rare in deep-sea sediment samples. Forty-four specimens of eight different species of this genus were recorded from different Atlantic and Mediterranean regions. Four out of the eight species encountered are new to science. We report here that this genus is widespread both in the Atlantic and in the Mediterranean Sea. These new findings together with literature information indicate that Manganonema is a cosmopolitan genus, inhabiting a variety of deep-sea habitats and oceans. Manganonema shows the highest diversity at water depths >4,000 m. Our data, therefore, indicate that this is preferentially an abyssal genus that is able, at the same time, to colonize specific habitats at depths shallower than 1,000 m. The analysis of the distribution of the genus Manganonema indicates the presence of large differences in dispersal strategies among different species, ranging from locally endemic to cosmopolitan. Lacking meroplanktonic larvae and having limited dispersal ability due to their small size, it has been hypothesized that nematodes have limited dispersal potential. However, the investigated deep-sea nematodes were present across different oceans covering macro-scale distances. Among the possible explanations (hydrological conditions, geographical and geological pathways, long-term processes, specific historical events), their apparent preference of colonizing highly hydrodynamic systems, could suggest that these infaunal organisms are transported by means of deep-sea benthic storms and turbidity currents over long distances.

Changes in nematode communities in different physiographic sites of the Condor Seamount (North-East Atlantic Ocean) and adjacent sediments

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

Characteristics of meiofauna in extreme marine ecosystems: a review

Extreme marine environments cover more than 50% of the Earth’s surface and offer many opportunities for investigating the biological responses and adaptations of organisms to stressful life conditions. Extreme marine environments are sometimes associated with ephemeral and unstable ecosystems, but can host abundant, often endemic and well-adapted meiofaunal species. In this review, we present an integrated view of the biodiversity, ecology and physiological responses of marine meiofauna inhabiting several extreme marine environments (mangroves, submarine caves, Polar ecosystems, hypersaline areas, hypoxic/anoxic environments, hydrothermal vents, cold seeps, carcasses/sunken woods, deep-sea canyons, deep hypersaline anoxic basins [DHABs] and hadal zones). Foraminiferans, nematodes and copepods are abundant in almost all of these habitats and are dominant in deep-sea ecosystems. The presence and dominance of some other taxa that are normally less common may be typical of certain extreme conditions. Kinorhynchs are particularly well adapted to cold seeps and other environments that experience drastic changes in salinity, rotifers are well represented in polar ecosystems and loriciferans seem to be the only metazoan able to survive multiple stressors in DHABs. As well as natural processes, human activities may generate stressful conditions, including deoxygenation, acidification and rises in temperature. The behaviour and physiology of different meiofaunal taxa, such as some foraminiferans, nematode and copepod species, can provide vital information on how organisms may respond to these challenges and can provide a warning signal of anthropogenic impacts. From an evolutionary perspective, the discovery of new meiofauna taxa from extreme environments very often sheds light on phylogenetic relationships, while understanding how meiofaunal organisms are able to survive or even flourish in these conditions can explain evolutionary pathways. Finally, there are multiple potential economic benefits to be gained from ecological, biological, physiological and evolutionary studies of meiofauna in extreme environments. Despite all the advantages offered by meiofauna studies from extreme environments, there is still an urgent need to foster meiofauna research in terms of composition, ecology, biology and physiology focusing on extreme environments.

Biodiversity and ecology of meiofauna in extreme and changing environments

Meiofauna (small interstitial animals and protists living in aquatic sediments) are ubiquitous. Owing to their high abundance and diversity, widespread distribution, rapid generation times and fast metabolic rates, meiofaunal organisms are important contributors to ecosystem processes and functions, including nutrient cycling and provision of food to higher t rophic leve ls , among others (Woodward 2010; Schratzberger and Ingels 2017). Meiofauna, however, have typically received less attention than the larger and more easily studied macroand megafauna, and more needs to be done to train the next new generation of meiobenthologists. In order to bridge this gap, the second meiofauna summer school, BMeioScool2016 a dive in a microscopic world^, was held in Brest, France, 27 June −1 July 2016, and attracted 131 scientists and students from 26 countries (Fig. 1; https://meioscool2016.sciencesconf.org/). Like the first summer school held in 2013, the objectives of MeioScool2016 were to bring together meiofaunal experts in several meiofauna-related sub-disciplines from all over the world to: (1) increase awareness of researchers, students and general public to the fundamental role of meiofauna in marine ecosystems from the coastal zone to the deep sea, and (2) train students and researchers in the identification and description of meiofaunal communities through several complementary disciplines (taxonomy, ecology, molecular biology). The first 2 days were devoted to oral and poster presentations by invited speakers, researchers, and students, while the three other days consisted of practical workshops and field and laboratory work. Two sessions of this summer school were devoted to the meiofauna of extreme and changing environments: BSession 4: Deep-sea and extreme meiofauna^ and BSession 5: Meiofauna response to anthropogenic impacts^. Extreme environments (i.e., environments characterised by one or more environmental parameters permanently close to the lower or upper limits for life; CAREX 2011) cover more than 50% of the Earth’s surface (Zeppilli et al. 2017), and offer many opportunities for investigating the biological responses and adaptations of organisms to stressful life conditions (Rothschild and Mancinelli 2001). The fauna adapted to extreme environments may be particularly sensitive to environmental changes (Catalan et al. 2006; Bellard et al. 2012) and can be used as biological indicators of pollution and global change (Zeppilli et al. 2015). Among the communities present in extreme natural environments, we constantly find meiofauna organisms. This Special Issue of Marine Biodiversity comprises studies and reviews related to extreme environments including taxonomy of extreme meiofauna, and biodiversity and ecology of meiofauna in extreme or changing environments (Table 1). The first contribution to this Special Issue provides a description of a new marine arthrotardigrade species (GomesJúnior et al. 2017). Ligiarctus alatus sp. nov. was discovered in sediments of the Brazilian continental shelf in the Southwestern Atlantic Ocean, from sites located in the major oil extraction basins in Brazil (Campos and Potiguar basins). The review of Rosli et al. (2017) describes trends in the ecology of deep-sea meiofauna with focus on patterns and processes at small to regional spatial scales described in studies published since the last review of deep-sea meiofauna of Soltwedel (2000), and highlights areas needing further research. Zeppilli et al. (2017) present an integrated review of the biodiversity, ecology and physiological responses of marine meiofauna inhabiting extreme marine environments, including mangroves, submarine caves, polar ecosystems, hypersaline areas, hypoxic/anoxic environments, hydrothermal vents, cold seeps, carcasses/sunken woods, deep-sea canyons, * Daniela Zeppilli Daniela.Zeppilli@ifremer.fr

Occurrence of Chromadorita regabi sp. nov. (Nematoda: Adenophorea), a nematode egg predator of Alvinocaris muricola (Crustacea: Decapoda: Caridea: Alvinocarididae) from a deep cold seep area of the Gulf of Guinea

Abstract Several individuals belonging to a new species of the genus Chromadorita (Nematoda: Adenophorea) were collected in a cold-seep area in the Gulf of Guinea during two French cruises: BIOZÄIRE 2 (2001) and BIOZAÏRE 3 (2003–2004) on board the R/V L’Atalante. In this area, rich chemosynthetic benthic communities have been discovered at 3150 m depth in the large pockmark field named Regab. Chromadorita regabi sp. nov. was found among the eggs in ovigerous specimens of the shrimp Alvinocaris muricola. The combination of long size (1500–2200 µm), nine strong preanal papillae and relatively small dorsal tooth with weak musculature distinguishes this species from all known congeneric ones. An identification key to all known species of Chromadorita is provided. http://zoobank.org/urn:lsid:zoobank.org:pub:68B32253-D4B4-45EB-B4F8-4F7B015E6FCC

A Nematode of the Mid-Atlantic Ridge Hydrothermal Vents Harbors a Possible Symbiotic Relationship

Deep-sea hydrothermal vent meiofauna have been the focus of recent research and the discovery of an abundant well-adapted free-living marine nematode on the Mid-Atlantic Ridge offers new perspectives on adaptations to the vent environment. Indeed, knowledge concerning biological interactions of microbes and meiofauna in marine extreme environments is scarce, especially for nematodes. In this study, we used microscopic observations [fluorescence in situ hybridization (FISH) and scanning electron microscopy (SEM)] and metabarcoding of 16S rRNA to characterize the bacterial community of the nematode species Oncholaimus dyvae, an overlooked but ecologically important vent organism. Detection of bacteria in the buccal cavity and on the cuticle (SEM) and epibionts in its intestine (FISH) suggests that O. dyvae harbors its own bacterial community. Molecular results and phylogenetic analysis show that bacteria associated with this species are related to symbiotic lineages typical of hydrothermal vent fauna, such as sulfur-oxidizing bacteria related to Epsilonproteobacteria and Gammaproteobacteria. This multi-approach study suggests a potential symbiotic role of bacteria with its nematode host and opens new research perspectives on vent meiofauna.

Meiofauna international workshop “MeioScool 2013: a dive into a microscopic world”

This issue contains selected studies presented during the Meiofauna International Workshop “MeioScool 2013: a dive in a microscopic world”, held in Brest, France, 26–29 November 2013. The main objectives of MeioScool were to bring together several meiofaunal experts in several meiofauna-related sub-disciplines from around the world in order to increase awareness among researchers, students and the general public of the fundamental role of meiofauna in marine ecosystems from the coastal zone to abyssal depths; and to train students and researchers in the identification and description of meiofauna through several complementary disciplines (taxonomy, ecology, molecular biology), and stimulate a new generation of meiobenthologists. The MeioScool workshop lasted 4 days. The first 2 days were devoted to conferences, while the other 2 days were focused on field and laboratory work (sampling, extraction, morphological and molecular identification of major meiofaunal taxonomic groups). The workshop attracted 126 scientists and students from 26 countries to study a wide range of aspects and topics related to meiofauna. This Special Issue of Marine Biodiversity presents selected results of the workshop, grouped in sections by topic as follows: 1) meiofauna taxonomy, with six contributions; 2) meiofauna ecology, with seven contributions; and 3) meiofauna sampling and identification methods, with three contributions.