Roberto Sandulli

Meiofauna of the Adriatic Sea: present knowledge and future perspectives

Owing to technical problems and difficult taxonomic identification, meiofauna have been generally less studied than macrofauna. However, the role of meiofauna in marine ecosystem functioning, and their effective and rapid response to anthropogenic alterations and climatic changes have recently been acknowledged, leading to increasing scientific and applied interest. At present, systematic and biogeographic knowledge of the meiofauna of the Adriatic Sea is extremely heterogeneous, because most of the data are limited to a few taxa and the sampled areas are scattered, being located mainly in the coastal areas of the northern basin. Analysis of the composition and distribution of meiobenthic groups in the Adriatic Sea highlights the presence of several endemisms. Meiofauna also include bioindicator taxa, which allow assessment of the quality of marine sediments; this is particularly useful in systems characterised by the synergistic effect of different forms of anthropogenic impact, such as the Adriatic basin. Current knowledge about the ecology of the meiofauna and use of this component in applied ecological studies, along with the availability of a standardised protocol for the analysis of meiofaunal assemblages, allows us to recommend formal acknowledgement of the need to integrate information derived from the analysis of macrofauna with information derived from the study of meiofauna. Future research based on the simultaneous use of both of these benthic components will allow faster and more accurate evaluation of the response of coastal marine ecosystems to anthropogenic disturbance.

Responses of meiobenthic communities along a gradient of sewage pollution

Abstract The composition of meiofauna along an organic pollution gradient in the Gulf of Salerno (Italy) was studied. Sediment samples for meiofauna and physicochemical parameters (Redox potential, particulate organic carbon, chlorophyll a , and phaeopigments) were collected quarterly at various distances from a sewage outfall. Results of the environmental analyses show the increasingly stressed conditions towards the outfall. Meiofaunal data show that nematodes increase in abundance along a gradient of increasing organic enrichment until the environmental conditions excessively deteriorate in the immediate vicinity of the sewage outfall, where this taxon is absent. Interstitial (mesobenthic) and epi-endobenthic copepods show a differential response: mesobenthic forms, totally absent within 50 m from the outfall, gradually enhance their numbers moving away from the pollution source; while the epi-endobenthic copepods increase in abundance along a gradient of increasing organic enrichment, reaching the highest densities in proximity of the sewage outfall.

Effects of organic enrichment on meiofauna: a laboratory study

Abstract An 84 day laboratory experiment indicates the decline of intertidal meiofauna abundance may be directly related to treatment level and time of exposure to sewage sludges. The observed changes revealed a marked decrease of nematodes and total disappearance of mesobenthic harpacticoids while the non-interstitial copepod species were little affected. The possibility of a new interpretation of the Nematode/Copepod ratio as an index of organic pollution in sediments is discussed.

Meiobenthic biodiversity in areas of the Gulf of Taranto (Italy) exposed to high environmental impact

Biological and chemical parameters (meiofauna density and diversity, redox profiles) were investigated in relation to the environmental conditions of sediments in the Gulf of Taranto. Sediment cores were collected from 42 stations from −5 to −20u200am depth, in 1995, 2000 and 2001. Meiofauna abundance and diversity were significantly lower in the Mar Piccolo, the area most heavily polluted by organic loads; in Mar Grande and Chiatona areas the same parameters showed slightly higher values. Eh profiles revealed anoxic conditions in coastal sediments impacted by industrial and sewage discharges. Meiofauna density ranged from 186 to 1370 individualsu2009×u200910u200acm−2. Generally, over 80% of total meiofauna was composed of nematodes; the contribution of other taxa is much less important. The widespread presence of the lessepsian Chlorophyte Caulerpa racemosa since 1996, seemed to enhance the abundance of meiofauna, and increased microhabitat complexity, but reduced diversity of some taxa, such as the meiobenthic crustaceans. Comparing 2001–2002 data with 1995 (before C. racemosa invasion), the recent decrease of some groups (ostracods, amphipods, isopods, tanaids and cumaceans) was markedly evident. In conclusion, our findings confirm the chronically degraded environmental conditions in the Gulf of Taranto, and draw attention to the further contribution of C. racemosa invasion.

Standardization proposal for the mapping of Caulerpa taxifolia expansion in the Mediterranean sea

Fourteen years after the first observation of Caulerpa taxifolia (Valh) C. Agardh in the northwestern Mediterranean Sea, this green alga of tropical origin is now present in five countries (Spain, France, Monaco, Italy and Croatia). By the end of 1997, more than 46 km2, at depths of between 0 and 50 m, were found to be affected by this expansion. A standardization of the cartographic procedure is proposed here. Such a standardization is necessary to compare maps produced by various organizations from different countries. For a given independent station, it is based on the definition of three levels of colonization: n• n- Level I refers to a station where one or several colonies less than 100 m apart cover a total surface area inferior to 1000 m2; n n• n- Level II refers to a station where several colonies less than 250 m apart totally cover more than 1000 m2 with fragments and small colonies dispersed over a surface area inferior to 10 ha; n n• n- Level III is attained when several large colonies are dispersed over a surface area superior to 10 ha, with a total covered surface of more than 1000 m2, impossible to map with precision due to its size. n n n n nFor each of these colonization levels, descriptive parameters can be used to precisely describe the situation: covered surface area, dispersion surface (i.e. “affected” zone), estimation of very large affected zones (i.e. “concerned” zones) and the portions of the coastline along which an affected or concerned zone can be found.

Meiobenthic communities in the shallow subtidal of three Italian Marine Protected Areas

Abstract Meiofauna assemblages of three Italian Marine Protected Areas (MPAs), Miramare (Trieste, Friuli-Venezia Giulia), Porto Cesareo (Lecce, Apulia) and Capo Caccia (Sassari, Sardinia), were investigated. Sediment samples were collected during summer 2005 in the shallow subtidal (1–4 m depth). The meiofauna was primarily represented by Nematoda and Copepoda. The results showed that significant differences in meiofauna communities abundances were found among the three Italian MPAs, and in particular between Capo Caccia and Porto Cesareo (3840u2009±u2009422 SE individuals·10 cm–2 at Miramare, 5716u2009±u2009857 SE ind.·10 cm–2 in Porto Cesareo, and 1063u2009±u2009289 SE ind.·10 cm–2 in Capo Caccia). These differences were mainly due to a clear change in nematodes and copepods abundances in the two MPAs. Meiofauna diversity was not significantly different among the three MPAs. The analysis on nematode communities showed a dominance of deposit feeders in Porto Cesareo (Anoplostoma, Daptonema and Theristus), while in the marine reserves of Miramare and Capo Caccia epigrowth feeding nematodes, and predators/omnivores were dominant (Mesacanthion, Marylynnia). The results reported here represent a new contribution to the knowledge of the Mediterranean meiofauna and nematode assemblages structure and composition.

Taxonomic distinctness in Mediterranean marine nematodes and its relevance for environmental impact assessment

Taxonomic distinctness has been applied successfully for the exploration of biodiversity patterns, yet its relevance in environmental impact assessment is far from being unquestioned. In this study, we assessed the potential of taxonomic distinctness to discern perturbed and unperturbed sites by analysing Mediterranean nematode assemblages. Geographic and habitat-related effects on the performance of the index were also explored. Above all, our findings do not corroborate the conjecture that taxonomic distinctness could be largely unaffected by natural variability, habitat features, and biogeographic context, casting doubts on potential generalization concerning its application as an indicator of environmental stress. Taxonomic distinctness represents an excellent metric to identifying taxonomic properties of ecological systems but, as for other ecological indices, it should be viewed as a complementary tool in environmental impact assessment, due to its sensitiveness to specific environmental features of systems being investigated.

Heterotardigrada of Two Submarine Cavesin S. Domino Island (Tremiti Islands) in the Mediterranean Sea with the Description of Two New Species of Stygarctidae

Abstract Two new species of the marine tardigrade family Stygarctidae, Parastygarctus mediterranicus and Pseudostygarctus rugosus , were recorded during an investigation of the meiofauna of two subtidal caves in San Domino Island (Tremiti Archipelago) in July and October 1997, July and October 1998 and May 1999. The description of the two species is given, and their phylogenetic relationships within the subfamily Stygarctinae are discussed. Bioecological information on the tardigrade fauna of the two caves are also supplied.

Taxonomic and functional biodiversity variations of meiobenthic and nematode assemblages across an extreme environment: a study case in a Blue Hole cave

Abstract In this paper we have explored for the first time the biodiversity pattern of the meiobenthic assemblage in a Blue Hole of the Maldivian Archipelago. The cave is characterised by a marked change of the chemical water parameters below 50 m of depth, with a relevant increase in hydrogen sulfide, carbon dioxide, and sulfates (H2S, CO2 and SO42–). Thus, three stations were selected above and two below the chemo-thermocline in order to test the possible effects of the chemical variations on the meiobenthos. The difficulty of adaptation to these environmental conditions is clearly suggested by the presence of only a few dominant meiobenthic taxa in the bottom of the cave. However, meiobenthic organisms seemed more resistant than macrobenthos, which disappeared completely below this depth. The nematode assemblage was mainly represented by Xyalidae, Desmodoridae, Comesomatidae and Linhomoeidae. A high level of confinement of nematode genera at the different depths has been documented. In the upper part, their structure and biodiversity were comparable to those of the Maldivian subtidal habitats characterised by fine coralline sediments, while a notable dominance was detected in the bottom. The Blue Hole features also influenced the functional traits of the nematode assemblage with a documented increasing number of general opportunists and decrease of Maturity Index. The dominance of non-selective deposit feeders supports the hypothesis of a high amount of organic matter accumulated on the sea bottom of the cave.

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.