The Mediterranean Sea is recognized as a marine biodiversity hotspot. This enclosed basin is facing several anthropogenic-driven threats, such as seawater warming, pollution, overfishing, bycatch, intense maritime transport and invasion by alien species. The present review focuses on the diversity and ecology of specific marine trophically transmitted helminth endoparasites (TTHs) of the Mediterranean ecosystems, aiming to elucidate their potential effectiveness as ‘sentinels’ of anthropogenic disturbances in the marine environment. The chosen TTHs comprise cestodes and nematodes sharing complex life cycles, involving organisms from coastal and marine mid/upper-trophic levels as definitive hosts. Anthropogenic disturbances directly impacting the free-living stages of the parasites and their host population demographies can significantly alter the distribution, infection levels and intraspecific genetic variability of these TTHs. Estimating these parameters in TTHs can provide valuable information to assess the stability of marine trophic food webs. Changes in the distribution of particular TTHs species can also serve as indicators of sea temperature variations in the Mediterranean Sea, as well as the bioaccumulation of pollutants. The contribution of the chosen TTHs to monitor anthropogenic-driven changes in the Mediterranean Sea, using their measurable attributes at both spatial and temporal scales, is proposed.

Free-living nematodes were investigated in the Mar Piccolo of Taranto (Ionian Sea), a semi-enclosed basin of strategic importance for its complex productive infrastructure but in need of remediation due to the alarming amounts of heavy metals and synthetic organic contaminants in the sediments. Abundance, genera composition, biodiversity and trophic traits of nematodes were related to the gradual transition from marine to more brackish conditions and to the varying levels of contaminants in different sub-areas of the basin. Nematodes were more abundant and diverse at the most marine site while low numbers and diversity characterized the most contaminated station. Going towards the innermost part of the basin, gradually increasing values of abundance and biodiversity were observed although the assemblage was susceptible to the organic enrichment caused by mussel farms. The use of nematodes as ecological indicators mirrored the response of the assemblage to the main patterns acting in the basin (High/Good scores at the most marine site and Poor/Bad scores at the most contaminated station), giving a clear indication of environmental quality to stakeholders/authority that can contribute to address remediation actions in contaminated sediments.

The ultimate measure of the success or failure of conservation initiatives in an area will be the ecological health of that area and the sustainability of institutions which support that ecological health. Heretofore, no comprehensive data has been presented about the current conservation state of the area known as the Heart of Borneo (HoB), a mostly intact subset of the island of Borneo, which is an international conservation priority. This paper identifies a set of indicators representative of the biodiversity status of the HoB; collecting and analysing data concerning these indicators and combining these data with supplemental conservation information should provide an accurate assessment of the overall conservation state of the HoB. Based on the indicators identified in this study, the general biodiversity status of the HoB is rated as good, or viable, although there are specific elements of concern. Using the threat indicators identified in this study, the overall threat level is medium. Major threats from industrial forest conversion and mining currently exist mainly on the edges of the HoB, but are likely to expand further inland without any intervention simply based on proximity. Though most habitats within (but not outside) the HoB are generally intact, the current protected area system is insufficiently representative of the natural ecosystems of the HoB area and its management effectiveness is as yet unknown.

Meiofauna assemblages were investigated at 15 stations on triplicated samples in the Uvea Atoll (Loyalty Islands) in relation to 9 selected environmental parameters. Spatial patterns and variability of meiofauna density were quantified according to location, macrofauna and nematode species assemblages. Meiofauna was dominated by ciliates and nematodes. Densities of total meiofauna and of most of the meiofauna taxa were significantly higher in the back reef North Pléiades stations than the leeward side of the Island. The highest correlation between biotic patterns and environmental parameters that best explains the pattern was with sediment thickness and to a lesser extent organic matter, C/N ratio and depth. One hundred and thirty-four nematode species were identified with four dominant species Chromadora macrolaimoides, an undescribed species of Bolbonema, Daptonema svalbardense and Prochromadorella septempapillata. Three significantly different nematode species assemblages were detected in two of the previously described macrofauna assemblages by cluster analysis and multidimensional scaling methods suggesting that nematodes are more sensible ecological indicators than macrofauna. Diversity indices based on dominance were not significantly different among the three nematode species assemblages but indices based on species richness and rarefaction were significantly higher leeward of Uvea Island. Estimates of total species richness showed no sign of stabilizing with sample size. However, rare species stabilized very quickly, whereas abundant species were added with increasing sampling coverage, indicating a high spatial variability of the local composition of nematodes.

Although the uses and merits of terrestrial insects as indicators have been extensively discussed, there is a lack of clear definition, goal directedness and hypothesis testing in studies in the field. In an attempt to redress some of these issues and outline an approach for further studies, three categories of terrestrial insect indicators, corresponding to differences in their application, are proposed, i.e. environmental, ecological and biodiversity indicators. The procedures in terrestrial insect bioindicator studies should start with a clear definition of the study objectives and proposed use of the bioindicator, as well as with a consideration of the scale at which the study is to be carried out. Bioindication studies are conducted at a variety of spatial and temporal scales within the context of earth-system processes, but the objectives of the study will largely determine the scale at which it would be optimally conducted. There is a tendency for studies to be conducted below their space-time scaling functions, giving them apparent predictability. The selection of potential indicator taxa or groups is then based on a priori suitability criteria, the identification of predictive relationships between the indicator and environmental variables and, most importantly, the development and testing of hypotheses according to the correlative patterns found. Finally, recommendations for the use of the indicator in monitoring should be made. Although advocating rigorous, long-term protocols to identify indicators may presently be questionable in the face of the urgency with which conservation decisions have to be made, this approach is critical if bioindicators are to be used with any measurable degree of confidence.