Concordance degrees in macrozoobenthic monitoring programmes using different sampling methods and taxonomic resolution levels

Optimization of the taxonomic resolution of an indicator taxon for cost-effective ecological monitoring: Perspectives from a heterogeneous tropical coastline

An important requirement towards formulating appropriate management and conservation measures for biological diversity is to devise efficient and cost-effective monitoring protocols that yield coherent data. Environmental monitoring investigations have been typically based on species level responses of biodiversity to environmental disturbances. Considering that this exercise is cost-intensive and the species identification keys are unavailable for some geographical areas, efforts are now afoot to test the efficacy of supra-specific taxa in resolving distribution patterns of biota, analogous to that of species. This study was aimed at testing the efficacy of Taxonomic Sufficiency (TS), a data reduction technique, in deciphering spatio-temporal variations of macrobenthos in the tropical coastal waters of northwest India. The macrobenthic indicator taxon, Polychaeta, was analyzed at five transects that included two marine protected areas, during the three major seasons. The consistency of spatio-temporal trends of polychaete assemblages, derived from four taxonomic levels and subjected to five types of data transformation was scrutinized. Univariate indices indicated that coarser taxonomic levels except order, maintained the indicative responses spatio-temporally, similar to the species level. Spatial variability was appropriately indicated by all data matrices. Temporal variation was evident only with family data subjected to fourth root or log data transformations. The TS approach succeeded in this tropical ecoregion owing to the consistent and sizable proportion of monotypic polychaete taxon and uniformity in responses of the constituents of higher polychaete taxon. CCA results revealed that a similar set of environmental variables influenced the polychaete distribution at all the taxonomic levels; however, spatial variations detected at species level diminished with reduced taxonomic breadth. Results indicated that meaningful robust data for deriving coastal management initiatives can be achieved cost-effectively by the adoption of TS approach for the ecologically and economically important 2360 km long northwest Indian coastline.

Perception of faunal circadian rhythms depends on sampling technique

Ecologists aim at disentangling how species vary in abundance through spatial and temporal scales, using a range of sampling techniques. Here, we investigated the circadian rhythm of seagrass-associated decapod crustaceans through three sampling techniques. Specifically, we compared the abundance, biomass and structure of seagrass-associated decapod assemblages between the day and night using a hand net, an airlift pump and baited traps. At night, the hand-net consistently collected a larger total abundance and biomass of decapods, what resulted in significant diel differences, which were detected for the total biomass, but not for the total abundance, when decapods were sampled through an airlift pump. Traps, however, collected a larger total abundance, but not total biomass, of decapods during the night. In summary, our perception of faunal diel rhythms is notably influence by the way organisms are sampled.

Benefits and shortcomings of non-destructive benthic imagery for monitoring hard-bottom habitats

Hard-bottom habitats with complex topography and fragile epibenthic communities are still not adequately considered in benthic monitoring programs, despite their potential ecological importance. While indicators of ecosystem health are defined by major EU directives, methods commonly used to measure them are deficient in quantification of biota on hard surfaces. We address the suitability of seafloor imaging for monitoring activities. We compared the ability of high-resolution imagery and physical sampling methods (grab, dredge, SCUBA-diving) to detect taxonomic and functional components of epibenthos. Results reveal that (1) with minimal habitat disturbance on large spatial scales, imagery provides valuable, cost-effective assessment of rocky reef habitat features and community structure, (2) despite poor taxonomic resolution, image-derived data for habitat-forming taxa might be sufficient to infer richness of small sessile and mobile fauna, (3) physical collections are necessary to develop a robust record of species richness, including species-level taxonomic identifications, and to establish a baseline.

Congruency analysis of biofilm-dwelling ciliates as a surrogate of eukaryotic microperiphyton for marine bioassessment

Biofilm-dwelling ciliates are primary components of the eukaryotic microperiphyton in both species composition and community structure. To evaluate the congruency of biofilm-dwelling ciliates as potential surrogates of the eukaryotic microperiphyton, a dataset was collected every month at four stations from the coastal waters of the Yellow Sea, northern China, and assessed. Sufficient species abundance data were obtained for ciliated protozoans at high taxonomic levels up to the family level, indicating a significant variation along the gradient of contamination. Correlation analyses revealed that the taxa richness of these matrices can explain > 85% of the variance in that of the full species dataset. The cost/benefit analysis showed that the protozoan subset at low resolutions up to the family level may be used as a potential surrogate of the original dataset. Thus, we suggest that the protozoan assemblages at genus- and/or family-level resolutions may be useful, cost-efficient surrogates of the original dataset for bioassessment in marine ecosystems.

Insights into assessing environmental quality status using potential surrogates of biofilm-dwelling ciliate fauna in coastal waters

To determine potential surrogates of biofilm-dwelling ciliate fauna for assessing water quality, a dataset of coastal waters of the Yellow Sea was studied. Samples were collected monthly at a depth of 1 m from four sampling stations during a 1-year cycle (August 2011-July 2012), northern China. The ciliate communities at low taxonomic resolutions up to family level were significantly correlated with the full ciliate fauna at species-level resolution and represented a significant spatial variation in relation to the environmental changes. The presence/absence resolutions up to genus level maintained sufficient information of the ciliate species-abundance matrix. The vagile and sessile ciliate assemblages were significantly correlated with the full ciliate communities but only the latter maintained sufficient information with a significant spatial variation in response to the environmental stress. Correlation analyses showed that the taxon richness indices of potential surrogates at genus- and family-level resolutions can explain >95 % of the variance in that of the full species pool. Thus, it is suggested that the taxonomic resolutions up to family level may be a robust time-efficient surrogate of whole periphytic ciliate communities for assessing water quality status and would allow improving sampling strategies of large spatial scale monitoring programs, using biofilm-dwelling ciliates, in coastal waters.

Macrobenthic community for assessment of estuarine health in tropical areas (Northeast, Brazil): review of macrofauna classification in ecological groups and application of AZTI Marine Biotic Index

The aim of the present study was to investigate the ecological quality of tropical estuaries on the northeastern coast of Brazil using the AMBI. Macrofauna classification based on ecological groups was reviewed using the Indicator Value (IndVal) coefficient. The results indicate that the ecosystems exhibit some level of disturbance. Most sites are situated between slightly-moderately disturbed boundaries due to the higher proportion of Nematoda (assigned here as Ecological Group I) and of Oligochaeta and Tubificidae (both classified as Ecological Group V). The AMBI proved efficient in evaluating environmental status, although the applicability of this index requires adjustments regarding some species in ecological groups. The present study also highlights the merits of the IndVal method for examining the assignments of species/taxa to an ecological group and demonstrates the validity of this coefficient is an assessment tool. Moreover, the complementary use of different methods is recommended for the assessment of ecosystem quality.

An approach to determining potential surrogates for analyzing ecological patterns of planktonic ciliate communities in marine ecosystems

INTRODUCTION

In order to identify a potential surrogate of planktonic ciliate communities for marine bioassessments and evaluating biological conservations, the different taxonomic/numerical resolutions and taxa as surrogates were studied in Jiaozhou Bay, northern China during a 1-year cycle (June 2007-May 2008).

MATERIALS AND METHODS

Samples were collected biweekly from a depth of 1 m at each of five sites. A range of physicochemical parameters were also measured in order to determine water quality.

RESULTS

The genus- and family-level resolutions maintained sufficient information to evaluate the ecological patterns of the ciliate communities in response to environmental status. The non-loricate oligotrichous ciliate assemblages in both abundance and occurrence may be used as a surrogate of planktonic ciliate communities. Heavy data transformations were an optimal strategy for the species level of planktonic ciliates, while mild data transformations were for the higher. The ordination patterns based on species biomass, occurrence, and biomass/abundance ratio matrices were significantly consistent with that of species abundance data.

CONCLUSION

The results suggest that the use of simplifications at both taxonomic and numerical resolutions are time-efficient and would allow improving sampling strategies of large spatial/temporal scale monitoring programs and biological conservation researches in the marine ecosystem with a relative paucity of scientists.

Different levels of macroalgal sampling resolution for pollution assessment

The effects of using reduced sampling resolutions to study macroalgal vegetation patterns have not been studied sufficiently. Here, we test the influence of taxonomic resolution level, removal of occasional species, aggregation of species abundances into functional groups and data transformation in the detection of a long-term recovery process by phytobenthic intertidal assemblages. Results indicate that the aggregation of species data into the genus level has very little influence. Likewise, almost any significant information is lost when occasional algae are removed. Analyses at the level of families and orders still clearly detect differences between highly degraded and reference vegetation. By contrast, analyses based on class and functional group abundances capture quite different information. The effect of transformation is similar at the different taxonomic levels. Most surrogate measures properly reflect changes in diversity. It is concluded that genus level is the most appropriate surrogate approach for detecting the recovery process.

Taxonomic sufficiency in the detection of natural and human-induced changes in marine assemblages: a comparison of habitats and taxonomic groups

Taxonomic Sufficiency (TS) is a promising analysis technique, particularly in light of the current need for rapid and reliable procedures in marine impact assessment and monitoring. However, generalizations are still difficult and there are few studies comparing the effectiveness of TS under different environmental settings. The present study investigates whether reduced taxonomy can be used to detect natural and human-driven patterns of variation in mollusk and polychaete assemblages from subtidal soft and hard bottoms in the Mediterranean. Results showed that, unlike in polychaetes, mollusk families represent effective taxonomic surrogates across a range of environmental contexts. These findings suggest that the mechanisms behind TS in mollusks could act homogeneously across habitats and environmental conditions. In contrast, multiple factors could interact to determine the robustness of polychaetes to taxonomic aggregation. This study highlights the need to go beyond the current pragmatism in this field of work and focus on the reasons underlying TS effectiveness in order to provide a general framework on the application of taxonomic surrogates in marine systems.

Human exclusion from rocky shores in a mediterranean marine protected area (MPA): an opportunity to investigate the effects of trampling

The effect of human trampling on the abundance of small invertebrates inhabiting rocky shallow bottoms was studied at Asinara Island MPA. To this aim we have conducted two experiments. The first was a quantitative study and tested the hypothesis that small invertebrates are more abundant at no-entry locations than at the location visited by tourists through time (before, during and after tourist season). The second was a manipulative experiment and tested the hypothesis that the abundance of small invertebrates is indirectly related to experimental trampling intensities. The effect due to tourist visitation was not highlighted on overall assemblages, suggesting that present seasonal tourist load at the MPA does not cause a significantly negative effect on the zoobenthic community studied. Although tourists exhibited trampling activity at the visited location, none of taxa examined showed a significant lower abundance during and strictly after the end of seasonal tourism peak in the visited location, rather than at control locations. However, results obtained with the second experiment suggested that the effects of different experimental trampling intensities on small invertebrates were variable among taxa. The experimental trampling caused immediate declines in the density of tanaids, nematodes, acari, bivalves, gammarids, echinoderms, isopods, and harpacticoids. For some of these taxa a recovery in abundance was observed within one month. This kind of data may offer important information to estimate the number of visitors compatible with the sensitivity of zoobenthic assemblages, and may substantially contribute to appropriate MPA management.

Taxonomic sufficiency and the increasing insufficiency of taxonomic expertise

Taxonomic sufficiency (TS) involves the identification of taxa only to a level of taxonomic resolution sufficient to permit the detection of changes in stressed assemblages. Recently, however, TS has been proposed also for conservation issues as a tool to estimate biodiversity over large areas and in poorly known environments. This paper briefly reviews the use of TS in environmental impact studies and the effects of TS on sampling procedures and data analyses. The risk of possible loss of information depending on TS and the studied environment are discussed. Concluding remarks deal with the dangers of loss of taxonomic expertise in marine biological studies and assess critically the proposal of TS as a tool to describe biodiversity at a taxonomic level higher than species.