AZTI Marine Biotic Index Research Articles

Effects of intensive scallop mariculture on macrobenthic assemblages in Sishili Bay, the northern Yellow Sea of China

To elucidate the effects of scallop mariculture on the macrobenthic community in a moderate energy system, bimonthly samples from four transects along a distance gradient in Sishili Bay, the northern Yellow Sea of China, were investigated. Differences in macrobenthic community structure along the distance gradient were evaluated using univariate and multivariate analyses. The AZTI's Marine Biotic Index (AMBI) and multivariate-AMBI analyses indicated that the macrobenthic community suffered little disturbance from the scallop culture. Consistently, the results of two-way analysis of similarities demonstrated that macrobenthic communities showed no difference along the distance gradient, but were significantly affected by the sampling months and transects. This conclusion was also confirmed by other univariate and multivariate analyses. The concentration of total organic carbon was 17.27 +/- A 6.05 mg g(-1), which is below the dangerous threshold of 35 mg g(-1) toxic to benthic fauna. Combined results revealed that no detectable effects on the macrobenthic community were caused by intensive and long-term scallop culture in this moderate energy system. This is likely due to the influence of local hydrodynamics and it is recommended that intensive scallop farming be located in areas with strong tidal or current flows.

Model-Based Assessment of Estuary Ecosystem Health Using the Latent Health Factor Index, with Application to the Richibucto Estuary

The ability to quantitatively assess ecological health is of great interest to those tasked with monitoring and conserving ecosystems. For decades, biomonitoring research and policies have relied on multimetric health indices of various forms. Although indices are numbers, many are constructed based on qualitative procedures, thus limiting the quantitative rigor of the practical interpretations of such indices. The statistical modeling approach to construct the latent health factor index (LHFI) was recently developed. With ecological data that otherwise are used to construct conventional multimetric indices, the LHFI framework expresses such data in a rigorous quantitative model, integrating qualitative features of ecosystem health and preconceived ecological relationships among such features. This hierarchical modeling approach allows unified statistical inference of health for observed sites (along with prediction of health for partially observed sites, if desired) and of the relevance of ecological drivers, all accompanied by formal uncertainty statements from a single, integrated analysis. Thus far, the LHFI approach has been demonstrated and validated in a freshwater context. We adapt this approach to modeling estuarine health, and illustrate it on the previously unassessed system in Richibucto in New Brunswick, Canada, where active oyster farming is a potential stressor through its effects on sediment properties. Field data correspond to health metrics that constitute the popular AZTI marine biotic index and the infaunal trophic index, as well as abiotic predictors preconceived to influence biota. Our paper is the first to construct a scientifically sensible model that rigorously identifies the collective explanatory capacity of salinity, distance downstream, channel depth, and silt–clay content–all regarded a priori as qualitatively important abiotic drivers–towards site health in the Richibucto ecosystem. This suggests the potential effectiveness of the LHFI approach for assessing not only freshwater systems but aquatic ecosystems in general.

Assessing benthic ecological status in stressed Liaodong Bay (China) with AMBI and M-AMBI

Rapid economic development in recent decades has resulted in environmental degradation of Liaodong Bay, North China, where eutrophication is becoming more evident because of excess nutrients inputs. To assess the benthic ecological status in Liaodong Bay, AZTI’s Marine Biotic Index (AMBI) and multivariate-AMBI (M-AMBI) were applied using both benthic macroinvertebrate density and biomass data collected from Liaodong Bay in July 2007. This first application of AMBI and M-AMBI in Liaodong Bay showed that the nearshore areas of the bay, especially near river estuaries, were severely disturbed, with a clear gradient of disturbance decreasing seaward. Ecological status assessed from density and biomass data was quite similar. Significant relationships were also found between both indices and environmental variables in Liaodong Bay. Moreover, the spatial distributions of both AMBI and M-AMBI matched those of plotted eutrophication indices (EI) in the surface water layer, and significant linear correlations were found between both benthic indices and EI. In general, both AMBI and M-AMBI worked well on assessing the ecological status of Liaodong Bay under eutrophication stress due to excess nutrients inputs.

Classification of the ecological quality of the Aysen and Baker Fjords (Patagonia, Chile) using biotic indices

The AZTI’s marine biotic index (AMBI), an ecological indicator for managing estuarine and coastal waters worldwide, was tested in two fjords in Chilean Patagonia. The Aysen Fjord (42° Lat. S) supports intensive salmon farming in coastal ecosystems, while the Baker Fjord (48° Lat. S) is currently just beyond the limit of the southern expansion of salmon concessions. The ecological status of the Aysen Fjord was classified as good, while the status of the Baker Fjord was classified as high and unbalanced. These differences were consistent with our expectations, illustrating the effect of local environmental conditions and human activities, combined with river inputs into semi-confined fjords. This method is appropriate for the evaluation of the ecological status of the fjords, but requires a sufficient amount of data for the robust environmental assessment as proposed by the Water Framework Directive (WFD).

Dose-dependent response of a benthic system to biodeposition from suspended blue mussel (Mytilus edulis) culture

This study reports the results of a field experiment using benthic mesocosms that examined dose-dependent effects of mussel biodeposition on the benthic environment. Mesocosms were placed in the natural sea bottom and subjected to one of eight levels of biodeposition (from 0 to 1400musselsm−2). Most analyses indicated non-linear (i.e., threshold) effects. Sediment characteristics changed significantly between 200 and 400musselsm−2 as did multivariate community structure. Community structure effects were characterised by changes in abundances of species that are very sensitive or tolerant to organic loading. The multivariate AZTI Marine Biotic Index (M-AMBI) indicated that the benthic status changed from High to Good in all mesocosms receiving biodeposits. Sediments acted as a sink for oxygen (O2), but results suggest O2 sediment demand was not sensitive enough to evaluate organic loading impacts. Results from this and improved experiments can be used to determine the environmental carrying capacity of sites for bivalve culture.

Characterization of macro-benthic fauna for ecological health status of the Fosu and Benya lagoons in coastal Ghana

This study conducted a comparative analysis of benthic macroinvertebrate communities in the Fosu and Benya lagoons in Ghana, based on the anthropogenic effect on the two lagoons. Salinity, oxygen, temperature, conductivity, turbidity and pH were measured, invertebrate richness and species densities were determined. The AZTI Marine Biotic Index (AMBI) and multivariate statistics were used to determine the different responses of fauna to pollution. The fauna were categorized into five ecological groups based on the degree of tolerance of the different species to pollution: disturbance-sensitive species; disturbance-indifferent species, disturbance-tolerant species, second-order opportunistic species; and first-order opportunistic species. The Fosu Lagoon supported more pollution tolerant species, whereas the Benya Lagoon had more species that were sensitive to organic enrichment under relatively unpolluted conditions. Chironomus sp., which is adapted to virtually anoxic conditions, was the most abundant in the Fosu Lagoon whereas Nemertea sp. was the most abundant in the Benya Lagoon. The numerical and relative abundance (%) of all 7 taxa in the Fosu Lagoon was 1,359 and 92.35%, respectively. The numerical and relative abundance (%) of all 34 taxa in the Benya Lagoon was 2,459 and 87.52%, respectively. Expectedly, the level of dissolved oxygen in the less saline Fosu Lagoon was higher than that in the more saline Benya Lagoon. The reduced photoperiod and photosynthetic activities of aquatic plants might account for this trend. There is a need to implement comprehensive monitoring and management initiatives for sustaining the ecological health of coastal lagoons in Ghana in order to support the many people that depend upon these ecosystems for their livelihood.

Combined effects of inorganic nutrients and organic enrichment on intertidal benthic macrofauna: an experimental approach

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 461:59-70 (2012) - DOI: https://doi.org/10.3354/meps09819 Combined effects of inorganic nutrients and organic enrichment on intertidal benthic macrofauna: an experimental approach Jayne E. Fitch*, Tasman P. Crowe School of Biology and Environmental Science, Science Centre West, University College Dublin, Belfield, Dublin 4, Ireland *Email: jaynefitch@hotmail.com ABSTRACT: Marine environments are affected by multiple anthropogenic stressors, but research to date has focussed primarily on the impacts and indicators of individual stressors. Nutrient and organic enrichment can occur separately or in combination with each other, but their combined effects are not fully understood. In a field experiment on a sheltered, sandy-mud, sedimentary intertidal shore, 3 levels of inorganic nutrient addition (nutrient sticks) were crossed with 2 levels of organic matter enrichment (rusks), and benthic macrofauna were sampled at 2 times. Organic matter caused greater impacts on benthic macrofauna than nutrients and had a significant effect on taxon richness and Shannon diversity. Total abundance responded to the interactive effects of nutrients and organic matter. The response observed in total abundance was largely driven by the small opportunistic polychaete Capitella sp., which responded primarily to organic matter, but its response was mediated by addition of nutrients to the system. This highlights that its abundance varies in response to interactions among stressors, so cannot be easily interpreted. The performance of 2 biotic indices, the AZTI Marine Biotic Index (AMBI) and Multivariate AMBI (M-AMBI), varied, but M-AMBI proved to be the most effective at detecting the combined effects of nutrients and organic enrichment. These findings show that effective management of coastal environments must take account of the potentially complex combined effects of multiple stressors. KEY WORDS: Multiple stressors · Inorganic nutrients · Organic matter · Benthic · Intertidal · Macrofauna Full text in pdf format PreviousNextCite this article as: Fitch JE, Crowe TP (2012) Combined effects of inorganic nutrients and organic enrichment on intertidal benthic macrofauna: an experimental approach. Mar Ecol Prog Ser 461:59-70. https://doi.org/10.3354/meps09819 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 461. Online publication date: August 08, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Performance of Two Southern California Benthic Community Condition Indices Using Species Abundance and Presence-Only Data: Relevance to DNA Barcoding

DNA barcoding, as it is currently employed, enhances use of marine benthic macrofauna as environmental condition indicators by improving the speed and accuracy of the underlying taxonomic identifications. The next generation of barcoding applications, processing bulk environmental samples, will likely only provide presence information. However, macrofauna indices presently used to interpret these data are based on species abundances. To assess the importance of this difference, we evaluated the performance of the Southern California Benthic Response Index (BRI) and the AZTI Marine Biotic Index (AMBI) when species abundance data were removed from their calculation. Presence only versions of these two indices were created by eliminating abundance weighting while preserving species identity. Associations between the presence and abundance BRI, and the presence and abundance AMBI were highly significant, with correlation coefficients of 0.99 and 0.81, respectively. The presence versions validated almost equally to the abundance-based indices when applied to the spatial and the temporal monitoring data used to validate the original indices. Simulations in which taxa were systematically removed from calculation of the indices were also conducted to assess how large the barcode library must be for the indices to be effective. Correlation between the BRI-P and BRI remained above 0.9 with only 370 species in the library and reducing the number of species to 450 had almost no effect on correlation between the presence and abundance versions of the AMBI.

Benthic invertebrate community in Khur-e-Mussa creeks in northwest of Persian Gulf and the application of the AMBI (AZTI's Marine Biotic Index)

Benthic invertebrates are a well-established target in environmental quality status evaluations. The AMBI (AZTI's Marine Biotic Index) was developed to determine the impacts and the quality status of soft-bottom marine benthic communities. The aim of this study was investigating multivariate pattern of benthic invertebrate community and application of AMBI (AZTI's Marine Biotic Index) for determining quality of health status in Khuzestan coastal waters. Seasonal samplings were collected from eight creeks over one year study by Peterson grab sampler, beginning from October 2005. All creeks are characterized by muddy bottom. According to sensitivity to environmental stress, macrobenthic animals classified into 5 ecological groups. Among 28 identified faunal groups the most abundant groups were polychaets, molluscs, crustaceans and nematodes, respectively. Two way ANOVAs showed only seasonal significant differences in mean abundance (P<0.05) and Margalef richness index values (P<0.05), while all of studied creeks shows similar biological characters based on benthic communities. According to annual mean of AMBI value all creeks were in ecological group III with slightly polluted condition, except for Darvish that was in unpolluted category. In the present study, although the number of species initially increased, but due to appearance of dominant species such as Capitella sp. and nematods (as opportunist species), diversity values reduced. In general, according to AMBI and Biotic index values, the most creeks are classified into unpolluted and slightly polluted categories except for Zangy, Doragh and Patil in summer and also Zangy and Bihad in winter which was in moderate to heavily polluted category. Different types of exploitation, industrial and shipping activities in this area could result in unbalanced to polluted status in benthic animals (as the best indicators in sediment quality assessment) so these results can be acceptable.

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.

Meta-analysis of a large data set with Water Framework Directive indicators and calibration of a Benthic Quality Index at the family level

A large data set of marine benthic samples from the Eastern Mediterranean was used to develop Benthic Quality Index (BQI)-family, a new indicator based on the BQI index, which was calibrated by maximizing the consensus with other existing indicators namely BQI, Shannon diversity H’, AZTI Marine Biotic Index (AMBI) and BENTIX. The values calculated for the BQI-family indicator are significantly and highly correlated (p<0.0001) to those calculated for all the aforementioned indicators and it provides judgment on ecological status close to their average. Furthermore, it combines the strong points of all these methods with the increased reliability, speed and low cost of the identification at higher taxonomic levels.

Analysis of Benthic Invertebrate Communities as a Function of Distance from Two Fish-Processing Plant Effluent Discharges in New Brunswick, Canada

Benthic invertebrate communities have been known to change due to impacts from nutrient-rich industrial outputs, such as those from pulp and paper, sewage-treatment plants, or aquaculture. Fish-processing plants have been recognized as contributors of large volumes of nutrient rich effluent to marine and estuarine environments, but their effect on benthic invertebrate communities is unknown. Benthic invertebrates and sediment samples were obtained from marine sampling stations at 0-, 10-, 30-, and 100-m distances from two fish-processing outfalls in Atlantic Canada. Sediment grain size, total organic carbon (TOC), ammonia, sulphide, and redox, as well as invertebrate abundance, density, taxa richness, Simpson's Inverse Diversity Index, Bray-Curtis Index of (%) Similarity, and the AZTI marine biotic index (AMBI), were determined for all sampling sites. Results from this study illustrate that taxa richness and density significantly increased as distance from the outfall discharge increased. In our study, TOC was only significantly correlated to AMBI but not to the other benthic invertebrate assemblage descriptors calculated in this study (invertebrate density, taxa richness, Simpson's Inverse Diversity Index). The study results suggest that taxa richness and density may be affected by effluent from fish-processing plants.

The importance of habitat-type for defining the reference conditions and the ecological quality status based on benthic invertebrates: The Ria Formosa coastal lagoon (Southern Portugal) case study

Coastal lagoons are complex systems, with considerable habitat heterogeneity and often subject to high temporal dynamics, which constitutes a great challenge for ecological assessment programs. For defining reference conditions for benthic invertebrates, under the EU Water Framework Directive objectives, historical data from the Ria Formosa leaky lagoon (wet surface area of about 105km2) located in Southern Portugal was used. The influence of habitat features, such as channel depth, sediment type and seagrass cover, on the expression of these biological communities, was inferred by analyzing subtidal data collected at stations with different environmental characteristics. Such heterogeneity effect was analyzed at the community compositional and structural levels, and also for three indices in the multimetric Benthic Assessment Tool (BAT). This tool for the assessment of ecological status includes the Margalef index, Shannon–Wiener diversity index, and AZTI's Marine Biotic Index (AMBI). Significant variations associated with environmental features were reflected on specific reference conditions at four habitats in the lagoon. After habitat calibration, the Benthic Assessment Tool (BAT) revealed that, in general and for the period of time covered by this historical data set, the status of the lagoon corresponded to a good ecological condition, which is mainly due to its high water renewal rate. Such classification is in accordance with the majority of studies at the lagoon. However, at punctual sites with human induced high water residence times, significantly lower BAT values were registered. Such community degradation can be associated with physical stress due to salinity increase and to a degradation of water quality, with occurrence of occasional dystrophic crisis, triggered by low water renewal. Habitat differentiation was a crucial step for a correct evaluation of the ecological condition of invertebrate communities across the lagoonal system.

Feeding diversity index as complementary information in the assessment of ecological quality status

The feeding diversity of macroinvertebrates from the estuary of Mondego was estimated with Shannon–Wiener complementary evenness following the methodology presented in Gamito and Furtado (2009. Ecological Indicators. 9, 1009–1019). Results were compared with those from BAT (Benthic Assessment Tool; Teixeira et al., 2009. Marine Pollution Bulletin. 58, 1477–1786) applied to the same data set, obtained from sampling carried out in 14 estuarine subtidal stations in Spring of 1990, 1992, 1998, 2000 and 2002. The BAT is a multimetric methodology based on three indices, the Shannon–Wiener and Margalef diversity indices, applied in conjunction with AMBI (AZTI Marine Biotic Index). To determinate the feeding diversity, each invertebrate was assigned to a feeding group. Six trophic groups were considered: surface deposit feeders, subsurface deposit feeders, herbivores or grazers, suspension feeders and suspension/deposit feeders. The carnivorous, omnivorous and scavengers were all grouped together, forming the sixth group.The results obtained with both tools pointed out, in general, to the same tendencies. However, in few occasions the feeding diversity pointed out to a high or a bad ecological quality condition whereas the BAT indicated a moderate condition. Occasionally, in stations with average species richness, all individuals were assigned to only one to three feeding groups, and the feeding diversity was low. Even if these taxa were included in the first two or three AMBI sensitive groups, with their presence indicating a possible good ecological condition, they all perform the same ecological function, for example, they are all omnivorous. In these cases the trophic functioning of the system is reduced and the lower trophic levels are missing, such as the suspension-feeders and the decomposers or deposit-feeders. On the contrary, a highly diverse trophic assemblage might be found, but composed of taxa assigned to AMBI ecological groups of species indifferent or tolerant to organic enrichment, and of second-order opportunistic species, indicating a moderate ecological condition, while the feeding diversity will be high. The feeding diversity is, therefore, useful as a complementary information index, measuring other aspects of the community organization, which are not required for ecological quality assessment by the WFD, and so not included in metrics such as BAT.

Assessment of estuarine macrobenthic assemblages and ecological quality status at a dredging site in a southern Europe estuary

The Water Framework Directive (WFD) strengthened the need for the protection and enhancement of Ecological Quality Status (EQS) in water bodies of EU Member States. However, in terms of the EQS assessment, there is a lack of detailed studies that assess the consequences of dredging, especially concerning macrobenthic communities. Therefore, the main objective of this study was to evaluate the EQS assessment, as important need to WFD, based on diversity and ecological quality indices after dredging activity.Data was collected in Mondego estuary, Portugal, between October 2007 and November 2008, within and around the area to be dredged (3 ha): one dredging occasion and ten sampling dates along one year. Physical–chemical changes were examined. The relative performance of Margalef, Shannon–Wienner, AMBI–AZTI Marine Biotic Index and the multimetric BAT –Benthic Assessment Tool (BAT) were analyzed before and after dredging.In the first days, dredging increased the share of fine and coarse sand sediment and had changed TSS, POM and SOM, affecting the macrofauna assemblages. Two months after the dredging, the number of taxa, density, diversity and ecological indices showed similar values to pre-dredging conditions and one year later the number of species and density values almost duplicated. However, the macrofauna composition and structure were still significantly different in relation to pre-dredging and the biomass values did not return to the original values. Nevertheless, BAT was sensitive to the changes that occurred in the area, showing that the system recovered to pre-dredging values after one year, in terms of EQS. The present work reinforced the robustness of BAT as an accurate ecological quality assessment tool.

Calibration and validation of the AZTI's Marine Biotic Index (AMBI) for Southern California marine bays

Benthic indices are useful indicators of sediment condition, but many indices are difficult to employ because they require large calibration datasets. The AZTI's Marine Biotic Index (AMBI) requires minimal local calibration, but it was developed in Europe and the validity of its extension to distant regions is unclear. Here we compare its performance in Southern California's marine bays with that of the Benthic Response Index (BRI), a locally derived data-intensive index. AMBI was calibrated in four ways: (1) using the original AMBI species’ classifications developed in Europe; (2) augmenting the original classifications with closely related taxa, following AMBI guidelines; (3) using local expertise to independently classify taxa; and (4) revision of the local expert classifications by European developers of the index. These approaches were applied to a 685 sample data set and assessed relative to the BRI by comparing samples’ classification from best to worst and by evaluating the level of agreement in assigning samples into four condition categories. The AMBI was validated against environmental proxies of disturbance and expert judgement, using consensus agreement about sample condition developed by nine benthic ecologists. The first AMBI approach did not work well, as only 24% of the 928 taxa were on the original AMBI species list, resulting in only 11% of the samples meeting the required 20% of classified individuals for AMBI application. The other approaches classified substantially more taxa, allowing application to 75–98% of the samples. Both of these approaches were significantly correlated with the BRI, though the correlations were lower than between the AMBI runs. None of the AMBI approaches, though, compared well with either the BRI or the validation data when placing samples into perturbation categories, with the AMBI having a greater central tendency. AMBI categorized less than 5% of the samples as reference compared to almost one-third of the samples by the experts or BRI, and substantially underestimating the number of severely affected samples. Species most responsible for disagreements between BRI and AMBI approaches were identified. Four modifications to enhance AMBI performance were identified: (1) incorporate local expertise in assigning ecological classifications, (2) use transformed abundance weighting to reduce the effect of dominant species, (3) calibrate the categorization scaling using expert judgement, and (4) use the AMBI in combination with other measures, such as the M-AMBI. The success of these modifications is specific to this study, but they are likely to enhance AMBI's performance worldwide.

The importance of setting targets and reference conditions in assessing marine ecosystem quality

Assessing benthic quality status of marine and transitional water habitats requires to set up both: (i) tools (i.e. indices) to assess the relative quality of the considered habitat, and (ii) reference conditions for which such indices can be computed and used to infer the absolute ecological status (ES) of the considered habitat. The development of indices, their comparison and the assessment of the causes of their discrepancies have been largely discussed but less attention has been paid to the methods used for the setting of adequate reference conditions, although this step is clearly crucial for the sound assessment of ES. This contribution reviews the approaches available in setting both reference conditions (pristine areas, hindcasting, modelling and best professional judgment) and targets (baseline set in the past, current baseline and directional/trends). We scored the use of pristine or minimally impacted conditions as the best single method; however, the other methods were judged as adequate then combined with best professional judgment. The case of multivariate AMBI (AZTI's Marine Biotic Index) is used to highlight the importance of setting correct reference conditions. Hence, data from 29 references, including 14 countries from Europe and North America, and both coastal (15 cases) and transitional (17 cases) waters, have been used to study the response of multivariate AMBI to human pressures. Results show that the inability of this index to detect human pressure is in most cases linked with the use of inappropriate methods for setting reference conditions.

Assessing proposed modifications to the AZTI marine biotic index (AMBI), using biomass and production

Initially described in 2000, AZTI's Marine Biotic Index (AMBI) aims to assess alterations in communities of soft-bottom marine benthic macroinvertebrates caused by anthropogenic impacts. Although it was designed to be used in European estuaries and coasts this index, based on Pearson and Rosenberg's model of responses to organic enrichment, is being used successfully worldwide. Taking into account statistical difficulties associated with the use of raw abundance data, modifications to the index were recently proposed. These included transforming abundances prior to its calculation, or to use data other than abundances which might be more functionally relevant (such as biomass or production data). Using data from the Basque coast and estuaries (northern Spain), collected between 1995 and 2009, where the evolution of human pressures and restoration actions in the area may be taken into account, the performance of AMBI is compared to that of the proposed modifications in order to assess their usefulness. Despite large variations in the form and nature of the input data, all variations of AMBI index are shown to be highly correlated, even when presence/absence data are used. New boundaries between disturbance categories were calculated, reflecting inter-relationships between different forms of the index. The disturbance classification obtained from all variations using the recalculated boundaries agreed closely with that derived from AMBI. The finding that AMBI values calculated with presence/absence data are potentially useful opens up many possibilities, such as determining the status of assemblages retrospectively using historical data.

Evaluating the influence of off-shore cage aquaculture on the benthic ecosystem in Alghero Bay (Sardinia, Italy) using AMBI and M-AMBI

The impact of an off-shore fish farm in Alghero Bay (northwest Sardinia, Italy) on the benthic ecosystem was investigated in 2007 and 2008. In addition to studying the chemical and physical characteristics of the area (i.e., currents and sediment analyses), some biological analyses were also performed. The AZTI's Marine Biotic Index (AMBI) and the multivariate AMBI (M-AMBI) were calculated, which are being used in assessing the ecological status of benthic communities within the European Water Framework Directive (WFD). Clear impact gradients were detected according to both methods; they are related to farm production, prevailing currents, and characteristics of the area (i.e., water depth and distance to the cages). The site affected most was detected within 84 m from the cages; the area that no longer showed effects was over 907 m from the cages. The gradient is shown by decreasing AMBI values and percentage of opportunistic species and increasing richness, diversity, and the presence of sensitive species. This study highlights the importance of setting reference conditions for different areas when calculating M-AMBI. These reference conditions correspond to those in undisturbed sites in the opposite direction of the prevailing currents within the area.

Assessing benthic health in stressed subtropical estuaries, eastern Florida, USA using AMBI and M-AMBI

Abstract The Indian River Lagoon (IRL) and the St. Lucie Estuary (SLE), both located in Florida, USA, are affected by a variety of anthropogenic pressures. Benthic macroinvertebrates have been monitored quarterly since February 2005, at 15 stations, in order to assess benthic health. Since the SLE and IRL are situated in a subtropical area, it is affected by two major climatic seasons, dry (winter) and wet (summer). This contribution investigates the application of the AZTI's Marine Biotic Index (AMBI) and multivariate-AMBI (M-AMBI), to assess the ecological status of these estuaries. AMBI was firstly calculated after assigning most of the previously unassigned species to each of the five ecological groups (from sensitive to first order opportunistic species). Three main benthic assemblages, associated to oligohaline, meso-polyhaline and euhaline stretches, have been identified within the area. Reference conditions of richness, Shannon's diversity and AMBI have been derived for these assemblages; M-AMBI has then been calculated. Both methods show that the inner part of the SLE is affected by anthropogenic pressures (increased freshwater inflow, with elevated nutrient input, and sedimentation), whilst the IRL is less affected. We have demonstrated that AMBI and M-AMBI are insensitive to the dramatic seasonal changes occurring in the SLE/IRL. At some of the stations a significant positive trend in benthic quality has been identified, linked to the polluted freshwater discharges decrease. The use of both tools seems adequate in assessing benthic health in this subtropical area.