Relocation of dredged material in estuaries under the aspect of the Water Framework Directive—A comparison of benthic quality indicators at dumping areas in the Elbe estuary

In the context of the requirements of the European Water Framework Directive (WFD) numerous benthic indices have been proposed recently to assess the ecological quality of marine and transitional waters. In several studies these metrics were applied to coastal and estuarine environments under diverse anthropogenic pressures. Although currently the dumping of dredged material is one of the most prominent human impacts that modify estuaries, the performance of benthic indices to detect effects of dredged sediment relocation has not yet been tested explicitly. Hence we examined a selection of common metrics (species richness, Shannon diversity, AMBI, M-AMBI, W-value, BO2A) at 11 dumping and 11 nearby reference areas in the highly modified Elbe estuary (Germany), where permanent dredging is necessary to maintain the depth of the navigation channel. In order to cover the entire estuary, the study area spanned over the whole salinity gradient from limnic to euhaline. Additionally, we investigated changes in benthic communities due to dredged material placement. All indices, except the W-value, were suitable to differentiate between dumping and reference areas and showed significantly better index values exclusively at reference areas. The applicability of AMBI and M-AMBI was restricted in the limnic stretch due to the more frequent occurrence of freshwater species there. The W-value and BO2A were non-satisfactory in the case of azoic sediment, and in most cases these two indices indicated much better ecological status classifications than the other indices tested. Furthermore, the BO2A had restricted applicability with increasing salinity. At eight of eleven sites the benthic communities differed significantly between dumping and reference areas. Our findings show that the power of conventional benthic indices to detect physical disturbances like the dumping of dredged sediment varies greatly. Having this in mind, we suggest to choose carefully the benthic indices for ecological quality assessments according to the WFD in estuaries in order to avoid misclassifications. Such errors may lead to unnecessarily expensive remediation activities or, in the opposite case, to inactivity although actions were necessary. Furthermore, in order to better meet the WFD requirements we suggest that, regarding frequency and volume, dumping should be adapted as far as possible to the natural processes of sediment movement.     

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.     

Is there a significant relationship between the benthic status of an area,determined by two broadly-used indices,and best professional judgment?

Two benthic indices to assess the quality status (the AZTI's Marine Biotic Index (AMBI) and multivariate-AMBI (M-AMBI)) are being used extensively in different habitats worldwide. We try to interpret what is behind these indices making them suitable for different habitats. To demonstrate that, we used best professional judgment (BPJ), applying it to a dataset from southern Chile, to determine the criteria proposed by 12 experts in assessing the status. The experts were provided with raw species abundance data, from 12 stations within a gradient of disturbance, from unaffected to severely affected. There was a very good agreement among experts (kappa values 0.72–0.77), with highly significant (p < 0.001) correlation between BPJ and AMBI and M-AMBI classifications, and an agreement of 76.4% and 81.9%, respectively. When comparing BPJ in Chile with other results in Europe, USA and northern Africa, similar patterns can be identified: (i) the number of criteria identified for classification is very high (range 7–12); (ii) the experts use several criteria together in the BPJ assessment; and (iii) the rank of the most important criteria is indicator species, richness, and diversity/dominance. These criteria are included in indices such as AMBI and M-AMBI. Hence, although experts are classifying samples subjectively when applying BPJ, they are corroborated in their opinions when using such indices. This fact can explain why these indices are so widely used.     

Assessing estuarine benthic quality conditions in Chesapeake Bay: A comparison of three indices

Legislation in US and Europe has been adopted to determine the ecological integrity of estuarine and coastal waters, including, as one of the most relevant elements, the benthic macroinvertebrate communities. It has been recommended that greater emphasis should be placed on evaluating the suitability of existing indices prior to developing new ones. This study compares two widely used measures of ecological integrity, the Benthic Index of Biotic Integrity (B-IBI) developed in USA and the European AZTI's Marine Biotic Index (AMBI) and its multivariate extension, the M-AMBI. Specific objectives were to identify the frequency, magnitude, and nature of differences in assessment of Chesapeake Bay sites as ‘degraded’ or ‘undegraded’ by the indices. A dataset of 275 subtidal samples taken in 2003 from Chesapeake Bay were used in this comparison. Linear regression of B-IBI and AMBI, accounted for 24% of the variability; however, when evaluated by salinity regimes, the explained variability increased in polyhaline (38%), high mesohaline (38%), and low mesohaline (35%) habitats, remained similar in the tidal freshwater (25%), and decreased in oligohaline areas (17%). Using the M-AMBI, the explained variability increased to 43% for linear regression, and 54% for logarithmic regression. By salinity regime, the highest explained variability was found in high mesohaline and low polyhaline areas (53–63%), while the lowest explained variability was in the oligohaline and tidal freshwater areas (6–17%). The total disagreement between methods, in terms of degraded-undegraded classifications, was 28%, with high spatial levels of agreement. Our study suggests that different methodologies in assessing benthic quality can provide similar results even though these methods have been developed within different geographical areas.     

Assessing the suitability of five benthic indices for environmental health assessment in a large subtropical South American estuary

Despite the increased and widespread usage of benthic indices for environmental health assessment, some methodological ambiguities remain to be solved. We tested the congruence and consistency of the benthic indices ITI, BO2A, BENTIX, AMBI and M-AMBI in a subtropical estuary (Paranaguá Bay, Brazil). Indices were applied to non-vegetated tidal flats increasingly contaminated by sewage to test: (i) correlations with molecular biomarkers of sewage (consistency); and (ii) evaluate the overall agreement/similarity of responses (congruence). The responses of the benthic indexes ITI, AMBI and BO2A were congruent among themselves and consistent with molecular biomarkers values. BENTIX and M-AMBI were less consistent and congruent and possibly need a readjustment of boundaries for subtropical habitats. The indices seemed robust to natural background yearly variations not related to contamination. Faecal sterols associated to nutrient contents suitably supported the validation of indices and could integrate reference conditions for sewage impacted coastal habitats. Benthic indices can successfully integrate management guidelines, but their suitable application demands further research on tolerance shifts of key indicator species.     

Benthic quality assessment in a naturally- and human-stressed tropical estuary

Cochin estuary, one of the largest tropical estuaries of India, supports high levels of human pressure throughout the year and natural stress during monsoon season. Six stations were monitored between 2002 and 2004 covering the pre-monsoon, monsoon, and post-monsoon seasons. Ecological status of macrobenthos was assessed using the AZTI's Marine Biotic Index (AMBI) and the multivariate-AMBI (M-AMBI). The overall ‘moderate’ disturbance classification (according to AMBI) and ‘moderate-poor’ ecological status (according to M-AMBI) indicate that the macrobenthos in the estuary experiences stress. There was a gradient of increasing quality from the most degraded northern site to the main estuary, downstream. Monsoon caused further reductions in quality of macrobenthos in the main estuary, while the degraded northern station showed improvement in 2003, when the monsoon was strong. The assessment of the Cochin Estuary using AMBI and M-AMBI indicates where this water body stands in comparison to European and other water bodies, which may be useful for developing required protective measures in tropical systems and to design monitoring strategies.     

M-AMBI revisited: looking inside a widely-used benthic index

M-AMBI is a multimetric index for assessing the ecological quality status of marine and transitional waters. It is based on benthic macroinvertebrates and integrates AMBI, a biotic index based on species sensitivity/tolerance, with diversity and richness, making it compliant with the European Water Framework Directive. The success of AMBI paved the way for the introduction of M-AMBI, which was subsequently incorporated into the regulations of several European countries. The M-AMBI algorithm integrates the metrics by means of factor analysis (FA). In this paper, we first reproduced the algorithm using the open source R software. This enabled us to point out that FA is not functional to M-AMBI, and its omission does not appreciably change the results. We then enhanced the applicability of the index, making it independent of the number of samples. In this way, M-AMBI is closely approximated by the simple mean of the normalised metrics with no need for multivariate techniques. Finally, we further simplified the approach, presenting a bivariate version that is still highly correlated with M-AMBI, in which the constitutive metrics are reduced to a diversity measure and a species sensitivity index. The properties of this bivariate version include simplicity, transparency, robustness, and openness.     

不同底栖生物指数在福建省近岸海域的适用性

将3个底栖生物指数AZTI海洋生物指数(AMBI)、多毛类机会种和端足目动物指数(BOPA)、底栖动物多毛类和端足目指数(BPA)和Shannon多样性指数(H)应用于福建省近岸海域4个典型海湾和1个河口的生态质量评价,评估这4个指数在研究区的适用性.结果表明: 4个指数的评价结果差异较大,评价等级完全相同的站位仅有4个,占总评价站数的8.7%;AMBI将76.1%的站位评价为等级“良”,BOPA将89.1%的站位评价为等级“优”,BPA和H的评价结果等级梯度变化明显;对于海湾,BOPA、BPA和AMBI与营养盐因子活性磷酸盐(DIP)和无机氮(DIN)无显著相关性,不能响应研究区的富营养化压力;而H与DIN呈显著负相关.对于河口,BOPA、BPA和AMBI与DIP和DIN均呈显著正相关,且随着与入海口距离的减小,7个断面生态质量评价等级没有明显变化,不能识别河口高强度的富营养化压力,评价结果偏高;而H与DIN呈显著负相关,且随着与入海口距离的减小,7个断面生态质量评价等级呈现提高的趋势.总体上,BOPA、BPA和AMBI在福建近岸海域的适用性较低,而H更合适该研究区,能够响应研究区主要的环境压力.     

莱州湾小清河口近岸海域底栖生境健康评价

于2019年7月、8月和9月对莱州湾小清河口近岸海域的大型底栖动物进行调查,对该海域大型底栖动物群落的种类组成和群落结构等进行研究,利用丰度/生物量比较曲线法、AMBI指数法和M-AMBI指数法对研究海域大型底栖动物群落健康和底栖生境健康状况进行评价。研究结果表明,2019年7月、8月和9月共采集到大型底栖动物64种,其中多毛类24种,甲壳类19种,软体动物17种,其他类群4种。该海域的优势种为光滑河蓝蛤（Potamocorbula laevis）、彩虹明樱蛤（Moerella iridescens）、半褶织纹螺（Nassarius semiplicatus）、四角蛤蜊（Mactra veneriformis）,寡鳃齿吻沙蚕（Nephthys oligobranchia）、中蚓虫（Mediomastus californiensis）、东方长眼虾（Ogyrides orientalis）、尖齿拳蟹（Philyra acutidens）和短角双眼钩虾（Ampelisca brevicornis）,其中彩虹明樱蛤和寡鳃齿吻沙蚕在三次调查中均为优势物种,优势度明显。群落结构聚类分析和多维尺度分析表明,7月研究海域的大型底栖动物群落以10%的相似性可以分为3组,8月以18%相似性可以分为4组,9月以19%的相似性可以分为3组,三次调查的群落结构相似度均较低。丰度/生物量比较曲线法研究结果显示,底栖动物群落生物量优势显著,群落处于未干扰状态。AMBI指数及M-AMBI指数分析结果表明,莱州湾小清河口近岸海域底栖生境处于未干扰或者轻度干扰的状态,健康状况处于高等或者优良的状态。     

M-AMBI derived from taxonomic levels higher than species allows Ecological Status assessments of benthic habitats in new geographical areas

Under the Water Framework Directive (WFD) benthic Ecological Quality Ratios (EQRs) are important tools for assessing Ecological Status (ES) of coastal and transitional waters. Calculation of the Multivariate-AZTI Marine Biotic Index (M-AMBI) EQR is based on the proportions of sensitive and stress tolerant benthic invertebrate species, number of species and Shannon–Wiener diversity. The sensitivity of many tropical/sub-tropical taxa has not yet been determined, presenting a barrier to the direct transfer of WFD EQRs, and the ideas underpinning them, to the management of coastal waters beyond Europe. To overcome this we examine using higher taxonomic level data with M-AMBI.Before applying such approaches to assessing ES in new geographical regions it is essential to determine the effects of using higher taxonomic level data on M-AMBI in areas where the tool was developed. To this end, we use macrofaunal data from three well studied sites in north-western Europe to examine the effects of using taxonomic level data higher than species on M-AMBI. Using the European datasets M-AMBI ES classification was shown to be robust to changes in taxonomic level data. We test the suitability of family-level M-AMBI for assessing ES in subtropical Hong Kong waters. Family level M-AMBI was useful in detecting stress in Hong Kong, where it successfully detected temporal and spatial shifts in ES in response to seasonal hypoxia and salinity variability, and anthropogenic organic enrichment.     

Development of a multimetric approach to assess perturbation of benthic macrofauna in Zostera noltii beds

Biotic indices based on soft-bottom macrozoobenthic communities are currently used throughout Europe to assess the ecological quality of coastal and transitional water bodies according to the European Water Framework Directive. However, the performance of the currently available biotic indices still has to be tested against a variety of different impact sources. In particular, physical perturbations have received much less attention than other kind of disturbances. This study consisted in testing the capacity of currently available uni- (BOPA, AMBI and BENTIX) and multivariate (M-AMBI) Biotic Indices to assess the ecological impact of the destruction of a Zostera noltii seagrass bed in Arcachon Bay (France) following sediment deposits. Changes of habitat after this physical perturbation were hardly assessed by any of these Biotic Indices whereas analysis of the benthic community showed drastic changes of structure following the perturbation and no recovery after 15 months. This study demonstrates that these Biotic Indices must be integrated into a multimetric approach which describes better the biological integrity of the benthic community by including a complementary set of metrics. A new multimetric approach, named MISS (Macrobenthic Index of Sheltered Systems) is proposed. MISS correctly highlighted the destruction of the seagrass beds, by using 16 metrics describing the biological integrity of the macrofauna.     

Sediment quality of the Neuse River estuary, North Carolina: an integrated assessment of sediment contamination, toxicity, and condition of benthic fauna

A study of ecological conditions associatedwith bottom sediments in the Neuse Riverestuary, U.S.A. was undertaken during summer1998. Sampling of macroinfauna, sedimentsfor toxicity and chemical contaminant analyses,and physical properties of water was carriedout synoptically over a four-day period at 20stations from the mouth of the Neuse River atPamlico Sound to approximately 90 km upstream. The distribution and condition of benthicinfauna were found to vary in response tonatural and anthropogenic factors, and apparentassociations between degraded infaunalcondition and sediment contamination and/ortoxicity were observed over roughly half of thesampled area (7 stations, 47% area). With fewexceptions, degraded benthic conditions wereassociated with significant sedimentcontamination or toxicity. High sedimentcontaminant levels were found to occur almostexclusively in fine-grained, organic-rich muds. These results suggest that high organic loadingand chemical contaminant inputs to the NeuseRiver, coupled with low freshwater dischargerates and high residence times in the lowerestuary, have contributed to degraded benthicconditions at these sites.     

A comparative approach of assessing ecological status in two coastal areas of Eastern Mediterranean

This work presents an assessment of the ecological quality status of two marine coastal areas in the Aegean Sea (Greece, Eastern Mediterranean) based on the benthic macroinvertebrate quality element. S. Evvoikos and Thessaloniki gulfs, two coastal areas subjected to slight and heavier anthropogenic pressures, were selected to test the biotic index Bentix developed for the assessment of the ecological status. Other ecological indicators, such as the Shannon diversity index (H′), the species richness (S) and the AMBI biotic index were also applied and evaluated comparatively. Faunistic data were also used to interpret results. The resulting classification was validated with the use of physicochemical parameters and pressure information. This work also provides an insight into the structure of the Bentix classification scheme within the scope of its use in Water Framework Directive (WFD) implementation.     

Development of a benthic macroinvertebrate multimetric index (MMI) for Neotropical Savanna headwater streams

Assessing the ecological impacts of anthropogenic pressures is a key task in environmental management. Multimetric indices (MMIs), based on aquatic assemblage responses to anthropogenic pressures, have been used increasingly throughout the world. The MMI approach is a low-cost, rapid field method that produces an aquatic condition index that responds precisely to anthropogenic pressures, making it useful for conservation and environmental management. We developed four candidate MMIs based on benthic macroinvertebrate assemblages sampled at 40 randomly selected sites to assess the environmental condition of streams upstream of a hydroelectric power plant in the Brazilian Neotropical Savanna biome. Those MMIs were built from landscape-adjusted and unadjusted biological metrics as well as two alternative ways of choosing metrics. The alternative MMIs performances were tested by comparing their precision to distinguish least-disturbed areas, responsiveness to discriminate least- and most-disturbed areas, and sensitivity to anthropogenic pressures at catchment and local scales. The best performing MMI had landscape-adjusted metrics and was produced through use of principal component analysis for metric selection. It included 4 metrics: Ephemeroptera richness, average tolerance score per taxon, percentage of predator individuals, and percentage of Odonata individuals adjusted by elevation. This index discriminated well the anthropogenic pressures at local- and catchment-scales, and at both scales simultaneously, as indicated by an integrated disturbance index. Our methodological development included statistical criteria for identifying least- and most-disturbed sites, calibrating for natural landscape variability, and use of non-redundant metrics. Therefore, we expect it will provide a model for environmental assessment of water resources elsewhere in Brazil and in other nations.     

云南程海湖泊系统响应富营养化与水文调控的长期模式

流域开发和气候变化背景下,逐渐增强的人类活动已经显著影响湖泊系统演替及功能。本研究以云南程海为研究对象,通过对程海湖泊沉积物记录与现代调查数据相结合,重建了程海近250年来的生态环境变化过程,探讨了程海湖泊系统在富营养化以及水文波动等多重环境压力影响下的长期响应模式。结果表明: 1970年之前程海营养水平整体偏低,1970—2000年间缓慢增长,2000年后快速增加,初级生产力呈长期上升趋势。1993—2000年期间,引水工程显著增加了湖泊水动力强度和物种扩散能力,促进了直链藻和菱形藻的增加。程海沉积物记录的碳循环变化主要受内源输入的长期影响。富营养化是硅藻群落长期演替的主要驱动因子,其次是湖泊水动力条件的波动。对程海的生态修复与流域管理不仅需要关注水体营养盐的富集与流域污染物的控制,同时还要考虑到湖泊水文调控和水位波动的影响。     

Trends in water quality and subtidal benthic communities in a temperate estuary: Is the response to restoration efforts hidden by climate variability and the Estuarine Quality Paradox?

The analysis of temporal patterns in water quality and benthic assemblages in estuaries constitutes an important methodological issue for discriminating the effects of natural and anthropogenic pressures. Temporal trends in water quality and in the subtidal benthic community over a 5-year interval in the Mondego estuary (Portugal) were investigated with the aim of assessing changes in environmental quality as a response to restoration efforts and climate variability. Particularly, we addressed the following questions: (a) Would trends in water quality and benthos behave consistently over the whole study period for the different zones of the monitoring network and indicate improvement or degradation in ecological condition? (b) Could we distinguish the effects of climate variability and restoration efforts in water quality and benthos from trend analysis results? (c) Could the response of the benthic communities and water quality be useful to guide the planning of future management actions in this system?Clear cause–effect relationships regarding the ecological response to restoration efforts and climate variability were indeed challenging to identify and interpret. In fact, the response of water quality and benthic communities to restoration efforts seemed to have been masked by the effects of climatic variability. Furthermore, the present study illustrated clearly the high environmental variability inherent to estuarine systems and the difficulty of clearly distinguishing natural from anthropogenic stressors, in agreement with the “Estuarine Quality Paradox”. Implications for ecological quality assessment and management of the Mondego estuary and other poikilohaline systems are discussed, namely with regard to the “one-out, all-out” principle required by the European Water Framework Directive (WFD).     

The suitability of the marine biotic index (AMBI) to new impact sources along European coasts

In recent years, several benthic biotic indices have been proposed to be used as ecological indicators in estuarine and coastal waters. One such indicator, the AZTI Marine Biotic Index (AMBI), was designed to establish the ecological quality of European coasts. The index examined the response of soft-bottom benthic communities to natural and man-induced disturbances in coastal and estuarine environments. It has been successfully applied to different geographical areas and under different impact sources, with increasing user numbers in European marine waters (Baltic, North Sea, Atlantic and Mediterranean). The AMBI has been used also for the determination of the ecological quality status (EcoQ) within the context of the European Water Framework Directive (WFD).In this contribution, 38 different applications including six new case studies (hypoxia processes, sand extraction, oil platform impacts, engineering works, dredging and fish aquaculture) are presented. The results show the response of the benthic communities to different disturbance sources in a simple way. Those communities act as ecological indicators of the ‘health’ of the system, indicating clearly the gradient associated with the disturbance.     

Optimising a widely-used coastal health index through quantitative ecological group classifications and associated thresholds

Many globally applied biotic indices, including the AMBI benthic index, are based on species’ sensitivity/tolerance to anthropogenic disturbances. The AMBI scoring primarily relies on the correct assignment of both taxon stressor-sensitivities and the disturbance thresholds or bands. Using an extensive, long-term monitoring dataset from New Zealand (NZ) estuaries, we describe how the AMBI has been strengthened through quantitative derivation of taxon-specific sensitivities and condition thresholds for two key estuarine stressors [mud and total organic carbon (TOC)], and the integration of taxon richness. The results support the use of the existing AMBI condition bands but improve the ability to identify cause; 2–30% mud reflected a ‘normal’ to ‘impoverished’ macrofaunal community; 30–95% mud and 1.2–3% TOC ‘unbalanced’ to ‘transitional’; and >3–4% TOC ‘transitional’ to ‘polluted’. The (refined) AMBI was also successfully validated (R² values >0.5 for mud, and >0.4 for TOC) for use in shallow, intertidal dominated estuaries NZ-wide. Most biotic indices lack the ability to differentiate between anthropogenic disturbances, which in turn undermine their effectiveness for applied purposes. By integrating key quantitative information to an existing benthic index, these results enable more robust identification of coastal stressors and facilitate defensible management decisions.     

Benthic indices and ecological quality of shallow Algeria fine sand community

This study applies six macrozoobenthos-based biotic indices in the shallow coastal waters along the Algerian coast (southern Mediterranean Sea) to establish a reference situation for future use. These shallow fine sand communities were sampled in seven bays along the Algerian coast during the 1980s and the beginning of the 1990s. For the first time, some of the benthic indices used nowadays in Europe for the implementation of the WFD and/or in North America for the Clean Water Act were used to analyze the data collected twenty years ago in order to assess the biological quality status of the Algerian shallow fine sand communities and to provide ecological classifications for the fine sand community along the Algerian coast. The faunal composition showed that the fine sand communities belonged to a Well-Calibrated Fine Sand (WCFS) biocenosis characterized by high species richness and high H′ Shannon-Weaver diversity, with moderate abundance levels only. In the bays of Fetzara, Jijel, Bejaia, Bou Ismail and Arzew (though not in bays of Algiers and Oran), H′ is >4.5, which implies highly diversified communities. The results of the six benthic indices (H′, AMBI, M-AMBI, BENTIX, BOPA and ITI) suggest that good and high quality status assessments are prevalent in all seven bays for the benthic shallow sand communities along the Algerian coast. Nevertheless, the effect of pollution was observed at a small number of sites in the Arzew, Oran and Algiers bays. For example, in Algiers Bay, an east-west quality gradient revealed the effect of organic matter input.