Taxonomic level for assessing oil spill effects on soft-bottom sublittoral benthic communities

Infralittoral soft-bottom macrofauna abundance data collected during four-year surveys after the Aegean Sea (Galicia, Spain) and the Amoco Cadiz oil spill (Brittany, France) at a total of seven sites were analysed at three different taxonomic levels (species, genus, and family). The effects of the spills on macrofauna populations were very similar in the two areas. The post-spill time-courses of Shannon-Weaver diversity values were similar regardless of whether species-, genus- or family-level data were used. Non-metric multidimensional scaling identified well-defined groups of samples corresponding to different times post-spill, and again the results obtained were very similar regardless of the taxonomic level considered. In general, the use of genus- or family-level data did not lead to relevant information loss by comparison with species-level data. In view of these findings and those of previous studies of this type, we conclude that family-level data is generally sufficient for monitoring pollution effects in infralittoral soft-bottom environments.     

Changes in macroalgal communities in the vicinity of a Mediterranean sewage outfall after the setting up of a treatment plant

Benthic macroalgal communities of the upper rocky sublittoral were studied in 1995-1996 in the vicinity of the Marseille (Mediterranean, France) sewage outfall, 8 years after the setting up of a wastewater treatment plant and compared to a previous study carried out in 1972-1974. The number of taxa has increased, a clear stational and seasonal gradient of differentiation of the vegetation appeared, and a turf of ephemeral species is taking place of Corallina elongata at sites close to the outfall. These changes may be due to a decrease in pollutant load, the discharge of ferric chlorates used in the treatment process. However, the overall change is much less conspicuous than that described for deeper soft bottom communities, in particular the Cystoseira amantacea community is not still restored. Biological traits of this species (short distance dispersal) and the nature of most pollutants removed from the effluent (solids and organic matter) may explain this phenomenon.     

Effects of the North Head deep-water sewage outfall on nearshore coastal reef macrobenthic assemblages

The macrobenthos on the coastal reefs near the North Head deep-water outfall were sampled nine times over a 3 year period to determine whether patterns in diversity and abundance were affected by the outfall. The assemblages were sampled using an asymmetrical after control/impact design (ACI). Ten replicate quadrats at each of three sites nested within each of three locations were photographed using a jump camera. These photographs were sampled to provide estimates of the number and abundance of major taxa and abundances of individual species. Significant interactions between outfall vs control through time were detected for the total number of species, bryozoans, cnidarians and the abundances of a silt matrix and two species of bryozoans. Smaller scale interactions among sites through time occurred for the abundances of total fauna, sponges and an ascidian species representing some evidence for the effect of the outfall at these smaller spatial scales. This paper summarizes the correlative evidence of effects from the outfall.     

Effects of a crude oil terminal on tropical benthic communities in Brunei

An environmental survey was carried out in May 1981 at the intertidal and subtidal zone of Sungai (River) Bera, where Brunei Shell Petroleum Company discharges wastewater from its operations. Two reference sites, Sungai Lumut and Sungai Tali, situated northeast of Sungai Bera were also studied. In addition to sampling the macrobenthic communities, hydrocarbon, metal levels, and particle size distribution of the sediments were also studied.Populations of intertidal and subtidal macrobenthic organisms at Sungai Bera were very much lower when compared to those at Sungai Tali and Sungai Lumut. The hydrocarbon levels were highest at Sungai Bera, and least at Sungai Lumut. The distribution pattern corresponds well with the levels of hydrocarbons found at the three sites. Hydrocarbons found at the three sites were of petrogenic origin.The effects of the wastewater discharged on the intertidal zone were very localized, confined mainly to Sungai Bera. The hydrocarbon levels at Sungai Tali were almost the same as those at Sungai Lumut. No deleterious effects on the macrobenthic community were detected at these two sites.     

Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities

Tributaries may either ameliorate or exacerbate the geomorphic and ecologic impacts of flow regulation by altering the flux of water and sediment into the flow‐regulated mainstem. To capture the effects of tributary influences on a flow regulated river, long‐term discharge and cross‐sectional data are used to assess the geomorphic and hydrologic impacts of impoundment. In addition, the use of the short‐lived cosmogenic radioisotope ⁷Be (half‐life 53·4 days) to link sediment transport dynamics to benthic macroinvertebrate community structure is evaluated. It is found that the ⁷Be activity of transitional bed load sediment is highly seasonal and reflects both variations in activity of sediment sources and limited sediment residence time within the junction. Benthic communities also exhibit a strong seasonal variability. In the spring, neither the ⁷Be activity of the sediment, nor benthic communities exhibit clear relationships with sample site location. In contrast, during the late summer the ratio of Ephemeroptera (mayflies)/Trichoptera (caddisflies) decreased significantly below tributary junctions. This decrease in benthic community ratio was driven by increases in caddisfly abundance and was strongly correlated with the presence of recently ⁷Be tagged transitional bedload sediment. These observations are probably associated with the presence of coarse, stable, and unembedded substrate downstream of tributaries and the rapid turnover of sediment that may also be associated with a rapid flux in nutrients or seston. The results show that tributaries are impacting the flow‐regulated mainstem and that these impacts are reflected in the benthic community structure and in the ⁷Be activity of transitional bed load sediment. Moreover, the observed reduction in competence and capacity of the mainstem following flood control suggests that these spatial discontinuities may be a consequence of impoundment. Copyright © 2008 John Wiley & Sons, Ltd.     

Influence of a Brazilian sewage outfall on the toxicity and contamination of adjacent sediments

The submarine sewage outfall of Santos (SSOS) is situated in the Santos Bay (São Paulo, Brazil) and is potentially a significant source of contaminants to the adjacent marine ecosystem. The present study aimed to assess the influence of SSOS on the sediment toxicity and contamination at Santos Bay. At the disposal site, sediments tended to be finer, organically richer and exhibited higher levels of surfactants and metals, sometimes exceeding the “Threshold Effect Level” values. The SSOS influence was more evident toward the East, where the sediments exhibited higher levels of TOC, total S and metals during the summer 2000 sampling campaign. Sediment toxicity to amphipods was consistently detected in four of the five stations studied. Amphipod survival tended to correlate negatively to Hg, total N and % mud. This work provides evidence that the SSOS discharge affects the quality of sediments from Santos Bay, and that control procedures are warranted.     

Improvement of the sediment ecosystem following diversion of an intertidal sewage outfall at the Fraser river estuary,Canada, with emphasis on Corophium salmonis (Amphipoda)

Primary treated sewage effluent from the city of Vancouver, Canada was deposited directly onto the intertidal ecosystem of Sturgeon bank, Fraser river estuary between 1962 and 1988. In response to the degraded sediment conditions an azoic zone developed near the discharge outfall. Effluent discharges into the intertidal zone were almost completely stopped in 1988 with the construction of a submerged outfall. Our studies, conducted between 1994 and 1996, showed considerable improvement in the environment of the mudflat ecosystem, including increased dissolved oxygen, decreased sediment chlorophyll, decreased organic material in the sediment, reduced heavy metals in surficial sediment and increased grain size. The amphipod Corophium salmonis, important in the food web for juvenile salmon and other fish species, recolonized the previously azoic location. At reference stations, C. salmonis density was similar to that observed in previous surveys two decades earlier. Our data strongly suggest that improvement or sediment conditions near the former sewage outfall was a major factor enabling colonization by C. salmonis.     

Subtidal assemblages on rocky reefs at a cliff-face sewage outfall (North Head, Sydney, Australia): What happened when the outfall was turned off?

For many years, sewage was continuously discharged via inshore outfalls into shallow subtidal habitats around Sydney (New South Wales). In 1990, deepwater ocean outfalls were commissioned and inshore discharge ceased. This study examined the assemblage of organisms found on subtidal cliffs at one inshore outfall to examine differences in, or recovery by, the biota when sewage was no longer discharged. This assemblage was primarily composed of filter-feeding animals (sponges, ascidians, bryozoans, anthozoans) and encrusting algae. Differences and changes in the assemblages at a number of different spatial scales, relative to the assemblages at two reference locations, were examined four times over a 20 month period. Although most taxa showed significant changes over the study period, most of these were unpredictable and varied interactively according to the taxon, plot, depth and location. For most measures, however, the location where sewage had been released lay within the natural variability shown by the reference locations. The implications of these findings are discussed with respect to other studies on the effects of sewage on intertidal and shallow subtidal habitats.     

Effects of environmental factors and predation on benthic communities in headwater streams

Structure and composition of benthic macroinvertebrate assemblages were investigated during three consecutive years in six headwater streams that exhibit a high variation in environmental conditions, habitat structure and predatory pressure. We examined whether the abundance of functional feeding groups could be best predicted by the abundance of predators and some habitat and chemical variables. Mean density and biomass of macroinvertebrate functional feeding groups varied significantly throughout the study area. Stepwise multiple regression analyses revealed that both density and biomass of functional feeding groups was influenced primarily by chemical features of water. Shredder biomass and scraper density were also influenced by habitat features, the abundance of scrapers increasing in deeper localities at lower altitudes and with abundant macrophytes. The abundance of predatory invertebrates was related to the density and biomass of benthic prey. An influence of fish predation on invertebrate communities was not observed in the study streams. The finding that benthic communities in undisturbed headwater streams are mainly affected by water chemistry variables irrespective of fish predation and habitat features clearly highlight the sensitivity of functional feeding groups to changes in chemical features and their role as indicators for bioassessment.     

Effect of streambed sediment on benthic ecology

Benthic macroinvertebrates have been commonly used as indicator species for assessment of aquatic ecology. Streambed sediment, or substrate, plays an important role in habitat conditions for macroinvertebrate communities. Field investigations were done to study the benthic diversity and macroinvertebrate compositions in various stream substrata. Sampling sites with different bed sediment, latitude, and climate were selected along the Yangtze River, the Yellow River, the East River, and the Juma River, in China. The results show that benthic community structures found in different substrata clearly differ, while those found in substrata of similar composition and flow conditions but in different macroclimates are similar. The study, thus, demonstrates that the benthic macroinvertebrate community is mainly affected by substrate composition and flow conditions, but is generally unaffected by latitudinal position and macroclimate. Taxa richness of the maeroinvertebrate community was found to be the highest on hydrophyte-covered cobbles, high on moss-covered bedrock, and low on clay beds and cobble beds devoid of plant biomass. Sandy beds are compact and unstable, thus, no benthic macroinvertebrates were found colonizing such substrata. Aquatic insects account for most of the macroinvertebrates collected in these rivers. Different insects dominate in different types of substrata： mainly EPT species （Ephemeroptera, Ptecoptera, Tfichoptera） in cobble, gravel, and moss-covered bedrock; and Chironomidae larvae in clay beds. The relation between the number of species in the samples and the size of the sampling area fits a power function of the species area. One square meter （lm） is suggested as the minimum sampling area. A substrate suitability index is proposed by integrating the suitability of sediment, periphyton, and benthic organic materials for macroinvertebrates. The biodiversity of macroinvertebrates increases linearly with the substrate suitability index. Benthic taxa richness increases linearly with the suitability index.     

Medium-term responses of rocky bottoms to sewage discharges from a deepwater outfall in the NE Atlantic

An investigation on the effects of deepwater outfall discharges on the status of rocky reef communities was carried out. The sanitation system was found to be an environmentally suitable option for the protection of those habitats situated in high energy coastal environments. Sediments occurring between the predominating rocky substrates showed low values of the fine fraction (<63microm) and organic matter content. In addition, high average concentrations of Cd, Hg and Zn were found in these sediments, though these values were similar to those registered in non-affected sites, far away from the outfall. On the other hand, those assemblages typical of hard substrates that settled near the outfall showed an increase in total richness and abundance of macroinvertebrates. Moreover, the average number of species of each taxonomic group, a good indicator of the maintenance of the previous trophic structure, only varied considerably over time at the rip-rap protection. In a global context, those changes were not directly related to the discharge disturbances, but to the natural variability or the successional processes occurring within those communities. Only communities dwelling in the rip-rap protection area were affected by the proximity of the discharges.     

Spatial and temporal patterns of the infaunal community near a major ocean outfall in Southern California

Effects of waste water discharge from a major ocean outfall in Southern California to the benthic infaunal community were examined during a 5-year monitoring programme. Natural features, primarily water depth, accounted for 82% of the variability in the infaunal community, while discharge-related effects represented less than 8% of the variability. The area immediately adjacent to the diffuser had the strongest outfall effects. Infaunal abundance showed a pattern of enhancement centred at the outfall. Diversity was also high, indicating that the area was not characterized by a degraded community.     

Implications of dredging induced changes in sediment particle size composition for the structure and function of marine benthic macrofaunal communities

A meta-analysis approach was used to assess the effect of dredging induced changes in sediment composition, under different conditions of natural physical disturbance, for the structure and function of marine benthic macrofaunal communities. Results showed the sensitivity of macrofaunal communities increased as both the proportion of gravel increased and the level of natural physical disturbance decreased. These findings may be explained by the close association of certain taxa with the gravel fraction, and the influence of natural physical disturbance which, as it increases, tends to restrict the colonisation by these species. We conclude that maintaining the gravel content of surface sediments after dredging and, where practicable, locating extraction sites in areas of higher natural disturbance will minimise the potential for long-term negative impacts on the macrofauna.     

Sublethal effects of the antibiotic tylosin on estuarine benthic microalgal communities

Pharmaceuticals are common chemical contaminants in estuaries receiving effluent from wastewater and sewage treatment facilities. The purpose of this research was to examine benthic microalgal (BMA) community responses to sublethal exposures to tylosin, a common and environmentally persistent antibiotic. Bioassays, using concentrations of 0.011–218 μmol tylosin l⁻¹, were performed on intertidal muddy sediments from North Inlet Estuary, SC. Exposure to tylosin resulted in a reduction in total BMA biomass and primary productivity. Furthermore, exposure seemed to retard diatom growth while having a minimal effect on cyanobacteria biomass. Estuarine systems receiving chronic inputs of trace concentrations of tylosin, as well as other antibiotics, may experience significant reductions in BMA biomass and primary productivity. Given the well-documented role of BMA in the trophodynamics of estuaries, these impacts will likely be manifested in higher trophic levels with possible impairments of the structure and function of these sensitive systems.     

Sediment disturbance off the Tagus Estuary, Western Portugal: chronic contamination, sewage outfall operation and runoff events

Sediment disturbance patterns in the coastal area off the Tagus Estuary (Portugal) have been assessed using a set of combined techniques. The potential sources of disturbance in the area include chronic contamination of the fine sediments originating from the estuary, a local input from a long-sea sewage outfall and occasional high runoff episodes following torrential rain. The Sediment Quality Triad approach, combining environmental chemistry (namely organic contaminants), macrofaunal benthic communities and laboratory sediment toxicity assays, was performed on sediment samples from 20 sites. The samples were collected before the outfall commenced operation and four years after commissioning, in order to evaluate the relative magnitudes of the three potential sources of disturbance. The sediment contamination created by the estuary was identified as the most important cause of reduced sediment quality, as disturbance in all three components of the Sediment Quality Triad were only found in a site located near the estuary.     

Development of a benthic index to assess sediment quality in the Tampa Bay Estuary

The identification, remedial treatment, and monitoring of contaminated sediments are among the priorities for managers of the Tampa Bay Estuary. Tampa Bay, as an urbanized estuary, is subject to the input of watershed sources of chemical contaminants, including metals, pesticides, and organic chemicals. Although the use of biological indicators and their incorporation into multi-metric indices is not new, the refinement and applications of such techniques for determining environmental condition still require further development and exploration. We present a single Tampa Bay Benthic Index (TBBI) that was developed specifically for Tampa Bay. Stepwise discriminant analysis was applied to a comprehensive list of potential benthic metrics. Results from the stepwise procedure identified the metrics that best discriminated between "healthy" and "degraded" conditions, as defined by sediment contaminant effect levels and dissolved oxygen. Discriminant analysis was then applied to the resultant three variables to determine the linear combination for the index.     

Shallow sublittoral meiofauna communities and sediment polycyclic aromatic hydrocarbons (PAHs) content on the Galician coast (NW Spain), six months after the Prestige oil spill

The aim of this work was to detect the impact of Prestige oil spill on meiobenthic community structure at higher levels of taxonomic aggregation. In addition, the relationship between sediment individual polycyclic aromatic hydrocarbon (PAH) concentration and meiofauna community structure was investigated. Six months after the Prestige oil spill, meiobenthos community and sediment PAHs content from seven shallow subtidal localities along the Galician coast were studied. Two sites presented differences in community structure, characterized by high densities of nematodes, gastrotrichs and turbellarians, and low densities of copepods. Chrysene and triphenylene were only found at these two disturbed sites and could be responsible for differences of meiobenthos community structure. However, differences in community structure of sites could be linked with sedimentary parameters, and discrimination between the effect of PAHs and sedimentary parameters was impossible due to the lack of baseline studies on meiobenthos and PAHs contents in this area.     

A possible method for the detection of pollution-induced disturbance on marine benthic communities

In unpolluted areas the log-normal distribution of individuals per species fits well data from many benthic communities. Using a simple plotting method, under slight pollution the data show a distinct break in the normally straight line log-normal plot and the plot covers more geometric classes than data from unpolluted areas. Under more severe pollution stress the data show a return to a log-normal distribution, but with a shallower slope, and span more geometric classes than data from less polluted areas. The above-mentioned patterns are consistent for spatial effects of pollution in Oslofjord and for temporal effects in data from a Scottish sea loch and also apply to other communities. An explanation of the reasons for such patterns is given and consideration given to the robustness of and application of the methods described.