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 mariculture on macrobenthic assemblages in a western mediterranean site

The effects of solid organic wastes from a marine fish farm on sediment was tested using macrobenthic fauna as biological indicators. Impact on benthic fauna was evaluated in the vicinity of a fish farm in the Tyrrhenian Sea (Western Mediterranean) between July 2001 and October 2002. Changes in benthic community structure were investigated using multivariate, distributional and univariate analyses (diversity indices, AMBI and M-AMBI). The results showed sharp disturbance of assemblages under the cages and no effects in the area more than 25 m from the cages. Sediment alterations were related to an increase in farmed biomass and its wastes, as well as to low current speed that allowed accumulation of organic matter on the sea floor. It was possible to follow the ecological succession from slightly altered assemblages to heavily polluted ones in the very short period of a single fish fattening cycle (15 months).     

Nutrient dynamics in seawater column in the vicinity of Piran submarine sewage outfall (North Adriatic)

Variations of nitrogen and phosphorus concentrations in the vicinity of Piran (North Adriatic) submarine sewage outfall were studied as well as the treatment plant operation. On the basis of the data it was concluded that the influence of the outfall to the nutrient level in that area is negligible. In comparison the data from the shallow organically polluted water in the inner part of the Bay of Koper are reported.     

Effects of the closure of a major sewage outfall on sublittoral, soft sediment benthic communities

The present study examines the benthos within western inner Swansea Bay (Wales, UK), for the period before, during and immediately after the cessation of a major, sewage discharge from Mumbles Head. There have been significant improvements in seawater quality and changes in the species composition of the benthic communities following the cessation of the sewage discharge. There has been an increase in the diversity of deposit feeders, especially the amphipods, and a decrease in the diversity of the filter feeders, especially the polychaetes. Changes are not attributable either to sediment organic matter content or to gross changes in sediment type, but are related to the significant reduction in suspended particulate organic material and sewage contaminants discharged to the Bay. A recovery model has been proposed to describe how soft sediment benthic communities in a shallow, sublittoral, high tidal energy environment respond to the abrupt cessation of a major sewage discharge.     

Influence of tuna penning activities on soft bottom macrobenthic assemblages

The influence of tuna penning on soft bottom habitat present in the vicinity of tuna pens and at distances 200 m and 1.5 km away, was assessed by comparing attributes of macroinvertebrate assemblages and sediment quality before (November 2000, March 2001) and after (November 2001, April 2002) initiation of the activity. Results from November 2001 indicated a significant increase in sediment organic carbon and organic nitrogen, and a non-significant increase in the abundance of Capitellidae in the vicinity of the cages. Similar results were obtained 200 m from the cages but not 1.5 km away, where the only change was a significant increase in organic nitrogen in sediment. Results from April 2002 indicated no significant change in sediment organic carbon and organic nitrogen, however, mean sediment grain size decreased significantly in the immediate vicinity of the cages. Changes in attributes of the benthic assemblages and sediment resulted from accumulation of uneaten feed-fish on the seabed.     

Effects of reclamation on macrobenthic assemblages in the coastline of the Arabian Gulf: a microcosm experimental approach

Coastal reclamation and modifications are extensively carried out in Bahrain, which may physically smother the coastal and subtidal habitats resulting in changes to abundance and distribution of macrobenthic assemblages. A microcosm laboratory experiment using three common macrobenthic invertebrates from a proposed reclaimed coastal area was preformed to examine their responses to mud burial using marine sediment collected from a designated borrow area. Significant difference in numbers of survived organisms between control and experimental treatments with a survival percentage of 41.8% for all of the selected species was observed. The polychaete Perinereis nuntia showed the highest percentage of survival (57.1%) followed by the bivalve Tellinavaltonis (42.3%) and the gastropod Cerithidea cingulata (24.0%). Quantifying species responses to sediment burial resulted from dredging and reclamation will aid in predicting the expected ecological impacts associated with coastal developments and subsequently minimizing these impacts and maintaining a sustainable use of coastal and marine ecosystems in the Arabian Gulf.     

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.     

Evidence for the effects of metal contamination on the intertidal macrobenthic assemblages of the Fal Estuary

The intertidal invertebrate macrofauna of five creeks in the Fal estuarine system, Cornwall, UK, is compared with data from 40 locations in six other estuaries in south-west Britain. Multivariate analysis shows that the community composition in the Fal is distinct from all the other estuaries. The differences are principally due to the absence of two crustacean species, Corophium voluntator and Cyathura carinata, and the high abundance of small opportunistic annelid species. The Fal Estuary is heavily contaminated with heavy metals as a result of mining in the catchment, and the faunistic features are commensurate with what is known of the relative sensitivities of marine invertebrate taxa to pollution.     

Estimation of nearshore groundwater discharge and its potential effects on a fringing coral reef

Radon (²²²Rn) measurements were conducted in Shiraho Reef (Okinawa, Japan) to investigate nearshore submarine groundwater discharge (SGD_nearshore) dynamics. Estimated average groundwater flux was 2-3 cm/h (maximum 7-8 cm/h). End-member radon concentration and gas transfer coefficient were identified as major factors influencing flux estimation accuracy. For the 7-km long reef, SGD_nearshore was 0.39-0.58 m³/s, less than 30% of Todoroki River’s baseflow discharge. SGD_nearshore was spatially and temporally variable, reflecting the strong influence of subsurface geology, tidal pumping, groundwater recharge, and hydraulic gradient. SGD_nearshore elevated nearshore nitrate concentrations (0.8-2.2 mg/l) to half of Todoroki River’s baseflow -N (2-4 mg/L). This increased nearshore Chl-a from 0.5-2 μg/l compared to the typically low Chl-a (<0.1-0.4 μg/l) in the moat. Diatoms and cyanobacteria concentrations exhibited an increasing trend. However, the percentage contributions of diatoms and cyanobacteria significantly decreased and increased, respectively. SGD may significantly induce the proliferation of cyanobacteria in nearshore reef areas.     

The effects of sewage discharge on shallow hard substrate sessile assemblages

On rocky shores, sewage discharges can modify natural distribution patterns of sessile organisms. The impact of sewage on shallow hard substrate assemblages has been assessed along SW Apulian coast (Ionian Sea, Italy), providing a framework to evaluate the benefits of future sewage displacement to deeper waters. Four locations (three controls and one putatively impacted) were selected and three sites were chosen at each location. Each site was sampled by 10 replicate photographic records. Univariate analyses revealed that the outfall did not affect the spatial distribution of number of taxa, total cover and abundance of some dominant taxa (mostly algae, sponges and bryozoans). The outfall negatively influenced the natural distribution pattern of filamentous green algae, whilst some algae (i.e. Gelidiales and Colpomenia sinuosa) were exclusively present at the impacted location. Multivariate analyses revealed that the outfall heavily modified the natural pattern of variability in the structure of the assemblage.     

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.     

Toxicological impact assessment of heavy metal contamination on macrobenthic communities in southern coastal sediments of Korea

In the heavily industrialized Masan Bay of southern coast, Korea, the potential harmful effects of heavy metals (Cd, Co, Cu, Ni, Pb, Sn, Zn, and Hg) were evaluated in terms of the pollution load index (PLI) and ecological risk assessment index (ERI) methods, and the results obtained were considered alongside the health of the macrobenthic fauna communities. The results revealed that the bay sediments, especially in the inner bay and the outfall area of a sewage treatment plant, are exposed to moderate to serious levels of metal pollution. Hg and Cd contributed the most to the potential toxicity response indices in sediments recently deposited in the bay. The potential ecological risk assessment of heavy metals in the bay was highlighted by the use of the benthic biological pollution index (BPI), suggesting that the ERI is a useful toxicity response index, which can quantify the overall ecological risk level to a target environment.     

Effects of beach slope breaks on nearshore groundwater dynamics

Interactions between fresh groundwater and seawater affect significantly the nearshore pore water flow, which in turn influences the fate of nutrients and contaminants in coastal aquifers prior to discharge to the marine environment. Field investigations and numerical simulations were carried out to examine the groundwater dynamics in the intertidal zone of a carbonate sandy aquifer on the tropical island of Rarotonga, Cook Islands. The study site was featured by distinct cross‐shore slope breaks on the beach surface. Measured pore water salinities revealed different distributions under the influences of different beach profiles, inland heads, and tidal oscillations. Fresh groundwater was found to discharge around a beach slope break located in the middle area of the intertidal zone. The results indicate a strong interplay between the slope break beach morphology and tidal force in controlling the nearshore groundwater flow and solute transport. The fresh groundwater discharge location was largely determined by the beach morphology in combination with the tidal force. The nearshore groundwater flow can be very sensitive to beach slope breaks, which induce local circulation and flow instabilities. As slope breaks are a common feature of beaches around the world, these results have important, general implications for future studies of nutrients transport and transformations in nearshore aquifers and associated fluxes via submarine groundwater discharge.     

Evaluation of sewage source and fate on southeast Florida coastal reefs

Water, sponge and coral samples were collected from stations impacted by a variety of pollution sources and screened for human enteric viruses as conservative markers for human sewage. While human enteroviruses and adenoviruses were not detected, noroviruses (NoV; human genogroups I and II) were detected in 31% of samples (especially in sponge tissue). Stations near inlets were the only ones to show multiple sample types positive for NoV. Fecal indicator bacteria and enteric viruses were further evaluated at multiple inlet stations on an outgoing tide. Greatest indicator concentrations and highest prevalence of viruses were found at the mouth of the inlet and offshore in the inlet plume. Results suggest that inlets moving large volumes of water into the coastal zone with tides may be an important source of fecal contaminants. Efforts to reduce run-off or unintended release of water into the Intracoastal Waterway may lower contaminants entering sensitive coastal areas.     

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.     

The effect of the new Massachusetts Bay sewage outfall on the concentrations of metals and bacterial spores in nearby bottom and suspended sediments

Since the new outfall for Boston's treated sewage effluent began operation on September 6, 2000, no change has been observed in concentrations of silver or Clostridium perfringens spores (an ecologically benign tracer of sewage), in bottom sediments at a site 2.5 km west of the outfall. In suspended sediment samples collected with a time-series sediment trap located 1.3 km south of the outfall, silver and C. perfringens spores increased by 38% and 103%, respectively, in post-outfall samples while chromium, copper, and zinc showed no change. All metal concentrations in sediments are <50% of warning levels established by the Massachusetts Water Resources Authority. An 11-year data set of bottom sediment characteristics collected three times per year prior to outfall startup provides perspective for the interpretation of post-outfall data. A greater than twofold increase in concentrations of sewage tracers (silver and C. perfringens) was observed in muddy sediments following the exceptional storm of December 11-16, 1992 that presumably moved contaminated inshore sediment offshore.     

Effects of nutrient enrichment on macroalgal coralligenous assemblages

Effects of eutrophication on marine ecosystems have been widely studied, even if both the effects on deep subtidal rocky assemblages and response of different successional stages to nutrients impact are still not clear. In this context, the study aimed to evaluate the effects of nutrient enrichment on Mediterranean macroalgal assemblages associated with coralligenous habitat. A manipulative field experiment was carried out by supplying both mature and early successional stages of assemblages with nutrients. A total of 62 macroalgal species were identified. Multivariate and univariate analyses showed that the structure of both mature and early successional macroalgal assemblages of coralligenous significantly varied between areas treated with nutrients and not treated areas. Moreover, differences were stronger when macroalgal assemblages were in the early successional stage than in the mature one. Results highlighted the role played by nutrients in determining the structure of macroalgal coralligenous assemblages, furthermore suggesting possible synergetic effects with other kinds of disturbances.     

Temporal and spatial variability of radium in the coastal ocean and its impact on computation of nearshore cross-shelf mixing rates

Constraining the exchange of water from the shoreline to the mid-shelf is necessary for the development of accurate and predictive models of nearshore circulation. Ra isotopes, which emanate from sediments and have a variety of half-lives, may be useful in measuring cross-shelf mixing rates. The distributions of Ra isotopes were measured in transects extending perpendicular from the shoreline at Sunset Beach and Huntington Beach, CA. The average inventory at Sunset Beach was four times greater than at Huntington Beach. Building on previous research on Ra inputs and circulation in San Pedro Bay, a two-dimensional model for surface water Ra was developed to identify the importance of onshore flow and cross-shelf mixing near Huntington Beach. For the mean summertime conditions, the eddy diffusivity (K_h) was 1.4±0.4 m² s⁻¹, with 8% of the water from Sunset Beach moving down the coast. The remaining water must be low-Ra water that has moved onshore. At time scales greater than a week, the short-lived Ra inventory at Huntington Beach varied by 50%, which reflects changes in the fractions of water moving down-coast and/or in the longshore advection rate. The shoreline Ra concentration varied on time scales of hours, which may be generated by tidal changes in the Ra input at the shoreline and short-period fluctuations in the mixing rate. The low K_h observed in this study in comparison to higher values measured further offshore is evidence that K_h increases with distance offshore. When scale-dependent mixing beyond 455 m offshore is incorporated into the model, the results are consistent with the observed data for ²²³Ra, ²²⁴Ra, and ²²⁸Ra. Using the model, the ²²⁸Ra input flux to the summertime mixed layer was between 3.4×10⁶ and 4.0×10⁶ atoms s⁻¹ (m shoreline)⁻¹.     

Effects of extreme climate events on the macrobenthic communities' structure and functioning of a temperate estuary

The Mondego estuary (Portugal) experienced profound structural and functional modifications due to eutrophication, which was exacerbated by consecutive weather extremes that compromised a previous restoration project. This work explores multiple climate impacts on macrobenthic communities’ structure and functioning and its implications on ecosystem’s recovery. Floods and heat waves had a stronger negative effect on macrobenthic assemblages than the droughts, imposing a total abundance decline. Contrarily, biomass was not so affected by climate events, being stable and even increased in a mudflat area, where seagrass is re-colonizing. Bivalves and oligochaetes decreased with the flooding episodes, likewise subsurface-deposit feeders and suspension feeders, while crustaceans were particularly sensitive to heat waves. Species richness declined with the floods and heat waves, whilst evenness increased in sandflat area, constituting a positive sign towards recovery. Succession of different climate extremes affected ecosystem structure and functioning, delaying its recovery with possible consequent effects at higher trophic levels.