(Table 2) Seasonal flux data and percentages of major bulk components of total flux at the mesotrophic sediment trap site CB from 1988 - 2012

A more than two-decadal sediment trap record from the Eastern Boundary Upwelling Ecosystem (EBUE) off Cape Blanc, Mauritania, is analysed with respect to deep ocean mass fluxes, flux components and their variability on seasonal to decadal timescales. The total mass flux revealed interannual fluctuations which were superimposed by fluctuations on decadal timescales. High winter fluxes of biogenic silica (BSi), used as a measure of marine production (mostly by diatoms) largely correspond to a positive North Atlantic Oscillation (NAO) index (December-March). However, this relationship is weak. The highest positive BSi anomaly was in winter 2004-2005 when the NAO was in a neutral state. More episodic BSi sedimentation events occurred in several summer seasons between 2001 and 2005, when the previous winter NAO was neutral or even negative. We suggest that distinct dust outbreaks and deposition in the surface ocean in winter and occasionally in summer/autumn enhanced particle sedimentation and carbon export on short timescales via the ballasting effect. Episodic perturbations of the marine carbon cycle by dust outbreaks (e.g. in 2005) might have weakened the relationships between fluxes and large-scale climatic oscillations. As phytoplankton biomass is high throughout the year, any dry (in winter) or wet (in summer) deposition of fine-grained dust particles is assumed to enhance the efficiency of the biological pump by incorporating dust into dense and fast settling organic-rich aggregates. A good correspondence between BSi and dust fluxes was observed for the dusty year 2005, following a period of rather dry conditions in the Sahara/Sahel region. Large changes of all bulk fluxes occurred during the strongest El Niño-Southern Oscillation (ENSO) in 1997-1999 where low fluxes were obtained for almost 1 year during the warm El Niño and high fluxes in the following cold La Niña phase. For decadal timescales, Bakun (1990) suggested an intensification of coastal upwelling due to increased winds (''Bakun upwelling intensification hypothesis''; Cropper et al., 2014) and global climate change. We did not observe an increase of any flux component off Cape Blanc during the past 2 and a half decades which might support this. Furthermore, fluxes of mineral dust did not show any positive or negative trends over time which might suggest enhanced desertification or ''Saharan greening'' during the last few decades.

Widespread contamination of coastal sediments in the Transmanche Channel with anti-androgenic compounds

This study analysed the levels of androgen receptor antagonist activity in extracts of coastal sediments sampled from estuaries in southern UK and northern France. Anti-androgenic (AA) activity varied between <0.2 and 224.3±38.4μg flutamide equivalents/g dry weight of sediment and was significantly correlated with the total organic carbon and silt content of samples. AA activity was detected in tissues extracts of clams, Scrobicularia plana, sampled from a contaminated estuary, some of which was due to uptake of a series of 4 or 5 ring polycyclic aromatic hydrocarbons (PAHs). Initial studies also indicated that fractionated extracts of male, but not female, clams also contained androgen receptor agonist activity due to the presence of dihydrotestosterone in tissues. This study reveals widespread contamination of coastal sediments of the Transmanche region with anti-androgenic compounds and these contaminants should be investigated for their potential to disrupt sexual differentiation in aquatic organisms.

Widespread contamination of coastal sediments in the Transmanche Channel with anti-androgenic compounds

This study analysed the levels of androgen receptor antagonist activity in extracts of coastal sediments sampled from estuaries in southern UK and northern France. Anti-androgenic (AA) activity varied between <0.2 and 224.3±38.4μg flutamide equivalents/g dry weight of sediment and was significantly correlated with the total organic carbon and silt content of samples. AA activity was detected in tissues extracts of clams, Scrobicularia plana, sampled from a contaminated estuary, some of which was due to uptake of a series of 4 or 5 ring polycyclic aromatic hydrocarbons (PAHs). Initial studies also indicated that fractionated extracts of male, but not female, clams also contained androgen receptor agonist activity due to the presence of dihydrotestosterone in tissues. This study reveals widespread contamination of coastal sediments of the Transmanche region with anti-androgenic compounds and these contaminants should be investigated for their potential to disrupt sexual differentiation in aquatic organisms.

An evaluation of trace metal distribution, enrichment factors and risk in sediments of a coastal lagoon (Ria de Aveiro, Portugal)

This paper describes a sediment survey undertaken to unravel patterns of distribution and dispersion of trace metals in an Iberian Peninsula northwestern coastal lagoon (Ria de Aveiro). Cadmium, lead, chromium, copper and zinc were analyzed in bottom sediments. Geochemical normalization is performed and two different regression models for each metal versus aluminum are tested and compared using the respective enrichment factors (EF), an estimation of the relative importance of anthropogenic contributions to the studied sediments. Mean sediment quality guideline quotients (mSQGQ) are used to evaluate sediment quality and associated potential risk to biota with effects range low as empirical sediment quality guideline (SQG) in the basis for mSQGQ calculation. Additionally, the geoaccumulation index is calculated to compare studied sediment levels to global baseline levels. The application of SQGs revealed insufficient characterization capability, especially when contrasted to EF calculated from the regression methods. These pointed a mildly enriched system with localized “hot spot” areas. Therefore, it can be considered that bottom sediments in the Ria de Aveiro system are in their majority unpolluted, zinc being the only metal of concern, presenting enrichment in all four main channels. The major rivers outlets (Caster, Antuã, and Vouga) constitute point sources, thus presenting potential risk for biota. Yet, the strong tidal influence creates a damping effect by efficiently redistributing sediment bound metals.

Sediment Budget for Cane Land on the Lower Herbert River Floodplain, North Queensland, Australia

Land use in the river catchments of tropical North Queensland appears to have increased the export of sediment and nutrients to the coast. Although evidence of harmful effect of sediment on coastal and riverine ecosystems is limited, there is a growing concern about its possible negative impacts. Sugarcane cultivation on the floodplains of the tropical North Queensland river catchments is thought to be an important source of excess sediment in the river drainage systems. Minimum-tillage, trash blanket harvesting has been shown to reduce erosion from sloping sugarcane fields, but in the strongly modified floodplain landscape other elements (e.g. drains, water furrows and headlands) could still be important sediment sources. The main objectives of this thesis are to quantify the amount of sediment coming from low-lying cane land and identify the important sediment sources in the landscape. The results of this thesis enable sugarcane farmers to take targeted measures for further reduction of the export of sediment and nutrients. Sediment budgets provide a useful approach to identify and quantify potential sediment sources. For this study a sediment budget is calculated for a part of the Ripple Creek catchment, which is a sub-catchment of the Lower Herbert River. The input of sediment from all potential sources in cane land and the storage of sediment within the catchment have been quantified and compared with the output of sediment from the catchment. Input from, and storage on headlands, main drains, minor drains and water furrows, was estimated from erosion pin and surface profile measurements. Input from forested upland, input from fields and the output at the outlet of the catchment was estimated with discharge data from gauged streams and flumes. Data for the sediment budget were collected during two ‘wet’-seasons: 1999-2000 and 2000-2001. The results of the sediment budget indicate that this tropical floodplain area is a net source of sediment. Plant cane fields, which do not have a protective trash cover, were the largest net source of sediment during the 1999-2000 season. Sediment input from water furrows was higher, but there was also considerable storage of sediment in this landscape element. Headlands tend to act as sinks. The source or sink function of drains is less clear, but seems to depend on their shape and vegetation cover. An important problem in this study is the high uncertainty in the estimates of the sediment budget components and is, for example, likely to be the cause of the imbalance in the sediment budget. High uncertainties have particularly affected the results from the 20002001 season. The main source of uncertainty is spatial variation in the erosion and deposition processes. Uncertainty has to be taken into consideration when interpreting the budget results. The observation of a floodplain as sediment source contradicts the general understanding that floodplains are areas of sediment storage within river catchments. A second objective of this thesis was therefore to provide an answer to the question: how can floodplains in the tropical North Queensland catchments can be a source of sediment? In geomorphic literature various factors have been pointed out, that could control floodplain erosion processes. However, their importance is not 'uniquely identified'. Among the most apparent factors are the stream power of the floodwater and the resistance of the floodplain surface both through its sedimentary composition and the vegetation cover. If the cultivated floodplains of the North Queensland catchments are considered in the light of these factors, there is a justified reason to expect them to be a sediment source. Cultivation has lowered the resistance of their surface; increased drainage has increased the drainage velocity and flood control structures have altered flooding patterns. For the Ripple Creek floodplain four qualitative scenarios have been developed that describe erosion and deposition under different flow conditions. Two of these scenarios were experienced during the budget study, involving runoff from local hillslopes and heavy rainfall, which caused floodplain erosion. In the longer term larger flood events, involving floodwater from the Herbert River, may lead to different erosion and deposition processes. The present study has shown that the tropical floodplain of the Herbert River catchment can be a source of sediment under particular flow conditions. It has also shown which elements in the sugarcane landscape are the most important sediment sources under these conditions. This understanding will enable sugarcane farmers to further reduce sediment export from cane land and prevent the negative impact this may have on the North Queensland coastal ecosystems.

Spatial and temporal interaction between sediment and microphytobenthos in a temperate estuarine macro-intertidal bay

Intertidal flats of the estuarine macro-intertidal Baie des Veys (France) were investigated to identify spatial features of sediment and microphytobenthos (MPB) in April 2003. Gradients occurred within the domain, and patches were identified close to vegetated areas or within the oyster-farming areas where calm physical conditions and biodeposition altered the sediment and MPB landscapes. Spatial patterns of chl a content were explained primarily by the influence of sediment features, while bed elevation and compaction brought only minor insights into MPB distribution regulation. The smaller size of MPB patches compared to silt patches revealed the interplay between physical structure defining the sediment landscape, the biotic patches that they contain, and that median grain-size is the most important parameter in explaining the spatial pattern of MPB. Small-scale temporal dynamics of sediment chl a content and grain-size distribution were surveyed in parallel during 2 periods of 14 d to detect tidal and seasonal variations. Our results showed a weak relationship between mud fraction and MPB biomass in March, and this relationship fully disappeared in July. Tidal exposure was the most important parameter in explaining the summer temporal dynamics of MPB. This study reveals the general importance of bed elevation and tidal exposure in muddy habitats and that silt content was a prime governing physical factor in winter. Biostabilisation processes seemed to behave only as secondary factors that could only amplify the initial silt accumulation in summer rather than primary factors explaining spatial or long-term trends of sediment changes.

A national coastal erosion risk assessment for Scotland

The geography of Scotland, with a highly undulating hinterland, long and indented coastline, together with a large number of islands, means that much social and economic activity is largely located at the coast. The importance of the coast is further highlighted by the large number of ecosystem services derived from the coast. The threat posed by climate change, particularly current and future sea level rise, is of considerable concern and the associated coastal erosion and coastal flooding has the potential to have a substantial effect on the socioeconomic activity of the whole country. Currently, the knowledge base of coastal erosion is poor, which serves to hinder the current and future management of the coast. This research reported here aimed to establish four key aspects of coastal erosion within Scotland: the physical susceptibility of the coast to erosion; the assets exposed to coastal erosion; the vulnerability of communities to coastal erosion; and the coastal erosion risk to those communities. Coastal erosion susceptibility was modelled here within a GIS, using data for ground elevation, rockhead elevation, wave exposure and proximity to the open coast. Combining these data produced the Underlying Physical Susceptibility Model (UPSM), in the form of a 50 m2 raster of national coverage. The Coastal Erosion Susceptibility Model (CESM) was produced with the addition of sediment supply and coastal defence data, which then moderates the outputs of the UPSM. Asset data for dwellings, key assets, transport infrastructure, historic assets, and natural assets were used along with the UPSM and CESM to assess their degree of exposure to coastal erosion. A Coastal Erosion Vulnerability Model (CEVM) was produced using Experian Mosaic Scotland (a geodemographic classification which identifies 44 different social groups within Scotland) to classify populations based upon 11 vulnerability variables. Dwellings were assigned a CESM and CEVM score in order to establish their coastal erosion risk. This research demonstrated that the issue of coastal erosion will impact on a relatively low number of properties compared to those impacted by flooding (both coastal and fluvial) as many dwellings are already protected by coastal defences. There is therefore, a considerable future liability, and great pressure for coastal defences to be maintained and upgraded in their current form. The use of the CEVM is a novel inclusion within a coastal erosion assessment for Scotland. Use of the CEVM established that coastal erosion risk is not distributed equally amongst the Scottish coastal population and highlighted that risk can be reduced by either reducing exposure or reducing vulnerability. Thus far in Scotland, reducing exposure has been the primary management approach, which has a number of implications with regards social justice. This research identified the existing data gaps that should be addressed by future research in order to further improve coastal management in Scotland. Future research should focus on assessing historical coastal change rates on a national scale, improve modelling of national scale wave exposure, enhance the information held about current coastal defences and, determine the direct and indirect economic cost associated with the loss of different asset types. It is also necessary to clarify the social justice implications of using adaptation approaches to manage coastal erosion as well as establishing a method to communicate the susceptibility, exposure, vulnerability and risk aspects whilst minimising the potential negative impacts (e.g. property blight) of releasing such information.

Changing use and hydromorphological adjustment in a coastal lagoon–estuarine system, the Ria de Aveiro, Portugal

Today the Ria de Aveiro of northern Portugal has a hydromorphological regime in which river influence is limited to periods of flood. For most of the annual cycle, tidal currents and wind waves are the major forcing agents in this complex coastal lagoon–estuarine system. The system has evolved over two centuries from one that was naturally fluvially dominant to one that is today tidally dominant. Human influence was a trigger for these changes, starting in 1808 when its natural evolution was halted by the construction of a new inlet/outlet channel through the mobile sand spit that isolates it from the Atlantic Ocean. In consequence, tidal ranges in the lagoon increased rapidly from ~0.1 m to >1 m and continued to increase, as a result of continued engineering works and dredging, today reaching ~3 m on spring tides. Hydromorphological adjustments that have taken place include the deepening of channels, an increase in the area of inter-tidal flats, regression of salt marsh, increased tidal propagation and increased saline intrusion. Loss of once abundant submerged aquatic vegetation (SAV), due to increased tidal flows, exacerbated by increased recreational activities, has been accompanied by a change from fine cohesive sediments to coarser, mobile sediments with reduced biological activity.

Sedimentary evidence for a mid-Holocene iceberg-generated tsunami in a coastal lake, west Greenland

We report sedimentological evidence for a tsunami from a coastal lake at Innaarsuit, Disko Bugt (west Greenland), which was most likely generated by a rolling iceberg. The tsunami invaded the lake c. 6000 years ago, during a period of time when relative sea level (RSL) was falling quickly because of isostatic rebound. We use the background rate of RSL fall, together with an age model for the sediment sequence, to infer a minimum wave run-up during the event of c. 3.3 m. The stratigraphic signature of the event bears similarities to that described from studies of the early-Holocene Storegga slide tsunami in Norwegian coastal basins. Conditions conducive to iceberg tsunami include a supply of icebergs, deep water close to the shore, a depositional setting protected from storms or landslide tsunami, and a coastal configuration that has the potential to amplify the height of tsunami waves as water depths shallow and the waves approach and impact the coast. Future warming of polar regions will lead to increased calving and iceberg production, at a time when human use of polar coasts will also grow. We predict, therefore, that iceberg-generated tsunami will become a growing hazard in polar coastal waters, especially in areas adjacent to large, fast-flowing, marine-terminating ice streams that are close to human populations or infrastructure.

Evidencing the Impact of Coastal Contaminated Sediments on Mussels Through Pb Stable Isotopes Composition

Heavily contaminated sediments are a serious concern for ecosystem quality, especially in coastal areas, where vulnerability is high due to intense anthropogenic pressure. Surface sediments (54 stations), 50 cm interface cores (five specific stations), river particles, coal and bulk Pb plate from past French Navy activities, seawater and mussels were collected in Toulon Bay (NW Mediterranean Sea). Lead content and Pb stable isotope composition have evidenced the direct impact of sediment pollution stock on both the water column quality and the living organisms, through the specific Pb isotopic signature in these considered compartments. The history of pollution events including past and present contaminant dispersion in Toulon Bay were also demonstrated by historical records of Pb content and Pb isotope ratios in sediment profiles. The sediment resuspension events, as simulated by batch experiments, could be a major factor contributing to the high Pb mobility in the considered ecosystem. A survey of Pb concentrations in surface seawater at 40 stations has revealed poor seawater quality, affecting both the dissolved fraction and suspended particles and points to marina/harbors as additional diffuse sources of dissolved Pb.

Restoration ecology of coastal lagoons: new methods for the prediction of ecological trajectories and economic valuation

Conservation of the seven lagoons of the Palavas complex (southern France) has been severely impaired by nutrient over-enrichment during at least four decades. The effluents of the Montpellier wastewater treatment plant (WWTP) represented the main nutrient input. To improve the water quality of these lagoons, this WWTP was renovated and upgraded and, since the end of 2005, its effluents have been discharged 11 km offshore into the Mediterranean (total investment €150 M). Possibilities of ecosystem restoration as part of a conservation programme were explored by a focus group of experts. Their tasks were: (i) to evaluate the impact of the reduction of the nutrient input; (ii) if necessary, to design additional measures for an active restoration programme; and (iii) to predict ecosystem trajectories for the different cases. Extension of Magnoliophyta meadows can be taken as a proxy for ecosystem restoration as they favour the increase of several fish (seahorse) and bird (ducks, swans, herons) species, albeit they represent a trade-off for greater flamingos. Additional measures for active ecosystem restoration were only recommended for the most impaired lagoon Méjean, while the least impaired lagoon Ingril is already on a trajectory of spontaneous recovery. A multiple contingent valuation considering four different management options for the Méjean lagoon was used in a pilot study based on face-to-face interviews with 159 respondents. Three levels of ecosystem restoration were expressed in terms of recovery of Magnoliophyta meadows, including their impact on emblematic fish and avifauna. These were combined with different options for access (status quo, increasing access, increasing access with measures to reduce disturbance). The results show a willingness of local populations to pay per year about €25 for the highest level of ecological restoration, while they were only willing to allocate about €5 for additional footpaths and hides.

Estimation of mercury background values in sediment and biota of the Bijagós archipelago, Guinea-Bissau

This work evaluates the mercury (Hg) contamination status (sediments and biota) of the Bijagós archipelago, off the coast of Guinea-Bissau. Sediments exhibited very low concentrations (<1-12ngg(-1)), pointing to negligible sources of anthropogenic Hg in the region. Nevertheless, Hg is well correlated to the fine fraction, aluminium, and loss on ignition, indicating the effect of grain size and organic matter content on the presence of Hg in sediments. Mercury in the bivalves Tagelus adansoni and Senilia senilis did not vary considerably among sites, ranging within narrow intervals (0.09-0.12 and 0.12-0.14μgg(-1) (dry weight), respectively). Divergent substrate preferences/feeding tactics may justify slight differences between species. The value 11ngg(-1) is proposed as the sediment background concentration for this West-African coastal region, and concentrations within the interval 8-10ngg(-1) (wet weight) may be considered as reference range for S. senilis and T. adansoni in future monitoring studies.

The impact of tides and waves on near-surface suspended sediment concentrations in the English Channel

Numerous ecological problems of continental shelf ecosystems require a refined knowledge of the evolution of suspended sediment concentrations (SSC). The present investigation focuses on the spatial and temporal variabilities of near-surface SSC in coastal waters of the English Channel (western Europe) by exploiting numerical predictions from the Regional Ocean Modeling System ROMS. Extending previous investigations of ROMS performances in the Channel, this analysis refines, with increased spatial and temporal resolutions, the characterization of near-surface SSC patterns revealing areas where concentrations are highly correlated with evolutions of tides and waves. Significant tidal modulations of near-surface concentrations are thus found in the eastern English Channel and the French Dover Strait while a pronounced influence of waves is exhibited in the Channel Islands Gulf. Coastal waters present furthermore strong SSC temporal variations, particularly noticeable during storm events of autumn and winter, with maximum near-surface concentrations exceeding 40 mg l−1 and increase by a factor from 10 to 18 in comparison with time-averaged concentrations. This temporal variability strongly depends on the granulometric distribution of suspended sediments characterized by local bi-modal contributions of silts and sands off coastal irregularities of the Isle of Wight, the Cotentin Peninsula and the southern Dover Strait.