Southampton Water Research Articles

Transgenerational effects influence acclimation to varying temperatures in Aurelia aurita polyps (Cnidaria: Scyphozoa)

Temperature is one of the most important drivers to affect marine ectotherms in the context of anthropogenic climate change modifying seasonal cycles in temperate regions. To reliably predict the impact of climate variability on marine ectotherms, their capacity to adapt to rapid change needs to be understood. Due to fast transmission between generations, transgenerational effects may enable populations to moderate stressors. We examined reproduction across three temperature scenarios and three generations of asexual Aurelia aurita polyps: transgenerational warming, transgenerational cooling, and stable temperatures. Polyps were incubated at three temperatures (15, 17, 19°C) encountered in summertime in Southampton Water. In the first two polyps generations, temperature remained the main driver of polyp reproduction. However, in the third generation parental and grandparental temperature influenced offspring production. These effects appeared most strongly in cooling scenarios: polyps who experienced rapid cooling between generations displayed an immediate drop in reproductive output as opposed to polyps who remained at the same temperature as their parents. Our results highlight that transgenerational effects may require more extreme temperatures or increased numbers of generations to have a measurable impact on a population, highlighting the vulnerability of these organisms to continued climate change.

Temporal variability of phytoplankton biomass and net community production in a macrotidal temperate estuary

Coastal zones play a significant role in Earth's biogeochemical processes. Within these regions, estuaries are particularly important due to their complex ecological interactions and spatial and temporal variability. The aim of this study was to apply a year long high-frequency (15 min) environmental data time series to identify both the timing and factors influencing phytoplankton blooms in the Southampton Water estuary. Dissolved oxygen measurements from an in situ deployed optode were applied to the open diel oxygen method to estimate daily integrated rates of gross primary production (GPP), ecosystem respiration (ER) and net community production (NCP). Additional water quality data including temperature, salinity, chlorophyll concentration and turbidity allowed the relationship between physical and biological processes occurring over different time scales to be investigated. The occurrence of major phytoplankton blooms during the spring-summer period were associated with critical values of estuarine water temperature and mean water column irradiance. In addition, neap tides were found to promote the initiation of phytoplankton blooms in late spring and summer months. Annual daily average NCP for the estuarine ecosystem presented an estimated net heterotrophic state (−0.8 mmol O2 m−2 d−1), although seasonal productivity events shifted this state for several days and sometimes weeks to net autotrophic conditions. The results of this study have demonstrated how high frequency in situ dissolved oxygen measurements from an optode can make a valuable contribution to understanding the key factors influencing bloom events in a temperate macrotidal estuary. This approach if applied more widely to other coastal sites could therefore contribute to consolidating global annual primary production budgets for coastal regions.

Environmental risk of trace metals and metalloids in estuarine sediments: An example from Southampton Water, U.K.

Industrial and commercial port activities are widely recognized worldwide as an important source of pollution to proximal estuaries. In this study, we analysed geochemical and sedimentological parameters including major and trace elements, organic matter and sediment texture in surface sediments from the estuarine environment of Southampton Water, U.K. Using these data, and multivariate statistical tools [correlation, factor and cluster analysis and pollution indices such as Enrichment Factor (EF), Pollution Load Index (PLI) and the Adverse Effect Index (AEI)], we examine sedimentary trace metal and metalloid contamination, contamination sources, and potential biological impacts of the contamination present. The geochemical data, multivariate statistical analysis and pollution indices indicate that the spatial distribution of trace metals and metalloids is influenced by both sediment composition (and mixing) and anthropogenic activities. Most trace metal and metalloid concentrations are close to local geological background levels, except for Cu, Zn and Pb. The spatial distribution of these elements indicates that the Exxon oil refinery, Southampton port, local marinas and runoff from domestic and industrial activities act effectively as point sources of these elements. Pollution indices calculations highlight a degraded environment as a result of these pollutants, and further work is needed to assess the current impact of trace metals and metalloids on local ecology.

Bronze Age Funerary and Later Prehistoric Activity at Badminston Farm, Fawley, Hampshire

Archaeological excavations were undertaken by Southern Archaeological Services Ltd. between 1999 and 2010 at Badminston Farm, Fawley, on the eastern edge of the New Forest, adjacent to Southampton Water. The excavations identified evidence of near- continuous human activity from the early prehistoric period to the present day. Mesolithic activity was followed by Early Bronze Age pits, containing 'placed' flint assemblages. Evidence of Bronze Age funerary activity included deflated barrows/ring ditches, and associated cremations. Late Bronze Age ceramics were absent but a hoard of 68 Armorican-type socketed axes may have been a votive offering marking the 'ancestral' barrow which would have been visible here. Other Bronze Age evidence included two burnt mounds and an ill-defined structure possibly associated with weaving. Iron Age activity was represented by a number of pits containing domestic pottery, while Late Iron Age and Romano-British ditches may have formed part of an enclosure. A significant assemblage of non-local worked stone attests to long distance exchange, and the possibility of a nearby farmstead. Medieval activity was represented by pits, ditches and stakeholes, with some evidence of an enclosure or structure associated with grain drying. Later land divisions and a WWII radio communication station dominated more recent use of the site.

An assessment of the feasibility of using skirt containment boom together with paravanes for offshore response

Abstract The use of conventional offshore containment boom is a recognised way of containing and recovering oil spilt at sea. However, there are various operational and logistical challenges with their use. One of the largest being that their containment becomes ineffective when towed through the water at speeds of greater than 0.75 knots. Containment and collection of oil using high speed systems allows for greater tow speeds (2–3 knots) without failure and can be operated with a paravane as a single ship system. Oil Spill Response Limited (OSRL) have had numerous requests from its members to supply offshore containment and recovery systems suitable for a single vessel deployment. The reason for this was to help with the challenges of low availability of vessels suitable for offshore operations and to reduce high costs. OSRL have used manufacturers guidance to advise its members on the best options however wished to have its own data to further support this guidance and provide user-validated recommendations to its members. OSRL have investigated the viability of using a paravane with a conventional offshore boom using field tests. These tests focused on vessel tow speed, current speed, boom containment effectiveness and encounter area. A number of deployments were carried out using conventional inflation boom and a medium sized paravane in Southampton Water, UK in 2018 (Figure 1). Observations were gathered to identify the point of boom failure when towed at different speeds and whether a suitable encounter area could be achieved. This poster will provide the detail on the feasibility of towing a conventional offshore boom with a single vessel and paravane, see boom configuration in Figure 2. It will outline specifications and parameters which make for a successful / unsuccessful deployment of conventional boom with paravane and provide recommendations for Tier 1 single vessel deployment equipment.

Identification of tidal trapping of microplastics in a temperate salt marsh system using sea surface microlayer sampling

Microplastics are contaminants of increasing global environmental concern. Estuaries are a major transport pathway for land-derived plastics to the open ocean but are relatively understudied compared to coastal and open marine environments. The role of the “estuarine filter”, by which the supply of sediments and contaminants to the sea is moderated by processes including vegetative trapping and particle flocculation, remains poorly defined for microplastics land to sea transfer. Here, we focus on the sea surface microlayer (SML) as a vector for microplastics, and use SML sampling to assess microplastic trapping in a temperate marsh system in Southampton Water, UK. The SML is known to concentrate microplastics relative to the underlying water and is the first part of rising tidal waters to traverse intertidal and upper tidal surfaces. Sampling a salt marsh creek at high temporal resolution allowed assessment of microplastics in-wash and outflow from the salt marsh, and its relationship with tidal state and bulk suspended sediment concentrations (SSC), over spring and neap tides. A statistically significant decrease in microplastics abundance from the flood tide to the ebb tide was found, and a weak positive relationship with SSC observed.

An investigation of trace metals and oil contamination in Southampton Water sediments: the distribution and influence on organisms

An investigation was conducted on 21st April 2012 in Southampton Water sediment, with the aim of detecting the contaminants distribution and the influence on the living organisms. Among the sampling sites, station 3 and 4 are most close to Fawley oil refinery, where contaminants with respect to trace metals, Cu and Zn, and oil are observed with highest concentrations. Metals contained in the sediments are in forms of weakly bounded compounds, such as carbonates and oxides, or strongly bounded complex, including organic metals and sulphide. High values of organic matter concentration in sediment at station 3 agree with the oil release from Fawley. Chlorophyll a concentrations are lowest at station 4, corresponding to the high pollution around.

Spatial Variation in Water Column Structure, Nutrients, Chlorophyll and Zooplankton in an Estuarine Transect of Southampton Water

Estuary systems are complicated and closely related to humans. The understanding of estuary systems is important to scientific study and human develop. An investigation was conducted on 3rd November 2009 by RV Callista along the Itchen estuary of Southampton Water with the aim of determining spatial variability in physical water column structure, nutrients, chlorophyll and zooplankton of Southampton Water, and recognizing the links between them. The salinity and temperature values are relatively lower at surface upper estuary than that of deep lower estuary. Water stratification is observed around upper and mid estuary. The nutrient Si exhibits conservative behaviour with a linear relationship with salinity gradient, while P shows non-linear with salinity, which may indicate an addition bahaviour. Chlorophyll distributes high concentration at surface upper estuary and relatively uniform and low concentration at downriver area which is mainly due to light and nutrients factors. Water turbidity affects chlorophyll distribution by reducing light availability in the water column, while chlorophyll can in turn influence water turbidity. The abundance dominant species of the estuary are Copepoda and Appendicularia. The mid estuary has the highest zooplankton abundance, while the lower estuary has the most zooplankton groups. Zooplankton distribution is relative to food distribution, temperature, light and salinity profiles.

The Fate of Contaminants and Stable Pb Isotopes in a Changing Estuarine Environment: 20 Years On.

Estuarine sediments provide an important sink for contaminants discharged into fluvial, estuarine, and nearshore settings, and numerous authors have utilized this trapping function to assess historical contaminant loadings and contaminant breakdown/transformation processes. This Article examines the retention of elemental and isotopic sedimentary signatures in an industrialized estuarine system subject to a strongly upward sea-level trend, over a 20 year period. Two contrasting saltmarsh sites (at Hythe and Hamble, part of the wider Southampton Water estuarine system, UK) were examined, which had been previously cored and analyzed in the early 1990s. Much of the geochemical record of recent anthropogenic activity has been eroded and lost at the Hamble site. In contrast, radiometric, isotopic and elemental records of anthropogenic activity have been retained in the Hythe marsh, with 137Cs and Cu depth profiles showing retention of input maxima related to fallout and local industrial discharges, respectively. Stable Pb isotope data show a broad degree of correspondence in cores analyzed in 1994 and 2014 when plotted against sediment (radiometric) age, indicating the usefulness of isotopic data in retaining information on Pb sources and in disentangling Pb input histories. New ultrahigh precision, double-spike mass spectrometry stable Pb isotope data allow clearer discrimination of historical Pb input phases, and highlight within-estuary mixing and supply of reworked, secondary contamination from erosion of anthropogenically labeled sediments elsewhere in the estuary.

A Lab-On-Chip Phosphate Analyzer for Long-term In Situ Monitoring at Fixed Observatories: Optimization and Performance Evaluation in Estuarine and Oligotrophic Coastal Waters

The development of phosphate sensors suitable for long-term in situ deployments in natural waters, is essential to improve our understanding of the distribution, fluxes and biogeochemical role of this key nutrient in a changing ocean. Here, we describe the optimization of the molybdenum blue method for in situ work using a lab-on-chip analyzer and evaluate its performance in the laboratory and at two contrasting field sites. The in situ performance of the LOC sensor is evaluated using hourly time-series data from a 56-day trial in Southampton Water (UK), as well as a month-long deployment in the subtropical oligotrophic waters of Kaneohe Bay (Hawaii, USA). In Kaneohe Bay, where phosphate concentrations were characteristic of the dry season (0.13 ± 0.03 M, n=704), the in situ sensor accuracy was 16 ± 12 % and a potential diurnal cycle in phosphate concentrations was observed. In Southampton Water, the sensor data (1.02 ± 0.40 µM, n=1267) were accurate to ± 0.10 µM relative to discrete reference samples. Hourly in situ monitoring revealed striking tidal and storm derived fluctuations in phosphate concentrations in Southampton Water that would not have been captured via discrete sampling. We show the impact of storms on phosphate concentrations in Southampton Water is modulated by the spring-neap tidal cycle and that the tenfold decline in phosphate concentrations observed during the later stages of the deployment was consistent with the timing of a spring phytoplankton bloom in the English Channel. Under controlled laboratory conditions in a 250 L tank, the sensor demonstrated an accuracy and precision better than 10 % irrespective of the salinity (0-30), turbidity (0-100 NTU), dissolved organic carbon concentration (0-10 mg/L) and temperature (5-20C) of the water (0.3-13 M phosphate) being analyzed. This work demonstrates that the LOC technology is mature enough to quantify the influence of stochastic events on nutrient budgets and to elucidate the role of phosphate in regulating phytoplankton productivity and community composition in estuarine and coastal regimes.

A Saxon Fish Weir and Undated Fish Trap Frames Near Ashlett Creek, Hampshire, UK: Static Structures on a Dynamic Foreshore

The remains of a wooden V-shaped fish weir and associated structures have been discovered near Ashlett Creek on the tidal mudflats of Southampton Water in Hampshire, southern Britain. Radiocarbon dating of oak roundwood stakes taken from the main weir structure date it to the middle Saxon period. Clusters of as-yet undated roundwood posts within the catchment area of the weir are interpreted as the frames for fish traps that are assumed to pre- or post-date the operational period of the weir itself. The weir is contemporary with wooden V-shaped fish weirs found elsewhere in southern and central Britain, and also Ireland, but its circular catchment ‘pound’ remains restricted, in these islands, to the Solent and Severn estuaries: it has a close parallel with another Saxon-era weir on the nearby Isle of Wight. It also shows striking structural similarities with examples in use today in Basse Normandy, on the southern shore of the English Channel. The paper discusses the function and operation of the weir, and places it in its social and historical context. Regressive cartography demonstrates that the structures have become exposed as a result of saltmarsh retreat in this area of Southampton Water since the nineteenth century. The radiocarbon dates returned for the posts demonstrate that this transgression of the marsh must have been preceded by a prolonged period of progradation, which covered and preserved the site; its subsequent re-exposure has negative implications for its survival.

Persistence, dispersal and genetic evolution of recently formed Spartina homoploid hybrids and allopolyploids in Southern England

In Southampton Water, UK, the recent (c. 150 years ago) interspecific hybridisation between Spartina alterniflora (2n = 6x = 62; A-genome) and S. maritima (2n = 6x = 60; M-genome) gave rise to the homoploid hybrid (S. × townsendii, 2n = 6x = 62), and subsequently to the invasive allododecaploid species S. anglica (2n = 12x = 120–124) that has since spread worldwide. To address the question of dynamics of mixed ploidy populations involving these plants, we analysed several Spartina populations (fifty one individuals) in Southern England, UK, one of which was the presumed place of origin of the homoploid hybrid (Hythe). Using a combination of flow cytometry and ribosomal DNA (rDNA) genotyping we were able to identify the genomic composition and ploidy level of each individual analysed. The data show that the homoploid hybrid still dominates the population at Hythe (82 % of individuals collected in that locality) since its origin in the nineteenth century. We also identified S. × townsendii for the first time on Hayling Island (66 % individuals), indicating dispersal beyond its likely origin. The fertile allododecaploid S. anglica was mainly found in populations outside the initial hybridisation site, on Hayling Island and at Eling Marchwood. Quantification of the rDNA contributions from each parental genome showed that the ratios were mostly balanced in S. × townsendii. However, two (3 %) S. anglica individuals analysed have lost nearly all M-genome homeologs, indicating extensive repeat loss. Such variation indicates that despite the presumed single allopolyploid origin of S. anglica and genetic uniformity at other loci, it has undergone substantial changes at the rDNA loci following genome duplication.

Effects of organism preparation in metallothionein and metal analysis in marine invertebrates for biomonitoring marine pollution

Metallothionein (MT) is established as a potentially useful biomarker for monitoring aquatic pollution. This paper addresses widespread inconsistencies in storage conditions, tissue type selection and pre-treatment of samples before MT and metal analysis in biomarker studies. This variation hampers comparability and so the widespread implementation of this monitoring approach. Actively sampled Mytilus edulis in Southampton Water, UK were exposed to different storage temperatures, a variety of tissue types were analysed, and various pre-treatments of transportation on ice, transportation in seawater, depuration, and rapid dissection in the field were examined. Storage temperatures of −20°C were found to be adequate for periods of at least ten weeks, as MT was not reduced by protein degradation compared with samples kept at −80°C. Whole tissue and digestive gland concentrations of MT and metals were significantly positively correlated and directly relatable. MT in the digestive gland appeared to be more responsive to metals than in whole tissue, where it may be diluted, masking MT responses. However, longer study periods may suffer the effects of mass changes to the digestive gland, which alters MT concentration, and it may therefore be advisable to measure whole tissue. Depuration and transportation in seawater reduced both MT and metal concentrations in the digestive gland, and few correlations between MT and metals were identified for these treatments. It is therefore recommended that: i) samples are transported to the laboratory on ice and dissected as soon as possible thereafter, ii) depuration should not be used when examining MT response to metal exposure until further research clarifying its utility is reported, iii) either whole tissue or the digestive gland can be used to measure MT, though whole tissue may be preferable on long-term studies, and iv) organisms can be stored at −20°C before analysis for up to ten weeks. These practices can be applied to future biomonitoring studies and will improve the comparability and repeatability of using MT as a biomarker.

Recovery from TBT pollution in English Channel environments: A problem solved?

Following recognition of effects in the 1980s, tributyltin (TBT) has been monitored at sites in the English Channel to evaluate the prognosis for biota – spanning the introduction of restrictions on TBT use on small boats and the recent phase-out on the global fleet. We describe how persistence and impact of TBT in clams Scrobicularia plana has changed during this period in Southampton Water and Poole Harbour. TBT contamination (and loss) in water, sediment and clams reflects the abundance and type of vessel activity: half-times in sediment (up to 8y in Poole, 33y in Southampton) are longest near commercial shipping. Recovery of clam populations – slowest in TBT-contaminated deposits – provides a useful biological measure of legislative efficacy in estuaries. On rocky shores, recovery from imposex in Nucella lapillus is evident at many sites but, near ports, is prolonged by shipping impacts, including sediment legacy, for example, in the Fal.

Lab-on-Chip Measurement of Nitrate and Nitrite for In Situ Analysis of Natural Waters

Microfluidic technology permits the miniaturization of chemical analytical methods that are traditionally undertaken using benchtop equipment in the laboratory environment. When applied to environmental monitoring, these "lab-on-chip" systems could allow high-performance chemical analysis methods to be performed in situ over distributed sensor networks with large numbers of measurement nodes. Here we present the first of a new generation of microfluidic chemical analysis systems with sufficient analytical performance and robustness for deployment in natural waters. The system detects nitrate and nitrite (up to 350 μM, 21.7 mg/L as NO(3)(-)) with a limit of detection (LOD) of 0.025 μM for nitrate (0.0016 mg/L as NO(3)(-)) and 0.02 μM for nitrite (0.00092 mg/L as NO(2)(-)). This performance is suitable for almost all natural waters (apart from the oligotrophic open ocean), and the device was deployed in an estuarine environment (Southampton Water) to monitor nitrate+nitrite concentrations in waters of varying salinity. The system was able to track changes in the nitrate-salinity relationship of estuarine waters due to increased river flow after a period of high rainfall. Laboratory characterization and deployment data are presented, demonstrating the ability of the system to acquire data with high temporal resolution.

Modelling of tide and surge elevations in the Solent and surrounding waters: The importance of tide–surge interactions

A regional two-dimensional hydrodynamic model using the MIKE-21 software and data from a pre-operational forecasting system of the English Channel is described and applied to the Solent–Southampton Water estuarine system. The regional model was able to predict surge heights with a root mean squared error (RMSE) accuracy of 0.09 m during a three month hindcast in the winter of 2009, comparing closely with accuracy assessments from other independent systems. However, consistent underprediction of tidal harmonic constituent amplitudes was present throughout the region leading to errors in the prediction of the total water level elevations. Despite the complex nature of the Solent tidal regime, interpolation of tidal elevations from harmonic analysis at fixed tide gauge locations was shown to be effective in reducing this uncertainty at gauged and un-gauged sites. The degree to which tide–surge interactions were taking place was examined. Of particular interest was the quantification of the sensitivity of the predicted surge to the levels of uncertainty expected in the prediction of the tide within a complex nearshore region such as the Solent. The tide–surge interaction during three surge events was shown to be greatest in the Western Solent and Southampton Waters regions, where the tidal uncertainty was greatest. Interaction between the tide and surge resulted in a change of up to 0.3 m (11%) in the predicted total peak water level when the surge was added to the harmonic analysis-based tidal prediction. Despite the significant effect of removing the tide–surge interactions, tests indicated that the error in tidal range expected in the regional models tidal prediction altered the prediction of the surge only enough to induce changes in peak total water elevations by up to 0.03 m during an event on 10th March 2008. The findings suggest that the current tidal predictions in complex estuarine systems, such as the Solent, are of high enough quality to reproduce the majority of the tide–surge interactions taking place and that the error in the surge due to uncertainties in the predicted tide are expected to be relatively small.

Evaluation of DGT techniques for measuring inorganic uranium species in natural waters: Interferences, deployment time and speciation

Three adsorbents (Chelex-100, manganese dioxide [MnO2] and Metsorb), used as binding layers with the diffusive gradient in thin film (DGT) technique, were evaluated for the measurement of inorganic uranium species in synthetic and natural waters. Uranium (U) was found to be quantitatively accumulated in solution (10–100μgL−1) by all three adsorbents (uptake efficiencies of 80–99%) with elution efficiencies of 80% (Chelex-100), 84% (MnO2) and 83% (Metsorb). Consistent uptake occurred over pH (5–9), with only MnO2 affected by pH<5, and ionic strength (0.001–1molL−1 NaNO3) ranges typical of natural waters, including seawater. DGT validation experiments (5 days) gave linear mass uptake over time (R2≥0.97) for all three adsorbents in low ionic strength solution (0.01M NaNO3). Validation experiments in artificial sea water gave linear mass uptake for Metsorb (R2≥0.9954) up to 12h and MnO2 (R2≥0.9259) up to 24h. Chelex-100 demonstrated no linear mass uptake in artificial sea water after 8h. Possible interferences were investigated with SO42− (0.02–200mgL−1) having little affect on any of the three DGT binding layers. PO43− additions (5μgL−1–5mgL−1) interfered by forming anionic uranyl phosphate complexes that Chelex-100 was unable to accumulate, or by directly competing with the uranyl species for binding sites, as with MnO2 and the Metsorb. HCO3− (0.1–500mgL−1) additions formed anionic species which interfered with the performance of the Chelex-100 and the MnO2, and the Ca2+ (0.1–500mgL−1) had the affect of forming labile calcium uranyl species which aided uptake of U by all three resins. DGT field deployments in sea water (Southampton Water, UK) gave a linear mass uptake of U over time with Metsorb and MnO2 (4 days). Field deployments in fresh water (River Lambourn, UK) gave linear uptake for up to 7 and 4 days for Metsorb and MnO2 respectively. Field deployment of the Metsorb-DGT samplers with various diffusive layer thicknesses (0.015–0.175cm) allowed accurate measurements of the diffusive boundary layer (DBL) and allowed DBL corrected concentrations to be determined. This DBL-corrected U concentration was half that determined when the effect of the DBL was not considered. The ability of the DGT devices to measure U isotopic ratios with no isotopic fractionation was shown by all three resins, thereby proving the usefulness of the technique for environmental monitoring purposes.

First account on the seasonal occurrence of parasitic forms on the zooplankton of Southampton Water

In the past half century, a number of studies have described the general composition of the mesozooplankton of Southampton Water, but little attention has been paid to the occurrence of parasitic and commensal species. In order to fill this gap, the occurrence and distribution of parasitic/commensal species was investigated in three fixed stations along the estuary in 2001/2002. A total of 16 parasitic taxa were identified, including 11 new records for the zooplankton of Southampton Water. The most frequent and abundant parasitic taxa observed in the estuary were Peltogaster paguri, Sacculina carcini, Siphonostomatoida copepodites and cryptonistic forms of isopods. This study is the first report on ‘free-forms’ of parasitic/commensal species within the mesozooplankton of Southampton Water being also a reasonable indicator of the presence of the infected/associate host in the estuary or surrounding areas.

Estuary schematisation in behaviour-oriented modelling

ASMITA (Aggregated Scale Morphological Interaction between Tidal basin and the Adjacent coast) is a behaviour-oriented modelling approach which represents estuarine systems schematically. It was originally developed for ‘classic’ tidal inlets such as those found in the Dutch Wadden Sea and Venice lagoons, where schematisations of two or three interacting elements (e.g. flat, channel and possibly an ebb-tidal delta) are appropriate. However, estuaries show a much wider range of form and human interference than these cases. This paper presents results for two UK estuaries with differing morphologies and management histories. The Ribble Estuary and Southampton Water are poorly represented by standard two and three element schematisations, and required novel schematisations which considered the dominant processes shaping the two estuaries. The new schematisations gave model predictions that (1) are better than the baseline assumption of no change through time, (2) are better than standard schematisations and (3) are physically reasonably whilst retaining simplicity. These results demonstrate a possible generic methodology to test different schematisations using simple models to characterise estuarine morphodynamics as a preliminary stage of estuary assessment.

THE SIGNIFICANCE OF WAVE REFLECTION ON THE MORPHOLOGY OF INTERTIDAL MUDFLATS

The influence of seawalls in modifying the equilibrium form of a shoreline has previously caused extensive debate. A numerical model was used to predict the equilibrium form of muddy intertidal profiles, along a shoreline in Southampton Water, UK. It was found that the profile containing a seawall had a very different profile form to the undefended sites, and that this seawall profile could not be accurately represented in the model. The model was extended to include wave reflection from the seawall, producing a new prediction with a much improved resemblance of the observed profile. It was concluded that the likely cause of the different profile form at the site of the seawall in this case, is due incident and reflected wave interaction.