Natural Beds Research Articles

Large-scale simulations of Floquet physics on near-term quantum computers

Periodically driven quantum systems exhibit a diverse set of phenomena but are more challenging to simulate than their equilibrium counterparts. Here, we introduce the Quantum High-Frequency Floquet Simulation (QHiFFS) algorithm as a method to simulate fast-driven quantum systems on quantum hardware. Central to QHiFFS is the concept of a kick operator which transforms the system into a basis where the dynamics is governed by a time-independent effective Hamiltonian. This allows prior methods for time-independent simulation to be lifted to simulate Floquet systems. We use the periodically driven biaxial next-nearest neighbor Ising (BNNNI) model, a natural test bed for quantum frustrated magnetism and criticality, as a case study to illustrate our algorithm. We implemented a 20-qubit simulation of the driven two-dimensional BNNNI model on Quantinuum’s trapped ion quantum computer. Our error analysis shows that QHiFFS exhibits not only a cubic advantage in driving frequency ω but also a linear advantage in simulation time t compared to Trotterization.

Suspended culture of the Manabí oyster Crassostrea cf. corteziensis in a tropical estuary

Grow-out of the Manabí oyster (Crassostrea cf. corteziensis) under suspended culture conditions from the Chone River Estuary (Manabí, Ecuador) was evaluated. The culture was established in lanterns with 50 oysters/floor for seven months (July 2022 to February 2023) using juveniles (34.9±6.2 mm) collected from natural oyster beds in the same estuary. The growth and survival, as well as environmental variables in the culture site, were monitored. The growth in the shell dimension was continuous, reaching high rates during October and November. At the end of the study, 86.7±6.68 mm anteroposterior length, 110.7±19.04 g dry mass of the whole organism (with 3.7±0.67 g soft tissue), and survival of 92.6±2.62 % were obtained. No association was observed between the patterns of the growth curves and those of the environmental parameters; however, the decrease of body mass (during February 2023) was associated with increased temperature, decreased salinity, and lower phytoplankton content. Oysters of marketable size (80 mm) were obtained after seven months of culture. The results suggest the biological feasibility of cultivating the Manabí oyster C. cf. corteziensis in the Chone River Estuary, which could be an emerging species for aquaculture in Ecuador and the tropical American Pacific.

The queen scallop Aequipecten opercularis: A slow domoic acid depurator?

Domoic acid (DA) is a dangerous phycotoxin produced by several strains of diatoms of the genus Pseudo-nitzschia, and responsible for Amnesic Shellfish Poisoning (ASP) in humans. The increasingly intense ASP-outbreaks along the English Channel over the last three decades have forced persistent harvest closures of economically important and highly contaminated bivalve stocks exhibiting slow DA-depuration rates, like the king scallop Pecten maximus. Under this scenario, other pectinid species, such as the queen scallop Aequipecten opercularis have been empirically proposed as alternative resources to redress the high economic losses due to the banning of the exploitation of P. maximus. Nevertheless, the kinetics of DA depuration in A. opercularis have not been assessed so far, and its direct extraction after ASP-episodes could represent a serious threat to public health. Hence, the main objective of this work was to estimate the DA-depuration rate in the digestive gland (DG) of naturally contaminated scallops A. opercularis after a toxic Pseudo-nitzschia australis bloom subjected to experimental depuration in the laboratory for 30 days. This study also intended to go further in the knowledge about the anatomical distribution of DA in scallop tissues, and corroborate the implications of autophagy in DA-sequestration in the DG of this species as recently hypothesized. In the DG, the DA-depuration rate (0.018 day−1) suggested that even with toxin burdens as low as 40 mg⋅kg−1 in the DG, queen scallops may remain contaminated for about 70 days, thus longer under intensely contamination scenarios. The subcellular analyses corroborated DA-sequestration mainly through late-autophagy within residual bodies in the DG, without differences in the frequencies of anti-DA labeled residual bodies across the entire depuration process. These results revealed that A. opercularis cannot be considered a fast DA-depurator, and represent a baseline knowledge for decision-making about harvesting natural beds of queen scallops after toxic Pseudo-nitzschia blooms. The findings of this work also represent a cornerstone for further research to accelerate DA-depuration in this species.

Behavioral hotspots of bottlenose dolphins in industrialized ship channels

Anthropogenic activity in coastal areas can damage marine habitats and alter marine mammal behavior and habitat use. Understanding behavioral associations with diverse habitat features in industrialized coastal areas is crucial for marine mammal conservation management. A shore-based digital theodolite was used to assess the behavioral states and habitat use of common bottlenose dolphins (Tursiops truncatus) off Port Aransas, Texas across seasons. The relationship between behavioral states and environmental and geographical variables were analyzed. Behavioral hotspots were identified. Dolphins frequently foraged (46%), indicating the area is an important feeding ground. Dolphins also traveled (25%) and milled (22%), with less frequent occurrences of socializing (6%) and resting (1% of observations). Season, time of day, and distance to shoreline were significant predictors of foraging and traveling behavioral states. Dolphins engaged in all behavioral states closer to seawall shorelines than to mangroves and natural seagrass beds, suggesting that hard shoreline features may influence daily activity patterns. Despite daily anthropogenic operations, bottlenose dolphins use features of the industrialized area (i.e., deeply dredged channels, human-engineered seawalls) to engage in a variety of behaviors. Monitoring of dolphin behavioral states and habitat use in active ship channels are needed to assess changes from baseline data from increasing coastal development and vessel activities.

Experimental investigation on productivity enhancement of conical solar distillers using various sand bed types based on energy, exergy, and exergo-economic analysis

In this study, performance enhancement of conical distillers was investigated with various natural sand bed types. Four sand types with different colors (compositions and concentrations of chemical compounds) were tested and used as thermal storage materials to reduce heat loss, enhance evaporation process, and daily production. Three similar distillers were designed and investigated experimentally under the same climatic parameters over two consecutive days. Performance parameters of the proposed distillers, including yield, energy, exergy, and exergo-economic were analyzed and compared with those of reference distiller and other related studies. Results showed that the highest yield and performance values were achieved by the distiller combined with a golden sand bed. The utilization of golden sand bed achieves a daily production of 7.38 lm−2day−1 with enhancement of 10.31 %, 22.79 %, 35.91 %, and 60.43 % compared with yellow sand, red sand, white sand, and reference distillers, respectively. The daily energy and exergy efficiency of conical distillers combined with golden, yellow, red, and white sand beds 59.59 %, 44.84 %, 30.33 %, and 17.85 % and 143.52 %, 103.44 %, 64.73 %, and 36.39 %, respectively, higher than that of the reference distiller. Integrating golden, yellow, red, and white sand beds with conical distillers reduces the yield price and payback time by 60.43 %, 45.43 %, 30.65 %, and 18.04 %. The annual energy and exergy output of conical distillers combined with golden, yellow, red, and white sand beds were 130.54, 118.47, 106.60, 96.41, and 81.76 kWh/year and 6.08, 5.08, 4.00, 3.31, and 2.49 kWh/year, respectively.

Efficacy of steam and diatomaceous earth dust against the tropical bed bug Cimex hemipterus (F.) under laboratory and field conditions.

Over the past two decades, bed bugs (Cimex spp.) have resurged as common urban pests around the world. The search for efficient and safe control measures has become a key interest among researchers, manufacturers, and pest control professionals. In this study, we evaluated and compared the efficacy of steam, diatomaceous earth (DE) dust, and a combination of both against tropical bed bugs (Cimex hemipterus (F.)) under laboratory and field conditions. In the laboratory study, the mortality of bed bugs after 2 days of exposure to DE dust was 100%. When bed bugs stayed on the surface of an object or in cracks, a brief steam treatment (1 s) caused 100% mortality. However, when bed bugs were hidden under a fabric cover, steam application for 10 s only caused 89 ± 6% mortality. Bed bugs that survived steam treatment exhibited reduced feeding activity. In a 14-week long study, there was no significant difference in the reduction rate of bed bugs between steam treatment and DE dust treatment. A 37-week long control study showed that steam and steam plus DE dust treatments eliminated 97-100% of the infestations. Applying steam and DE dust are effective strategies for eliminating natural tropical bed bug infestations. Continuous follow-up monitoring and treatment until no bed bugs are found are crucial in completely eliminating the infestation of tropical bed bugs. © 2024 Society of Chemical Industry.

Hypoxia in the Blue Mussel Mytilus chilensis Induces a Transcriptome Shift Associated with Endoplasmic Reticulum Stress, Metabolism, and Immune Response.

The increase in hypoxia events, a result of climate change in coastal and fjord ecosystems, impacts the health and survival of mussels. These organisms deploy physiological and molecular responses as an adaptive mechanism to maintain cellular homeostasis under environmental stress. However, the specific effects of hypoxia on mussels of socioeconomic interest, such as Mytilus chilensis, are unknown. Using RNA-seq, we investigated the transcriptomic profiles of the gills, digestive gland, and adductor muscle of M. chilensis under hypoxia (10 days at 2 mg L-1) and reoxygenation (10 days at 6 mg L-1). There were 15,056 differentially expressed transcripts identified in gills, 11,864 in the digestive gland, and 9862 in the adductor muscle. The response varied among tissues, showing chromosomal changes in Chr1, Chr9, and Chr10 during hypoxia. Hypoxia regulated signaling genes in the Toll-like, mTOR, citrate cycle, and apoptosis pathways in gills, indicating metabolic and immunological alterations. These changes suggest that hypoxia induced a metabolic shift in mussels, reducing reliance on aerobic respiration and increasing reliance on anaerobic metabolism. Furthermore, hypoxia appeared to suppress the immune response, potentially increasing disease susceptibility, with negative implications for the mussel culture industry and natural bed populations. This study provides pivotal insights into metabolic and immunological adaptations to hypoxia in M. chilensis, offering candidate genes for adaptive traits.

Herbivores can benefit both plants and their pathogens through selective herbivory on diseased tissue

Abstract Infectious disease can shape community structure, particularly when pathogens affect foundation species. Seagrasses are foundation species that form meadows along coasts worldwide, controlling sediment deposition and biogeochemical cycling while supporting a diverse community of fish and invertebrates. These plants are hosts to wasting diseases that cause necrotic tissue lesions, which could alter seagrass value as food, habitat and mediators of ecosystem processes. However, such biotic interactions and influences on disease dynamics are still not well understood. We investigated whether a common herbivore affected the development of wasting disease on eelgrass. We measured the severity and prevalence of eelgrass wasting disease in a meadow across two summers through repeated field surveys. We assessed the role of the eelgrass herbivore on disease spread and growth using microcosm and mesocosm experiments. We further explored herbivore feeding preferences in a choice trial, which was paired with chemical analysis of plant tissue and analysed using a structural equation model. While the herbivore facilitates the growth of new disease lesions among isolated leaves, on balance they reduce lesion severity by more than 50% in comparison with no‐herbivore controls in field‐realistic settings. This was likely because the herbivore strongly prefers to eat diseased rather than healthy tissue, consuming nearly twice as much lesion area in choice trials. This preference arises from pathogen‐driven changes in the host plant; lesioned tissue requires less force to penetrate than non‐lesioned tissue. Additionally, as lesions increase in size, their polyphenolic concentrations drop, which further increases the magnitude of preference for lesioned tissue. Synthesis: These results suggest that these herbivores could help maintain disease in this system at a high prevalence (by facilitating disease development) but low severity (through preferential consumption), which is consistent with our field observations of nearly 100% prevalence and low severity in a natural bed where herbivore density is high. Describing such multi‐species interactions in marine systems will advance our predictions of future disease states, as current understandings focus primarily on how environmental change contributes to pathogen outbreaks.

Effects of Erosion Control Works: Case Study–Reservoir Celije, Rasina River Basin, the Zapadna Morava River (Serbia)

The aim of this research was to analyze the impact of implemented erosion control works (ECW) on soil erosion intensity in the watershed of the Ćelije reservoir (Rasina River) in the period between 1968 and 2022. The Erosion Potential Method was used to calculate the annual gross erosion (W), sediment transport (G), and erosion coefficient (Z) in the study area. As a result of the performed ECW there was a general decreasing trend in the intensity of soil erosion processes in the last 54 years. The specific annual gross erosion was 1189.12 m3/km−2/year−1 in 1968, while in 2022 it was 554.20 m3/km−2/year−1. The specific sediment transport was 540.18 m3/km−2/year−1 in 1968 and 253.55 m3/km−2/year−1 in 2022. Due to the changes in the intensity of erosion processes, the specific annual gross erosion decreased by 634.92 m3/km−2/year−1 and the specific sediment transport decreased by 286.63 m3/km−2/year−1. The erosion coefficient was reduced from Z = 0.62 to Z = 0.35. A dependence between the slope of siltation and the natural bed slope was defined. The results show a significant correlation between erosion intensity and performed ECW, providing a basis for future watershed management and defining a strategy for soil erosion control in the Ćelije reservoir watershed.

The role of macroinvertebrate taxonomic resolution in bioassessment of urban streams: A case study from the City of Lodz, Poland

Benthic macroinvertebrates were sampled at 28 sites situated on ten urban streams (Łódź, Poland) representative of a wide range of anthropogenic modifications of water chemistry and bed structure. A total of 5,043 individuals, comprising 121 species belonging to 37 families and 15 orders, were collected. Diptera (35.8 %) and Ephemeroptera (31.8 %) were dominant.The studied sites were grouped into clusters based on separately-analyzed environmental parameters, various levels of taxonomic diversity, and bioassessment variables. All analyses demonstrated similar trends of anthropogenic modification, intensifying concentrically from the suburbs towards the city centre. The first cluster included the upper section of streams; less polluted, richer in ecotone zones and natural stream bed substrate. The second cluster comprised streams demonstrating the influence of moderate human pressure. The third cluster included streams flowing through the city center in concreted beds and which were connected to a combined sewage system in which sewage and rain water are transported through a single canal system and enters the nearest stream. Modification of stream beds was significantly negatively correlated with the number of species, families and orders, but not with total abundance.The number of species, the number of families and the number of orders were highly mutually correlated. Moreover, they were similarly correlated with biodiversity and biotic indices, which are used to assess the ecological status of the aquatic environment. Hence, different levels of taxonomic identification demonstrate similar effectiveness in assessment, i.e. higher taxa of aquatic macroinvertebrates may be suitable for simplified ecological monitoring of urban watercourses.

Marine transmissible cancer navigates urbanized waters, threatening spillover.

Inter-individual transmission of cancer cells represents a unique form of microparasites increasingly reported in marine bivalves. In this study, we sought to understand the ecology of the propagation of Mytilus trossulus Bivalve Transmissible Neoplasia 2 (MtrBTN2), a transmissible cancer affecting four Mytilus mussel species worldwide. We investigated the prevalence of MtrBTN2 in the mosaic hybrid zone of M. edulis and M. galloprovincialis along the French Atlantic coast, sampling contrasting natural and anthropogenic habitats. We observed a similar prevalence in both species, probably due to the spatial proximity of the two species in this region. Our results showed that ports had higher prevalence of MtrBTN2, with a possible hotspot observed at a shuttle landing dock. No cancer was found in natural beds except for two sites close to the hotspot, suggesting spillover. Ports may provide favourable conditions for the transmission of MtrBTN2, such as high mussel density, stressful conditions, sheltered and confined shores or buffered temperatures. Ships may also spread the disease through biofouling. Our results suggest ports may serve as epidemiological hubs, with maritime routes providing artificial gateways for MtrBTN2 propagation. This highlights the importance of preventing biofouling on docks and ship hulls to limit the spread of marine pathogens hosted by fouling species.

Mass Mortality Event of Mediterranean Mussels (Mytilus galloprovincialis) in the Middle Adriatic: Potential Implications of the Climate Crisis for Marine Ecosystems

The effects of the climate crisis are affecting ecosystems at different scales and magnitudes. This paper focuses on a massive Mediterranean mussel die-off observed along the middle Italian Adriatic coast in the summer of 2022. We considered the possible environmental causes of this phenomenon and carried out a climatic analysis of the last decade. We performed field surveys in different locations along a 16 km coastal stretch from Martinsicuro (TE) in the south, to Grottammare (AP) in the north. The study area includes two marine Sites of Community Importance under the European Natura 2000 network. The die-off of the mussels was observed in practically all the natural mussel beds colonizing the study area. As sessile filter-feeding organisms inhabiting the intertidal zone, mussels are highly exposed to variations in environmental conditions such as temperature and nutrient load. We discuss the possible causes of this die-off, proposing that high temperature and the scarce availability of food acted simultaneously as stress factors, generating local unsustainable living conditions for this species.

Exploring the impact of spatial patterns on restoration efforts: promoting self‐facilitating feedback mechanisms with an innovative biodegradable seed mussel collector

Transplantations of organisms in aquatic ecosystems play an important role in ecological restoration and commercial practices. However, success rates of these transplantations, especially when ecosystem engineers are involved, are often low. To enhance transplantation success, the promotion of self‐facilitation between transplants that mitigate environmental stressors is crucial. Besides, spatial patterns resulting from self‐facilitation can enhance ecosystem resilience. Using blue mussels as a model organism, we explored the possibility of increasing transplantation success in a subtidal ecosystem. We used biodegradable structures (“BioShell‐SMCs”) to ameliorate self‐facilitating feedback mechanisms to overcome environmental stressors in the initial post‐transplantation phase, and to increase transplantation success by implementing large‐scale spatial configurations, mimicking natural mussel bed patterns. The structures are an innovation of traditional seed mussel collectors (SMCs) used in mussel cultivation. They consist of a biodegradable net based on a compound of aliphatic polyesters, filled with empty cockle shells around a coconut fiber rope. We tested whether different spatial configurations could increase transplantation success of mussel seed: low versus high density labyrinth pattern and banded pattern. The results of this experiment showed high losses (approximately 75%), with no significant variation between configurations. The lack of migration due to unexpected retention of the biodegradable net hindered the initiation of natural aggregations, resulting in increased competition among mussels. Besides, factors such as hydrodynamic dislodgement, burial and interannual variation likely contributed to the observed losses. While the BioShell‐SMC has not demonstrated large‐scale success, this research contributes to understanding the mechanisms that underlie successful transplantation strategies in aquatic ecosystems.

Influence of Pediveliger Larvae Stocking Density on Settlement Efficiency and Seed Production in Captivity of Mytilus galloprovincialis in Amsa Bay, Tetouan.

In mussel hatchery systems, the settlement process is a crucial element influencing seed yield. The current study assayed the influence of five densities of competent pediveliger larvae on settlement success and post-larvae production. We showed an inverse relationship between density and settlement efficiency, e.g., an attachment success of 99.4% at the lowest density (35 larvae/cm2) but only 9% at the highest density (210 larvae/cm2). However, post-larvae production was higher at intermediate larvae densities (70 larvae/cm2). The reimplementation of treatments upon post-larvae density after 6 weeks post settlement showed that the lowest-density groups bore both the highest post-larvae growth rate (22.24 ± 4.60 µm/day) and the largest head batch (48% of the size distribution), as compared to the higher-post-larvae-density groups. These results highlight the importance of optimizing both pediveliger larvae density and post-larvae density, to maximize high-quality seed yield in local hatcheries. Current rearing technologies would assure a timely commercial seed production to protect natural sea rocky beds in Alboran Sea coasts.

Density of hydrobiont populations in the coastal zone of the Barents Sea and in aquaculture

Objects for obtaining additional food sources and maintaining the quality of the environment in multicultural farms of the northern seas can be kelp (Laminaria saccharina), sea urchin (Strongylocentrotus droebachiensis), mussel (Mytilus edulis), which do not require significant costs during cultivation. The aim of the study was to assess the productive potential of species promising for multiculture based on the density of their populations. The work is based on the materials of expeditionary research of marine communities of the Barents Sea and on the analysis of scientific and practical developments on the cultivation of aquatic organisms in the reservoirs of the High North. Kelp and mussels are characterized by a wide range of variation density and biomass, and individual characteristics. On the Murman coast, in natural kelp beds, the average biomass is 1.4–5.4 kg/m2 (up to 16 kg/m2), and the average density is 9–104 specimens/m2 (up to 172 specimens/m2), significantly varying depending on the local conditions of the biotope. The largest biomass values are characteristic of the mussel population at the Kola Bay mouth (4.8–17.8 kg/m2), and the highest population density was noted in the bays of the Eastern Murman (45030–61167 specimens/m2). Mussels with the largest size and weight (from the studied areas) were found in the Pechenga Bay (shell height 4.3±0.1 cm, mussel weight 6.84±0.34 g). The population density parameters of cultivated species in marine benthic communities, which affect the growth of aquatic organisms, can be recommended for use in multicultural farms of kelp, mussels and sea urchins.

Mito‐nuclear discordance and phylogeography of the surf clam Mesodesma donacium along the Southeast Pacific coast

AbstractMesodesma donacium is a surf clam endemic to the southeast Pacific coast, and it is an important resource species of the sandy beach artisanal fishery in Peru and Chile. Over time, the species has shown high variability in population dynamics (presence and abundance), which has been attributed to overfishing and environmental events. In this study, we assess the phylogeography of seven natural beds of M. donacium (17 to 42° S), to reveal the geographic distribution of the genetic diversity through the analysis of 278 sequences of the mitochondrial gene COI. Sequences of the nuclear genes 18S and 28S were used to evaluate the divergence of COI haplogroups. Two divergent parapatric mitochondrial haplogroups were found, which lacked divergence at nuclear markers (18S and 28S); this mito‐nuclear discordance allows inferring that there is no reproductive isolation of mitochondrial haplogroups. The North haplogroup is the only one present at the northernmost site, while only the South haplogroup was present in Cucao in the south. Between 28° and 32° S, coincident with a coastal biogeographic break at 30° S, both haplogroups are in sympatry. Haplogroups differed in their genetic structure, with the North haplogroup representing a single, highly diverse population and the South haplogroup with genetic differentiation and more restricted genetic diversity and gene flow. The divergence in mitochondrial haplogroups without nuclear divergence suggests a past scenario of geographic isolation in the northern and southern areas, without developing reproductive isolation, followed by secondary contact. Given the phylogeography, genetic information should be considered in restocking and management activities.

River Park Assessment: 2D Hydraulic Watercourse Modeling for Nature-based Solutions in Urban Area

Over time, fragmentation of semi-natural habitats in urban areas has become a pressing concern, disrupting ecological processes within cities. The focus on preserving open ecosystems has grown, highlighting the need to enhance resilience in urban riverside areas for effective ecosystem restoration. Comprehensive studies on river valleys, considering both hydrology and ecology, play a crucial role in urban river ecosystem development. Our article explores the potential of protective zones with urban vegetation and watercourses as Nature-based Solution within Krakow's ongoing riverine park system development. The study's cross-sections in the River Park area revealed dominant velocities ranging from 0.67 to 2.0 m s-1for SWQ (mean annual maximum flow) and below 0.67 m s-1for Q1% (1% annual exceedance probability flow). The hydrological analysis accurately captured the natural river bed channels' curvature, providing the basis for a two-dimensional mathematical model to visualize the hydraulic structure of protected sites. Integrating water and greenery management systems in urban areas offers significant potential for adapting to climate change, mitigating extreme weather events. Our research's novelty lies in applying 2D hydraulic modeling, demonstrating how River Parks can serve as climate change mitigation solutions in urban environments.

Investigating and Modeling of the Scour Downstream of a Tree Trunk Deflector in a Straight Channel

Scouring depends on several factors, including the water flow of artificial obstacles, sections, piers, and foundations, the disturbance of bed materials, and soil permeability. The other factors are the non-parallelism between piers and the water flow, the type of river activity (static or dynamic), and the existence of a waterfall or an obstacle that forms a waterfall in natural bed materials, causing the underlying bed materials to be washed away. This study fully investigated how the movement of a tree trunk affects a river’s flow by considering different flow conditions using the artificial neural network (ANN) model. A feedforward optimal network with the error back-propagation training algorithm and sigmoid transfer functions was used for four models. To determine the number of neurons in the hidden layer, one and ten neurons were selected in the hidden layer according to verification indicators. In addition, a physical model was utilized to measure data. To verify and test the models, our data were gathered in a laboratory using the physical model. Considering the network structure of one neuron in the hidden layer, a comparison was made between dimensional and dimensionless parameter models that are effective in terms of the dimensions of the scour hole. The comparison between the results of the ANN and the measured data using nonlinear regression models demonstrated that the ANN was more accurate and capable of simulating phenomena. Additionally, R and RMSE values were between 0.93 and 0.98, as well as 0.18 and 0.013, respectively. Finally, the results related to the width, height, length, and depth of the scour revealed that the modified DOT model had the best agreement with Mahdavizadeh’s measured data.

Gaping behaviour of Blue mussels (Mytilus edulis) in relation to freshwater runoff risks

Shellfish grown for food are vulnerable to environmental contamination, potentially rendering them unsafe for human consumption. Non-invasive gape (valve openness) sensing allows in-situ monitoring of bivalve shellfish behaviours, such as feeding, that can result in exposure to contaminated waters. Sensors were attached to Blue mussels and deployed for 10 days on natural mussel beds in Dundrum Bay, Northern Ireland. Data showed a tidally synchronous behaviour pattern of high openness at high water and vice versa. It is likely that this is, at least in part, due to extreme salinity variation (1.8–33.6) resulting from near total water exchange with each tide in the bay. This behaviour is likely to infer a degree of protection from contaminants during periods of low water, a time at which runoff-derived pollutants are most concentrated.

BED PROTECTION FOR EXTREME STORM SURGE INFLOW THROUGH FAILING SLUICEGATES

At the northern part of The Netherlands the closure dam Afsluitdijk is situated. It is the primary flood defense that closes off Lake IJssel from the Wadden Sea to protect the northern provinces against storm surges. This structure was built in the 1930’s and needed to be improved to withstand the foreseen increase in storm surge conditions and sea level rise. It consists of a 32 km long dam with five discharge sluices for regulating the water level at Lake IJssel. Three of these sluices are located in the west end of the dam and two in the east end. Due to climate change larger discharges are foreseen. Therefore two new sluices were built in between the three old sluices at Den Oever in the west end of the dam to increase the capacity. A new bed protection was designed at Lake IJssel to ensure the stability of the old and new sluices. This bed protection needs to withstand the inflow during the worst case scenario that one sluice does not close during a 45 hour storm surge. This event has a probability of occurrence of 1/1,000,000 per year. During this extreme load case, water flows from the Wadden Sea through the open sluice gates into Lake IJssel. The water level difference is up to 6.6 m. This causes discharges up to 3600 m3/s and currents that are supercritical with speeds up to 9 m/s. Erosion of the bed cannot be prevented entirely with these high velocities. The length of the bed protection is designed large enough to keep the scour hole away from the sluices. The bed protection consists of a structural and a natural part. The natural part was introduced to minimize the length of the structural protection, reducing the construction costs and CO2 footprint. For this design approach the erosion resistant boulder clay layers in the subsoil were taken into account as natural bed protection, ‘Building with Nature’. To achieve the custom made design was a challenge. To predict the flow behavior in combination with the erosion process was extremely complex. This could not be predicted with the conventional formulas and methods. Therefore multiple approaches were used and combined. This resulted in the design being based on the combination of computer simulations, 2D and 3D model tests and calculations with conventional formulas. The structural part of the bed protection has a length of 24 m. The first 19 m is a concrete slab with a sheet pile at the end. The last 5 m consists of grouted rock. The thickness of the concrete slab and grouted rock is 1-1.5 m. This large thickness is required to prevent uplift due to the supercritical flow. Further downstream of this structural bed protection a scour hole will develop. At this location the boulder clay forms the natural part of the bed protection. The expected development of the flow field and geometry of the scour hole during the 45 hour storm surge was determined. The scour resistance of the boulder clay was based on laboratory tests with samples taken on site. This lead to the conclusion that the boulder clay reduces the development of the scour hole enough to ensure the stability of the structural part of the bed protection and the stability of the sluices.