Tidal Range Research Articles

The effect of tidal range and mean sea-level changes on coastal flood hazards at Lakes Entrance, south-east Australia

Despite being well-documented in other countries, the roles that anthropogenically induced changes and natural variability in tidal processes play in modulating coastal flood frequencies have not been investigated in Australia. Here we conduct a brief assessment of changes in tidal variability around Australia. We then apply a simple attribution framework to quantify the separate and joint effects of tidal range changes and increasing relative mean sea level on nuisance flood frequency at the location with the largest relative changes in tidal range, Lakes Entrance, Victoria. To understand how these changes in variability affect flood hazards, we consider a nuisance flood threshold based on recent coastal flood impact surveys. Results show that increases in the heights of high tides over recent years have exerted a large influence on coastal flood frequencies. These recent changes are potentially linked to changes in channel dredging regimes. We show that 93% of nuisance flood days since 2009 would not have occurred without these tidal range changes or the coincident increases in the mean sea level. We demonstrate the importance of considering tidal processes in estuarine coastal flood hazard assessments for future planning, even if these processes do not represent a substantial flood threat today. We discuss the implications of this study for future work on estuarine flood hazards and the benefits of considering impact-based thresholds in the assessment of such hazards.

Tidal Modulated Shoreface Facies in Eocene Agbada Formation, Niger Delta Basin, Nigeria

Tidal influence shoreface are shoreface deposit generated by wave induced tidal action. The extent of the tidal impact from lower to upper shorefaces depend mostly on the tidal range thereby controlling the impact of different shoreline wave action on sediment distribution across shorefaces. The Tidally influenced shoreface sediment display wave generated structure, however the structure are strongly associated with tidal generated structures and trace fossil consistent with tidal depositional setting. Shoreface successions in Titun well display a wide range of variability, largely restricted to the lower and middle shoreface intervals. This variation was controlled by relative wave dominance and intermittent pulsating nature of associated tidal bed deposition. The successions were subdivided into three end members, although a complete gradation between them exists. High energy shoreface consist almost entirely of erosively based amalgamated tide and wave beds with minimal bioturbation. Intermediate energy shoreface consist of stacked laminated to burrowed intervals, recording repeated erosive storm bed emplacement, followed by opportunistic colonization, and commonly overprinted by resident fairweather burrowing. Weakly storm-affected low energy shorefaces typically show intense bioturbation with minimal preservation of high energy beds. Based on the association of the facies, facies vertical build-up patterns, sedimentary structures and trace fossil content, the T1 sands in Titun well are interpreted as a prograding tidally influence shoreface deposit. This interpretation is supported by presence of tide generated structures and marine trace fossil, due to the prevalence of several tidal imprint as suggested by several mud drapes and flasers, couplets of sands and shale’s in heterolithic sequences, and bidirectional current structures (herringbone cross stratification), a tidally influence shoreface geological model is suggested for deposit.

Geographical variation of bacterial and ciliophoran communities in tidal flats in a continental archipelago.

In tidal flats, which are located at the transition zone between terrestrial and marine ecosystems, environmental factors such as temperature, sediment particle size, and tidal range exhibit geographic variation. Accordingly, the composition and structure of the microbial communities in the tidal flats are likely to vary in geographically different habitats. To clarify these differences with environmental factors causing them, we analyzed microbial communities consisting of bacteria and ciliates in sediments collected from nine tidal flats in geographical diverse region from Hokkaido to Kagoshima, Japan. The results confirmed that the community structures of bacteria and ciliophora in tidal flat sediments differed at the geographical scale of the Japanese archipelago. However, the variation could not be explained by the physical distance between the tidal flats nor by the differences in the trophic conditions among the tidal flats. Instead, the OTU richness of both the bacterial and ciliophoran communities was significantly related to the tidal range. The results also showed that bacteria and ciliophora tended to form similar communities among the tidal flats with similar median particle sizes. Furthermore, ciliophoran communities were similar among the tidal flats with similar bacterial communities. The results suggest that bacteria and ciliophora interact each other through trophic relationships or physical and chemical processes in the sediment habitats.

Analysis of physical, chemical and condition of mangrove ecosystems for development of mandrove crab cultivation (Scylla serrata, Forskal)

The aims of this research are; (1) analyzing the physical and chemical characteristics of coastal waters in mangrove forest areas for the development of crab cultivation businesses (2) Assessing the condition of mangrove forest ecosystems, (3) testing prototypes of technology for crab cultivation businesses in mangrove forest areas. The benefit of the results of this research is to determine the feasibility of crab cultivation based on the biophysical and chemical characteristics of the coastal waters of the mangrove area, so that the cultivation business can be sustainable. To achieve this, a field survey was carried out by collecting primary and secondary data. Primary data includes physical and chemical parameters as well as mangrove forest conditions. The results of observations of the condition of the mangrove area, for the Important Index Value (INP) of mangroves, Rhizopora, sp sampling I (191.23), sampling II (181.72), sampling III (205.07), this shows that in sampling III for The Rhizopora sp type has a greater role in maintaining the sustainability of the ecosystem. For the dominance index value, the value for the entire station is 0.02 – 0.03. This shows that there is no species that dominates other species or the community is in a stable condition. Meanwhile, the species diversity index value in the entire sampling area has low species diversity, namely 0 < H < 2. The results of physical observations of waters, the results of tidal data processing using the Admiralty method show that the mean sea level (MSL) is 200.41 cm, The lowest low sea level (LLWL) is 112.86 cm and the highest high sea level (HHWL) is 279.41 cm, the tidal range (range) is 166.36 cm. From the value of the Formzahl number (F value = 1.89) it can be concluded that the type of tide around the observation location is a mixed tidal type that tends to be single daily. The results of observations of water salinity parameters at the research location ranged from 25.0 - 27.1 ‰ with an average value of average 26.0 5 ‰, pH, nitrite (NO2), nitrate (NO3) and phosphate (PO4) in water. The average pH value of 6.90, the average nitrite content value of 0.020, the average nitrate content value of 0.236 and the average phosphate content of 0.145 indicate good water quality for mariculture purposes, and also indicate the condition of the waters that have not been polluted.

Wave distribution and proposed seawall design around Tanjung Emas Port, Semarang

On May 23rd, 2022, an extreme coastal event occurred around the northern coast of Java. This event had caused the collapsed of several seawall segments around Tanjung Emas Port, Semarang. Combined with wave overtopping, it led to severe flooding and economic damages to the port operation. Responding to the event, this research aimed to characterize the hydrodynamic condition around the port and proposed a seawall design. The research was done through field observation, wave climate characterization, and numerical simulation. The field observation confirmed the extent of the damage and wave condition around the harbour. The wave climate study, based on a global wave reanalysis data, confirmed that the offshore wave height could reach 3 m during high wave season, with wave period of 4 – 6 seconds coming from the northwest. The tidal range is up to 1 m with highest astronomical tide (HAT) is at +0.65 MSL. The extreme value analysis gave a 3.7 meter of offshore design wave height for 100-year return period or up to 1.7 meters wave height nearshore. The proposed seawall crest elevation is at least at +3.40 meters above the mean sea level to avoid overtopping, which is 1.1 m higher than the existing seawall.

Effect of Estuary Urbanization on Tidal Dynamics and High Tide Flooding in a Coastal Lagoon

AbstractHigh tide floods (HTFs) are minor, shallow flooding events whose frequency has increased due to relative sea‐level rise (SLR) and secular changes in tides. Here we isolate and examine the role of historical landscape change (geomorphology, land cover) and SLR on tides and HTF frequency in an urbanized lagoonal estuary: Jamaica Bay, New York. The approach involves data archeology, historical (1870s) map digitization, as well as numerical modeling of the bay. Numerical simulations indicate that a century of landscape alterations (e.g., inlet deepening and widening, channel deepening, and wetland reclamation) increased the mean tidal range at the head of the bay by about 20%. The observed historical shift from the attenuation to amplification of semidiurnal tides is primarily associated with reduced tidal damping at the inlet and increased tidal reflection. The 18% decrease in surface area exerts a minor influence. A 1‐year (2020) water level simulation is used to evaluate the effects of both SLR and altered morphology on the annual number of HTFs. Results show that of 15 “minor flood” events in 2020, only one would have occurred without SLR and two without landscape changes since the 1870s. Spectral and transfer function analyses of water level reveal frequency‐dependent fingerprints of landscape change, with a significant decrease in damping for high‐frequency surges and tides (6–18 hr time scale). By contrast, SLR produced only minor effects on frequency‐dependent amplification. Nonetheless, the geomorphic influence on the dynamical response significantly increases the vulnerability of the system to SLR, particularly high‐tide flooding.

The Gondola: a boat to respond to the history, and the morpho-dynamics of the Venice Lagoon

Origin and evolution of the gondola have been reconstructed from historical and documentary written and pictorial sources (figures in books, engravings and paintings), in relation to the physical environment of the Lagoon, its morpho-dynamics with shallow and deep waters, marshes and canals. Particular care has been applied to the physical and hydrodynamic aspects in order to interpret the data and understand how the ancient Venetians could have had an advanced knowledge of the tidal range from sea stairs, tidal phase from the algae colour and direction, bottom depth from surface ripples, and exchanges between the Lagoon and the sea from suspended debris. The various elements of the boat are considered in terms of use and physical advantage, e.g. rowing style, cabin, hull and decorations. The boat evolution has been followed and documented over the centuries. This study clarifies the original shape of the gondola in the 11th century, from the analysis of the contemporary manuscripts and Byzantine mosaics in Ravenna and Venice, and a tablet of the early 14th century. In the 16th century, the gondola changed shape and size. The reason of this restyling was unknown, but has been found in the contemporary edicts, diaries and chronicles and other historical sources. The transformation was kept as a military secret, as well the production of a fleet of small boats provided of rostrums to sail on the rivers Po and Adige and fight against Ferrara and its Allies of the League of Cambrai. A comparison with the Viking- Norman vessels of Bayeux, Palermo and some codices show several strong analogies with the military gondolas of the 16th century. An overview of the written and pictorial sources has allowed to classify the various gondola types and recognize several technical details. Finally, the size and depth have been considered to interpret the ancient chronicles that mentioned that in the occasion of the most extreme storm surges, the gondolas could ride on San Marco Square, i.e. the flooding water depth necessary to float and to navigate over street paving.

The tidal prism as a dynamic response of a nonlinear harmonic system

As known, the empirical relationship between the equilibrium cross-sectional area of a lagoon inlet and the tidal prism was intuited for the first time by LeConte [“Discussion on the paper, “Notes on the improvement of river and harbor outlets in the United States” by D. A. Watt,” Trans. ASCE 55, 306–308 (1905).] and then formalized by O'Brien [“Estuary tidal prism related to entrance areas,” Civ. Eng. 1(8), 738–739 (1931)]. This relationship requires knowledge of the tidal prism, which can be estimated either using the cubature method or the current data method [Jarrett, Tidal Prism-Inlet Area Relationships (Coastal Engineering Research Center, US Army Corps of Engineers, Fort Belvoir, VA, 1976)], both of which involve the execution of a number of experimental measurements. However, these methods, besides being very expensive, can only provide the prism value in the present condition and do not allow for predictions in the case of significant morphological changes, of both natural and anthropic origin, to the tidal inlet. On the other hand, the hydrodynamic relationship, which links the tidal prism to the product of the tidal range and the basin extension, can only give a coarse estimate of the prism, especially when the value of the tide outside the lagoon is considered. In this work, we propose a simple hydrodynamic relationship based on the dynamic response of a nonlinear harmonic system. This is a relationship that requires the calibration of a single physically based parameter. Through this relationship, knowing the geometric characteristics, the bottom friction of the inlet channel, the surface of the basin, and the tide amplitude in the open sea, it is possible to estimate the tidal prism. The application of this relationship to real cases shows a good agreement with the experimental data.

Meta-analysis reveals controls on oyster predation

Predators can have strong roles in structuring communities defined by foundation species. Accumulating evidence shows that predation on reef-building oysters can be intense and potentially compromise efforts to restore or conserve these globally decimated foundation species. However, understanding the controls on variation in oyster predation strength is impeded by inconsistencies in experimental methodologies. To address this challenge, we conducted the first meta-analysis to quantify the magnitude, uncertainty, and drivers of predator effects on oysters. We synthesized 384 predator-exclusion experiments from 49 peer-reviewed publications over 45 years of study (1977 to 2021). We characterized geographic and temporal patterns in oyster predation experiments, determined the strength of predator effects on oyster mortality and recruitment, and assessed how predation varies with oyster size, environmental conditions, the predator assemblage, and experimental design. Predators caused an average 4.3× increase in oyster mortality and 46% decrease in recruitment. Predation increased with oyster size and varied with predator identity and richness. Unexpectedly, we found no effects of latitude, tidal zone, or tidal range on predation strength. Predator effects differed with experiment type and tethering method, indicating the importance of experimental design and the caution warranted in extrapolating results. Our results quantify the importance of predation for oyster populations and suggest that consideration of the drivers of oyster predation in restoration and conservation planning may hasten recovery of these lost coastal foundation species.

Improvement of a coastal vulnerability index and its application along the Calabria Coastline, Italy

The present paper further develops a coastal vulnerability index formulation (CVI) previously proposed by the authors by integrating a new variable and redefining three variables to improve the suitability of the index for low-lying coasts. Eleven variables are divided into three typological groups: geological, hydro-physical process and vegetation. The geological variables are: geomorphology, shoreline erosion/accretion rates, coastal slope, emerged beach width, and dune. The hydro-physical process group includes: river discharge, sea-level change, mean significant wave height and mean tide range. The vegetation variables are: vegetation behind the back-beach and coverage of Posidonia oceanica. The index was applied to a stretch of the Ionian coast in the province of Crotone in the Calabria region (Southern Italy), and a vulnerability map was produced. A geography information system (GIS) platform was used to better process the data. For the case study area, the most influential variables are shoreline erosion/accretion rates, coastal slope, emerged beach width, dune, vegetation behind the back-beach, and coverage of Posidonia oceanica. The most vulnerable transects are those near urban areas characterized by the absence of dunes and vegetation. Statistical and sensitivity analyses were performed, and the proposed CVI was compared with the previous formulation proposed by the authors and with two other CVI methods present in the literature.

Vibrio vulnificus and Vibrio parahaemolyticus in Oysters under Low Tidal Range Conditions: Is Seawater Analysis Useful for Risk Assessment?

Human-pathogenic Vibrio bacteria are acquired by oysters through filtering seawater, however, the relationships between levels of these bacteria in measured in oysters and overlying waters are inconsistent across regions. The reasons for these discrepancies are unclear hindering our ability to assess if -or when- seawater samples can be used as a proxy for oysters to assess risk. We investigated whether concentrations of total and human pathogenic Vibrio vulnificus (vvhA and pilF genes) and Vibrio parahaemolyticus (tlh, tdh and trh genes) measured in seawater reflect concentrations of these bacteria in oysters (Crassostrea virginica) cultured within the US lower Chesapeake Bay region. We measured Vibrio spp. concentrations using an MPN-qPCR approach and analyzed the data using structural equation modeling (SEM). We found seawater concentrations of these bacteria to predictably respond to temperature and salinity over chlorophyll a, pheophytin or turbidity. We also inferred from the SEM results that Vibrio concentrations in seawater strongly predict their respective concentrations in oysters. We hypothesize that such seawater-oyster coupling can be observed in regions of low tidal range. Due to the ease of sampling and processing of seawater samples compared to oyster samples, we suggest that under low tidal range conditions, seawater samples can foster increased spatial and temporal coverage and complement data associated with oyster samples.

Sleech Salt Making from the Solway to the Mersey in the Medieval and Early-Modern Period

Salt making by the method known as ‘sleeching’ was practised extensively along the coasts of North-West England and southern Scotland, from earliest times until it came to a sudden end in the eighteenth century with the widespread availability of cheap rock salt from Cheshire. The method involved the gathering of salt-enriched sand from below the high-tide mark, and washing the same in troughs to produce a concentrated brine, which was then evaporated in lead pans. The region from Solway to Mersey was one of only four parts of Britain where the necessary conditions for sleeching could be found, namely a considerable tidal range, extensive sandy shores backed up by flat land above the spring tide line, and easy access to plentiful supplies of fuel, generally peat. Physical, cartographic, place-name and documentary evidence show that, at its height, more than one hundred locations along the coast were engaged in the manufacture of salt, largely as a seasonal by-employment, and generally for local consumption.

Fortnightly variability of horizontal salinity gradient affects exchange flow in the Sumjin River estuary

The horizontal salinity gradient has been reported to play a crucial role in fortnightly variability of estuarine exchange flow in short estuaries. However, spatiotemporal variations in the salinity gradient and exchange flow have not been examined over an entire short estuary, as only data observed only at specific points was available. We analyzed the variation in salinity gradient along the entire Sumjin River estuary and its effect on the exchange flow over fortnightly tidal cycles based on observations and numerical model experiments. The salinity gradient and exchange flow were in different phases between the lower and upper estuaries by 6–7 days. The maximum salinity gradient periodically reciprocated along the channel as a result of salt flux changes determined by vertical mixing. The stronger exchange flow (> 0.04 m s-1) changed location from mouth to head of estuary while the tidal range decreased, resulting from variability of the salinity gradient. The horizontal salinity gradient is large enough to overwhelm the vertical mixing effect on the exchange flow. The spatiotemporal changes of strong exchange flow correspond well with the horizontal Richardson number value (> 3). This study suggests that for the health of estuarine ecosystems, it is important to determine the spatiotemporal variation in exchange flow throughout the estuary.

Development and validation of an AI-Driven model for the La Rance tidal barrage: A generalisable case study

In this work, an AI-Driven (autonomous) model representation of the La Rance tidal barrage was developed using novel parametrisation and Deep Reinforcement Learning (DRL) techniques. Our model results were validated with experimental measurements, yielding the first Tidal Range Structure (TRS) model validated against a constructed tidal barrage and made available to academics. In order to proper model La Rance, parametrisation methodologies were developed for simulating (i) turbines (in pumping and power generation modes), (ii) transition ramp functions (for opening and closing hydraulic structures) and (iii) equivalent lagoon wetted area. Furthermore, an updated DRL method was implemented for optimising the operation of the hydraulic structures that compose La Rance. The achieved objective of this work was to verify the capabilities of an AI-Driven TRS model to appropriately predict (i) turbine power and (ii) lagoon water level variations. In addition, the observed operational strategy and yearly energy output of our AI-Driven model appeared to be comparable with those reported for the La Rance tidal barrage. The outcomes of this work (developed methodologies and DRL implementations) are generalisable and can be applied to other TRS projects. Furthermore, this work provided insights which allow for more realistic simulation of TRS operation, enabled through our AI-Driven model.

Factors controlling massive green tide blooms on the coasts of Jeju Island, Korea

To determine the driving mechanisms between submarine groundwater discharge (SGD) and massive blooms of the green alga Ulva, we examined the magnitude of SGD and SGD-derived nutrient fluxes from November 2019 to July 2020 in Ihotewoo (north) and Bangdu (east) bays, Jeju Island, Korea. The variability of SGD flux at both the sites, where the hydraulic gradient is low, closely followed the daily variability of the tidal range, indicating that SGD flux is primarily driven by tidal pumping. Although the average annual SGD-driven nutrient fluxes were 24–37 % lower in Bangdu Bay than in Ihotewoo Bay, massive Ulva blooms only occurred in Bangdu Bay. A longer residence time (poor water exchange) and continuous SGD input with high dissolved inorganic nitrogen play a significant role in the growth and extentsion of Ulva blooms.

The forgotten ones of ports: The filter feeders at the heart of siltation processes

Siltation is a major concern in dynamic and complex ecosystems, such as ports. The mud must be regularly dredged to avoid disturbing the navigation channels. Sediments are carried by the waters entering the port and are partially trapped by harbour structures. Numerous studies have been conducted on the physical factors influencing siltation in port areas, whereas, few have focused on the role of biotic factors in mud formation. However, research in other contexts has shown that organisms that are abundant in pontoons, such as bivalves and tunicates, play an important role in this siltation process. All of these organisms belong to the filter feeder group. The sediments sucked in by the filter feeders are excreted in the form of faeces or mucus-bound pseudo-faeces. These waste materials, called bioproducts, settle efficiently and are involved in the composition of the mud. This study aimed to highlight the role of filter feeders in the siltation process in port areas and to determine the factors that influence the production of bioproducts by filter feeders. To investigate the role of filter feeders in the siltation processes, an experimental analysis was conducted in the largest marina in Europe (La Rochelle, France). It is divided into four basins with distinct filter feeder communities and environmental conditions, allowing for a detailed study of the environmental factors that influence the production of bioproducts. This analysis consisted of recovering and studying the bioproducts generated by the filter feeders using sediment traps fixed under pontoons. To explore the evolution of this biological production, 16 campaigns were conducted from January to March 2020 and May to July 2020. The total amount of dry matter produced was constant between seasons at approximately 130 g/m2/d; marina-wide, this amount represents a total daily production of 3.2 tons. However, the production amount varies spatially and temporally in relation to marine hydrodynamics and the organisms involved. Bioproduction was taxon-dependent: areas abundant in oysters and mussels were the areas with the most pronounced bioproduction, whereas there was no significant relationship between bioproduction and the presence of tunicates or scallops. If we consider bioproduction on a seasonal scale, we can see that the campaigns with the greatest production correspond to the periods when the sediment supply was the highest, i.e. when the tidal range was the highest. The quality of the bioproducts (organic matter content) differed between seasons, which can be explained by both environmental and metabolic changes. Understanding the role of filter feeders in siltation processes appears to be essential in port environments that need to be regularly dredged to ensure safe navigation.

Accounting for environmental stress in restoration of intertidal foundation species

Abstract Restoration of foundation species in historical habitat may be difficult if adult facilitation is obligatory for survival of early life stages. On intertidal Mediterranean coasts, large‐scale loss of the dominant forest‐forming macroalga Ericaria amentacea have prompted restoration efforts using recruits. Yet, early life stages may be more susceptible to the abiotic stress that characterizes their habitat. We tested strategies to enhance resilience of lab‐cultured juveniles of E. amentacea to environmental stress in historical habitat lacking conspecifics. Juveniles were exposed in culture to fluctuations of the dominant physical stressors, irradiance and temperature, and then outplanted in upper and lower zones of their native intertidal range. Without adult canopy, juvenile outplant survival was limited to the lower tidal range, with nearly complete mortality in the upper zone. Survival was also strongly determined by spatial clumping of recruits within the outplant substrate. Longer‐term growth in the lower zone was enhanced by fluctuating mild stress in culture, with variable irradiance and concurrent heat pulses increasing post‐outplant cover by 40%–60% after 4 months. Clumping also promoted growth across experimental treatments. Synthesis and applications. Reliance on self‐facilitation feedbacks is a common barrier to foundation species restoration in high‐stress habitats. Our results suggest that without adult habitat amelioration, environmental stress limits recruit survival in intertidal algal forest. Yet, exposure to transient, low environmental stress in culture and outplanting of clumped individuals may confer resilience and allow successful establishment of early life stages in zones of reduced abiotic stress, providing a source for gradual colonization of more high‐stress areas.

Spectral analysis of near-breaking wave data observed in macro-tidal environment by zero up-crossing transform method

In this study, frequency spectra were obtained by applying the Zero-Up Crossing Transform (ZUCT) and the fast Fourier transform (FFT) methods from the waveform data observed at one point of a macro-tidal beach. Their frequency spectrum conversion characteristics according to changes in water depth can be investigated and compared with the TMA spectrum applicable to shallow water. The ZUCT method is based on the reproducibility of the actual wave height and period and applies a technique that guarantees energy conservation. In particular, when the tidal level is low, the spectrum by the ZUCT method seems to show a similar shape to the TMA spectrum over the entire tidal range even if the spectrum is deformed due to partial depth-induced wave breaking. This study derived the reduction rate of the frequency spectrum by wave breaking, assuming that the wave height distribution for each frequency followed the Rayleigh distribution. Based on this, we proposed the TMA-SOON (Spectrum Operated On Nearshore), a frequency spectrum equation applicable to the nearshore zone where wave breaking occurs. Therefore, by using this formula, it is possible to estimate the incoming wave energy as well as the incoming frequency spectrum from the observation data in the wave breaking region.

Parametric study on the short-term extreme mooring tension of nylon rope for a point absorber

A series of 1:40 model tests are carried out to study the dynamic responses of a point absorber moored by three taut nylon ropes under irregular wave conditions. The experimental results are applied to calibrate a numerical model, and then the calibrated numerical model is applied to study the influence of pretension, mooring axial stiffness, current velocity and tidal range on extreme mooring tension under head sea wave conditions. Both the global maximum method and the average conditional exceedance rate method are applied to study extreme mooring tension based on fifty 3-h fully coupled analyses. The nonlinear strain-tension curve is used in numerical simulations to consider the material non-linearities of nylon rope. To discuss the influence of axial stiffness on extreme mooring tension, nonlinear strain-tension curves of a worked rope and a new rope are studied. The numerical simulations under three current profiles are conducted to study the influence of current velocity on extreme mooring tension. It is found that the influence of axial stiffness and current velocity on extreme mooring tension is significant, and the influence of current velocity on extreme mooring tension reduces with the increase of mooring pretension.

Latitudinal and archipelago effect on the composition, distribution, and abundance of zooplanktonic organisms in the Gulf of California

The upper Gulf of California is one of the most energetic regions owing to its tidal range and strong tidal currents, making the upper gulf and the archipelago zone highly turbulent regions; the abundance of zooplankton should be associated with mixing phenomena. We aimed to determine the latitudinal distribution of zooplanktonic organisms in this region and the influence of the islands on their distribution and abundance using historical data. Distribution of abundance followed the current patterns, the archipelago influences abundance favorably but does not affect diversity. Latitudinal zooplankton richness had a quasi-parabolic shape. A decrease in richness was observed at 27.5°N, in the archipelago region, with maximum richness at 26.5°N and 28.5°N. The distribution of latitudinal ranges is consistent with geometric constraints models; taxa with wide ranges are in the central area, while those with narrow ranges are near the boundaries and the Upper Gulf. Zooplankton responds in some way to the existence of the southern boundary as shown by the decrease of richness in this region. At the whole scale of the Gulf, the distribution of richness followed geometric constraints model, while at smaller scales, distribution and abundance are conditioned by the hydrodynamics of the Gulf. We compared zooplankton spatial distribution with Sea Level Anomaly, Sea Surface Temperature, and Chlorophyll-a concentrations from Copernicus to establish relationships between these factors. We performed Cluster and Redundancy Analysis to characterize similarities between stations in terms of biomass and taxon composition and to assess the importance of environmental variables on the distribution of zooplankton.