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Long sand banks elongated parallel with the main tidal flow, are abundant in European seas and most have one slope steeper than the other. For the majority of these sand banks the direction faced by the steeper slope corresponds with the clockwise or anticlockwise sense of rotation of the tidal current vectors in relation to the net sand transport direction. This finding is interpreted as being the result of a lag effect in the picking up and putting down of fine sand through the tidal cycle. It has considerable relevance to both the coastal engineer and the geologist as it suggests portions of coast which are likely to be subject to a long term, net sand loss to, or gain from, the offshore zone.

Earlier work indicated that currents move alternately up and down the floors of submarine canyons with greater average speeds and longer duration downcanyon. Now we find there are roughly synchronous movements up to at least 34 m above the canyon floors. The speeds decrease somewhat with height above the canyon floors and upcanyon flows are more significant. The patterns of up- and downcanyon flow at adjacent stations usually can be matched, indicating that the currents are related to internal waves. Crosscanyon flow occurs, particularly during periods of strong crosscanyon winds and usually has a definite sequence of repetition related to the tidal cycle. The strongest and longest transverse flows were in the broadest floored canyon. During storms with strong onshore winds, there are violent downcanyon flows that have carried current meters with them and eroded the floors, but the speeds are unknown.

A pattern in moonquakes, which correlates with the monthly tidal cycle, also correlates with a phase-shifted pattern of a 7-month tidal cycle. The lead of approximately 2 months in moonquake occurrence can be explained if local tidal forces are combined with a moonquake-driving force. This force, assumed to result from the 6-yr physical libration in latitude, would cause N-S sliding of an outer layer across a solid layer within a decoupled core in a lunar model. During 1969-1971, the sliding would be southward with a progression of monthly maxima in the combined forces. Where these forces control moonquakes, the reversal in direction of the 6-year cyclic force in early 1972 should cause a minimum in moonquake activity. Decreases toward such a minimum did occur simultaneously in the similar progressions of monthly moonquakes and maxima in the combined forces at the most active hypocenter. Repetition of the 1966-1971 force pattern in 1975-1977 should produce a corresponding repetition of the moonquake pattern.

The ebb and flow of the tides in an estuary affect not only the hydrographical conditions but also to a marked extent the abundance of zooplankton populations. Observations were made during one particular cycle studied during February 1961. Water samples and plankton were collected at regular intervals of two hours at a fixed station in the mid-estuarine region of the river Godavari. The temperature of the waters seems to follow the course of the day and the atmospheric conditions, rather than the tides, whereas the salinity variations during 24-hour period closely followed the tides. The incoming tides contribute to an increase in the salinity of the estuarine waters. The volume of plankton collected appears to have some relationship with the nature of the tide, strength of the current and the direction of the flow of water. The distribution and abundance of different groups of zooplankton in the estuary were found not only to follow the tides, but more so the diurnal rhythm. The abundance of zooplankton during night was many times higher than during the day and particularly copepods and veligers showed greater densities during the night.

The fiddler crab Uca crenulata, from California (USA), was exposed to artificial tides in order to differentiate between the influence of a tidal cycle from that of a light-dark cycle on its locomotor activity. Most crabs could be well synchronized by tides, but the activity patterns of other crabs was merely exogenously reinforced. Under constant conditions, after tidal treatment, crabs showed bimodal or unimodal activity patterns. When a 24 h light-dark cycle and a 12.35 h tidal cycle acted as concurrent stimuli, their effectiveness in synchronizing the crabs' activity was variable, depending on the undividual. It is likely that crabs which tend to exhibit a unimodal activity pattern are more sensitive to a light stimulus, whereas crabs with a bimodal activity pattern respond preferably to the tides. Thus, responses of endogenous activity of U. crenulata to tides and light-dark cycles are similar, suggesting that the basic oscillarory mechanism for circadian and tidal activity may be the same.

The crystalline style disappears from Pacific oysters held out of water, but is completely reformed 1 hour after submergence. The style is secreted and dissolved along its entire length and does not move forward into the stomach. It is renewed every 8 hours in submerged oysters or follows the tidal cycle in tidal localities. The style carries a thin superficial coating of mucus and food particles which travel its length in 50 minutes at 17°C. It is possible that the crystalline style functions by mechanically pressing nutritious particles against the absorptive epithelium of the style pouch and is a substitute for an almost total lack of muscular elements in the bivalve alimentary canal.

This paper provides background information on the effect of tide waves upon the movement of water in the Hudson River estuary. Computations based on records from three continuous stage recorders and current-meter discharge measurements made throughout a tidal cycle show that peak discharge rates in the estuary at Poughkeep-sie may be as great as 500,000 cubic feet per second and that total daily tidal volumes as great as 20 billion cubic feet move in the estuary. Computation of water movement in the estuary requires precise field data and continued efforts are needed to perfect the data-collection system and the computation procedure in order to adequately define water movement in the Hudson estuary.

From the middle of June to the middle of September the germ cells of Mytilus edulis L. and Macoma baltica L. in Passamaquoddy bay mature during the new-moon spring tides and are spawned throughout the remainder of the lunar tidal cycle. The initiation of spawning may be due to increased temperature since the low water of the neaps occurs about midday when the mud flats are heated by the rays of the sun. Mya arenaria L. shows the same phenomenon to a lesser degree from mid-June through August. Yoldia sapotilla (Gould), a deep-water form, has a bimonthly spawning on the spring tides.

Finite-difference methods are developed for the numerical analysis of BOD and dissolved oxygen profiles confined to cases which may be treated as one-dimensional problems. Temporal and spatial variations of hydraulic parameters and sources and sinks of BOD and dissolved oxygen can be incorporated into the models developed. Results obtained by the methods developed compare favorably to the results of available analytical solutions. For estuaries, the methods are applicable to the analysis of the variations of BOD and dissolved oxygen profiles within a tidal cycle. Significant variations of these profiles from those obtained by the commonly used quasi steady-state approach are demonstrated. The spreading which results from the tidal velocity variation is shown to have a significant effect on the BOD and dissolved oxygen profiles. The methods developed should prove useful in studies of estuaries in which the tidal variations are large and the temporal variations in the strengths of the BOD and dissolved oxygen inputs are great.

Daily activity patterns of 50 Trinectes maculatus were monitored in the laboratory under a 15 : 9 photoperiod (light : dark), in continuous dim light. Under L : D there was activity only during the night. In continuous light, the animals were active during the diurnal as well as the nocturnal phase of the cycle. In both L : D and continuous light, peaks of activity corresponded to periods of slack tide in the natural habitat. It is concluded that Trinectes maculatus regulates the timing of locomotor activity with an internal clock phased by the tidal cycle. The relationship of T. maculatus activity to patterns described for other fishes is discussed.

Estuarine dispersion coefficients have been determined from steady state salinity profiles. The salinity gradients can be determined from profiles at various stages of the tide or may be averaged over time intervals. Without the steady state assumption, the dispersion coefficient \ID\dL\N, can be determined by an equation. One weakness of this equation lies in the determination of ΔC/ΔX, which varies within the tidal cycle. A method is developed herein which reduces this weakness.

1. Pisaster ochraceus shows a definite seasonal feeding periodicity, in terms of per cent of the population feeding at one time, dry weight ingested, and in composition of ingested prey. Less than 5% are feeding in January and February; 60% to 80% in July and August. The dry weight ingested varies from about 3 grams per tidal cycle per 100 animals in the winter to about 30 grams in the summer months. Chitons are the principal winter prey, while barnacles and limpets are fed on most often in the summer.2. Cyclic changes in gonad and pyloric caeca size and histological appearance characterize this species. The gonads are smallest in the fall, and grow during the winter to a maximum in the late spring, when spawning occurs. The pyloric caeca size-changes are approximately inverse to those of the gonads. Seasonal histological changes of the oocytes, and storage granules in the pyloric caeca, are correlated with the gross organ patterns.3. Two factors are suggested as explanations for these cyclic phenomena. (...

Daily changes in elevation due to compaction and expansion of the upper 400 ft to 700 ft (122m-214m) of the earth have been recorded. It is suggested that changes in intergranular pressure due to the daily tidal cycle apply and relax elastic stress to sand grains resulting in surface elevation changes ranging from 0.002 ft to 0.010 ft (0.6 mm - 3.0 mm). Variations in rates of water withdrawal from nearby water wells on drilling Island Chaffee substantially increase elevation changes at that location.

The swimming rhythm of Pseudaega punctata Thomson is shown to have dual circadian and tidal components. The rhythm is endogenous, persisting for ten days under constant conditions in the laboratory and has a free-running period of greater than tidal frequency. The swimming activity has a basic semi-lunar rhythm even in the absence of marked differences between the heights of spring and neap tides. The rhythm is phased by exogenous factors such as light and tides but is flexible enough to deal with seasonal variations in day length and the shifting tidal cycle. Chilling weakly-rhythmic isopods re-inforces the rhythm. Control is thought to be neurosecretory, depletion of a neurosecretory product accumulated during a quiescent phase terminating swimming activity. The work is compared with similar studies on the related Eurydice pulchra which fills the same ecological niche in the northern hemisphere.

Spectral and cross-spectral analysis have been applied to two time series of beach data, published by ESSA (Harrison et al., 1968). The first series consisted of seven variables recorded at four-hourly intervals (with hourly value interpolated) and the second of four variables, recorded at high and low tide. In the first set, peaks in the spectrum at the semidiurnal tidal period were prominent for beach slope and breaker height, and in the second set for longshore current velocity, beach slope and sand size. Cross-spectral analysis gave coherence values for all possible pairs of variables; four notably high values occurred in the first set and three in the second. The results of the analysis are summarized in Tables I, II, III and IV which demonstrate the importance of the semidiurnal and diurnal tidal cycle in both process variables and the beach slope response variable. A strong coherence between beach slope, sand size and longshore current velocity shows that they are all affected by the tidal cycle.

The Tanoura fishfarm, located on the southern coast of Syozu-sima in Kagawa Prefecture, has a long bay-mouth stretch (about 560m wide) and is partitioned with double sheets of netting. The water area and its volume are 16.4×104m2 and 166×104m3, respectively, at high tide. In 1965, 46×104 fish (Hamachi, the young of Seriola quinqueradiata) were stocked initially and 42×104 of fish harvested. On the whole, sea water (the upper layer) flows into the farm and from the flshfarm the lower layer flows out through the western half of the netting fence, but the water is little exchanged through the eastern half. Surface currents flowing into the farm through the western half of the netting fence run directly to the interior, but the current through the middle part makes an eastward turn. In the eastern region of the farm the current flows veryslowly. The quantity of sea water exchanged is about 56×104m3 during half a tidal cycle in the neap tide. On the basis of the water exchange rate during the neap tide, it may be estimated that the optimum number of Hamachi stocked in the Tanoura fishfarm amounts to 40×104, late in August, when each Hamachi weighs about 400g. The results are discussed with due consideration given to the growth rates of Hamachi cultured in this farm for the past several years.

In freshly collected Naesa bidentata there exists a clear dependence of respiration rate, measured in sea water, on the tidal cycle, with the maximum occurring at high tide, the minimum at low tide. In specimens that had spent 1–2 days in the laboratory the tidal rhythmicity is less pronounced due to a lowering of the Qo2-values at high tide and at the beginning of experiments. This is interpreted as reflecting differences in nutrition between freshly collected and laboratory specimens.

In tanks containing sediment and sea water Eurydice pulchra Leach has been shown to exhibit a swimming rhythm with maximum activity on the ebb tide. Light suppresses swimming activity in the laboratory. There is a semi-lunar component, and maximum activity was recorded on ‘falling’ spring tides. No activity was recorded in animals collected during neap tides. Swimming behaviour is discussed in relation to migrations up and down the beach associated with the spring-neap tidal cycle.

Repeated transverse profile surveys were made in the summers of 1959, 1960, and 1961 on the Atlantic beach of Sandy Hook, New Jersey. The beach experienced accretion (progradation) throughout early and middle summer at the same time that a summer berm was built. By late July progradation largely ceased, yielding an equilibrium profile closely fixed in position and slope. Superimposed upon the late-summer steady state are rhythmic minor changes in beach profile attending the semidaily tidal cycle in which the swash-backwash zone and breaker zone shift up and down the foreshore. Elevation changes at selected points on the foreshore transverse profile were measured at half-hour intervals using engineer's level, level rod, and steel tape. From accumulated level data, a model cycle was synthesized to represent elevation and form changes at various levels on the beach. As tide rises, a short phase of initial deposition of about 0.02 foot of medium sand takes place near the inner limit of swash. There follows a ...

Salinity in the northern part of the Delta area of Rhine and Meuse is discussed. The initial situation, prior to realization of the Delta Plan, the successive influences of the construction of the dam forming part of the bridge over the Haringvliet and the construction of the Grevelingen dam are described. Isohalines have been drawn depicting the situation in the surface water during 6 phases of the tidal cycle. The isohalines of the water near the bottom at low and high tide, are shown on two further charts. The consequences of the closure of the Volkerak dam are discussed.

Experiments were carried out in a tide model to determine the patterns of zonation of four species of periwinkles under laboratory conditions. Both upper shore littorinids, Littorina neritoides (L.) and L. saxatilis (Olivi), showed the same zonation in relation to the tidal cycle as observed on the shore at Plymouth. In the model, the animals adopted a zone above the level of high water and then remained inactive. L. littoralis (L.) showed the same distribution unless fucoid algae were provided, in which case the periwinkles clustered on them. L. littorea (L.) showed the ability to adopt a pattern of zonation in the model, which was at, and just below, high tide level, but higher than that normally observed on the shore. Time-lapse cinematographic monitoring of the movement of L. littorea in the experimental tank was carried out: movement mainly occurred during periods of submersion, but under varying experimental conditions the number of animals moving was very low. Under normal (12.5 h) and increased (20 h) tidal periods, L. littorea showed a virtually identical pattern of movement. When the tidal period was experimentally decreased to 3 h, however, the periwinkles responded to the increased rate of movement of the water level by increased rates of movement and greater activity: moving water level brings about the initiation of movement of the animals, but it also governs the rate of their movement. None of the four species showed any differences in their pattern of movement or zonation when in complete darkness, or in continuous light. When under continuously damp conditions, L. littorea adopted a slightly lower position in the model, possibly because of the movement of the water layer over the substratum. The survival of L. littorea under conditions of longer emersion than would normally be experienced on the shore indicated that physical conditions directly related to the rise and fall of the tide cannot be the major factors controlling the zonation of these species of Littorina.

1. The emergence times of intertidalClunio-species (Diptera, Chironomidae) are correlated with special tidal conditions in such a way that the immediately following reproduction of the short-lived imagos can take place on the exposed habitat. 2. If the habitat of aClunio-species is situated in the middle tidal region and exposed twice a day by the tidal cycle (T = 12.4 h), a tidal rhythm of emergence with an average period of 12.4 hours may result (example:Clunio takahashii). 3. If the habitat is located in the lower tidal zone, exposed only at about the time of the spring tides, a semilunar rhythm of emergence is expected (examples:Clunio marinus andClunio mediterraneus). These semilunar rhythms are correlated with certain conditions of low tide which occur at the coastal locations every 15 days at about the same time of day. The semilunar rhythm is therefore exactly characterized by two dates: the lunar emergence time (a few successive days around full and new moon) and the diurnal emergence time. 4. According to experimental investigations on the control of the emergence rhythm, the midges are able to determine both dates in advance. 5. Coastal populations differ in their lunar and diurnal emergence times. These differences correspond to the time of low tide which exists at each location during the emergence days of the semilunar rhythm. 6. Crossbreeding between stocks of different populations showed that the differences in diurnal emergence time are gene-controlled.

1. The occurrence of a tidal rhythm in the rate of water propulsion in Mytilus californianus, collected from high and low inter-tidal levels and from a depth of 30 ft. off the shore, and also in M. edulis collected from pilings and the underside of floats, has been demonstrated.2. Such a rhythm is independent of temperature (9 to 20° C.) and persists in the laboratory, in phase with the external tidal cycle, for over four weeks, in continuous darkness, or continuous light or the natural day and night environment.3. No indications of a diurnal rhythm in the rate of water propulsion have been observed.4. A rhythm of similar frequency, but out of phase with local tidal cycle by about 6½ hrs., was observed in M. edulis collected from Barnstable Harbor on Cape Cod and studied at Los Angeles, California, after transporting them by air.5. Some of the east coast mussels were secured in the inter-tidal at Corona del Mar, California, for a week. Examination of their activity pattern after this period, revealed a pr...

Turbulence measurements of scales as small as two inches have been made in the ocean with hot-wire equipment which was especially designed for use in sea water. Observations have been made of the variation of the turbulence spectrum over a tidal cycle in the Strait of Juan de Fuca and of the influence of an underwater obstacle in altering the spectral distribution. A preliminary experiment has been carried out to correlate velocity and pressure fluctuations due to turbulence in the ocean. From the work done to date the specifications for a hot-wire instrument for use in the sea can be outlined. A review of several types of turbulence measuring instruments that have been used in water is included.

Observations were performed to detcrminc the relationship bctwccn the time of maximal pigment dispersion in the fiddler crabs, Uca pugilator and Uca minax, and the tidal events on the beach where the crabs were collcctcd. Uca pugilator obtained from burrows above the high tide mark did not have an overt tidal rhythm but did have 24-hour and 14.8-day cycles of color change. The tidal rhythm was probably suppressed bccausc the crabs wcrc free to leave their burrows at any time, whereas crabs from the intertidal zone can lcavc only when the area where their burrows are located is uncovered by the receding water. Crabs living in the intertidal zone displayed a typical tidal rhythm of color change. The tidal maximum of pigment dispersion progressed across the 24-hour cycle at the usual rate. Analysis of the tidal rhythms of two groups of crabs, Uca pugilator, collected near the high and low tide marks, respectively, rcvealcd that crabs from burrows near the low tide mark behaved as if low tide occurred .for them 9.8 hours later each day than for the high tide crabs. Crabs living near the low tide mark annearcd on the beach 10.1 hours later than crabs living near Lhe high tide mark. As a &ult of these observations the hypothesis was presented that the phases of the tidal rhythm are set primarily according to the time that the area where the crabs live is uncovered by the receding water, and secondarily according to the time required for the arca to drain-so that the saitnd is firm enough to subport holes from the burrows to the surface. A review of the literature concerning tidal and semilunar rhythms of color change has appeared recently (Fingerman 1957a). Brown et al. (1953) published the first report of these rhythms. The fiddler crab Uca pugnax collected in the region of Woods Hole, Massachusetts, where the tides are semidiurnal, would darken by day and blanch by night in accordance with a 24-hour rhythm of color change. Superimposed upon the latter was a tidal cycle that progrcsscd across the 24-hour rhythm at the average rate of 48.8 minutes per day. The tidal rhythm was evidenced by a supplementary dispersion of pigment in the melanophorcs about the time of low tide. A semilunar rhythm was also cvidcnt from analysis of the data. The frequency of this rhythm was 14.8 days, the average interval between days on which the 24-hour and tidal rhythms repeated similar time relations to one another. Marc recently, Brown et al. (1955) showed that Uca pugnax has the endogenous ability to mark off 1 This investigation was supported by Grant No. B-838 from the National Institutes of Ilcalth. periods of solar and lunar day-lengths in the absence of all possible rhythmic external signals. Persistent tidal and semilunar rhythms of color change were observed in the blue crab, Callinectes sapidus, by D’ingerman (1955). These rhythms were similar to those described above for Uca pugnax in spite of the fact that the Cullinectes were collected in the vicinity of New Orleans, Louisiana, a region of diurnal tides. Evidently the “center” of tidal rhythmicity of color change in blue crabs operated on the basis of tides spaced 12.4 hours apart, although the crabs were collected in a region where 24.8 hours was the average interval between successive low tides. In addition to Uca pugnax, tidal rhythms of color change have been observed in Uca pugikator and Uca speciosa by Fingerman (1956). The latter two species were collcctcd at Ocean ‘Springs, Mississippi, where the tides are diurnal. The tidal rhythms of both species wcrc similar to the tidal rhythms of Callinectes sapidus and Uca pugnax. Both the Uca pugilator and

The supposition that the Slack, a river in northwestern France discharging directly into the sea, has a significantly higher chlorinity in its bottom sediments than in the overflowing river water, is confirmed. A device to take samples of sediment from the river bottom has been constructed and is described in this publication. To obtain the interstitial water, the sample is simply centrifuged. A peculiar phenomenon, which could not be explained, is that after a regular decrease of the interstitial chlorinities, a considerable increase (to > 1.5 ‰) takes place at a distance of some 2½ kilometres from the mouth. The interstitial chlorinity in the estuarine part of the river proved to be almost constant, regardless of the tidal cycle.

A preliminary investigation into the effect of wind on shore gastropods has been undertaken. Moderate winds displace some Monodonta lineata (da Costa) from boulders on the shore and some individuals detach within six hours in weaker winds in the laboratory (5–10 km/h, 10°C, 94% humidity). Sheltered aspects of the rock are used to minimize the effects of the wind on shores, and maintenance movements on the shore are extensive. Summary: In calm conditions and in light winds Monodonta lineata is more widely dispersed about the rocks than in moderate winds when the animals are either sheltering in cracks or displaced. Providing the rock surface is damp then animals continue to move about during emersion in light winds. On a small boulder beach animals moved as much as 4 m upshore during one tidal cycle. Only slight reorientation movements were recorded during moderate winds. Animals withstand a windspeed of 4 km/h for six hours in a wind tunnel in a humidity of 94% at 10°C, but are displaced within an hour by 10 km/h winds in similar conditions.

Two-dimensional trend surface analyses were performed on areally distributed tracer-concentration data for three different fluorescent sand tracers recovered from four depth intervals of the foreshore. The tracers had been affected by the swash, breakers, and longshore currents of one tidal cycle. Analysis of the statistical significance of trend surfaces for each depth interval showed that only the upper 2.5 cm. of the sand column evidenced definite trend components. Differential sorting of tracers of different shapes and mean grain sizes was probably negligible, as deduced from the similarity in direction of orthogonals to the trend surface contours for the various tracer data. The advantage of the trend surface method of describing sand movement patterns on beaches lies in its ability to represent, in an objective manner, the average movement of sand grains by means of a single representative equation. Furthermore, for time scales of the order of minutes to several hours, the motion of sand is seldom p...

Determination of the time history of water temperature in an estuary is accomplished by using a thermal quality model in conjunction with a hydrodynamic simulation model. The hydrodynamic model computes tidal stages and flows throughout the estuary for any tidal cycle. The thermal quality model uses the results of the hydrodynamic model and observed meteorologic data to predict water temperatures. These models have been used successfully in case studies to reproduce observed water temperatures. The sensitivity of the resulting temperatures to the various meteorologic parameters, such as wind conditions, dew point temperature, and solar radiation, is presented. Dew point temperature is shown to exert a major influence on water temperature.

The ash weight of material suspended in the waters of the Menai Straits was measured twice weekly between May 1962 and May 1963. The amount was much greater in winter than in summer and greater during spring than during neap tide periods. No differences could be detcctcd between the ebb and flood periods within a single tidal cycle. The variations in ash weight correlated strongly with temperature but not with rainfall. There was a significant correlation between ash weight and the temperature-related variables, ut and estimated freshwater runoff, but neither was significant after the effect of temperature was eliminated. The suspended burden was greater during periods of easterly winds, but no relationship could be established with wind velocity. The seasonal changes could not be attributed to changes in thermal instability or viscosity, The variations are thought to be caused by biological rather than by physical processes.

A facultatively autogenous population of Culicoides marmoratus (Skuse, 1889) was abundant at Deception Bay, 40 km north of Brisbane. Truck trapping and collections using bait animals were more effective methods of collection than light trapping. Population levels were depressed considerably in July when crepuscular activity was limited to evenings. The time of adult emergence shifted seasonally in relation to the tidal cycle. This shift was related to the duration of the ovarian cycle in winter and summer conditions. Abdominal pigmentation was permanent once developed. This provided and reliable criterion for age grading C. marmoratus. Pigment development, digestion and follicle maturation progressed, with few exceptions, synchronously with time. C. marmoratus in this area would be a poor vector of disease owing to its low estimated daily survival rate.

Fiddler crabs inhabiting the intertidal zone must adapt their activity to both the day-night cycle and the cycle of the tides. The tidal cycle imposes on the animals a rhythmic alternation between terrestrial and marine periods of existence. At the same time the crabs are influenced by the day-night cycle, since they exhibit specific diurnal and nocturnal habits. Moreover, the interaction of daily and tidal rhythms may give rise to semi-monthly variations in activity. It is now well established that persistent daily and tidal rhythms in physiological processes underlie rhythmic variations in the behavior of crabs in the field. The present paper reviews more recent studies, which have compared the persistent rhythms in crabs from different tidal and non-tidal regions. Rhythmic patterns recorded in the laboratory are found to be closely correlated with tidal conditions in the native habitat of the crabs. It has also been shown that the persistent pattern can be modified by transplanting crabs to the intertidal zone of another coast where they are exposed to tidal cycles which differ in form from those in the original habitat.

The semi-enclosed nature of Long Island Sound makes it ideal for surface and sea-bed drifter studies. A U.S. Coast Guard H-3 helicopter provided a “synoptic” launch within a half tidal cycle. Drifter releases were conducted on 18 June 1973 at a total of 50 stations in Long Island and Block Island Sounds. Drops were made at various altitudes and speeds in order to determine optimum release conditions.

Mechanical tide-generators have a shaft which rotates in synchronism with the tidal cycle and which can be used to operate auxiliary equipment. Modern tide generators controlled from a graph of the desired tide have no synchronized shaft, and auxiliary equipment is then conveniently operated by changes in the water level. A device for injecting solid material, and a system for time lapse cinephotography are described, both controlled by water level. The use of a "surplus" aircraft camera for routine still photographs is also described.

Detailed echo sounding along a fixed transit off Avonmouth (England) has proved that sand waves reverse their orientation during the tidal cycle.

A multiple strain-gage system was field tested as in situ submarine instrumentation for monitoring diurnal beach sediment migration in high-energy foreshore environments. The system has major quantitative limitations in measuring absolute sand heights, but does have potential utility as a qualitative instrument for the synoptic monitoring of tidal-induced erosional and accretionary trends. Relatively long-period trends exceeding one-quarter of a tidal cycle are effectively denoted by gage response pressure. However, gage response to shorter period sand-height variations is of more limited reliability because of extraneous pressures induced by the hydraulic regime.

Source: https://erdc-library.erdc.dren.mil/jspui/ Velocity, depth, temperature, grain size, and bed form scale and orientation were measured for complete tidal cycles at 50 stations in two New England estuaries. Scuba observation of bed form change and migration, fathometer profiles, and 700 bed form scale and orientation readings were also carried out. This investigation led to the recognition of a sequence of bed forms based on increasing "flow strength." Bed form type is governed by maximum flood and ebb velocities (Umax) attained at a given locality. Velocity asymmetry and duration are important in determining bed form morphology and amount of crossbedding bimodality. Froude number (Fr) shows good correlation with bed form type only in depths less than 2 meters. In the intertidal and shallow subtidal (2 meters MLW) areas, sand waves are the principal bed form. They show no dominant orientation. However, where Umax exceeds 80 centimeters per second, megaripples are superimposed on the sand wave form and crossbedding is complex.

A small quantity of Rhodamine WT dye was injected at the headwater of the Muddy Creek estuary and concentration of the dispersed dye was measured with a uniform time interval at a number of fixed locations in the lower portion of the estuary. By the use of the superposition principle of a linear system, the builtup concentration of the dye is found to range from 8 ppb at 1,900 feet downstream from the confluence of the north and south forks of Muddy Creek to 2 ppb near the Smithsonian Institution’s pier in the Rhode River, provided that the dye is continuously injected at the headwaters at the rate of one pound per two tidal cycles.

A study involving the determination of the bed shear stress and thence shear velocity in the Narrows of the River Mersey (a well mixed tidal estuary) is described. The two dimensional equation of motion is examined and it is concluded that in order to determine the energy slope (S) (and thence the shear stress and shear velocity) it is essential to evaluate density, inertia and kinetic energy terms as well as surface slopes. Although the density term is much smaller than the other terms it is important at periods of low slack-water. Measurements of the various terms are described and attention is drawn to the difficulties arising m the case of the surface slopes. Comparison is then made between the values of the shear velocity as predicted from the energy slope and those obtained using velocity traverses throughout the depth and with measurements of velocity at three fixed positions near to the bed. Finally consideration is given to the relationship between the cross-sectional mean velocity (U), the depth-mean velocity (U) and velocity at 3ft. above the bed (U,) and the shear velocity obtained from the energy slope. It is concluded that there is good linear correlation of each of these velocities (U, U and U ) with the shear velocity throughout the tidal cycle except for the period around low slack-water.

Radiographic examination of cores taken at the entrance of a Georgia tidal inlet revealed three texturally and structurally different types of mud layers. Type I mud layers are composed of laminations of day-size detritus that occur as flaser, wavy and lenticular bedding. Type II mud layers are composed of foresets and sand-size fecal and organic detritus that also occur as flaser, wavy and lenticular bedding. Type III mud layers are composed of foresets of mud pebbles and occur as wavy lenticular bedding. Mud-layer types form in response to hydraulically different depositional processes combined with the local availability of mud-grain sizes. Examination of textures and structures in these mud layers indicates that grains which constitute mud layers are transported and deposited from the traction load as well as the suspension load. In some areas, deposition from the bedload (traction load)is considerably more pronounced than deposition from suspension load. Type II and III mud layers result from bedload deposition which does not necessitate a period of slack-water in the tidal cycle or a specific set of conditions of wave activity, suspended-matter concentration, and current velocity.

Numerous marine organisms show rhythms in their behaviour, coinciding with the cycles of high and low tide; but they also continue under laboratory conditions. Bohn (1903) found that green flatworms (Convoluta) come to the surface of the sand during high tide, and at low tide they bury themselves into the sand as it dries. This rhythm also continues in an aquarium without the tidal cycle. We may further refer to the investigations by Bracher in Euglena limosa, by Faure-Fremiet in Chromulina and in the diatom Hantzschia.

This study is concerned with a 29km long barrier island system along the New Brunswick coast of Kouchibouguac Bay. Over the past 150 years these islands have been retreating shorewards and have been affected by storm wave action. The changes in the island configuration, the characteristics of the island topography and the seasonal variations in the beach profile suggests that these islands are similar to better known ones along the United States coastline. The sediment characteristics of these islands reveal that there is an interplay of wind and wave processes on the sands, an interplay that is constantly mixing beach, dune and lagoon sands. The dominant southwest winds in summer cause most of the beach and dune sands to take on the characteristics of wind affected sands while the fall and spring storms impart characteristics of wave deposition to the beach sands at these times. The sediment characteristics revealed seasonal changes in the islands but simulation modelling of the energy distribution of waves in the bay after wave refraction accounts for most of the long term change in the island configuration. This modelling emphasizes field work which revealed that not all parts of the islands are affected by the same storm waves. Nort-northeast waves have a better chance of affecting the southern part of the bay while more easterly approaching waves will only influence the northern part. Over a period of time form 1894 to 1964, wave refraction modelling also shows that much of the change in the configuration of South Beach can be accounted for by wave refraction over a changing offshore bathymetry. Storm wave action thus accounts for most of the change in island configuration but the change around the inlets is most likely dependent upon the ability of these inlets to maintain stability at all times. Richibucto Inlet has achieved a stable equilibrium between the strength of the tidal currents passing through the inlet and the amount of incoming longshore drift, so that its position has remained static over the last 30 years. It is unlikely that Blacklands Gully or Little Gully have achieved this stability. Thesis Master of Science (MS)

This report presents the results of a fluorescent-dye-tracing study to determine the concentrations of a pollutant that would be present in the Northeast Cape Fear Estuary at various rates of continuous waste injection and freshwater inflow. Rhodamine WT dye was introduced into the estuary at a constant rate over a 24.8-hour period (two tidal cycles) at a point 6.4 miles upstream from the mouth in Wilmington, N.C., and concentrations were monitored at several selected sections in the tide-affected part of the river for 17 days. Th Q range between high and low tide in this reach of the estuary averages about 3.5 feet, and there is usually strong flow in both directions. Results of the dye study indicate that if a pollutant were injected at a rate of 100 pounds per day under the conditions of relatively low inflow existingat the time, concentrations would ultimately build up to 20 micrograms of dye per liter of water 1,000 feet downstream. The flushing time during the study is estimated to be 17 days. These results are extrapolated to include periods of lower or higher inflow. For example, at average intervals of 10 years, it is estimated that inflow is so low that 100 days are required for a pollutant to travel the 6.4 miles from the point of waste release to the mouth of the river. Under these conditions it is expected that 1,000 feet downstream from the point of waste discharge, daily maximum concentrations will average about 130 micrograms per liter for each 100 pounds of pollutant injected per day. Results of a continuous discharge measurement of flow made by current meter during a complete tidal cycle are presented as a part of this report. Data from this measurement and other evidence indicate that net upstream flow in the estuary is possible over a period of several days.

Arrangements of dams, sluices and turbines, and principles of operation for various simple or complex power generation cycles have been extensively described 1,2,3). In these introductory paragraphs it is sufficient to summarize the most significant features of those few systems which at present offer any prospect of commercial importance.

Short‐term and long‐term fluctuation studies have been made in the BIFI Shallow X, Water Acoustic Range, which is 37 kyd in length. It is shown how time‐smear analysis may be used to predict the extent of short‐term signal fluctuation by taking into account the energy content of the “front” and “tail” of the received signal. The method is applied to an actual received signal with good results. Long‐term fluctuation, such as that due to tide, is considered in terms of normal mode theory, using the results of the time smear analysis to provide an estimate of the relative strengths of the modes. When applied to the BIFI range this method predicts that tidal effects will cause negligible fluctuations in the received signal, due to the absence of modes other than the fundamental at this large range. This prediction was verified by experiment. At shorter ranges, the interaction of several modes will cause relatively large fluctuations in the signal as the water depth changes during the tidal cycle.

IN a previous communication on the behaviour of elvers in the Dutch Wadden Sea1 it was pointed out that the animals most probably use the tidal streams for their migration from the open sea to inland water. They are carried inward by the flood at higher water levels, and go down to the bottom during the ebb tide so that they are not carried back seaward. This means that elvers should be able to discriminate between ebb and flood tide. The suggestion was made that this discrimination was based on changes in salinity during the tidal cycle.