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Europa likely has an active surface ice shell producing numerous low-magnitude (

The expression of individual behaviour as a function of environmental variation (behavioural plasticity) is recognized as a means for animals to modify their phenotypes in response to changing conditions. Plasticity has been studied extensively in recent years, leading to an accumulation of evidence for behavioural plasticity within natural populations. Despite the recent attention given to studying individual variation in behavioural plasticity, there is still a lack of consensus regarding its causes and constraints. One pressing question related to this is whether individual plasticity carries over across temporal and environmental gradients. That is, are some individuals more plastic (responsive) than others in general? Here, we examined the influence of temporal and environmental gradients on individual behavioural responses in a marine gastropod, Littoraria irrorata. We measured individual boldness repeatedly over time and in response to tidal cycle (high vs. low, an index of risk) and daily temperature fluctuations (known to affect metabolism), in a controlled field experiment. On average, boldness increased from high to low tide and with increasing temperature but decreased marginally over time. Individuals also differed in their responses to variation in tide and temperature, but not over time. Those which were relatively bold at high tide (when predation risk is greater) were similarly bold at low tide, whereas shy individuals became much more "bold" at low tide. Most notably, individuals that were more responsive to tide (and thus risk) were also more responsive to temperature changes, indicating that plasticity was correlated across contexts (r = 0.57) and that bolder individuals were least plastic overall. This study provides a rare and possibly first example of consistency of individual behavioural plasticity across contexts, suggesting underlying physiology as a common mechanism, and raises the possibility of correlational selection on plasticity.

Atlantic sturgeon Acipenser oxyrinchus surfacing behaviour was investigated in Minas Basin (45° 20' N; 64° 00' W) and the Bay of Fundy with pop-up satellite archival tags (MiniPAT) measuring physical variables (pressure, temperature, light). Of six tags deployed during June and July, five provided pop-up locations and two were recovered after c. 4 months. Analysis of recovered archival data revealed that the frequency of surfacing events was highest (78·9%) when A. oxyrinchus were in Minas Basin at depths 40 m). The tidal cycle in Minas Basin had a significant relationship to surfacing frequency, with the most surfacing events (49·5%) occurring on the flood tide, from mid- to high-tide. Surfacing events ranged from 0-12 a day and the maximum number occurred between 2300 and 0300 hours. Maximum surfacing ascent speeds ranged from 0·50 to 4·17 m s-1 and maximum descent speeds ranged from 0·17 to 3·17 m s-1 . Buoyancy control, by gulping air to inflate the gas bladder, is proposed as the main reason for surfacing behaviour in A. oxyrinchus.

This work shows statistical evidence for lunar nodal cycle influence on the low-frequency summer rainfall variability over the plains to the east of subtropical Andes, in South America, through long-term sea surface temperature (SST) variations induced by the nodal amplitude of diurnal tides over southwestern South Atlantic (SWSA). In years of strong (weak) diurnal tides, tide-induced diapycnal mixing makes SST cooler (warmer) together with low (high) air pressures in the surroundings of the Malvinas/Falklands Islands in the SWSA, possibly through mean tropospheric baroclinicity variations. As the low-level tropospheric circulation anomalies directly affect the interannual summer rainfall variability, such an influence can be extended to the bi-decadal variability present in the summer rainfall owing to the nodal modulation effect observed in the tropospheric circulation. The identification of the nodal periodicity in the summer rainfall variability is statistically robust.

This work was financed by the Portuguese Foundation for Science and Technology (FCT) through a Post-Doc grant to J.P. Coelho (SFRH/BPD/48449/2008) and P. Pato (SFRH/BPD/35068/2007).

SUMMARY The average numbers of Herring Gulls Larus argentatus present in a breeding colony on Walney Island, Cumbria, were found to vary with the tidal cycle but to remain effectively constant with time of day through the breeding season. An activity survey, based on 50 Herring Gulls observed at half-hourly intervals during March and April 1973, showed that sleep and rest varied inversely with each other with sleep increasing to 50 per cent at midday. After a peak in the proportion of gulls asleep four hours before low tide, sleeping progressively decreased until low tide; seemingly a result of resident gulls waking and remaining more alert as others left the colony in search of food. Preening was constant throughout the day and tide cycle. Other behaviours (mostly courtship and agonistic behaviour associated with territory defence) increased slightly during low tide and were more common early and late in the day. Night observations of the gulls' activities showed that there was a peak of sleeping between midnight and 02.00 hours. It is suggested that Herring Gulls have a bimodal diel sleep pattern.

Deposit feeding in the coastal epibenthic mudsnail Hydrobia ulvae, as estimated by egestion rate, varies in relation to the tidal cycle. In nature, feeding is maximal when the snails are covered by tidal water; after exposure, feeding reduces slightly but significantly whilst the sediment surface remains damp; and it is minor or ceases whilst the snails are buried in pits in the drying sediment. Within each of these three phases, however, egestion rate remains unchanged both in relation to phase duration, and with temperature over an ambient range of 18–30 °C (mean 24 °C). These findings form another example of disagreement between field and laboratory results on feeding in Hydrobia.

The main aim of this research was to assess the mercury transport from an estuarine basin with a background of anthropogenic contamination during a spring tidal cycle (year 2009) and compare it with two previous tidal cycles (years 1994 and 1999), as part of a long-term monitoring program. Results showed that effective mercury transport occurs both in the dissolved and particulate fractions (0.18 and 0.20 kg per tidal cycle, respectively), and despite an overall decrease in environmental contamination, results more than double previous findings on particulate transport in the system. These findings result essentially from changes in the tidal prism (net export of 2 million m3 of water), given that both dissolved and particulate concentrations did not increase over time. Hydrodynamic simulations were performed to evaluate the effect of physical disturbance (dredging) and weather events (increased freshwater flow) in these processes, and results suggest the increased freshwater flow into the system as the main forcing function for the mercury transport increment. These results highlight the importance of long-term monitoring programs, since despite an overall improvement in local contamination levels, the enhancement of transport processes through hydrological changes increases environmental pressure away from the contamination source. This work was financed by the Portuguese Foundation for Science and Technology (FCT) through a Post-Doc grant to J.P. Coelho (SFRH/BPD/48449/2008) and P. Pato (SFRH/BPD/35068/2007).

The behaviour of Magellanic Penguins Spheniscus magellanicus commuting between their foraging areas and breeding areas in San Julian Bay, Argentina, was studied to examine whether tidal rip currents affected travelling patterns. Although there was no apparent relationship between departure and arrival patterns and the state of the tidal cycle, birds travelling against the current dived for longer periods and a shorter rests on the surface than birds travelling with the current. In addition, bird swimming against the current hugged the banks of tidal rivers much more closely than did birds swimming with the, thus, reducing the magnitude of the current against which they had to swim. In cases of extremely high current speeds, birds travelling upstream walked. Models regarding the energetics of movement indicate that the strategies adopted by Magellanic Penguins can result in substantial energy savings. Fil: Wilson, Rory P. Institut fur Meereskunde; Alemania Fil: Locca, R.. No especifíca; Fil: Scolaro, Jose Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Frere, Esteban. Universidad Nacional de la Patagonia Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gandini, Patricia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia Austral; Argentina

The plant and sediment dynamics in salt marshes are strongly interrelated, but few data are available to document their interaction. Puccinellia maritima is a perennial grass that occurs widely in salt marshes and this study examines its role in the stabilization or trapping of sediment in the pioneer zone and its response to burial, a characteristic phenomenon in accreting salt marshes. Puccinellia not only appears to limit erosion but also to significantly enhance accretion. The functional role of this species is largely dependent on the local disturbance regime. The response of Puccinellia to burial was studied in a series of burial treatments. Growth performance of Puccinellia was stimulated by burial of 4 mm sediment and reduced by burial of 8 mm/month. Burial under 12 mm of sediment led to high mortality of up to 97%. Response was determined by the instantaneous thickness of sediment rather than by the total quantity. Morphological response to burial consisted mainly of stem elongation. Plants collected from accretion zones in the field also produced tillers with adventitious roots at successive soil layers. The range of burial tolerances found for Puccinellia fits well with its occurrence in locations with up to 8 mm sediment accretion per tidal cycle, a common situation in the salt marsh studied.

This paper describes the pattern of daylight occurrence of humpback dolphins Sousa chinensis in Algoa Bay, the Eastern Cape, South Africa, between May 1991 and May 1994. Two indices, the Sighting Index (SI) and the Total Recorded Dolphin Presence (TRDP), were used to quantify the dolphins' daylight occurrence. Humpback dolphins display a clear pattern of daylight occurrence in Algoa Bay and can be seen mostly in the morning, and, to a lesser extent, in the evening. This pattern varies little between seasons (with possible exception for the evening hours), follows the time of the solar day, is not related to the tidal cycle and is probably governed by the diurnal cycles of dolphins' prey.

Truck trap collections of Ceratopogonidae were made over a period of 27 months (November 1973-February 1976) at Tingalpa Creek, in southeast Queensland, Australia. Six collections were made on each of 95 days, giving 570 observations and a total of 29,378 Culicoides. Two collections were made before, one at, and three after sunset. Separate analyses were made of the catches of thirteen entities: male and female C. austropalpalis, C. brevitarsis, C. marksi, C. marmoratus and C. victoriae, female C. henryi and C. longior, and total C. bundyensis. Catches were dominated by C. brevitarsis (35.2%) and C. marmoratus (32.3%) and, with C. victoriae, were taken on almost every collecting day over all seasons. Sex ratios (M:F) varied from 0:100 for C. longior to 130:100 for C. marksi. Collections of all entities, except female C. henryi, were greatest (50-70% of the daily catch) at sunset. In winter there was substantial activity in the hour before sunset. Time of day was the most important variable, accounting for 15-45% of the observed variation. Between-day differences were significant for all except C. austropalpalis, C. victoriae and male C. marksi. Culicoides brevitarsis, C. bundyensis and C. longior had highly significant annual cycles, C. victoriae and female C. austropalpalis had significant lunar cycles, and C. longior had a significant tidal cycle. Logarithms of catches of female C. austropalpalis, C. brevitarsis, C. henryi, C. marmoratus, and female and male C. victoriae were inversely related to linear wind speed. Log catches of female C. austropalpalis, C. brevitarsis, C. marmoratus and C. victoriae, and male C. marksi and C. victoriae were positively related to temperature (quadratic).

Common snook Centropomus undecimaliswere sampled monthly from the Jupiter–Lake Worth area of Florida's Atlantic coast during 1989 and 1991 (1452 fish) and from Tampa Bay on Florida's Gulf of Mexico coast during 1988 and 1989 (2090 fish). Group-synchronous oocyte development was demonstrated. Ovarian maturation began during March or April on both coasts. Spawning was first detected histologically in April during 1989 and 1991 on the Atlantic coast and during May in 1988 and in April in 1989 on the Gulf coast. In each year, spawning ended during October on the Atlantic coast and during September on the Gulf coast. Ovarian histological evidence suggested that individual females may spawn every 1·1–2·5 days between 1400 and about 2000 hours. Final oocyte maturation occurred independently of either tidal cycle or lunar phase, and some common snook were observed in prespawning or spawning condition on every day sampled. Spawning occurred in or near major inlets to the Atlantic Ocean and the Gulf of Mexico, in secondary passes to larger inland bays and bayous, and around nearshore islands.

Tidal fluctuation is shown to affect the piezometer readings taken in a nearshore aquifer around a working nuclear power station. Continuous monitoring of a network of 40 piezometers provided relations between the tidal cycle and the piezometer readings. These relations can be expressed in terms of a time lag and amplitude scaling factor. Using these parameters, tidal interference was filtered from the day-to-day piezometer readings. The early detection of ground-water drawdown below the working station caused by construction of a new nuclear power station on an adjacent site could thus be achieved. In parallel with the field work, the theoretical relationship between the tide and piezometric response was shown to be of the same form as that observed in the field. Values of the aquifer characteristics could then be deduced and compared with those measured in conventional pumping tests. The transmission of the pressure oscillation is shown to be faster in areas of higher permeability and in the deeper parts of the aquifer. This second effect is thought to be caused by the presence of the phreatic surface.

Nearshore water circulation and bar patterns at Coledale, New South Wales, were surveyed daily over thirty-six consecutive days, from 3 November to 8 December 1978, to identify sequences of changes that might occur in response to spring-to-spring tide cycles of fourteen days, changing barometric and wind conditions associated with the passage of anticyclonic weather systems across the coast, and day to day variation in the nearshore wave regime. During the survey the bar patterns tended to vary from transverse bars, through a composite arrangement incorporating longshore and transverse bars, to a longshore bar pattern as the tide changed from its spring to neap tide phase. However, this sequence was too brief to unequivocally establish variations in nearshore bar pattern that might be attributed to the fourteen day, spring-to-spring tide cycle. Nevertheless, morphologic changes occurring in response to wave regime fluctuation at Coledale were broadly in accord with studies from elsewhere by Dolan et al. (1979, 1982), and Clarke and Eliot (1982, 1983) in that bars and rips were systematically distributed along the beach. At Coledale, bars tended to relocate approximately 0.4 and 0.75 of the distance along the beach from its southern end. The preferred bar spacing closely matches hypothetical standing waves trapped between the headlands of the Coledale embayment. Temporally, the nearshore morphology is highly responsive to wave regime changes such that, as primary breaker heights decrease and remain below Hmax=1.0m, the bar pattern changes from longshore through mixed to transverse bar patterns within three to five days. On one occasion the bar pattern switched from a longshore to a transverse bar pattern within twenty-four hours.

An infiltrometer has been designed to measure infiltration and exfiltration in intermittently or continuously inundated soils, such as occur in tidal salt marshes. The device isolates a column of water while actively maintaining natural head conditions, and yields infiltration/exfiltration rates from mass balance considerations. It incorporates a Stevens recorder, a reversible positive-displacement metering pump, and solid-state circuitry. It can detect

The biology of young grey mullet, Mugil cephalus L. populations of a coastal lagoon—the Negombo Lagoon on the West Coast of Sri Lanka was studied from October 1976 to March 1978. The relative abundance of fry were found to vary from month to month, with peaks occurring in December-January, May and September-October, coinciding with the end of rainy seasons. It was found that the young fry tended to migrate into the lagoon at a size of about 10–20 mm, most frequently between 15–20 mm in length, by which time they were fully scaled. The young fry after a period of growth in the shallow areas of the lagoon, when they reached a size of 30–35 mm, emigrated into the deeper waters of the lagoon. The rate of growth, as computed from length frequency distribution studies, was found to be around 0.24 mm day−1. Results of diurnal surveys showed a movement of the larger size fry into shallower waters during the hours of darkness and this movement appears to be independent of the tidal cycle. It is postulated that the cause of this migration is to escape from predators, chiefly piscine. Investigations of the meristic characters indicated that the young fry which migrated into the lagoon at different times of the year probably originated from a single spawning stock.

Series of aerial photographs taken with an interval of 6 Minutes were used to study the dynamics of the suspended matter distribution in a 1 km section of the Elbe Estuary. The observations show heterogeneous distribution patterns which are different at each phase of the tidal cycle. The comparison with the bathymetry indicates that the distribution is mainly a function of the river bed topography, which modifies the local current structure. The surface distribution in the fairway region is especially determined by the ship traffic.

A tidal-powered compositing water sampler has been designed to operate over a wide range of tides. It can sample water over long periods without attention and can be made from inexpensive hardware components and two check valves. The working principle of the sampler is to use the reduction of pressure by the falling tide and the stored pressure from the previous high tide to pump water into a collection bottle. The sampler can produce a constant volume of water per tidal cycle over a tidal range of 2 to 4 m.

A series of flume runs using a 12·5 h tidal cycle was conducted in order to determine whether or not flaser beds could be formed in nearshore subtidal areas as a result of purely tidal activity. The effects of clay composition, sand size, bed thickness, and maximum current velocity were investigated. The resistance to erosion of mud beds 10 mm thick or less is low; shear stresses approximately equal to those needed to initiate sand movement resulted in rapid erosion of the mud beds. In the light of the low resistance to erosion of the beds, and the necessity for increased thicknesses and very long time periods for their resistance to be increased substantially, it is concluded that the formation of these beds is unlikely to result from purely tidal action unless very large amounts of mud are available. A mechanism which more readily permits the deposition of thicker beds and longer consolidation times, such as storm action, is preferred.

Since the late 1960s there has been a large mudslide in coastal cliffs of Permo-Triassic strata (conglomerate overlying mudstone) at West Down Beacon, 2 km west of Budleigh Salterton, Devon. A total displacement of 100 m was achieved between 1981 and 1985 as the lobate toe of the mudslide pushed forward across the beach in eleven surges of movement. Each surge involved a displacement of between 5 and 15 m and was completed within a few hours. The toe moved by planar sliding, possibly on more than one seaward-dipping shear surface or zone. Occasionally there were additional relatively minor displacements (less than 1 m), but normally the mudslide was stationary between the major surges. After each surge high-oblique aerial photographs were obtained for stereoscopic interpretation. Debris falls from the cliff appear to have triggered some of the mudslide surges. A displacement recording of one surge has indicated that the rate of movement of the mudslide may have been partly controlled by variations in sea level during the tidal cycle.

Continuous, detailed records of marine gravel transport have been obtained acoustically and compared with bedload transport rates (qb) predicted by five bedload transport equations using measurements of the near-bed turbulent current flow. When mean flow data are used in these equations, total qb estimates are similar to those measured. However, when instantaneous flow data are used, total qb is over-estimated by approximately one order-of-magnitude. Based on the acoustic measurements, an empirical equation has been obtained that gives accurate estimates of total qb over a tidal cycle and simulates well the intermittent characteristics of marine bedload transport.

Two closely related killifish, Fundulus grandis of the Gulf coast and F. heteroclitus of the Atlantic coast, were held under standard laboratory conditions and monitored for spawning activity. Daily egg collections for 4–5 months during summer revealed semilunar cycles of spawning activity in both F. grandis (three aquaria) and F. heteroclitus (five of six aquaria). The mean periods were near 13.7 days for F. grandis and near 14.8 days for F. heteroclitus. The shorter duration in F. grandis closely approximates the tidal cycle in the Gulf of Mexico, which is an expression of the declinational cycle of the moon (tropical month: 27.3 days). The longer duration in F. heteroclitus closely approximates the tidal cycle along the Atlantic coast, which, along with the moonlight cycle, is an expression of the synodic month (29.5 days). Unless the fish respond to subtle exogenous cues that can influence spawning under isolated laboratory conditions, these results indicate that both killifish have endogenous cycles with very precise periods. These cycles free run for several months in specific phase relationships with tidal (F. grandis) and tidal/moonlight cycles (F. heteroclitus) present in their respective natural habitats.

The fluctuations of aerobic, heterotrophic bacteria, particulate organic carbon (POC), and adenosine triphosphate (ATP) in the water system of a salt marsh were investigated at two marsh creeks. Both reached maximum densities of bacteria just before low tide. In a typical study, however, the mean concentration at station 1 over a tidal cycle was an order of magnitude greater than at station 2. POC increased twofold to fourfold during ebbtide in both systems. ATP concentrations at station 2, during ebbtide, increased about fourfold, and the fraction of the total carbon regarded as “living” ranged from 2–24%.

Seepage flux can be measured and samples of groundwater flowing into lakes and estuaries collected by enclosing an area of bottom with a cylinder vented to a plastic bag. The method has the advantage of not requiring measurements of permeability of bottom sediments. Seepage velocities from −0.1–2.58 µm s−1 were measured in Minnesota and Wisconsin lakes and in Nova Scotia and North Carolina estuaries. Where seepage inflow was rapid (0.4–0.8 s−1), water collected with the seepage meter was chemically similar to water from wells on the same flow path, and the distribution and chemistry of the seepage concurred with a theoretical flow net. The rate and direction of seepage flux were correlated with water surface elevation during a tidal cycle.

Tidal variability of water mass characteristics has been assessed in the upper 100 metres of the Saguenay, a subarctic fjord in Quebec, Canada. Temperature and salinity show a maximum variability in the 5-15 m layer in which vertical oscillations of a very sharp pycnocline are observed. Phosphates, nitrates and chlorophyll a are highly variable above this pycnocline during a tidal cycle, but dissolved oxygen content is remarkably stable in the whole water column. It is concluded that fluctuations of many variables in the subsurface waters might be large enough to hinder high rates of primary production.

Ultrasonic telemetry was used to follow the movements of two groups of smolts in the estuaries of two small Scottish rivers. Hatchery reared smolts released into a typical wedge flow, partially mixed estuary had movements which were dominated by the influence of tide on the direction of water flow. The net movements of wild native smolts in a two layer flow estuary, in which freshwater flow dominated, was downstream but were intermittent consisting of short steps and numerous long pauses. The hatchery reared smolts escaped from the estuary within a tidal cycle, moving out on an ebb tide. The wild smolts remained in the estuary for periods up to 108 h, none escaping within one tidal cycle.

The total phosphate content of the water in a well delimited region of the Wadden Sea (26.8 km2) was determined by multiplying the concentration by the water volume during each phase of the tide. When the weather is moderate, sharp but stable gradients are observed from the shore to the open sea resulting from the remineralization processes that occur most rapidly near the shore.

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.

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

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.

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.