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Despite sea turtles in Papua New Guinea being culturally important and heavily harvested, no in-country density estimates have been previously established. We provide the first estimates of sea turtle density in Papua New Guinea from two locations around Mussau Island where turtle consumption is banned due to religious beliefs. We obtained density estimates using a low-cost, in-water distance sampling method. Our monitoring shows that the island has a high density of sea turtles (almost exclusively Chelonia mydas). At Lolieng, a site with a steep reef drop off, we recorded a mean of 7.4 turtles ha−1 (s.d. = 2.6) at the reef crest during low tide (across all sampling occasions), which is comparable to high density sites globally. By comparison, we recorded a much lower estimate of 1.1 turtles ha−1 (s.d. = 0.4) at Nae, a site with an extensive, low profile reef system. Additionally, our modelling shows that tidal cycle is an essential covariate for assessing sea turtle density for in-water distance sampling. We advocate that Papua New Guinea needs to invest in long-term monitoring at a national scale to track the sustainability of this important cultural resource, and that in-water distance sampling is a low cost monitoring method that potentially could be used for this purpose albeit subject to certain caveats.

This study analyzed the reproductive cycle of Chiton virgulatus and its relationship with air temperature (AT) sea and surface temperature (SST), photoperiod, and tidal cycle (TC) in Bahía de La Paz, in the coast of the Gulf of California. Monthly samples were collected from September 2008 to September 2009. The parameters recorded included total length, total weight, and gonad weight of each organism; the gonad was processed using a histological technique, and the gonadal index and length at first maturity (L50) were estimated. C. virgulatus displays partial spawning with a reproductive peak in summer and autumn (July to December). The frequency of ripe organisms was associated with rises in SST (30.6 ºC), AT (29.9 ºC), and TC (68 cm, high tidal), while photoperiod (longer days) regulated the frequency of developing organisms. The length at first maturity was 29.7 mm. Chiton virgulatus is a polyplacophoran species in which high temperatures and high tides influence reproductive timing, while an increase in daylight boosts gonad development.

Olivella minuta is an abundant neogastropod on sandy beaches from Texas (USA) to southern Brazil. This study aimed to characterize and compare the feeding activity and diet of a Brazilian population of O. minuta in different tidal zones (intertidal and subtidal), and different tidal levels (high and low tides), with three combinations of tidal zone and level being studied (intertidal during low tide, intertidal during high tide and subtidal). The results showed that diet composition was generally similar among tidal conditions, with O. minuta being a generalist, feeding on 45 different food items. Feeding activity, however, was higher in the intertidal during low tide, whereas the richness and diversity of food items were higher in the intertidal during high tide. The higher feeding activity of O. minuta during low tide may be linked to a lower risk of predation; at low tide organisms may be able to feed for a longer time, and this may be particularly true on beaches with fine sand, where water retention is higher than that on beaches with coarse sand. The higher diversity of food items consumed in the intertidal during high tide is likely related to the increased prevalence of planktonic food during high tide. Our results indicate that tidal zone and level may strongly influence the feeding activity of coastal soft-bottom species and that species may show higher feeding activity during low tide. Given the current loss of intertidal habitats due to anthropogenic activity and climate-change associated factors, our study has important implications, highlighting the importance of intertidal areas for the ecology and conservation of sandy beach species.

Accurate predictions of the effects of warming temperatures under climate change on an individual species require an accurate characterization of its current and future thermal environment. Behavioral responses to environmental heterogeneity are an important but poorly understood determinant of species’ body temperatures and thermal risks. In this paper we describe the steps necessary for determining a species’ opportunities for behavioral buffering of climate change, and provide examples using a combination of previously published studies and new results for the intertidal snail Nucella ostrina. We find that N. ostrina’s current patterns of daily microhabitat selection have the potential to buffer it from warming temperatures under climate change. N. ostrina’s foraging behavior is highly correlated with the 14.5 d semilunar tidal cycle, shielding it from both current and future thermal stress.

Intertidal culture in meshed bags on trestles is worldwide the most established culture method for oysters. Culturists can affect oyster performance by adjusting stocking density and immersion time, and it can be expected that these factors are not independent. The combined effect of stocking density and immersion time on survival, growth and condition of oysters was investigated on a culture site, where oysters are usually stocked at 8 kg bag−1. Half-grown oysters were stocked in three biomass densities: 4, 8 and 12 kg bag−1, nested within three immersion times (87%, 76% and 73% of tidal cycle). Chlorophyll-a concentration peaked in summer (~ 3–10 μg l−1) and was low in autumn (~ 1 μg l−1), and high chlorophyll-a levels coincided with oyster spawning period. Survival was not affected by density or immersion time. Shell growth per oyster and biomass production per bag were density dependent—higher at 4 than at 12 kg bag−1—but neither were different from 8 kg bag−1. Growth rates were negativity related with immersion over the spawning period but showed a (non-significant) positive trend over other periods. At harvest, condition per oyster decreased with stocking density and increased with immersion. There was no interaction between density and immersion. Treatments had a more pronounced effect on meat content than on biomass production. Hence, oysters might be kept at higher stocking densities to increase biomass production during most of the growth cycle but restocked in lower densities, with longer immersion times prior to harvest to maximize meat content at harvest.

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.

The feeding habitats of Great (Ardea alba) and Snowy (Egretta thula) egrets at the Great Marsh in Northeastern Massachusetts, USA, were characterized through field observations over two years during the breeding seasons of 2012 and 2013. Both species were from a large breeding colony making a daily commute to the Great Marsh for foraging. Habitats at the Great Marsh were delineated as marsh pools, the vegetated marsh, impoundments, open water, tidal flats, and tidal creeks and ditches. Observations (45 counts in 2012 and 48 in 2013) consisted of recording the number of birds, behavior (feeding or not), habitat, and the time of observation and relating these observations to the tidal cycle. The preferred feeding habitats of Snowy Egrets were in marsh pools and along the edges of large impoundments. The preferred feeding habitats of Great Egrets were on the marsh platform, particularly at high tides, and marsh pools. An analysis of physical characteristics with locations of feeding sites revealed no consistent patterns. Certain sites would occasionally support large numbers of feeding Great and Snowy egrets one day only to be ignored the next day at the same tide. The results suggest that Great and Snowy egrets are opportunistic in their selection of feeding sites at the Great Marsh. A future of wetter marshes might provide more feeding opportunities for Great and Snowy egrets, at least in the short-term.

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.

The brooding gastropod Crepipatella dilatata can feed by scraping the substrate with the radula and by suspension-feeding, which also requires use of the radula. There is a “division of labour” for the radula among three discrete tasks associated with feeding: (1) removing mucous balls from the food pouch; (2) transferring the mucous cord from the neck channel to the mouth (both components of suspension-feeding); (3) scraping the substrate. We hypothesised that the proportion of time used for each feeding activity varies according to environmental conditions. Total radular activity in females was greatest at high tide and in summer. The rate of radular extrusion for ingesting the mucous cord varied seasonally and between brooding and non-brooding females. Non-brooding females exhibited higher rates of radular extrusion for ingesting the mucous cord and for scraping the substrate than did brooders. In females, radular activity in removing the mucous ball from the food pouch was strongly influenced by the tidal cycle during winter, reaching minimum values at low tide. Differences were recorded in substrate scraping among seasons and within tidal cycles, and among males, brooding females and non-brooding females. Brooding females displayed less rasping than non-brooders, since the area available for grazing was restricted by the egg mass. Throughout the year, including low salinity periods, males allocated a greater proportion of total radular activity to rasping than to removing the mucous ball or ingesting the mucous cord. The feeding behaviour of both males and females is modulated by salinity, but the principal determinants of radular activity are the mode of reproduction (brooding in females) and, in males, motility.

Animals inhabiting the intertidal zone are exposed to abrupt changes in environmental conditions associated with the rise and fall of the tide. For convenience, the majority of laboratory studies on intertidal organisms have acclimated individuals to permanently submerged conditions, and thus we currently know little about how acclimation to cyclic emersion-immersion influences the ability of intertidal organisms to cope with fluctuations in environmental conditions. In the present study, the green shore crab Carcinus maenas was acclimated to either a simulated tidal regime of continuous emersion-immersion (tidal) or to permanently submerged conditions (non-tidal). Aquatic oxygen consumption was assessed when crabs were exposed to cooling (15 °C - 5 °C) or warming (15 °C - 25 °C) regimes. Tidal crabs had lower levels of oxygen consumption over the 15 °C - 20 °C range. During acute thermal stress, the Q10 values of non-tidal crabs increased as the temperature declined to 5 °C, whereas tidal crabs maintained relatively consistent Q10 values across the temperature range (5 °C–25 C). These changes in oxygen consumption were paralleled by changes in haematological parameters. Tidal crabs had higher levels of haemocyanin which may have augmented oxygen delivery to the tissues and buffered acid-base imbalances. Surprisingly lactate levels were higher in tidal crabs, these appeared unconnected to anaerobic metabolism, but may have been an important metabolic fuel for tidal crabs. These results suggest that acclimation to a simulated tidal cycle may result in different physiological responses to environmental stressors and as such is an important consideration when assessing the responses of intertidal animals in a laboratory setting.

Homing behaviour is frequently observed in marine intertidal invertebrate species. This behaviour may help species to deal with the environmental variability of the intertidal, providing shelter during low tides and areas to explore and search for food during high tides. The capacity of individuals to show fidelity behaviour should be an adaptive trait, due to the uncertainty that finding a new shelter in each tidal cycle implies. Chiton granosus is a common polyplacophora of the Southeastern Pacific rocky intertidal zone. During high tides, individuals move throughout the substratum in search of food; meanwhile, they are found within crevices in groups of variable sizes during low tides. According to previous works, this species shows some degree of fidelity to these shelters. Using field and laboratory experiments, we herein evaluate the factors determining the degree of site fidelity in C. granosus, taking into account the distance travelled from the shelter and food availability. Also, we evaluated the importance that chemical signs from the pedal mucus have in aiding C. granosus to return to its refuge. Field observations showed that C. granosus presents variable levels of site fidelity covering a maximum distance of 50 cm from its shelter. Laboratory results suggested that fidelity to shelters is related to the proximity of food sources. Chemical cues from the pedal mucus could be used to find the shelter after exploratory activities during high tides.

In soft-bottom habitats, post-settlement dispersal of infaunal organisms can be important in population connectivity and turnover. However, this phase of dispersal is often overlooked and understanding of how spatial and temporal variability in biophysical processes drives dispersal in the field is lacking. To quantify spatial and temporal variability in post-settlement dispersal of bivalves, we conducted a study at three sites in Whangarei Harbour, New Zealand. At each site on two separate occasions, we stained the sediment and infauna in 2 m diameter plots with fluorescein to measure the post-settlement dispersal of the clam, Austrovenus stutchburyi (Gray). Dispersal was quantified by monitoring changes in the abundance of non-fluorescent individuals within the plots and fluorescent individuals outside the plots. Our experiments show that some A. stutchburyi were able to disperse at least 50 cm into the plots within 1 tidal cycle (12 h). Dispersal was size dependent, with adult A. stutchburyi dispersing less than juveniles. Post-settlement dispersal varied both spatially and temporally, as indicated by both the change in abundance of non-fluorescent individuals in the plots through time, and the turnover rate within the plots. Dispersal was greatest at the most wave exposed site, and during a storm event. By replicating an experiment in both space and time, our results demonstrate the variability in bivalve dispersal in the field setting. Through the use of fluorescein staining in situ, this study is one of the few that provides estimates of population turnover due to post-settlement dispersal in undisturbed communities.

The pen shell Atrina maura has economic importance in northwestern Mexico, but limitations to rear larvae in hatcheries increased the interest of scientists and producers to study aspects of reproduction and larval cultivation. Reproductive and larval performances of the species were studied in relation to the origin (depth, phases of tidal cycle) and gross condition of broodstock. The results were correlated to variations in water temperature and concentration of chlorophyll a. Tide influenced spawning response, which was between 40% and 100% successful in broodstock collected during rising and falling tides and only 10% at high or low tides (this percentage corresponds tomales only). The number and size of released and fertilized eggs and the survival of larvae were higher in pen shells collected at 5–8 m depth, compared with those collected at less than 1m. The number and size of released and fertilized eggs, number of veliger larvae, and the survival and growth rate of larvae were significant...

The endogenous activity rhythms of the South African endemic isopod Exosphaeroma truncatitelson were explored. Isopods were collected on days coinciding with either a neap or spring tide. High- and low-energy beaches, which vary in the intensity of wave action, were selected as study sites. Isopods, in groups of 10–30, were placed in glass tanks with different experimental conditions: darkness + no sand, darkness with sand and natural ambient light (no sand). Activity of the isopods was measured for 50 h by recording the number of isopods swimming actively during a 30-s period. These isopods exhibited an endogenous activity rhythm which coincided with the tidal cycle even though removed from their natural habitat. Cosine curves were fitted to the observed activity data and statistical differences across variables were investigated. Peak activity was shown to occur shortly after high tide. Similar activity cycles were observed for both neap and spring tides and for different times of the year. Results also...

Many intertidal organisms exhibit endogenous rhythms corresponding to the tidal cycle, i.e., circatidal rhythm. However, circatidal rhythm has been poorly investigated in insects. Several hypotheses have been proposed for the clock generating circatidal rhythm. Nevertheless, the physiological mechanisms of the clocks remain unknown, with one of the long-standing questions being whether the circatidal rhythm is generated by circadian clocks, their variations, or clocks distinct from the circadian clock. In the mangrove cricket Apteronemobius asahinai, the circatidal clock operating locomotor activity rhythm differs from the circadian clock at both the molecular and neural level. Dissections of the clock generating the circatidal rhythm are expected in the near future.

The ovaries of female Fundulus heteroclitus living in the northeastern Florida saltmarsh recrudesce in January and the fish initially spawn heavily during the subsequent full moons (a lunar pattern); they later spawn with less intensity during both the new and full moons (a semilunar pattern), and then regress in late September. In the laboratory, fish spawning against a vertical screen showed only semilunar periodicities, as observed for seven spawning groups under constant conditions (temperature 26 +/- 1°C; photoperiod 14 h light to 10 h dark; excess food). Regardless of collection times (January, April, August, or September), these seven groups exhibited similar patterns of semilunar spawning for five to eight consecutive cycles whose periods (14.4 to 16.0 days) and phases (-1.7 to +8.4 days) were variable compared with concurrent full/new moon and spring tide cycles. These semilunar cycles, which occurred over the entire year in the laboratory, were thus free-running without entrainment and represent endogenous circasemilunar rhythms. In addition to annual and lunar/semilunar cycles, a tidal spawning cycle was also observed in the habitat. Fish apparently select the higher of the two semidiurnal tides for spawning, regardless of the daily light-dark cycle. This tidal cycle has not yet been tested in the laboratory.

Glass eels have a magnetic compass, and their orientation abilities are linked to their endogenous circatidal clock., The European eel (Anguilla anguilla) has one of the longest migrations in the animal kingdom. It crosses the Atlantic Ocean twice during its life history, migrating between the spawning area in the Sargasso Sea and Europe, where it is widely distributed. The leptocephalus larvae drift with the Gulf Stream and other currents for more than a year and metamorphose into glass eels when they arrive on the continental shelf and move toward coastal areas. The mechanisms underlying glass eel orientation toward the coast and into freshwater systems are poorly known. However, anguillid eels, including the glass eel life stage, have a geomagnetic sense, suggesting the possibility that they use Earth’s magnetic field to orient toward the coast. To test this hypothesis, we used a unique combination of laboratory tests and in situ behavioral observations conducted in a drifting circular arena. Most (98%) of the glass eels tested in the sea exhibited a preferred orientation that was related to the tidal cycle. Seventy-one percent of the same eels showed the same orientation during ebb tide when tested in the laboratory under a manipulated simulated magnetic field in the absence of any other cue. These results demonstrate that glass eels use a magnetic compass for orientation and suggest that this magnetic orientation system is linked to a circatidal rhythm.

The upstream migrations of juvenile galaxiids, or ‘whitebait’, form the basis of an important New Zealand fishery. This study used mark and recapture experiments with juvenile galaxiids in the Mokau River to examine the effect of flow on migration and capture rates. Recapture rates of marked fish ranged between 2.7% and 26.9%, with the proportion of fish recaptured positively correlated with increasing river flow. Increasing river flow negatively affected the upstream migration rates of fish. Migration rates through the tidal zone could be rapid, with fish travelling upstream at speeds up to 1.4 km h−1 within 24 h of release. However, not all marked fish exhibited rapid upstream movement. Fish captured on the second day following release had travelled at slower speeds up to 0.7 km h−1, suggesting that these fish did not initiate their migration on the tidal cycle subsequent to their liberation. A small proportion of fish were also found to travel up to 15 km downstream following release at the upper end o...

Hwang, S.D.; Lee, T.W.; Choi, I.S., and Hwang, S.W., 2014. Environmental factors affecting the daily catch levels of Anguilla japonica glass eels in the Geum River estuary, South Korea. The Japanese eel, Anguilla japonica, is a catadromous fish whose recruitment stage glass eels enter estuaries and rivers after being born offshore in the ocean. The daily variation in glass eel catch was analyzed in relation to environmental factors that affect upstream migration. The first glass eels of the 2003 season were caught in the Geum River estuary in early March, when the water temperature exceeded 5°C. The catch rates peaked in mid-March, when the temperature reached 6–7°C. Few glass eels were caught when the temperature was above 14–16°C in early May. Water temperature may have triggered the timing of glass eel immigration. The catch fluctuated with tidal cycle, since the catch level was relatively high during each new and full moon throughout the sampling period. A generalized additive model indicated...

We established the role of the pallial filter in the suspension-feeding slipper limpet Crepipatella fecunda (Gastropoda, Calyptraeidae), which inhabits coastal areas of southern Chile characterised by sediment resuspension resulting from tidal forces. We determined that this spe- cies is capable of qualitative and quantitative pre-ingestive selection of particles. We exposed individual limpets to diets composed of a mixture of sediment and microalgae and measured the particle concentrations in the inhalent region, the infrabranchial cavity and the exhalent region, allowing us to derive an electivity index individually for the pallial filter and the gill. At a particle concentration at which pseudofaeces are always produced, and regardless of the proportion of sediment in the diet, the pallial filter selectively removed sediment (inorganic) material from sus- pension and diverted it into the lateral canal of the mantle for rejection. Qualitative particle selec- tion on the gill was observed when the proportion of microalgae in the diet was low and micro- algae were preferentially retained. When the diet was composed entirely of sediment, the gill retained only 15% of the suspended particles. The gill is more a collector than a selector of parti- cles, while the pallial filter regulates the concentration of particles entering the pallial cavity and increases the nutritional quality of the suspension available for removal by the gill, thereby par- tially compensating for the high proportions of inorganic matter in the resuspended sediment which the limpet encounters during the tidal cycle, especially in the periods immediately before exposure to air and after reimmersion.

The tidal cycle around New Zealand results in spring low tides consistently occurring during the hottest part of the day (mid-afternoon) in north-eastern New Zealand, and during the cooler dawn/dusk periods in the north-west of the country. We hypothesised that due to mid-afternoon spring low tides, intertidal populations residing at north-eastern sites would show greater thermotolerance than their north-west conspecifics. To test this we used the marine gastropod, Lunella smaragda, which were collected from sites on both the East and West coasts of the Auckland region and exposed to an acute heat shock. Thermotolerance was measured as survivorship (LT 50 ), drop down time (time to heat coma) and thermal stability of the anaerobic energy producing enzyme Tauropine dehydrogenase. Furthermore, temperature loggers were deployed at each site so as to record and compare thermal regimes among sites. A strong temperature spike associated with spring low tide was found at all sites, and maximal temperatures of all East coast sites were higher than West coast sites (in some case by up to 10 °C). In terms of thermotolerance, mortality of L. smaragda occurred at 42 °C leading to 100% mortality at 45 °C. However, comparison of LT 50 showed snails were equally thermotolerant regardless of site of collection. Similar results were found in TDH thermal stability with animals from all sites showing an approximately 80% decrease in enzyme activity after 10 min exposure to 42 °C. Whilst drop down times were different among sites these were correlated with animal size as opposed to site of collection. Thus, East coast populations of L. smaragda appear no more thermotolerant than their West coast counterparts. Such a result is concerning as maximal temperatures at East coast sites already exceed the LT 50 values of L. smaragda recorded in the lab suggesting these populations have less of a thermal safety margin.

The shallow coast of The Netherlands is an important habitat for small pelagic fish. They form one of the major links between plankton and the higher trophic levels. Predatory fish, sea mammals and birds rely on small pelagic fish as a major food source. Currently, monitoring of fish in the Dutch coastal zone mainly focuses on demersal species, using bottom trawls and fykes. Four hydro-acoustic surveys were carried out in May and October 2010/2011 in the Marsdiep area, a relatively deep tidal inlet in the western Wadden Sea, to quantify abundances of pelagic fish. The aims of this study were to (1) describe temporal and vertical variations in fish distribution and school dimensions in relation to tide, and (2) estimate biomass of pelagic fish and their proportion to total fish biomass. The biomass of pelagic fish in the Marsdiep area ranged between 23 and 411 kg/ha. These were mainly sprat, but also young herring, anchovy and pilchard. The fish was scattered in small schools with volumes smaller than 5m 3 and concentrated in the top 10 m below the surface. There was a clear effect of tidal cycle on school volume and fish abundance, with larger densities and larger schools at high tide compared to low tide. In May, sandeel contributed substantially to the pelagic assemblage, whereas in October sandeel was absent in the trawl catches, most likely because they stayed buried in the seabed from late summer to spring. The presence of pilchard and anchovy confirmed their re-establishment in the Southern North Sea and Wadden Sea. The abundance of pelagic fish exceeded the biomass of demersal fish in the western Wadden Sea by an order of magnitude. This finding is relevant for ecosystem studies. The fact that this study suggests that small pelagics outnumber demersal species to such a large extent calls for a rethinking of the allocation of monitoring effort in the Dutch coastal zone.

International audience; The case study of Yves Bay (Pertuis Charentais, France) highlighted links between environmental gradients (i.e. sediment characteristics and emersion time) and prey distribution and availability for the two most numerous shorebird species overwintering in Yves Bay: the red knot Calidris canutus and the dunlin Calidris alpina. Two hundred and fifty-two stations were sampled on a predetermined 250 m regular grid covering the intertidal mudflats of this major wintering site in France for east-Atlantic migratory shorebirds. The distribution of principal benthic species abundance and biomass was modelled along two environmental gradients: sediment structure (particularly pronounced north–south sand-mud gradient) and emersion time. The effect of emersion time combined with sedimentary structure strongly explained abundances and biomasses of the main prey for C. canutus and C. alpina in the bay (Cerastoderma edule, Hydrobia ulvae, Macoma balthica, Scrobicularia plana, and Nephtys hombergii). This study highlighted prey species-specific spatial segregation/overlapping as well as spatial interferences in the trophic niche of the two shorebirds.

We tested herein the hypothesis that exposure time significantly contributes to the vertical distribution profile of nematodes during a tidal cycle as a function of distinct feeding and locomotion behaviors, conditioned by body morphology. We showed that the vertical distribution profile of the slender with filiform tail, numerically dominant Terschellingia longicaudata is in fact significantly correlated with sediment changes induced by tidal variation. Conversely, none of the other nematode species showed unequivocal evidence of vertical migration. Horizontal spatial heterogeneity also influenced the vertical distribution of nematode associations, probably as a response to varying temperature and desiccation levels at the sediment surface. The resulting vertical profiles for individual or species groups are a trade-off among locomotory and feeding strategies and concordant morphological adaptations.

Hydrobia ulvae displays an endogenous rhythm of crawling behaviour of circatidal periodicity, with higher levels of activity during high water. In the present study we address the effect of repeated cycles of immersion and emersion at tidal periodicity on the level and synchronism of the behaviour, by contrasting these with the effects of continuous immersion and continuous emersion. Snails were recorded in dark conditions under the different immersion regimes for 3 days. The results show that continuously emersed snails displayed very low levels of activity. Average activity levels of continuously immersed snails and of those subjected to tidal cycles of immersion and emersion were similar, had identical periods related to the period of the tidal cycle, and had similar phase relationships to the expected tidal cycle. However, form-estimates for these two categories of snails differed, the snails subjected to cyclic conditions showing a larger amplitude and greater synchronism of activity. Therefore, it is concluded that recurrent cycles of immersion and emersion should contribute to well defined cycles of activity in the intertidal environment, with greater activity levels during high water.

Fish spawning aggregations (FSA) are generally spatially and temporally predictable, making them particularly vulnerable to fishing, which is capable of rapidly removing a significant proportion of the aggregated adults and reducing egg production. These effects may cause the loss of the aggregation altogether. In the Northern Territory (NT), Australia, repeated fishing of known aggregations of the tropical sciaenid species, the blackspotted croaker Protonibea diacanthus, is probably unsustainable, particularly given this species' decline elsewhere. Acoustic monitoring was used to examine the temporal and spatial movement patterns and site fidelity of P. diacanthus in the NT. Fish were only detected at their respective aggregations, providing no evidence of large-scale movements between FSA. There was evidence for behavioural polymorphism in the aggregations, and fish monitored for ≥1 yr showed decreased presence during cooler months and increased pres- ence during warmer months when peak spawning occurs. The tidal cycle significantly influenced the detection of tagged fish, with detections peaking on running tides, the peak period for catching P. diacanthus, suggesting that this is when they feed. This study has provided important information on the connectivity and dynamics of P. diacanthus aggregations in the NT, including crucial information for implementing appropriate management strategies for this vulnerable species. There appears to be little interchange of adult P. diacanthus at the spatial scale examined, which suggests that the sep- arate FSA examined support separate adult populations. The presence of seemingly separate spawn- ing populations of P. diacanthus has significant implications for their management, with the potential for each aggregation to be vulnerable to localised depletion.

Males of several species of fiddler crabs construct sand structures at the entrance of their burrows, to which they attract females for mating. Although sand structures are able to attract females, males do not always construct structures, and there is a considerable variation in the frequency of structure construction per day. To determine what factors cause the variation in the frequency of structure construction, I conducted a field observation on the structure construction of Uca lactea and examined the effects of air and soil temperatures, tidal amplitude, male and female densities, and the interaction between male and female densities. The frequency of structure construction was related to tidal amplitude. This may be a male response to the changing levels of female receptivity associated with the tidal cycle. The frequency of structure construction was also correlated positively with air temperature. Although courtship investment is expected to be influenced by the number of mates and rivals, neither male nor female density were significantly correlated with the frequency of structure construction. Les mâles de plusieurs especes de crabes violonistes construisent des structures de sable a l'entree de leur terrier, vers lesquels ils attirent les femelles pour l'accouplement. Bien que ces structures de sable sont capables d'attirer les femelles, les mâles ne construisent pas toujours ces structures, et il y a une grande variation journaliere de la frequence des constructions. Une observation sur le terrain de la construction de ces structures par Uva lactea a ete menee. Ont aussi ete examines, les effets de la temperature de l'air et du sol, de l'amplitude des marees, de la densite des mâles et des femelles, et les interactions entre ces densites. La frequence des constructions a ete reliee a l'amplitude des marees. Ce qui pourrait etre la reponse du mâle au changement du niveau de receptivite de la femelle associe au cycle des marees. La frequence des constructions a aussi ete positivement correlee avec la temperature de l'air. Bien que l'on attende que l'investissement dans la recherche du partenaire soit influence par le nombre de partenaires et de rivaux, ni la densite des mâles ou des femelles n'a ete significativement correlee avec la frequence des constructions.

This paper presents the first data on the diving behaviour of Flatback turtles, Natator depressus, between nesting events. Dive profiles were recorded in turtles from breeding populations at Curtis Island in Queensland and at Bare Sand Island in the Northern Territory, using Time-Depth Recorders (TDRs). Both populations displayed dive types typical of those described in other internesting sea turtles. Dives spent on the seabed were most prevalent, accounting for 57% of the time at depth. While on the sea bed, the turtles apparently remained inactive, cyclical changes in depth reflecting the tidal cycle. These inactive dives were long compared to those typical of other large sea turtles such as C. mydas and C. caretta, up to 98 min (mean 80±12 min), and with a mean and median of 50 and 52 min, respectively. In both populations, these dives occurred more commonly by day, by an average of 14%, and were most prevalent in the middle third of the internesting interval in most turtles, while the eggs were maturing. The turtles spent only 10% of their time at or near the surface and surface intervals rarely exceeded a few minutes, insufficient to be attributed to a need for either rest or thermoregulation. The Bare Sand Island population showed longer dive durations and proportionally more dives with a gradual ascent phase, a phase presumed to be a method of compensating for buoyancy loss and a way for turtles to conserve energy in mid-water while still moving around. Maximum dive depths of 29 m and 44 m were recorded at Curtis Island and Bare Sand Island respectively, probably reflecting differences in bathymetry.

Despite the numerous ecological and behavioural studies, relatively little is known about the behavioural dynamics of Corophium volutator during the tidal cycle. In the present study, the behaviour of C. volutator was observed in the laboratory in a tide-simulated aquarium, and time allocation of the different activities was quantified. Overall, the surface activity was low and showed a steep decline after submersion. A clear tide-based cyclic pattern was found, with a boost of activity immediately after first submersion, continuing during submersion, and shifting over a period with decreasing activity towards almost total inactivity at the end of emersion.

Little is known about the specific environmental cues that gravid females use to initiate nesting behaviours, especially in aquatic species that are restricted to nesting in terrestrial environments. I used 15 atmospheric and oceanic environmental variables to help explain the nightly variation in the number of loggerhead turtle nests laid and the proportion of emergences that resulted in a nest. The number of nests laid was related to principal components weighted heavily by rainfall (positive association) and tidal cycles (nesting occurred when tides were moderate), although the predictive power of the environmental variables was limited. In addition, a higher proportion of emerging females laid nests during nights associated with other factors, including temperature and maximum tidal cycles. Since rainfall is commonly associated with nesting in many turtle species, I also tested the hypothesis that nesting on nights during rainfall results in a lowered probability of nest depredation. However, I found no support for this hypothesis. The turtle's large body size makes it unlikely that nesting during rainfall slows evaporative water loss or makes it easier to dig nests by softening the sand, but there may be other reasons for associating nesting with rainfall events, for example locomotion may be more efficient in moist sand. Nesting female loggerhead turtles appear to use multiple environmental cues to guide their nesting behaviours, and may use different sensory processes to determine when the weather is suitable for emerging from the ocean, and subsequently whether the conditions are conducive for laying eggs.

“Biolog” plates were used to study the changes in the metabolic capabilities of bacterioplankton over a complete tidal cycle in a tropical ecosystem (Cochin Estuary) along southwest coast of India. The pattern of utilization of carbon sources showed a definite shift in the community metabolism along a salinity gradient. Multivariate statistical analysis revealed two communities, namely allochthonous bacterioplankton sensitive to salinity and autochthonous bacterioplankton, which are tolerant to wide salinity fluctuations. Regression analysis showed salinity as the most important parameter influencing the physiological profile of bacterioplankton, irrespective of tide. Apart from salinity, limno-tolerant retrievable counts and halo-tolerant retrievable counts also accounted for the metabolic variation of bacterioplankton during low and high tides, respectively. The shift in the substrate utilization from carbohydrates to amino acids appears to be due to the physiological adaptation or nitrogen limitation of bacterial community with increasing salinity.

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.

172 Behavioral characteristics and functional mechanisms of physiological systems of various marine mammals have been a focus of researchers’ attention for several decades [1‐4]. The interest in these issues is determined by unique adaptive capacities of the animals to a wide range of temperatures and pressures and their ability to remain at a considerable depth under water for a long time. At the same time, our knowledge on the physiology of marine mammals is as little as 5‐10% of that for terrestrial mammals, according to Yablokov’s [5] estimation. We studied some behavioral and physiological characteristics of gray ( Halichoerus grypus Fabricius, 1791) and Greenland ( Pagophilus groenlandica Erxleben, 1777) seals aged from one to eight years. The seals were kept in net enclosures in a lake connecting with the sea during the tidal cycle at the Experimental

One of the most important factors explaining the distribution and behaviour of coastal marine mammals are tides. Tidal forces drive a large number of primary and secondary processes, such as changes in water depth, salinity, temperature, current velocity and direction. Unravelling which tidal process is the most influential for a certain species is often challenging, due to a lack of observations of all tide related covariates, strong correlation between them, and the elusive nature of most marine organisms which often hampers their detection. In the Marsdiep area, a tidal inlet between the North Sea and the Dutch Wadden Sea, the presence of harbour porpoises ( Phocoena phocoena ) was studied as a function of tide related covariates. Observations were carried out in early spring from a ferry crossing the inlet on a half hourly basis. Environmental and sightings data were collected by one observer, while an on-board Acoustic Doppler Current Profiler (ADCP) and temperature sensor continuously recorded current velocity profiles and temperature, respectively. Sea surface temperature and salinity were measured at a nearby jetty. Sightings ( n = 134) were linked to tidal elevation, geographical position, local depth-averaged current velocity, water temperature (with and without trend correction) and salinity. Variation in sighting rate was best described by salinity, with highest sighting rate at high levels of salinity (> 30 g kg − 1 ), indicating that porpoises enter the area in bodies of (more saline) North Sea water. Second best variable was time of day, with the highest sighting rate early morning, and decreasing during the day. However, surveys in the morning happened to coincide more often with high water and hence, the apparent time of day effect could be due to collinearity. Most porpoises were present in the northern part of the Marsdiep, particularly during high tide. Tide dependent sighting rates confirmed that porpoises reside in the North Sea, and enter the western Wadden Sea during the flood and leave during ebb. This tidal influx is most likely related to prey availability, which corresponds to other recent studies in this area showing higher fish abundance during high tide. Documenting information on tide related patterns could be used in practice, when e.g. planning anthropogenic activities or assessing critical habitats for this species.

The brown shrimp (Crangon crangon) is a highly abundant invertebrate in the North Sea with its life cycle spanning deeper offshore spawning and shallow onshore nursery areas. To overcome the long distances between these two habitats, brown shrimp are suspected to use selective tidal stream transport (STST) moving with the cyclic tide currents towards their preferred water depths. However, it is not known which stimulus actually triggers STST behavior in brown shrimp. In this work, we determined the influence of different hyperbaric pressures on STST behavior of juvenile brown shrimp. Brown shrimp's activity was recorded in a hyperbaric pressure chamber that supplied constant and dynamic pressure conditions simulating different depths with and without a tidal cycle. Subsequent Wavelet and Fourier analysis were performed to determine the periodicity in the activity data. The results of the experiments show that STST behavior in brown shrimp varies with pressure and therefore with depth. We further show that STST behavior can be initiated by cyclic pressure changes. However, an interaction with one or more other environmental triggers remains possible. Furthermore a security ebb-tide activity was identified that may serve to avoid potential stranding in shallow waters and is “remembered” by shrimp for about 1.5 days without contact to tidal triggers.

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.

Larvae of the coastal tiger beetle Callytron inspecularis (W. Horn) (Coleoptera: Cicindelidae) plug their burrow opening before submergence at high tide. Field observations showed that burrow plugging was a rhythmic behaviour that coincided with the tidal cycle (ca. 12.4 h). On average, larvae plugged their burrows 41.8 min before the tide covered the habitat. The mean interval between consecutive burrow-plugging events in the field was 12.40 h. In the laboratory, in the absence of tidal inundation, the mean interval between consecutive burrow-plugging events was 12.45 h. This suggests that the burrow-plugging rhythm of the coastal tiger beetle is governed by an endogenous circatidal rhythm.

Capsule Low tide counts may give inaccurate estimates of habitat use; combining low and mid-tide counts yields better estimates. Aims To evaluate whether low tide bird counts provide a good estimate of habitat use of intertidal areas with different exposure periods, to analyse how differences in the response of the birds to the tidal movement influences these estimates, and to evaluate an alternative to the traditional counting scheme. Methods The total use of intertidal plots by six wader species was estimated through regular bird counts during entire tidal cycles. These estimates were then compared to estimates of use based on both replicate low tide counts, and a combination of low and mid-tide counts. Results For most species, estimates based on low tide counts alone differed substantially from estimates based on counts repeated over the full tidal cycle. This difference tended to be greater in the upper parts of the sediment flats, and in species that followed the tidal waterline while foraging. Usin...

Laboratory experiments on two species from the Pecten (Pecten) subgroup of pectinids indicated that they form growth lines with a true (solar) daily periodicity. Experimental subjects that formed growth lines in numbers equal to their days of growth were consistently those with uniform, apparently continuous shell growth, and subjects that formed fewer lines than days were those with stress marks, or disturbance lines. No subjects formed more growth lines than days. Furthermore, those specimens forming stress marks had those marks spaced out in very similar patterns, apparently in response to stressful events in their aquarium, such that the patterns could be correlated, not only between the specimens with interrupted growth, but with the others as well. In the original experiments, a natural light–dark stimulus had been present (transparent aquaria near an outside window). To test whether the subjects were responding to this stimulus, another experiment was conducted in which several individuals were subjected to an accelerated light–dark regime. These subjects responded by increasing production of their growth lines to approach the number of cycles to which they had been exposed. An opportunity to extend this work into the fossil record came with the collection of a number of Pliocene pectinids, closely related to one of the species used in the experiments, from a thin horizon that almost certainly represents a catastrophic event. Measurements of the intervals between growth lines were made across hundreds of increments on many paired (and presumably untransported) valves. Comparison of these growth rate records suggested that many, and perhaps all of these individuals died at the same time. Moreover, frequency analysis of these records revealed a regular fluctuation of about 15 days, suggesting a tidal cycle marked off by solar increments. When the growth rate patterns were compared with nearby tidal regimes, the best fit was for a regime matching the currently accepted paleogeography of the collecting site in Pliocene time. This strongly supports the experiments on the living species, for tidal patterns in the fossil group could not have been revealed without an accurate solar marker.

The California grunion Leuresthes tenuis, a teleost fish (Atherinopsidae), spawns terrestrially by burying its eggs in damp sand on beaches following semilunar spring tides. The eggs incubate above the water line and are ready to hatch after approximately 10 days at 18 C. However, grunion eggs do not hatch, even when developmentally ready, until returned to water and mechanically stimulated by wave action. In nature, the environmental trigger occurs on subsequent semilunar tides, when waves reach as high on the shore as the eggs were buried during spawning. If waves do not reach the eggs after one semilunar tidal cycle, the eggs survive by extending incubation and delaying hatching until the trigger occurs. This may take up to several additional weeks. Temperature affects the time to hatching readiness in California grunion eggs; this interval is shorter at warmer temperatures than at cooler ones. We incubated grunion eggs at three relevant temperatures: 15, 20, and 25 C. Viability of embryos was ascertained by microscopic examination, and hatching was attempted daily for eggs from each temperature, until no eggs hatched. The ability to extend incubation and delay hatching decreased with increasing incubation temperature. At the coolest temperature, eggs survived longer but were not able to hatch at the time of the first semilunar spring tide series. Hatching success and the duration of extended incubation are also influenced by temperature. Eggs incubated at 15 C always had lower hatching success than eggs incubated at the two higher temperatures. Eggs incubated at 20 C had a significantly greater chance of surviving and hatching during the three subsequent semilunar tides than eggs at 15 or 25 C. Eggs incubated at higher temperatures matured more quickly but had a shorter total period of viability. Temperature affects the duration of extended incubation for grunion eggs, and influences their hatching success, yet a majority of the eggs can mature and hatch successfully at each of the three temperatures. A broad temperature tolerance, plasticity in incubation duration, and environmentally triggered hatching allow the grunion fish to spawn terrestrially over a long season in a variable coastal ecosystem.

It has been suggested that some gastropods might utilise pedal mucus trails as a source of nutrition. Despite much work, there has been little attention on the ecological consequences of such a strategy. Here we aimed at determining the value of mucus trails to snails by investigating (1) snail reaction to naturally aged conspecific mucus trails and (2) the effect of starvation on trail- following behaviour. The mucus trails of Littorina littorea (L.) adhered microalgae in the laboratory but this ability began to diminish after the trails had been exposed on-shore for >1 tidal cycle. Nat- ural floral components of trails were greatest for up to 4 tidal cycles of exposure and then began to diminish. If trails are to be used for foraging purposes, snails would gain most benefit by utilising them while relatively fresh. Correspondingly, snails readily responded to fresh mucus trails, but after 20 tidal cycles only 3 of 24 did so. As the mucus was still present we conclude that some unknown cue is present enabling snails to discriminate trails by their age. Despite previous work to the contrary, no evidence of preference for following trails in a particular direction was found and we conclude that trail following in our snails was not related to mate searching or the formation of aggregations. The starvation level of snails (up to 4 d) did not affect their foraging behaviour in the laboratory. However, snails followed the trails of starved snails for significantly shorter distances than those of fed snails, suggesting a coding of starvation level in the trail mucus. Choices about whether to trail follow may be based on how well fed a conspecific is and how old a trail is —following a fresh trail would increase the likelihood of encountering a conspecific and may have a nutritional benefit if the trail is to be grazed. Previous work on trail following should be re-evaluated in the light of these findings.

An animal's decision to enter into a fight depends on the interaction between perceived resource value (V) and fighting costs (C). Both could be altered by predictable environmental fluctuations. For intertidal marine animals, such as the sea anemone Actinia equina , exposure to high flow during the tidal cycle may increase V by bringing more food. It may also increase C via energy expenditure needed to attach to the substrate. We asked whether simulated tidal cycles would alter decisions in fighting A. equina . We exposed some individuals to still water and others to simulated tidal cycles. To gain insights into V, we measured their startle responses before and after exposure to the treatments, before staging dyadic fights. Individuals exposed to flow present shorter startle responses, suggesting that flowing water indicates high V compared with still water. A higher probability of winning against no-flow individuals and longer contests between flow individuals suggests that increased V increases persistence. However, encounters between flow individuals were less likely to escalate, suggesting that C is not directly related to V. Therefore, predictable environmental cycles alter V and C, but in complex ways.

The influence of topographic and temporal variables on cetacean distribution at a fine-scale is still poorly understood. To study the spatial and temporal distribution of harbour porpoise Phocoena phocoena and the poorly known Risso's dolphin Grampus griseus we carried out land-based observations from Bardsey Island (Wales, UK) in summer (2001-2007). Using Kernel analysis and Generalized Additive Models it was shown that porpoises and Risso's appeared to be linked to topographic and dynamic cyclic variables with both species using different core areas (dolphins to the West and porpoises to the East off Bardsey). Depth, slope and aspect and a low variation in current speed (for Risso's) were important in explaining the patchy distributions for both species. The prime temporal conditions in these shallow coastal systems were related to the tidal cycle (Low Water Slack and the flood phase), lunar cycle (a few days following the neap tidal phase), diel cycle (afternoons) and seasonal cycle (peaking in August) but differed between species on a temporary but predictable basis. The measure of tidal stratification was shown to be important. Coastal waters generally show a stronger stratification particularly during neap tides upon which the phytoplankton biomass at the surface rises reaching its maximum about 2-3 days after neap tide. It appeared that porpoises occurred in those areas where stratification is maximised and Risso's preferred more mixed waters. This fine-scale study provided a temporal insight into spatial distribution of two species that single studies conducted over broader scales (tens or hundreds of kilometers) do not achieve. Understanding which topographic and cyclic variables drive the patchy distribution of porpoises and Risso's in a Headland/Island system may form the initial basis for identifying potentially critical habitats for these species.

Some intertidal insects show endogenous activity rhythms that synchronize with the tidal cycle, that is, circatidal rhythms. In this chapter, we collected studies of the circatidal activity rhythms of intertidal insects and the entrainment of the circatidal rhythm to the tidal cycle. Until now, circatidal activity rhythms have been reported in three taxonomic groups: springtails (Collembola), beetles (Coleoptera), and crickets (Orthoptera). The mangrove cricket Apteronemobius asahinai is known as the only insect species that shows clear and persistent circatidal activity rhythms. When the inundation cycle with a period of 12.4 h was provided by artificial means, the circatidal rhythm of A. asahinai responded to the given periodic inundations in a phase-dependent manner. Furthermore, the molecular mechanism of the circatidal clock of A. asahinai is likely to be different from the circadian clock. Advances in studies in A. asahinai will lead to better understanding of the circatidal rhythm in insects.

To examine how Steller's eiders, Polysticta stelleri, wintering at 70°N cope with adverse winter conditions in terms of darkness and low temperatures, we studied their feeding behaviour during four periods between late autumn and early spring. Steller's eiders were most likely to feed during daylight and twilight, but they also fed during darkness. The incidence of feeding was highest at low tide, and there was a significant interaction between tidal cycle and winter period. Hence, the birds fed more intensively at low tide in midwinter (January) than during the other periods. Air temperatures were between 8 and 10°C lower in midwinter than during the other periods, and during this period the eiders also fed more by means of nondiving techniques (up-ending, surface feeding). The total estimated feeding time was highest in late autumn and midwinter (5.9 and 6.3 h were spent actively feeding, respectively) and lower in late winter and spring (5.1 and 4.6 h, respectively). Thus, as energy requirements increased as a result of low temperatures, Steller's eiders increased their feeding effort, but also reduced feeding costs by reducing diving depth. The results of this study suggest that the Steller's eider is behaviourally well adapted to survive winter at high latitudes at relatively low stress.

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.