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High Tide (high + tide)
Selected AbstractsMicrohabitat and rhythmic behavior of tiger beetle Callytron yuasai okinawense larvae in a mangrove forest in JapanENTOMOLOGICAL SCIENCE, Issue 3 2007Aya SATOH Abstract Mangrove forests are regularly flooded by tides at intervals of approximately 12.4 h (tidal rhythm). Larvae of the tiger beetle Callytron yuasai okinawense in a mangrove forest made shallow burrows in mounds up to 1 m in height constructed by the mud lobster Thalassina anomala. No larval burrows were observed on the forest floor, which was very muddy even during low tide. Some larvae plugged the burrow openings before they were submerged at high tide. The mean interval between consecutive burrow plugging events was 12.37 h, which is similar to the period of tidal cycles. Nine out of 30 larvae plugged the burrow openings even when the burrows did not become submerged. Plugging behavior may be governed by an endogenous biological clock, or may be a response to exogenous information about tidal level (e.g. moisture seeping through the ground). [source] Incidence and severity of marine borer attack at different depths at Mtongwe Jetty Pontoon Mombasa, KenyaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009P. K. Sirmah Abstract The activity of marine borers was investigated at Mtongwe Jetty Pontoon, Mombasa, Kilindini harbour using untreated panels of Pinus patula (Schlecht) submerged to different depths. Twenty test panels replicated over 7 months were each strung in three ladder-like frames using nylon twine and suspended vertically, in such a way that the top most panels were 25 cm below the water surface at low and high tide. Monthly observations were made between January and July for the vertical incidence and extent of marine borer attack following the technique of Bobat (1995). Marine borers were collected from test panels, identified and counted. In addition, the percentage weight loss for panels at different depths was determined at the end of 7 months. Teredo fulleri (Clapp) was dominant on panels near water surface while Martesia striata (Linne) and Lyrodus pedicellatus (Quatrefages) were predominant at the bottom. The results showed that attack began within the first month of exposure and was severest by the seventh month. The vertical incidence and extent of attack decreased with increasing depth of panel exposure and was negatively correlated with depth. This is attributed to changes in hydrographic conditions. Résumé L'activité des foreurs marins a étéétudiée dans le Ponton de Mtongwe Jetty, Mombasa, dans le port de Kilindini, en utilisant des panneaux de Pinus patula (Schlecht) non traités, plongés à différentes profondeurs. Vingt panneaux tests identiques ont été attachés avec des cordes de nylon pour former trois cadres ressemblant à des échelles et suspendus pendant sept mois verticalement de façon à ce que les panneaux supérieurs se trouvent à 25 cm sous la surface à marée basse et haute. L'on a fait des observations mensuelles entre janvier et juillet de l'occurrence verticale et l'étendue de l'attaque des foreurs marins en utilisant la technique de Bobat (1995). Les foreurs marins ont été collectés sur les panneaux tests, identifiés et comptés. De plus, on a déterminé le pourcentage de la perte de poids des panneaux aux différentes profondeurs à la fin des sept mois. Teredo fulleri (Clapp) était dominant sur les panneaux situés près de la surface de l'eau alors que Martesia striata (Linné) et Lyrodus pedicellatus (Quatrefages) étaient prédominants en profondeur. Les résultats ont montré que l'attaque a commencé dès le premier mois et que c'est alors qu'elle fut la plus sévère. L'occurrence verticale et l'étendue de l'attaque diminuaient quand le panneau était plus profond et étaient négativement liées à la profondeur. Cela est attribué aux changements des conditions hydrographiques. [source] Recruitment of Anguilla spp. glass eels in the Waikato River, New Zealand.JOURNAL OF FISH BIOLOGY, Issue 9 2009Evidence of declining migrations? The timing of Anguilla spp. glass eel recruitment into the Waikato River, North Island, New Zealand, was studied over a 2 year period (2004,2005). While glass eels of both the shortfin eel Anguilla australis and the endemic longfin eel Anguilla dieffenbachii were caught, the former comprised >97% of the species composition. There was a positive correlation of glass eel migrations with spring tides, with peak migration periods typically occurring within a few hours of the peak of high tide, and between 2 and 4 days after the day of spring tide. Both water temperature and discharge had significant inverse relationships with glass eel catches, with temperature explaining >30% of the variance in catch periodicity. Comparison of catch data 30 years apart showed that main migration periods appear to occur several weeks earlier today than previously. Reduced catch per unit effort and duration of runs from recent years' sampling (compared with the 1970s) indicate that a reduction in recruitment may also have occurred during this period, something recorded in other temperate species of Anguilla. [source] Factors affecting recruitment of glass eels into the Grey River, New ZealandJOURNAL OF FISH BIOLOGY, Issue 5 2003D. J. Jellyman The arrival pattern of glass eels of the shortfin eel Anguilla australis and longfin eel Anguilla dieffenbachii was studied over a two successive migration seasons in the Grey River, South Island, New Zealand. Fishing was carried out on selected nights during September to November, for 3 h per night during 2000 and 2001. The number of shortfin glass eels exceeded longfins in both years; earliest glass eels (September) were larger than later glass eels (November), and longfins larger than shortfins, but there were significant differences in size between years for both species. Environmental variables affecting recruitment differed between years, but common variables for both years were sampling date, time after high tide (incoming tide preferred), time after sunset and moon phase; the influence of moon phase appeared to be expressed both through tides (spring tides preferred) and moonlight. During the year of higher discharge variability, both increasing discharge and increased turbidity were also important. [source] HABITAT DIFFERENCES IN THE TIMING OF REPRODUCTION OF THE INVASIVE ALGA SARGASSUM MUTICUM (PHAEOPHYTA, SARGASSACEAE) OVER TIDAL AND LUNAR CYCLES,JOURNAL OF PHYCOLOGY, Issue 1 2009Carla Monteiro Sargassum muticum (Yendo) Fensholt is an invasive species that is firmly established on intertidal and subtidal rocky shores of Europe and the Pacific coast of North America. Local success and spread of S. muticum is thought to rely on its reproductive potential that seems dependent on exogenous factors like tidal and lunar cycles. This study is the first to compare the reproductive patterns (periodicity of egg expulsion and embryo settlement) of this invader in two different habitats: the middle and low intertidal. The combination of monthly, daily, and tidal samples at triplicate sites within each habitat showed a semilunar periodicity of egg expulsion and embryo settlement coincident with increasing tidal amplitude just before full and new moons. In both habitats, duration of each egg expulsion event was ,1 week, and embryo settlement occurred during the first daily low tide and with the incoming high tide during spring tides. However, both expulsion and settlement started 1,2 d earlier, expulsion saturation was faster, and settlement was higher in the mid- compared to the low intertidal. Our results suggest that the exact timing of gamete expulsion and embryo release of S. muticum responds to local factors, including tidal cues, which result in differences between mid- and low-intertidal habitats. [source] ARE SPERM LIMITING IN THE SEA?JOURNAL OF PHYCOLOGY, Issue 2000M. L. Berndt The reproductive success of marine species with external fertilization depends on environmental conditions during gamete release. There is special interest presently in whether water motion causes sperm limitation under natural conditions. We investigated gamete release of Fucus vesiculosus from an exposed shore to ascertain: 1) when gametes are released during the tidal cycle, 2) when fertilization occurs, and 3) what the natural sperm:egg ratios are. Water samples were collected and concentrated over five minutes every half hour off Pemaquid Point, ME from three replicate sites within each of two locations using a pump-filter device. Immunofluorescence microscopy revealed that gamete release occurred only on the two calmest spring tides. Sperm became present in the water column at the same time as oogonia (30 min,1 h prior to high tide [HT]) and reached peak concentration at exactly HT. The sperm:egg ratio was 76:1 on 8 Oct 1999 and 21:1 on 8 Nov 1999 at exactly 30 min prior to HT and dropped sharply after HT. Gametes continued to be collected for several hours after HT but analysis of pronuclear position in aceto-iron-hematoxylin stained eggs revealed that all fertilization occurred at approximately HT. We modelled the total number of days when reproduction was possible using these results and wind and wave data from the National Data Buoy Center. Our research provides evidence that gamete release by F. vesiculosus occurs at slack HT on calm days and that sperm are not a limiting factor in fertilization for this species. [source] The effect of weather conditions on the Oxford,Cambridge University Boat RaceMETEOROLOGICAL APPLICATIONS, Issue 2 2009Benjamin J. Morris Abstract The sensitivity of Oxford,Cambridge University Boat Race finishing times to changing weather conditions was assessed over the period 1949,2006. Predictors of race times included tide height and river discharge as well as standard weather variables (temperature, humidity, wind speed and wind direction). As the Race is rowed against the flow of the River Thames, quicker races are favoured when a low river discharge is combined with a high tide and a SE wind. Wind speed and direction exert a much greater influence on race times than temperature and humidity. The zonal (W,E) wind speed explained 28.5% of the year-to-year variations in finishing times between 1967 and 2005, with races taking place under a westerly wind being on average 1 min and 27 s slower than races rowed under easterly conditions. The combined effects of the wind, river discharge and tide height accounted for 42.9% of the inter-annual variance in race times over a 39 year period. Races rowed under cooler conditions tended to be slightly slower. The results are discussed in the context of the biometeorological literature and the hydrodynamics of the Boat Race course. Copyright © 2008 Royal Meteorological Society [source] Effects of the Cardiff Bay tidal barrage on the abundance, ecology and behaviour of shelducks Tadorna tadornaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2009Peter N. Ferns Abstract 1.Closure of the Taff/Ely Estuary by the Cardiff Bay barrage in 1999 resulted in the replacement of intertidal mudflats by a permanent freshwater lake. This led to an 89% reduction in the population of shelducks Tadorna tadorna. 2.The birds switched from foraging mainly for Nereis diversicolor and Hydrobia ulvae by scything with the bill as they walked across the mudflats at low tide, to feeding on benthic chironomid midge larvae while swimming in shallow water around the margins of the lake. 3.The population decline occurred as a consequence of a decrease in the area available for foraging,,,from about 1,km2 of mudflats to about 0.1,km2 of water shallow enough for shelducks to reach the bottom when dabbling, head dipping and upending. 4.Contrary to expectation, the amount of time shelducks spent feeding was similar pre- and post-barrage, and their body and plumage condition improved. 5.A tidal rhythm in activity persisted, with a reduced amount of feeding at high tide, probably because of the slight rise in water levels that sometimes occurred at this time. Copyright © 2008 John Wiley & Sons, Ltd. [source] Saltmarsh erosion and restoration in south-east England: squeezing the evidence requires realignmentJOURNAL OF APPLIED ECOLOGY, Issue 5 2005MINEKE WOLTERS Summary 1Saltmarshes in south-east England have been eroding rapidly since 1960. Recently, Hughes & Paramor (2004) and Morris et al. (2004) have presented contrasting views on the extent to which physical and biological processes might contribute to the erosion. There are three contentious issues: (i) saltmarsh erosion is the result of coastal squeeze, where sea walls prevent a landward migration of a saltmarsh in response to sea level rise; (ii) saltmarsh erosion is linked to bioturbation and herbivory of seedlings by the ragworm Nereis diversicolor; (iii) new saltmarshes will not develop on managed realignment sites where existing sea walls have been removed because of the effects of ragworms. 2In this paper, we provide a literature review of physical and biological processes relevant to the above three issues, and discuss the relative importance of these processes at different spatial and temporal scales. 3Our synthesis shows that, at a regional scale, the combination of strong winds, high tides and increased wave height appears to be responsible for the increased rate of marsh erosion and creek dissection recorded in the 1970s. There is also some laboratory evidence that bioturbation and herbivory from populations of Nereis can lead to sediment instability and loss of pioneer plant species, such as Salicornia spp. However, the field evidence is more equivocal and has been conducted at small spatial scales. 4At a large number of different managed realignment sites there is strong evidence that even if bioturbation and herbivory by Nereis have occurred, overall the effects have been insufficient to restrict plant succession of exposed sediment. 5Synthesis and applications. There is an urgent need for long-term field studies that integrate and quantify physical and biological processes and the related feedbacks at different spatial and temporal scales. Until this is completed, terms such as coastal squeeze will remain contentious and management decisions will invite criticism. [source] 83 Comparative analysis of vertically migrating euglena viridis populations in tidal and non-tidal benthic environmentsJOURNAL OF PHYCOLOGY, Issue 2003M.B. KingstonArticle first published online: 12 JAN 200 Benthic populations of Euglena viridis exhibit vertical migration behavior on high energy intertidal beaches and along the sand banks of freshwater streams. This study examines similarities and differences in the migratory behavior and cell morphology of populations of E. viridis inhabiting Scripps Beach, La Jolla, California and Coble Brook, Burlington, North Carolina. The timing of migration was measured by counting the number of cells in samples collected from the sediment surface throughout the day. Sediment cores were extracted and sectioned to determine the vertical distribution of the population. Neutral density filters and opaque canisters were used to shade the substratum to 56%, 22%, 2%, and 0% of incident irradiance (Io) to examine the effect of light on cell morphology and migratory behavior. On intertidal beaches, E. viridis exhibited a tidal rhythm in vertical migration with cells migrating below the sediment surface at night (>15 cm) and during daytime high tides. In this habitat, the upward migration response was enhanced at irradiances lower than 100% Io but cell morphology was not altered by shading. On the banks of freshwater streams, E. viridis exhibited a diurnal migratory rhythm with both tear-drop and spherical morphologies observed throughout the day. The population was most concentrated at the surface around solar noon and at night it was located between 1 and 2 cm below the surface. Shading did not enhance upward migration but it did affect cell morphology. These results will be interpreted in the context of the dominant selection pressures in each environment. [source] | |||||||||||||