Simulated Tidal Conditions Research Articles

Intertidal habitat complexity influences the density of the non-native crab Hemigrapsus sanguineus.

Habitat structural complexity can provide protection from predators, potentially affecting population density of native and non-native prey. The invasive Asian shore crab, Hemigrapsus sanguineus, occurs in variable densities in the rocky intertidal zone of eastern North America and northern Europe, often in densities greater than in its native range. The present study examined the influence of habitat complexity on the density of H. sanguineus. Artificial shelters of concrete pavers with stones arranged in increasing complexity were deployed in the intertidal zone along a rocky shore in southeastern Massachusetts, USA, for 21 consecutive weekly intervals in 2020. Crabs consistently reached the highest densities in the most complex shelters despite their lower internal surface area. In addition, crabs exhibited shelter selectivity based on body size, with large crabs occupying artificial shelters in greater numbers than adjacent natural substrate. In a subsequent lab study, crab activity over 1 h was observed in the presence of the same artificial shelters, under simulated tidal conditions. Shelter complexity had little influence on the number of crabs under the pavers although crabs were more active when submerged in water than exposed to air. These results show that crab density increases as habitat complexity increases, and complexity may serve as a predictor of H. sanguineus density but not short-term behavior.

Effect of Tidal Cycles on Bacterial Biofilm Formation and Biocorrosion of Stainless Steel AISI 316L

The effects of tidal cycles associated with the water level on the biocorrosion of stainless steel AISI 316L were studied. Steel coupons were exposed to different conditions of immersion in mesocosms fed by fresh seawater either continuously or in accordance with the periodicity of natural tides. After 5 and 15 weeks, all coupons were found to have undergone ennoblement associated with the formation of a biofilm. Analysis of the composition of the bacterial community using denaturing gradient gel electrophoresis (DGGE) revealed differences in the biological succession. After 15 weeks, exposure to the simulated tidal conditions resulted in biofilms with lesser bacterial richness; the corresponding rate of corrosion, as determined by weight loss, was about 40 times lower compared to the case for the continuous exposure to seawater. Phylogenetic analysis of selected DGGE bands and the inspection of biofilm morphologies revealed that the faster rate of corrosion was associated with the presence of iron-oxidizing Zetaproteobacteria and eukaryotic photosynthetic microorganisms. On the other hand, intermittent exposure to seawater resulted in the succession of microorganisms resistant to the stress associated with sudden environmental changes, which was associated with a low rate of corrosion.

Rapid formation of iron sulfides alters soil morphology and chemistry following simulated marsh restoration

Many marshes show signs of degradation due to fragmentation, lack of sediment inputs, and erosion which may be exacerbated by sea level rise and increasing storm frequency/intensity. As a result, resource managers seek to restore marshes via introduction of sediment to increase elevation and stabilize the marsh platform. Recent field observations suggest the rapid formation of iron sulfide (FeS) materials following restoration in several marshes. To investigate, a laboratory microcosm study evaluated the formation of FeS following simulated restoration activities under continually inundated, simulated drought, and simulated tidal conditions. Results indicate that FeS horizon development initiated within 16 days, expanding to encompass >30% of the soil profile after 120 days under continuously inundated and simulated tidal conditions. Continuously inundated conditions supported higher FeS content compared to other treatments. Dissolved and total Fe and S measurements suggest the movement and diffusion of chemical constituents from native marsh soil upwards into the overlying sediments, driving FeS precipitation. The study highlights the need to consider biogeochemical factors resulting in FeS formation during salt marsh restoration activities. Additional field research is required to link laboratory studies, which may represent a worst case scenario, with in-situ conditions.

Site Selection Appraisal for Tidal Turbine Development in the River Mersey

This paper used a specialist software package to produce a detailed model of the River Mersey estuary, which can be subjected to a range of simulated tidal conditions. The aim of this research was to use the validated model to identify the optimal location for the positioning of a tidal turbine. Progress was made identifying a new optimal site for power generation using velocity data produced from simulations conducted using the MIKE 3 software. This process resulted in the identification of site 8, which sits mid-river between the Morpeth Dock and the Albert Dock, being identified as the favoured location for tidal power generation in the River Mersey. Further analysis of the site found that a 17.2-m diameter single rota multidirectional turbine with a 428-kW-rated capacity could produce 1.12 GWh annually.

Physiological performance of intertidal coralline algae during a simulated tidal cycle.

Intertidal macroalgae endure light, desiccation, and temperature variation associated with sub-merged and emerged conditions on a daily basis. Physiological stresses exist over the course of the entire tidal cycle, and physiological differences in response to these stresses likely contribute to spatial separation of species along the shore. For example, marine species that have a high stress tolerance can live higher on the shore and are able to recover when the tide returns, whereas species with a lower stress tolerance may be relegated to living lower on the shore or in tidepools, where low tide stresses are buffered. In this study, we monitored the physiological responses of the tidepool coralline Calliarthron tuberculosum (Postels and Ruprecht) E.Y. Dawson and the nontidepool coralline Corallina vancouveriensis Yendo during simulated tidal conditions to identify differences in physiology that might underlie differences in habitat. During high tide, Corallina was more photosynthetically active than Calliarthron as light levels increased. During low tide, Corallina continued to out-perform Calliarthron when submerged in warming tidepools, but photosynthesis abruptly halted for both species when emerged in air. Surprisingly, pigment composition did not differ, suggesting that light harvesting does not account for this difference. Additionally, Corallina was more effective at resisting desiccation by retaining water in its branches. When the tide returned, only Corallina recovered from combined temperature and desiccation stresses associated with emergence. This study broadens our understanding of intertidal algal physiology and provides a new perspective on the physiological and morphological underpinnings of habitat partitioning.

Durability-Based Ranking of Typical Structural Repairs for Corrosion-Damaged Marine Piles

Corrosion damage is a main cause of deterioration for concrete marine structures. It has become increasingly important to rehabilitate structures and develop repair techniques that prolong their life cycles. This investigation compares the performance of recognized repair techniques, in terms of corrosion resistance, structural integrity, and cost-effectiveness. Eight sets of three cylindrical piles were prepared to conduct seven types of repairs with one control set. Following initial exposure to corrosion, the specimens were repaired using the proposed techniques and tested for durability under simulated tidal conditions, with corrosion monitoring, determination of time-to-corrosion threshold, and visual inspections. The structural integrity was determined by crack scoring and ultimate load testing, and synthesized with a cost-effectiveness evaluation to rank the repair techniques. The repairs comprising carbon wrapping, high-density polyethylene (HDPE) jacketing, and MMFX steel outperformed the others, slurry-infiltrated fibrous concrete (SIFCON) repair, styrene-butadiene grout with woven roving fabric wrapping, normal concrete repair with spliced fiberglass reinforcing plastic (FRP) (glass) reinforcement, and the modified ASANO refresh method.

Impact of Iron Amendment on Net Methylmercury Export from Tidal Wetland Microcosms

Tidal wetlands can be important sources of methylmercury (MeHg) in aquatic ecosystems. As a result, wetland restoration could increase MeHg concentrations. Previous research has shown that addition of Fe[II] to wetland sediment can reduce MeHg production by decreasing concentrations of bioavailable Hg complexes with dissolved sulfur species. In this study, the potential for reducing MeHg production via an iron amendment was evaluated in laboratory microcosms that used intact sediments from a tidal marsh in San Francisco Bay. The microcosms were maintained under simulated tidal conditions and amended at four iron doses (0, 180, 360, and 720 g-Fe/m(2)). Two experiments were conducted: one with devegetated sediments and one with live wetland vegetation. Following iron addition to the devegetated sediments, porewater S[-II] concentrations decreased for each dose relative to the control with the average weekly export of MeHg in the surface water decreased by 82% and 89% for the two highest doses, respectively. Despite substantial variability within treatment groups, similar trends were observed for the vegetated microcosms. The results suggest that iron addition has the potential to provide a landscape-scale control on MeHg released by restored tidal wetlands; however, additional research is required to evaluate the efficacy of this approach under field conditions.

Larval hatching in the horseshoe crab, Limulus polyphemus: facilitation by environmental cues

Female horseshoe crabs, Limulus polyphemus (Linnaeus), lay their eggs in nests on sandy beaches near the high water line. Embryos develop within the sand, hatch into trilobite larvae, and enter the water column when the nest is inundated. Given the diversity of tidal and shoreline inundation patterns that populations of L. polyphemus experience throughout their range (semidiurnal and diurnal tides, microtidal, and nontidal), hatching may also be facilitated by environmental triggers that serve to synchronize hatching and larval emergence with periods of high water. The objective of this study was to determine if larval hatching in L. polyphemus is triggered or facilitated by environmental cues. Stage 21 embryos were subjected to one of seven different treatments that simulated conditions experienced during inundation: (1) hydration, (2) agitation, (3) hydration and agitation, (4) hydration and agitation with sand, (5) osmotic shock, (6) terrestrial hypoxia, and (7) aquatic hypoxia. Hatching rates increased significantly under all simulated tidal conditions compared to controls and were highest (96%) for eggs simultaneously exposed to both hydration and agitation with sand. Measurements of the osmolarity of the perivitelline fluid of developing eggs collected from the field indicated that it is hyperosmotic to the ambient seawater and porewater. Thus, when inundated, eggs also experience a hypoosmotic shock, which would likely facilitate hatching by causing the eggs to swell, rupturing the egg membrane and thereby increasing the likelihood that larvae would hatch and enter the water column during periods of high water.

Differences in the swimming behaviour of the amphipod Corophium volutator from different populations

The swimming behaviour of Corophium volutator from Wales and East Anglia was investigated to establish whether differences apparent from two previous studies are real or artefacts of the different techniques used. Swimming C. volutator were caught in a Welsh estuary in the summer, but only rarely in the autumn and winter, and in both daylight and darkness. In simulated tidal conditions in the laboratory C. volutator from two sites in East Anglia never swam, while those from Wales swam whenever the substratum was immersed, in daylight and darkness, mostly on the ebb tide and in winter. The unnatural swimming in winter may have been stimulated by laboratory conditions, but the East Anglian amphipods were not so affected. The tidal swimming rhythm is different to east coast C. volutator which only swim at night. This difference may be related to the time of spring tides, when most swimming occurs. In Wales high water of spring tides may occur only in daylight in summer and nocturnal swimming may not be possible. The ebb tide swimming by C. volutator in Wales contrasts with the flood and ebb swimming of east coast amphipods and may reflect differences in their habitats. The former were collected close to the sea while the latter were 15 km up a narrow estuary and may represent a sub-population of amphipods with a disposition to swim early (on the flood tide) enabling them to colonise upstream habitats.

Root Aeration and Respiration in Young Mangrove Plants (Avicennia marina(Forsk.) Vierh.)

Curran, M., Cole, M. and Allaway, W. G. 1986. Root aeration and respiration in young mangrove plants (Avicennia marina (Forsk.) Vierh.).—J. exp. Bot. 37: 1225-1233. The roots of young plants of Avicennia marina (Forsk.) Vierh. grown under simulated tidal conditions were harvested so as to obtain the entire root system. The roots were subdivided and weighed and subsamples taken for manometric determination of respiration rates at different temperatures. The supply capacity of the above-ground portion of the root system was determined and the results compared in terms of supply and demand. The oxygen consumption rate of the roots at 15 °C was found to be 1-69 + 007 ?tmol kg1 s1 for cable roots and 3-27 + 0-12 /rmol kg-1 s_1 for fine roots. The gio for respiration was 2-55 for oxygen consumption in both fine and cable roots, and for carbon dioxide production was 2-66 for fine roots and 04 for cable roots. The respiratory quotient varied with temperature but was less than unity. Concentration differences of between 1-8 mol m and 3-4 mol m 3 between the inside of root and the air were sufficient to permit aeration of the root system by diffusion alone, and the aerenchyma contained sufficient oxygen to maintain aerobic conditions while the roots were covered with water. The effect of tide and seasonal temperature change on gas exchange, together with the possibility of some form of carbon dioxide fixation within the root, are examined and the implications of these effects on growth and development are discussed.

Impact of dispersed and undispersed oil entering a gulf coast salt marsh

AbstractThe effect of dispersed and undispersed South Louisiana crude oil on the growth of Spartina alterniflora and associated meiofaunal communities was investigated in a replicated experiment conducted in a uniform Louisiana salt marsh. The oil and the oil plus dispersant were applied to open water adjacent to the marsh and forced onto the marsh, using a pump to create a “head” of water that simulated tidal conditions. Neither crude oil nor oil plus dispersant had any inhibitory or stimulatory effect on the growth of S. alterniflora or the meiofaunal communities, including the meiobenthos.

Observations on the tidal activity rhythm of the periwinkleLittorina nigrolineata(Gray)

The spontaneous activity pattern of the periwinkle L. nigrolineata has been studied by direct observation in the field and under controlled conditions in the laboratory. In the laboratory the animals are induced to crawl by both immersion and exposure under simulated tidal conditions, and the increased activity following emersion has been confirmed by field observations. Animals kept submerged under constant conditions show an endogenous activity rhythm with a free running period of about 12 to 13 hours. The main activity periods occur about 2 hours after the onset of inundation and the rhythm rephases almost immediately to the time of immersion. There is also evidence for a further endogenous component with peaks corresponding to the time of subjective emersion. The rhythm is modulated on a circadian basis, and is less pronounced during the neap tide period, and during the winter months.

Entrainment of a semilunar rhythm by simulated tidal cycles of mechanical disturbance

The semilunar rhythm of pupation and succeeding emergence in populations of the intertidal midge Clunio marinus Hal. can be entrained by the combination of a 24-h light-dark cycle and a 12.4-h cycle of simulated tides, both of which recur in characteristic phase relationships every two weeks (collectively designated as ‘semi-monthly zeitgeber cycle’). The effective tidal factor in simulated tidal conditions was the mechanical disturbance of the water which is correlated with turbulence, underwater sound, and bottom vibrations. The experiments induced underwater sound of 50–200 cps, 20–30 dB above background noise level, and of 6 h duration per tidal cycle, which corresponded well with the conditions in nature. It is supposed that tidal turbulence and vibration result in mechanical stimulation of the larvae. Tidal changes of hydrostatic pressure and light intensity were ineffective as zeitgeber. The phase relationship between the semilunar rhythm and the semi-monthly zeitgeber cycle is a population-specific property as demonstrated by stocks from two locations with different tidal schedules (Helgoland and Normandy). Comparing experimental data and field data, this phase relationship represents a successful genetic adaptation to geographic differences in the phase of tides.