Effects Of Tidal Cycles Research Articles

Effects of tidal cycles on the variability of microbial communities in a semiclosed bay

Shallow sediment-water plays an important role in transforming organic matter in estuaries. As a shallow bay often flanks a large estuary, the estuarine water enters the shallow bay during flood tides and exits during ebb tides. The inundation between flood and ebb tides in the shallow bay serves as an incubation of the bay water and sediment. However, little is known about the effects of tidal cycles on microbial diversity and biogeochemical processes. In Tangjiawan Bay, which is a small bay located on the west side of the Pearl River estuary, we examined changes in microbial diversity and environmental factors by collecting surface water samples between floods and ebbs. Using high-throughput sequencing targeting 16S and 18S rRNA genes, the results indicated that between floods and ebbs, the community composition of bacteria and eukaryotes differed significantly, the alpha diversity of bacteria and eukaryotes differed significantly, with floods harboring higher diversity. The analysis of RDA suggested that salinity and TOC were important in explaining community variation in both bacteria and eukaryotes. Moreover, the co-occurrence networks between bacteria and eukaryotes showed higher negative relationships in ebbs (83.87%) than in floods (64.29%), suggesting increased interactions between bacteria and eukaryotes during ebbs as the water was incubated in the bay. These findings demonstrated the dynamics of biogeochemical processes of nutrients and plankton communities in the shallow bay and tidal cycles are a dominant driving force in regulating variability in phytoplankton and bacterial community and the sediment-water interface exchange. The results indicate that we should not overlook at the importance of shallow water column fringing the shore lines.

Effects of tidal cycle on greenhouse gases emissions from a tropical estuary

The potential effects of tidal and diel cycles on fluxes and concentrations of carbon dioxide (pCO2), methane (CH4), and nitrous oxide (N2O) along with associated biogeochemical processes remain poorly understood in tropical estuaries. The present study, based on six-hourly sampling for nine consecutive days at three locations along the salinity gradient in the Mahanadi estuary of India, revealed that the tidal forcing affected pCO2 and CH4 in the mixing zone with elevated concentrations during low tide with maximum concentrations up to 21,606 μatm and 285 μM, respectively. pCO2 increased with decrease in tidal height within low and high tide duration as well, possibly due to higher relative contribution of freshwater with high CO2. N2O, on the other hand, showed no significant variability with tidal cycle or water level fluctuation during high and low tide. Barring the offshore region, the study area was source of greenhouse gases to the atmosphere.

Transport of Microplastics in Shore Substrates over Tidal Cycles: Roles of Polymer Characteristics and Environmental Factors.

Tidal zones providing habitats are particularly vulnerable to microplastic (MP) pollution. In this study, the effects of tidal cycles on the transport of MPs (4-6 μm polyethylene, PE1; 125 μm polyethylene, PE2; and 5-6 μm polytetrafluoroethylene, PFTE) in porous media combined with various environmental and MPs properties were systemically investigated. The results indicated that smaller substrate sizes exhibited higher retention percentages compared to those of larger substrate sizes under different tidal cycles. In terms of the size of MPs, a larger size (same density) was found to result in enhanced retention of MPs in the column. As the number of tidal cycles increased, although the transport of MPs from the substrate to the water phase was enhanced, PE1 was washed out more with the change in water level, compared to PTFE. Additionally, more MPs were retained in the column with the increase of salinity and the decrease of flow velocity under the same tidal cycles. Ultraviolet and seawater aged PE1 showed enhanced transport, while aged PTFE showed enhanced retention under the same tidal cycles. These results can help understand the MP behaviors in the shoreline environment and provide support for future cleanup and sampling in tidal zones.

Survey of Khor Al-Zubair and Umm Qasr Mudflat Birds: Effect of Tidal Cycle and Seasonal Variations on Their Assemblages and Abundance, Basrah, Iraq

Ornithological surveys were conducted at tidal mudflats that nationally represents one of the marine key biodiversity (KBA) areas at Khor Al-Zubair (KBZ) and Umm Qasr south-east of Basrah City, Iraq. On the basis of hourly counting for 7h monitoring period at day time and covering an area of 7.5 km2 of the intertidal zone, a 7 surveys were conducted from March 2019 until January 2020. A total of 7658 individual birds belongs to 54 species have been recorded. The highest numbers of birds per a day were recorded in Autumn and Winter 4869, 1999 respectively, which coincided with the migration seasons. The lowest numbers were recorded during the Summer season just where only 61 birds have been observed. The birds assemblages and their abundance during the high tide times and during the low tide times were compared statistically and the results weren’t different (t < 0.05). Additional observations of different surveys targeted different sites of the KAZ mudflat over the period 2005-2020 have resulted in a final list consists of 102 bird species, a result reflecting the importance of this habitat to various migratory and resident birds.

Effect of Tidal Cycle on Escherichia coli Variability in a Tropical Estuary.

A faecal indicator bacteria, Escherichia coli (E. coli), is widely used in monitoring health of estuaries, where tidal amplitude plays a critical role in its variability. Mahanadi estuary, formed at the mouth of a major tropical river Mahanadi, has large socio-economic importance. This anthropogenically stressed estuary remains understudied with respect to E. coli. Hence, this study addressed E. coli variability in Mahanadi estuary with novel sampling strategy that can be implemented at other tropical estuaries. The sampling strategy includes simultaneous measurements, at lesser-saline upper-estuary and higher-saline lower-estuary, over a tidal cycle. Although no significant variability of E. coli was observed between upper and lower-estuary, overall average count was higher during low tide and lower during high tide attributed to salinity fluctuations. Intermittent surpass of E. coli counts above recommended limits in Mahanadi estuary, indicated potential health risk, thus demands for frequent water quality monitoring and management strategies.

External Corrosion Of Pipe Riser API 5L X52 On Tidal Zone Of Offshore Production Platform

External corrosion on mature oil and gas field installation very challenging issues. External corrosion of pipeline riser on tidal zone is the most case for pipeline corrosion [2]. API 5L X52 is familiar pipeline for offshore oil and gas production facilities. Pipeline riser external corrosion on tidal zone have some consequences, time constrain related tidal cycle, production loss, oil spill impact to company reputation, costly maintenance. This research intended to find out effect of tidal cycle and salt water salinity to the rate and type of corrosion on API 5l X52 pipeline riser. Tidal cycle is modeling by wet and dry coupon on salt water. Corrosion rate measure by weight loss coupon. Corrosion product examine by XRD. Chloride contents and oxygen dissolve combination resulting maximum corrosion rate. Oxygen dissolve is main factor to corrosion on salt water. Maximum oxygen dissolve on salt water concentration 3.5% wt. On high salinity salt water corrosion rate depend oxygen dissolve [2]. Tidal cycle has impact to corrosion rate. General corrosion type happen on all coupon with corrosion product component Fe 2 O 3 , Fe 3 O 4 examined by XRD.

Effects of tidal cycles on shorebird distribution and foraging behaviour in a coastal tropical wetland: Insights for carrying capacity assessment

Wetland loss has driven negative effects on biodiversity by a reduction in potential available habitats, directly impacting wetland-dependent species such as migratory shorebirds. At coastal areas where tidal cycles can restrict food access, the degree to which density of foraging birds is mediated by conspecific abundance or by the available areas is crucial to understanding patterns of bird distribution and wetland carrying capacity. We used the bathymetry of two sectors modeled with two numerical matrices to determine the availability of intertidal foraging areas in relation to tidal level (spring and neap tides), and this information was used to estimate shorebird density and foraging activity throughout the low-tide cycle in a tropical coastal lagoon in northwestern Mexico. Relative to spring tides, an 80% reduction in available foraging areas occurred during neap tides. Overall shorebird abundance was significantly reduced during neap tide periods, with differences between species. Densities of shorebirds increased during neap tides, particularly in one sector, and remained similar throughout the low-tide period (i.e. 4 h) either during spring or neap tides. Time spent foraging was consistently lower during neap-tides relative to spring-tides, especially for Long-billed curlew (44% reduction), Willet (37% reduction) and Black-necked stilt (29% reduction). These decreases in foraging activity when available habitats became reduced can hamper the opportunities of migratory shorebirds to reach their daily energy requirements to survive during the non-breeding season. This study shows that when intertidal habitats are severely reduced an important fraction of shorebird populations would probably be forced to find alternative areas to forage or increase foraging time during the night. Serving an essential function as top-predators, these results can have important implications on carrying capacity assessment for shorebirds at coastal wetlands.

Petroleum hydrocarbon contaminations in the intertidal seawater after the Hebei Spirit oil spill – Effect of tidal cycle on the TPH concentrations and the chromatographic characterization of seawater extracts

In December 2007, the oil tanker Hebei Spirit released approximately 12,547,000 L of crude oil off the west coast of Korea, impacting more than 375 km of coastline. The seawater TPH concentrations immediately after the spill ranged from 1.5 to 7310 μg L−1, with an average of 732 μg L−1. The concentrations appeared to decrease drastically to 2.0–224 μg L−1 in one month after the spill. The TPH concentrations in seawater fluctuated with time thereafter because of the remobilization of oil by continuing shoreline cleanup activities and subsequent wave/tidal actions. Seawater TPH concentrations were much higher during high tide than during low tide due to the resuspension of stranded oil. The variation of TPH levels in seawater also matched the spring-neap tidal cycle in the study areas for the first three weeks of the study. Comparisons of the gas chromatograms of the seawater with the water accommodated fraction and the cargo oil indicated that seawater samples were contaminated mainly by the dispersed droplets of spilled oil. One year of monitoring revealed that the oil content in seawater had clearly decreased at most sites, although some regional fluctuations of oil contamination were noted until June 2008.

The Effect of Tidal Cycles on the Community Structure of Plankton (with Emphasis on Copepods) at Afmed Marina in Winter (A Preliminary Study)

Tidal cycles had no significant effect on the abundance or community structure of plankton at AFMED (Aquaculture, Fisheries and Marine Environment Department) Marina, nor had any physicochemical factor, except salinity, on the density of copepods (p &lt; 0.05), although variation in the physichochemical data measured was small. The major components of the plankton community throughout the study were copepods, Noctiluca spp. (mostly N. scintillans (Macartney) Kofoid &amp; Swezy), and cirripede nauplii. Their abundance differed between high and low tides throughout the study. Variation between high and low tides was also observed among the various groups and species of copepods. MDPs (Mean Density Percentages) of calanoids, copepod nauplii, and poecilostomatoids were higher at high tide (45%, 20.09%, and 2.81%, respectively), while cyclopoid and harpacticoid MDPs were higher at low tide (30.63% and 9.95%, respectively). The most dominant copepods were Parvocalanus crassirostris (F. Dahl, 1894), Paracalanus spp., Oithona simplex Farran, 1913, Euterpina acutifrons (Dana, 1847), Oncaea spp., and Corycaeus spp. The copepods with the highest MDPs at high tide were Parvocalanus crassirostris (14.19%), Paracalanus spp. (10.79%), Oncaea spp. (1.75%) and Corycaeus spp. (1.06%), respectively, while Oithona simplex and Euterpina acutifrons had a higher MDP at low tide (14.97% and 9.12%, respectively). The highest MDP at low tide was that of Oithona simplex. Neither tide nor any other factor measured had a significant effect on any of the copepods. Other, related factors (mainly biological and anthropogenic) may thus have accounted for the differences in abundance and biodiversity observed.

Effect of tidal cycle and food intake on the baseline plasma corticosterone rhythm in intertidally foraging marine iguanas

In most species, plasma levels of baseline glucocorticoids such as corticosterone (B) have a circadian rhythm. This rhythm can be entrained by both photoperiod and food intake and is related to aspects of energy intake and metabolism. Marine iguanas ( Amblyrhynchus cristatus) offer a unique opportunity to better understand the relative importance of the light:dark cycle versus food intake in influencing the rhythm in baseline B in a natural system. Compared to other species, food intake is not as strictly determined by the phase of the light:dark cycle. Animals feed in the intertidal zone so feeding activity is heavily influenced by the tidal cycle. We measured baseline plasma B levels in free-living iguanas over several 24-h periods that varied in the timing of low tide/foraging activity. We found that baseline B levels were higher during the day relative to night. However, when low tide occurred during the day, baseline B levels dropped coincident with the timing of low tide. Whether the baseline B rhythm (including the drop during foraging) is an endogenous rhythm with a circatidal component, or is simply a result of feeding and associated physiological changes needs to be tested. Together, these data suggest that the baseline B rhythm in marine iguanas is influenced by the tidal cycle/food intake as well as the light:dark cycle.

Reconstructing daily temperatures from growth rates of the intertidal bivalve mollusk Chione cortezi (northern Gulf of California, Mexico)

We establish a model for the reconstruction of average daily sea surface temperatures from calcification rates of an intertidal bivalve mollusk. The rate of shell production in Chione cortezi (Carpenter, 1864, ex Sloat MS) is mainly controlled by water temperature, ontogenetic age and the effect of tidal cycles. Statistical methods developed by dendrochronologists can successfully extract the water temperature signal from daily growth increment chronologies. After removal of noise, the growth rates are expressed as scaled daily growth indices. Average daily water temperatures during the first half of the year are highly correlated with the scaled daily growth index values of recent and subrecent specimens, using the multi-valued function presented here. Increment width analysis can reconstruct daily average water temperatures with a mean error of less than 3%. This technique provides an independent method for reconstructing temperatures in fossil specimens of species with living representatives and can supplement high-resolution temperature reconstructions based on geochemical analysis.

Pelagic diatom assemblages are good indicators of mixed water intrusions into Saanich Inlet, a stratified fjord in Vancouver Island

Abstract We assessed the potential importance of tidally-driven intrusions of autochthonous protistan plankton into Saanich Inlet, a fjord in Vancouver Island, as potential sources of fossils in the fine intra-annual sediment laminations of ODP cores. We determined the structure of protistan assemblages throughout the Inlet during July 1995 at times of successive neap and spring tides. Results were compared to a concurrent physical study of tidal flows and nutrient advection into and out of the Inlet, which allowed us to identify protistan species indicative of mixed Satellite Channel and stratified Saanich Inlet waters. These identifications were either confirmed or rejected by temporal analyses of protistan assemblages based on weekly sampling at two fixed positions, one in Saanich Inlet and one in Sidney Channel from May through October 1997. Results of both studies supported the hypothesis that the presence of a suite of diatom species, including most Chaetoceros spp., a large-celled variant of Skeletonema costatum and Thalassiosira rotula indicates the intrusion of water with elevated levels of dissolved inorganic nitrogen into Saanich Inlet from the Strait of Georgia. This indicator group of species contained additional species, but not all were observed in large numbers in 1997. Many of these species are important components of the laminated sediments of Saanich Inlet, whose presence is probably indicative of paleo-environmental conditions in the southern Strait of Georgia rather than Saanich Inlet. Effects of tidal cycles on dinoflagellate and other flagellated cells, exclusive of mastigophorans, were inconclusive and additional studies are required to elucidate details of their ecology in waters of the southern Strait of Georgia.

Effect of Tidal Cycles on Loggerhead Sea Turtles (Caretta caretta) Emerging from the Sea

Effect of Tidal Cycles on Loggerhead Sea Turtles (Caretta caretta) Emerging from the Sea