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The content of nonstructural carbohydrates (glucose, fructose, sucrose, starch) and activities of sucrose-utilizing enzymes (vacuolar, apoplastic, and cytoplasmic invertases, as well as sucrose synthase) were examined in halophyte plants Triglochin maritima L. (sea arrowgrass), Tripolium vulgare Ness. (sea aster), and Glaux maritima L. (sea milkwort) inhabiting the littoral zone of the White Sea coast. Studies of plants growing in tidal cycle conditions revealed species-specific differences in sugar content and the activity of sucrose-metabolizing enzymes. T. maritima featured high concentrations of monosaccharides in leaves and elevated content of sucrose and storage starch in underground organs. T. vulgare was characterized by low monosaccharide content and the activated synthesis of sucrose that is deposited in stems and plays the main role in maintaining the plant osmotic balance. G. maritima occupies a special place: unlike other species, it accumulates abundant starch reserves in aboveground and underground organs. This species is a crinohalophyte. Its protection against ion toxicity is mediated by the release of excess toxic ions via salt-removing glands, while mineral nutrition is assisted by the mycorrhiza. The above differences show that various littoral species adapt to salinity conditions in different ways, depending on their origin and biological features. [ABSTRACT FROM AUTHOR]

Biological processes in intertidal species follow tidal rhythms that enhance survival and fitness. Whereas tidal effects on behaviour and metabolic rates have been widely studied, impacts on other key process such as protein synthesis are still poorly understood. To date, no studies have examined the effect of immersion/emersion and tidal cycles on protein synthesis rates (ks). Patella vulgata is an intertidal limpet present in North-Eastern Atlantic rocky shores from high to low shore. Previously reported P. vulgata respiration and heart rate measurements suggest aerobic metabolism is maintained during emersion and growth rates increase from high to low shore, but whether these patterns are reflected in ks is currently unclear. Here, we measured for the first time in any intertidal organism, ks, RNA to protein ratios and RNA translational efficiency (kRNA) in P. vulgata over a full tidal cycle, at three different shore heights. ks increased during emersion (p < 0.001) and was significantly higher in low shore animals compared to the other shore heights (p < 0.001), additionally ks was negatively correlated to body mass (p = 0.002). RNA to protein ratios remained unchanged over the tidal cycle (p = 0.659) and did not vary with shore height (p = 0.591). kRNA was significantly higher during emersion and was also higher in low shore limpets (p < 0.001). This study demonstrates that P. vulgata increases ks during emersion, an important adaptation in a species that spends a considerable amount of its lifecycle emersed. Intertidal species are highly exposed to increasing air temperatures, making knowledge of physiological responses during emersion critical in understanding and forecasting climate warming impacts. [ABSTRACT FROM AUTHOR]

The carbon cycle process of coastal ecosystems is extremely complex subjected to the coupling effects of hydrodynamics from land and sea. To investigate the distribution and biogeochemistry of organic carbon in estuaries area, particulate organic carbon (POC) and dissolved organic carbon (DOC) in water and total organic carbon (TOC) in surface sediments were measured over four tidal cycles at Sanjiagang (121.8°E, 31.2°N) in the Yangtze River estuary (YRE) from November 2022 to February 2023. Our results showed that the concentration of POC and DOC in water was positively correlated during the autumn and winter. Additionally, the significant positive correlation between tidal elevation and TOC concentrations indicated that organic carbon accumulation to estuarine areas was greatly influenced by tides. According to the principal component analysis (PCA) and stepwise multiple regression, the tidal dynamics and physicochemical properties of water, including salinity, dissolved oxygen (DO), temperature, turbidity, and pH, showed significant correlations to organic carbon. DOC and TOC concentrations were significantly higher in autumn than in winter. Due to the tidal asymmetry in the YRE, the POC and DOC concentrations during ebb tides were higher than those during flood tides. Furthermore, the influence of hydrometeorological conditions such as monthly precipitation and average temperature on the accumulation of organic carbon cannot be ignored in coastal areas. In addition, the grey correlation analysis revealed that strong relevance between the development of the processing manufacturing industry and the TOC in sediments at Site SJG. The socio-economic development and anthropogenic activities along the YRE interfered with the biogeochemical cycle of organic carbon through the massive discharge of wastewater and CO2. [ABSTRACT FROM AUTHOR]

The German Bight in the southern North Sea receives nutrients, dissolved organic matter (DOM), and trace metals from rivers, porewater reflux, and porewater outwelling. We studied the marine, riverine, and porewater sources analyzing molecular transformations of solid-phase extracted (SPE) DOM in the German Bight. We applied a combination of ultrahigh-resolution mass spectrometry (FT-ICR-MS) with quantitative data of dissolved organic sulfur (DOS), dissolved black carbon (DBC), dissolved trace metals (Ba, Co, Gd, Mo, Mn, W), and nutrients (nitrite, nitrate, phosphate, silicate). While aromatic DOM and DBC mainly originated from the rivers, nitrogen-containing, more saturated DOM was enriched offshore suggesting greater contributions of marine (algal) sources. Except for dissolved Mo, rivers were the primary source of trace metals and nutrients. However, tidal flats contributed to dissolved nutrient (e.g., dissolved phosphate), trace metal and DOS inventories of the southern North Sea. The input of DOS from intertidal flats was identified by the molecular index derived from sulfidic porewaters (ISuP), non-conservative behavior of elemental sulfur-to-carbon ratio and sulfur content of molecular formulae (from FT-ICR-MS). Dissolved Mn and Si were removed in the German Bight, likely due to precipitation as Mn(hydr)oxides and biological uptake, respectively. Preliminary estimates suggest that DOS from porewater outwelling is approximately four times higher than DOS discharged by the three main rivers in the region. Our study therefore highlights the need to consider porewater discharge in addition to riverine sources to comprehensively assess elemental budgets within the complex interplay and transformations of DOM, nutrients, and trace metals in coastal ecosystems. [ABSTRACT FROM AUTHOR]

The authors studied the composition of fatty acids (FAs) in four species of dominant obligate halophytes—Triglochin maritima, Plantago maritima, Tripoliumpannonicum subsp. tripolium, and Lysimachiamaritima—growing in different flood conditions in the littoral zone of the White Sea. It was found that the content of total FA varied from 13 to 22 mg/g a.d.w. with maximum values in L.maritima and minimal in P. maritima. All species have high values of UFA content (74–77%), double bond index (1.6–1.8), and a significant contribution of triene FAs (45–55%). A high diversity of long-chain FAs (C20–24) was established: 14 FAs. This analysis showed the similarity of all halophytes in the main parameters of FA composition and the high functional activity of halophyte membrane systems. Two clusters of species with different adaptive responses have been identified: the first includes P. maritima, Triglochin maritima and Tripoliumpannonicum and the second includes L.maritima. A comparison of data for two clusters showed that there are FAs that are involved in the adaptation of all types of C18:3(n-3), C16:0, C18:2(n-6), and FAs that differ among clusters. For species of the first cluster, 1 FA is C20:4(n-4), and, for the second cluster, 4 FAs are C18:1(n-9), C18:3(n-4), C20:1(n-9), and C22:0. The revealed differences may be associated with different ways of adaptation of halophytes of the two clusters to littoral conditions. [ABSTRACT FROM AUTHOR]

Field hydrometric studies at the estuaries of the White Sea basin yielded data on some hydrodynamic features of reverse tidal currents. Among the mouth areas of tidal rivers studied in 2015–2022, the most interesting results were obtained at the mesotidal Kyanda estuary, flowing into Onega Bay, and at the macrotidal Syomzha estuary, flowing into Mezen estuary. The essence of the method used in the field studies is synchronic measurements of water flow by acoustic Doppler profilers and water levels by autonomous barometric recorders in two cross-sections, located at different distances from the river mouth, during an entire semidiurnal tidal cycle. The results of these measurements were used to evaluate the terms of Saint-Venant equation of motion and the roughness coefficients. It was found that in the tidal rivers, the flow resistance varies considerably during a tidal cycle. In periods of quasi-steady water flow in both directions during flood and ebb, the values of the Darcy–Weisbach friction factor are 0.04–0.07, as is typical for rivers with similar morphological channel pattern and characteristics. However, in several cases, in periods close to slack water, the friction factor took negative values. A possible explanation of this phenomenon is a negative turbulent viscosity, which manifests itself in some phases of the tidal cycle, when the energy of eddy formations can be transferred to the translational motion of the water mass. [ABSTRACT FROM AUTHOR]

In the fall of 2018, studies of suspended particulate matter and its organic part in the water column and their lateral flux on the Karelian coast of the White Sea were carried out. The concentration of suspended particulate matter varied from 0.42 to 0.93 μg/L, and the concentration of Corg ranged from 124 to 249 μg/L. In the water column, 25 registration taxa of phytoplankton were recorded; it was shown that its species composition changed from the surface to the bottom. The lateral flux values varied from 159 to 439 μg m–2 h–1. As part of lateral flux, 49 phytoplankton taxa were revealed. It was shown that, depending on the tidal cycle phase, not only the quantitative characteristics of the lateral flux of phytoplankton change, but also the species composition of microalgae. In the tidal phase, more organic matter enters the inner regions of the bays than is carried out from these areas to the low-tide phase. At high tide, the proportion of phytoplankton organisms in the lateral flux is more than 80%; at low tide, it is less than 55%. [ABSTRACT FROM AUTHOR]

Productive and ecologically highly valuable ecosystems, macrotidal estuaries are also characterised by complex habitat and connectivity dynamics driven by tidal and freshwater influence. Organisms living in these constantly changing systems have to match their movement patterns to the shifting habitat mosaic using available windows of connectivity to access habitat patches of interest. This appears particularly important for the juvenile stages of many fish species colonising shallow and intertidal areas of the estuaries as summer nurseries. We apply tools from landscape ecology to investigate the estuarine habitat and connectivity dynamics on the example of juvenile seabass (Dicentrarchus labrax). We test under which conditions spatio-temporal bottlenecks to estuarine nursery colonisation may emerge for this species in a human-modified estuary. Combining a hydrodynamic model of the Seine estuary with remote sensing data allows us to capture structural changes in habitat availability and connectivity at the estuarine scale and at a fine spatio-temporal resolution. With chronological least-cost modelling of successive tidal steps, we assess patterns of nursery accessibility and estimate tidal colonisation fronts for different mobility scenarios. We show that, at certain hydrological conditions, tidal water level variation causes local disruptions of habitat availability and connectivity, creating temporary bottlenecks for seabass juveniles' movement. Fish mobility appears determinant for their vulnerability to these connectivity disruptions. Our approach allows for quantitative assessment and visualisation of riverscape complexity related to tidal dynamics. It is applicable to other highly dynamic ecosystems, where the mobile nature of connectivity and habitats needs to be integrated into conservation and management planning. [ABSTRACT FROM AUTHOR]

Structural and functional traits in leaves of sea plantain (Plantago maritima L.) inhabiting intertidal and supratidal zones of the White Sea coast were studied. At the intertidal, the plants were found to have smaller and thicker leaves with more frequent stomata and thinner cover tissues in comparison with the plants collected from the supratidal. Leaf fluorescence and stomatal conductance obeyed the circadian rhythm in plants residing in the supratidal. The tested parameters considerably changed according to tidal dynamics in the intertidal plants. Two stable states (high and low tides) and two transition states (while water level ascends or descends) were defined. In both stable states, the plants demonstrated high functional parameters of fluorescence (Fv/Fm, Y(II), and ETR) and open stomata. In the transitional states, the stomata were partly closed, and the functional activity was inhibited. Leaf structural peculiarities, leaf gas films, the inducible CO2-concentrating mechanism, and the determining role of the stomata are considered in terms of the hypotheses explaining the responses of sea plantain to tidal dynamics on the White Sea coast. [ABSTRACT FROM AUTHOR]

Winter field campaigns conducted by the Department of Hydrology of the Moscow State University Geographical Faculty undertaken during winter periods of 2017–2020 are introduced. The estuarine zone of the Onega, Mezen, Varzuga, Umba, Kuzreka, Kyanda, and Tamitsa rivers, which flow into the White Sea, have been investigated. The methodology and preliminary analyses of tidal wave estuarine transformation, mixing zone dynamics, and ice cover formation are presented. [ABSTRACT FROM AUTHOR]

A new sedimentation device, the "lateral sediment flow meter", was developed and tested for taking samples of substances moving in the water column in lateral directions. The device can be successfully used for solving the sedimentological, biological and environmental problems, and the monitoring of solid pollutant transfers. [ABSTRACT FROM AUTHOR]

The complex, stratified seaweeds within kelp forests provide habitat to a multitude of organisms and can alter the physical and chemical parameters of their surrounding environment. It is unclear, however, how patterns in the architecture of these beds change as the tide ebbs and floods. We investigate biomass distribution of floating and stipitate canopies within a kelp bed during low and high slack tides to determine how biomass interacts with common environmental parameters (nutrients, light, and mass-transfer). Floating canopy biomass remained consistent despite differences in depth, likely driven by an interaction between stipe density and individual biomass. Biomass was distributed inconsistently throughout the water column, in which biomass at the surface roughly doubled at low tide relative to high. Despite an increase in kelp biomass at the surface of the water column during low tide, more light reached the benthos than at high tide, suggesting that seawater optical properties independent of algal canopy better explain light attenuation. Seawater nutrients were consistent throughout the bed. Rates of mass-transfer decreased from the exterior to the interior of the bed and also attenuated with depth. This study highlights the structural complexity of kelp beds and the localized effects on important environmental variables. [ABSTRACT FROM AUTHOR]

The quantitative contribution of tropical estuaries to the atmospheric CO2 budget has large uncertainties, both spatially and seasonally. We investigated the seasonal and spatial variations of carbon biogeochemistry downstream of Ho Chi Minh City (Southern Vietnam). We sampled four sites distributed from downstream of a highly urbanised watershed through mangroves to the South China Sea coast during the dry and wet seasons. Measured partial pressure of CO2 (pCO2) ranged from 660 to 3000 μatm during the dry season, and from 740 to 5000 μatm during the wet season. High organic load, dissolved oxygen saturation down to 17%, and pCO2 up to 5000 μatm at the freshwater endmember of the estuary reflected the intense human pressure on this ecosystem. We show that releases from mangrove soils affect the water column pCO2 in this large tropical estuary (~600 m wide and 10-20 m deep). This study is among the few to report direct measurements of both water pCO2 and CO2 emissions in a Southeast Asian tropical estuary located in a highly urbanised watershed. It shows that the contribution of such estuaries may have been previously underestimated, with CO2 emissions ranging from 74 to 876 mmol m−2 day−1 at low current velocity (< 0.2 m s−1). Corresponding gas transfer velocities k600, ranging from 1.7 to 11.0 m day−1, were about 2 to 4 times of k600 estimated using published literature equations. [ABSTRACT FROM AUTHOR]

In order to discuss the content distributions and fluxes of heavy metals in suspended matters during a tidal cycle in the turbidity maximum around the Changjiang (Yangtze) Estuary, the contents of heavy metals (Zn, Pb, Cd, Co and Ni) have been analyzed. During a tidal cycle, the average contents of heavy metals are in the order of Zn>Ni>Pb>Co≫Cd. The average contents in ebb tide are generally higher than that in flood tide. However, at the inshore Sta. 11, influenced by the contamination from the nearby waste treatment plant, the average contents of Zn and Ni in flood tide are higher than those in ebb tide and at the offshore Sta. 10, the content of Cd in flood tide higher than that in ebb tide due to marine-derived materials. The five heavy metals, mainly terrigenous, are transported towards east-northeast, and settle down with suspended matters in the area between Sta. 11 and Sta. 10. Influenced by marine-derived materials, the flux value of Cd does not alter significantly with obviously changing in flux direction towards northwest. The source of heavy metals, the salinity of water and the concentration of suspended matters are the main factors controlling the content distributions of heavy metals during a tidal cycle. There is a positive correlation between the contents of heavy metals (Zn, Pb, Co and Ni) and the salinity of water, while the opposite correlation between the contents and the concentrations of suspended matters. Because of marine-derived materials, the content of Cd is not correlated with the concentration of suspended matters and the salinity of water. [ABSTRACT FROM AUTHOR]

Tidally driven fluctuations lead to rapid variations in hydrological properties that can have profound effects on the dynamic and functions of salt marshes. During low tides, many nektonic species find refuge from predatory fish in shallow intertidal pools. The utilization of shallow pool refuges also exposes fishes to fitness costs that fluctuate between day and night. Yet, how aggregated fish using an intertidal pool modulate their schooling behavior over the diel cycle remains unknown. Using high-resolution imaging sonar (ARIS), we monitored an intertidal pool over a 3-day period and quantified fish abundance, size, and schooling behavior relative to the diel and tidal cycles. Higher fish abundance was found during low tides than high tides when the section was connected with the subtidal waters. At low tide, no differences in fish abundance and size were detected in the pool between day and night, but larger schools formed at night than day. Our results suggest that biotic and abiotic factors affecting fish schooling behavior in the low tide refuge may vary over the diel cycle. We present possible functional explanations for the shifts in schooling tendency between nocturnal and diurnal utilization of the pool. [ABSTRACT FROM AUTHOR]

Based on experiment in tidal flume, this paper analyzes the sediment rarefactive phenomenon and hydraulic characteristics of sediment resuspension with different physical properties under the effect of tidal current. According to this experiment, sediment resuspension is related to the hydraulic characteristics of overlying water and its own dry density, namely the moisture content of sediment and deposition time. Generally, river sediment can be classified into the upper layer of floating sludge and lower layer of deposit sediment. Incipient velocity goes higher as the sediment layer goes thicker. Based on the experiment, incipient velocity formula of sediment can be obtained. There is a cohesive force among natural fine sediment whose resuspension is almost irrelevant to their diameters. Therefore, the critical incipient velocity is determined by the cohesive force instead of particle diameter. The lower layer of deposit sediment is generally not so easy to start up. And it will be rarified and release into the overlying water when contacting with overlying water. However, this rarefaction release velocity is gentle and slow. Under the same flow condition, annual loss amount of lower layer deposited sediment is about one fifth of upper layer of floating sediment. Flow velocity of tidal river and variation of the water level are asymmetrical, both of which vary under different tidal cycles. During long tidal cycle, flow velocity and water level change in the same phase and amplitude with tide. During the whole ebb and flow, flow direction does not change as the water level goes under the influence of acceleration and deceleration. As the tide cycle increases, the incipient velocity of sediment goes higher. This means that the long period tide cycle plays buffer effect on the resuspension of sediment, which makes the sediment not so easy both to start up and to suspend. [ABSTRACT FROM AUTHOR]

Salinity changes resulting from storm surge, tides, precipitation, and stormwater run-off are common in coastal wetlands. Soil microbial communities respond quickly to salinity changes, altering the rate of soil organic carbon (SOC) loss and associated biogeochemical processes. This study quantified the impact of salinity-altering pulses on SOC loss, defined as microbial respiration (CO flux) at high and low tide, CH flux, and dissolved OC (DOC) release, in 3 intertidal wetlands (Jacksonville, FL, USA). Intact soil cores from a freshwater tidal, brackish, and salt marsh were exposed to simulated tides and 3 salinity pulsing events during a 53-day laboratory experiment. Soil and water physio-chemical properties, nutrient release, and microbial indicators were measured. Microbial respiration was the dominate pathway of SOC loss (>97 %). Soil hydraulic conductivity was greater in brackish and salt marshes and was critical to overall soil respiration. High tide CO flux was greatest in the freshwater marsh (58 % of SOC loss) and positively correlated with DOC concentration; low tide CO flux was greatest in brackish and salt marshes (62 and 70 % of SOC loss, respectively) and correlated with NH and microbial biomass. The freshwater marsh was sensitive to brackish pulses, causing a 112 % increase in respiration, presumably from accelerated sulfate reduction and N-cycling. SOC loss increased in the salt marsh pulsed with freshwater, suggesting freshwater run-off may reduce a salt marsh's ability to keep-pace with sea level rise. Increased inundation from storm surges could accelerate SOC loss in freshwater marshes, while decreasing SOC loss in brackish and salt marshes. [ABSTRACT FROM AUTHOR]

In this study, we evaluate the nature of the relationship between particulate matter and total mercury concentrations. For this purpose, we estimate both of the two values in water column over 12-h tidal cycles of the Jade Bay, southern North Sea. Total particulate mercury in 250 mL water samples was determined by oxygen combustion-gold amalgamation. Mercury contents varied from 63 to 259 ng/g suspended particulate matter (SPM) or 3.5-52.8 ng/L in surface waters. Total particulate mercury content (THg) was positively correlated with (SPM), indicating that mercury in tidal waters is mostly associated with (SPM), and that tidal variations of total particulate mercury are mainly due to changes in (SPM) content throughout the tidal cycle. Maximum values for THg were observed during mid-flood and mid-ebb, while the lowest values were determined at low tide and high tide. These data suggest that there are no mercury point sources in the Jade Bay. Moreover, the THg content at low tide and high tide were significantly lower than the values recorded in the bottom sediment of the sampling site (>200 ng/g DW), while THg content during the mid-flood and mid-ebb were comparable to the THg content in the surface bottom sediments. Therefore, changes in THg content in the water column due to tidal forcing may have resulted from re-suspension of underlying surface sediments with relatively high mercury content. [ABSTRACT FROM AUTHOR]

Tidally induced resuspension processes play an important role in the release of mercury (Hg) into the water column, which increases the risk of Hg exposure to estuarine eco-systems. In order to further understand the geochemical activities of Hg in the intertidal area, the temporal variations of dissolved Hg (Hg) and particulate Hg (Hg) in the water column during the course of a tidal cycle and its geochemical processes were studied in the southern intertidal zone of the Yangtze Estuary, China. The concentrations of Hg and Hg varied between 37-612 ng/L and 51-638 ng/L respectively during the tidal cycle. The increase of Hg was distinguished at the early flood tide and late ebb tide when the water flow rates were higher. The Hg concentrations were negatively correlated with Hg ( r = −0.523, p < 0.05) and positively correlated with dissolved organic carbon (DOC) ( r = 0.605, p < 0.05) in the bottom water, indicating that the Hg released from the sediments into the overlying water was associated with the simultaneously released colloidal material in the bottom water. The main pathways for the translocation of Hg from the sediments to the overlying water include the processes of desorption from resuspended particles, advection or diffusion from sediments, and the oxidation of resuspended sulfide. The results of principal components analysis (PCA) and Pearson correlation analysis showed that the combined effects of the total suspended substrate (TSS), DOC, pH and dissolved oxygen (DO) influenced the geochemical activities of Hg in the water column during the course of a tidal cycle. [ABSTRACT FROM AUTHOR]

The Comet assay is finding increasing application as a biomarker assay for the genotoxic potential of contaminants in field transplantation experiments involving mussels. Especially in estuaries, habitats that are of particular concern, environmental variables, such as salinity, can vary significantly. Although hinted at in the literature, there is a lack of clarification as to whether changes in salinity or emersion-induced hypoxia have the potential to alter background DNA damage in mussels, thus masking the extent of potential genotoxic effects following exposure to environmental contaminants. The present study exposed Mytilus edulis in the laboratory to static salinities (25, 50, 75, and 100 %) for 72 h. Mussels were also subjected to simulated tidal cycles, including periods of emersion, for 72 h. None of these treatments resulted in a significant change in the level of DNA damage expressed as % tail DNA. These experiments demonstrate that salinity, within the limits of the concentrations tested, and temporary emersion are not confounding factors for Comet assay data derived from M. edulis. [ABSTRACT FROM AUTHOR]

Animals living on upper intertidal mudflats experience habitat desiccation during neap tides when water does not flood the habitat. Individuals of the manicure crab Cleistostoma dilatatum construct cone-shaped towers at the entrance of their burrows, in which they remain during neap tides. These towers are the tallest known structures compared to body size built by crabs living on intertidal flats. The frequency of tower construction followed semilunar tidal cycles with most building done prior to neap tides when few crabs were active on the mudflat surface. Bigger crabs tended to make taller and wider towers with a wider pinhole on the top. These towers may regulate the microclimate in burrows. [ABSTRACT FROM AUTHOR]

The spatial and diurnal tidal variability of dissolved organic carbon (DOC) concentrations and the composition of dissolved organic matter (DOM), as evaluated by high-temperature catalytic oxidation and excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC), respectively, were determined in Liverpool Bay. EEM-PARAFAC modeling resulted in six fluorescent components characterized as terrestrial humic-like (two), microbial humic-like (two), and protein-like (two). The spatial distributions of DOC and the four humic-like components were negatively correlated with salinity in the high-salinity waters observed in this study (30.41-33.75), suggesting that terrestrial DOM was conservatively distributed. The spatial patterns of protein-like components were largely different from those of DOC, humic-like components, and chlorophyll a, suggesting that these distributions were the combined result of production and degradation in the bay in addition to river inputs. These findings suggest that the DOM dynamics in Liverpool Bay are strongly controlled by river-dominated allochthonous DOM inputs with some less significant contributions of autochthonous DOM within the bay. In addition, the temporal variations of DOM associated with the diurnal tidal cycles were determined at one inshore (31.34-32.24 salinity) and one offshore (33.64-33.75 salinity) station in the bay. Negative linear relationships between salinity and DOM characteristics, i.e., DOC, humic-like, and protein-like components, were observed at the inshore station. In contrast, no relationship was observed at the offshore station, suggesting that the export of DOM through rivers and possibly tidal flats have a noticeable influence on DOM concentration and composition up to a relatively elevated salinity of around 33 in Liverpool Bay. [ABSTRACT FROM AUTHOR]

Transepithelial potentials (TEP) were measured in killifish, acclimated to freshwater (FW), seawater (SW), 33% SW or cycling salinities relevant to tidal cycles in an estuary, and subsequently subjected to salinity changes in progressive or random order. Random compared to progressive salinity changes in an upward or downward direction in FW- and SW-acclimated fish, respectively, did not greatly influence responses to salinity change. Fish acclimated to SW or 33% SW as well as those acclimated to cycling salinities behaved similarly (TEP more positive than +15 mV in 100% SW, decreasing to ~0 mV at 20–40% SW, and more negative than −30 mV in FW). In contrast, FW-acclimated fish displayed a less pronounced TEP response to salinity (0 mV in FW through 20% SW, increasing thereafter to values more positive than +10 mV at 100% SW). We conclude that when evaluated under estuarine tidal conditions, the killifish gill exhibits adaptive electrical characteristics, opposing Na+ loss at low salinity and favouring Na+ extrusion at high salinity, changes explained at least in part by the Cl− to Na+ permeability ratio. Thus animals living in the estuaries can move to lower and higher salinities for short periods with little physiological disturbance, but this ability is lost after acclimation to FW. [ABSTRACT FROM AUTHOR]

The monthly distribution of zooplankton communities in Han River estuary was investigated at two stations from July 1998 to June 1999. Monthly mean abundance of total zooplankton varied remarkably, with the range from 20 indiv.·m-3 to 19,600 indiv.·m-3. During the study period, dominant species of zooplankton community were dinoflagellate Noctiluca scintillans, copepods Paracalanus indicus, Paracaanus crassirostris, Acartia hongi, Acartia ohtsukai, and meroplanton cirriped larvae. According to tidal states, relative high abundance occurred at high tide without regard to season. The temporal distribution of abundance implied that the reduced salinity probably limited the zooplankton populations and the fluctuations of salinity were an important factor in the variation of abundance. However, the results of salinity tolerance test shows that the variations in salinity do not directly influence the decrease of abundance. This study shows that the relatively high abundance of zooplankton near high tide seems to be related with the expansion of abundant zooplankton inhabiting Incheon coastal waters through tidal currents. [ABSTRACT FROM AUTHOR]

Particulate trace metal (Cu, Cr, Ni, Pb and Zn) and major element (Fe, Mn and Al) concentrations have been determined following intensive sampling over two consecutive spring tidal cycles in the 'turbidity maximum zone' (TMZ) of the Port Jackson estuary, Australia. Salinity, temperature, pH, dissolved oxygen, suspended particulate matter (SPM) and chlorophyll a were also determined. A three-factor analysis of variance was used to test temporal variability in concentrations of particulate trace metals and major elements as a result of tidal oscillation. Estuarine master variables, such as temperature and pH, varied within a narrow range; nevertheless, the tidal signal was clear for surface and bottom waters. In surface water, no variance was detected in SPM concentrations between consecutive tidal cycles or between tidal stages (i.e. flood, ebb and slack water). In bottom water, however, SPM concentrations were significantly higher (P≤0.05) at flood tide than at slack high water and ebb tide. Concentrations of particulate trace metals and major elements in surface water do not display significant variability between tidal cycles or stages. Nevertheless, differences within each tidal stage were significant (P≤0.05) for all elements. In bottom water, only particulate Fe and Al exhibited significant differences (P≤0.05) between tidal cycles, whereas particulate Ni was the only trace element that presented significant differences (P≤0.05) between tidal stages, following the distribution of SPM, with highest concentrations at flood tide. Among the metals studied, significant variation was found at all three temporal scales examined (i.e. from hours to consecutive tidal cycles), although the patterns of variation were different for each metal. The semi-diurnal fluctuation of SPM and particulate trace metal concentrations during spring tides is interpreted as a resuspension–deposition cycle caused by cyclical oscillations of bottom currents. The results are discussed in the context of the implications of tidal cycle influence on the geochemistry and cycling of particulate trace metals in the Port Jackson estuary. [ABSTRACT FROM AUTHOR]

Many marine organisms have a specific reproductive timing, but its adaptive nature has not been directly tested because of the difficulty of manipulating reproductive timing in the field. Egg survival in relation to the timing of egg release in the puffer Takifugu niphobles, an intertidal spawner, was assessed by experimentally transplanting eggs to several tidal zones, and the observed pattern of variation in spawning time across environments (a pebble vs. a sandy beach) was examined to see if it was consistent with the presumed selection regime. The vertical distribution of eggs and the observation of spawning zones showed that substrate characteristics affected the fate of released eggs: at the pebble beach eggs were stranded in the high intertidal zone, while they were washed out toward the lower zone at the sandy beach. The egg-transplant experiment showed that egg survival was lower in the high zone than in the middle and low zones at both the pebble and sandy beaches, indicating that individual fishes should spawn earlier relative to the tidal cycle. However, the selection pressure for thefish to spawn earlier was more intense at the pebble beach than at the sandy beach, which was attributed to the difference between the beaches in the degree to which eggs were transported seaward. At the pebble beach (1) the timing of spawning was more strictly synchronized with the tidal cycle, (2) a day's spawning started, peaked, and ended earlier relative to the tidal cycle, and (3) a day's spawning was concentrated in a shorter time, than at the sandy beach. These temporal patterns of spawning are allexpected from the presumed selection regime across the beaches, suggesting that there is an evolutionary response of the trait to this selective force. This study explains interpopulation variation in reproductive timing of a marine fish by combining experimental manipulations of the reproductive timing with classic comparative methods. This experimental approach performed in different ecological settings is essential to further understanding of the ecology and evolution of temporal patterns of reproduction. [ABSTRACT FROM AUTHOR]

Riverine organic carbon export plays a major role in the global carbon cycle. The biodegradability of riverine dissolved organic carbon (DOC) determines both greenhouse gas emissions and the amount of refractory DOC. However, seasonal changes in organic carbon and factors controlling DOC biodegradation are still not well understood in large rivers. Here, we examined the monthly changes in concentrations of particulate organic carbon (POC) and DOC in a large subtropical river (Changjiang River, Nantong Section, China) in 2017. We also measured biodegradable DOC (BDOC), specific UV absorbance (SUVA254), neutral sugar concentrations and their compositions. The results showed that POC had no significant relationship with water temperature, precipitation, and discharge. DOC concentrations were significantly negatively correlated with all these parameters, and water temperature explained 61% of the variance in DOC. BDOC concentrations varied between 0 and 14.01 ± 1.22 mg C/L and were closely associated with DOC (R2 = 0.85, p < 0.001). The negative correlation between BDOC% and SUVA254 (R2 = 0.63, p < 0.01) suggested that high aromaticity was associated with low bioavailability. Water temperature was positively correlated with total neutral sugar yield (R2 = 0.43, p < 0.001), which was mainly composed of glucose and deoxysugars in the warm season; thus, neutral sugar composition is a useful indicator of DOC decomposition. Taken together, our study showed that POC has no clear seasonal change, while DOC exhibits a strong seasonal change, and high water temperature leads to low BDOC in a large subtropical river. [ABSTRACT FROM AUTHOR]

Tropical intertidal sediments often contain porewater of relatively high salinity, especially in areas exposed to longer periods without seawater inundation and high evaporation. Such an area exists on the west coast of Zanzibar: a high intertidal mangrove plateau, flooded only during spring high tides, with sediment porewater salinities commonly exceeding 100 ppt. A field survey was conducted in this area to examine variations in population density of major meiofaunal taxa andthe assemblage structure of free-living marine nematodes during spring-neap tidal cycles. Samples were taken on seven occasions for two months, starting from the end of the rainy season. Porewater salinity remained high throughout the sampling period, ranging from 89 to 160 ppt. Neither spring tide inundation nor heavy rains lowered the salinity markedly. The meiofauna consisted only of four taxa, present on all sampling occasions: nematodes, harpacticoid copepods, plathyhelminthes and chironomids. Densities in surface sediments (0-5 cm) were low compared to other mangrove areas, ranging from 271 to 656 animals 10 cm-2 with nematodes dominant on all sampling occasions (58-87%). Density fluctuations could not be explained by the effects of spring tide inundation, but the meiofauna showed significant correlations with grain size and organic material. Despite the wide range of salinity, only the numbers of chironomids were negatively correlated with increased salinity. Nematode species diversity was low in all samples, although altogether 28 species were recorded in the samples.Four species occurred in more than 50% of the samples ( Microlaimus sp. (100%), Metalinhomoeus sp. (76%), Daptonema sp.l (56%), Chromadorina sp. (56%)) while 12 species were found only in one or two samples. Multidimensional scaling ordination (MDS) of the nematode species abundance data indicated little effects of spring tide inundation on the assemblage structure, but rather a successive change from wet to dry [ABSTRACT FROM AUTHOR]