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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]

This study investigates the effects of tidal cycles on the zooplankton community within the Cotonou Channel, an important waterway connecting the large Nokoué Lagoon to the Atlantic Ocean in Benin. From the determination of zooplankton composition from 25-hour samples collected in July 2020, alpha diversity indices and abundance were assessed, while relationships between biotic and abiotic parameters were analyzed through Pearson correlation, analysis of variance, and principal component analysis. A total of 66 zooplankton taxa were identified, with rotifers exhibiting the highest species richness (35 taxa), while copepods dominated in abundance (71%). Zooplankton abundance varied significantly, ranging from 2 to 95 ind L−1 depending on the tidal phase. A negative correlation was found between species richness (r = −0.51, p < 0.01) and increasing salinity (3–37), indicating that higher salinity reduced diversity (r = 0.06, p > 0.05). Resilient species like Synchaeta bicornis persisted despite salinity changes. The tidal cycle structurally altered the zooplankton community, with abundance and diversity peaking at different phases, notably higher at high tide (15 ind L−1.) These initial findings underscore the complex interactions between tidal dynamics and estuarine biodiversity, suggesting the need for further research across different tidal and seasonal conditions to inform effective management and conservation efforts. [ABSTRACT FROM AUTHOR]

We investigated the reproduction of the barnacle Tetraclita kuroshioensis Chan, Tsang & Chu, 2007 (Cirripedia: Thoracica: Tetraclitidae) at different heights in the intertidal zone in Okinawa, Japan with a focus on gonadal development, the brooding of eggs, and unhatched larvae, as well as the role of environmental factors in breeding rhythmicity. Histological observations collected around each full moon from September 2019 to October 2020 showed various stages of oocyte development in September and October 2019 and from March to September 2020, whereas mature testes were observed from April to October 2020. The breeding season of this species thus lasts for at least seven months under long-day conditions at a water temperature above 21 °C. Barnacles collected from three tidal levels on multiple occasions during April, August, and October 2020 displayed little vertical variation in their stage of ovarian development, but there was a noticeable difference in the percentage of brooding individuals in August and October, as well as an increased prevalence of brooding during the new-moon phase at the upper and middle tidal heights. Our findings indicate that larval release by T. kuroshioensis undergoes seasonal variation, apparently influenced by the cycles of lunar (major factor) and tide (minor factor) in their habitat. [ABSTRACT FROM AUTHOR]

Morphological changes in estuaries are typically discussed on decadal time scales, with reported changes often exceed several decimeters. In our study, we utilized refined in-situ data to investigate bed-level changes and rapid accretion-erosion transitions during tidal cycles off the Changjiang Estuary. A field study employing a high-resolution bottom tripod system was conducted, measuring various parameters such as water level, waves, velocity profiles, nearbottom suspended sediment concentration (SSC), and bed level changes over ten tidal cycles. Our findings reveal significant and intense bed level changes occurring at the scale of tidal cycles. The data suggests that downward sediment transport plays a dominant role in the overall accretion tendency throughout the study period. Additionally, our research introduces a dynamic critical bed shear stress that increases during tidal cycles, deviating from fixed values. We also present a new quadrant analysis method to elucidate the primary processes controlling near-bed sediment transport. The results highlight the importance of horizontal advective sediment transport in frequent accretion-erosion transitions at tidal-cycle timescales. This implies a frequent exchange of sediment between adjacent shoals and channels in the seaward region of the North Channel in the Changjiang Estuary, which holds significance for future navigation and construction management. [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]

This study investigates the effects of tidal cycles on the zooplankton community within the Cotonou Channel, an important waterway connecting the large Nokoué Lagoon to the Atlantic Ocean in Benin. From the determination of zooplankton composition from 25-hour samples collected in July 2020, alpha diversity indices and abundance were assessed, while relationships between biotic and abiotic parameters were analyzed through Pearson correlation, analysis of variance, and principal component analysis. A total of 66 zooplankton taxa were identified, with rotifers exhibiting the highest species richness (35 taxa), while copepods dominated in abundance (71%). Zooplankton abundance varied significantly, ranging from 2 to 95 ind L−1 depending on the tidal phase. A negative correlation was found between species richness (r = −0.51, p < 0.01) and increasing salinity (3–37), indicating that higher salinity reduced diversity (r = 0.06, p > 0.05). Resilient species like Synchaeta bicornis persisted despite salinity changes. The tidal cycle structurally altered the zooplankton community, with abundance and diversity peaking at different phases, notably higher at high tide (15 ind L−1.) These initial findings underscore the complex interactions between tidal dynamics and estuarine biodiversity, suggesting the need for further research across different tidal and seasonal conditions to inform effective management and conservation efforts.

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]

Trees in wetlands emit a significant amount of methane (CH4) into the atmosphere which is produced in the soil where anaerobic conditions prevail. However, only very few studies have considered the role of trees in the CH4 budget of mangrove forests. How tree CH4 emissions (FCH4$$ {F}_{{\mathrm{CH}}_4} $$) vary between and within individuals, and how these emissions vary with the day/night alternation and the tidal cycle, have not yet been elucidated. We measured FCH4$$ {F}_{{\mathrm{CH}}_4} $$ from buttress roots and stems on individuals of Bruguiera gymnorrhiza of different sizes. We also measured FCH4$$ {F}_{{\mathrm{CH}}_4} $$ from trees and sediments over a 24‐h cycle. Higher FCH4$$ {F}_{{\mathrm{CH}}_4} $$ was measured on the buttress roots than on the stems, with a decreasing trend with height along the stems on a majority of trees. FCH4$$ {F}_{{\mathrm{CH}}_4} $$ exhibited large variations over a 24‐h cycle which were observed for the first time in this study. FCH4$$ {F}_{{\mathrm{CH}}_4} $$ from sediment was twice higher at low tide compared to just before or after the flood period. FCH4$$ {F}_{{\mathrm{CH}}_4} $$ from non‐submerged stem positions at high tide was four times higher during the day than during the night. On buttress roots and on stem portion which were submerged, high FCH4$$ {F}_{{\mathrm{CH}}_4} $$ were measured at the beginning of the ebb tide even at night. A better understanding of FCH4$$ {F}_{{\mathrm{CH}}_4} $$ variability from mangrove trees and its controls, at different time scales and along spatial gradients is needed for accurate estimation of CH4 budgets of mangrove forests. [ABSTRACT FROM AUTHOR]

The brown alga Pelvetia canaliculata is one of the species successfully adapted to intertidal conditions. Inhabiting the high intertidal zone, Pelvetia spends most of its life exposed to air, where it is subjected to desiccation, light, and temperature stresses. However, the physiological and biochemical mechanisms allowing this alga to tolerate such extreme conditions are still largely unknown. The objective of our study is to compare the biochemical composition of Pelvetia during the different phases of the tidal cycle. To our knowledge, this study is the first attempt to draft a detailed biochemical network underneath the complex physiological processes, conferring the successful survival of this organism in the harsh conditions of the high intertidal zone of the polar seas. We considered the tide-induced changes in relative water content, stress markers, titratable acidity, pigment, and phlorotannin content, as well as the low molecular weight metabolite profiles (GC-MS-based approach) in Pelvetia thalli. Thallus desiccation was not accompanied by considerable increase in reactive oxygen species content. Metabolic adjustment of P. canaliculata to emersion included accumulation of soluble carbohydrates, various phenolic compounds, including intracellular phlorotannins, and fatty acids. Changes in titratable acidity accompanied by the oscillations of citric acid content imply that some processes related to the crassulacean acid metabolism (CAM) may be involved in Pelvetia adaptation to the tidal cycle. [ABSTRACT FROM AUTHOR]

Dissolved inorganic carbon (DIC) and particulate organic carbon (POC) dynamics in the world's estuaries have been studied extensively at monthly, seasonal, and annual time scales with particular focus on their concentrations and export fluxes to the coastal oceans. However, given the dynamic nature of the estuaries, the effect of tidal and diel cycles on the processes modulating DIC and POC dynamics remains obscure. To decipher the biogeochemical processes at tidal scale, DIC and POC concentrations and their carbon and nitrogen isotopic compositions were measured across the salinity gradient at every high and low tide for nine consecutive days (14–23 October 2019) in the Mahanadi estuary, a tropical estuary at the east coast of India. Showing contrasting differences across salinity gradient in DIC, POC and their isotopic compositions, DIC and POC were significantly different during high and low tide in the mixing zone only during spring duration. This showed the effect of spring-neap tidal cycle owing to water level fluctuations and mixing intensity in the estuarine mixing zone. Linear least-squares regression models indicated carbonate and/or silicate weathering by biogenic CO 2 to be the probable DIC source in the freshwater region of the estuary. Deviations of observed DIC concentrations and δ13C DIC from the conservative mixing values suggested pronounced alteration of DIC source signature in the mixing zone. A process-based model approach aimed at delineating possible biogeochemical processes affecting DIC dynamics indicated calcite dissolution during low tide and calcite precipitation during high tide to be dominant processes in the mixing zone. Additionally, signatures of more than one simultaneous biogeochemical process modulating the DIC dynamics were also observed. POC pool in the mixing zone was largely influenced by its removal through rapid remineralization during both high and low tides. Graphical plots also showed that POC in the mixing zone and at the saline location was significantly affected by processes such as degradation, whereas it was only slightly affected in the freshwater region of the estuary. δ13C POC , along with the C/N ratio of POM, indicated that C3 plants and/or their derived soil were the major source of POM in the freshwater, whereas the higher contribution of riverine POM and marine phytoplankton was observed in the mixing zone and saline location, respectively. • High resolution tidal measurements of DIC and POC in a tropical estuary • Carbonate and/or silicate weathering through biogenic CO 2 was major source of DIC. • Nonconservative mixing and various biogeochemical processes affected DIC and POC pools. • Calcite dissolution and precipitation during low and high tide, respectively • Degradation was major process affecting POC in the mixing zone. [ABSTRACT FROM AUTHOR]

Reversals in wave-generated longshore currents in surf zones occur at different temporal and spatial scales. Along coastlines with tidal channel openings with well-developed mouth bars or ebb-tidal deltas, the reversal mechanism is often attributed to the mouth bar – induced refraction of the shoaling waves. This reversal mechanism is characterized by convergence of longshore currents from the adjoining surf zones at the mouth of the tidal channel. Simultaneous half-hourly monitoring of wave-generated longshore currents over 50 successive (daylight) semi-diurnal tidal cycles in beach surf zones adjoining the Qua Iboe River estuary, S.E coast of Nigeria showed the above reversal pattern during flooding stage only. The converse pattern, where the surf zone longshore currents diverged away from the mouth of the estuary, was observed during ebbing stage. Both surf zones showed flow direction inversion with respect to each other, with velocity vector correlation coefficient r > − 0.8 in over 80 % of the data set. Instances of comparable flow direction (<10 %) were also recorded. Tidal processes are implicated in the documented results. Direction-averaged longshore current velocities, typically in the 15–60 cm/s range, attained highest values in both surf zones at about spring tide phase. Also, tidal cycle-residual longshore current maximum and minimum velocities occurred close to spring and neap tide, respectively. Only 30 % of the residual velocities were eastward directed in the up-drift surf zone as against 80 % in the down-drift counterpart. Given the prevailing southwesterly waves, the present results negate the assertion that reversal in longshore current direction in this offset shoreline setting is exclusively a consequence of wave refraction by mouth bar morphology. The reversing pattern of the longshore currents over a tidal cycle is well explained by incorporating interacting effects of shoaling waves with tide-induced oscillations in water level as well as the estuarine flow. • Wave-generated longshore current direction reversal occurred at tidal frequencies • Wave refraction by estuarine mouth bar as sole mechanism for flow reversal was unlikely • Impact of tidal processes on flow pattern differed with tidal stage and lunar phase • Pressure gradient can drive flow in direction opposite to breaker angle dictated. [ABSTRACT FROM AUTHOR]

Numerous studies have evaluated the acoustic characteristics of soniferous snapping shrimp, but a few are based on long-term mooring measurements. In this study, underwater ambient noise signals were collected from a hydrophone moored 10 m from the sea bed in the coastal sea of western Jeju, South Korea, from mid-September 2019 for 90 days to analyze the variation in the sound of snapping shrimp. The kernel signal and a threshold value were utilized to identify the snapping shrimp, and the snap rate per minute was computed for quantitative analysis. The results show that the mean and standard deviation of the snap rate in the western sea of Jeju was 2132 ± 432 per minute during the whole measurement period. The surface water temperature and tidal level decreased by 7 °C from 25 °C and 50 cm from 190 cm, respectively, over 90 days. The snap rate decreased from September mainly due to the decrease in water temperature by 71 times per minute for every 1 °C decrease. It showed a circadian cycle, increasing by 17~24% at sunrise and sunset compared to the daytime minimum. The snap rate at night was the highest in late summer but the rate dropped like the one during the day in late fall. The snap rate at high tide was 13% higher on average than at low tide. The circadian and tidal changes of the snapping shrimp sound from long-term mooring measurements may be used as primary data for underwater ambient noise and the ecological behavior of snapping shrimp. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) contamination was investigated along a freshwater-seawater continuum from Chumphon River to the Gulf of Thailand. The vertical distribution in the water column and contamination in green mussels were also studied. MPs were detected in all water samples and sediment samples. Furthermore, MPs were detected in 75% of the green mussels. A higher abundance of MPs was observed in the river system than in the coastal region, indicating that river runoff associated with inland human activities is the major sources of MPs in the coastal regions and cultured green mussels. In the water column, a polymer gradient varying with depth existed where low-density particles decreased from surface to subsurface and sediment while high-density particles exhibited the opposite pattern. Polymers in surface and subsurface water were predominantly composed of low-density polyethylene, polypropylene, and polystyrene particles. However, sediment samples were equally dominated by those mentioned low-density polymers and high-density polyethylene terephthalate, polyamide, rayon, and cotton particles. Furthermore, fibers were the most common shape found in water, sediment, and mussel samples representing 95% of all particles in river water samples and were evenly distributed throughout the water column regardless of density. However, only shorter fiber (mostly <1 mm) was detected in green mussel samples similar to their living environment. Blue, black and white particles dominated all samples. During the tidal cycle, half of the MPs entering the Gulf of Thailand returned to the river during high tide. This backflow predominantly comprised small fibers and low-density polymer MPs. The average daily load of MPs from Chumphon River to the Gulf of Thailand was 3.33 × 102 million items/day. [Display omitted] • The density of MPs impacts their vertical distribution. • Small MPs (<1 mm) increased in the estuary during the rising tide. • Mussels preferentially ingested smaller MPs over larger MPs. • Polyethylene and polypropylene were the predominant polymers identified. • Daily flux of MPs from Chomphon River to the Gulf of Thailand was 3.33 × 102 million items/day. [ABSTRACT FROM AUTHOR]

Nearly all of our understanding of rocky inter-tidal ecology comes from studies conducted at low tide. To study inter-tidal organisms at high tide, we anchored waterproof digital GoPro® video cameras in wave-exposed tidepools and recorded the daytime movements of the black turban snail, Tegula funebralis, over the tidal cycle between May and August 2012 near Bodega Bay, California. Overall, snails moved more quickly and presumably foraged more during low tides and on days with warmer air and perhaps water temperatures. This is similar to other ectotherms that exhibit increased metabolic rates, movement and foraging in warmer conditions. Snails also moved less during flood and high tides, may have moved downward in tidepools at flood tides, and showed evidence of reduced activity on days with larger waves. This inactivity and refuge seeking may have been a strategy to avoid dislodgment by waves. Analysis of snail trajectories showed foraging bouts indicated by alternating zig-zagging and straight movement. There was no effect of temperature, wave height, or tidal phase on distribution of snail turning angles, suggesting that they may have foraged consistently but moved faster during warm conditions and low tides, thereby grazing a larger area. This is one of few direct recordings of inter-tidal organisms on wave-exposed rocky shores during high tide. The methods used here are easily transferable to other studies, which are needed to increase our understanding of behaviors that structure rocky shore communities during high tide.

River estuaries are specific transition zones that connect coastal and terrestrial environments and are recognized as primary conveyors for land-derived plastics to open oceans. The present study is the first to investigate tidal effects on microplastics (MPs) in the Chao Phraya River estuary. MPs (16–5000 μm) were collected from the water column during the changes in tidal current in order to analyze abundance, characteristics, and ecological risk. The abundance of MPs varied from 1.37 to 4.51 pieces/L and an average of 4.0 ± 3.8 pieces/L were found during the tidal cycle, which implied moderate to relatively high contamination when compared to other estuaries. Moreover, the average abundance of MPs during the low tide period was comparatively higher than that in other tidal phenomena. Morphological characteristics revealed that shape of fragments, shade of blue, size of 16–100 μm and PTFE is dominant in the MPs. The pollution load index (P L I C P R E) was 5.98, which denoted that the Chao Phraya River estuary is polluted with MPs at a low contamination level. In contrast, the risk index (R I C P R E) of MPs in the water column during the tidal cycle was 318.8, which indicated that the estuarine ecosystem of the Chao Phraya River is under considerable risk. In the present study, an ecological risk assessment was conducted for the Chao Phraya River estuary, which provides basic reference data for the management of pollution control related to MPs in the Chao Phraya River basin. • Influence of tidal effects was arranged as low tide ≥ flood tide = ebb tide ≥ high tide. • Shape of fragments, shade of blue, size of 16–100 μm and polytetrafluoroethylene (PTFE) is dominant in the microplastics. • The Chao Phraya River estuary is under considerable risk. • Low contamination and percentage of polyurethane (PUR) are the key factors of ecological risk. [ABSTRACT FROM AUTHOR]

Millions of migrating and wintering waders depend on coastal areas and estuaries for feeding and to replenish body reserves. These habitats are dynamic, with changing intertidal flats and sediments due to natural and climate-driven processes. The aims of this study were to examine whether physical conditions of intertidal flats such as geomorphology and sediment compositions could explain abundance of wader species, and furthermore whether changes in these conditions over time influenced changes in abundance of waders. In addition to physical structures such as datum (level), slope and sediment composition of intertidal flats, dynamic variables connected to tidal cycles such as distance of the waterline from the coast and duration of water cover were included. Penetration of the sea floor was measured as a proxy for sediment composition. The study was conducted in the Danish section of the Wadden Sea during 1981–1986 and 2008–2009 with additional data from 2020. The focus was on 12 widespread wader species. PCA analysis revealed that wader species were distributed in relation to tidal cycles such as duration of water cover and the position of waterline and to the physical structures, datum, slope and penetration, in decreasing order. With regard to the physical structures, pairwise comparisons of distribution of waders species showed that mean datum (level) was significantly different for 51 pairs of species out of 66 comparisons, mean penetration values differed for 34 pairs, and mean slope differed for 26 pairs of wader species. Long-term changes of physical structures of transects revealed that changes of densities of 10 wader species were significantly correlated with changes per year in one or more of the physical structures: seven wader species were significantly correlated with changes per year of mean datum (level) of transects (Lapwing was positively correlated while Avocet, Golden Plover, Grey Plover, Dunlin, Bar-tailed Godwit and Redshank were negatively correlated), five species with mean slope (Oystercatcher, Ringed Plover and Knut were positively correlated and Grey Plover and Redshank were negatively correlated), and three species with mean penetration values (sediment composition) of transects (Avocet and Bar-tailed Godwit were positively correlated and Lapwing was negatively correlated). The study shows that long-term changes of physical structures of intertidal flats affected abundance of wader species. The results are important for interpretation effects of erosion and accretion of coastal areas as consequences of natural and climate driven processes such as sea level rise and coastal squeeze. • Wader species distribute in relation to dynamic and physical features in estuaries. • Wader species distribute significantly in relation to level of intertidal flats and sediment. • In decreasing order, level, slope and sediment composition affect distribution of waders. • Long-term changes of physical structures affect densities of waders. [ABSTRACT FROM AUTHOR]

For sessile intertidal organisms, periods of low tide impose both cellular and physiological challenges that can determine bathymetric distribution. To understand how intertidal location influences the cellular response of the bivalve Perumytilus purpuratus during the tidal cycle (immersion-emersion-immersion), specimens from the upper intertidal (UI) and lower intertidal (LI) of bathymetric distribution were sampled every 2 h over a 10-h period during a summer tidal cycle. Parallelly, organisms from the UI and LI were reciprocally transplanted and sampled throughout the same tidal cycle. Levels of oxidative damage (lipid peroxidation and protein carbonyls) as well as total antioxidant capacity and total carotenoids were evaluated as cellular responses to variations in environmental conditions throughout the tidal cycle. The results indicate that both the location in the intertidal zone (UI/LI), the level of aerial exposure, and the interaction of both factors are determinants of oxidative levels and total antioxidant capacity of P. purpuratus. Although oxidative damage levels are triggered during the low tide period (aerial exposure), it is the UI specimens that induce higher levels of lipid peroxidation compared to those from the LI, which is consistent with the elevated levels of total antioxidant capacity. On the other hand, organisms from the LI transplanted to the UI increase the levels of lipid peroxidation but not the levels of protein carbonyls, a situation that is also reflected in higher levels of antioxidant response and total carotenoids than those from the UI transplanted to the LI. The bathymetric distribution of P. purpuratus in the intertidal zone implies differentiated responses between organisms of the lower and upper limits, influenced by their life history. A high phenotypic plasticity allows this mussel to adjust its metabolism to respond to abrupt changes in the surrounding environmental conditions. • Bathymetric location and time of aerial exposure influences REDOX metabolism. • Higher oxidative damage is generated in mussels from the upper intertidal limit. • Transplanted mussels from low to up fringe showed higher oxidative damage. • During emersion carotenoids increased in transplanted mussels from the lower fringe. [ABSTRACT FROM AUTHOR]

This study assessed the effects of tidal stages and habitat conditions on nekton assemblage and distribution in the Kakum River estuarine mangrove system in the Central Region of Ghana. Teleosts and crustaceans were sampled using pole seine and cast net from a tidal mangrove pond and a channel, and characterised using morphometry and ecological guilds concept. In total, 1 146 specimens were collected, with 35 species from 19 families represented. The most abundant species encountered were Liza spp. (Mugilidae; 36%), Sarotherodon melanotheron (Cichlidae; 16%), Elops lacerta (Elopidae; 6%) and Sardinella aurita (Clupeidae; 5%), which exhibited pronounced spatial distribution. Sarotherodon melanotheron showed preference for ponds with minimal water flow and depth, Sardinella aurita occurred only in deeper sections of the mangrove channel with significant flow velocity, and Elops lacerta in the pond and all channel stations. Mugilids were found exclusively in the channel, whereas Palaemonidae (Macrobrachium macrobrachion and M. vollenhoveni) occurred in specific locations in the channel, with species- specific preferences for tidal stages. Most species encountered were identified to be predominantly marine migrants with bentophagous feeding habit. Site selection and tidal stages were found to affect the occurrence and distribution of fishes over a tidal cycle and interactively influence species diversity. [ABSTRACT FROM AUTHOR]

Abstract Background A strong behavioural plasticity is commonly evidenced in the movements of marine megafauna species, and it might be related to an adaptation to local conditions of the habitat. One way to investigate such behavioural plasticity is to satellite track a large number of individuals from contrasting foraging grounds, but despite recent advances in satellite telemetry techniques, such studies are still very limited in sea turtles. Methods From 2010 to 2018, 49 juvenile green turtles were satellite tracked from five contrasting feeding grounds located in the South-West Indian Ocean in order to (1) assess the diel patterns in their movements, (2) investigate the inter-individual and inter-site variability, and (3) explore the drivers of their daily movements using both static (habitat type and bathymetry) and dynamic variables (daily and tidal cycles). Results Despite similarities observed in four feeding grounds (a diel pattern with a decreased distance to shore and smaller home ranges at night), contrasted habitats (e.g. mangrove, reef flat, fore-reef, terrace) associated with different resources (coral, seagrass, algae) were used in each island. Conclusions Juvenile green turtles in the South-West Indian Ocean show different responses to contrasting environmental conditions - both natural (habitat type and tidal cycle) and anthropogenic (urbanised vs. uninhabited island) demonstrating the ability to adapt to modification of habitat.

Short duration events (SDEs) are reported worldwide from ocean-bottom seismometers (OBSs). Due to their high frequency (4–30 Hz) and short duration, they are commonly attributed to aseismic sources, such as fluid migration related processes from cold seeps, biological signals, or noise. We present the results of a passive seismic experiment that deployed an OBS network for 10-month (October 2015–July 2016) at an active seepage site on Vestnesa Ridge, West Svalbard continental margin. We characterize SDEs and their temporal occurrence using the conventional short-time-average over long-time-average approach. Signal periodograms show that SDEs have periodic patterns related to solar and lunar cycles. A monthly correlation between SDE occurrences and modelled tides for the area indicates that tides have a partial control on SDEs recorded over 10 months. The numbers of SDEs increase close to the tidal minima and maxima, although a correlation with tidal highs appears more robust. Large bursts of SDEs are separated by interim quiet cycles. In contrast, the periodicity analysis of tremors shows a different pattern, likely caused by the effect of tidally controlled underwater currents on the instrumentation. We suggest that SDEs at Vestnesa Ridge may be related to the dynamics of the methane seepage system which is characterized by a complex interaction between migration of deep sourced fluids, gas hydrate formation and seafloor gas advection through cracks. Our observation from this investigated area offshore west-Svalbard, is in line with the documentation of SDEs from other continental margins, where micro-seismicity and gas release into the water column are seemingly connected.

Modeling of microplastic (MP) transport in the aquatic environment is complicated by the diverse properties of the plastic particles. Traditional modeling methods such as Lagrangian particle tracking and Eulerian discrete class (DC) methods have limitations as they are not best placed to account for the diverse characteristics of individual particles, namely, size, density, and shape, which are crucial for determining the transport of MPs. In this work, we address the issue of particle size diversity by using the population balance equations (PBE) method. In addition to the advection-diffusion terms, the PBE transport equation involves a deposition sink term. Seven size classes of MPs are modeled in the DC method, which is compared to the PBE method. The evolution of particle size distribution is compared between the two methods using a simplified test case of a schematized estuary with tidal forcing and river discharge. This work successfully demonstrates the applicability and appropriateness of the PBE model in modeling the transport of MPs to track the dynamic and complete size distribution at a reduced computational cost in comparison to the DC model. With the PBE method, it is possible to address other diversities of the MPs such as the shape and density.

Environmental context Methane and nitrous oxide play a significant role in climate change, while the variation in fluxes in mangrove-dominated coastal wetlands is a key uncertainty in the production of these gases. Field studies measuring the fluxes of these gases in a specific coastal mangrove were conducted and revealed complex seasonal behaviors. Methane emissions to the atmosphere were significant, while nitrous oxide emissions were less so, but are likely to increase where nutrient levels increase. Mangroves are carbon sinks that are believed to contribute to carbon neutrality; however, they are also considered to be partly offset by their emissions of methane (CH4) and nitrous oxide (N2O). In this study, dissolved CH4, N2O and other hydrological parameters over the tidal cycle in the Golden Bay mangrove (GBM), Beihai, Guangxi, are investigated during the dry season and wet season. The concentration and flux of dissolved N2O and CH4 in the GBM have distinct seasonal variations under the influence of the tidal cycle, and the concentration and flux in the dry season were higher than those in the wet season, with GBM as a weak source of N2O and a strong source of CH4. The fluxes of N2O and CH4 were 119 ± 370 μmol m-2 yr-1 and 87.2 ± 48.6 mmol m-2 yr-1 respectively during tidal coverage. The emission of CH4 through the water-atmosphere interface offsets 22.5 % of the total carbon sequestration of GBM. Owing to the potential increase in N2O emissions caused by possible exogenous nitrogen input and the transport of dissolved CH4 from mangroves to coastal water, uncertainty remains in assessing the capacity of blue carbon sinks in mangroves. [ABSTRACT FROM AUTHOR]

Recent increased application of optical imaging devices have facilitated efficient capture of plankton abundance and community composition, enabling the study of plankton distribution in situ and at a high spatio-temporal resolution. In this study, we aim to investigate how the abundances and distribution patterns of plankton taxa relate over 24-h periods, covering tidal and diel cycles, in the southern North Sea using data from a WP2 net and a Video Plankton Recorder. In the highly dynamic southern North Sea, we document diel vertical migration patterns in the pelagic zone of both pelagic and hyperbenthic taxa, including Calanoida (Copepoda), Amphipoda, Annelida, and Cumacea. In addition, the densities of plankton taxa showed significant small-scale geographical variation over a 24-h period for which tidal currents played an important role, a source of considerable variation that is typically not accounted for. This study adds to the current understanding of plankton distribution and behaviour, particularly in the context of coastal areas characterised by strong tidal cycles and currents, by using in situ imaging techniques. [Display omitted] • Fine-scale VPR tracking of plankton's diel vertical migration. • Proof of nocturnal migration of hyperbenthic taxa from sea bottom. • Significant plankton density fluctuations within 24 h at a single sample location. • Tidal currents have a substantial impact on plankton distribution and densities. [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]

Numerous studies have evaluated the acoustic characteristics of soniferous snapping shrimp, but a few are based on long-term mooring measurements. In this study, underwater ambient noise signals were collected from a hydrophone moored 10 m from the sea bed in the coastal sea of western Jeju, South Korea, from mid-September 2019 for 90 days to analyze the variation in the sound of snapping shrimp. The kernel signal and a threshold value were utilized to identify the snapping shrimp, and the snap rate per minute was computed for quantitative analysis. The results show that the mean and standard deviation of the snap rate in the western sea of Jeju was 2132 ± 432 per minute during the whole measurement period. The surface water temperature and tidal level decreased by 7 °C from 25 °C and 50 cm from 190 cm, respectively, over 90 days. The snap rate decreased from September mainly due to the decrease in water temperature by 71 times per minute for every 1 °C decrease. It showed a circadian cycle, increasing by 17~24% at sunrise and sunset compared to the daytime minimum. The snap rate at night was the highest in late summer but the rate dropped like the one during the day in late fall. The snap rate at high tide was 13% higher on average than at low tide. The circadian and tidal changes of the snapping shrimp sound from long-term mooring measurements may be used as primary data for underwater ambient noise and the ecological behavior of snapping shrimp.

From 2015 to 2019 we installed high-frequency (HF) sea surface temperature (SST), salinity, fluorescence, dissolved oxygen (DO) and partial pressure of CO2 (pCO2) sensors on a cardinal buoy of opportunity (ASTAN) at a coastal site in the southern Western English Channel (sWEC) highly influenced by tidal cycles. The sensors were calibrated against bimonthly discrete measurements performed at two long-term time series stations near the buoy, thus providing a robust multi-annual HF dataset. The tidal transport of a previously unidentified coastal water mass and an offshore water mass strongly impacted the daily and seasonal variability of pCO2 and pH. The maximum tidal variability associated to spring tides (>7 m) during phytoplankton blooms represented up to 40% of the pCO2 annual signal at ASTAN. At the same time, the daily variability of 0.12 pH units associated to this tidal transport was 6 times larger than the annual acidification trend observed in the area. A frequency/time analysis of the HF signal revealed the presence of a day/night cycle in the tidal signal. The diel biological cycle accounted for 9% of the annual pCO2 amplitude during spring phytoplankton blooms. The duration and intensity of the biologically productive periods, characterized by large inter-annual variability, were the main drivers of pCO2 dynamics. HF monitoring enabled us to accurately constrain, for the first-time, annual estimates of air-sea CO2 exchanges in the nearshore tidally-influenced waters of the sWEC, which were a weak source to the atmosphere at 0.51 mol CO2 m–2 yr–1. This estimate, combined with previous studies, provided a full latitudinal representation of the WEC (from 48°75′ N to 50°25′ N) over multiple years for air-sea CO2 fluxes in contrasted coastal ecosystems. The latitudinal comparison showed a clear gradient from a weak source of CO2 in the tidal mixing region toward sinks of CO2 in the stratified region with a seasonal thermal front separating these hydrographical provinces. In view of the fact that several continental shelf regions have been reported to have switched from sources to sinks of CO2 in the last century, weak CO2 sources in such tidal mixing areas could potentially become sinks of atmospheric CO2 in coming decades.

There is growing evidence that a substantial fraction of the dissolved organic and inorganic carbon (DOC and DIC) and particulate organic carbon (POC) can be exported from mangroves to the ocean. Yet our understanding of C fluxes in mangrove forests is limited to only few regional studies that exclude the world's longest sediment dispersal system connected to the Amazon River. The present study aims at (1) examining tidal fluctuations of DOC, POC, and DIC; their isotopes; and optical properties such as chromophoric dissolved organic matter (CDOM) and (2) estimating their exchange fluxes between the mangroves and adjacent coastal water in the Sinnamary estuary, French Guiana. Time series observation highlighted that physical processes coupled to tides controlled diel dynamics and sources of DOC (e.g., litter leaching and pore water seepage) and POC (microphytobenthos, sediment resuspension, and bioturbation activities). Intense benthic remineralization could account for high water column pCO2 and DIC exchange flux during the low tide. Mangrove‐derived DOC export to inner shelf (8.14 g C m−2 day−1) was exceeding import of POC and DIC from the mud bank and marine sources to the mangroves (1.35 and 0.90 g C m−2 day−1, respectively). Because of specific dynamics of the Amazon mobile muds, local geomorphology, water column stratification, and environmental forcing, Guianese mangroves cannot be seen as simple C exporters to the Atlantic waters. These first data setting on C fluxes for the region should be included along with other studies to improve global mangrove C budget estimate. Key Points: Dissolved and particulate carbon exchange fluxes were estimated in a mangrove dominated estuary, French Guiana coastal systemsMangroves are exporter of DOC and importer of DIC and POC that is contrast to previous simplification of mangrove‐derived C exportDistinctive sources of DOC, POC, and DIC were observed referring to specificity and dynamics of the Guianese coastal systems [ABSTRACT FROM AUTHOR]

Peale's dolphin is one of the most common species of cetaceans in Tierra del Fuego, Argentina. However, limited information exists about the local population. In order to characterize the habitat use by Peale's dolphin, land-based observations were carried out during a summer season. Behavioral patterns were studied in relation to tidal cycles and kelp forest, and the main activities displayed were determined. Foraging and resting were the most frequent behaviors observed. Dolphin's behavior seems to be related to the tidal cycle and to its position relative to the kelp bed. This study provides data that can contribute to management plans of the austral marine ecosystem. [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]

The deposition of MPs in a water column and surface sediment during a mixed spring tidal cycle of the Chao Phraya River estuary was investigated. The settling MPs during flood and ebb tides were collected by deploying traps at 3 m below the surface, while the settled MPs throughout the tidal cycle were collected by deploying traps at 1 m above the bottom. The settling rate of MPs was 2168 pieces/m2/h during highest to low tide, and 639 pieces/m2/h during high to lowest tide. The deposition rate of MPs after the end of the tidal cycle was 3172 pieces/m2/day, while the accumulation rate of MPs in the surface sediment was 1515 pieces/m2/day. The settling MPs tended to decrease inversely to the suspended solids and salinity. The major types of the deposited MPs were polyethylene (36 %) and polyamide (33 %), while that of the surface sediment was epoxy resin (80 %). [Display omitted] • The deposition rate of microplastics collected by sediment traps was 3,172 pieces/m2/day, while the accumulation rate of microplastics in the surface sediment was 1515 pieces/m2/day. • The settling of microplastics is inverse to salinity and suspended solids. • Low-density plastics were the majority of plastics that settled at the sediment trap 1 m above the bottom, but denser plastics highly accumulated in the surface sediment. • The result is evidence of a resuspension of microplastics during a tidal current in a river estuary. [ABSTRACT FROM AUTHOR]

Muddy coasts with burrows are widespread globally and most contain brine in underground aquifers. Salt evaporated on a tidal flat surface is an important source of shallow underground brine (phreatic brine and brine in the top layer). However, the salt accumulation/release process in shallow underground brine during tidal cycles remains unclear. To analyze the abovementioned process, sediment permeability and pore-water parameters are measured, and electrical resistivity tomography and ring electrode resistivity probe monitoring are conducted in a tidal flat on the south bank of Laizhou Bay, China, where underground brine occurs and biological activities are pronounced. The results show that evaporated salt on the surface of tidal flats and offshore high-salinity underground brine are the two salt sources of shallow underground brine in tidal flats. Dense burrows and large tidal ranges can accelerate the rate of salt cycling, and promoting the exchange of surface and deep salt through the top layer. During the flooding tide, shallow underground brine is primarily replenished by evaporated salt on the beach surface. In areas with dense burrows, some evaporated salt on the beach surface can pass through the top layer to recharge the phreatic brine. During the ebbing tide, the salt in layers U and B is released into seawater and phreatic brine, respectively. When seawater recedes from the beach surface, a trace amount of phreatic brine and salt in the top layer is released to the beach surface via an upward flow field. Layers U and B are the main areas of salt accumulation and release. The proportion of salt accumulation/release in layer M is the lowest; however, layer M is the most susceptible to salt accumulation and features the highest pore-water salinity among the top layers. • Four stages of salt accumulation/release processes in shallow underground brine during a tidal cycle were described. • Ninety percent of salt cycling in the top layer occurred in layers U and B; however, layer M was more likely to store high-salinity pore water. • The density of burrows and tidal range affected the salinity cycling rate and spatial distribution of high-salinity plumes. • Spatiotemporal changes in pore-water salinity were measured based on electrical resistivity. [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]

We investigated the reproductive characteristics of a terrestrial hermit crab (Coenobita rugosus H. Milne Edwards, 1837) inhabiting Okinawa-Jima. Monthly changes in the gonadosomatic index and ovarian histology revealed that this species had fully developed oocytes from May to October. Data showing that females with (ovigerous females) and without (non-ovigerous females) embryos on their pleopods appeared simultaneously on the shore from June to September 2014 demonstrates that this species undergoes larval release several times for four months. When non-ovigerous females were reared under a combination of two day lengths and two temperatures, oocyte development was induced in the high-temperature group, suggesting that temperature is a proximate factor in ovarian development. The weekly collection of females during the spawning season revealed that the proportion of fully developed oocytes in an ovary increased toward the time of the new moon and decreased around the first-quarter moon, suggesting that this species is a lunar-spawner with a new-moon preference. Some females releasing larvae around the new or full moon were recaptured at approximately 30 d intervals, suggesting at least two major groups with lunar-synchronized larval release. The ovarian development and larval release of C. rugosus are likely entrained to external factors, which change periodically in their habitats. [ABSTRACT FROM AUTHOR]

Suspended particulate matter (SPM) is a key component of coastal food webs and a key variable of nutrient budgets. Understanding its variability across short time scales in estuaries may help ecologists understand seasonal and diurnal migration of estuarine organisms, and answer how their nutritional requirements are fulfilled. It may also inform biogeochemists regarding the factors that influence import and export of nutrients between terrestrial and coastal ecosystems. This study aimed to link the dynamics of fatty acids, stable isotopes (δ13C and δ15N) and C/N ratios of SPM, revealing organic matter quality, to rapidly varying factors (SPM concentration, salinity and presence of daylight) and comparing this variability to the seasonal variation induced by the alternation of dry and wet seasons in the studied region. Our results revealed that these rapidly varying factors had a strong influence on the bacterial and the phytoplanktonic compartments of SPM. They suggest that tidally resuspended particles are the site of intense heterotrophic activity and that estuarine phytoplankton store lipids during the daytime up to substantially modifying SPM quality. Our study also shows higher freshness of SPM during the wet season. We expect this study to raise the interest of both biologists and biogeochemists to introduce daily variability of SPM in food webs and nutrient budgets modelling. Image 1 • We highlight suspended particulate matter daily variability in a tropical estuary. • Tide-resuspended particles are rich in bacterial fatty acid biomarkers. • Phytoplankton stores lipid during daytime up to substantially modifying SPM quality. • Higher freshness of SPM was measured during the wet season. [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]

Abstract The Mozambique tilapia, Oreochromis mossambicus , is a teleost fish native to estuarine waters that vary in salinity between fresh water (FW) and seawater (SW). The neuroendocrine system plays a key role in salinity acclimation by directing ion uptake and extrusion in osmoregulatory tissues such as gill. While most studies with O. mossambicus have focused on acclimation to steady-state salinities, less is known about the ability of adult fish to acclimate to dynamically-changing salinities. Plasma osmolality, prolactin (PRL) levels, and branchial gene expression of PRL receptors (PRLR1 and PRLR2), Na+/Cl− and Na+/K+/2Cl− co-transporters (NCC and NKCC), Na+/K+-ATPase (NKAα1a and NKAα1b), cystic fibrosis transmembrane conductance regulator (CFTR), and aquaporin 3 (AQP3) were measured in fish reared in FW and SW steady-state salinities, in a tidal regimen (TR) where salinities changed between FW and SW every six hours, and in fish transferred from FW or SW to TR. Regardless of rearing regimen, plasma osmolality was higher in fish in SW than in FW fish, while plasma PRL was lower in fish in SW. Furthermore, branchial gene expression of effectors of ion transport in TR fish showed greater similarity to those in steady-state SW fish than in FW fish. By seven days of transfer from steady-state FW or SW to TR, plasma osmolality, plasma PRL and branchial expression of effectors of ion transport were similar to those of fish reared in TR since larval stages. These findings demonstrate the ability of adult tilapia reared in steady-state salinities to successfully acclimate to dynamically-changing salinities. Moreover, the present findings suggest that early exposure to salinity changes does not significantly improve survivability in future challenge with dynamically-changing salinities. Highlights • Tilapia were reared in steady-state (FW or SW) or tidally-changing salinities (alternating FW and SW every 6 h). • Adult tilapia reared in steady-state salinities are capable of acclimating to a tidalregimen (TR). • Expression of PRLRs and effectors of ion and water transport in adult fish transferred to TR is similar to that of TR-reared fish. [ABSTRACT FROM AUTHOR]

Vitale, A.J.; Genchi, S.A., and Piccolo, M.C., 2019. Assessing the surface radiation balance and associated components in an intertidal wetland. Journal of Coastal Research, 35(1), 158–164. Coconut Creek (Florida), ISSN 0749-0208. Knowledge of the surface radiation balance and associated components in intertidal wetlands is essential to the understanding of the ecosystem. The aim of this study is to assess the behavior of the radiation balance (or net radiation) and its components in a salt marsh environment (Bahía Blanca Estuary, Argentina), taking into consideration two different tidal conditions: nonflooded salt marsh (NFS) and flooded salt marsh (FS). In situ measurements were made during a 1-year period. An adequate measurement system to record meteorological and oceanographic parameters by using a floating structure was implemented. The results showed that the tide led to an increase of 5% in net radiation for a typical summer day (NFS = 3485 W m-2 d-1; FS = 3663 W m-2 d-1), while for a typical winter day, the net radiation under NFS and FS conditions was similar (NFS = -616 W m-2 d-1; FS = -615 W m-2 d-1) but showing differences throughout the day. With the purpose of strengthening the results, a spectral analysis using Fourier and wavelet transforms was performed on the net radiation and tide level time series. [ABSTRACT FROM AUTHOR]