Subtidal Channels Research Articles

Heterolytic tide-dominated sedimentary facies and depositional environment: An Example from the Boka Bil formation, Sitapahar anticline, Bangladesh

The Baraichari Shale Formation, which is equivalent to the Boka Bil Formation, is well exposed within the Neogene sequence of the Sitapahar Anticline in the Chittagong-Tripura Fold Belt, Bengal Basin, Bangladesh. Regardless of its importance in hydrocarbon accumulation, a comprehensive facies analysis is essential to understand and explain the heterogeneity within different depositional architectural elements. The purpose of this work is to delineate the lithofacies characteristics, depositional environment heterogeneities and propose a generic depositional model for the Middle to Late Miocene shallow marine sediments of the formation. The sedimentary facies were investigated at three outcrops along the Kaptai–Chandraghona road cut sections of the Sitapahar anticline. The formation is composed of dark to bluish-gray shale, silty shale, yellowish brown siltstone, and gray to yellowish brown fine-to medium-grained sandstone. Eight distinct sedimentary facies have been identified and were categorized into three facies associations: subtidal or estuarine, mixed flats with tidal creeks, and tidal mud flats. The subtidal facies, predominant in the middle member, consists of fine to medium-grained ripple cross-stratified sandstone-siltstone, herringbone cross-stratified sandstone, and trough cross-stratified sandstone, indicating sub-tidal channel deposition. Mixed flats with tidal creeks exhibit heterolithic facies, suggesting energy level changes in intertidal to sub-tidal zones influenced by tidal currents. Tidal mud flats are predominantly laminated shale/mudstone and lenticular laminated sandstone-siltstone, reflecting deposition during tide transitions in the intertidal zone. Fining upward cycles within the formation indicate progressive progradation or changes in inner tidal flats conditions during regressive periods. These depositional settings serve as analogs for equivalent subsurface reservoirs and contribute to the construction of reservoir models with greater accuracy.

The novel estuarine bioremediation target Gracilaria transtasmanica has high tolerance to light limitation, air-exposure and a broad range of salinities

AbstractIn-situ macroalgal bioremediation could help prevent and reduce estuarine eutrophication. However, estuaries are dynamic ecosystems characterized by fluctuating abiotic conditions. Therefore, target macroalgal species for in-situ estuarine bioremediation must be able to maintain productivity under a range of challenging abiotic conditions. The aim of this study was to assess the tolerance of the novel bioremediation target Gracilaria transtasmanica to ambient and extreme levels of salinity, air-exposure, and light limitation that occur in estuarine environments. Three separate experiments were conducted to assess tolerance to each factor and photosynthetic functioning and growth were used to quantify the tolerance range of G. transtasmanica in each experiment. Specific Growth Rate (SGR) was significantly affected by salinity, air-exposure, and light limitation. Gracilaria transtasmanica was able to grow in salinities of 5 to 35 ppt, but growth rates decreased with decreasing salinity. Air-exposure periods of up to 9 h were tolerated, but growth rates decreased as air-exposure period increased. Gracilaria transtasmanica was able to maintain growth with a loss of up to 75% of ambient light and was also able to tolerate short periods (48 h) of continuous darkness. Photosynthetic function was unaffected by salinity, air-exposure, or light limitation. These results demonstrate the high tolerance of G. transtasmanica to light limitation, air-exposure and a broad range of salinities. Consequently, this species could be cultivated in a range of habitat types within estuaries. However, the optimal habitats for cultivation will be submerged subtidal channels and lower intertidal mudflats where the impacts of freshwater inflows and air-exposure are reduced.

Wetland geomorphology and tidal hydrodynamics drive fine-scale fish community composition and abundance

Effective restoration of tidal wetlands for fish communities requires clear goals and mechanistic understanding of the ecosystem drivers which affect fish distribution and abundance. We examined fish community responses to abiotic habitat features in two adjacent but dissimilar freshwater tidal wetlands in the Sacramento-San Joaquin Delta, CA, USA, each of which represents a potential restoration configuration. The first wetland was characterized by a broad, intertidal basin with relatively high hydrodynamic exchange with surrounding waterways. The second wetland was characterized by a dendritic network of shallow subtidal channels with relatively low hydrodynamic exchange. Fish community composition significantly differed between the two wetlands, based on permutational analysis of variance. Fish abundance within and among the two wetlands was also highly affected by specific geomorphic and hydrodynamic characteristics: distance from connection with the main external waterway, bed elevation, and water surface elevation. The physical configuration of a restored tidal wetland, in conjunction with the way tides move across the restored landscape, has strong implications for local fishes. Manipulating these elements to create a landscape mosaic of habitat configurations can be an effective tool for targeting desired restoration outcomes, such as specific fish communities or target fish densities.

Designing for the Future: A Climateresponsive and Adaptive Design Framework for Habitat Restoration and Recreation in the Rumney Marsh Area of Critical Environmental Concern (ACEC), Massachusetts, USA

According to the U.S. Fish and Wildlife Service, the Rumney Marsh Area of Critical Environmental Concern (ACEC) north of Boston, has been considered as one of the most significant estuaries of biological importance in Massachusetts. The area comprises of approximately 400 ha of saltmarsh, tidal flats, and shallow sub-tidal channels. Our goal was to develop a landscape design strategy for the marsh that integrates research and design focused on improving habitat, creating recreational opportunities, and mitigating the long-term impacts of climate change. An evaluation of existing case studies on wetland development was developed as a matrix to guide the framework needed and learn how other projects address these issues. A thorough analysis of the site’s quantitative and qualitative data was done to facilitate the process through which the design strategy could take place, focusing on the marsh by extending programs from the surrounding social context, while at the same time enhancing its ecological value, and preparing for climate change. By developing such strategies that are in tune with the environment and sensitive to the natural systems, our proposal tries to establish design interventions to allow access and recreational opportunities while still enhancing the marsh landscape ecology. Through this project a method is developed to create an open space strategy that can support the diverse social interactions and ecological demands of such a wetland system.

Tectonic and sedimentary evolution of a potential supra-detachment fault basin, Archaean Moodies Group (~3.22 Ga), central Barberton Greenstone Belt

Abstract Greenstone belt dynamics are a key to understanding the formation and evolution of continental crust but the scarcity, commonly poor exposure, strong deformation, and high metamorphic grades of many Archaean supracrustal rocks preserved in greenstone belts often hinder geological insights. Exceptionally, the largely siliciclastic Palaeoarchaean (ca. 3.22 Ga) Moodies Group, uppermost unit of the Barberton Greenstone Belt (BGB) in South Africa and Eswatini, allows a detailed understanding of regional depositional processes and stratigraphic architecture due to its low degree of deformation, considerable thickness, generally good exposure, and diverse sedimentary facies. We here investigate the Powerline Road Syncline (PRS) and the adjacent Maid-of-the-Mists Syncline (MMS), two east-west-trending, tightly to isoclinally folded, locally northwardly overturned synclines in Moodies Group strata in the central BGB. The northern and southeastern margins of the PRS and the southern to southwestern margin of MMS are bounded by the bedding-parallel 24-Hour-Camp Fault. Along this fault, Moodies Group strata and stratigraphically underlying units of the Auber Villiers Formation of the upper Fig Tree Group structurally overlie lower Fig Tree strata above Onverwacht Group strata. Stratigraphic architecture and palaeocurrent analysis of Moodies Group strata in both synclines document a northeastward (depositionally downdip) facies transition from proximal fan delta conglomerates to fluvial- to coastal-plain and estuarine sandstones in which thick foresets likely represent subtidal channel fills. The overall deepening- and fining-upward trend in this sequence, corresponding to an increasing mineralogical maturity of sandstones, is partially obscured by local hydrothermal alteration which was contemporaneous with sedimentation, minor volcanism, and sill intrusion. Moodies Group conglomerates and sandstones were largely shed from the rising Onverwacht Anticline to the southwest. Lithologies and stratigraphy in the PRS-MMS region closely resemble strata of the lower Moodies Group in the Sadddleback Syncline, located nearby to the north but across the Inyoka Fault. If the 24-Hour-Camp Fault was part of a group of extensional faults accompanying the rise of the Onverwacht Anticline and of tonalitic-trondhjemitic-granodioritic plutons around the BGB margins at ca. 3 224 Ma, it would have acted as one of numerous basin-bounding normal faults during early Moodies time. This would place the deposition of Moodies Group strata in the PRS-MMS region in a supra-detachment fault environment which was subsequently tightly folded.

A diverse Late Pliocene fossil fauna and its paleoenvironment at Māngere, Auckland, New Zealand

ABSTRACT Excavations at Māngere Wastewater Treatment Plant, Auckland, in 2020 provided New Zealand’s richest and most diverse fossil faunas of mid-Pliocene age (Waipipian Stage, 3.7–3.0 million years old). The vast excavated heap of sandy shell was extensively searched and sieved resulting in the recovery of 266 fossil taxa, (particularly rich in Mollusca including 77 Bivalvia, 105 Gastropoda, 32 Foraminifera, 13 Ostracoda, 11 Bryozoa). The fauna includes several undescribed taxa and additional warm-water Pliocene records for New Zealand. The fauna is most similar in composition and age to the fauna obtained from the Otahuhu Brewery well in the late 1940s. The fauna contains a mixture of taxa from many different shallow marine habitats, from intertidal and subtidal rocky shores and intertidal and shallow subtidal soft sediment flats to exposed and semi-exposed subtidal sandy habitats down to depths of 30–40 m. The shelly deposit is inferred to have accumulated in a current swept subtidal channel during one of the mid-Pliocene warm periods when sea level was high and had flooded an incised river valley that flowed from east to west across the Auckland region.

Onset of the late Paleozoic glaciation in the Lhasa terrane, Southern Tibet

The Late Paleozoic Ice Age is characterized by diverse stratigraphic records with extensive spatial-temporal distribution in the Gondwana. The Lhasa terrane located in northeastern Gondwana during the late Paleozoic developed successive glacial sedimentary records, but the depositional evidence, as well as age constraint for the onset of glaciation, is unknown. This paper provides the first full description of the basal glacial deposits in the Xainza area of Lhasa terrane, southern Tibet. Conodonts present in the carbonate overlying the glacial bed (1 m) dominantly consist of Declinognathodus intermedius, indicating that the initiation of the Late Paleozoic Ice Age in the Lhasa terrane took place in Bashkirian. Three facies associations were recognized: (i) tidal flat association (subtidal channel, bar, intertidal mixed flat), (ii) subglacial association (megaclasts and melt-out diamictite), and (iii) lonestone-bearing heterolithic association (grounding-line fan and iceberg). These facies associations are vertically arranged into a complete transgressive-retrogressive glacial succession. Ice movement direction reconstructed from the imbricated megaclasts, the concordant folds and the lateral distribution of subglacial deposits and glacial marine deposits is consistently from NNE to SSW. These characteristics suggest that the Bashkirian glaciation in the Lhasa terrane is irrelevant to western Australia, implying that these two blocks were separated during the Late Carboniferous.

Miocene-Holocene paleoenvironmental changes in the Tinto River estuary (SW Spain) evidenced by sedimentology, geochemistry and fauna

This paper investigates the paleoenvironmental evolution of a long core extracted in a small cove located in the Tinto-Odiel estuary (SW Spain). The inferred reconstruction is supported by sedimentological, geochemical, paleontological data and dating. Seven phases have been identified, with the transit from Late Neogene marine environments to a subrecent freshwater pond and a final anthropic filling. On the basis of these data, this area was flooded during the maximum of the MIS-1 transgression (6.5-5.2 cal. kyr BP), with the temporary presence of a subtidal channel with phanerogam meadows. During this evolution, three geochemical peaks have been detected, which correspond to 1) the first evidence of mining activities (~4.5 cal. kyr BP), 2) an interval of intensive mining (1850-1960) and 3) an industrial period (1966-1985), affected by the dumping of highly polluting waste into this estuary.

Changes in tidal asymmetry in the German Wadden Sea

The recent morphological development of the German Wadden Sea (North Sea, Europe) has been characterized by expanding intertidal flats and deepening, narrowing tidal channels at declining subtidal volume. This study analyzes the effect of these changes on tidal asymmetry, based on numerical modeling with high-resolution bathymetry data, and discusses possible adaptations of the import and export behavior in intertidal systems. As common descriptors of tidal asymmetry may show a high spatial variability in bathymetrically complex intertidal systems, we develop a novel subregion averaging approach for a more robust trend estimation. Our data reveal a statistically significant decrease in flood and flood current duration in the period from 1996 to 2016 resulting in declining flood dominance or enhanced ebb dominance in most tidal basins of the German Wadden Sea. Mean and peak current asymmetry also indicate significant decreases in mean flood current magnitude. We relate decreasing flood dominance mostly to local bathymetric volume changes rather than tidal amplitude. However, it appears likely that the sum of local effects facilitates the adaptation of regional tidal dynamics which affects especially the northern German Bight. This regional shift is explained by the deceleration of rising tides due to increased friction on laterally expanded intertidal flats and decreased subtidal channel volume. The decrease in flood or increase in ebb dominance, respectively, indicates that the recent trend of sediment accretion in Wadden Sea areas may cease soon.

Ontogeny of a subtidal point bar in the microtidal Venice Lagoon (Italy) revealed by three‐dimensional architectural analyses

AbstractSedimentological and architectural features of meandering subtidal channels are relatively unexplored, and their deposits are commonly investigated based on facies models set up for intertidal meandering channels. The Venice Lagoon (northern Adriatic Sea, Italy) is affected by a micro‐tidal regime and hosts a dense network of active and buried tidal channels. It represents an excellent natural laboratory to improve the current knowledge on subtidal meander morphodynamics and related deposits. In this study, the integration of high‐resolution geophysical images and core data allows reconstruction of the architectural three‐dimensional model of a meandering subtidal palaeochannel, which is buried below a modern subtidal flat. The study palaeochannel was 35 m wide and 3 m deep, and formed three adjacent meander bends and related point bars. A detailed three‐dimensional architectural reconstruction was carried out for deposits associated with one of these meander bends, that was crossed by a minor, low‐sinuosity channel with two minor bank‐attached bars. This reconstruction highlights that the study point bar has a horseshoe shape, which arose from the onset of bar accretion from an already‐sinuous channel. Reconstructed growth stages of the studied bends show that point‐bar accretion can follow different styles of planform transformation, also experiencing simultaneously landward (or seaward) deposition according to the dominant flow direction (i.e. local tidal asymmetry). The analyses show that planform transformations occurred in parallel with elevation changes of the related channel thalweg, which shaped pools with geometry varying with the radius of curvature of the bend. The present study highlights the relevance of high‐resolution three‐dimensional reconstructions to link palaeomorphodynamic processes with related sedimentary products.

Building and Raising Land: Mud and Vegetation Effects in Infilling Estuaries.

Many Holocene estuaries were infilled to form convergent, single‐channel systems, while others remained partially or wholly unfilled. This difference in the degree of infilling depends partly on the balance between fluvial and coastal sediment input and the hydrodynamics that can export sediment. However, it remains unclear to what degree this balance is tipped by mud supply and eco‐engineering vegetation, and by what planform patterns the infilling proceeds. This study aims to explore experimentally how mud and vegetation change the degree and process of infilling, elevate and merge bars above intertidal levels and affect the planform of estuaries. To this end, three experiments were conducted in the Metronome, a flume that tilts periodically to create tidal currents, wherein forced tidal asymmetry resulted in net importing estuaries. In the second and third experiments, mud was supplied and in the third experiment seedlings were released of three vegetation species with eco‐engineering traits at a laboratory scale. With only sand, the estuary fills sufficiently to form a multi‐channel pattern with intertidal bars. Both mud and vegetation settle on intertidal bars and on the fluvial bay‐head delta, thereby contributing to bar stabilization and further estuary infilling, pointing at effective strategies to keep up with future sea‐level rise. This reduces channel mobility and effectively narrows the summed subtidal channel width toward an ideally converging funnel shape. This seems especially effective where vegetation stabilizes the mud. The experiments suggest that a range of steady states exists between the end‐members of an unfilled and a completely infilled, ideal estuary.

Sedimentology and neoichnology of a muddy translating point bar in the fluvio-tidal transition, Serpentine River, BC, Canada

Point bars are common in the fluvio-tidal transition of rivers, yet detailed characterization of their sedimentology and neoichnology is rarely reported. Herein, we present sedimentological and ichnological descriptions for a seaward translating point bar located in the fluvio-tidal transition of the Serpentine River, BC, Canada. This bar accumulates in mainly polyhaline water, and channel flow is tide-dominated. The landward bar has steep channel banks and grain size fines from medium sand in the thalweg to mud in the upper intertidal zone. The seaward side of the bar forms a bench-like morphology that is steeply inclined in the intertidal zone, has a wide, gently dipping platform in the lower intertidal/uppermost subtidal zone, and a steep lower subtidal channel bank. Sediment sizes fine from coarse- to medium-grained sand in the thalweg, to mud in the lower intertidal zone. Medium-grained sand is deposited on the middle- and upper-intertidal zone of the seaward-side of the bar as a result of flow reversal and impingement of the flood tidal current against the seaward side of the translating point bar.The neoichnological assemblage of the intertidal part of the translating point bar is characteristic of brackish-water environments, and comprises low diversities of diminutive structures that occur locally in high densities (Bioturbation Indices 3–4). The neoichnological distribution correlates closely with the macrobenthos distribution, which in turn indicates marine-nutrient distribution. Marine nutrient supply is likely controlled by the bar's morphology. Biogenic structures attributable to Arenicolites, Skolithos, Polykladichnus and Siphonichnus mark the middle and upper intertidal zones, as well as the lower intertidal zone along the landward side of the bar. The trace makers that produce this trace assemblage are resilient to prolonged subaerial exposure and employ diverse feeding strategies. The lower intertidal zone along the seaward side of the bar is affected by decreasing current velocities across the wide bench-like morphology, which permits regular deposition of marine nutrients. Here, population counts are high and trace makers specialize in surface deposit- and filter-feeding. Traces include Gyrolithes-like structures and Siphonichnus. The Gyrolithes and Gyrolithes-like burrows that are produced by S. kowalevskii at the study site are hypothesized to potentially reflect the trace maker's anatomical predisposition, and not represent some spatial or anchoring advantage.This work represents the first published study on the neoichnology of a tide-dominated, translating point bar in the fluvio-tidal transition. The model we present is intended as an analog to show the variability in fluvio-tidal point bars and how they might be manifested in the sedimentary record.

The effects of wind‐generated currents on velocity asymmetry in tidal basins with varying geometries

AbstractGeomorphologic characteristics of tidal basins have been shown to control tidal asymmetry and associated sediment transport potential in coastal regions. In this study, we examine how winds modulate horizontal velocity asymmetry patterns in shallow tidal basins. Numerical modelling experiments for a series of idealized basins in which planform shape and bathymetry were varied, reveal that an increase in wind speed promotes more extreme horizontal velocity asymmetry (larger velocity asymmetry values) without substantially altering the overall spatial pattern of velocity asymmetry throughout the domains. The wind forcing primarily influences mean and peak flow velocities, with a limited effect on tidal harmonics. Changes to the velocity asymmetry patterns are most evident for wind speeds of 6 m/s and greater, and for wind directions parallel to the main axes of the basins’ tidal channels. However, the velocity asymmetry is strongly depth‐dependent. Shallow intertidal basin regions are characterized by a downwind‐directed increase in velocity asymmetry, whereas deeper subtidal channels display asymmetry changes in the opposite direction. Additionally, the timing and duration of a wind event are found to influence the velocity asymmetry patterns. Wind events coinciding with flooding tides result in the most noteworthy differences between the relative size of the peak flood‐ and ebb‐directed currents inside the shallow basins, for wind event durations of both 3 and 6 h.

Revisited sediment budget with latest bathymetric data in the highly altered Yangtze (Changjiang) Estuary

Most river-deltas of the world have been extremely altered by anthropic activities, where a regime shift from net accretion into net erosion may have occurred. In this study, subtidal morphodynamic variations in the Yangtze Estuary (YE) are elaborately analyzed for their causalities using high resolution DEM data from bathymetric surveys conducted every two years from 2007 to 2019; sediment budgetary balance in the estuary has been updated accordingly with mean annual depositional/erosional sediment amounts. The results show that subtidal channel erosion has occurred almost over the whole YE with a mean annual erosional rate of −5.59 cm/yr during the study period. Peak erosion occurred both in the South Branch and the delta front with mean annual erosional rates of −12.64 cm/yr and −8.11 cm/yr, respectively. The erosion lessened in the middle estuary where sandy shoals prevail, and a net accretive rate of 3.13 cm/yr was solely measured at the Chongming shoal. Negative correlation between estuarine erosional volume and riverine sediment discharge demonstrates the great impact of upstream hydro-engineering projects on estuarine morphodynamic change, but large-scale estuarine engineering projects also exert remarkable influence on local morphodynamics, evidenced by the presence of deep erosional belts near the projects. Annually eroded sediment amounts were estimated as 166 Mt/yr and 206 Mt/yr in the distributary channels and the delta front during the period 2007–2019, and the former was almost offset by recent sand mining amount of 143 Mt/yr from the distributary channels for land reclamation. Moreover, contemporary eroded sediment mass and sand mining amount from the tidal river reach between Datong and Xuliujing were reckoned as 77 Mt/yr and 44 Mt/yr, respectively. Our analysis further show that recently 124 Mt/yr and 153 Mt/yr of sediment discharge into the tidal river reach at Datong station and the YE at Xuliujing station account for merely 27.5% and 37.7% of their corresponding values before the 1990s, respectively. Annual sediment amount bypassing the estuary into the open sea has decreased by 37.8% from pre-1990s 370 Mt/yr to recent 140 Mt/yr, leading to recently severe erosion in the delta front. It is therefore highlighted that the estuarine system in response to natural and anthropogenic pressures is very dynamic, and the impacts of various engineering projects in the source-to-sink system should be fully taken into consideration when predicting its morphodynamic response in the estuary.

Complex Tidal Marsh Dynamics Structure Fish Foraging Patterns in the San Francisco Estuary

Mechanisms driving the consumption and transport of tidal marsh nutrients and energy by fishes are of key interest in the San Francisco Estuary, CA, USA. By combining multiple data sources (gill-net catches, gut contents, channel morphology, tides), we modeled spatial and temporal patterns of fish abundance and gut fullness across a tidal marsh elevation gradient. Channel depth, microhabitat, and tide were important predictors of fish abundance and gut fullness. Species, feeding guild, and season were also important to fish abundance but not to gut fullness, suggesting that abundance was more related to physical constraints of shallow water than to prey availability. Multiple feeding guilds overlapped in space and time at interaction hotspots in subtidal channel habitat near the marsh entrance. In contrast, fish use of shallow intertidal marsh channels was more variable and indicated tradeoffs between foraging and predation. Gut content analysis revealed moderate-to-high gut fullness for all feeding guilds and models predicted high gut fullness in subtidal reaches during tidal flooding, after which fish fed intensively throughout the marsh. While mysids, amphipods, and detritus were common prey among feeding guilds, variation in prey consumption was apparent. Overall, complex tidal marsh hydrogeomorphology driving land-water exchange and residence time may diversify and enhance benthic and pelagic food web pathways to fishes and invertebrates. Furthermore, these findings substantiate the notion that dynamic tidal marshes in this system can support robust secondary production, foraging by multiple feeding guilds, and trophic transfer by fishes to the estuarine mosaic.

Eocene larger foraminiferal biostratigraphy, depositional history and paleogeography of the Sylhet Limestone of the Mikir Hills of Assam, NE India: Implications for an Open Tethys

This study presents results of integrated larger foraminiferal biostratigraphy, lithofacies and stable carbon isotope (13 C org) analysis carried out in the Sylhet Limestone of Dillai Parbat Limestone Mine succession, Karbi Anglong District, Assam. Larger foraminiferal assemblages assign a middle Eocene age to the studied succession of Sylhet Limestone. The Shallow Benthic Zone (SBZ) 13 and SBZ 16-18 and a barren interval in between is recognized in the studied part of the Sylhet Limestone. The SBZ 13 Zone (early Lutetian) is represented by fossiliferous limestone at the base of the section and is inferred to have been deposited in a subtidal environment. The overlying barren interval lies in the arenaceous interval and was likely deposited in a subtidal channel sand shoaling bars. The upper part of the section ismarked by SBZ16-18 (late Lutetian to Bartonian) and was deposited in subtidal channel sand inner neritic zone environments, followed by intertidal marl to subtidal limestone. The organic carbon stable isotopic data reveals a sharp negative excursion at about 34-35m of the succession, which may be correlated with Middle Eocene Climatic Optimum (MECO) and/or vegetation types. This and earlier studies from India and elsewhere indicate that during the middle Eocene, the Neo-Tethys Sea was open and connected through the East and West coasts of India, Northeast India, western Himalaya, and most of the Middle East and southeast Europe. This vast area produced enormous amount of petroleum.

Resource utilization of puffer fish in a subtropical bay as revealed by stable isotope analysis and food web modeling

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 626:161-175 (2019) - DOI: https://doi.org/10.3354/meps13045 Resource utilization of puffer fish in a subtropical bay as revealed by stable isotope analysis and food web modeling Mathilde Lemoine1,2, Tom Moens2, Anna-Maria Vafeiadou2, Luis Artur Valões Bezerra3,4, Paulo Lana1,* 1Laboratório de Bentos, Centro de Estudos do Mar, Universidade Federal do Paraná, 83255-000 Pontal do Paraná, Paraná, Brazil 2Ghent University, Biology Department, Marine Biology Lab, Krijgslaan 281/S8, 9000 Gent, Belgium 3Laboratório de Análise e Síntese em Biodiversidade (LASB), Programa de Pós-Graduação em Ecologia e Conservação (PPGEco), Universidade Federal do Paraná, Centro Politécnico, 81531-980, Curitiba, Paraná, Brazil 4Biology Centre of the Czech Academy of Sciences, Institute of Hydrobiology, Čské Budějovice, Czech Republic *Corresponding author: lana@ufpr.br ABSTRACT: Estuaries often comprise a habitat mosaic, the connectivity of which depends in part on mobile organisms that move in between habitats for feeding and breeding. We assessed resource utilization by 2 co-existing puffer fish species, Sphoeroides testudineus and Sphoeroides greeleyi, in mangroves, saltmarshes and shallow subtidal channels of a subtropical bay. We hypothesized that puffer fish migrate into mangroves mainly to feed and that the coexistence of the 2 species may be explained by differences in resource utilization and/or by a differential preference for different foraging grounds. We combined a stable isotope approach with an Ecopath model that contrasted detritus-driven and herbivory-driven foodweb scenarios. The most parsimonious foodweb scenario involved the feeding of puffer fish on benthic invertebrates associated with Spartina marshes. This emphasizes the importance of saltmarshes as feeding grounds for both puffer fish species, independently of where they were sampled. Small differences in isotopic signatures between S. greeleyi and S. testudineus indicated major resource overlap, but also some degree of food partitioning probably through the selection of differently sized prey. The smaller S. greeleyi consistently had a slightly higher trophic level than the larger S. testudineus. S. testudineus had larger isotopic niche sizes as a consequence of greater inter-individual variation in resource use. Our results emphasize the importance of considering multiple habitats and foodweb scenarios when investigating resource use and species interactions in estuarine ecosystems. KEY WORDS: Sphoeroides testudineus · Sphoeroides greeleyi · Isotopic analysis · Diet · Mangrove · Saltmarsh · Subtropical bay · Habitat connectivity Full text in pdf format Supplementary material PreviousNextCite this article as: Lemoine M, Moens T, Vafeiadou AM, Bezerra LAV, Lana P (2019) Resource utilization of puffer fish in a subtropical bay as revealed by stable isotope analysis and food web modeling. Mar Ecol Prog Ser 626:161-175. https://doi.org/10.3354/meps13045 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 626. Online publication date: September 12, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Multi-day water residence time as a mechanism for physical and biological gradients across intertidal flats

Tidal flats with shallow-sloping bathymetry under meso-to macrotidal conditions allow organisms to occupy similar tidal elevations at different distances from subtidal channels. As water floods or ebbs across such tidal flats during a single tidal cycle, upstream organisms may modify water properties such as chlorophyll concentration, while physiochemical properties may change due to close association with sediments. Here we report evidence for an additional mechanism establishing cross-shore gradients: multi-day water residence times, in the sense that even if water completely drains into subtidal channels at low tide, a large fraction returns to the flats on the next high tide. We applied circulation modeling and empirical measurements of water properties and benthic secondary production to a 1-km-wide tidal flat in Willapa Bay, Washington, USA. From the circulation model, water parcels on this intertidal flat have residence times up to 2 d, that is, water found on the flat at one high tide returns to the intertidal zone for a median of 4 successive semidiurnal high tides. Modeled residence times generally increased towards shore. Four empirical datasets showed cross-shore gradients consistent with modeled residence times: Salinity time series lagged towards shore; water column chlorophyll declined towards shore at fixed stations (near-bottom) and in surface transects more than could be explained by benthic suspension-feeding during a single transit of water; and oyster (Magallana = Crassostrea gigas) condition declined 25% over 0.5 km from channel to shore, independent of tidal elevation. One environmental measurement was more consistent with within-tide change, as water temperatures warmed towards shore on afternoon flood tides but showed no tidal-cycle lags. Taken together, these patterns suggest that multi-day water residence times can contribute to environmental heterogeneity from channel to shore on tidal flats, acting orthogonally to well-recognized estuarine gradients in residence time from ocean to river.

Significant Techno-stratigraphic development of the Caroni Basin, recorded in outcrops of the late Neogene Manzanilla and Springvale Formations, NE Trinidad

The Manzanilla and Springvale Formations outcrop along a 1.9 km stretch on the eastern coast of Trinidad, and provide vital information about the development of the Caroni Basin and north-central Trinidad. The Manzanilla Formation contains deposits that range from deepwater to delta plain facies. Sandstone turbidites are the oldest deposits and these transition upward into muddy slope deposits then shelf mudstones, siltstones and sandstones. The occurrence of sporadic conglomerate beds suggests debris flows or other coarse-grained sediment gravity flows additionally entering the basin at this time. The upper parts of the Manzanilla succession reflect marginal marine environments with delta front (including mouth-bar), crevasse splay, bay fill and marsh deposits. Most of these deposits originated as the northernmost part of the east to northeast flowing paleo-Orinoco Delta. The anomalous interfingering of coarse-grained lithic-rich debris flow deposits with the delta-derived deposits, strongly suggests a derivation directly from the steep-sloped alluvial-fan and fan-delta deposits eroding off of the Northern Range orogenic belt, some 10 km to the north. The facies associations of the Springvale Formation reflect channelized estuarine environments strongly influenced by tidal processes. Subtidal channels associate with and are succeeded by wave and tidal influenced intertidal facies and their overlying supratidal mudstones, paleo-sols and lignite beds.Examination of these two formations reveals that the Neogene Caroni Basin developed quite differently from the coeval Southern and Columbus basins to the south. The Southern and Columbus Basins are true foreland basins with growing accommodation space and expanded shelf section due to the movement of huge listric faults. When compared to similar aged formations in the Southern Basin, the Caroni Basin succession is relatively thin, starved of sediment, contains internal discontinuities and tectonically derived coarse-grained conglomerates. This contrast is due to the fact that the Caroni Basin is sited immediately adjacent to the northern Trinidad zone of Caribbean and South American plate-margin convergence. The compressional forces acting on the basin produced alternating periods of uplift/erosion and subsidence which inhibited continuous deposition. The outcrops examined herein present new detail of the tectonic impact on the evolving Caroni foreland basin within northern Trinidad, where compression-driven base level changes left their signals in the foreland succession.

Facies architecture of the Cambrian deposits of the Baltica shelf in the Lublin Basin, SE Poland

In the Cambrian, the Lublin Basin was a shallow-water area, located on the western edge of the Baltica palaeocontinent. The Cambrian sedimentary sequence, forming the lower part of the sedimentary cover of the North European Platform, is lithologically diversified and reflects dynamic variation in depositional environment. This paper presents the distribution of palaeofacies and sedimentary environments in the early Lublin Basin, including changes in their lateral extent during its evolution in the Cambrian. In order to evaluate the facies architecture of the Lublin Basin, a sedimentological analysis was carried out. On the basis of the detailed logging of drill cores, lithofacies made up of conglomerates, sandstones, mudstones and heterolithic deposits were distinguished; 16 lower-rank sublithofacies were identified. Their specific assemblages are indicative of shelf-type lithofacies associations, i.e. (1) tidal flat with muddy, mixed and sandy tidal plain sublithofacies including subtidal channels; (2) barrier – lagoon; (3) shoreface with lower, middle and upper shoreface subassociations; and (4) offshore with upper and lower offshore subassociations, including sandy tidal ridges. During the early Cambrian, the lateral variability and environmental succession indicate a transgressive, long-term trend and the migration of a lagoonal environment across wide tidal plains and the shoreface up to an offshore environment. The Lublin Basin reached its greatest lateral extent and maximum depth in the upper lower Cambrian. Next, an opposite trend began and during the middle Cambrian a regression cycle is recorded in successive changes in sedimentary environments that reflect a progressive shallowing. Multiple changes in adjacent environments indicate repeated and cyclical, lower-rank ingressions.