Shallow Water Estuary Research Articles

Documenting Loss and Fragmentation of Intertidal Oyster (Crassostrea virginica) Reefs in a Subtropical Estuary

Intertidal reefs of Crassostrea virginica (eastern oyster) provide ecologically valuable habitat in estuaries along the Atlantic coast of North America. In Mosquito Lagoon, a shallow-water estuary on the east coast of central Florida, USA, historical aerial imagery was used to document a 24% decline in the live C. virginica reef area between 1943 and 2009. Using 2021 imagery, every living and dead reef in the same region was manually digitized to identify changes during the intervening 12 years. Positive impacts of C. virginica reef restoration that took place between 2007 and 2021 were also digitized to quantify long-term restoration impact. Natural, live C. virginica reef coverage throughout the system was found to have decreased by 50.6% between 2009 and 2021 and, thus, 62.6% between 1943 and 2021. This was attributed to reef fragmentation, reef footprint loss, boating activity, and mangrove expansion. Of the 2542 live reefs identified using 2009 imagery, 219 reefs fragmented, 988 reefs no longer had an identifiable footprint, and 598 reefs contained visible mangroves with non-continuous canopies. Conservatively, 63.6% of directly restored reef area was classified as living reef in 2021, and 74.5% of restoration projects were more than 50% live reef. Dead reef area decreased by 57.9% throughout the system. Understanding changes in C. virginica reef acreage, reef numbers, and mangrove expansion is essential for resource management, restoration practices, and tracking climate change impacts on publicly protected estuaries.

A detailed luminescence chronology of the Lower Volga loess-palaeosol sequence at Leninsk

We present a detailed luminescence chronology of the loess-palaeosol sequences in the Lower Volga region of Russia at the Leninsk site – an important palaeogeographic archive describing the climate and environmental conditions of regressive stages of the Caspian Sea. The chronology of these sediments has received very little attention compared to the under- and overlying marine deposits. The degree of bleaching was addressed by making use of the differential resetting rates of quartz and feldspar. Our results show that the quartz OSL and feldspar pIRIR 50,290 signals were sufficiently bleached before deposition and uncertainties in bleaching have a negligible impact on the reliability of the luminescence ages. The combined quartz OSL and K-feldspar pIRIR 50,290 chronology constrains the main stages of the Northern Caspian Lowland evolution during the Late Quaternary. During early MIS 5 (130–120 ka), the northern part of the Lower Volga was covered by a shallow brackish water estuary of the warm Late Khazarian Caspian Sea transgression. After ∼122 ka, the Volga incised the Northern Caspian Lowland surface following sea-level decrease and the start of subaerial conditions at Leninsk. Loess accumulation rate increased towards the end of MIS 5 and two palaeosols of presumably MIS 5с and MIS 5a age formed, exhibiting features evidencing a dry, cold climate, influenced by long seasonal flooding by the Volga River. Cryogenesis affecting the MIS 5a soil is a regional phenomenon and is dated to between ∼70 and 90 ka. The overlying thick Atelian loess unit formed during the cold periods of MIS 4 and MIS 3. Clear erosional features at the top of the Atelian loess are constrained by luminescence to ∼35 to ∼24 ka, allowing reconstruction of erosion of 150–200 cm of loess.

Application of Marine Spatial Planning tools for tidal stream farm micro-siting

The operation of tidal stream energy farms may interfere with other uses of the marine space, especially in depth-limited areas (estuaries, rivers, etc.) which are typically subject to multiple demands of use. The Marine Spatial Planning Directive (MSP) was passed by the European Commission in 2014 to ensure a harmonic coexistence between different maritime activities and to protect the marine environment. In this context, the objective of this work is to present a methodology based on MSP tools for tidal-farm siting in depth-limited areas. The methodology is illustrated through a case study: Ria de Ribadeo, a shallow-water estuary in NW Spain. Having considered a number of uses (archaeological, biodiversity, fishing, aquaculture, recreational and navigation), two exploitable tidal farm sites (Areas A and C) with annual energy densities of 1 GWhm−2 were found. The estuary is periodically dredged to maintain navigation. Dredging-related risks were analysed using a novel indicator, the Dredging Associated Risk (DAR), based on which Area C was discarded and Area A had its exploitable surface area reduced by 25%. In sum, the methodology proposed was proven to be effective for tidal stream farm planning.

The summer soundscape of a shallow-water estuary used by beluga whales in the western Canadian Arctic

The soundscape is an important habitat component for marine animals. In the Arctic, marine conditions are changing rapidly due to sea ice loss and increased anthropogenic activities such as shipping, which will influence the soundscape. Here, we assess the contributors to the summer soundscape in the shallow waters of the Mackenzie River estuary within the Tarium Niryutait Marine Protected Area in the western Canadian Arctic, a core summering habitat for beluga whales (Delphinapterus leucas Pallas, 1776). We collected passive acoustic data during the summer over four years, and assessed the influence of physical variables, beluga whale vocalizations, and boat noise on sound pressure levels in three frequency bands (low: 0.2–1 kHz; medium: 1–10 kHz; high: 10–48 kHz) to quantify the soundscape. Wind speed, wave height, beluga vocalizations, and boat noise were all large contributors to the soundscape in various frequency bands. The soundscape varied to a lesser degree between sites, time of day, and with tide height, but remained relatively constant between years. This study is the first detailed description of a shallow summer soundscape in the western Canadian Arctic, an important habitat for beluga whales, and can be used as a baseline to monitor future changes during this season.

Fast-start escape performance across temperature and salinity gradients in mummichog Fundulus heteroclitus.

Fast-start predator-escape performance of mummichogs Fundulus heteroclitus was tested across field-informed variation in temperature (24, 30 and 36°C) and salinity (2, 12 and 32 ppt). Performance was similar across temperatures and salinities when fish were allowed to acclimate to these conditions. However, when mummichogs experienced acute temperature changes, performance exhibited thermal dependence in two contrasting ways. Fast-start turning rates and linear speeds varied directly with the temperature at which the manoeuvre was executed, but these aspects of performance varied inversely with acclimation temperature, with cool-acclimated fish exhibiting faster starts across test temperatures. Temperature effects were consistent across salinities. These results suggest that while mummichogs increase performance with acute temperature increases, long-term rises in sea temperature may cause these fish to become more susceptible to predation during abrupt cooling events, such as when storm events flood shallow water estuaries with cool rainwater.

The influence of dredging for locating a tidal stream energy farm

Development of third generation of Tidal Energy Converters (TECs) may boost the exploitation of the tidal stream energy resource in depth-limited regions. The hydrodynamic conditions of depth-limited tidal sites are highly influenced by changes in the bathymetric conditions, such as sedimentation and/or dredging operations, which are typical of these regions. Consequently, significant variations in terms of magnitude and predominant flow direction can be present during the operating life of tidal farms, which may compromise their viability. The objective of this work is to explore the potential effects caused by dredging operations on the performance of tidal farms and to propose initial threshold values for key variables (flow magnitude and direction, operating hours of TECs), to ensure the techno-economic viability of tidal farms. For this purpose, three potential tidal sites in a shallow water estuary (Ribadeo, NW Spain), were used as case study. Significant variations were found between the pre- and post-dredging scenarios in terms of energy production, with annual variations exceeding 38%, for the tidal sites present in the region. In sum, the present study highlights the importance of considering the potential bathymetric changes in the decision-making process, when planning the installation of tidal farms in depth-limited regions.

Drones detect illegal and derelict crab traps in a shallow water estuary

AbstractThe issues surrounding illegal, unregulated and unreported fishing, and that of abandoned, lost and discarded fishing gears, leading to ghost fishing, are intensifying. Estuarine crab trapping is likely subject to high levels of illegal and potential ghost fishing, because it also has good economic incentives regarding potential catch, low gear acquisition costs and accessible fishing grounds. To improve the efficiency and effectiveness of fisheries monitoring, control and surveillance operations, the efficacy of small consumer‐grade drones for sighting traps in an estuary in NSW, Australia, was tested. Twelve sets of two flights were undertaken at 20 and 30 m altitude over a 600‐m stretch of estuary for 5 days to quantify the detectability of submerged mesh traps of three different mesh colours. The drone was able to detect the majority of traps efficiently, with depth in relation to water clarity being the main factor affecting detection. In shallow water, detection rates were high for all mesh colours, but in the slightly deeper placements, orange traps were more readily detected. This study demonstrates that drones could be an efficient and reliable tool for rapidly assessing areas for illegal and derelict traps and can be supplemented into land or vessel‐based fisheries operations.

Modelling the Main Hydrodynamic Patterns in Shallow Water Estuaries: The Minho Case Study

Numerical models are key tools to characterize hydrodynamical patterns of coastal environments and anticipate the potential effects of hazardous and extreme events, anthropogenic intervention or climate change. In this work, the openTELEMAC-MASCARET modelling system was selected to represent the dynamics of the Minho estuary, a very shallow estuary located at the Northwestern Iberian Peninsula coast. Calibration and validation results confirm the accuracy of the numerical tool, with small root mean square errors, close to null bias and the close to unit correlation and skill coefficients obtained for water level and currents velocity at several estuarine locations. The obtained results depict a tide dominated estuary with a delay in the tide phase and a marked asymmetry in the tide curve that increases upriver. Additionally, an upstream diminution of M2 and an upstream augmentation of M4 was observed, classifying this estuary as flood-dominated. The represented current patterns show that variations in the intensities of the main driving forces alter the behaviour of the hydrodynamical patterns within the estuary, with a clear dependence on bathymetric and topographic characteristics. During flood events, larger estuarine regions become submerged due to the low margins and the wetland characteristics, highlighting the need for accurate numerical models that can be used as a decision-making support tool for effective and integrated estuarine management.

SEAGRASS COMMUNITY STRUCTURE IN TUNDA ISLAND GULF OF BANTEN

Seagrass, as an aquatic angiosperms which are completely adapted to live in the marine environment and shallow water estuaries, is one of the most highly productive marine ecosystems. Under the increasing of global water temperature, coupled with nutrient over-enrichment, the community structure of seagrass may transform as the alteration of ecological functions followed. This condition may also happen in Indonesian coastal waters, including Tunda Island on the Gulf of Banten which received excessive nutrients from the mainland. Study of seagrass community in Tunda Island has been carried out using line transect method perpendicularly to the shore with the 1x1 meter transect plots within 10 meters interval. Community structure as density, coverage, diversity index and dominance index of seagrass had been observed in 4 stations. The results showed that there were five species of seagrass were recorded in this area, namely Cymodocea rotundata, Syringodium isoetifolium, Enhalus acoroides, Halophila ovalis and Thalassia hemprichii. The distributions and species composition were varied and generally dominated by Thalassia hemprichii with 48.25 shoots m*2 density. The diversity index obtained from the research was 0.84 as well as the dominance index was 0.55. It showed that the diversity of seagrass at Tunda Island is low and no high dominance among species. The status of seagrass meadows in Tunda Island was classified as poor since the total coverage was only 22 %. Further observation of correlation among other organisms such as macroalgae and grazers in the ecosystems will be necessary to investigate the ecological alteration.

The Fossil Cypraeidae of the Buckingham Member (Unit 10), Tamiami Formation of Southern Florida: (Mollusca: Gastropoda: Cypraeidae)

The oldest recorded fossil Cypraeidae from southern Florida date from the late Zanclean-early Piacenzian Pliocene (circa 3.8-3.6 million years ago - hereinafter “mya”) in the Myakka Lagoon System, a shallow water estuary that lies beneath the present day Sarasota area. Shallow water sea grass beds and nascent shoreline mangrove forests hosted seven Cypraeidae species in five genera. Determining the origins of these species is challenging as only steinkern casts have been found in adjacent lower layers. However, enough features are present in two of the casts to infer the ancestral presence of two of the genera. For the other genera and species, a comparison of features with the northern Florida Panhandle Cypraeidae populations dating from the Burgdigalian Miocene (16-20 mya) does suggest certain affinities. However, no direct lineage can be asserted with any confidence. The sea bed deposit layer of this period has been designated the Buckingham Member of the Tamiami Formation of southern Florida.

Acoustically Measured Distribution and Abundance of Atlantic Menhaden (Brevoortia tyrannus) in a Shallow Estuary in Long Island, NY

Atlantic menhaden (Brevoortia tyrannus) is an euryhaline forage fish abundant along the eastern coast of the USA that seasonally migrates between the open ocean and shallow water estuaries. These fish are known for forming large, dense schools and are important prey for piscivorous fish, seabirds. Following several large fish kills in the late spring of 2015 in the western Peconic Estuary in Long Island, New York, we conducted multiple surveys during the spring, summer, and fall using scientific echosounders to quantify menhaden abundance in this region. Acoustic backscatter data were used to estimate numeric abundance and biomass of menhaden for the western Peconic Estuary. We found that the 2015 fish kills represented between 7 and 18% of the total local population (~ 2.4 million) that were present at the time. Significant changes in target strength distributions during the study suggest that the size classes of menhaden present in the estuary change as fish grow or migrate in and out of the estuary. This study demonstrates that vertical beam active acoustics is a viable method for quantifying forage fish in a very shallow (< 4 m depth) estuary.

Not all snaps are from shrimp: Broadband, impulsive sounds from different benthic organisms can provide information on animal presence and behavior

Snapping shrimp are a dominant source of sound in many marine environments; however, there are several other benthic organisms which produce broadband, impulsive sounds as part of their daily activity. We used a passive acoustic recorder with a video camera to identify and categorize the soniforous behaviors of several different species (fish and bivalves) in both laboratory and field environments. Bay scallops (Argopecten irradians) in shallow water estuaries in New York “cough” when they move via jet propulsion as well as to clean their filter feeding apparatus. Additionally, the substrate they are “scooting” on can alter the characteristics of their “cough.” Parrotfish (multiple species) “chomp” as they forage on seagrasses and surgeonfish (Acanthuridae) “scrape” algae from hard substrates in Caribbean lagoons. We investigated whether these signals can be distinguished from other broadband sounds occurring in the marine environment and, if so, how longer-duration passive acoustic recordings can be used to monitor the abundance or behaviors of these animals.

Late Miocene-Pliocene coastal acid sulphate system in southeastern Australia and implications for genetic mechanisms of iron oxide induration

Ferricrete – sediment cemented by iron oxides and hydroxides – is common in subaerial weathering environments around the world. Formed under alternating oxidising and reducing conditions, ferricretes record pedogenetic processes of translocation and concentration of iron and trace elements in the soil. Given their stability and high preservation potential, ferricretes can provide insights to ancient soil forming and weathering processes.In this study the key processes controlling ferricrete geochemistry in a Neogene strandplain are identified and interpreted in the context of a coastal acid sulphate weathering system. Textural and geochemical variations in sediment indurated by hematite and goethite represent a record of in situ induration, erosion, and reworking. This development took place within an environment of fluctuating pH and Eh and subaerial wetting and drying cycles. We distinguished depositional and post-depositional processes based on the results of whole rock geochemistry, hyperspectral mineralogy, and major and trace element maps of petrographic thin sections. The ferricretes have three morphological types: flat-lying indurations, concentric pisoliths, and rounded nodules with fragmented internal textures. Successive laminae of Fe-oxides and hydroxides in all morphological types of ferricrete have variable Fe, Al, and Si abundances, reflecting cyclic precipitation and groundwater chemistry changes. Episodic wetting and drying of near coastal sediments was superimposed on a long-term trend of marine regression and local tectonic uplift (from ~7Ma to present). This resulted in the diachronous exposure of relatively reduced shoreline sediments and concomitant acid production due to ferrolysis and the oxidation of biogenic sulphide. Local landform variations contributed to a wide variety of pedogenic processes and subsequent ferricrete formation. Acid sulphate weathering recorded by these indurated sediments is similar to conditions that are observed at present in the shallow water estuary of the Lower Lakes, near the mouth of the Murray River.

Effects of Clam Aquaculture on Nektonic and Benthic Assemblages in Two Shallow-Water Estuaries

ABSTRACT Aquaculture of the northern quahog (=hard clam) Mercenaria mercenaria (Linnaeus, 1758) is widespread in shallow waters of the United States from Cape Cod to the eastern Gulf of Mexico. Grow-out practices generally involve bottom planting and the use of predator exclusion mesh. Both the extent and scale of clam farms have increased in recent decades resulting in concerns regarding the impacts of these practices on estuarine fauna. Seasonal distribution, abundance, biomass, species richness, and community composition of nektonic, demersal, epibenthic, and infaunal organisms were examined in cultivated and uncultivated shallow-water habitats in Virginia and New Jersey. The results reveal that clam aquaculture, as practiced in both Virginia and New Jersey, has remarkably few quantifiable impacts on estuarine fauna. Seasonal variations were observed in the biota, but of the 39 population and community metrics tested, mean values associated with 26 did not differ between cultivated and uncultivated are...

Hidden Components in Tropical Seascapes: Deep-Estuary Habitats Support Unique Fish Assemblages

Tropical coastal seascapes are biodiverse and highly productive systems composed of an interacting mix of habitats. They provide crucial ecosystem services that support people’s livelihoods, yet key components of these seascapes remain unstudied. We know little about the deep (>2 m) subtidal areas of tropical estuaries, because, due to gear restrictions, there have been no detailed studies of the habitats they contain and the fish that use them. Consequently, potentially important functions and linkages with surrounding habitats remain unknown. Using unbaited videos, an approach capable of sampling the full breadth of benthic habitats and whole fish assemblages, we investigated patterns of fish occupancy of the deep subtidal habitats (2–20 m) in one of Australia’s largest tropical estuaries. We identified 19 taxa not previously recorded from estuaries of tropical eastern Australia, along with 36 previously identified estuary taxa. Three recognisable fish assemblages were associated with distinct benthic habitat types: open bottom fine sediment, seagrass and structurally complex rocky areas. In deep water, habitats often overlooked in shallow water become important, and there are sharp differences in habitat function. Deep subtidal habitats are potentially an important zone for direct interaction between estuary and marine fauna, with a range of consequences for intertidal habitat use and nursery ground functioning. The interface between marine areas and the shallow-water estuary may be richer and more complex than previously recognised.

Formation, Movement, and Restoration of Dead Intertidal Oyster Reefs in Canaveral National Seashore and Mosquito Lagoon, Florida

ABSTRACT Globally, 85% of shellfish reefs have been lost during the past century. The severe loss of the eastern oyster Crassostrea virginica has encouraged different types of restoration efforts in the United States. In Mosquito Lagoon (ML), a shallow-water estuary on the east coast of central Florida, restoration focuses on providing additional substrate for larval recruitment via deployment of stabilized oyster shell. To assess the current number and area of natural, dead, and restored oyster reefs within ML, aerial photographs from 2009 were digitized using ArcGIS software. All reefs were screen digitized using a reef “signature” to estimate the surface area of each reef type. The maps from 2009 were then used as a guide to digitizing the historical aerial photographs (1943, 1951, 1967, 1971, 1984, 1995, and 2006). Oyster habitat within ML has decreased by almost 15 hectares between 1943 and 2009, which constitutes 24%of the 1943 lagoon-wide coverage. The impacts were greater in Canaveral National Sea...

Spatiotemporal distribution and composition of phytoplankton assemblages in a coastal tropical lagoon: Chilika, India.

The Asia's largest lagoon, Chilika, is a shallow water estuary and a designated "Ramsar" site located in the east coast of India. The spatiotemporal diversity of phytoplankton based on the monthly sampling between July 2011 and June 2012 was investigated in relation to physicochemical variables of the surface water column from 13 stations. The salinity was minimum (average 9) during the monsoon which was primarily due to riverine discharge. As the season progressed towards post-monsoon, average salinity of the whole lagoon reached to 10 which further increased to 20 during pre-monsoon season. A total of 259 species of phytoplankton, mostly dominated by the Bacillariophyta (138 species) followed by Dinophyta (38 species), Chlorophyta (32 species), Cyanophyta (29 species), Euglenophyta (18 species), and Chrysophyta (4 species), were recorded in this study. Different ecological sectors of the lagoon (except the northern sector) were dominated by diatoms, while the northern sector due to its freshwater regime supported large population of euglenoids. Based on the multivariate ordination analysis, salinity regime and light availability played important role in determining the distribution, diversity, and composition of phytoplankton communities. Overall, this study documented a very high diversity of phytoplankton and highlighted the importance of taking extensive sampling in getting a clearer understanding of phytoplankton community structure in less-studied environments such as Chilika lagoon.

Wave attenuation experiments over living shorelines over time: a wave tank study to assess recreational boating pressures

With sea level rise, erosion, and human disturbances affecting coastal areas, strategies to protect and stabilize existing shorelines are needed. One popular solution to stabilize while conserving intertidal habitat is the use of “living shoreline” techniques which are designed to mimic natural shoreline communities by using native plants and animals. However, little information is available on the success of living shoreline stabilization. This project evaluated the wave energy attenuation associated with living shorelines that contained Crassostrea virginica (eastern oyster) and/or Spartina alterniflora (smooth cordgrass) in a wave tank. Four living shoreline techniques were assessed, including a control (sediment only), oysters alone, cordgrass alone, and a combination of oysters plus cordgrass. Time since deployment (newly deployed, one-year after deployment) was also assessed to see how wave energy attenuation changed with natural oyster recruitment and plant growth. Wave energy was calculated for each newly deployed and one-year old shoreline stabilization treatment using capacitance wave gauges and generated waves that were representative of boat wakes in Mosquito Lagoon, a shallow-water estuary in Florida. All one-year old treatments attenuated significantly more energy than newly-deployed treatments. The combination of one-year old S. alterniflora plus live C. virginica was the most effective as this treatment reduced 67 % of the wave energy created by a single recreational boat wake, compared to bare sediment. Natural resource managers and landowners facing shoreline erosion issues can use this information to create effective stabilization protocols that preserve shorelines while conserving native intertidal habitats.

Air–Sea $$\mathrm{CO}_{2}$$ CO 2 Gas Transfer Velocity in a Shallow Estuary

The air–sea transfer velocity of \(\mathrm{CO}_{2}\, (k_{\mathrm{CO}_{2}})\) was investigated in a shallow estuary in March to July 2012, using eddy-covariance measurements of \(\mathrm{CO}_{2}\) fluxes and measured air–sea \(\mathrm{CO}_{2}\) partial-pressure differences. A data evaluation method that eliminates data by nine rejection criteria in order to heighten parametrization certainty is proposed. We tested the data evaluation method by comparing two datasets: one derived using quality criteria related solely to the eddy-covariance method, and the other derived using quality criteria based on both eddy-covariance and cospectral peak methods. The best parametrization of transfer velocity normalized to a Schmidt number of 600 \((k_{600})\) was determined to be: \(k_{600} = 0.3\,{U_{10}}^{2.5}\) where \(U_{10}\) is the wind speed in m \(\mathrm{s}^{-1}\) at 10 m; \(k_{600}\) is based on \(\mathrm{CO}_{2}\) fluxes calculated by the eddy-covariance method and including the cospectral peak method criteria. At low wind speeds, the transfer velocity in the shallow water estuary was lower than in other coastal waters, possibly a symptom of low tidal amplitude leading to low intensity water turbulence. High transfer velocities were recorded above wind speeds of 5 m \(\mathrm{s}^{-1}\), believed to be caused by early-breaking waves and the large fetch (6.5 km) of the estuary. These findings indicate that turbulence in both air and water influences the transfer velocity.

Patterns of the growth of soft-shell clam Mya arenaria L. (Bivalvia) in shallow water estuaries of the southern Baltic Sea

We explored the shell shape and growth performance of the soft-shell clam Mya arenaria L. in two shallow brackish water estuaries of the southern Baltic Sea – Darss-Zingst and Ruegen lagoons. Observed clams ranged from 2 to 50.1mm in length with detected age up to 6 years old. The growth patterns of the clams were analyzed using the von Bertalanffy growth function (VBGF). An isometric relationship was found between shell length and shell height or shell thickness. Asymptotic length and weight were predicted according to von Bertalanffy equation as L∞=82.75mm and W∞=10.9g. The relationship of wet weight to length was allometric, with exponent b=3.09. Observed shell lengths were close to values predicted by the model. Our study distinguished patterns of the molluscan growth in estuarine transitional environment of the southern Baltic Sea in comparison with other coastal habitats with pronounced spatial environmental heterogeneity.