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 Showing 1 - 77 of 77 Journals sorted by number of followers Deep Sea Research Part II: Topical Studies in Oceanography       (Followers: 29) Deep Sea Research Part I : Oceanographic Research Papers       (Followers: 23) Estuaries and Coasts       (Followers: 23) Limnology and Oceanography       (Followers: 22) Progress in Oceanography       (Followers: 21) Journal of Marine Biology & Oceanography       (Followers: 19) New Zealand Journal of Marine and Freshwater Research       (Followers: 18) Journal of Physical Oceanography       (Followers: 18) Frontiers in Marine Science       (Followers: 17) Journal of Marine Sciences       (Followers: 17) Coastal Engineering       (Followers: 15) Advances in Oceanography and Limnology       (Followers: 15) Journal of Oceanography       (Followers: 14) Maritime Studies       (Followers: 13) International Journal of Oceanography       (Followers: 12) Advances in Statistical Climatology, Meteorology and Oceanography       (Followers: 11) Atmospheric and Oceanic Science Letters       (Followers: 10) Bulletin of Marine Science       (Followers: 9) Fisheries Oceanography       (Followers: 8) Journal of Oceanography and Marine Science       (Followers: 7) Open Journal of Marine Science       (Followers: 6) Limnology and Oceanography: Methods       (Followers: 6) Journal of Operational Oceanography       (Followers: 6) Physical Oceanography       (Followers: 6) Paleoceanography and Paleoclimatology       (Followers: 5) Marine Science       (Followers: 5) Limnology and Oceanography: Fluids and Environments       (Followers: 5) Ocean Yearbook Online       (Followers: 4) Journal of Oceanology and Limnology       (Followers: 4) Limnology and Oceanography Letters       (Followers: 4) Journal of Marine Science and Engineering       (Followers: 4) African Journal of Marine Science       (Followers: 4) Oceanology       (Followers: 3) Journal of Aquatic Sciences       (Followers: 3) Limnology and Oceanography e-Lectures       (Followers: 3) Journal of Coastal Development       (Followers: 3) Ciencias Marinas       (Followers: 3) Journal of Marine Science and Application       (Followers: 3) Journal of Ocean Engineering and Marine Energy       (Followers: 3) Tropical Oceanography       (Followers: 2) Indian Journal of Geo-Marine Sciences       (Followers: 2) Mediterranean Marine Science       (Followers: 2) Regional Studies in Marine Science       (Followers: 2) Annals of Marine Science       (Followers: 2) Limnology and Oceanography: Bulletin       (Followers: 2) Annals of Limnology and Oceanography       (Followers: 2) Development and Applications of Oceanic Engineering       (Followers: 2) Journal of Ocean Engineering and Technology       (Followers: 1) Ocean Life       (Followers: 1) Marine Systems & Ocean Technology       (Followers: 1) Journal of Ocean University of China (English Edition)       (Followers: 1) Marine Life Science & Technology       (Followers: 1) Journal of Ocean Engineering and Science       (Followers: 1) Coastal Engineering Proceedings : Proceedings of the International Conference on Coastal Engineering       (Followers: 1) Marine Technology Society Journal       (Followers: 1) Scientia Marina       (Followers: 1) Western Indian Ocean Journal of Marine Science       (Followers: 1) Asian Journal of Fisheries and Aquatic Research Thalassas : An International Journal of Marine Sciences Oceans Aquatic Research Jurnal Kelautan Tropis Acta Aquatica : Aquatic Sciences Journal Depik Jurnal Ilmu-Ilmu Perairan, Pesisir dan Perikanan Journal of Agricultural and Marine Sciences Turkish Journal of Maritime and Marine Sciences Arquivos de Ciências do Mar Scientific Drilling Jurnal Kelautan : Indonesian Journal of Marine Science and Technology Oceanologia Revista de Gestão Costeira Integrada Revista Ciencias Marinas y Costeras Egyptian Journal of Aquatic Research China Ocean Engineering Revista de Biología Marina y Oceanografía Latin American Journal of Aquatic Research Acta Oceanologica Sinica
Similar Journals
 Estuaries and CoastsJournal Prestige (SJR): 1.187 Citation Impact (citeScore): 2Number of Followers: 23      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1559-2723 - ISSN (Online) 1559-2731 Published by Springer-Verlag  [2467 journals]
• Insights into Salt Marsh Plant Community Distributions Through Computer
Vision and Structural Equation Modeling

Abstract: Abstract Community structure and dynamics are influenced by numerous abiotic and biotic factors requiring large datasets to disentangle, which are often difficult to obtain over the spatiotemporal scales necessary for meaningful analysis. The approach outlined here illustrates one potential solution to this problem by leveraging computer vision methods to gain accurate, in-depth community data from ~ 10,000 photographs of salt marsh plants across an elevation gradient at Sapelo Island, GA, USA. A convolutional neural network (ResNext101) trained to detect the 6 dominant plant species achieved high accuracy for all species, allowing mapping of high-marsh plant communities over gradients in elevation and pore-water salinity. To statistically analyze the high-resolution mapping data, we constructed a structural equations model using the generated data as informed by prevailing ecological theory for salt marshes in the Southeastern United States. Model fit to data was strong, with R2 values for five of six plant species > 0.7. The distribution of the rare understory perennial Limonium carolinianum, however, was not accurately predicted by the model. Modeled effects of abiotic factors elevation and soil salinity were commensurate with the literature. Biotic interactions also largely conformed to ecological understanding of Southeastern marshes, but a potentially novel positive interaction between Borrichia frutescens and Batis maritima was observed. Overall, this approach shows promise as a method of efficiently generating and statistically analyzing community data for sessile species at scales not previously possible. This study contributes to a growing body of work developing integrated computer vision and big data techniques for ecological field work.
PubDate: 2022-12-05

• Spatial Variation in Nursery Habitat Use by Juvenile Blue Crabs in a
Shallow, Wind-Driven Estuary

Abstract: Abstract Nursery habitats promote the survival of juveniles to the adult population and are often targeted by conservation policies and restoration practices. Managers must choose where to focus limited resources, which is complicated when juveniles utilize multiple habitats. This is particularly applicable to the blue crab (Callinectes sapidus) population in North Carolina, USA, which uses three main habitats, low salinity ephemeral Ruppia maritima seagrass beds, high salinity mixed-species seagrass beds, and shallow marsh detrital habitat (SDH). Spatial variation in early juvenile blue crab density and size-class of blue crab instars (2.2–20 mm) was quantified within the Albemarle-Pamlico estuarine system (APES) together with potential explanatory variables such as habitat structural complexity and proximity to inlets, potentially driving spatial variation in crab density and size. Despite being 25–40 km from oceanic sources of megalopae, juvenile crab density was nearly four times greater in ephemeral R. maritima habitat on the western shore of the APES than adjacent SDH or mixed-species seagrass beds located near inlet sources. Increased crab density in western habitats may be a result of cross-sound transport being hurricane-driven as opposed to secondary density-dependent distribution resulting in increased recruitment to western habitats. Local-scale factors also affected crab distribution patterns. For example, mean crab density in mixed-species seagrass beds along the eastern shore decreased by approximately 87% over a distance of 26.6 km from inlet sources of megalopae. Mean crab density in western R. maritima beds increased tenfold between locations with the lowest shoot density (~ 14,000 shoots m−2) to that with the highest (~ 54,000 shoots m−2). This study highlights how regional postlarval dispersal patterns and local-scale factors affect nursery habitat use by blue crabs when multiple habitats are present in a seascape.
PubDate: 2022-12-02

• Within-marsh and Landscape Features Structure Ribbed Mussel Distribution
in Georgia, USA, Marshes

Abstract: Abstract Ribbed mussels, Geukensia demissa, are marsh fauna that are used in coastal management and restoration due to the ecosystem services they provide. Ribbed mussel restoration efforts may be improved with a greater understanding of the environmental drivers of ribbed mussel distribution at multiple spatial scales to predict areas where restoration could be successful. This study sought to estimate the effects of within-marsh (4 m) and landscape (500 m) factors on ribbed mussel distribution. Ribbed mussel densities were surveyed at 11 sites along the coast of Georgia, USA, and overlaid with spatial data for within-marsh factors (elevation, distance to marsh features, slope) as well as landscape factors (percent cover by subtidal creek, forest, and development within a 500-m radius). The distribution model was then validated using three previously unsurveyed marshes and explained 55% of the variance in ribbed mussel abundance. Ribbed mussel abundances and occupancy were most sensitive to changes in within-marsh factors (elevation and distance to subtidal creeks, bodies of water inundated during the full tidal cycle) but were also sensitive to landscape features (percent landcover of forests and development). The highest ribbed mussel densities were found in mid-elevation areas (~ 0.7 m NAVD88), far from subtidal creeks, and in marshes surrounded with forest and development. These results contrast with distributions in the northeastern USA, where ribbed mussels are distributed along subtidal creek banks. This work suggests that restoration may be most effective when focused on appropriate elevations and at locations away from the marsh-creek ecotone.
PubDate: 2022-12-01

• Whole-Ecosystem Experiment Illustrates Short Timescale Hydrodynamic,
Light, and Nutrient Control of Primary Production in a Terminal Slough

Abstract: Abstract Estuaries are among the most productive of aquatic ecosystems. Yet the collective understanding of patterns and drivers of primary production in estuaries is incomplete, in part due to complex hydrodynamics and multiple controlling factors that vary at a range of temporal and spatial scales. A whole-ecosystem experiment was conducted in a deep, pelagically dominated terminal channel of the Sacramento-San Joaquin Delta (California, USA) that seasonally appears to become nitrogen limited, to test whether adding calcium nitrate would stimulate primary productivity or increase phytoplankton density. Production did not respond consistently to fertilization, in part because nitrate and phytoplankton were dispersed away from the manipulated area within 1–3 days. Temporal and spatial patterns of gross primary production were more strongly related to stratification and light availability (i.e., turbidity) than nitrogen, highlighting the role of hydrodynamics in regulating system production. Similarly, chlorophyll was positively related not only to stratification but also to nitrogen—with a positive interaction—suggesting stratification may trigger nutrient limitation. The average rate of primary production (4.3 g O2 m−2 d−1), metabolic N demand (0.023 mg N L−1 d−1), and ambient dissolved inorganic nitrogen concentration (0.03 mg N L−1) indicate that nitrogen can become limiting in time and space, especially during episodic stratification events when phytoplankton are isolated within the photic zone, or farther upstream where water clarity increases, dispersive flux decreases, and stratification is stronger and more frequent. The role of hydrodynamics in organizing habitat connectivity and regulating physical and chemical processes at multiple temporal and spatial scales is critical for determining resource availability and evaluating biogeochemical processes in estuaries.
PubDate: 2022-12-01

• Benthic Foraminiferal Response to Trace Elements in a Tropical Mesotidal
Brazilian Estuary

Abstract: Abstract Living benthic foraminifera have been widely used as ecological indicators in coastal ecosystems. There is, however, a lack of studies on their response to trace element pollution in tropical estuarine systems. Here we analyze the living assemblages of benthic foraminifera, collected in 2016, in the Cachoeira River Estuary (CRE) in northeastern Brazil, to understand their response to natural and anthropogenic stressors, including trace element pollution. Some species were good bioindicators of specific environmental conditions, such as the agglutinant Paratrochammina clossi which preferred mangrove areas and anoxic conditions. In addition, the calcareous Ammonia tepida and Cribroelphidium excavatum, dominant within the whole system disregarding organic or trace element pollution, seem to resist even in the areas most polluted by trace elements. Interestingly, C. excavatum showed a particular positive relationship with trace element pollution (specifically by Cu and Pb), outnumbering the opportunistic A. tepida in the areas with higher pollution of these metals. However, for other species, it is still difficult to constrain to which parameters they respond (i.e., Haynesina germanica and Elphidium gunteri, which in the present study seem to respond to natural conditions, whereas in the literature they are regarded as indicators of trace element and organic pollution, respectively). Therefore, our findings shed light on the response of benthic foraminiferal species in a highly polluted and highly mixed tropical estuarine system and highlight the need to understand the complexity of these environments when applying foraminiferal biological indexes to avoid imprecise conclusions.
PubDate: 2022-12-01

• Too Much Freshwater, Not Enough, or Just Right' Long-Term Trawl
Monitoring Demonstrates the Impact of Canals that Altered Freshwater Flow
to Three Bays in SW Florida

Abstract: Abstract Understanding the impact of anthropogenically altering freshwater flow to estuaries is a growing information need for coastal managers. Due to differences in watershed development, drainage canals, and water control structures, the Ten Thousand Islands area of southwest Florida provides an ecosystem-scale opportunity to investigate the influence of both more, and less, freshwater flow to coastal bays compared to locations with more natural hydrology. Bottom trawl and water quality data spanning 20 years were used to investigate how environmental and hydrological differences among three bays affect community structure of small estuarine fishes. Relationships between fish community structure and salinity and temperature variables were evaluated over timescales from 1 day to 3 months prior to each trawl. Longer-term aspects of temperature (i.e., 2–3 months) exhibited the highest correlations in all bays, suggesting that spawning cycles are the main cause of seasonal changes in fish communities, rather than differences in freshwater flow. Despite major contrasts in watershed manipulation and the seasonal salinity of one bay being much less than the others, the bays differed primarily based on relative abundances of more common species rather than due to unique suites of species being present. Truly freshwater conditions were never detected, and high salinity conditions were experienced in all bays during dry seasons. This likely prevents a community shift to freshwater species. The range in flow characteristics among bays and general similarity in fish communities suggest that conditions will remain within the tolerance of most fishes in all three bays following restoration to more saline conditions.
PubDate: 2022-12-01

• Disentangling the Drivers of Benthic Oxygen and Dissolved Carbon Fluxes in
the Coastal Zone of the Southern Baltic Sea

Abstract: Abstract Benthic fluxes of oxygen and carbon in coastal zones are poorly resolved in mechanistic models due to the lack of understanding of the diverse interactions among the physical, chemical, and biological drivers of biogeochemical fluxes. To inform modelling efforts we used ex-situ incubation experiments to identify spatial and seasonal patterns of oxygen and dissolved inorganic and organic carbon (DIC and DOC) fluxes in the coastal southern Baltic Sea. We used boosted regression trees to identify important drivers of the studied fluxes. Our results demonstrate that benthic communities, in addition to sediment parameters, played a dominant role in shaping oxygen and DIC fluxes, while neither benthic community, environment, season, nor sampling location could account for the highly variable DOC fluxes. DIC fluxes were partly decoupled from oxygen fluxes, since carbonate dissolution, anaerobic respiration, and submarine groundwater discharge affected DIC fluxes in the study region. Boosted regression trees proved to be a useful tool to study drivers of biogeochemical fluxes as it allowed to identify non-linear effects of biological and environmental variables on benthic fluxes.
PubDate: 2022-12-01

• Kelp Forest Drag Coefficients Derived from Tidal Flow Data

Abstract: Abstract We present an approach for estimating drag coefficients for depth-averaged tidal flows that uses the ratio of observed RMS velocities to the RMS velocities that would be observed without bottom friction. We find that this ratio, R, depends on a single non-dimensional number, $$P={C}_{D}C{\eta }_{0}/\omega {H}^{2}$$ , where CD is the drag coefficient, and C is the phase speed of a tidal wave with amplitude $${\eta }_{0}$$ and frequency $$\omega$$ , in water of depth h. The function R(P) can be inverted to solve for CD using measured values of R. Taking advantage of a unique multi-year record of tidal flows on Isla Nativdad, Baja California, Mexico, during which time the kelp forest there varied between non-existent and dense, we use this method to quantify the effect of kelp biomass on drag. This analysis shows that a maximum value of CD ≈ 0.04 is reached for relatively low values of kelp biomass, which may be an effect of sheltering (reductions in the velocity creating drag due to the close proximity of bundles of kelp stipes). However, values as large as 0.015 were observed when the water column experienced strong secondary flows in the presence of strong density stratification. Given that the long-term measurements were made near a coastal headland, we argue that this may reflect variations in secondary flow strength due to stratification. Lastly, our measurements show little evidence of enhancement of drag by surface waves.
PubDate: 2022-12-01

• Characteristics of Surface Currents in a Shallow Lagoon–Inlet–Coastal
Ocean System Revealed by Surface Drifter Observations

Abstract: Abstract The circulation in a shallow lagoon–inlet–coastal ocean system is significant to material transports (e.g., debris, pollutants, and larvae). To study surface flows in this system, we deployed 35 surface drifters at various tidal phases and wind conditions during 2017 and 2018 in the Maryland Coastal Bays system (MCBs). Given that winds and tides are two important drivers of estuarine and coastal circulation, their influences on surface drifter trajectories were analyzed. Observations indicate that surface drifters exit (enter) the lagoon mostly during ebb (flood) currents, and clockwise circular movements at a length scale of 1.5 km formed at the outer edge of Ocean City Inlet (OCI). Under weak wind conditions, tides are primarily responsible for drifter movements near OCI, whereas both the long-fetch winds and tides are important near the relatively larger Chincoteague Inlet and backbays. Under strong wind conditions, surface drifter movements generally follow wind directions. In the shallow lagoonal system, relative effects of winds on surface drifters gradually become stronger in the regions further away from the adjacent inlet as tides are weaker. Further investigations indicate that the fastest and slowest surface drifters are near the small OCI and backbays with the weakened tides, respectively. The direct surface drifter observations that cover a wide spatial range and long time series can provide strong support to surface current simulations. Enhanced understanding of coastal physical oceanography in the MCBs can be beneficial to similar systems and coastal ocean communities.
PubDate: 2022-12-01

• Distribution and Morphology of Littoraria irrorata in Mesohaline Tidal
Marshes Dominated by Juncus roemerianus

Abstract: Abstract Marsh periwinkle snails (Littoraria irrorata) are common in salt marshes of the Atlantic and Gulf of Mexico coast and often occupy important ecological roles. Much of the published research examining the abundance and role of this species has been conducted in marshes dominated by smooth cordgrass (Spartina alterniflora). We investigated the distribution and morphology of L. irrorata in marshes dominated by black needlerush (Juncus roemerianus) an important marsh species that commonly forms monotypic conditions in more mesohaline conditions. Eight marshes along the coastal border of Alabama and west Florida, USA, were sampled for L. irrorata and other environmental data (plant density and biomass) at four different proximities to the marsh-bay edge. We also examined L. irrorata abundance, shell size, and biomass across a salinity gradient (quantified using a salinity regime index). We found that (1) abundance of L. irrorata in J. roemerianus-dominated marshes (1.0 ± 1.0 to 25.3 ± 12.6 snails m−2) were within the lower range of snail densities reported for S. alterniflora-dominated marshes elsewhere, (2) most L. irrorata were detected along the 10-m waterward edge of the marsh, and (3) considering snails at the waterward edge, a positive relationship (r2 = 0.53, p = 0.04) was detected between marsh salinity and snail density along with a negative relationship (r2 = 0.86, p < 0.01) between marsh salinity and mean snail shell length. Mechanisms associated with L. irrorata abundance and morphology are unclear but likely relate to various aspects of salinity and tidal connectivity. These results suggest that mesohaline J. roemerianus marshes may be marginal in terms of L. irrorata habitat; however, further research is encouraged.
PubDate: 2022-12-01

• Impact of Colonizer Copepods on Zooplankton Structure and Diversity in
Contrasting Estuaries

Abstract: Abstract The impact of the occurrence of the non-indigenous species (NIS) Acartia tonsa, Oithona davisae, and Pseudodiaptomus marinus and of the range-expanding copepods Acartia bifilosa and Calanipeda aquaedulcis on the structure and diversity of zooplankton communities was analyzed using 18 years (1998–2015) time series from the contrasting estuaries of Bilbao and Urdaibai (Basque coast, Bay of Biscay). Changes in the structure of communities were assessed by using multivariate analyses of taxa abundances and changes in diversity by using descriptors of alpha, beta, and gamma diversity. The most evident changes occurred at the upper reaches of the estuary of Bilbao, where an abundant and less diverse brackish community, dominated by the NIS, A. tonsa and O. davisae, succeeded a low abundance and more diverse community of neritic origin. The later establishment of C. aquaedulcis was linked to further changes in the structure of the community and a progressive increase in diversity. The seasonal pattern of diversity at the inner estuary and the beta diversity in the estuary were also significantly affected by the arrival of the NIS and C. aquaedulcis. In contrast, the original low diversity brackish community of the estuary of Urdaibai, clearly dominated by A. bifilosa, was far less affected by the arrival of the same copepod NIS, and A. bifilosa remained as the species best related to the changes in zooplankton structure and diversity in the brackish habitats of the estuary.
PubDate: 2022-12-01

• Statistical Detection of Spatio-Temporal Patterns in the Salinity Field
Within an Inter-Tidal Basin

Abstract: Abstract Salinity is a key factor affecting biological processes and biodiversity in estuarine systems. This study investigates temporal and spatial changes in salinity at a basin-wide scale for 2005–2015 in the Dutch Wadden Sea. Scan statistics is applied to track salinity variations systematically and to detect potential clusters, i.e., estuarine regions marked by anomalous high-salinity (or low-salinity) values in a certain period (i.e., strong deviations from the expected value in a statistical sense). Clusters’ statistical significance has been assessed via Monte Carlo simulations. Particular attention is devoted to event-driven spatial and temporal patterns characterized by extreme salinity values since these episodes dramatically increase stress levels on organisms living in intertidal areas. Periodic components in the modeled salinity time series are identified using wavelet analysis and eventually removed from the signal before performing scan statistics. Wavelet analysis suggests that tides are the chief agent controlling salinity fluctuations in the system at within-day time scales, whereas no dominant periodicities were detected at longer time scales. Scan statistics reveal long-lasting clusters next to the main freshwater outlets and within the areas characterized by low water exchanges. In contrast, active regions of the estuary can efficiently counteract extreme events and quickly recover their pre-perturbation conditions. Finally, by analyzing the freshwater dispersal in the system, it is found that clusters’ occurrence is related to episodic events characterized by extreme conditions in the southwesterly wind and freshwater discharge. This research demonstrates that scan statistics can be used as a powerful tool for spatiotemporal analyses of marine systems and for identifying data-clustering that may be indicative of emerging environmental hazards (e.g., due to climate change).
PubDate: 2022-12-01

• Tidal Freshwater Zones Modify the Forms and Timing of Nitrogen Export from
Rivers to Estuaries

Abstract: Abstract It is widely recognized that nitrogen (N) inputs from watersheds to estuaries are modified during transport through river networks, but changes within tidal freshwater zones (TFZs) have been largely overlooked. This paper sheds new light on the role that TFZs play in modifying the timing and forms of N inputs to estuaries by (1) characterizing spatial and temporal variability of N concentrations and forms in the TFZs of the Mission and Aransas rivers, Texas, USA, and (2) examining seasonal fluxes of N into and out of the Aransas River TFZ. Median concentrations of dissolved inorganic N (DIN) were lower in the TFZs than in upstream non-tidal river reaches and exhibited spatial gradients linked to locations of major N inputs. These spatial patterns were stronger during winter than summer. The forms of N also changed substantially, with DIN changing to organic N (primarily phytoplankton) within the TFZs. Discharge and N flux comparisons for the Aransas River TFZ demonstrated that secular tidal patterns modulate the timing of N export during baseflow conditions: N export far exceeded input during winter, whereas export and input were relatively balanced during summer. While more data are needed to build an annual N budget, our results show that TFZ can change the timing and form of N export immediately upstream of estuaries.
PubDate: 2022-12-01

• Modelling the Spatial Distribution of Oyster (Crassostrea virginica)
Biodeposits Settling from Suspended Aquaculture

Abstract: Abstract Oysters in suspended aquaculture filter out particulates from the water column and release pseudofeces and feces (collectively called biodeposits) back to the water column. These biodeposits consist of dense assemblages of labile organic matter that quickly settle to the sediment surface. To properly quantify the environmental effects of biodeposition from suspended aquaculture, it is necessary to determine where the biodeposits settle. An analytical/numerical model was developed for suspended aquaculture systems to predict the spatial distribution of biodeposits; input parameters include water depth, tidal elevation, biodeposit settling rate, and wind and tidally driven current velocity. The biodeposit model was validated in three shallow Cape Cod, Massachusetts, estuaries characterized by low-energy hydrodynamics. For each site, model-predicted carbon deposition was regressed against measured carbon remineralization (determined from sediment oxygen uptake) obtained from intact sediment cores collected along a gradient of predicted carbon deposition. Results showed that in summer, nearly all carbon deposited was remineralized but that the fraction of deposited carbon that is remineralized decreases considerably with declining temperatures in the fall. The simple analytical/numerical model developed and validated in this study provides a tool for commercial oyster growers and environmental managers to assess the effect of organic matter deposition by suspended oyster aquaculture over the growing season. This approach can be applied in shallow depositional coastal systems.
PubDate: 2022-12-01

• Transport and Fate of Particulate Organic Nitrogen in Chesapeake Bay: a
Numerical Study

Abstract: Abstract In Chesapeake Bay, substantial quantities of organic matter are produced during the spring bloom, which contributes to severe chronic bottom oxygen depletion during the summertime. However, the details of this transport in the estuarine system under realistic forcing is still unclear. In this research, a three-dimensional coupled physical-biogeochemical model has been used to investigate the production, transport and fate of organic matter in Chesapeake Bay. Analysis of a control volume in the deep channel reveals that the sinking flux of fast-sinking particulate organic nitrogen (PON) into the deep channel is comparable to the horizontal advective transport in contributing in the accumulation of PON in the thalweg, both on the scale of 106 mol nitrogen/day during springtime. The model analysis also reveals a pronounced east to west transport of PON during the springtime and a tendency to export mass from the eastern shore to the deep channel and from the deep channel to the western shore of the Chesapeake Bay, and also a convergence of mass transport on the western shore. This transport pattern is consistent with the springtime lateral estuarine circulation in Chesapeake Bay that arises due to the asymmetry of the flood-neap tidal cycle. In addition, the model reveals that seasonal variations in wind alter the magnitude and distribution of organic matter flux in the along channel and cross channel direction, with northerly winds during the springtime favoring more northward organic matter transport and more organic matter accumulation in the deep channel. Numerical experiments suggest that with enhanced northerly winds, bottom PON accumulation increases to as much as 3.25 × 106 mol nitrogen/day in April. However, the lateral net flux direction and pattern remain the same.
PubDate: 2022-12-01

• Maternal Nutrient History Enhances Black Mangrove (Avicennia germinans)
Seedling Growth After Propagules Experience a Hard Freeze

Abstract: Abstract Climate change is a primary driver of tropical mangroves colonizing temperate salt marshes in the Gulf of Mexico. Studies indicate that threshold temperatures of adult and sapling Avicennia germinans survival range from −7 to −10 °C and survival can depend on life history stage during a freeze event. We performed a growth chamber study to explore responses to varying freezing temperature regimes when produced at two different latitudes with varying salinity and nutrient conditions. Propagules were collected from Corpus Christi and South Padre Island, Texas. In Corpus Christi Bay, propagules were harvested from fertilized maternal shrubs (nitrogen, phosphorus, and controls) in an ongoing fertilization experiment (2017 to present). A 2-h hard freeze treatment (−8 °C), resulted in 20% survival across latitude and nutrient treatments. The lower latitude propagules, which were harvested from the hypersaline South Padre Island A. germinans, had higher survival rates after –2 °C exposure, grew significantly taller as seedlings over 20 weeks, and produced more leaves after −8 °C exposure. Propagules from nitrogen-treated shrubs grew taller following −2 °C exposure. In all treatments, propagule weight was a significant covariate predictor of seedling height and leaf production. Avicennia germinans populations may not be decimated by a single −8 °C freeze, and populations could possibly experience rapid recruitment from surviving propagules after a freeze, leading to local adaptation. Growth benefits from fertilized parent plants indicate that propagules from high nutrient areas may be “hotspots” of future A. germinans expansion.
PubDate: 2022-12-01

• Microplankton Interactions with Decadal-Scale Nutrient Enrichment in a
Deep Estuary, with Implications for Eutrophication—Related Ecosystem
Stressors

Abstract: Abstract Long-term (decadal) records of microplankton provide insights into how lower trophic levels of coastal ecosystems respond to nutrient enrichment, over and above shorter-term variability. We used a 15-year seasonal census in the Firth of Thames, a deep, nutrient-enriched estuary in northeastern Aotearoa/New Zealand, to determine microplankton responses to enrichment. Kendall trend analyses showed that dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen were enriched by 99% and 34%, respectively, over 15 years, while phosphorus changed little. Larger phytoplankton (> 2 µm) increased by 46%, including 57% increases by diatoms (mainly large centrics with 93% increase) and nanoflagellates (151% increase). Dinoflagellates decreased by 46%, such that the community shifted from dinoflagellate to diatom/nanoflagellate dominance. Within phytoplankton ≤ 2 µm, picoprokaryotes increased by 369%, while picoeukaryotes changed little. Among microheterotrophs (< 200 µm), bacteria increased by 89%, and small oligotrichs increased by 53%. Trend analyses and multivariate general additive modelling showed that microplankton biomass responded primarily to increased DIN over the 15-year period and secondarily to stratification variation at shorter time scales. The changed biomasses and community composition are explained as responses to increased N:P and food-web interactions. Deleterious changes included increased toxic Pseudo-nitzschia abundance and potentially reduced nutritional quality of the phytoplankton community for grazers. The increased N and larger diatoms indicated potential for increased deposition to sediments, possibly explaining previous observations of lowered denitrification in the Firth during the time series period. The results indicated a continuation of enrichment the Firth has received over decades, with implications for expression of ecosystem stressors of acidification and hypoxia.
PubDate: 2022-12-01

• Seasonal Dynamics of Faunal Diversity and Population Ecology in an
Estuarine Seagrass Bed

Abstract: Abstract Biodiversity is important for communities to be resilient to a changing world, but patterns of diversity fluctuate naturally over time. Understanding these shifts — and the species driving community dynamics — is crucial for informing future ecological research and conservation management plans. We investigated the impacts of seasonality, small-scale changes in seagrass cover, and small-scale spatial location on the epifaunal communities occupying a temperate seagrass bed in the South Island of New Zealand. By sampling epifaunal communities using a fine-mesh push net two to three times per season for 1 year, and using a combination of multivariate and hierarchical diversity analyses, we discovered that season, seagrass cover, and the location within the bay, and their interactions, explained 88.5% of the variation in community composition. Community composition and abundances, but not numbers, of species changed over seasons. The most common taxa were commercially important Caridean shrimp and juvenile flounder (Rhombosolea spp.), and both decreased in abundance in summer (shrimp: 1.40/m2 in winter to 0.80/m2 in summer; flounder: 0.15/m2 in winter to 0.01/m2 in summer). Other commercially important species were captured as juveniles, including blue cod (Parapercis colias), kahawai (Arripis trutta), and whitebait (Galaxias spp.). The only adult fish captured in the study were two pipefish species (Stigmatopora nigra and Leptonotus elevatus), which had distinctly seasonal breeding patterns, with reproductively active adults most likely to be found in the spring and fall. Our study highlights the importance of estimating biodiversity parameters based on sampling throughout the year, as some species will be overlooked. We demonstrate that the temperate estuarine seagrass-affiliated animal communities differ in response to season and fine-scale local environments, causing fluctuations in biodiversity throughout the year.
PubDate: 2022-12-01

• Can Coastal Habitats Rise to the Challenge' Resilience of Estuarine
Habitats, Carbon Accumulation, and Economic Value to Sea-Level Rise in a
Puget Sound Estuary

Abstract: Abstract Sea-level rise (SLR) and obstructions to sediment delivery pose challenges to the persistence of estuarine habitats and the ecosystem services they provide. Restoration actions and sediment management strategies may help mitigate such challenges by encouraging the vertical accretion of sediment in and horizontal migration of tidal forests and marshes. We used a process-based soil accretion model (Coastal Wetland Equilibrium Model) combined with a habitat classification model (MOSAICS) to estimate the effects of SLR, suspended sediment, and inland habitat migration on estuarine habitats, soil carbon accumulation, and economic value of climate change mitigation of carbon accumulation (social cost of carbon dioxide) in a macrotidal estuary in the northwest USA over 100 years (2011 to 2110). Under present-day sediment levels, we projected that after 100 years, most high salt marsh would remain with < 100 cm SLR, but substantial area converted to transitional (low) salt marsh and mudflat with ≥ 100 cm SLR. Increasing sediment availability increased the projected resilience of transitional salt marsh to SLR but did not prevent declines in high marsh area. Projected total carbon accumulation plateaued or declined with ≥ 100 cm SLR, yet the economic value of carbon accumulation continued to rise over time, suggesting that the value of this ecosystem service was resilient to SLR. Doubling or tripling sediment availability increased projected carbon accumulation up to 7.69 and 14.2 kg m−2 and increased total economic value up to $373,000 and$710,000, respectively. Allowing marsh migration supported conversion of upland to freshwater marsh, with slight increases in carbon accumulation. These results inform climate adaptation planning for wetland managers seeking to understand the resilience of estuarine habitats and ecosystem services to SLR under multiple management strategies.
PubDate: 2022-12-01

• Shoreline Variability of a Bay Beach: The Case of Apam Beach, Ghana

Abstract: Abstract The Ghanaian coast is eroding at a significant rate. A comprehensive understanding of the dynamics of a beach is vital for its management. Two decades of shoreline and a short-term sediment volume change data on the Apam Beach were analysed from freely available satellite and drone images, respectively. After assessing its long-term shoreline changes, it was revealed that the beach is gradually accreting at a mean rate of + 0.60 m/year. This, coupled with a net sediment deposition of + 3725.22 m3 within 5 months, could be attributed to fluvial discharges and the topography of the beach. The Parabolic Bay Shape Equation (PBSE) further characterised this beach as being in the dynamic equilibrium state. Thus, any disruption to the existing sediment transport mechanism will lead to a chronic erosion problem. To avert this, it is proposed that all future developments on this beach should be thoroughly planned.
PubDate: 2022-12-01

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