Lagoon System Research Articles

The effect of fluvial avulsion on the Holocene chronostratigraphic record and the agricultural signal of the world's largest coastal lagoonal system

This study identified the occurrence of Holocene chronology hiatuses in the sedimentary record of the Patos-Mirim system caused by river avulsion processes, as well as evidence of sharp anthropogenic changes in the surrounding region of the lagoon water bodies. The presence of chronology hiatuses demonstrates the importance of considering the disturbance effect of paleo-drainage processes on the paleoenvironmental resolution and expression of the sedimentary record of such coastal plains. Anthropogenic activities especially those related to agriculture and forestry have increased significantly during the great acceleration, resulting in modifications of both the landscape and the environmental conditions of the lagoon bodies. Such impacts were clearly reflected in the sedimentary record where abrupt changes in palynological trends, sedimentary DNA, isotopic and granulometric analyses were inferred. The climatic conditions combined with regressive sea level can explain the chronology hiatuses. Pollen analyses demonstrated changes in the landscape, particularly indicated by the shift from Cyperaceae to Poaceae dominance after the 1960 CE. Therefore, all proxies together demonstrate the modification in the landscape and changes in the environment, clearly influenced by anthropogenic action from unsustainable agricultural practices.

Tremátodos y acantocéfalos asociados a mojarra amarilla (Caquetaia kraussii) en un sistema de laguna costera, San Onofre, Colombia

In Colombia, ichthyozoonoses caused by helminths are little studied and remain neglected by the public health sector, representing an interaction to be explored regarding biodiversity and health. Caquetia kraussi is a native fish of Colombia and Venezuela that is economically important due to its high consumption by local communities. This research records the fauna of parasitic helminths associated with C. kraussi in a coastal lagoon system in the Colombian Caribbean. Thirty-two specimens of C. kraussi were captured and inspected in February and December 2020, resulting in the collection of 242 helminths at the metacercariae stage and adults. Parasites included metacercaria of the trematodes Clinostomum sp., Austrodiplostomum sp., two forms of Posthodiplostomum and adults of Oligogonotylus andinus, and adults of the acanthocephalan Neoechinorhynchus sp. These results indicate that C. kraussii acts as a definitive host for O. andinus and Neoechinorhynchus sp., and as an intermediate host for Clinostomum sp., Posthodiplostomum spp. and Austrodiplostomum sp. This research reports for the second time a population of O. andinus in Colombia and the occurrence of a morphoespecies of the genus Neoechinorhynchus that could constitute a new record for Colombia. In addition to contributing to the knowledge of the diversity of fish-associated helminths, the results of this research will make it possible to generate recommendations for the management and control of helminthiasis in artificial fish farming systems that are supplied by natural tributaries, and favor the establishment of hosts and parasites.

Urbanization effects on growth and otolith asymmetry in Chrysichthys nigrodigitatus and Oreochromis niloticus within tropical coastal lagoon watersheds

In this study, we investigated the growth dynamics and otolith shape asymmetry of two fish species, Chrysichthys nigrodigitatus (CN) and Oreochromis niloticus (ON), within urbanized watersheds of the southern lagoon system, Nigeria. Using the von Bertalanffy growth model (VBGM), in addition to sediment metal concentration indices such as the average shale content, index of geoaccumulation (Igeo), contamination factor (CF), pollution load index (PLI), and potential ecological risk (PER) index, contamination levels were classified, and ecological risks were assessed. Notably, a lower growth potential (t0) was observed in CN at Ikorodu than at Epe, with similar trends for ON in the Epe during the dry season. Otolith asymmetry patterns, particularly in the CN at Ikorodu and ON in the Epe during the dry season, exhibited distinct ecological variations, indicating heightened stress levels at Ikorodu. Sediment analyses revealed moderate to strong contamination (Cd, Pb, Ni, and Cr) in both Lagos Lagoon (Ikorodu) and Epe Lagoon, with Ikorodu exhibiting notably high to moderate contamination levels according to the CF index. Elevated PLI values for Cd and Pb in Ikorodu, in addition to greater PER, indicated increased risk, with Cd posing a high risk (61.42%) and Pb posing a moderate risk (49.50%). Additionally, the reduced asymptotic length in the Epe during the dry season suggests that Chrysichthys nigrodigitatus is adaptable to seasonal variations, while divergent growth patterns in both areas indicate the existence of trade-off mechanisms in response to changing conditions. Habitat-specific otolith asymmetry and metal contamination underscore species adaptability, with wider stressor variability in Lagos than in Epe. Furthermore, multidimensional scaling analysis highlights the intricate relationship between otolith shape variables and environmental factors, emphasizing the need for tailored conservation efforts in urbanized watersheds.

Study on the Start-Up Phase of the Stabilization Lagoons System for Municipal Wastewater Treatment

Study on the Start-Up Phase of the Stabilization Lagoons System for Municipal Wastewater Treatment

Repeated Coseismic Uplift of Coastal Lagoons Above the Patton Bay Splay Fault System, Montague Island, Alaska, USA

AbstractCoseismic slip on the Patton Bay splay fault system during the 1964 Mw 9.2 Great Alaska Earthquake contributed to local tsunami generation and vertically uplifted shorelines as much as 11 m on Montague Island in Prince William Sound (PWS). Sudden uplift of 3.7–4.3 m caused coastal lagoons along the island's northwestern coast to gradually drain. The resulting change in depositional environment from marine lagoon to freshwater muskeg created a sharp, laterally continuous stratigraphic contact between silt and overlying peat. Here, we characterize the geomorphology, sedimentology, and diatom ecology across the 1964 earthquake contact and three similar prehistoric contacts within the stratigraphy of the Hidden Lagoons locality. We find that the contacts signal instances of abrupt coastal uplift that, within error, overlap the timing of independently constrained megathrust earthquakes in PWS—1964 Common Era, 760–870 yr BP, 2500–2700 yr BP, and 4120–4500 yr BP. Changes in fossil diatom assemblages across the inferred prehistoric earthquake contacts reflect ecological shifts consistent with repeated draining of a lagoon system caused by >3 m of coseismic uplift. Our observations provide evidence for four instances of combined megathrust‐splay fault ruptures that have occurred in the past ∼4,200 years in PWS. The possibility that 1964‐style combined megathrust‐splay fault ruptures may have repeated in the past warrants their consideration in future seismic and tsunami hazards assessments.

Foraminifera as indicators of environmental changes promoted by dredging in tidal channels from Maricá-Guarapina Lagoonal System, Rio de Janeiro, Brazil

To mitigate the anthropogenic impacts on the coastal lagoons, public managershave been implementing different approaches, such as dredging and opening channels to increase the circulation of the marine waters and improve the system's environmental quality. This study aims to investigate the effects of these approaches (opening and dredging of channels) in the Maricá-Guarapina Lagoonal System, using the relationship between foraminifera and environmental parameters before (2013) and after (2019) these interventions on the environment. After the interventions, data showed a significant increase in the marine influence on the lagoon system. The effects of seasonality could be identified by the reduction of sandy sediments related to the decrease in rainfall between the two analysed periods. The ecological indexes for foraminifera increased in 2019 due to the higher efficiency of water renewal in the lagoons. Ammonia tepida, Ammonia parkinsoniana and Elphidium excavatum were the most constant species in both sampling periods. Quinqueloculina seminulum was replaced by Ammotium morenoi and Ammotium cassis after the interventions as a result of changes in the distribution of muddy sediments in the lagoons. The Assemblage E. excavatum was correlated with higher salinity levels and showed an extension of its range within the lagoons. The same occurred with the Assemblage Paratrochammina guaratibaensis, which indicated high hydrodynamic. On the other hand, Assemblage A. tepida, related to the most impacted area, was distributed in all the innermost lagoons, and after the dredging its distribution was reduced.

Evaluation of some selected antibiotics and dyes removal by fungi isolated from wastewater sludge

In developing countries, stabilization ponds are the most common facilities wastewater treatment, where microbial consortia are the workhorse for removing organic contaminants. Fungi play an important role in the removal of organic matter. However, their efficiency in removing recalcitrant pollutants such as antibiotics and dyes still needs to be determined. The present work evaluates four fungal strains isolated from wastewater treatment lagoon systems (aerobic-anaerobic-anoxic) to remove persistent organic pollutants: Tilmicosin, Enrofloxacin, and Methylthionine chloride in Malt medium rich in carbon and in Mineral medium with only mineral nutrients. Fungi were isolated from sludge obtained from lagoons and identified based on their morphology. Removal assays were conducted in synthetic wastewater, with variations in operating conditions such as fungus type, temperature, and residence time. The quantification of contaminants was performed using UV-V spectrometry, and data on pH, conductivity, and spore concentration were obtained. The results were analyzed using R software, version 4.0.2. The results indicate that adsorption is the primary pathway in all cases. It was found that the greater the amount of fungal biomass produced during the test, the greater the absorption of the mode; that was the case with the Malt medium and dyes tests compared to Mineral medium and antibiotics tests. The studied fungi poorly removed antibiotics, around 20% in Malta medium and less than 10% in mineral medium, but are more capable of adsorbing Methylene blue, around 70% in Malta medium and less than 20% in the mineral medium. These results indicate natural fungi role in removing persistent organic pollutants (POPs). This shows that this type of plant needs the support of ternary treatments to eliminate POPs such as antibiotics. Limiting the discharge of this type of POPs is recommended as they could risk the biological remediation system’s health. Nevertheless, Fungal species from these lagoon systems can be used in dye removal processes.

Mangrove development on a remote volcanic island in the South Atlantic

Sueste Bay, in the Fernando de Noronha archipelago (FNA), contains the only mangrove area among the oceanic islands of the South Atlantic. This work aims to reconstruct this mangrove's evolution during the Holocene based on a morphostratigraphic study integrated with palynological and multi-elemental geochemical data, temporally calibrated with radiocarbon dating. The data obtained indicated that, around 8000 to 7000 cal yr BP, well-developed Rhizophora and Laguncularia mangroves established over altered rocks of the Quixaba (phonolites, lamprophyres, basanites, trachyandesites and basalts) and Remédios (basanites, melilite and melanophelinites) Formation, under rising relative sea level, about 2 to 3 m below present. This period was the last record of Rhizophora in the FNA. From 6000 to 3600 cal yr BP, the lagoon system was eroded and significantly retrograded, under rising RSL during at least part of time, leaving clay pebbles scattered in the lower/upper shoreface deposit as the only record of its reworking. This process limited mud/mixed flats near the mouth of the Maceió River. Under a relative stability of RSL from 3600 cal yr BP to the present, a progradation of coastal facies, including beach/foredunes ridges, occurred and allowed the development of the modern lagoon system over swales between aeolian sand ridges. Mangroves were only observed during modern times but in environmental conditions very different from those of the previous occurrence. Indeed, Laguncularia coexists with several invasive plants within the narrow mixed flats associated with a small and almost filled tidal creek, whose siltation may be a product of the artificial damming of the Maceió River to supply public water to the archipelago. This study highlights the complex interactions between natural processes, sea-level changes, and human activities in shaping the coastal evolution of the Fernando de Noronha archipelago over the Holocene.

Use of otolith microchemistry signatures to assess the habitat use of Centropomus undecimalis in lagoon systems of the southwest Atlantic

The common snook, Centropomus undecimalis, is a catadromous species that is economically important for the southwest Atlantic artisanal and recreational fisheries. Their complex movement patterns and habitat use preferences are not fully understood in the Brazilian Atlantic waters, raising some issues regarding the rational and sustainable management of the fisheries. The present study aimed to identify the habitat use by C. undecimalis individuals captured in four coastal lagoon systems in the Eastern Rio de Janeiro state, Brazil. Sixty individuals were collected in the lagoon systems of Itaipu, Maricá, Saquarema and Araruama, between November 2019 and March 2020. A selection of 15 individuals per site from the same age group (3 years old), following age estimation by counting the annual growth increments, were used. Elemental signatures of the otolith’s cores and edges were obtained using laser ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS). Data were analyzed using univariate and multivariate statistics to assess the degree of separation among individuals regarding the natal origin (otolith cores) and moment of capture (otolith edges) from the sampling sites. Elemental signatures exhibited distinct spatial patterns, driven by Ba/Ca, Li/Ca and Sr/Ca in the otolith cores and Ba/Ca, Li/Ca, Mn/Ca and Sr/Ca in the edges. A low reclassification was recorded for the otolith’s core (overall: 45%; by lagoon: 53% Saquarema, 53% Maricá, 47% Itaipu and 27% Araruama). However, a highest overall reclassification was observed for the otolith’s edge (overall: 65%; by lagoon: 73% Itaipu, 73% Saquarema, 60% Maricá, and 53% Araruama). Differences between otolith core and edge signatures within locations were detected for Ba/Ca, Cu/Ca, Li/Ca, Mn/Ca and Sr/Ca ratios. The results obtained indicate an ontogenetic habitat shift, with a similar natal origin of the individuals probably due to marine water influence, and discrimination of heterogeneous juvenile fish groups driven by distinct phenotypic characteristics of the lagoons.

Are lagoons efficient for summer wastewater treatment in northern decentralized communities to ensure environmental and human health?

Among wastewater treatment methods, wastewater treatment lagoons are popular in northern decentralized regions. There is however a shortage of studies on northern wastewater treatment efficiency. This research addresses this gap by sequentially evaluating lagoon efficiency in a northern Canadian community, aiming to determine the feasibility or the necessity for improvement or alternative methods. The study encompasses physicochemical and human enteric viruses' detection in wastewater, crucial for mitigating environmental and public health risks. Wastewater lagoons exhibited removal efficiencies of 94.10 % for total suspended solids (TSS), 70.5 % for total solids (TS), 99.89 % for ammonium (NH4), 61.53 % for total nitrogen (TN), 65.85 % for phosphate (PO43−), and 91.3 % for chemical oxygen demand (COD). Human noroviruses GI and GII were detected in raw wastewater and lagoon samples, indicating their presence in the community's sewage system. The inefficiency of the lagoon system in reducing TSS, COD, and PO43− to below standard levels, along with the presence of viruses, raises concerns for environmental and human health in the region, especially considering the community's heavy dependence on land and water resources. Urgent measures are imperative to address these inefficiencies for the well-being of both the environment and the community.

Temporal changes in habitat use by dugongs in a spatially restricted coral reef environment

Context The dynamic habitat use by dugongs (Dugong dugon) in small coral reef lagoon systems spatially limited by tides is not well understood and has hampered adaptive management. Aims We investigated how dugongs locally used a high conservation value coral-reef lagoon system during different seasons and tides to support local management. Methods We conducted local-scale aerial surveys to document the seasonal and tidal changes in the distribution and number of dugongs over seagrass and non-seagrass coral reef habitats in a small lagoon in New Caledonia. The surveys were conducted fortnightly over 18 months in different seasons and at different tides. Temperature loggers and existing local footage of dugong herding behaviour were used to study the habitat use and behaviour of the animals in the area. Key results More dugongs were sighted in Cap Goulvain during the cool season than during the warm season. As tides restricted access to the intertidal seagrass meadows and during the cool season, more dugongs were sighted outside the lagoon on the fore reef shelf outside the lagoon. Dugongs were resting in large aggregations during their use of this non-seagrass habitat. Conclusions Our study emphasises the importance of non-seagrass habitats for dugongs in spatially restricted coral reef environments as well as the importance of considering outer lagoon habitats as key dugong management areas. This study also adds evidence of behavioural thermoregulation in dugongs. Implications The development of dynamic management strategies is essential, especially where different habitats should be protected at different times of the year.

An easily implemented single-visit survey method for intermittently available and imperfectly detectable wildlife applied to the Florida east coast diamondback terrapin (Malaclemys terrapin tequesta).

Single-visit surveys of plots are often used for estimating the abundance of species of conservation concern. Less-than-perfect availability and detection of individuals can bias estimates if not properly accounted for. We developed field methods and a Bayesian model that accounts for availability and detection bias during single-visit visual plot surveys. We used simulated data to test the accuracy of the method under a realistic range of generating parameters and applied the method to Florida's east coast diamondback terrapin in the Indian River Lagoon system, where they were formerly common but have declined in recent decades. Simulations demonstrated that the method produces unbiased abundance estimates under a wide range of conditions that can be expected to occur in such surveys. Using terrapins as an example we show how to include covariates and random effects to improve estimates and learn about species-habitat relationships. Our method requires only counting individuals during short replicate surveys rather than keeping track of individual identity and is simple to implement in a variety of point count settings when individuals may be temporarily unavailable for observation. We provide examples in R and JAGS for implementing the model and to simulate and evaluate data to validate the application of the method under other study conditions.

Growth and reproduction of the shrimp population in a lagoon system in southern Benin (West Africa)

Abstract The aim of this work was to characterize the growth and reproduction dynamics of shrimp in the Lac Nokoué-Chenal de Cotonou complex. The results of one year’s sampling from five stations (North, South, East, Central and West) of the lagoon complex revealed that linear growth in size in Lake Nokoué is decreasing over time in Macrobrachium macrobrachion (the most representative species of the genus Macrobrachium), but positive in Penaeus notialis (the most representative species of the genus Penaeus). Size-weight relationships indicate that the lowest growth coefficient () is obtained in immature males of Macrobrachium felicinum, while the highest growth coefficient () is obtained in mature females of Macrobrachium vollenhovenii, with an average of 2.84 for all shrimp species over both sexes considered. The test indicated that only the species Macrobrachium vollenhovenii has a significant sexual imbalance in favour of females in Lake Nokoué. Fisher’s Least Significant Difference test indicated that the estimated first sexual maturity sizes in Macrobrachium vollenhovenii and M. macrobrachion are significantly different from those estimated in M. felicinum at the threshold. However, the same test indicates that there is not enough evidence to differentiate the sizes of first sexual maturation in M. vollenhovenii and M. macrobrachion. This work revealed that Penaeus monodon was the only species to show better positive growth within all its groups in Lake Nokoué while exposed to anthropogenic effects. A gradual average increase in the size of Penaeus notialis in Lake Nokoué is found between the beginning and end of the saline intrusion (which confirms the life cycle of the species presented). Species of the genus Macrobrachium showed good reproductive capacity, with the absence of sexually mature Penaeus in this lagoon.

Length-Weight and Length-Length Relationships of 39 Demersal Fish Species of an Estuarine-Coastal Ecosystem from the Northwestern of the Baja California Peninsula, Mexico

The length-weight (LW) and length-length (LL) relationships of 39 demersal fish species belonging to 19 families were calculated. Fish samples were collected monthly during the open (September–February) and close (March–August) shrimp fishing seasons from 2014 to 2022 by the artisanal fishery in the Bahía Magdalena-Almejas lagoon system (BMA), using small boats and a shrimp bottom trawl with 16–17 m top rope and 38 mm mesh opening. Total (TL) and standard (SL) lengths and total weight (TW) were measured for all fish specimens. The b parameter of the LW relationship ranged from the minimum of 2.483 for Cynoscion parvipinnis to 3.775 as the maximum for Bagre panamensis while, for the LL relationship, the parameter b ranged from 0.685 for Balistes polylepis to 0.994 for Orthopristis cantharinus. Both LW and LL relationships were highly correlated (r2>0.95; P<0.05. The parameter b of the LW relationship indicated that 59% of the fish species showed isometric and 41% allometric growth. Information on LW and LL relationships is updated for thirteen species, and four are reported for the first time: Citharichthys xanthostigma, Ophidion galeoides, Pleuronichthys guttulatus, and P. ritteri. This study will be useful to update the LW relationship parameters for data-poor fish species and contribute to the accuracy of fish stock assessment in the BMA fisheries.

Holocene organic matter composition in relation to relative sea level stands and associated morphometric changes of a lagoonal system

Garzón Lagoon is a temperate shallow coastal lagoon influenced by sea level variation. A study on the isotopic composition of Holocene sedimentary organic matter was performed. Although the system was subject to significant changes in sea level, leading to important changes in the lagoon morphometry during the Holocene, the composition of the organic matter was rather surprisingly constant, being dominated by particulate organic matter of marine origin, and to a lesser extent of terrestrial origin. By ∼5000 yr BP, the sea level was +5 m amsl, and the lagoon displayed the largest morphometric dimensions. Once the sea level decreased towards 3000 yr BP and present times, the lagoon area progressively decreased. Even though we inferred significant changes in morphometry, the composition of the organic matter remained relatively constant, as the lagoon was always connected to the ocean, a condition that remains today, at least intermittently during storms or heavy rains. Only after the 1960s, a slight change in the organic matter composition was detected, consisting of a decrease in particulate organic matter of terrestrial origin.

Anthropogenic vs. natural habitats: Higher microbial biodiversity pays the trade-off of lower connectivity

Climate change and anthropogenic disturbances are known to influence soil biodiversity. The objectives of this study were to compare the community composition, species coexistence patterns, and ecological assembly processes of soil microbial communities in a paired setting featuring a natural and an anthropogenic ecosystem facing each other at identical climatic, pedological, and vegetational conditions. A transect gradient from forest to seashore allowed for sampling across different habitats within both sites. The field survey was carried out at two adjacent strips of land within the Po River delta lagoon system (Veneto, Italy) one of which is protected within a natural preserve and the other has been converted for decades into a tourist resort. The anthropogenic pressure interestingly led to an increase in the α-diversity of soil microbes but was accompanied by a reduction in β-diversity. The community assembly mechanisms of microbial communities differentiate in natural and anthropic ecosystems: for bacteria, in natural ecosystems deterministic variables and homogeneous selection play a main role (51.92%), while stochastic dispersal limitation (52.15%) is critical in anthropized ecosystems; for fungi, stochastic dispersal limitation increases from 38.1% to 66.09% passing from natural to anthropized ecosystems. We are on calcareous sandy soils and in more natural ecosystems a variation of topsoil pH favors the deterministic selection of bacterial communities, while a divergence of K availability favors stochastic selection. In more anthropized ecosystems, the deterministic variable selection is influenced by the values of SOC. Microbial networks in the natural system exhibited higher numbers of nodes and network edges, as well as higher averages of path length, weighted degree, clustering coefficient, and density than its equivalent sites in the more anthropically impacted environment. The latter on the other hand presented a stronger modularity. Although the influence of stochastic processes increases in anthropized habitats, niche-based selection also proves to impose constraints on communities. Overall, the functionality of the relationships between groups of microorganisms co-existing in communities appeared more relevant to the concept of functional biodiversity in comparison to the plain number of their different taxa. Fewer but functionally more organized lineages displayed traits underscoring a better use of the resources than higher absolute numbers of taxa when those are not equally interconnected in their habitat exploitation. However, considering that network complexity can have important implications for microbial stability and ecosystem multifunctionality, the extinction of complex ecological interactions in anthropogenic habitats may impair important ecosystem services that soils provide us.

State of Surface and Vertical Salinity in Puttalam Lagoon during North-East Monsoon

Puttalam Lagoon which covers 226 km2 located in Sri Lanka‘s Northwest coast, plays an important role in aquaculture and lagoon capture fisheries. Kala oya and Mee oya are the major freshwater sources which empties into the Lagoon by eastern bank. Salinity variability is an important environmental variable in lagoon system that has an impact on aquaculture and aquatic resources. During the Northeast monsoon (NEM) in 2021, the spatial and vertical fluctuation of salinity in the lagoon was studied using SBE 19plus V2 CTD profiler. Field measurements show that the vertical salinity stratification in the lagoon was substantial during the study period. The lagoon has a significant spatial variability of salinity, ranging from 15 psu to 26 psu and Kala Oya river mouth has a salinity of 22 psu which impacted by freshwater and sea water circulation. The Salinity stratification in eastern section of the lagoon where the Kala Oya and Mee Oya streamflow reach is observed with surface salinity of 15 psu. During the NEM season, the average discharge of Kala Oya and Mee Oya to the lagoon was 10.8 m3/s and 9.4 m3/s, respectively, with a mean monthly precipitation of 48.89 mm. Fresh water from the Kala and Mee oya rivers flows into the lagoon during the season, while low evaporation and significant rainfall led the salinity to decline during the wet season, influencing the structure and function of lagoon ecosystems. The study reveals that a significant area of the lagoon is covered by the 20-30 psu salinity range, which is more appropriate for brackish water fisheries, particularly for shrimp and prawns during NEM. 
 Keywords: Salinity, CTD profiling, Northeast Monsoon, Freshwater

Processes of stratification and vertical turbulent mixing in a choked lagoon system

This work concentrates on the processes of stratification and turbulent mixing in a choked shallow lagoon, Xiaohai Lagoon, by using a three-dimensional hydrodynamic model. The model results were processed to derive buoyancy frequency, shear production, gradient Richardson number, and buoyancy flux during the tidal cycles. The parameters regarding stratification and turbulent mixing exhibited significant heterogeneity within the lagoon. Shear production primarily occurred in the downstream region with complex shoreline and bed morphology, whereas stratification was predominantly developed in the flat upstream region by tidal strain and baroclinic strain, especially during the ebb tide. The salinity mixing indicated by buoyancy flux was thus mainly confined during the ebbs in the downstream region and the middle-lower layer of the upstream region. In addition, the distribution of the gradient Richardson number indicated dominances of shear instability and buoyancy effects in the downstream and upstream regions, respectively. By simulating various combinations of river discharges and offshore tidal ranges, we examined the variations of stratification and turbulent mixing within the lagoon's parameter space. The results revealed the influence of the interaction between tidal and runoff forces through a modulation of the salinity interface's moving range. Further investigation of the buoyancy balance underlying the variation in stratification revealed the dominance of straining and mixing, while advection played a secondary role. Straining dominance appeared at locations with sufficient streamwise density gradients in the upstream region during the ebb. The contribution of advection was essential, as straining and mixing largely counteracted each other's effects through their persistent competition. A conceptual model for the stratification and mixing patterns in choked lagoons during the tidal cycle was then proposed. This conceptual model clarifies the process of the interaction between stratification and turbulent mixing in the distinctive hydrological and geomorphic environments of choked lagoons and could serve as a conference for investigating other lagoon systems in the world.

Gonad pathology, sex hormone modulation and vitellogenin expression in Chrysichthys nigrodigitatus from Lagos and Epe lagoons within the southern-lagoon system, Nigeria.

Introduction: Estrogenic chemicals in aquatic environments impact fish reproductive health, with vitellogenin protein levels serving as a crucial biomarker for xenoestrogen exposure. Limited knowledge exists on estrogenic effects in tropical environments, prompting an investigation into the influence of environmental estrogens on Chrysichthys nigrodigitatus in Lagos and Epe lagoons. Methods: A total of 195 fish samples underwent analysis for vitellogenin protein, sex hormones (testosterone and 17 β-estradiol), and gonad pathology in effluent-receiving areas of the specified lagoons. Results: Gonadal alterations were observed in male and female fish, including empty seminiferous tubules and distorted ovaries. Intersex occurred in 3.81% of Lagos and 3.33% of Epe. Testosterone levels were generally higher in females and males from both lagoons, while E2 levels were higher in females from both lagoons, with Lagos showing higher levels than Epe. Vtg levels were higher in males than females in Lagos samples but showed no significant difference in Epe samples. Discussion: Contaminant analysis revealed similar trends in metals (Hg, As, Cr) and phthalates (DEHP, DBP, DEP) in both sexes in the Epe population. Multivariate depictions from the PCA showed sex-specific patterns of metal uptake (Cd) in male fishes at the Lagos Lagoon. The positive association between higher pH loadings and metal and DBP levels in sediment at the Lagos lagoon suggests the influence of higher alkalinity in lower bioavailability of contaminants. Conclusion: Endocrine disrupting effects were observed in male and female Chrysichthys nigrodigitatus in Lagos and Epe lagoons populations, with notable differences in hormone and contaminant concentrations between the two lagoon systems. Identification of specific contaminants and their spatial and temporal trends can inform targeted management and remediation efforts to protect and restore these valuable aquatic ecosystems.

The eutrophication process in the lagoon systems of eastern Rio de janeiro investigated through the analysis of sedimentary phosphorus and historic of basin occupation

Lagoons along the eastern coast of Rio de Janeiro serve as vital corridors for the preservation of marine and coastal biodiversity. However, these ecosystems are facing substantial threats stemming from environmental degradation and cultural eutrophication. This study aims to investigate the process of eutrophication by analyzing sedimentary environments in coastal lagoons located in the municipalities of (Itaipu) Niterói, (Fora) Saquarema, and Araruama (São Pedro da Aldeia). The investigation involves the analysis of sedimentary records collected at various times in each lagoon, with particular focus on phosphorus content and grain size distribution, emphasizing silt, clay and sand fractions. These analyses are correlated with the historical population growth in the drainage basins. Our working hypothesis posits that the impacts of urbanization on the degradation of lagoon systems are archived within the sedimentary records. It is anticipated that the extent and magnitude of these impacts are correlated with population density. The notable increase in demographic density can be attributed to the inauguration of the Rio-Niteroi Bridge, resulting in a significant influx of residents and tourists into the coastal region in question. This hypothesis is supported by census data, which reveal substantial population growth in coastal areas. In addition, this study utilizes ordination analysis, specifically Principal Component Analysis (PCA), to classify sedimentary layers based on their depositional characteristics. The PCA allows for the categorization of sedimentary data, unveiling changes in erosion and sedimentarion patterns. Remarkably, our research stablishes a significant correlation between the escalating total phosphorus fluxes and population growth, thereby providing valuable insights into the historical progression of cultural eutrophication within the coastal lagoon systems of eastern Rio de Janeiro. Overall, our findings contribute to an enhanced understanding of how urbanization and population dynamics have influenced the eutrophication process within there vital coastal ecosystems over the past five decades.