Shallow Lagoon Research Articles

Effects of geomorphic-induced turbulence on horizontal mixing in the coastal lagoon Xiaohai in China

Geomorphic conditions and the resulting turbulence are significant factors that influence coastal lagoonal environments. In this study, a shallow-water hydrodynamic transport model was employed to investigate turbulence related to geomorphic features in a large shallow lagoon (Xiaohai Lagoon) in China and to explore the effects these features have on horizontal mixing and the dissipation of tidal energy within the lagoon. At various tidal stages, the vorticity distribution revealed the presence of large-scale turbulent structures associated with the local geomorphic features found in the downstream part of Xiaohai Lagoon, which enhanced flow shear in the affected area and governed local mixing. Increased tidal range enhanced the horizontal mixing flux in the upstream part of the lagoon during spring-neap cycles. In contrast, the mixing flux in the downstream region declined during spring tides and increased during neap tides due to phase differences between tidal flow processes and tracer concentration. In addition, tidal energy dissipation was most concentrated in the vicinity of the local geomorphic features. The rate of dissipation from the inlet to the upstream end of the deep groove accounted for 99.6% of the total in Xiaohai Lagoon, resulting in a loss of 72% of the tidal range in the upstream region, which substantially limited the upstream tidal prism and water mixing. This study suggests that turbulent mixing and energy dissipation associated with local geomorphic features are important mechanisms governing water exchange and environmental heterogeneity in lagoons and should be considered when formulating management and optimization strategies for coastal lagoons.

Assessing the effects of coral reef habitat and marine protected areas on threatened megafauna using aerial surveys

Abstract Overfishing and habitat degradation are major threats to marine megafauna worldwide. Marine protected areas (MPAs) are effective spatial conservation tools for reducing anthropogenic pressures on threatened species but their benefits for megafauna are still debated. While the effects of MPAs on species abundances are widely reported, few studies have simultaneously investigated the confounding effect of habitat. This study aimed at disentangling the effects of coral reef habitat and spatial protection on megafauna densities in a shallow lagoon partly covered by a no‐take MPA in New Caledonia (South‐west Pacific). Twenty replicates of aerial‐video surveys (representing 17 h of videos) were conducted during a 5‐month period to estimate and map the densities of five megafauna taxa (dugongs, sea turtles, sharks, Dasyatidae rays and Myliobatidae rays). A permutational multivariate analysis of variance was then applied to assess and disentangle the effects of coral reef habitat obtained from high‐resolution satellite imagery and spatial protection on megafauna taxa densities. The analysis revealed a significant effect of protection for sharks and Myliobatidae, with observed densities respectively 9 and 3 times higher inside the MPA compared with outside. The results also highlighted a significant combined effect of habitat and protection for dugongs and Dasyatidae, as well as a significant effect of habitat alone for Dasyatidae. In contrast, no significant effect of habitat or protection was detected for sea turtles. In conclusion, this study revealed positive effects of protection (alone or combined with habitat) for four of the five studied megafauna taxa, confirming the effectiveness of the current MPA. Future studies should be conducted over broader spatial and temporal scales to examine whether detected effects hold beyond the surveyed period and area.

Characterization of Phosphate Compounds along a Catena from Arable and Wetland Soil to Sediments in a Baltic Sea lagoon

Phosphorus (P) is an indispensable nutrient for arable crops, but at the same time, contributes to excessive eutrophication in aquatic ecosystems. Knowledge about P is essential to assess the possible risks of P being transported towards vulnerable aquatic ecosystems. Our objective was to characterize P along a catena from arable and wetland soils towards aquatic sediments of a shallow lagoon of the Baltic Sea. The characterization of P in soil and sediment samples included a modified sequential P fractionation and P K-edge X-ray absorption near edge structure (XANES) spectroscopy. The concentrations of total P ranged between 390 and 430 mg kg−1 in the arable soils, between 728 and 2258 mg kg−1 in wetland soils and between 132 and 602 mg kg−1 in lagoon sediments. Generally, two sinks for P were revealed along the catena. The wetland soil trapped moderately stable P, Al-P and molybdate-unreactive P (MUP), which are most likely organically bound phosphates. Sediments at the deepest position of the catena acted as a sink for, MUP compounds among the lagoon sediments. Thus, wetlands formed by reed belts can help to prevent the direct transfer of P from arable soils to adjacent waters and deeper basins and help to avoid excessive eutrophication in shallow aquatic ecosystems.

Benthic diatom diversity in a turbid brackish lagoon of the Baltic Sea

ABSTRACT The Darß-Zingst Bodden Chain is a tide-less shallow lagoon at the Southern Baltic coast. It was and is studied in almost all hydrological, biogeochemical as well as floristic and faunistic aspects. Benthic diatoms were studied using light and scanning electron microscopy (SEM) in the early 1970s and one sampling site was now revisited. A total of 103 diatom taxa were recorded in sediment and on macrophyte samples collected between 2015 and 2019. In the sediment samples, epipsammic diatoms accounted for almost 90% of the total valve counts. In the 1970s, only three epipsammic species were observed, while we recorded a total of 27 epipsammic taxa, most of which were very small (<12 µm). Since those earlier studies, many of these species have been newly described or transferred from other genera. Moreover, small diatoms may have been misidentified, overlooked or counted as important. This study emphasizes, in addition, the need to combine light microscopy with electron microscopy to allow the unambiguous identification also of small entities, and to reach a comprehensive overview over the diatom flora present in different benthic habitats.

Flooded mangrove landscapes hide ancient Maya coastal sites in Belize

Evidence of ancient Maya exploitation of salt, other marine resources, settlement, and sea trade is hidden in flooded mangrove landscapes on the cays, mainland, and in shallow offshore locations on the south coast of Belize. This article includes a discussion of the coastal economy from the Middle Preclassic through the Postclassic periods (600 B.C.–A.D. 1500). Data from sites discovered and excavated since 1982 in the coastal area of the Port Honduras and Paynes Creek National Park support a model of coastal reliance on marine resources and tree crops. The need for a regular supply of coastal salt to inland cities may have expanded the market for other marine resources. Obsidian imported from volcanic highlands documents long-distance trade throughout prehistory in the area. The island of Wild Cane Cay expanded its role in long-distance coastal trade after the abandonment of inland cities in southern Belize at the end of the Classic period. Inundation of the region documented from the depths of radiocarbon-dated archaeological deposits below the water table and from a sediment core indicates sea-level rise of at least 1 m that submerged the coastal sites. The waterlogged deposits provided an ideal matrix for preservation of vertebrate material at Wild Cane Cay. The red mangrove (Rhizophora mangle) peat below the sea floor in a shallow lagoon preserved wooden buildings.

Inter-seasonal comparison of acoustic propagation in a Thalassia testudinum seagrass meadow in a shallow sub-tropical lagoon.

Acoustic propagation measurements were collected in a seagrass meadow in a shallow lagoon for periods of over 65 h in winter and 93 h in summer. A bottom-deployed sound source transmitted chirps (0.1-100 kHz) every 10 min that were received on a four-receiver horizontal hydrophone array. Oceanographic probes measured various environmental parameters. Daytime broadband acoustic attenuation was 2.4 dB greater in summer than winter, and the median received acoustic energy levels were 8.4 dB lower in summer compared to winter. These differences were attributed in part to seasonal changes in photosynthesis bubble production and above-ground seagrass biomass.

Performance of blue mussel culture in nearshore and offshore environments

Bivalve aquaculture in nearshore sites has expanded worldwide. Mussel farming productivity is commonly assumed to depend on survival and growth performance, which can be highly variable among spat stocks originating from different sites, even at a microgeographical scale. Using a traditional two-year production cycle, we monitored the productivity of neighbouring blue mussel (Mytilus edulis) spat stocks that had been cultivated in such contrasted environments that are shallow lagoons and open sea sites. We demonstrated that mussels collected in the nearshore, Bassin du Havre-Aubert (BHA) lagoon, exhibited the best survival rate (≥ 90%) in both nearshore and offshore sites, while other stocks experienced mortality as high as 60% under the same conditions. At spat recovery, the BHA spat stock showed higher gene expression levels for catalase and heat shock protein 70 (HSP70), which are involved in antioxidant defenses and the cellular stress response, respectively. Offshore conditions clearly enhanced overall growth performance independently of stock origin, as shown by the higher condition indexes, higher energy lipids (triacylglycerol), and generally higher glycogen content in mussels at the end of the production cycle. These observations of improved performance at the more favourable open-water conditions, particularly during summer, confirmed the importance of site-related environmental factors for productivity. The observed survival (+ 23%) and growth (+ 27%) trends support the hypothesis that offshore cultivation represents a valuable strategy for mussel aquaculture development. Considering current social, environmental, economic, and resource constraints, offshore mussel cultivation may be a viable alternative strategy for aquaculture development.

Paleoenvironmental constraints on shallow-marine carbonate production in central and West Texas during the Albian (Early Cretaceous)

The Albian Glen Rose Formation in central and west Texas records carbonate sedimentation in a broad epicontinental sea partly contemporaneous with Oceanic Anoxic Event 1b. The paleogeographic setting of the Comanche Platform facilitated the deposition of carbonate sediments that resulted in carbonate matrix-rich facies, with various amounts of allochems, which permitted the interpretation of shallow lagoon depositional settings. Geochemical proxies for environmental conditions (nutrient supply, detrital input, redox conditions) were calculated from the elemental geochemical analysis of samples, while their carbon and oxygen isotope composition was used to evaluate the impact of diagenesis. The statistical analysis of this dataset helps identify three intervals within the Glen Rose Formation where the matrix-rich carbonate sedimentation was modulated by environmental parameters. First, the strong correlation between MgO concentration and δ18O vectors on a Principal Component Analysis for the whole dataset confirms the deposition of dolomitic series with stromatolites in a restricted environment. Second, moderately high nutrient input and low detrital flux suggest that part of the sedimentation in west Texas was affected by upwelling. Third, mesotrophic conditions associated with a patch reef made of rudist bivalves support their suspension feeder ecological behavior. Conclusions drawn for this research may apply to other shallow-marine series deposited in broad epicontinental seas affected by greenhouse conditions.

Late Pleistocene-Holocene Evolution of Malé Island (North Malé Atoll Rim, Republic of Maldives)

Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square kilometres, with a maximum relief of 2.7 m and a population of 236,000 inhabitants. It is amongst the most densely populated areas on Earth and located virtually at sea-level. This study focuses on the late Pleistocene-Holocene evolution of Malé island that recently formed as part of the discontinuous North Malé Atoll rim. Understanding the formation of Malé Island is relevant in predicting its future in the context of accelerating rates of sea-level rise in the next centuries due to anthropogenic global warming. Analyses of two boreholes up to 35 m-long, published information from additional boreholes drilled on Malé Island and a high-resolution multi-beam bathymetric survey acquired along its upper slopes and deep surroundings were available for this study. Two distinct sedimentary units were recovered from the boreholes. Facies analyses of the lower unit reveal an overall deepening coralgal reef that accumulated probably during the previous interglacial (Marine Isotope Stage = MIS 5e) and which was subsequently altered by meteoric diagenesis during a 100 kyr-long time of exposure. The upper unit consists of Holocene unconsolidated coralgal accumulation, unconformably overlying the lower karstified coralgal MIS 5e unit. The upper unit, protected behind a karstified late Pleistocene reef, was initiated at ~8200 yr BP and vertically grew 25 m-high until 6510 yr BP in the northern part of the Malé Island area, which at the time was a karstified limestone island with a central geomorphological depression. The narrow, 30 to 35 m-deep, newly formed central faro lagoon started to fill ~ 5500 yr BP, when a reef initiated on top of the southern highest Pleistocene karstified reef and sea-level rise stalled. The infilling of the faro lagoon was completed ~ 4500 yr BP. An island formed that was flanked on its south side by a shallow lagoon and surrounded by a reef flat. Through several phases of land reclamation since the 1950s, the shallow lagoon was infilled and the reef flat buried with sand and rubble to form Malé Island as it is known today.

Lagoonal reef island formation in Huvadhoo atoll, Maldives, highlights marked temporal variations in island building across the archipelago

Coral reef islands provide the only pedestals of human habitation in mid-ocean atoll archipelagoes. Understanding the environmental controls on island formation is critical for evaluating the future response of islands to environmental change and sea-level rise. This study examines the evolution of lagoonal reef islands in Huvadhoo atoll, southern Maldives. Using extensive ground penetrating radar (GPR) imaging of island sediment structure, combined with comprehensive analysis of island morphology, sedimentology, and 49 radiometric dates, detailed reconstructions of the evolution of two lagoonal islands is presented. A four-stage model shows a complex history of island formation across various stages of sea-level change during the late-Holocene: 1) lagoon infill occurring from ~3000–2000 years ago during a period of sea-level fall from the mid-Holocene highstand; 2) emergence of the island core through vertical aggradation during the latter stages of sea-level fall between ~2000 and 1500 yBP; 3) rapid lateral expansion of the islands between 1500 and 500 yBP coincident with the availability of sand-size sediments and during a period of sea-level oscillation; and, 4) subsequent minor expansion and modification of island shorelines through alongshore reworking of island sediments over the past 500 years. Results provide evidence of marked differences in the timing and mode of island formation within Huvadhoo atoll. Significantly, the formation of the lagoonal islands post-dates the formation of islands on the atoll rim by 1000–2000 years. Furthermore, the formation of sand islands over infilled shallow lagoons contrasts the formation of most atoll rim islands through the sequential deposition of storm-generated rubble deposited directly across reef surfaces that have reached their vertical growth limit. Results of lagoonal island formation in the southern Maldives provide comparative data for the northern Maldives. While the sequence of island formation follows the faro infill model identified in the northern archipelago, lagoonal islands in the south appear to have formed 2000 years after those in the north. This difference is likely to reflect lagged reef growth response from deeper foundations in the southern archipelago.

Gongolaria barbata forest in the shallow lagoon on the southern Istrian Coast (northern Adriatic Sea)

Abstract The Gongolaria barbata forest inhabiting Šćuza lagoon on the southern Istrian coast (northern Adriatic) represents the last significant refuge for this species among the shallow waters of the Istrian Coast. The lagoon is characterised by extreme winter and summer temperatures. Moreover, the absence of certain grazers could be one of the main factors favouring the development and growth of G. barbata forest. Two morphologically distinct forms of G. barbata inhabit the lagoon: attached and detached. Abundance and morphological characteristics of each form were analysed in randomly sampled thalli. The wet weight, thallus length, number of cauloids and total cauloid length were significantly higher in the detached than in the attached form. Although the main cauloid was highly branched in both forms, its total length was up to three times higher in the detached than in the attached form. Our study suggests that this population of G. barbata can thrive in the extreme conditions found in the lagoon, while also exhibiting two distinct forms. Furthermore, this large population could serve as a donor for future restoration attempts on the western Istrian Coast where a decline of G. barbata has been confirmed in recent years.

Climatic and environmental changes in the Baidunzi wetland, Northwest China, over the last 800 years inferred from glycerol dialkyl glycerol tetraethers

To help understand the temperature and moisture variations in the semiarid and semi-humid regions of China that lie a transitional zone between the Westerlies and the East Asian monsoon, reconstruction of the regional climatic changes over the last millennium is useful. However, high-resolution time-series data related to the histories of climatic changes in these areas are limited. Therefore, this multiproxy analysis of a sediment core from the Baidunzi wetland, northwest China, was conducted using grain size, total organic carbon, glycerol dialkyl glycerol tetraethers (GDGTs), and molecular biomarkers. The results show that GDGTs can reliably reconstruct paleoclimate changes recorded in sediments in salt marsh environments. The climate and environment history of the past 800 years can be divided into the three stages: the end of the dry Medieval Warm Period (MWP) (1278–1366 CE), a humid Little Ice Age (LIA) (1366–1896 CE), and the humid Current Warm Period (CWP) (1896–1999 CE). The Baidunzi setting during the end of the MWP was a warm and dry wetland with high salinity, low water levels, and emersed aquatic plants, and the depositional environment transitioned from fluvial facies to shore lake facies. In contrast, the local climate during the LIA was cold and humid, and the era was characterized by the appearance of vascular flora and two short-term flooding events, that caused a rise in water levels. The lowest temperatures and highest salinities of the period were correlated, which was likely caused by seasonal freeze-thaw cycles. During the CWP, the local climate was warm and humid, with a higher water level than during the LIA, and emersed plants again developed in shallow lagoon facies. Generally, salinity was positively correlated with temperature, except for freezing and thawing salinization resulting from episodes of extremely low temperatures. The warm–dry to cold–humid climate changes of the area were like those of arid Central Asia, which indicates that the Baidunzi region was affected mainly by the Westerlies and was impacted by southward intrusions of that system. The area was also affected by the North Atlantic Oscillation and experienced diminished evaporation during periods of cold climate.

Predicting and Scoring Estuary Ecological Health Using a Bayesian Belief Network

Excessive nutrient and sediment inputs threaten ecological condition in many estuaries. We describe a Bayesian Belief Network (BBN) that calculates an Estuary Trophic Index (ETI) score ranging between 0 (no symptoms of eutrophication) to 1 (grossly eutrophic) for estuaries in Aotearoa New Zealand (NZ). The ETI BBN includes estuary physiographic characteristics (estuary type, flushing time, intertidal area, estuary closure state, water column stratification) and nutrient and sediment loads available from existing geospatial tools and databases, that drive responses of ‘primary’ indicators (macroalgae and phytoplankton biomass) and ‘secondary’ indicators (or symptoms) of estuary ecological impairment (sediment carbon, sediment apparent redox potential discontinuity depth, water column oxygen, macrobenthos and seagrass condition). Relationships between the BBN nodes are based primarily on observational and model-based information from NZ and international studies rather than expert opinion. The model can be used in a purely predictive manner under knowledge-poor situations, using only the physiographic drivers and nutrient/sediment loads, or refined using field-derived observations of indicator values to reduce the uncertainty associated with the probabilistic BBN score. It is designed for shallow tidal lagoons, tidal river estuaries and coastal lakes; systems which are sensitive to eutrophication and sedimentation pressure and are common in NZ and globally. Modelled ETI BBN scores agreed well with ETI scores calculated from observed indicator values for 11 well-studied NZ estuaries. We predict ecological condition of 291 NZ estuaries, most of which have no monitored information on trophic state. We illustrate capabilities of the ETI BBN with two case studies: to evaluate improvements in estuary health arising from diversion of wastewater from an estuary via an ocean outfall, and to estimate catchment diffuse nutrient load reductions required to meet estuary health objectives. The ETI BBN may serve as a template for other agencies wishing to develop similar tools.

Predicting long-term solid accumulation in waste stabilisation lagoons through a combined CFD-process model approach

Sludge accumulation in anaerobic lagoons is one of the major issues determining long-term operating costs. However, very little mechanistic analysis has been done on long-term sludge behaviour. A coupled hydrodynamic-biochemical model was developed using computational fluid dynamics (CFD), and results from this applied to a compartmental based model (CBM) for long-term simulation. The CFD model incorporates a mixture method for the spatial-and temporal evolution of fluid and solids with a non-Newtonian rheology. CFD was used to evaluate short term hydrodynamics, and a common CBM used to understand the fluid movement and sludge behaviour of full-scale anaerobic lagoons (with varying depths, sidewall slopes, and loading rates), operating in commercial piggeries located in Southern Queensland and Southern New South Wales, Australia. The results found that the lagoons had varying hydrodynamics, and sludge accumulates rapidly in sloped sidewall lagoons, forming a variable depth bed which occupied a substantial fraction of the lagoons. Shallow lagoons were dominated by significant surface recirculation dynamics, and were susceptible to solids accumulation, while deep lagoons allowed the formation of a well developed settled fraction. Predicted lagoon lifetimes varied substantially, but predicted long-term accumulation rates were approximately double that observed, due to long-term degradation of slowly degradable material.

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

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.

The Effects of Different Inlet Configurations on Particles Transport and Residence Time in a Shallow and Narrow Coastal Lagoon: A Numerical Based Investigation

Setiu Lagoon experienced shoreline alterations, leading to the opening of a new inlet and the closing of the old one. To evaluate the effects of these alterations on the tidal flow in this shallow and narrow lagoon, a numerical hydrodynamic model was developed. The model-predicted water level and current velocities were validated against field measurements, which yielded a high simulation skill. The transport of particles and residence time under different inlet configurations were also investigated through the implementation of numerical tracers released from R1, R2, and R3, which represent different pollution sources. The results indicated that the particle transport and residence time in Setiu Lagoon varied spatially and temporally depending on the release locations, proximity to the inlet, and tidal current strength. Comparing the scenarios, the flushing efficiency in Setiu Lagoon was improved with the presence of both inlets, resulting in a shorter residence time of less than 50 days. The findings of this research are vital for understanding the water current flow and residence time in this restricted lagoon, while evaluating the possible adverse effects on its water quality. Although this work is case-study based, the output is applicable to other lagoon systems with similar characteristics.

Late Holocene development of Bubiyan Island, Kuwait

AbstractBubiyan Island, presently a vast sabkha and salt flat in the westernmost part of the Shatt Al-Arab delta, originated ca. 4000 cal yr BP as prodelta deposits from a paleochannel of the Euphrates River that flowed into a shallow sea. Southeastern Bubiyan Island first surfaced when spits and barrier islands formed on a 1–2 m forebulge caused by heavy sediment load to the northwest; the spits and barriers delineated an incipient shoreline and sheltered a shallow lagoon. Progradation of southeastern Bubiyan Island began when the spits and barriers were gradually stranded as beach ridges during minor sea-level fluctuations and continued marginal uplift. AMS dating of the beach ridges, which are ~1–5 km from the present shoreline, implies that Late Holocene relative sea level fell in three phases: ca. 3700–3400 cal yr BP, ca. 2600–1000 cal yr BP, and ca. 600–500 cal yr BP. Prior to each phase, relative sea level apparently stabilized to near stillstands, allowing spits and barriers to accrete. Torpedo-jar pottery sherds scattered on some of the most prominent beach ridges indicate Sasanian (AD ca. 300–650; 1650–1300 cal yr BP) to early Islamic (AD ca. 650–800; 1300–1150 cal yr BP) periods of human presence, concurrent with the Second phase of beach-ridge formation.

Eelgrass beds can mitigate local acidification and reduce oyster malformation risk in a subarctic lagoon, Japan: A three-dimensional ecosystem model study

It is well known that ocean acidification (OA) inhibits growth of marine calcifying organisms. Therefore, the adverse effects of acidification on marine ecosystems and aquaculture, such as oyster farming, are of concern. Since eelgrass beds in neritic areas have a high potential for carbon assimilation, this study focuses on local scale mitigation of OA effects. Using a three-dimensional lower-trophic system ecosystem model, we modeled nitrogen and carbon cycles, and the dynamics of carbonate parameters in a subarctic shallow lagoon and bay, where nitrogen availability limits the photosynthesis of primary producers. Simulation of the present conditions allowed reproduction of spatiotemporal variations in water quality and, by assuming future environmental changes quantitatively, revealed that the progress of OA significantly elevated the probability of shell malformation in juvenile oysters. The results represent the spatiotemporal variations in carbonate parameters inside and outside eelgrass beds and enable the evaluation of the alleviation effect on local acidification by the presence of a dense eelgrass bed. Our study shows that in the absence of the eelgrass bed scenario, the effect of OA on oysters became more remarkable. The simulations revealed that maintaining eelgrass beds is essential to mitigate the effects of acidification on oysters.

Endoparasites of Hypostomus commersoni (Siluriformes, Loricariidae) from two shallow lagoons, Argentina

Hypostomus commersoni is a freshwater fish, native to the Paraná River basin, which plays an important role in trophic networks of this system. This study aimed at analyzing the structure of the endohelminth community of H. commersoni from two shallow lagoons in the municipality of Santa Fe, Argentina. In the 51 hosts analyzed, 2103 helminths were found. Hosts from Belgrano Park lagoon were infested with Genarchella genarchella, Saccocoelioides nanii, Raphidascaris (Sprentascaris) sp., and Gorytocephalus elongorchi. Hosts from the Western Urban Nature Reserve lagoon were infested with Thometrema magnifica, Procamallanus (Procamallanus) annipetterae, Raphidascaris (Sprentascaris) sp., Gorytocephalus elongorchi, and Proteocephalidae spp. In both host populations, the prevalence of some parasites was high, and species richness and diversity of component communities were low. The distribution pattern of helminth was aggregated in all cases. No correlation was found between the length of the host and the richness and abundance of endoparasites. The total number of parasites and the specific richness per host in both lagoons did not differ significantly. The findings on G. genarchella, P. (P.) annipetterae, G. elongorchi, and Proteocephalidae spp. were the first records in his host

Groundwater Quality around upstream and downstream area of the Lagos lagoon using GIS and Multispectral Analysis

Despite covering over 70% of the earth crust, access to potable water is still extremely challenging due to the ubiquity of several water contaminants. In mitigating the effects of these aquifer pollution, a distinctive identification of polluted areas as well as pollution sources is essential. To address the Africa Union's Agenda 2063 goal for environmental sustainability in water security, the Lagos coastal aquifer was evaluated for groundwater pollution induced by seawater intrusion. Hence, the purpose of this study is to determine a zone with suitable groundwater. In so doing, we obtained forty-three groundwater samples for hydrochemical evaluation within selected areas of the Lagos metropolis. However, physico-chemical analyses were conducted on the collected groundwater samples; hydrochemical facies were used to evaluate the dissolved cations and anions. Apart from utilizing the water quality index (WQI) to determine the samples portability, the sodium absorption ratio (SAR) was calculated and used to ascertain the suitability of groundwater for irrigation purposes. Put differently, a spatial variability map was produced using inverse distance weight (IDW) on the ArcGIS module. Furthermore, the piper tri-linear model was adopted to practically identify the four (4) prominent hydrochemical facies which include Calcium Magnesium Chloride 39.5%, Calcium Bicarbonate 23.3%, Calcium Alkali Bicarbonate 23.3% as well as Alkali Bicarbonate. Using the piper tri-linear model, Calcium possesses the dominant facies in all the samples. The result from the water quality index analysis shows that 16.28% of the water sample is excellent water, 32.56% is good water, 39.53 is poor water, and 11.63 is very poor water. The SAR result of the water sample reveals that 32.56% are excellent water, 44.19% good water, 23.26% doubtful and zero percent are unsuitable. This implies the groundwater around the coastal area can be used for irrigation purposes. Finally, from all the spatial variability maps and potentiometric maps, groundwater around the upstream is preferred to downstream due to groundwater flow direction and its remoteness to the Atlantic Ocean and not the shallow lagoon.