Marginal Lagoons Research Articles

Coevolution of the holocene coastal barrier and lagoon terraces and their implications on the record of relative sea-level change in southernmost Brazil

This paper presents the coeval history of a sandy coastal barrier and four lagoon margins located in the Rio Grande do Sul State, southernmost Brazil. To achieve this objective we compared the Holocene relative sea-level changes recorded along a regressive coastal barrier with the register of base-level fluctuations preserved in the lagoon terraces. We used geomorphology, geochronology, geophysics (GPR), and high-resolution sequence stratigraphy to evaluate changes on the relative sea- and base-level recorded in the barrier and lagoon terraces, respectively. The record of the relative sea-level fall (forced regression) began at ∼4 ka in the coastal barrier and around 3.4 ka in the lagoon system. Maximum altitudes of the eolian/beach deposits boundary are similar on both barrier and lagoon settings, hence pointing out that relative sea-level controlled lagoon base-level. The forced regression stage is more accurately preserved in the margin of the lagoons than in the coastal barrier. Along the former, four progradational sets related to stepped terraces record pulses of relative sea-level fall at 3.4, 1.4, 0.35, and 0.27 ka. The pulses that took place from 1.4 ka onwards are recorded as low terraces in the lagoon but appear in the coastal barrier as an acceleration in the rate of the relative sea-level fall. Each relative sea-level fall is supposed to have liberated beach sands for eolian reworking during the subsequent stillstand phase and allowed the development of transgressive dunes. Therefore, we conclude that lagoonal terraces vertical displacements are adequate proxies for high-resolution analysis of relative sea-level changes.

Taphonomy and taphofacies of the bioclastic accumulations of Baía Formosa Paleolagoon (Quaternary), Rio de Janeiro state, Brazil

The study of taphofacies is extremely relevant in Paleontology as it provides support for paleoenvironmental interpretation by associating the preservation state of fossil content with sedimentological and stratigraphic characteristics. Despite its importance, there are few analyses of taphofacies in bioclastic accumulations of invertebrates in Brazilian sedimentary basins or Quaternary sedimentary accumulations. Therefore, this article aims to identify taphofacies in Holocene bioclastic accumulations distributed along the coastal plains of Armação de Búzios, Rio de Janeiro State, Brazil. After qualitative observations and taphonomic analysis of material from two outcrops located in the Canal Marina Porto Búzios, three distinct taphofacies were identified. Taphofacies 1 was interpreted as a beach environment related to strandlines; taphofacies 2 was interpreted as a shallow lagoon environment; and taphofacies 3 was interpreted as a lagoon margin. The taphofacies identified in this study are related to the maximum Holocene transgression, which occurred in the region about 6000 years BP, and the subsequent marine regression. This study presents relevant and unprecedented data, enabling a better understanding of the coastal evolution of Armação dos Búzios and Cabo Frio.

Some aspects of the reproductive biology of tilapia black-chinned, Sarotherodon melanotheron (Rüppel, 1852) in relation to macrophyte abundance in three marginal lagoons, Southeast of Côte d'Ivoire

Some aspects of the reproductive biology of tilapia black-chinned, Sarotherodon melanotheron (Rüppel, 1852) in relation to macrophyte abundance in three marginal lagoons, Southeast of Côte d'Ivoire

Unforeseen cascading effects of an inlet opening

The opening of the Cacela Inlet (southern Portugal) in 2010 led to unforeseen effects observed after 2017, including an extreme acceleration of the retreat of the inland lagoon margin from about 0.2 to 2 m/year. This was a consequence of the development of a large flood delta in an area of limited accommodation space, forcing the main tidal channel to move inland. The coastal retreat currently affects a flat sandy area that separates the old and inactive Cacela cliff from the lagoon. Between 2035 and 2040, the currently inactive Cacela cliff is likely to become active again, posing a potential risk of damage to a medieval fortress and the existing settlement of Cacela Velha, an unforeseen cascading effect of the opening of the inlet. In order to prevent instability and damage to this legally protected area of national and public interest, several coastal management measures will be required.

Lithofacies and cyclicity of sulphate dominated tidal-lagoon deposits of Late Triassic age in Northeast Iberia (western Europe)

Thick gypsum‑carbonate sequences were deposited in different periods and basins of Europe during the westward opening of the Tethys Ocean. Although they seem to represent widespread perimarine sulphate-dominated lagoons in shallow epeiric platforms, the sedimentary characteristics and interpretation of these deposits are still poorly constrained. To advance in the knowledge of these deposits, a detailed study is presented of two distinctive sulphate dominated sequences of Late Triassic age located in NE Iberia (Western Europe), which correspond to the Canelles and Espinagosa units, found in the southern Pyrenees and the Catalan Coastal Ranges respectively. These sequences present a diverse suite of carbonate and sulphate lithofacies, which are stacked in several recurring sedimentary cycles. These cycles consistently present a carbonate base that transitions to a sulphate top, and can be correlated along several tens of kilometres. Each of the observed cycles depicts an initial sudden flooding of a tidal-lagoon system by marine water, which led to carbonate-dominated sedimentation. Progressive evaporation under dominant arid climate conditions triggered the shallowing of the lagoon and salinisation of its water. Then, a transition from carbonate to gypsum/anhydrite precipitation and the early dolomitisation of the underlying carbonate sediments by brine reflux occurred. Gypsum precipitated in the water column as cumulate crystals and deposited at the bottom of the lagoon, forming laminations or being incorporated into microbial mats. Anhydrite precipitated as early diagenetic crystals in the different subaqueous and subaerial environments of the tidal-lagoon system, leading to a variated set of lithofacies until now largely undocumented. It mainly formed as displacive lath-shaped crystals randomly oriented within carbonate muds at the bottom of the lagoon, which were mostly reworked at the lagoon margins by wave and tidal currents resulting in aligned fabrics in cross-lamination structures. Anhydrite also formed as pure massive beds by anhydritisation of subaerially exposed gypsum sediments during the main retraction stages of the lagoon, as well as typical nodular (sabkha) lithofacies. Such sulphate lithofacies are not easy recognisable due to the lack of modern analogues to compare and to their current transformation into secondary gypsum in the outcrops. These are aspects to be taken into account in future sedimentological studies on similar evaporitic materials.

Stratigraphy and evolution of the late Pleistocene (MIS 5) coastal Barrier III in southern Brazil

Abstract The structure and origin of the Pleistocene (Marine Isotope Stage [MIS] 5) coastal Barrier III in southern Brazil were investigated through analysis of lithofacies, numerical ages, and ground-penetrating radar (GPR) data obtained in outcrops and subsurface deposits. The stratigraphic succession is characteristic of transgressive barriers, with muddy lagoon bottom facies unconformably overlying an older unit (Barrier II) and overlain by landward-dipping lagoon margin and aeolian facies. The back-barrier lagoon was filled with sediments and shells transferred from the foreshore through overwash and/or inlets during the MIS 5e transgressive-high-stand phase, with a higher sea level that reached about +6 to +7 m relative to the present. Marine sediments and shells on the seaward side of the barrier dated to ~100–106 ka indicate another high stand at +4 to +5.1 m during MIS 5c. One shell dated to ~87 ka and aeolian deposits dated to ~82 and ~85 ka suggest a third high stand during MIS 5a that reached at least −2 m relative to the present. The two (possibly three) juxtaposed marine deposits show that Barrier III is a more complex unit than previously recognized, built by successive orbitally forced eustatic sea-level oscillations also recorded in other deposits along the Brazilian coast and worldwide.

Determination of pesticide residue in marginal lagoons of natural parks in Brazil using an improved calibrate passive sampler

Passive sampling is a sensitive and efficient method for analyzing pesticides in water. This article describes a hollow fiber liquid-phase microextraction (HF-LPME) device that was improved using polypropylene membranes grafted with nanocellulose for the passive sampling of pesticides in water. A comprehensive gas chromatography time-of-flight mass spectrometry (GCxGC/Q-TOFMS) system was used to separate, identify, and quantify pesticides. The sampling rates of 38 moderately hydrophobic to hydrophobic agricultural pesticides (2.18 < log Kow < 6.89) from different chemical classes, including the main triazine, organochlorine and organophosphate compounds, were calculated. A calibration process was applied to evaluate the role of flow velocity and select potential candidates for a possible performance reference compound (PRC). Sampling rates varied between 0.17 mL d−1 and 23.15 mL d−1. The accumulation curves identified linear periods ranging from 3 to 18 days. The new passive sampler device was applied for 8 days in rivers and marginal lagoons of natural parks of the São Francisco basin in Minas Gerais, Brazil and identified 10 target pesticides. Furthermore, 10 non-targeted pesticides were detected by the GCxGC/Q-TOFMS method.

Resisting Venice: individual and collective housing practices to stay put in the tourist city

ABSTRACT Whereas Venice (Italy) has been extensively analysed through the lens of tourism, little has been written so far regarding the resistance practices emerging due to increasing tourism-led gentrification. This paper presents two examples of housing initiatives taking place in the historic city and its neighbouring lagoon islands. The first, promoted by a collective actor (Assemblea Sociale per la Casa), concerns the selection, occupation, and self-restoration of public dwellings located in the historic city; the second, an individual choice made by some citizens, concerns moving to the small lagoon islands as not simply a form of displacement, but as a resistance mechanism against the progressive expansion of the tourism industry into the lagoon margins. Drawing on Annunziata and Rivas-Alonso’s work, the aim of this contribution is to provide an interpretation of such initiatives as examples of resistance practices in gentrifying contexts, and to enrich the literature on resisting gentrification by stressing their informal, invisible, and ambiguous nature.

Development of polypropylene membranes grafted with nanocellulose to analyze organic pollutants in environmental waters using miniaturized passive samplers based on liquid-phase microextraction

Reinforcing hollow polypropylene fibers with nanocellulose is a viable alternative for implementing miniaturized passive sampling devices (MPSDs) based on liquid-phase microextraction (LPME). This modification improves the extractive properties of microporous membranes, including the sensitivity to fluctuations in the uptake steps. The new material, polypropylene hollow fiber grafted with nanocellulose, was developed and characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive System (EDS) and Thermogravimetric (TGA) and Differential Thermal (DTA) analysis. The morphology type of the crystallite of cellulose most abundant after chemical regeneration was the CII (Celulose II) allomorphic. Sorption studies were carried out and revealed that the modified membrane could absorb 177% more water than its untreated commercial counterpart, making it suitable for long-term sampling. Miniaturized passive sampling devices were equipped with the new material, and the devices were deployed in situ for passive sampling of organic pollutants in environmental waters of marginal lagoons. Fingerprint analysis of samples was performed by comprehensive two-dimensional gas chromatography coupled with mass spectrometry and identified a variety of pollutants such as pesticides, plasticizers and prescription and illegal drugs and their metabolites. Therefore, these MPSDs can be employed for the sampling and long-term monitoring of water contaminants with a wide range of polarities.

Metazoan endoparasites of Hoplias malabaricus (Bloch, 1794) (Actinopterygii: Erythrinidae) from upper and middle São Francisco river basin, Minas Gerais State, Brazil.

The endoparasitic fauna of Hoplias malabaricus (which is a species of paramount importance in the fishing and human food sectors) from Três Marias reservoir, São Francisco river, and from eleven marginal lagoons in the upper and middle São Francisco river basin, Brazil, was herein recorded for the first time. In total, 13 endoparasite species belonging to ten different families were found in 147 analyzed H. malabaricus specimens. The identified taxa comprised individuals belonging to phyla Apicomplexa-Calyptosporidae-Caplyptospora sp. (oocysts); Platyhelminthes-Trematoda-Diplostomidae (metacercariae)-Austrodiplostomum sp. and Sphincterodiplostomum musculosum, Clinostomidae (metacercariae)-Clinostomum sp., Gorgoderidae (adults)-Phyllodistomum spatula, and Eucestoda-Proteocephalidae gen. sp. (plerocercoids larvae); and Nematoda-Anisakidae (larvae)-Contracaecum sp. Types 1 and 2 and Hysterothylacium sp., Gnathostomatidae (larvae)-Spiroxys sp., Camallanidae (juveniles/adults)-Procamallanus (Spirocamallanus) inopinatus, Guyanemidae (juveniles/adults)-Guyanema baudi, and Cystidicolidae (juveniles/adults)-Cystidicoloides fischeri. Proteocephalidae gen. sp. and Contracaecum sp. Type 1 were the species presenting expressive parasitic indexes in the reservoir, in the river, and in nine of the eleven lagoons. Cystidicoloides fischeri was recorded for the first time in H. malabaricus. Guyanema baudi and S. musculosum had their geographic distribution expanded to São Francisco river basin.

Novel miniaturized passive sampling devices based on liquid phase microextraction equipped with cellulose-grafted membranes for the environmental monitoring of phthalic acid esters in natural waters

Phthalic acid esters (PAEs) are considered endocrine disruptors and potential carcinogens. Consequently, efficient and accurate environmental monitoring of trace levels of these organic pollutants is necessary to protect the population against their hazardous effects. Passive sampling techniques have gained notoriety for environmental monitoring and have been proven highly sensitive to temporal variations. This study developed a miniaturized passive sampling device (MPSD) based on hollow fiber liquid-phase microextraction (HF-LPME). The devices were calibrated in the laboratory using an automated calibration system. The results demonstrated the first-order uptake ranges for Diethyl phthalate (DEP), Diisobutyl phthalate (DiBP), Dibutyl phthalate (DBP), Benzyl butyl phthalate (BBP) and Bis(2-ethylhexyl phthalate) (DEHP) between 30 min and 24 h with sampling rates equivalent to 0.009; 0.021; 0.033; 0.085 and 0.003 mL h−1 respectively (R2 between 0.88 and 0.99). The calibrated devices were deployed in 12 marginal lagoons, stretching approximately 330 km along the main river. The extracts recovered from the devices were analyzed by gas chromatography (GC), resulting in the identification and quantification of DEP (0.697–13.7 ng L−1), DiBP (0.100–4.43 ng L−1), DBP (0.014–1.21 ng L−1), BBP (0.218–5.67 ng L−1), and DEHP (0.002–2.24 ng L−1). Despite being frequently identified, DEHP concentrations were well below the maximum established limits, revealing a good water quality in terms of the target PAEs. In contrast, screening the extracts using GCxGC was possible to detect other hazardous pollutants such as pesticides, drugs, and their metabolites. The described device was effective and reliable, providing accurate PAE measurements following short exposure periods. In this sense, its deployment during emergency operations, such as accidental discharges of industrial effluents into natural waters, could continuously and cost-effectively monitor water quality.

Reproductive Biology of the Hybrid Coptodon guineensis x Coptodon zillii within Two Marginal Lagoons Invaded by Macrophytes in South Eastern of Côte d`Ivoire

Hybrids of Coptodon guineensis x Coptodon zillii are omnivorous species with a phytophagous tendency found in most of water bodies of Côte d`Ivoire. This study aims to better understand its reproductive biology and possible influence of macrophytes on the breeding season. A total of 608 fish were caught monthly from September 2017 to August 2019. The overall sex-ratio showed significant predominance of females in Ono (1:1.37; χ² = 7.10; P&lt;0.05) and Kodjoboue (1:1.84; χ² = 28.62; P&lt;0.05) lagoons. The sexual maturity recorded in Ono lagoon for males (148.2 mm, SL) and females (145.3 mm) was slightly higher than that of males (144.4 mm, SL) and females (141.8 mm) in Kodjoboue lagoon. March and August–October (Ono lagoon) and February and July–September (Kodjoboue lagoon) were the most intensive spawning months. The absolute fecundity was higher in Ono lagoon (1472–6116 oocytes) than in Kodjoboue lagoon (1676–4210 oocytes), indicating a better food supply due to the high abundance of macrophytes in Ono lagoon. Oocyte size frequency distributions show oocytes of different sizes, indicating more than one spawning within a reproduction season. These findings might facilitate future studies establishing its potential production and its exploitation and management.

Atoll inland and coastal mangrove climate change vulnerability assessment

Climate change threatens global mangroves, which are already among the world’s most impacted ecosystems. Vulnerability components of exposure, sensitivity and adaptive capacity were evaluated on mangroves of atoll settings on Jaluit Atoll, in the Marshall Islands, assessing spatial changes of mangrove cover 1945–2018/19, sea-level trends 1968–2019, and reviewing available information. Inland mangrove depressions occur on Jaluit, as well as coastal lagoon margin mangroves, and both were assessed using the same methods. Spatial analysis results showed both inland and coastal mangroves have increased in area. Inland mangroves on eight of Jaluit’s islands mostly expanded after 1976 from 40 to 50 hectares, with progradation and tidal creek infill closing lagoon connections. Shoreline mangroves showed 88–100% of transects prograding 0.1–0.51 m year−1 and 0–11.5% of transects eroding 0–0.18 m year−1. Assessment of a combination of aerial/satellite images, literature and on-the-ground photos indicated that the mangroves are in healthy condition. Vulnerability assessment results showed both inland and coastal mangroves to have similar strengths and weaknesses in resilience, with intrinsic areas of vulnerability persisting during increased future sea level rise, limited sediment supply and extremely low elevations.

Padrões sazonais podem influenciar a dieta do lambari Serrapinnus notomelas (Eigenmann 1915)

Abstract: Aim This study investigated whether seasonal variations have an effect on diet composition of Serrapinnus notomelas in a marginal lagoon located under the area of influence of the Tibagi River, Upper Paraná Basin. Methods Samples were carried out monthly between February 2017 and January 2018, and fish specimens were caught with two sieves (2 mm mesh). The volumetric and occurrence method were used to quantify stomach contents. Results A total of 358 stomachs had their contents analyzed. The autochthonous resources were dominant in the diet of S. notomelas in all seasons, with a predominance of algae, detritus and Tecamebas. Meanwhile, plant material was the most abundant allochthonous resource in the diet. Diet composition showed significant differences between all seasons, while in the autumn and summer seasons, individuals showed greater trophic niche breadth, respectively. Conclusions Our results show the great importance of autochthonous resources for the maintenance of the S. notomelas population, and that seasonality can influence the trophic composition in the species' diet. We observed difference in the diet during the seasons and that during autumn and summer, individuals presented a greater breadth of the trophic niche. Thus, our results corroborate with knowledge to the preservation of small fish species, which are fundamental for the trophic network in ecosystems.

ICHTHYOPLANKTON COMMUNITY IN LAGOONS OF THE TAPAJÓS AND TROMBETAS RIVERS, EASTERN AMAZON

We evaluated the structure of the ichthyoplanktonic assemblage (taxonomic composition, abundance, developmental stages, and relationship with local environmental variables) in marginal lagoons located in the clearwater Tapajós and Trombetas rivers, Amazon Basin, Brazil during periods of high water (rising waters and flooding). Samples were collected by means of horizontal drags in the subsurface of the water with a plankton net (300 µm mesh). Sorting, counting, identification of biological material, and classification of embryonic and larval stages were performed under a stereoscopic microscope. A total of 122 eggs and 2,813 fish larvae were captured and distributed in nine orders, 18 families, 20 genera, and 26 species. Of these, more than 75% are considered sedentary or short-distance migrants and more than 50% are of commercial interest. The results revealed fluctuating patterns of abundance and species composition between the lagoons of the two rivers. The ichthyoplankton community in the lagoons consisted mainly of larvae of native pelagic fish belonging to the Engraulidae family and larvae of benthic fish such as Eleotridae, making up more than 85% of the individuals captured in the study area. In addition to these two groups, some larvae of piranha species (Pygocentrus nattereri) stood out due to their high densities in the Tapajós river lagoons and croaker larvae (Plagioscion spp.) in the Trombetas river lagoons. The highest larval densities were recorded during the night with significant variations recorded in species composition. The presence of all stages of larval development indicates that these biotopes enable growth and are essential for the biological recruitment of fish species in the region. The ichthyoplankton showed a low correlation with the limnological variables, however, the patterns of abundance and composition of fish larval assemblages in the lagoons of the Tapajós and Trombetas rivers were preliminarily elucidated, although additional work is needed to assess the effects on survival and recruitment

Sebekia sp. (Eupentastomida, Sebekidae) in Pygocentrus piraya (Actinopterygii: Serrasalmidae) from marginal lagoons of the middle São Francisco River basin, Brazil.

Pygocentrus piraya is an endemic species of the São Francisco River basin. In this study, 342 carnivorous fish were examined, nymphs specimens of Sebekia sp. and its ecological indexes are recorded only in piranhas, of the total of 53 collected from three marginal lagoons of the middle São Francisco River basin: 17 specimens from Curral de Varas lagoon; 15 from Maris lagoon, both of state of Minas Gerais; and 21 specimens from Mocambo lagoon, state of Bahia. The prevalence (P) and mean abundance (MA) of Sebekia sp. nymphs in intermediate hosts were as follows: in Curral de Varas lagoon, P = 11.8%, MA = 0.18; in Maris lagoon, P = 46.6%, MA = 0.47; and in Mocambo lagoon, P = 14.3%, MA = 1.05. Despite the lower number of fish examined from Maris lagoon, this lagoon had the highest number of piranhas (seven) parasitized by Sebekia sp. Pentastomids have zoonotic importance and evaluation of the indirect life cycle of sebekids in lagoons is necessary for defining the intermediate and final hosts involved. This record is novel and stems from collection of piranhas in the marginal lagoons of the São Francisco River, in the states of Minas Gerais and Bahia, Brazil.

New Dinosaur Tracks from the Lower Barremian of Portugal (Areia do Mastro Formation, Cape Espichel)

We present a new tracksite with multiple dinosaur tracks from the lowermost Barremian (Lower Cretaceous) of the Cape Espichel (Sesimbra, Portugal). The tracks are localized on three beds on the top carbonate beds of the Areia do Mastro Formation. Those bioclastic, nodular limestones were deposited in a very shallow subtidal-intertidal, restricted lagoon environment. The track surfaces are very dinoturbated, with a substantial number of tracks. Several tracks assign to sauropods, ornithopods and theropods dinosaurs were recorded. Due to heavy bioturbation and the preservation conditions, it is not possible to define trackways; some preliminary work done on the tracks could disclose some behaviours of their producers. Several species of carnivore and herbivore dinosaurs crossed that large area at different times. Herbivores may have used the lagoon margin as passage between feeding spots, while carnivores frequented the area to hunt in groups or individually.

Centesimal composition and meat yield of Hoplias malabaricus: association with intestinal parasites.

Hoplias malabaricus is a non-migratory fish commonly found in the Mogi Guaçu River basin, mainly feeding on fish, small crustaceans and insects. It forms part of the diet for humans, birds and some mammals. This fish has great nutritional value, with both good quality and good quantities of essential vitamins and amino acids. Regarding parasitic fauna, this fish can host different species of helminths in its gastrointestinal tract. The aim of the present study was to investigate the possible interference of parasitism in the meat yield from H. malabaricus and the centesimal composition. For this purpose, fish specimens were collected from marginal lagoons of the Mogi Guaçu River (Pirassununga, state of São Paulo, Brazil) using hooks and fishing nets. We found that all specimens of H. malabaricus were parasitized by at least one species, including larvae of Contracaecum sp. (Nematoda: Anisakidae). Parasitism did not have any significant influence on centesimal composition, but meat yield was negatively correlated with the abundance of larvae.

The ‘decoada’ phenomenon effect on the Paraguay river water quality, Northern Pantanal

In the Pantanal, during the beginning of the flooding hydrological phase occurs a natural phenomenon called 'decoada'. Characterized by the water quality alteration of the rivers, in floodplain areas and marginal lagoons, with the possibility of significant fish mortality, depending on the changes’ magnitude. For this purpose, throughout a hydrological cycle (July 2018 to June 2019), precipitation, bathymetry and water quality were monitored monthly, in 6 sampling points, to determine, the moment, duration and intensity of the decoada, and its effects on water quality in the Paraguay River, northern Pantanal, near the municipality of Cáceres/MT. The dissolved oxygen (DO) concentration was used as an indicator, in which DO &lt; 3.0 mg/L, during the flood season, was considered indicative of the potential event occurrence. According to the records, there were different hydrological periods, where the flooding and high waters presented DO values lower than in the dry and ebb phases, with a drastic change from October 2018 (DO = 6.37 ± 0.17 mg/L) to November 2018 (DO = 2.78 ± 0.05 mg/L), registering, therefore, in all points, low-intensity decoada. The DO values remained below 5 mg/L, the maximum limit allowed by CONAMA Resolution 357/2005 for class II rivers. From November 2018 to April 2019 in all sampling points, the minimum value was recorded in March 2019 in the bay, with DO = 1.84 mg/L, considered a medium level decoada. The principal component analysis (PCA), proved the results difference of decoada found in the river and the bay, presented with greater intensity and duration in the bay. The parameters that influenced the decoada, according to the PCA, were pH, temperature, precipitation, turbidity and DO.

Presence of organic pollutants in the São Francisco river and its compartments

There has been great concern about the presence of organic pollutants in the environment. These types of compounds can be found in different types of habitats and have long term and deleterious effects on all living beings. The main objective of this study was to verify the presence of organic pollutants in different compartments of the Sao Francisco river. Fourteen sites were sampled since right after its springs till marginal lagoons in Pirapora City. The fine sediment was subject to the soxhlet extraction. The extracts were measured in a spectrophotometer in the absorbance range of 589 nm, which correspond to a yellow spectrum that correspond to the extraction of the organic pollutants. The organic matter of the sediments was measured. There was a positive correlation between organic matter content and the absorbance in the yellow color. However, both organic matter content and absorbance did not correlate with the distance from the spring. Even though was not possible to measure which organic pollutants were present in the sediments of the different compartments of the Sao Francisco river, the results of this study clear indicates the presence of these compounds in the samples. The correlation of the organic matter content and the absorbance showed that the organic matter is a important constituent in the sequestration of the organic pollutants. More studies should be conducted to determine which types of compounds are present in these sediments and if there is transfer of these organic pollutants in the aquatic food chain.