Estuarine Complex Research Articles

Patterns and Variabilities in the Microphytoplankton Assemblage in a Tropical Estuarine Complex Along the Southwest Coast of India

Patterns and Variabilities in the Microphytoplankton Assemblage in a Tropical Estuarine Complex Along the Southwest Coast of India

Relações peso-comprimento de peixes de um estuário do Banco dos Abrolhos, Brasil

Abstract: Aim We investigate the length-weight relationship estimates of seventeen species caught using an artisanal purse seine in the Abrolhos Bank, a tropical estuarine complex in eastern Brazil. Methods From February 2012 to November 2013, fish were collected monthly using an artisanal small purse seine with a total of 84 fish landings. The fish were captured in mangrove margins during high tide and retrieved after six hours at depths ranging from 1.2 to 3 meters. Results A total of 4433 fish specimens from 17 species and nine families were sampled. The coefficient of determination ranged from 0.904 for Centropomus parallelus to 0.987 for Lutjanus cyanopterus. Species presented allometric growing, with Caranx latus, Lutjanus cyanopterus and M. curema exhibing negative allometric while all the other species presented positive allometric growing. We present first data in Brazil to L. cyanopterus and first data in the literature to Lutjanus alexandrei. Conclusions Our results provide novel data of biological attributes for 17 species. By understanding the length-weight relationships and growth patterns of these species, data at stock level may subside proper management initiatives such as fishing restrictions in fishing sites or seasons and mesh size limits.

SPATIOTEMPORAL CO-OCCURRENCE PATTERNS OF DEMERSAL FISHES IN A SUBTROPICAL MARINE AND ESTUARINE ENVIRONMENT

In order to investigate spatiotemporal co-occurrence patterns of demersal fishes from the Paranaguá Estuarine Complex (PEC) and the adjacent continental shelf, state of Paraná, Southern Brazil, fish from nine sampling sites within the estuary and three additional sites in open sea (N = 12 sampling sites) were sampled at quarterly intervals between 2014 and 2016. The assemblage structure was evaluated by the C-Score index and null models developed through 5,000 randomizations. Species co-occurred as expected, but a general pattern in both temporal and spatial matrices was only detected in the Upper sector, which showed a random co-occurrence pattern. In contrast, fish species from the other sectors co-occurred less than expected by chance in some circumstances. According to the concepts related to the organization of communities on temporal scales, many communities tend to become disorganized after disturbances and then present a progressive increase in organization, that is, they display a random co-occurrence pattern, similar to initial response, and over time the species in the community segregate or aggregate in response to system stability restoration. Therefore, understanding how fish assemblages are structured at different spatial and temporal scales, and especially what processes drive such conformations, including assembly rules for communities, is crucial for ecosystem maintenance and understanding, as well as providing baselines for conservation and management policies, interventions, and practices in these environments.

Inferring ecological connectivity between populations of Opsanus beta (Goode & Bean, 1880) from the southern Gulf of Mexico and the South-western Atlantic coast

AbstractOtoliths are an excellent tool in studies on ecological connectivity of fish species populations. Opsanus beta is an invasive species introduced on the Brazilian coast, but not native from the Gulf of Mexico. The present study aimed to compare the otolith contours of specimens collected in Mexico (Celestún, CEL) and in two Brazilian estuaries (Santos Bay, STB, and Paranaguá Estuarine Complex, PEC). In the laboratory, 99 otoliths were extracted, photographed and compared using wavelet analysis. The otolith contours varied between sites (39 from CEL, 26 from STB and 34 from PEC). The linear discriminant analysis correctly reclassified 87.9% of otoliths by sites, with the best reclassifications in the CEL (97.36%), followed by PEC (88.23%) and SBT (73.07%). MANOVA showed significant differences in otolith contours between sites (F = 5.37; P < 0.005). The otolith contour from CEL was significantly different from those from the PEC and SBT. However, the otolith contour of the two Brazilian estuaries did not significantly differ among them (MANOVA, P > 0.005). Our results indicate O. beta populations on the Brazilian coast are connected, and probably isolated from the Mexican population.

End-member modeling and sediment trend analysis as tools for sedimentary processes inference in a subtropical estuary

Mathematical models based on grain size data enable identifying sediment transport sources and processes in coastal regions, helping to understand the relationship between hydrodynamic and sedimentary processes. This study applied End-Member Analysis and Grain Size Trend Analysis to a grain size database from the Paranaguá Estuarine Complex (PEC), a subtropical estuary in southern Brazil. The end-member analysis allowed identifying three grain size populations, whose spatial distribution is influenced by the dynamics between river discharge and tidal currents acting in the Paranaguá Estuarine Complex. The end-member 1 — formed by finer sediments — is mainly distributed over Antonina Bay and extends into the maximum turbidity zone. The Grain Sized Trend Analysis revealed that these sediments — derived from the weathering of rocks from the Serra do Mar mountain range system — are transported in the west-east direction by river discharge, mainly from the Cachoeira and Nhundiaquara rivers. Furthermore, our results indicate that sediments from end-members 2 and 3 — which are coarser — are distributed in the Paranaguá and Laranjeiras Bays. The transport of these sediments happens towards the center of the estuary due to wave- and tidal-generated currents.

Health conditions of Guiana dolphins facing cumulative anthropogenic impacts

Coastal areas are associated with anthropogenic activities and stressors that can expose the marine fauna to negative cumulative impacts. Apex predators, such as dolphins, can flag the quality of their environment through health parameters such as cutaneous and body conditions. We examined the potential relationship between environmental conditions and health parameters of Guiana dolphins around a port and a conservation unit within the Paranaguá Estuarine Complex, southern Brazil. During boat surveys between July 2018 and April 2019 covering both areas, we measured environmental parameters, photographed dolphins to infer their health condition and the frequency of use of the estuary. In total, 204 individual Guiana dolphins were photo-identified, 52 of which were seen in both years. In general, dolphins showed poor body condition (76% classified as emaciated or thin in 2018, and 79% in 2019), diverse cutaneous conditions (four types of lesions suggestive of an infectious aetiology, two conditions suggestive of traumatic events of anthropogenic origin, and two anomalous pigmentation) and a high prevalence of such cutaneous conditions (85% in 2018, 70% in 2019). Most individuals maintained their body and cutaneous conditions between the two years. There were no clear differences between the port and the conservation areas in terms of environmental conditions, frequency of use and health conditions of individual dolphins, suggesting that dolphins inhabiting this estuarine complex are exposed to potential cumulative impacts, such as pollutants, noise and habitat degradation. This study provides baseline information on some health parameters of Guiana dolphins in southern Brazil and highlights the need for systematic, long-term health assessment of Guiana dolphin populations to guide conservation actions to safeguard this vulnerable species.

Geotechnical characterization of the estuarine deltaic deposits in the Guayaquil city through in situ and laboratory tests

According to previously available research and seismic microzonation studies a large area of the Guayaquil (Ecuador, South America) sits on estuarine deltaic deposits which consist of weak and highly compressible clays with diatoms. The nature of these fine-grained deposits may determine difficulties in a proper estimation of the soil properties. In this respect, the paper provides a detailed geotechnical and geophysical characterization of these soft clays, carried out in the estuarine complex of the Ecuadorean city. Borehole logs, standard penetration tests (SPT), piezocone tests (CPTu), a seismic dilatometer test (SDMT), a non-invasive geophysical survey, and laboratory tests were performed and then compared to analyze the static and dynamic geotechnical parameters of these deposits. The interpretation of the results highlighted the higher reliability of CPTu and SDMT rather than SPT and characterization lab testing to estimate soil shear strength, compressibility and stress history due to the soft nature of these clays, underlining also a certain sensitivity to the presence of the diatoms.

Microbiological quality of the water in collection areas and the tissue of Mytella falcata-Cananéia (SP, Brazil).

Changes in fauna and abiotic factors in estuaries are a consequence of their exploitation; thus, bivalve mollusks, as they filter, are widely used as environmental bioindicators. The aim of this study was to analyze the existence of seasonal variation in the concentration of total coliforms (TC) and thermotolerant coliforms (Ct), in addition to correlating the data obtained with the salinity and temperature in collection areas of Mytella falcata and the soft tissue cultivated in the Estuarine Complex of Cananéia. Two biweekly samples of water and tissue were taken, for 12 consecutive months, in nine cultivation areas of M.falcata. The analysis of the water samples showed that the Fisheries Institute, Mosquiteiro, and Itapitangui have high TC densities, with respective annual averages of 772.22, 592.67, and 563.75 most probable number (MPN).100 ml-1 . The highest concentrations of TC and Ct occurred in the summer, in most areas. There was a decrease in both TC and Ct with increasing salinity. However, there was an increase in Ct with increasing temperature. The soft tissue showed TC densities from 9 to 26 MPN.100 ml-1 and Ct densities from 6 to 14 MPN.100 ml-1 , displaying the highest counts in the summer. Places where coliforms were found in high concentrations could indicate contamination, because Ct do not support higher salinities for a long time. PRACTITIONER POINTS: The general mean was 77.64 (total coliforms) and 39.35 (thermotolerant) MPN.100 ml-1 . Annual average (thermotolerant) exceeded the permitted Brazilian limit in five points. Higher concentrations of total and thermotolerant coliforms occurred in the summer. In mollusk's tissue, concentrations of thermotolerant were 6.30 to 26.16 MPN.100 g-1 . Coliforms' MPN varied with increasing salinity and temperature.

Sedimentological archives of coastal storms in South-West Wales, UK

High magnitude coastal storms have persistently threatened human communities and environments. In the British Isles their frequency and magnitude are predicted to increase in the future with advancing climate change. This study analyses sedimentological evidence from south-west Wales to assess the impacts of high magnitude coastal storms in vulnerable coastal saltmarshes in the Three Rivers Estuarine Complex, Carmarthen Bay. Storm surge saltmarsh deposits were identified following geochemical and particle size analyses and dated using radionuclides 137Cs and 210Pb. The sedimentological evidence is compared with regional tidal gauge and meteorological records to assess variability in storm recording and corroborate the storms which produced the sedimentological deposits. Three episodes of high magnitude saltmarsh storm surge deposition are identified in 1954, 1977 and 1981. Evidence of storm erosion or alternative forms of storm deposition were not present. The sedimentological evidence highlights the comparative rarity of major depositional events in the saltmarshes between 1929 and 2019. The recorded depositional events combined with organic accretion have contributed to maintaining saltmarsh elevation relative to sea level.There remains uncertainty surrounding the storm impacts on the saltmarshes of the Three Rivers Estuarine Complex. When the future 21st century threats of increasing regional atmospheric storminess and sea level rise are considered along with predictions of saltmarsh degradation, this study suggests further research is required to explore the sedimentological storm impacts. This could contribute to sustaining the vulnerable coastal saltmarsh environments and the important ecosystem services they provide.

Citizen science as a tool for understanding the silent dispersion of toadfish Opsanus beta (Goode and Bean, 1880).

Citizen science is an excellent tool in studies of the spatial distribution of non-native species. In Brazil, Opsanus beta has recently been introduced. Studies indicate the occurrence of this species in five estuaries off the Brazilian coast (Guanabara Bay, Sepetiba Bay, Santos Bay, Paranaguá Estuarine Complex and Guaratuba Bay). The present study aims to understand the dispersion of this species on the Brazilian coast through citizen science. Between January and May 2021, information about O. beta was weekly posted in 32 recreational fishing Facebook groups. Sixty-five fishers reported catches of O. beta in estuaries (Guanabara Bay, Sepetiba Bay, Santos Bay and Paranaguá Estuarine Complex). In addition, there were reports from other shallow areas outside adjacent estuaries (Bertioga and Peruíbe, in Sao Paulo State) and the first occurrence record for Laguna (Santa Catarina State), a southern estuarine zone (28° 29' 45″ S to 48° 45' 36″ W). In four estuaries along the Brazilian coast where O. beta was recorded, there are internal ports that trade with countries from the Gulf of Mexico and Caribbean Sea (species original range), indicating ballast water as a possible introduction route. In Laguna, the introduction may have occurred by maritime cabotage services. The reproductive capacity, the aquarists' interest, the absence of introduction policies aimed at this species and the cabotage fleet transportation may be factors that help further extend the dispersal of O. beta on the Brazilian coast.

A first assessment of microplastic abundance in sandy beach sediments of the Paranaguá Estuarine Complex, South Brazil (RAMSAR site)

Here we present the first assessment of microplastic (1–5 mm) abundance in drift line sediments from nineteen sandy beaches at the Paranaguá Estuarine Complex, a subtropical estuarine system from South Brazil. This estuarine system harbors Brazil's second-largest grain port, the Guaraqueçaba Environmental Protection Area, and a RAMSAR site. Sediment samples were washed through a 5 and 1 mm mesh sieve and then visually inspected. We found a total of 398 microplastic particles, of which the majority were foams (63.7%), hard plastic fragments (13.8%), paint fragments (12.8%), and pellets (7.2%). Almost all sampled beaches, including those located within the Guaraqueçaba Environmental Protection Area, were contaminated by microplastics. The most likely microplastic sources for the Paranaguá Estuarine Complex beaches are urban and port activities. However, small communities and marine sources may also contribute to microplastic presence.

Пространственно-временна́я изменчивость гидрохимических показателей водной среды Обской и Тазовской губ

The Gulf of Ob and Taz Bay are components of a special geographical object — Ob-Tar estuarine area. They are intensively used by companies, which produce natural gas and oil in the Yamal Region. The aim of the study is to assess the spatial patterns and temporal dynamics of the priority hydrochemical characteristics of the Gulf of Ob and Taz Bay. The data of the Arctic estuarine expeditions (1968—1989) and complex expeditions (2012—2013), organized by the Arctic and Antarctic Research Institute, are used as the research materials The authors have analyzed hydrochemical characteristics: pH, salinity, dissolved oxygen, silicon and phosphorus compounds. In summer-autumn period 2012—2013 there was a significant seawater intrusion to the south of the Gulf of Ob, caused by a small runoff of rivers the in these dry years. Dissolved oxygen distribution is determined by seasonal variability. In summer-autumn period the average values of more than 7 mg/l were observed. In winter, in the southern part of Gulf of Ob and Taz Bay there was an extreme oxygen deficit, dissolved oxygen values dropped below 1 mg/l. A tendency for a decrease in the content of silicon and phosphorus compounds from south to north was noted. Concentrations of phosphorus-containing compounds in the whole water area were low. The condition of Taz Bay and southern part of the Gulf of Ob is mainly determined by the river runoff and the hydrochemical regime in the area. In the period of high waters the regime has features inherent to rivers, and in the period of low flows — to lakes and reservoirs. Large-scale interference in the ecosystem of Ob-Taz estuarine area recently requires regular hydrological-ecological observations at coastal stations and along the water area sections.

Age, growth, and ontogenetic variation in the sagitta otolith of Opsanus beta (Goode & Bean, 1880), a non-native species in a wetland of international importance

Invasive species are among the most important problems for biodiversity conservation worldwide, particularly in megadiverse countries such as Brazil. However, there is no biological information to develop policies for managing invasive species populations in many cases. The life history parameters and otolith variations are essential to understanding the adaptations of the species introduced in marine environments. This study aimed to identify the age structure and ontogenetic variation in the sagitta otolith of Opsanus beta. Fish samples were obtained monthly in the Paranaguá Estuarine Complex (PEC), south of Brazil. The shape indices verified ontogenetic variations in the otoliths (PERMANOVA; F = 110; P < 0.0001), but no sexual variations were observed in the shape of the otoliths (PERMANOVA; F = 3.65; P > 0.05). Specimen aged between 1 to 9 years were observed in the PEC, with the highest occurrence of individuals between 3 and 6 years (78%). No sexual differences were observed between the ages by the Kimura test. Our results confirm that the O. beta population is well established with age groups similar to that observed in the region where the species is native.

Relationship between fish assemblage structure and predictors related to estuarine productivity in shallow habitats of a Neotropical estuary

Abstract The variability of fish assemblage structure with respect to seasonality in salinity and productivity remains to be elucidate to many Neotropical estuaries. In this study, we hypothesized that salinity gradient and a set of variables related to ecosystem productivity drive community parameters in the shallow-water fish assemblage of the north-south axis of the Paranaguá Estuarine Complex (Southern Brazilian coast). Samples were taken with beach seine monthly from May 2000 to April 2001. Supporting our hypothesis, richness and abundance increased with turbidity, warmer waters of the rainier summer seasons, which are more productive. This environmental setting favors reproduction, as well as juvenile recruitment and growth, whose intensities are highest in this period. Highest abundance was found in inner areas, which may be explained by greater food and habitat availability. Richness was higher in more saline waters, due to the proximity of the rich pool of marine fish species. We suggest that local human interventions (e.g., dredging) should be avoided during the rainy seasons that are critical for species life cycles. Salinization, low estuarine productivity, and warmer waters, which are expected with climate change and human impacts in the local watershed, could affect the integrity of the local fish assemblage.

Mapping of the Sedimentary Facies of the Bottom of the Ouladine Lagoon in Grand-Bassam (Ivory Coast_West Africa)

The Ouladine lagoon has an irregular bottom lined with different substrates. The lithological characteristics make it possible to observe sediments ranging from silts to sands and mixed sediments of variable color. These different fractions have varying proportions. The coarse fraction (>63 μm) has percentages ranging from 0 to 77% and the fine fraction ( μm) from 22.46 to 100% in the different sediments collected. The minority fraction of fine sands occupies the northern banks where the greatest depths of the section parallel to the coastal strip are observed. On the other hand, the sandy fractions occupy the southern shore up to the vicinity of the Azuretti mangrove island. This sandy fraction is also present on almost the entire section from the Comoé-Ebrié lagoon confluence to the closed mouth. The grain size characters of the sediments, such as the diagram of the classification coefficient So and the mean Mz, show well-classified sands. These sediments are deposited in a slightly agitated environment coming mainly from dunes and rivers. The sands of the estuarine complex were emplaced by saltation for most samples and by rotation.

A Quinquennial Multivariate Monitoring of the Brackish Water Zone of Hooghly Estuary, Northern Bay of Bengal, India

A quinquennial study (Mar'2010-Feb'2015) was undertaken to comprehend the interrelationship of the selected ecological variables in the lower Hooghly estuarine complex. The yielded data pointed out that there was a paradigm shift after in the year 2013 as the real time data revealed considerable changes in mean before and after that period. A total of 19 variables were considered for the study among which 4 were ecological indices derived. From the extensive study it was evident that variables such as dissolved nutrients, pH, water temperature, air temperature, turbidity, wind speed, relative humidity and precipitation etc were all influential on the population density of phytoplankton [r-values ranging from -0.99 to +0.95 @ 95% confidence level; p-values of upto +0.99]. A 'single factor ANOVA' was performed on the normalized data sets, the 'Null hypothesis' was rejected. To detect the set(s) where the differences in variances of means lie, two sets of t-tests were performed (assuming equal and unequal variances) where in both the cases the 'Null hypothesis' was rejected. A multivariable regression analysis was also performed [Multiple R:+0.9004; R Square: 0.8107; Adjusted R Square: 0.7519; Standard Error: 3.1117; Observations (n): 60, at 0.05 level of significance] and the generated equation is as follows: NPP = [+47.0402] + (-0.1054) Rh + (-0.0056) Precpn. + (+0.4871) WS + (0.4080) pH + (+0.2870) Sal + (+0.2006) D. O. + (-0.9625) aT + (+0.7120) wT + (-0.0340) Turb + (+0.0068) NO3 -N + (+0.4755) PO4 -P + (+0.0109) SiO4 -Si + (-0.6815) Chl a + (+0.0005) Den.

Protected Areas approach in the Brazilian EIA system: quality of Terms of Reference and Environmental Impact Statements of major projects in a remnant of the Atlantic Forest

Several initiatives emerged to deal with environmental problems, such as Protected Areas and Environmental Impact Assessment, spread worldwide. The coast of Paraná State, southern Brazil, is 82.6% covered by protected areas to conserve the remnants of the Atlantic Forest and its associated ecosystems, whereas port activities date back to the colonial period and remain important, demanding expansions. The present study evaluated the Protected Areas' approach given by environmental licensing processes of port and industrial projects surrounding the Paranaguá Estuarine Complex. To this end, two checklists assessed the Terms of Reference (TR) and the Environmental Impact Statements (EIS) to classify them. EIS turned out to be of average quality, although they fulfilled about 70% of the Terms of Reference requirements. The point is that the TR are indeed poor.

Anthropogenic influences on sedimentary geochemistry of Itapessoca Estuarine Complex, Pernambuco, Brazil.

The Itapessoca Estuarine Complex is characterized by a history of intense economic activities developed on the banks of its tributary rivers, often exercised without any control or planning. In order to relate natural and/or anthropic events to the sediment age, radiometric dating method was performed by determining excess 210Pb in the sediment using the proportional gas flow technique. To investigate possible disturbances in recent sedimentation processes in studied area, 20 surfaces sediment samples and 2 sediment cores were collected for determination of concentrations of the chemical elements. Al, Ca, Fe, K, Mg, Mn, Ni, Pb, Si, Sr, Ti and Zn concentrations were determined by the energy-dispersive X-ray fluorescence (EDXRF) technique. Through the enrichment factors and ratios among some elements associated with geochronological data, it was possible identify geochemical changes in sedimentation of sampled points, with increase of minerals associated with fine fractions and decrease of the proportions of elements associated with coarse fractions. The radiometric dating reveals that Pb enrichment and the exacerbated increase of Ca and Sr enrichment factors are strongly related to the anthropic activity in the region.

TEMPORAL CHANGES IN LENGTH-WEIGHT RELATIONSHIPS OF SCIAENIDAE (PISCES: TELEOSTEI) SPECIES IN SOUTH BRAZIL

This study reports the importance to evaluate the length-weight relationships (LWR) across the years. We evaluate the LWR for 8 Sciaenidae species of Paranaguá Estuarine Complex, South Brazil, sampled between 2016 and 2018 by bottom trawls similar to the used by artisanal fisheries in this region. There were differences between growth type among the years for 5 species, and all species showed differences in the slope of LWR in at least one year. These results show the importance of fauna and fisheries monitoring programs to better evaluate the population dynamics and fisheries stocks.
 Keywords: estuarine fish, fisheries biology, marine fish, sciaenid, weight-length relationship

Socio-Environmental Vulnerability of Water in the Estuary of the Metropolitan Region of Santos (Brazil)

Abstract Santos and São Vicente Estuarine Complex (SSEC) is a densely populated coastal area that houses the main port in Latin America and the most prominent Brazilian industrial complex. Irregular occupations in preservation areas result in a disorderly increase in population, with negative social and environmental impacts. We evaluated the average annual growth of 74 slums occurring in this area and variations in water quality from 2005 to 2018. We monitor the growth of the occupied areas and estimate their respective populations. The average annual population growth was over 6% per year (p.a.). Invasions of new areas and verticalisation of already occupied areas represent 85% of the growth seen. The monthly polluting loads exceeded 450 tonnes or 2,086,000 m3, compromising the waters and local and regional public health. We strongly recommend re-urbanising the area using the resource savings caused by water loss to reduce the risks of ecosystem degradation, damage to health and disease spread.