Patos Lagoon Estuary Research Articles

Long-term trends in the functional structure of estuarine fish assemblages in a subtropical estuary and its relationships with local environmental variability, man-made changes, and climatic drivers

Climate and anthropogenic impacts are prevalent in marine and estuarine ecosystems. Rapid environmental changes have altered biological diversity and the ecological services associated with ecosystems around the world. The consequences of these impacts on estuarine ecosystems are worrying, given that estuaries are essential habitats for maintaining the diversity of species functions, as they act as sources for larger ecosystems through the recruitment and replacement of species. Through long-term standardized monitoring (1996–2019), we evaluated the temporal variability of the functional structure of fish species in a subtropical estuary using Principal Component Analysis (PCA), and their relationship with environmental, climatic, and anthropogenic variables using Generalized Additive Models (GAM). We investigate the hypothesis that natural disturbances associated with El Niño events and anthropogenic ones related with changes in the estuary morphology will lead to a decrease in the diversity of functions of the fish assemblage in the Patos Lagoon Estuary in south Brazil (32°S). Our findings suggest an overall downward trend in the fish functional structure, especially in the second half (2006–2019) of the time series, which seems to be associated with a combination of abiotic effects (salinity and temperature), global climate phenomena (ENSO phases) and anthropogenic impacts (changes in the morphology of the estuarine mouth and its connection with the sea). These findings rise concern considering the current climate change scenario, where phenomena such as El Niño may become more frequent and intense. Therefore, the evidence from this study suggests that extreme natural climatic events in synergy with anthropogenic disturbances may imply biodiversity losses over time and, consequently, loss of ecosystem processes in a subtropical estuary.

Trajectory, fate, and magnitude of continental microplastic loads to the inner shelf: A case study of the world's largest coastal shallow lagoon

The Patos Lagoon estuary is a highly significant ecosystem where freshwater from a vast and densely populated area continuously flows into the Atlantic Ocean by coastal plumes, exporting not only freshwater but also sediment, nutrients, plastics, and other contaminants. In this work, numerical modeling tools together with field data were used to assess for the first time the capacity of the coastal plume to export microplastics (MPs) to the inner shelf under different hydrodynamic conditions. Two field surveys were conducted during plume events to quantify MP concentrations and validate the model approach. A bottom-up approach was employed to estimate the potential MP export from the estuary's domain to the Atlantic Ocean. MP concentration in surface plume waters ranged from 0.20 items m−3 to 1.37 items m−3, confirmed by FTIR as synthetic polymers in a 90 %, being Polypropylene (PP) and Polyethylene (PE) the most abundant in a 73 %. The accumulation pattern was observed on the plume's frontal system, consistent with simulation results. The estimated average MP potential export rate attained 9.0 million items day−1 during moderate plume events and 47.5 million items day−1 during high discharge plume events. Strong discharge events, coupled with intense northeast winds, facilitated rapid southwestward export of MPs. Conversely, moderate to weak discharge events retained MPs closer to the estuary's mouth, enabling either longer trajectories or earlier deposition. Significant MP accumulation hotspots were identified in the gyre between the jetties and Cassino beach, as well as in the saline front within the plume boundaries. These accumulation zones may function as reservoirs for MP particles, potentially posing threats to local ecosystems. Understanding these dynamics is crucial for ongoing monitoring efforts to assess potential harmful interactions over time.

Functional diversity of benthic macrofauna during and after an el niño event in a subtropical estuary

Bioturbation promoted by benthic macrofauna impacts the biogeochemical processes in the sediment and water column, being an important process in estuaries, which are depositional ecosystems of high ecological importance. Functional diversity provides clear connections between biota and environmental variables, enabling researchers to comprehend the structure and functioning of ecosystems. The functional approach is still an emerging field of studies for estuaries, especially in the context of weather events such as the ENSO – El Niño. We investigated the functional diversity on a sandflat in the Patos Lagoon Estuary, regarding the bioturbation related traits of the benthic macrofauna, during and following the 2002/2003 El Niño event. Our study evidenced that the decrease in salinity caused by the high precipitation during the El Niño was the most influential factor affecting the functional diversity of the macrofauna. This led to assemblages with less potential for bioturbation, decreased stability, and higher prevalence of opportunistic traits. We also found that despite using bioturbation related traits for our analysis, the proportions of sand, silt, and clay in the sediment were not the main drivers of changes in the functional indices or trait composition, presenting less influence than the seasonal variation of temperature.

Bioaccumulation of metals in Spartina alterniflora salt marshes in the estuary of the World's Largest Choked Lagoon.

Salt marshes are capable of mitigating metal pollution in coastal environments, yet the efficacy of this remediation is contingent upon various environmental factors and the plant species involved. This study investigates the influence of different anthropogenic activities, including industrial, urban, recreational (in an insular area), and dredging operations, on the bioaccumulation of eight metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) within Spartina alterniflora Loisel. in the Patos Lagoon estuary, Brazil. The research aims to assess the pattern of metal bioaccumulation and distribution within the plant's leaves, stems, and roots while also examining metal presence in the sediment. Our main findings reveal that S. alterniflora exhibited elevated metal levels in its plant structure directly related with the metal concentrations in the surrounding sediment, which, in turn, is related to the different anthropogenic activities. The industrial area presented the highest metal levels in sediment and plant sections, followed by dredging, insular, and urban areas. This same pattern was mirrored for the bioconcetration factors (BCF), with the BCFs consistently indicating active metal bioaccumulation across all areas and for most of the metals. This provides evidence of the metal bioaccumulation pattern in S. alterniflora, with elevated BCFs in areas affected by activities with a higher degree of impact. Translocation factors (TF) showed varying metal mobility patterns within the plant's below-ground and above-ground sections across the different areas, with only Hg exhibiting consistent translocation across all study areas. Zn was the primary metal contributor in all plant sections, followed by Pb and Cu. It is worth noting that Pb is a non-essential metal for this plant, highlighting the relationship between elevated Pb contributions in the plant sections and the bioaccumulation of this metal within the plant's structure. Overall, this study emphasizes the bioaccumulation capacity of S. alterniflora and elucidate the intrinsic connection between different anthropogenic activities and their impact on the resultant availability and bioaccumulation of metals by this salt marsh plant.

Nutrient fluxes, budgets and net ecosystem metabolism in a Brazilian coastal system under drought conditions

Integrated dissolved inorganic nutrient fluxes (nitrite, nitrate, ammonium, phosphate and silicate) between Patos Lagoon estuary (PLE), Brazil, and the inner continental shelf of the southwest Atlantic Ocean, were estimated from averaged water column nutrient concentrations and water fluxes (method 1 – M1). Daily surveys were carried out for 30 days, spanning from Feb-22 to Mar-23 of 2021 during late austral summer drought, at two stations — one next to the estuary mouth, the other in the inner estuary, at the interface between the estuary main channel and a shallow embayment called the Arraial bight. On average, PLE delivered dissolved inorganic phosphorus (DIP), nitrogen (DIN) and silicate outfluxes to the adjacent continental shelf at rates of 22.4 ± 596.1, 89.8 ± 207.3 and 1715.9 ± 3283.2 × 103 mmol m−2 d−1, respectively. Budgets for DIP and DIN were computed by the LOICZ box model approach (method 2 – M2) considering Patos Lagoon divided into its limnic (fresh, mean salinity 2 psu) and estuarine (brackish, mean salinity 18.5 psu) regions. The residual fluxes for DIP and DIN from PLE to the inner continental shelf were similar to those of M1, but the complete budget (M2) revealed that PLE also imported DIP, at a positive exchange rate between PLE and coastal waters. There is evidence that DIP is supplied by Plata Plume Water. Net ecosystem metabolism (NEM) and N-fixation – denitrification were assessed through the LOICZ budgets for DIP and DIN, respectively. Denitrification prevailed in both limnic and estuarine regions. Estimated NEM indicated weak autotrophy in the limnic region, and net heterotrophy in the estuarine region. The net heterotrophy in the estuarine region was mainly attributed to nitrogen limitation due to low allochthonous supply by river discharge, and N-loss by denitrification during austral summer drought conditions.

Temporal patterns in the soundscape of the port area in an urban estuary

Soundscape ecology, facilitated by the collection of environmental sounds, enables the determination of the area used by specific species, estimation of population abundance, verification of habitat health, and assistance in management and monitoring processes. Estuaries are key environments in the life cycle of many species. As coastal ecosystems, they face potential impacts by human activities. This study aims to characterize the soundscape of the Patos Lagoon estuary (PLE), Brazil, examining its temporal and seasonal variations. Additionally, it seeks to investigate the influence of temperature and salinity on sound pressure levels (SPL) across three different frequency bands throughout the year. For data collection, two autonomous devices - a SoundTrap digital recorder and an F-POD sampler - were used. The data collection spanned from September 2020 to August 2021 and covered one consecutive week per season. The analysis of audio files was performed manually using Raven software. Sound emissions by Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) and fish were observed throughout the sampling period, with peak detections occurring during the summer and spring, respectively. Boat noise was detected throughout the year but more intensely in the summer. Generalized linear models (GLMs) revealed that, for the three SPL frequency bands, the season significantly influenced the composition of the PLE soundscape, with positive fluctuations in the warmer seasons (summer > spring > autumn > winter). Salinity, in turn, showed a slightly negative relationship with the SPL values in the three models, suggesting a decrease in frequencies with increasing salinity. Our results also indicate that the low-frequency SPL, originating mostly from various sources of anthropogenic noise, constitutes the main component of the PLE soundscape. In conclusion, our study provides novel insights into the temporal patterns of the soundscape in an urban estuary, including biotic and anthropogenic sounds, and their relationships with selected environmental variables.

First record of Centropomus undecimalis (Bloch, 1792) (Perciformes, Centropomidae), Common Snook, in the Patos Lagoon estuary, in southern Brazil

We report the first record of Centropomus undecimalis (Bloch, 1792), Common Snook, in the Patos Lagoon estuary (32°S), Brazil. Two specimens were caught in April and May 2021 as bycatch in the fyke nets fish-ery for shrimp. Centropomus undecimalis was previously known to occur south to 29° S. We hypothesize that the intensification of the warm Brazilian Current has being promoted an expansion southward of this fish species along the Brazilian coast.

Seasonal variability in water‒air CO2 exchanges and carbon origin in a subtropical estuary

The seasonal and interannual variabilities in the water‒air net carbon dioxide (CO2) flux were investigated in the lower zone of the Patos Lagoon Estuary (PLE), the largest choked lagoon worldwide. The studied region experienced periods of CO2 ingassing (outgassing) during ocean-dominated (riverine-dominated) conditions. During ocean-dominated conditions (summer/autumn), CO2 uptake was an average of −15 mmol m–2 d–1, whereas under riverine-dominated conditions (winter/spring), CO2 emissions prevailed, reaching an average of 22 mmol m–2 d–1. The magnitude of CO2 uptake in summer/autumn was comparable to the CO2 released to the atmosphere in winter/spring in the mesomixohaline zone. However, the CO2 uptake in summer/autumn was 4-fold higher than the CO2 released in winter/spring in the euhaline zone of the PLE. Unlike most estuarine systems, the PLE acted as a net CO2 sink, with a net CO2 uptake of −2 mmol m–2 d–1 during the period investigated (May 2017 to June 2021). The water‒air CO2 exchanges are modulated mainly by the balance between continental freshwater discharge and the inflow/outflow of seawater. However, the combined effect of wind speed, biological activity, and water residence time adds complexity to understanding the carbon exchanges in this region. The higher concentration of organic matter entails the highest estuarine CO2 concentration during autochthonous production, which indicates heterotrophy in estuarine waters. Part of this carbon produced in the estuary is likely exported to the coast, as suggested by the high CO2 concentration in the estuary mouth. The CO2 export from the PLE to the coastal zone appears to make the lagoon resilient to regional anthropogenic CO2 build-up. Owing to the water‒air net CO2 flux range associated with complex PLE biogeochemistry dynamics, further investigations as a long-term time-series program will improve knowledge of regional CO2 exchanges in the context of climate and elucidate the role of large estuaries and coastal bays in the global carbon budget.

Temporal variation in diatom communities associated to sediments of impacted versus non-impacted seagrass meadows of an estuarine lagoon

Microphytobenthos play a key role as food resources at the base of the trophic web, particularly in sediments of highly productive seagrass meadows. Here, we investigated patterns of variation in microphytobenthic diatom communities and their driving factors in an impacted versus non-impacted meadow of Ruppia maritima in the Patos lagoon estuary (Brazil), across seasons in two consecutive years. We found higher taxa richness, diversity and equitability, together with lower dominance, at the non-impacted meadow. Seasonally, the same pattern was found in autumn and/or winter 2017 at both meadows, driven by the lower seawater temperature. Higher richness was related to lower river discharge and equitability to lower wind velocity. Diatom assemblages differed in species presence/absence and abundance between meadows, mostly due to higher phosphate at the impacted meadow, together with higher water transparency and sediment organic matter (2016) and with higher grain size (2017) for species presence/absence. Even diatom assemblages differed more in terms of species abundances than of presence/absence, Paralia sulcata and Tryblionela compressa (commonly reported as indicator of eutrophic conditions) were exclusively present at the impacted meadow, while Amphora charrua, Desikaneis howellii, D. simplex (commonly in undisturbed environments) did so at the non-impacted meadow. Often two species were responsible for more than half the dissimilarities in abundances, with Catenula adhaerens dominating at the impacted meadow and Ambo tenuissimus at the non-impacted meadow. Overall, the combination of natural and anthropogenic environmental factors acted together to determine between-meadow and seasonal patterns of variation in the presence and abundance of diatom species.

Plastisphere composition in a subtropical estuary: Influence of season, incubation time and polymer type on plastic biofouling

Plastics are abundant artificial substrates in aquatic systems that host a wide variety of organisms (the plastisphere), including potential pathogens and invasive species. Plastisphere communities have many complex, but not well-understood ecological interactions. It is pivotal to investigate how these communities are influenced by the natural fluctuations in aquatic ecosystems, especially in transitional environments such as estuaries. Further study is needed in subtropical regions in the Southern Hemisphere, where plastic pollution is ever increasing. Here we applied DNA-metabarcoding (16S, 18S and ITS-2) as well Scanning Electron Microscopy (SEM) to assess the diversity of the plastisphere in the Patos Lagoon estuary (PLE), South Brazil. Through a one-year in situ colonization experiment, polyethylene (PE) and polypropylene (PP) plates were placed in shallow waters, and sampled after 30 and 90 days within each season. Over 50 taxa including bacteria, fungi and other eukaryotes were found through DNA analysis. Overall, the polymer type did not influence the plastisphere community composition. However, seasonality significantly affected community composition for bacteria, fungi and general eukaryotes. Among the microbiota, we found Acinetobacter sp., Bacillus sp., and Wallemia mellicola that are putative pathogens of aquatic organisms, such as algae, shrimp and fish, including commercial species. In addition, we identified organisms within genera that can potentially degrade hydrocarbons (e.g. Pseudomonas and Cladosporium spp). This study is the first to assess the full diversity and variation of the plastisphere on different polymers within a subtropical Southern Hemisphere estuary, significantly expanding knowledge on plastic pollution and the plastisphere in estuarine regions.

Levels and sources of hydrocarbons in the Patos Lagoon estuary and Cassino Beach mud bank (South Atlantic, Brazil): evidence of transference between environments

This study assessed the concentrations and sources of natural and anthropogenic aliphatic (AHs) and polycyclic aromatic hydrocarbons (PAHs) in superficial sediments collected along the Patos Lagoon estuary and in sediment cores obtained from the Cassino Beach mud bank. Levels and distribution of n-alkanes indicate terrestrial sources, overlapping with a low amount of petrogenic hydrocarbons (heavy oils). Unresolved complex mixture (UCM) was observed in all samples. On the other hand, the distribution of PAHs in the sediments showed a predominance of pyrolytic over petrogenic sources. In general, hydrocarbons (HCs) contamination in the Patos Lagoon estuary and its adjacent coastal area can be considered low, except for sites near urban or industrial effluents, where moderate to high levels of contamination were found. Concentrations of hydrocarbons were homogeneous throughout the sediment cores, suggesting that mixing processes may have occurred along the layers or that HCs inputs to the mud banks were uniform during the studied deposition period. In addition, the levels and profile of HCs in the coastal sediments were similar to those observed in the estuary. Moreover, the frequent remobilization of sediments from the mud bank towards Cassino beach does not seem to pose any threats to the local biota or beach users since the levels of contamination were relatively low and below the threshold limits of sediment quality guidelines.

Sedimentation processes in the navigation channel of Patos Lagoon Estuary, southern Brazil

The morphology of estuarine navigation channels varies in time and space. Siltation occurs in areas where flow conditions enable sediment trapping and it limits navigability in most cases, requiring periodic dredging. Identifying sedimentation patterns is fundamental to designing ports to reduce siltation. The Port of Rio Grande, located in the Patos Lagoon estuary, holds strategic significance and it is a key example for understanding the evolution of large estuarine access channels. We used 19 bathymetric surveys from April 2001 to February 2018 to generate Digital Elevation Models and evaluate the evolution in time of bed morphology in the Porto Novo basin and its access channel (located in Port of Rio Grande). Also, we considered hydrological data available from September 2005 to December 2011. Major siltation rates were observed in the northwestern portion of the basin and the convex margin of the access channel, whereas other locations exhibited stable conditions. Channel configuration and position were determinants to define spatial variations of sedimentation processes. Hydrological conditions, mainly when discharge exceeds 4,000 m3/s over long periods, strongly controlled siltation magnitude in the Porto Novo basin and its access channel.

Composição e estrutura da comunidade de diatomáceas bentônicas de marismas do sul do Brasil e sua relação com variáveis ambientais

Abstract: Aim This study focused on the spatiotemporal variation of the benthic diatom community structure in salt marshes from the Patos Lagoon estuary and their relationship with environmental variables. Methods Samplings were carried out in the winter of 2010 and summer of 2011 (during El Niño and La Niña) in sites with different sediment granulometry, salinity, and distances from the Atlantic Ocean. The surface sediment was collected using a core (10 cm in diameter and 2 cm in depth) and the benthic diatoms were removed following the Trapping method, allowing the observation of live diatoms. Results The richness values (18 and 48 taxa), evenness (0.41 and 0.68), and Shannon diversity indices (2.02 and 3.31 bits/ind.) variations were not significative between the sites and seasons, although temperature and salinity differed significatively between winter and summer. However, the diatom's composition and distribution were related to temperature, salinity, and sediment particle size. Mainly the species Hippodonta hungarica, Luticola simplex Navicula cf. cryptotenelloides, N. erifuga, N. jacobii, Nitzschia filiformis var. conferta, Planothidium frequentissimum and Tryblionella calida were associated with lower temperature and lower salinity in the winter. The species Navicula cf. cryptocephala, N. phylleptosomaformis, Nitzschia pusilla, N. frustulum, N. scalpelliformis and Pseudostaurosiropsis geocollegarum were associated with higher temperature and higher salinity in the summer. Birraphid diatom taxa, mainly species of the genus Navicula and Nitzschia, were frequent or abundant in sandy sediments, and monoraphids, such as Planothidium frequentissimum, were frequent in sites where silt and clay predominated. Conclusions The composition of the benthic diatoms revealed variation between the sites in the winter and summer seasons, during El Niño and La Niña episodes. In winter, high rainfall and freshwater runoff maintained oligohaline condition in the marshes, while in summer, flooding with meso-poly-euhaline waters changed the diatom composition. The granulometry was an important factor in explaining the distribution of the birraphid and monorhapid taxa.

Influence of long jetties on estuarine and coastal hydrodynamics in a microtidal estuary

Coastal areas are extremely important regions for social and economic development, therefore vulnerable to human impacts as port settlement and development as well as construction of coastal structures. The aim of this study is to assess changes on estuarine and coastal hydrodynamics due to the construction of long jetties at the Patos Lagoon inlet (Brazil). The Patos Lagoon estuary has a remarkable socio-economic and ecological importance, yet no study focused on the original impact of the jetties construction at its inlet, which occurred between 1911 and 1917. Through the application of a three-dimensional numerical model, we assess its hydrodynamic changes based on pre- and post-jetties scenarios. The TELEMAC-3D was calibrated and validated against in situ measured data. The morphological changes caused by the jetties induced a reduction of the ebb and flood current velocities along the channel, a decrease in the capacity of salt transport, and a reduction in salinity values and saline incursion. The presence of jetties, however, led to the intensification of current velocities in the plume jet and consequently an increase in continental water offshore. The changes presented here for the Patos Lagoon estuarine and coastal areas and the possible repercussions for the maintenance of essential conditions in this environment revealed the importance of evaluating ecological, sedimentary and morphological aspects prior to coastal constructions. Additionally, results of this study highlight the importance of investigating past human-induced impacts in order to provide useful information for future sustainable development works in coastal zones.

Diversity and Variation of Epiphytic Diatoms on Ruppia maritima L., Related to Anthropogenic Impact in an Estuary in Southern Brazil

Knowledge about the diversity and spatiotemporal variability of epiphytic diatom communities in estuarine meadows has great relevance for coastal ecology and, thus, contributes to understanding the impact of natural and anthropogenic changes on seagrass meadows. The community of epiphytic diatoms in Ruppia maritima L. meadows was investigated in two environments with different levels of anthropogenic impact and nutrient loads. Both impacted and non-impacted meadows had similar conditions in terms of water depth, temperature and transparency but distinct nutrient loads and salinity ranges. A total of 159 diatom taxa were found on Ruppia maritima leaves during the monitoring period, including freshwater (30.8%), marine (25.1%), brackish (9.4%) and cosmopolitan (8.8%) taxa. The most abundant species were C. placentula, T. tabulata, M. pumila and T. fasciculata, in addition to A. tenuissimus, C. adhaerens and M. moniliformis. Although present in both sites, C. placentula and T. tabulata were the dominant species in the impacted site. We found that 32% of the taxa were exclusive to the non-impacted site, 23% to the impacted site and 45% were common to both sites. The study sites showed marked differences in community attributes; i.e., higher richness, diversity and equitability and lower dominance were found in the non-impacted site, which is distant from anthropogenic sources of domestic and industrial sewage and has low concentrations of dissolved N and P in water and low values of sediment organic matter. Nutrient concentration and salinity were the main factors behind the spatial and temporal variability in the structure of the epiphytic community when all other environmental variables were similar (water depth, temperature, transparency and host plant). The influence of temperature and salinity on community structure was site-dependent. This study revealed the high richness and diversity of epiphytic diatoms in the meadows of the Patos Lagoon estuary (PLE) and the high spatial and temporal heterogeneity of the communities, and it shows the potential of epiphytic community studies for the assessment of environmental quality in seagrass meadow habitats.

Salt marsh-atmosphere CO2 exchanges in Patos Lagoon Estuary, Southern Brazil

Blue carbon ecosystems are recognized as carbon sinks and therefore for their potential for climate mitigation. While carbon stocks and burial rates have been quantified and estimated regionally and globally, there are still many knowledge gaps on carbon fluxes exchanged particularly at the interface vegetation-atmosphere. In this study we measured the atmospheric CO2 concentrations in a salt marsh located in the Patos Lagoon Estuary, southern Brazil. Eddy correlation techniques were applied to account for the CO2 exchange fluxes between the vegetation and the atmosphere. Our dataset refers to two sampling periods spanning from July up to November 2016 and from January to April 2017. By using time series analysis techniques including wavelet and cross-wavelet analysis, our results show the natural cycles of the CO2 exchanges variability and the relationship of these cycles with other environmental variables. We also present the amplitudes of the salt marsh-atmosphere CO2 fluxes’ diurnal cycle for both study periods and demonstrate that the CO2 fluxes are modulated by the passage of transient atmospheric systems and by the level variation of surrounding waters. During daytime, our site was as a CO2 sink. Fluxes were measured as -6.71 ± 5.55 μmol m-2 s-1 and -7.95 ± 6.44 μmol m-2 s-1 for the winter-spring and summer-fall periods, respectively. During nighttime, the CO2 fluxes were reversed and our site behaved as a CO2 source. Beside the seasonal changes in sunlight and air temperature, differences between the two periods were marked by the level of marsh inundation, winds and plant biomass (higher in summer). The net CO2 balance showed the predominance of the photosynthetic activity over community respiration, indicating the role of the salt marsh as a CO2 sink. When considering the yearly-averaged net fluxes integrated to the whole area of the Patos Lagoon Estuary marshes, the total CO2 sink was estimated as -87.6 Mg C yr-1. This paper is the first to measure and study the vegetation-atmosphere CO2 fluxes of a salt marsh environment of Brazil. The results will contribute to the knowledge on the global carbon budget and for marsh conservation and management plans, including climate change policies.

Seasonal variability of carbonate chemistry and its controls in a subtropical estuary

We performed an unprecedented investigation of the seasonal variability in carbonate system parameters (total alkalinity – AT, total dissolved inorganic carbon – CT, pH, and partial pressure of carbon dioxide – pCO2) in the lower zone of the Patos Lagoon Estuary (PLE), the largest choked lagoon in the world. Sampling was conducted monthly from May 2017 to June 2021. AT and pH were measured during the study period, while other carbonate system parameters were estimated using CO2Sys software. The pH distribution reflected the average natural alkaline conditions throughout the year, with an average of 8.0 pH units. The surface waters in the lower zone of the PLE are generally characterized by a supersaturated calcium carbonate environment. However, a susceptibility to undersaturation conditions was observed during winter (calcite and aragonite) and spring (aragonite). Furthermore, the average surface water pCO2 was 394 μatm during the analyzed period, with the highest values recorded in winter and early spring. The predominant estuarine processes governing changes in the carbonate system in the PLE were the dilution and concentration of salts. These processes depend on the complex balance between freshwater outflows and oceanic inflows that change the surface salinity and produce favorable conditions for primary producer development and the input of continental carbon. However, the remineralization of organic matter and CO2 ingassing likely contribute to the deviations in the theoretical mixing line, causing the increased CT in the region. In addition, the nonthermal effects on seasonal changes in the pCO2 prevail over thermal effects, and the region presents an ocean-dominated (riverine-dominated) condition during summer and autumn (winter and spring). The novel results described here reveal the complexity and challenges that still exist to a better comprehension of how carbonate system parameters evolve temporally and spatially in the PLE, especially considering the climate- and anthropogenic-driven stressors. Finally, this study contributes to the understanding of carbonate system variability in coastal ecosystems and highlights the need for more intense and continuous biogeochemical monitoring of Southern Hemisphere estuaries.

Categorizing estuarine fish assemblages in the Warm Temperate Southwestern Atlantic Province: The case of Patos Lagoon Estuary, Brazil

Classifying organisms into guilds is a good strategy to deal with taxonomic differences, and possibly to compare systems worldwide to address ecosystemic questions. Functional guilds have been used to classify organisms; however different classifications frequently are used for the same species, depending on each author. In order to standardize the guild classification for the Patos Lagoon Estuary, South Brazil, we evaluated its fish assemblage using historical dataset (1979 through 2016). Fish species were classified into guilds covering estuarine use, feeding mode and reproductive strategy. We found 140 Osteichthyes species for this estuary, in that most of the species are marine (58.5%), followed by freshwater (31.4%), estuarine (6.3%), and diadromous (3.8%) species. Concerning feeding mode, most species were classified as zoobenthivores, followed by piscivores and zooplanktivores, with some species presenting ontogenetic variation in their feeding habits. The average trophic level of this fish assemblage was estimated in three. Regarding reproduction, oviparity was the main reproductive mode, with pelagic eggs in the marine species, and settled eggs in the freshwater species. We provided an updated and unified list of Osteichthyes from Patos Lagoon Estuary, with all species classified in standardized guilds, assisting future studies that aim at analyzing estuarine assemblages in the Warm Temperate Southwestern Atlantic Province, as well as worldwide.

Patos Lagoon estuary and adjacent marine coastal biodiversity long-term data

Abstract. Estuaries are among the most productive aquatic ecosystems and provide important ecological and economic services in coastal areas. However, estuarine systems have been threatened worldwide by natural and anthropogenic impacts acting on local, regional, and global scales. Long-term ecological studies contribute to the understanding and management of estuarine functioning and provide the baseline information for detection changes and modeling of predictive scenarios. Here, we describe long-term data on the biodiversity and physico-chemical parameters obtained from 1993 to 2016 for the Patos Lagoon estuary and adjacent marine coast (PLEA), in southern Brazil. We report 8 datasets containing 6972 sampling events with the occurrence and abundance records of 275 species (kingdoms: Bacteria, Protozoa, Chromista, Plantae, and Animalia) of functional groups plankton, benthos, and nekton. Datasets also include 22 190 abiotic records. The database is published in the Global Biodiversity Information Facility (GBIF) repository (see Sect. 3 “Data availability” and Table 3). The present compendium represents one of the most comprehensive and longest datasets from primary producers to top predators in an estuarine coastal system in South America, and their availability will be an important contribution to the understanding and predictability of estuarine dynamics around the world.

Spatial zoning to conserve fish species with complex life cycles in estuaries

Fish conservation in estuaries is complex because there are diverse social values and interests associated with estuarine ecosystems and multiple ecological processes (e.g., nursery, connectivity, and population dynamics). Furthermore, ontogenetic shift has an important role in determining fish habitat use (e.g. pelagic vs benthic environments), and consequently, critical implications for conservation. Here, we develop a prioritisation approach to create conservation zones in an estuarine system that considers fishery costs while also integrating pelagic and benthic habitats for different life history stages (from eggs to adults), and multiple conservation objectives. We applied our approach to the whitemouth croaker Micropogonias furnieri in the Patos Lagoon estuary (Brazil) and tested four scenarios based on different objectives, zone types and targets. In this study, we used Marxan and Marxan with Zones and accounted for 41 conservation features (including habitat type, vegetation and seasonal distribution of whitemouth croaker within the estuary). Overall, we found two important results. First, spatial priorities for the no-take and partially protected zones did not change substantially and were very robust to variation in uncertain parameters. Second, an integrated conservation plan with multiple zones requires less area to be designated as no-take zone than a traditional conservation plan with a single zone. A well-designed conservation plan based on multiple life stages may help to ensure the recruitment, persistence and management of important estuarine resources.