effect of short-term meteorological disturbances on the submerged aquatic vegetation and associated fauna in the Patos Lagoon estuary, southern Brazil

Occluded fronts are naturally cyclogenic areas that have been intensified by global warming. Studies evaluating the effects of occluded fronts in the submerged aquatic vegetation (SAV) and its associated fauna in shallow estuarine areas may provide insights on the impacts of climate change-induced extreme weather events on coastal ecosystems functioning. The present dataset describes data on benthic fauna and flora in the Patos Lagoon Estuary (PLE), in southern Brazil, seasonally obtained during intense occluded fronts. Using a hierarchical sample design, based on Beyond BACI protocols (Before/After and Control/Impact), fauna and flora were sampled before and after four occluded fronts passage throughout 2019.Three habitats were sampled: SAV Meadow, SAV Edge and adjacent Sandflat. A total of 432 macrozoobenthic samples (216 samples for stratum); 216 samples for bellow and aboveground biomass, vegetation coverage, canopy height and marine macrophytes morphology; 144 samples by sedimentology and organic matter; 72 water column depth measurements; and 8 temperature and salinity measurements were collected during the study period. The data is available at the Global Biodiversity Information Facility (GBIF), in Darwin Core standard format (DwC), organized according to the OBIS-ENV-DATA model, with CC-BY-NC-4-0 license for use. The present dataset adds to the comprehension of the temporal variability of estuarine benthic communities in subtropical systems, and how short-term meteorological process can affect zoo and fitobenthic communities in the context of climate changes.

Gauchergasilus euripedesi (Copepoda, Ergasilidae) parasitizing different species of fish from two environments in southern Brazil

The parasitic copepod Gauchergasilus euripedesi (Montú, 1980) Montú & Boxshall, 2002 was described from plankton samples and specimens found in four fish species from the estuarine area of Patos Lagoon, state of Rio Grande do Sul (RS), Brazil. Later, one different fish species was reported parasitized with G. euripedesi in the same locality. Species of Astyanax Baird & Girard, 1854 (Astyanax henseli Melo & Buckup, 2006 and Astyanax lacustris (Lütken, 1875)) and Psalidodon Eigenmann, 1911 (Psalidodon eigenmanniorum (Cope, 1894) and Psalidodon aff. fasciatus (Cuvier, 1819)) were collected in two environments (Pintada Island, municipality of Porto Alegre and Itapeva Lagoon, municipality of Terra de Areia, RS) to investigate their parasites. The copepods found in the gill arches were counted, processed, mounted in permanent slides, and photographed using light microscopy, or processed for observation in scanning electron microscopy. Specimens of P. eigenmanniorum from Pintada Island, A. lacustris and P. aff. fasciatus from Itapeva Lagoon, were parasitized by G. euripedesi, with prevalences of 29.03% (A. lacustris), 10.34% (P. eigenmanniorum), and 9.68% (P. aff. fasciatus). Measurements obtained for specimens of G. euripedesi were similar to those found in the literature, except for egg sacs which were larger in the specimens examined in the present study. In addition to being the first report of G. euripedesi parasitizing species of fish (A. lacustris, P. eigenmanniorum, and P. aff. fasciatus), the results presented here also extend the known geographic distribution of the copepod species.

Dispersion Plumes in Open Ocean Disposal Sites of Dredged Sediment

Management of estuarine systems under anthropogenic pressures related to port settlement and development requires thorough understanding about the long-term sediment dynamics in the area. In an era of growing shipping traffic and of ever larger ships; millions of tons of bottom sediments are dredged annually all over the world and the major question concerning dredging operations is not whether they should be done, because it is obvious that they are extremely important and necessary, but where the dredged sediments can be disposed of with the least possible ecological impact. The present study involves the evaluation of transport trends of dredged material from a turbid estuary disposed of in four different open ocean disposal sites using numerical model techniques, aiming to contribute to minimizing potential environmental impacts and maximizing efficiency of the dredging operation. The study is carried out in southern Brazil, investigating the fate of dredged material from the Port of Rio Grande, located inside the Patos Lagoon estuary. Simulations were carried with the TELEMAC-3D model coupled with the suspended sediment (SEDI-3D) module and incorporating results from the wave module (TOMAWAC) to evaluate the dispersion of the suspended sediment plume and its interaction with coastal currents. This modeling structure proved to be a valuable tool to study the hydrodynamics and sediment transport pathways in estuarine and coastal areas. Results indicate that the natural Patos Lagoon coastal plume was observed under the predominant ebb flows and NE winds, promoting fine sediment entrapment south of the mouth of the lagoon (in front of Cassino Beach). The dispersion plumes in the disposal sites responded to the wind intensity and direction and did not present any transport tendency towards Cassino Beach. Part of the dredged sediment disposed of in the proposed alternative sites located in deeper areas (Sites B and C) left the site and was transported parallel to the coast (SW–NE direction) according to the wind direction (NE–SW). The area where the disposal sites were located took around 4 days to recover from the dredging operation and reach the usual suspended sediment concentrations and the actual Port of Rio Grande Licensed Site for dredged material proved to be the best alternative among the investigated options

Water exchange between estuarine lagoon and sea through a narrow strait: case study of two Brazilian lagoons

<p>The Patos Lagoon, located in the Southern Brazil, is the largest freshwater lagoon in the World (area is 10 360 km2). It is connected with the Atlantic Ocean by a narrow strait, through which saline sea waters inflows to the lagoon and fresh waters of Patos outflows to the sea. Todos os Santos is the second large bay in the Brazil, which area is 1223 km2. It is located in the Northern Brazil, connected with Atlantic Ocean and remains saline during the whole year. Study of these basins represent difference in water exchange mechanisms between small and large estuarine lagoon.<br>Based on year-long in situ data from sea mooring and river gauge stations, as well as wind and precipitation reanalysis data, the influence of local meteorological and hydrological conditions on water exchange of these basins was studied.<br>It was revealed that the distinct seasonal variability of water exchange in Patos is defined mostly by the seasonal river discharge variability, while the variability of local atmospheric circulation does not influence it. Outflows of lagoon waters to the sea are typical during the high river discharge period, while inflows of sea waters to the lagoon are rare and occur under specific wind conditions. During the low river discharge periods, inflows of sea waters to the lagoon are typical, while short-term outflows are induced by increase of river discharge.<br>Meantime, it was found that synoptical salinity variation in Todos-os-Santos is mostly caused by tides, while seasonal water exchange variability is almost generally wind-driven. </p>

Temporal Variability of Suspended-Solids Concentration in the Estuarine Channel of Patos Lagoon, Southern Brazil

The assessment of suspended-solids dynamics is crucial for the effective monitoring of estuarine environments. As the recurring in-situ sampling is usually problematic, the calibration of the backscattering from acoustic Doppler profilers has shown to be a reliable technique to estimate the suspended-solids concentration (SSC) in estuaries and rivers. In this study, we obtained a linear model that provides SSC estimates for the estuarine channel of Patos Lagoon by calibrating turbidity and acoustic data with in-situ concentration samples. The model output was analyzed in terms of its relationship with estuarine hydrodynamics and temporal variability. In this estuary, the supply of suspended solids is known to be due the runoff from its main tributaries, but also through the exchanges between the estuary and the coastal ocean. Both sources provide sediments and organic solids which affect water quality, geomorphology, and harbor operations. Results show that SSC is strongly linked to estuarine hydrodynamics, where concentrations increase with streamflow. During outflow periods, higher concentrations are associated with river runoff, whereas with inflow conditions they are induced by southern and southwesterly winds. However, relationship between SSC and streamflow is asymmetrical, meaning that the largest concentrations are majorly linked to outflow currents and downstream transport.