Spatial and seasonal dynamics of phosphorous and physicochemical variables in the Negro River Estuary (Argentina): a preliminary approach.

Nutrient discharge into rivers and estuaries and the factors that control it need to be further understood to decrease the risk of harmful algae blooms on these ecosystems. Preliminary seasonal physicochemical parameters at six stations along the Negro River Estuary (Argentina) were studied during 2019 (Austral summer, winter, and spring) with high- and low-frequency data. Three of the stations were mainly estuarine-influenced and three were marine-influenced ones. The concentration of phosphate (P), river discharge, meteorological conditions, seasonality, and physicochemical variables were analyzed. Total phosphorus (TP) showed seasonal variations and was higher than previously reported for the upper watershed in all stations in the warmer months, except for the marine control one. Orthophosphate values were also high compared to previous watershed data and changed independently of TP fluctuations. Changing turbidity, water temperature, pH, and conductivity did not appear to have an essential role in phosphorus variations. An unexplained high TP spike in the late spring sample shows the need for further research in the area, while the seawater mixing with P-rich river water could be acting as a dilution agent at the mouth of the river.

Tourism in the COVID-19 context in mesotidal beaches: Carrying capacity for the 2020/2021 summer season in Pehuén Co, Argentina.

As a result of the COVID-19 pandemic, there is an evident decrease in economic activity, especially in the tourism sector. On the southwest coast of the Buenos Aires Province (Argentina), coastal cities base their economy on 3S tourism. In this context, the analysis of social views is crucial for participatory coastal management. As well as the forecast of beach use areas in semi-diurnal mesotidal and low-slope beach conditions, wherein few hours the available beach can double or disappear. Therefore, our objective was to determine the beach's optimal use according to its tides, socio-environmental characteristics, and the perception of the interested parties about the 2020/2021 summer season in the pandemic context in Pehuén Co Beach. We employed camera images (January 2019 and 2020) to obtain the behaviour of normal, spring and neap tides, beach geomorphology, and daily and hourly beach use curves. Online surveys were also conducted with residents, second homeowners, and Pehuén Co visitors about their perception for the 2020/2021 summer season. With this analysis, we were able to divide the beach into four areas according to its potential carrying capacity. During low tide, users' maximum capacity on the beach, respecting sanitary distances, may be 6400 people. Meanwhile, at low tide, this number may rise to 34,000. This information is essential for coastal management after the COVID-19 irruption to ensure maximum efficiency in using the beach maintaining a safe social distance.

Assessment of surf zone environmental variables in a southwestern Atlantic sandy beach (Monte Hermoso, Argentina).

The aim of this study was to investigate the temporal dynamics (monthly/tidal) of water temperature, salinity, chlorophyll-a (chlo-a), suspended particulate matter (SPM), particulate organic carbon (POC), and dissolved nutrients in the surf zone of Monte Hermoso sandy beach, Argentina. We also aimed to understand the underlying mechanisms responsible for the observed variability. Sampling was carried out approximately monthly (September 2009-November 2010), and all samples were collected in a fixed station during high and low tide. Water temperature showed a clear seasonal variability (July: 9 °C-December: 26.5 °C) and a thermal amplitude of 17.5 °C. Salinity ranged from 33 to 37, without a pronounced seasonality. SPM (10-223 mg L(-1)) and POC concentrations (399-6445 mg C m(-3)) were high in surf zone waters. Chlo-a (0.05-9.16 µg L(-1)) was low and did not evidence the occurrence of surf diatom accumulations. Dissolved nutrient concentration was quite fluctuating. None of the variables seemed to be affected by tidal stage. The results showed how fluctuating the physico-chemical and biological variables can be in this particular system. The observed variability can be related with local beach conditions but also with regional processes. The study area is highly influenced by a neighbor estuary and as a consequence, could be vulnerable to their seasonal and inter-annual dynamics. All of these characteristics must be considered for further studies and planning of the uses of natural resources and should be taken into account in any environmental monitoring program conducted in a similar beach system.