Eutrophication disrupts summer trophic links in an estuarine microbial food web

Alternative Conservation Paradigms and Ecological Knowledge of Small-Scale Artisanal Fishers in a Changing Marine Scenario in Argentina

We studied conservation paradigms of small-scale artisanal fishers and other actors involved in the conservation of the Bahía Blanca Estuary (BBE)-a Southwestern Atlantic estuary under anthropogenic pressures (conservationists, NGOs, individuals in the private sector and the port consortium). We focused on the relationship between fishers and non-human entities (e.g., animals, tides, lunar cycles, etc.) from alternative conservation paradigms according to Pálsson's schema (orientalism, paternalism, communalism). We also explored the ecological knowledge of fisher communities to identify possible conservation strategies. Using an ethnographic approach, we identified communalism as the dominant paradigm within the fisher communities as opposed to the paternalistic and orientalist approaches of conservationists and industry employees in the BBE. Fishers demonstrated a broad knowledge on the effects of climate change on fish stocks and pollution on ocean environments and biota, which gillnets avoid catching juveniles and threatened species, and landscape changes over the long-term period, among others areas that could be useful for conservation of these changing coastal ecosystems. We conclude that understanding local perspectives and practices is essential for a democratic exchange among different bodies of knowledge to conserve marine ecosystems.

Spatial distribution of physicochemical-bacteriological parametric quality and water quality index of Gomti River, India

Surface water bodies are vital source of water for human consumption, domestic needs, agriculture, industrial activities, and also for aquatic life and ecosystems. In this study, a stretch of river Gomti was studied at 5 sites in Lucknow for two consecutive seasons during 2019. The physicochemical-bacteriological parameters of water and sediment samples were analyzed, followed by multivariate statistics. Mean values of pH, turbidity, EC, TS, TDS, TSS, DO, BOD, COD, nitrate, phosphate, sulfate, total alkalinity, total hardness, chloride, and fluoride during the pre-monsoon period were 7.4 ± 0.2, 5.2 ± 3.3 (NTU), 444.4 ± 97.4 (µS/cm), 274.6 ± 61.6, 254.3 ± 50.2, 21.9 ± 11, 5.4 ± 1.6, 10.2 ± 5.9, 31.2 ± 13.3, 1.2 ± 0.5, 1.7 ± 1.1, 25.9 ± 3.7, 204 ± 41.8, 146.2 ± 11.5, 15.5 ± 8.7, and 0.5 ± 0.1 mg/l, respectively. The corresponding values during the post-monsoon season were 7.5 ± 0.2, 5.5 ± 3.2 (NTU), 436 ± 75.1 (µS/cm), 273.7 ± 124.2, 209.7 ± 82.5, 63.9 ± 43.4, 5.6 ± 1.6, 15.8 ± 8.9, 39.2 ± 23.5, 5.4 ± 4.6, 1.4 ± 0.9, 25.5 ± 5, 199.2 ± 36.6, 134 ± 8.6, 20.2 ± 8.9, and 1.7 ± 0.2 mg/l, respectively. Concentration of pollutants significantly increased by 5-15% from sampling station S1 (upstream) to S5 (downstream). Enumerations of fecal coliform and Escherichia coli bacteria were low at S1 but significantly higher at the S5 site. WQI ranged from 88 to 345 during pre-monsoon and 159 to 422 during post-monsoon period, indicating poor water quality which was unsuitable for drinking purposes. Strong positive correlations (≥ 0.9) were observed among pH, chloride, phosphate, sulfate, turbidity, conductivity, TS, TDS, BOD, and COD for water samples during both seasons. The data reveals that pollution load increases gradually from upstream to downstream due to the increasing discharge of raw sewage. Regulatory bodies should formulate strict regulations and ensure their implementation for the protection and management of river water quality.

First long-term assessment of metals and associated ecological risk in subtidal sediments of a human-impacted SW Atlantic estuary

The main objective of this article was to profile the metal accumulation, sources, pollution levels and trends during 6 years in a SW Atlantic coastal system (Bahía Blanca estuary). Subtidal sediment samples were taken from six stations with different human impacts, and chemical element analyses were performed using ICP-OES. As a result, metals tended to increase in time and differences were observed between a site profoundly impacted by sewage waters and the rest of the sampling stations. Values range from background levels to those considered toxic for the marine biota, as in the case of Cd and Cu. Besides, the geochemical analyses exhibited low to moderate pollution with probable adverse biological effects. Finally, the physicochemical parameters of the water column like pH and DO significantly decreased in time in all stations and temperature correlated with some metals, indicating a potential interaction.

A "new normality" for small-scale artisanal Fishers? The case of unregulated fisheries during the COVID-19 pandemic in the Bahía Blanca estuary (SW Atlantic Ocean)

The current COVID-19 pandemic is causing health and economic crises worldwide, but consequences are worse for those emerging countries with poor sanitary conditions struggling against economic recessions. Small-scale artisanal fishers (SSAF) should be considered among the "essential workers" since they provide food services; however, the COVID-19 might have altered the normal livelihood and reduced people economic incomes in an already marginalized sector. This situation highlights the fishers' vulnerability, derived from changes in fish stocks caused by climate change, pollution, overharvesting, and informal work (illegal, unreported and unregulated fishing). Therefore, the so-called "new normality" raises big questions about the management of coastal areas and fisheries in developing countries. As a study case, we proposed exploring SSAF from an Argentinian estuary, the Bahía Blanca estuary (SW Atlantic Ocean). Most of them are unregulated after a reconversion program carried out by the local government in 2012. After reviewing the current COVID-19 legislation for coastal fisheries and having virtual encounters with SSAF, we observed they are struggling against the economic crisis caused by the pandemic. According to our observations, imperative measures must be taken to prevent fisheries collapse in the area. In this work, we present a reference point for the post-pandemic management of fisheries that could be considered for emerging public policies.

Chemically unidentified dissolved organic carbon: A pivotal piece for microbial activity in a productive area of the Northern Patagonian shelf

The biochemical composition and fluorescence properties of DOM were assessed in relation to phytoplankton and major aquatic bacterial clades in a regenerative area of the Argentine Shelf. DOM was mainly of autochthonous biological origin, containing humic- and protein-like substances of medium degree of unsaturation and diagenesis. Biochemical-DOM accounted for 25% of total DOC, being dissolved combined amino acids (DCAA) the dominant fraction followed by free carbohydrates. Phytoplankton was the main source of serine, alanine, and valine, and particulate carbohydrates. Gammaproteobacteria abundance correlated negatively with ammonium and positively with DCAA, suggesting a coupling between ammonium consumption and refractory amino acid production. A preferential utilization of alanine, leucine and threonine as nitrogen source was inferred from the distribution of Cytophaga-Flavobacteria-Bacteroidete in relation with dissolved free amino acids (DFAA). Notably, Alpha- and Betaproteobacteria correlated with the large pool (75%) of chemically unidentified DOC and not with DCAA or dissolved combined carbohydrates. Particularly, Alphaproteobacteria (∼40% of EUB total heterotrophic bacteria) either significantly contribute to the production of the "humic", refractory fraction of marine DOM, or the latter impairs resource control on their abundance. Spatial heterogeneity inherent to coastal-shelf areas drives important regional variability in the biochemical properties of DOM.

Spatial distribution and functional profile of the bacterial community in response to eutrophication in the subtropical Beibu Gulf, China

In this study, we investigated the specific bacterial distribution and the response of bacterial communities to shifts in environmental factors in the subtropical Beibu Gulf, southern China. The abundances of Actinobacteria, Bacilli, Planctomycetia, Thermoleophilia, Anaerolineae, and Synechococcophycideae were significantly higher in high eutrophic samples than in medium eutrophic and oligotrophic samples. Bacterial alpha-diversity was found greater in high eutrophication samples than in the other samples. Besides, Ponticaulis koreensis, Nautella italic, Anaerospora hongkongensis, Candidatus Aquiluna rubra, and Roseovarius pacificus were sensitive to trophic variation and thus could be used as eco-markers. In addition, the relative abundances of functional genes involving carbohydrate and amino acid metabolism were very high among the samples. We also found temperature, Chl-a, TDN and NO₃^- were the main environmental drivers of bacterial community structure. Overall, this study provides new insight into the composition of bacterial community and function response to gradients of eutrophication in Beibu Gulf.