Holocene morpho-sedimentary evolution of Marambaia Barrier Island (SE Brazil)

Barrier islands are sedimentary bodies susceptible to changes in sediment supply, dominant physical processes, and sea level. The aim of this work was to study the sedimentary processes that established Marambaia Barrier Island (SE Brazil) as an elongated sandy body that created Sepetiba Bay. For this purpose, barrier and back-barrier bay environments were analyzed using high-resolution satellite imagery, geophysical and topographic surveys, surface sediment samples and short cores, and radiocarbon and optically stimulated luminescence (OSL) dating techniques. Seven morpho-sedimentary domains were identified: coastal beach ridges, overland flow features, inter-ridge paleo lagoon, bayside beach ridges, marshlands, dune field and tidal wetlands. The results show that Marambaia Barrier Island evolved throughout the Holocene, first under normal regression conditions during sea-level rise, and then by forced regression as sea level lowered to its present position. Concurrent processes related to longshore drift, onshore transport, reworked barrier deposits, eolian transport, bay circulation, and pedogenesis influenced its morpho-sedimentary evolution. Morphological features such as truncated beach ridges, flying spits, and filled channels attest to the occurrence of alternating periods of erosion and accretion, evincing how the morphology of barrier island systems preserves an important archive of environmental changes.

Environmental Surveillance and Characterization of Antibiotic Resistant Staphylococcus aureus at Coastal Beaches and Rivers on the Island of Hawaiʻi

Staphylococcus aureus are human facultative pathogenic bacteria and can be found as contaminants in the environment. The aim of our study was to determine whether methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolated from coastal beach and river waters, anchialine pools, sand, and wastewater on the island of Hawaiʻi, Hawaiʻi, are a potential health risk. Samples were collected from three regions on Hawaiʻi Island from July to December 2020 during the COVID-19 pandemic and were characterized using whole-genome sequencing (WGS). From WGS data, multilocus sequence typing (MLST), SCCmec type, antimicrobial resistance genes, virulence factors, and plasmids were identified. Of the 361 samples, 98.1% were positive for Staphylococcus spp. and 7.2% were S. aureus positive (n = 26); nine MRSA and 27 MSSA strains were characterized; multiple isolates were chosen from the same sample in two sand and seven coastal beach water samples. The nine MRSA isolates were multi-drug resistant (6–9 genes) sequence type (ST) 8, clonal complex (CC) 8, SCCmec type IVa (USA300 clone), and were clonally related (0–16 SNP differences), and carried 16–19 virulence factors. The 27 MSSA isolates were grouped into eight CCs and 12 STs. Seventy-eight percent of the MSSA isolates carried 1–5 different antibiotic resistance genes and carried 5–19 virulence factors. We found S. aureus in coastal beach and river waters, anchialine pools, and sand at locations with limited human activity on the island of Hawaiʻi. This may be a public health hazard.