Microplastics in the Amazon biome: State of the art and future priorities

Microplastics (MPs) have been identified as a major potential threat to the biota and human health. Despite the exponential increase in MP research worldwide, few studies have focused on the extensive Amazon biome. To assess research priorities, the present study reviewed and summarized the available scientific knowledge on MPs in the Amazon, in addition to analyzing population and waste-management data, to evaluate potential sources of MPs in the hydrographic system. Poor sanitation conditions are a main source of MPs for the vast hydrographic basin, and, consequently, for the adjacent ocean. Secondary MPs predominated, mostly fibers (96% of debris), composed of polyamide (32%). Mean MP concentrations ranged from 0.34 to 38.3 particles.individual-1 in biota, 5 to 476,000 particles.m-3 in water, and 492.5 to 1.30848 × 107 particles.m-3 in sediment, values in close comparison with those found in areas profoundly affected by anthropogenic pollution. MPs were widespread in a range of Amazonian environments and species, and negative effects are probably occurring at various ecological levels. However, limited research, methodological constraints, flaws and the lack of standardization, combined with the continental dimensions of the Amazon, hampers the collection of the fundamental knowledge needed to reliably evaluate the impacts and implement effective mitigation measures. There is an urgent need to expand scientific data available for the region, improving local research infrastructure, and training and deploying local researchers.

Marine debris provide long-distance pathways for spreading invasive corals

Anthropogenic marine debris and invasive species are pervasive in the ocean. However, research on the mechanisms and dynamics controlling their distribution in marine systems (e.g.; by floating debris acting as vectors for invasive species) is limited. Applying a numerical modeling approach, we demonstrate that rafting invasive corals (Tubastraea spp.) can be transported over long distances and reach important tropical receptor regions. In <180 days, buoyant debris can cover distances between 264 and 7170 km moving from the Brazilian semiarid coast to the Amazon coast and reaching eight regions in the Wider Caribbean (mainly the Eastern Caribbean and Greater Antilles). Analyzing 48 simulated scenarios (4 years × 3 depths × 4 months), we demonstrate that in ~86 % of the scenarios the particles are stranded in the Caribbean and in ~71 % they end up in the Amazon coast. Our results showed litter floating trajectories at 0-10 m water depth, transported every year to the Caribbean province. However, in August this transport is frequently blocked by the retroflection of the North Brazil Current adjacent to the Amazon River estuarine plume. Our results indicate routes for fast and long-distance transport of litter-rafting invasive species. We hypothesized a high risk of bioinvasion on important marine ecosystems (e.g., coral reefs) likely becoming increasingly threatened by these invasive species and debris. This highlights the imperative need for an ocean governance shift in prevention, control, and eradication, not only focused on local actions to prevent the spread of invasive species but also a broad international action to decrease and mitigate marine debris pollution globally.

Do coral reefs act as sinks for microplastics?

Microplastic (MP) pollution has been detected in coral reefs, raising concerns regarding its global impact. Although they cover a small portion (<1%) of the total area of the world's oceans, coral reefs are geological and biological structures that trap MPs and disproportionately enhance their accumulation. In this review, we attempted to understand how coral reefs act as short- and long-term sinks for MPs. We describe five characteristics that lead to the enrichment of microplastics in coral reefs: 1) adhesion on reef-building corals at distinct depths; 2) ingestion by reef organisms (e.g., suspension feeders, such as sponges, ascidians, and corals), bioconcentration, and formation of short-term (i.e., years to decades) biological sinks for MPs; 3) formation of long-term (i.e., centuries) MP sinks in coral skeletons and unconsolidated subsurface sediments; 4) reduction of sediment resuspension and seafloor turbulent kinetic energy by complex marine forest architecture that reduces bottom shear stress, facilitates the retention, and deposition of small (<0.5 mm) and high-density floating MPs; and 5) diagenesis of Anthropocene sedimentary rocks containing MPs. We estimate that reef processes may remove more than 10% of floating MPs in shallow tropical waters yearly. Statistical results show that microplastic abundance for reef-building corals are higher than values found in reef sediments and especially in seawater. Moreover, pellets, films, foams and mainly fragments and fibers have been found. These field-based data support our hypothesis of sinks in the reef sediments and organisms. We highlight the role of these seascapes in the interception of MPs as traps and sinks in reef sediments, biota, and carbonate frameworks. As coral reefs are prone to MP accumulation and can become pollution hotspots, global initiatives are necessary to conserve these rich ecosystems and prevent rapidly increasing plastic pollution.

Microplastics and microfibers in the Guajará Bay, Amazon delta: Potential sources and variability

The role of Amazon on the transport and as a source of microplastics (MPs) to the ocean is uncertain. This study is an assessment on the distribution of MPs and microfibers (MFs) in a portion of the Amazon delta. Guajará bay is a potential source for surrounding waters, since a metropolis is located at the right margin. Surface water samples were collected during the dry and rainy season of 2014/2015 at six stations. MP and MF abundance ranged from 218 to 5529.98 (1565.01 ± 196.94) particles·m-3. Transparent, white and blue particles were frequent. Higher values were detected on the right, urbanized margin of the bay (p = 0.0124). Most of the particles were anthropogenic cellulose fibers (68.8 %). Polyethylene terephthalate (52.9 %) and polyamide (34.4 %) were the dominant polymers. Our results indicate higher MP and MF abundances near to the potential source, the urban nucleus, and related to local hydrodynamic characteristics.

First assessment of microplastic and artificial microfiber contamination in surface waters of the Amazon Continental Shelf

The composition and distribution of microplastics (MPs) in the Brazilian Amazon Continental Shelf surface waters are described for the first time. The study was conducted during the 2018 rainy and dry seasons, using 57 water samples collected with aluminum buckets and filtered through a 64-μm mesh. The samples were vacuum-filtered in a still-air box, and the content of each filter was measured, counted, and classified. A total of 12,288 floating MPs were retrieved; particles were present at all 57 sampling points. The mean MP abundance was 3593 ± 2264 items·m^-3, with significantly higher values during the rainy season (1500 to 12,967; 4772 ± 2761 items·m^-3) than in the dry season (323 to 5733; 2672 ± 1167 items·m^-3). Polyamides (PA), polyurethane (PU), and acrylonitrile butadiene styrene (ABS) were the most common polymers identified through Fourier Transform Infrared Spectroscopy (FTIR) analysis. Cellulose-based textile fibers were also abundant (~40%). Our results indicate that the Amazon Continental Shelf is contaminated with moderate to high levels of MPs; the highest abundances were recorded at stations near land-based sources such as river mouths and large coastal cities.

Algae application in civil construction: A review with focus on the potential uses of the pelagic Sargassum spp. biomass

Pelagic Sargassum, usually found at the Sargasso Sea and the Western portion of the North Atlantic and Gulf of Mexico, has been detected in many new locations through the tropical Atlantic. The huge biomass found from the African coast to the Caribbean was called the Great Atlantic Sargassum Belt and is responsible for the stranding of tons of algae on coastal regions. Despite the environmental, social, and economic impacts, sargassum is a valuable source for multiple uses at the industry, such as alginates, cosmetics, recycled paper and bioplastics, fertilizers, and as raw material for civil construction. This work presents a systematic literature review on the use of algae at the civil construction sector, with a focus on the valorization of the pelagic Sargassum spp. biomass, by identifying the potential applications related to the use of other algal species. The review considered other genera of marine algae and marine angiosperms, resulting in a total of 31 selected articles. The marine grass Posidonia oceanica was the most used species, found in eight published papers, followed by the red alga Kappaphycus alvarezii with four studies. Two articles were available on the use of pelagic Sargassum spp. (S. fluitans and S.natans) for construction materials (adobe and pavement), with potential good results. The literature presented results from the use of marine algae and sea grasses for particleboards, polymeric and cemented composites, adobe, pavement, facades, and roofs. This article provides a state-of-the-art review of algal application in the civil construction sector and points out the main directions for the potentialities on the insertion of the Sargassum spp. biomass into the production chain of the sector.

Widespread microplastics distribution at an Amazon macrotidal sandy beach

Microplastics (MPs) are widespread and cause many impacts, yet their distribution and abundance are unknown for the Amazon coast. We estimated the abundance and distribution of microplastics at a sandy beach on the northern Brazilian coast during April 2014. Sand was collected and analyzed at three depth strata (0-20, 20-40 and 40-60 cm). MPs (250-500, 501-5000 μm) from each depth were sieved and retrieved by flotation when necessary. We found 492.5 ± 556.4 particles m^-3, with fibers comprising up to 95%. The abundance decreased with depth (61.5, 25 and 13.5% from the surface to 40-60 cm) and the deposition zone showed higher densities compared to the erosion zone. Although present in low to moderate abundance, MPs were widespread on the beach. The Amazon coast is an important area for fisheries and traditional communities, and further studies of its potential as a source or sink of MPs are needed.