Kelp forest food webs as hot spots for the accumulation of microplastic and polybrominated diphenyl ether pollutants.

Kelp forests (KFs) are one of the most significant marine ecosystems in the planet. They serve as a refuge for a wide variety of marine species of ecological and economic importance. Additionally, they aid with carbon sequestration, safeguard the coastline, and maintain water quality. Microplastic (MP) and polybrominated diphenyl ethers (PBDEs) concentrations were analyzed across trophic levels in KFs around Todos Santos Bay. Spatial variation patterns were compared at three sites in 2021 and temporal change at Todos Santos Island (TSI) in 2021 and 2022. We analyzed these MPs and PBDEs in water, primary producers (Macrocystis pyrifera), grazers (Strongylocentrotus purpuratus), predators (Semicossyphus pulcher), and kelp detritus. MPs were identified in all samples (11 synthetic and 1 semisynthetic polymer) and confirmed using Fourier-transform infrared microspectroscopy-attenuated total reflectance (µ-FTIR-ATR). The most abundant type of MP is polyester fibers. Statistically significant variations in MP concentration were found only in kelps, with the greatest average concentrations in medium-depth kelps from TSI in 2022 (0.73 ± 0.58 MP g-1 ww) and in the kelp detritus from TSI in 2021 (0.96 ± 0.64 MP g-1 ww). Similarly, PBDEs were found in all samples, with the largest concentration found in sea urchins from Punta San Miguel (0.93 ± 0.24 ng g-1 ww). The similarity of the polymers can indicate a trophic transfer of MPs. This study shows the extensive presence of MP and PBDE subtropical trophic web of a KF, but correlating these compounds in environmental samples is highly complex, influenced by numerous factors that could affect their presence and behavior. However, this suggests that there is a potential risk to the systems and the services that KFs offer.

Microplastics: Sources and distribution in surface waters and sediments of Todos Santos Bay, Mexico.

Microplastics (MPs) are ubiquitous and a threat to marine and freshwater environments. Effluent waters from secondary wastewater treatment plants (WWTPs) into Todos Santos Bay (TSB) were investigated as sources of MPs. MPs were detected in all analyzed matrices and presented variable morphologies. MPs from surface water samples (n = 18) varied from 0.01 to 0.70 plastic particles/m3 (pp/m3). Fragments (47 ±â€¯23%) and fibers (47 ±â€¯23%) were the most abundant particles found in the surface water samples. In sediment samples (n = 11), MPs varied from 85 to 2494 pp/0.1 m2. Sediment samples showed fragments of 70 ±â€¯19%, fibers 28 ±â€¯18% in mean. The range of MP values from WWTP effluents (n = 24) was 81 to 1556 pp/m3, and fibers (65 ±â€¯28%) were the most abundant MP particles. Several synthetic polymers (polypropylene, polyethylene, polyethylene-propylene, polyvinyl chloride, cellophane), and natural fibers (cotton and wood) were identified. The surface currents and the parameters that modulate them, are the main factors that dominate the distribution of MPs in surface waters. While in the sediments the parameters such as bathymetry and grain size distribution have more influence on their distribution in the marine environment, where the effluent waters from WWTPs only contributes MPs to the TSB.

Organochlorine pesticides in residential soils and sediments within two main agricultural areas of northwest Mexico: Concentrations, enantiomer compositions and potential sources.

The agricultural Mexicali and Yaqui valleys (MV, YV) in northwest Mexico were heavily treated with organochlorine pesticides in the past. Residential soils and agricultural drain sediments were sampled in 2008-2009 and analyzed for DDTs (o,p'- and p,p'- isomers of DDE, DDD and DDT); hexachlorocyclohexanes (α-, ß-, γ- and δ-HCH) and chlordanes (trans-chlordane, cis-chlordane, heptachlor and heptachlor exo-epoxide). Geometric means (GMs) (ng g-1 dry weight) were: MV soils (n = 27) ΣDDT 22, ΣHCH 0.80, ΣCHL 0.88; YV soils (n = 25) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.67; MV sediments (n = 3) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.53; YV sediments (n = 8) ΣDDT 2.6, ΣHCH 0.12, ΣCHL 0.090. GMs were significantly higher (p < 0.05) in MV than YV soils for ΣDDT and ΣHCH, but not for ΣCHL. Comparison to worldwide regulatory guideline values (RGVs) for residential soils showed all compounds below mean or GM RGVs, but above the lowest RGV in some cases. Low p,p'-DDT/(p,p'-DDT + p,p'-DDE) in most soils indicated aged residues. Lack of p,p'-DDT metabolism might account for its dominance in a few soils. HCH isomer profiles suggested aged technical HCH in the YV, and technical HCH + lindane in the MV. Heptachlor dominated the ΣCHL, probably from application of technical heptachlor as well as chlordane. Chiral compounds were nonracemic in soils and sediments and indicated enantioselective microbial degradation of (+)α-HCH, (-)trans-chlordane, (-)cis-chlordane and (+)o,p'-DDT. Depletion of (+)o,p'-DDT in soils may account for similar enantiomer signatures previously reported in air of northwest Mexico.