The influence of El Niño–Southern Oscillation (ENSO) on productivity at upwelling systems has been extensively studied. However, in recent decades, ENSO diversity has been documented; there are more frequent events with anomalies in the central Pacific (CP) causing ecological impacts that are different from the canonical events centered in the eastern Pacific (EP). We hypothesize that ENSO effects on upwelling intensity and its biological response are highly dependent on ENSO diversity. Wavelet coherence was computed for monthly standardized anomalies of Ekman transport and sea surface Chlorophyll-a (Chl-a) concentration from eight upwelling centers located along the west coast of the Baja California peninsula (1993–2022). Ekman transport (ET) showed a non-linear association with ENSO at interannual periodicities between 1.2 and 7 years, as well as semiannual scale variability. Coherence between ENSO and ET showed a reduction in upwelling intensity during CP ENSO events and an increased upwelling intensity after EP El Niño events with regional differences. Our results reveal an influence of northern Pacific circulation that subsequently influences ENSO events during its development and its peak. We detected an influence of SST and wind anomalies on the ENSO–Ekman transport connection associated with the northern Pacific Meridional Mode pattern. The CP shows an important role in sea surface Chl-a concentration anomalies (1998–2022). We highlight the conceptual relevance of distinguishing ENSO diversity, with influential ecological effects associated with CP ENSO events.

Contamination of marine ecosystems by pharmaceutically active compounds (PhACs) deserves more research since their environmental fate differs from that observed in freshwater systems. However, knowledge remains scarce, especially in semi-arid coastal regions of the Global South. This study investigates the occurrence and distribution of caffeine, carbamazepine, ciprofloxacin, and sulfamethoxazole in sediments from the La Paz lagoon, a coastal system in a semi-arid region of Mexico with inverse estuarine conditions. Samples of superficial sediments (0–5 cm depth) were collected from 18 sampling points distributed through the lagoon, encompassing sites heavily polluted by discharges of municipal sewage and 3 potentially pristine sites far from the urban and peri-urban zones. Also, a 25 cm length sediment core was taken and divided into 1 cm sub-samples to determine the deposition of target PhACs in the sediment bed through time. The extraction of the target PhACs was performed through the accelerated solvent extraction (ASE) technique and quantification was achieved using a validated HPLC-MS/MS analytical method. The concentration of caffeine, carbamazepine, ciprofloxacin, and sulfamethoxazole in superficial sediment oscillated in the range of 1 to 45 ng g⁻¹ (dry weight). The highest mass fraction of target PhACs was detected in sites impacted by wastewater discharges. The caffeine-to-carbamazepine ratio was determined for the first time in marine sediments impacted by wastewater discharges, resulting in values from 4.2 to 9.12. Analysis of the 25 cm length sediment core revealed a high dispersion of caffeine, which was attributed to high water solubility, while antibiotics were predominantly detected in the upper 20 cm of the core. Risk quotients were calculated, observing low risk for caffeine, carbamazepine, and ciprofloxacin, while sulfamethoxazole presented high risk in all the sampling points. PhACs are retained in superficial sediments from a lagoon impacted by wastewater discharges, and the level of impact depends on the properties of the compounds and the TOC content in sediments. Risk assessments should be performed in the future considering the combination of pharmaceuticals and byproducts in marine sediments. This research emphasizes the importance of sewage management in preserving marine ecosystems in semi-arid regions in the Global South.

Heavy metal pollution in aquatic ecosystems is a critical environmental issue worldwide. In these ecosystems, the seston adsorbs heavy metals from the water and introduces them into the food web, causing potential environmental and health risks. This study analyses how heavy metals (Cd, Hg, Cr, Cu, Pb, Fe, and Mn) are distributed in the water and seston of the Tampamachoco Lagoon, an ecosystem affected by pollution from a thermoelectric plant and by hydrometeorological variability, both of which influence their concentrations. The relationships among metal distribution, physicochemical variables, and the influence of plant emissions in three seasons (rainy, northerly windstorms, and dry) were analyzed. The metal concentrations in seston (Fe > Mn > Pb > Cu > Cr > Hg) were up to four times higher than in the water column (Fe > Mn > Cr > Cd > Pb > Cu > Hg), emphasizing the key role of particulate matter in metal transport and bioavailability. Particularly, the Cd concentrations exceeded WHO thresholds by 527.6% in the water column during the rainy season, while Hg and Pb exceeded the thresholds of the Mexican criteria for the protection of marine aquatic life by 4.05% and 41.6%, respectively. Principal Component Analyses revealed distinct spatiotemporal distribution patterns for metals in water and seston, reflecting the combined effects of natural variability and anthropogenic inputs. The strong association between metals and seston indicates continued contamination and potential risks to aquatic ecosystems. These findings highlight the environmental impact of metals on seston and the need for monitoring to assess aquatic ecosystems’ health. Our results highlight the importance of understanding how metals are distributed between seston and water, and how climate variability affects pollutant redistribution patterns. We propose that water quality regulations need to be rethought and redirected towards the achievement of new strategic objectives that truly integrate the different pollutant sources whose final destination is water bodies, so as to protect and conserve biodiversity and aquatic ecosystems.