A phytoremediation experiment was carried out in mesocosms to investigate the performance of Rhizophora mangle in the remediation of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediment contaminated with crude oil. The water pH of the experiments (phytoremediation and natural attenuation) ranged from 4.9 to 8.4 at 0 and 90 days, respectively. The oxy-reduction potential (Eh) ranged from oxidising (108.0 mV, time 0) to reducing (approximately −110.0 mV, time 90) environments. Dissolved oxygen (DO) ranged from 5.7 mg L⁻¹ (time 0) to 4.5 mg L⁻¹ and 3.6 mg L⁻¹ (time 90) in phytoremediation and natural attenuation, respectively. The sediments had silty texture and an average concentration of 5% organic matter (OM). Phytoremediation (60.76%) showed better efficiency in the remediation of the 16 PAHs compared to natural attenuation (49.57%). Principal component analyses showed a correlation between the concentrations of PAHs with pH, Eh, OM and DO in both experiments.

An experiment observed the behavior of selected tagged plastic items deliberately released in different habitats of a tropical mangrove forest in NE Brazil in late rainy (September) and late dry (March) seasons. Significant differences were not reported among seasons. However, marine debris retention varied among habitats, according to characteristics such as hydrodynamic (i.e., flow rates and volume transported) and relative vegetation (Rhizophora mangle) height and density. The highest grounds retained significantly more items when compared to the borders of the river and the tidal creek. Among the used tagged items, PET bottles were more observed and margarine tubs were less observed, being easily transported to adjacent habitats. Plastic bags were the items most retained near the releasing site. The balance between items retained and items lost was positive, demonstrating that mangrove forests tend to retain plastic marine debris for long periods (months-years).

Sargassum spp. strandings in the tropical Atlantic harm local ecosystems due to toxic sulfide levels. We conducted a mesocosm experiment to test the efficacy of iron(III) (hydr)oxides in (a) mitigating sulfide toxicity in mangroves resulting from Sargassum and (b) reducing potentially enhanced greenhouse gas emissions. Our results show that iron addition failed to prevent mangrove mortality caused by highly toxic sulfide concentrations, which reached up to 15,000 μmol l−1 in 14 days; timely removal may potentially prevent mangrove death. Sargassum-impacted mesocosms significantly increased methane, nitrous oxide, and carbon dioxide emissions, producing approximately 1 g CO2-equivalents m−2 h−1 during daylight hours, thereby shifting mangroves from sinks to sources of greenhouse gasses. However, iron addition decreased methane emissions by 62 % and nitrous oxide emissions by 57 %. This research reveals that Sargassum strandings have multiple adverse effects related to chemical and ecological dynamics in mangrove ecosystems, including greenhouse gas emissions.

The removal of ammonium (NH4+), nitrite (NO2−), nitrate (NO3−), and phosphate (PO4−3) in a closed silvofishery system was examined using three mangrove species (i.e., Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle). Specifically, six closed tanks were installed for this experiment with a population of 60 Dormitator latifrons fishes per tank. We planted 40 seedlings in each of three experimental tanks separated by species, while the remaining tanks were used as control. During 15weeks, nutrient concentrations among the three mangrove systems presented no significant differences (P>0.05). However, nutrient removal variability was minimum during the last 2–5weeks. Mangroves presented an average efficiency of 63% for the removal of NH4+ and NO2−. Contrary, the average removal potential of NO3− and PO4−3 was 50%. Results from this study suggest that the three mangrove species could be used in a closed silvofishery systems for the biological removal of NH4+, NO2−, NO3−, and PO4−3.

In Mexico, the mangrove is distributed in 764,486 ha, comprising the Atlantic coast from the Laguna Madre in Tamaulipas to Chetumal Bay in the Caribbean and in the Pacific from Ensenada, Baja California to Chiapas. On the coast of Oaxaca, coexist four species: red mangrove (Rhizophora mangle), white mangrove (Laguncularia racemosa) button mangrove (Conocarpus erectus) and black mangrove (Aviccenia germinans). In the Laguna “Salina” Tonameca, grows and develops the white, button, and black mangroves, whose spatial distribution decreases by deforestation, land use change, and increased saline substrate. Salinity of soil and waters, its concentration, and tipogenesis associated with the growth of mangrove trees were determined. Three saline gradients were identified in rainy season (gradient I: 2.18 dS m⁻¹; gradient II: 9.95 dS m⁻¹ and gradient III: 36.14 dS m⁻¹); while in drought season four gradients were detected (gradient I: 1.15 dS m⁻¹; II: 17.83 dS m⁻¹; III: 39.06 dS m⁻¹ and IV: 57.75 dS m⁻¹). The interannual saline variation is due to climatics, hydrologycal, and geomorpholigical conditions of the substrate. The lake salinity is hydrochloric, predominantly NaCl salt, of intense osmotic effect, which largely explains the mangrove halophytism. Moisture diluting brackish water, such that low salt conditions promotes growth and development of mangrove, but at concentrations > 35 g L⁻¹ limits their growth. In drought, hypersaline (>70 g L⁻¹) prevents the establishment and repopulation of this species.