Tracking the Dynamic Ecological History of a Tropical Urban Estuary as it Responds to Human Pressures

Unexpected Nitrogen Sources in a Tropical Urban Estuary

“…In the case of the CMP east, this activity may be associated with fixation, but the δ 15 N values indicate that the opposite may be true in San José Lagoon. The high values for δ 15 N, DEA, and microbial biomass data are consistent with the observations of others that nitrate removal processes dominate in this basin (e.g., Oczkowski et al, ; Pérez‐Villalona, ; Pérez‐Villalona et al, ).…”

“…The δ 15 N values in the surface sediments from this study and recent sediment core deposits (Oczkowski et al, 2019) from the CMP are consistent with the observations of others and suggest that N-fixation may be an important process in the CMP sediments and water column. The enriched nature of the CMP water, as evidenced by high fecal coliform concentrations, suggests that N and C loads from sewage are high.…”

“…In contrast, the highest δ 15 N values were measured in the adjacent San José Lagoon. A recent study of isotope values in sediment cores collected from the SJBE suggested that since the 1980s San José has been increasingly functioning as a settling basin and the higher δ 15 N values reflected a mix of urban runoff and nutrient cycling (Oczkowski et al, ). The CMP likely receives as much, if not more, urban runoff as San José Lagoon, but the δ 15 N values in those sediment cores declined over time.…”

Sequencing of Coastal Lagoon Samples from the Piñones Lagoon, Puerto Rico, Reveals Important Role of Bacterial Sulfur Metabolism in the Lagoon Ecosystem

“…It has recently been shown that Sulfurimonas species play an important role in other mangrove environments for the oxidation of the toxic sulfide produced by sulfur-reducing bacteria such as Sulfurospirillum species. These species likely play a similar role here for detoxification and maintenance of homeostasis in the lagoon ecosystem, although overgrowth of N-fixing, sulfur-reducing bacteria may contribute to buildup of nitrogen in these estuaries ( 2 , 5 ).…”

“…The lagoon has been impacted since 2016 by sedimentation problems related to the mangrove growing in the canals that joined the Piñones Lagoon to the Torrecillas Lagoon ( 1 ). Mangrove ecosystems have been proposed for wastewater treatment ( 3 , 4 ), although recent reports on the San Juan Estuary indicate that excessive nitrogen buildup has larger ecological consequences ( 2 , 5 ). Understanding the bacterial composition provides insight into the environmental impact that the bacterial microbiome has on the local ecosystem.…”