Coastal vegetated habitats can be important sinks of organic carbon (C) and mitigate global warming by sequestering significant quantities of atmospheric CO and storing sedimentary C for long periods, although their C burial and storage capacity may be affected by on-going sea level rise and human intervention. Geochemical data from published Pb-dated sediment cores, collected from low-energy microtidal coastal wetlands in El Salvador (Jiquilisco Bay) and in Mexico (Salada Lagoon; Estero de Urias Lagoon; Sian Ka'an Biosphere Reserve) were revisited to assess temporal changes (within the last 100years) of C concentrations, storage and burial rates in tropical salt marshes under the influence of sea level rise and contrasting anthropization degree. Grain size distribution was used to identify hydrodynamic changes, and δC to distinguish terrigenous sediments from those accumulated under the influence of marine transgression. Although the accretion rate ranges in all sediment records were comparable, C concentrations (0.2-30%), stocks (30-465Mgha, by extrapolation to 1m depth), and burial rates (3-378gmyear) varied widely within and among the study areas. However, in most sites sea level rise decreased C concentrations and stocks in sediments, but increased C burial rates. Lower C concentrations were attributed to the input of reworked marine particles, which contribute with a lower amount of C than terrigenous sediments; whereas higher C burial rates were driven by higher mass accumulation rates, influenced by increased flooding and human interventions in the surroundings. C accumulation and long-term preservation in tropical salt marshes can be as high as in mangrove or temperate salt marsh areas and, besides the reduction of C stocks by ongoing sea level rise, the disturbance of the long-term buried C inventories might cause high CO releases, for which they must be protected as a part of climate change mitigation efforts.
In late October and early November 2013 and 2017, hundreds of sea turtles were found dead along the Pacific coastline of El Salvador. The dead turtles were in good body condition and did not have any injuries or other major anomalies. In order to determine the role of paralytic shellfish toxins (PST) in this mass mortality, tissue samples, including blood, flipper, liver, kidney, stomach and intestinal contents, of dead green turtles (Chelonia mydas) and olive ridley turtles (Lepidochelys olivacea) were analyzed for PST using a radioactive receptor binding assay, enzyme-linked immunosorbent assay, and high performance liquid chromatography. Highest values of PST were detected in enteric contents in the 2013 event (7,304.1 µg STX eq kg −1) and in gastric contents during the 2017 event (16,165.0 µg STX eq kg −1). During these events, remotely-sensed chlorophyll-a and fluorescence line height imagery revealed anomalies suggestive of algal blooms off the coast of El Salvador. In the 2017 event, Pyrodinium bahamense was observed in samples of gastrointestinal contents from affected sea turtles. Seawater from the region where dead sea turtles were found was also analyzed, but saxitoxin-producing species were found in low abundance (5400 cell/L in 2013 and 672 cell/L in 2017), which may reflect limited sampling. Although threshold levels of toxicity in sea turtle species are not well-characterized, our evidence suggests that these large events were the result of PST-producing algal blooms and that these blooms are a major cause of sea turtle mortality in this region.
© 2022 Los Autores. Editado por la AEET. [Ecosistemas no se hace responsable del uso indebido de material sujeto a derecho de autor] Académicos de Centroamérica crean una red de investigación y monitorean la basura marina aplicando la ciencia ciudadana aeet ASOCIACIÓN ESPAÑOLA DE ECOLOGÍA TERRESTRE
The geochemical, mineralogical, and micropaleontological (Foraminifera, Ostracoda, Bacillariophyta) spatial and temporal variations in marshland sediments from the Jiquilisco Bay Biosphere Reserve, El Salvador, are described. The sedimentary characteristics of two marsh sites reveal contrasting sedimentary environments: site Los Cedrones depicts a high energy environment with sandy sediments, low organic matter content, and no microfossils, while site El Gimidor represents a lower energy environment with muddy sediments rich in organic matter and more abundant and diverse microfossils. 210 Pb-dated sedimentary cores showed changes over time (last 100 years) in the mineral and elemental composition, as well as in the accumulation rates, suggesting changes in the type and magnitude of sediments delivered to the sites. Sediment accumulation rates were similar at both sites, ranging from 1.2 ± 0.9 to 3.4 ± 0.5 mm yr-1 at Los Cedrones and from 0.8 ± 0.2 to 4.0 ± 0.5 mm yr-1 at El Gimidor. Even though both marshes are located 13 km apart, and depict different sedimentary environments, elemental composition, and microfossil assemblages, both sedimentary records show the influence of hydrological changes, probably due to the damming of the Lempa River and the sea-level increase during the last 100 years.
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