GS23A-01
Geochemical characterization of anthropogenic effects in coastal lagoons at the Northern Pacific coast of Mexico
Sinaloa is a coastal state located in the Gulf of California that is characterized by an economy mostly based on agroindustry, fisheries, aquaculture and tourism. It has been recognized that the coastal lagoons neighboring the most developed economic areas of Sinaloa state are showing signs of infilling and eutrophication that have been related with the dumping of untreated effluents from agriculture croplands, aquaculture facilities and human settlements. The environmental impact to the lagoons of Navachiste, Santa María, Ohuira, Ensenada del Pabellón, Chiricahueto, Ceuta y Estero de Urías has been evaluated through the assessment of time dependent changes in the 210Pb-derived sedimentation rates and the sediment concentrations of geochemical constituents such as organic matter, carbonates and nutrients (N and P). 210Pb geochronology has shown that accretion rates and nutrient fluxes in some lagoons have considerably increased due to the development of the agriculture activities in the region. For instance, in Ohuira lagoon, at the area adjacent to the culture fields of El Fuerte Valley, sediment accumulation has increased ~5 times with respect to the pre-anthropogenic conditions in less than 20 years (0.06 to 0.32 cm yr-1), while C, N and P fluxes (mg cm-2 yr-1) increased almost 10, 10 and 13 fold, respectively (4.0-37 for OC, 0.6-6.0 for N and 0.1-7.0 for P).
GS23A-02
Spatial and temporal variation of water quality in the coastal lagoons of Sinaloa
The Mexican state of Sinaloa has 656 km of coastline and 221,600 ha of coastal lagoons, and is characterized by a high fishing and agriculture activity. It is well known that agricultural activities constitute a major factor affecting the water quality in the coastal waters. The current study focused on the 6 more important coastal lagoons of Sinaloa (Topolobampo-Ohuira-Santa María, Navachiste-San Ignacio-Macapule, Santa María-La Reforma, Altata-Ensenada del Pabellón, Ceuta and Teacapán-Agua Brava) with the aim to evaluate the water quality spatial and temporal variation at the lagoons (physico-chemical parameters, nutrients (N, P and Si), dissolved oxygen, total suspended solids and chlorophyll a) and to assess its eutrophication status. The water samples were collected in several stations at each lagoon (between 9 and 23 stations depending on the lagoon area) at low and high tides, during three different weather periods (dry-warm, rainy and dry-cold seasons) between May 2004 and April 2005. Mean concentrations of nutrients (μM), dissolved oxygen (mg/L) and chlorophyll a (mg/m3) obtained for each variable were comparable between lagoons (total N=51±45; total P= 2.5±1.5; Si=23±31; DO=6.7±1.8; Chll=1.7±1.9) although seasonal and spatial differences were observed at each lagoon. The nutrient concentrations measured fell in the typical concentration intervals for coastal lagoons; however, critical sampling points were identified and related to direct discharges of untreated effluents from municipal wastes, aquaculture farms and agriculture drain ditches.
GS23A-03
Potentially Toxic Element Uptake by Bacillus jeotgali Strain U3: A Natural Attenuation Mechanism in polluted sediments from Estero de Urías Coastal Lagoon (SE Gulf of California)?
In addition to an increased flux of potentially toxic elements (PTE's) into aquatic ecosystems, toxicity, bioavailability and persistency of these pollutants have led to critical localized pollution sites around the world, and the risk for the environment and the health of organism, including humans, has been increased. Clean-up technologies for the treatment of huge volumes of water, sediments and soils contaminated with these elements are needed. Use of bacteria as concentrators of PTE's can become a good tool for the remediation of man- impacted coastal ecosystems. A subtropical estuarine bacterium was isolate from surface sediments from Estero de Urías coastal lagoon, Mazatlán, Mexico, which is an aquatic ecosystem surrounded by several anthropogenic that release PTE's into the environment. This bacterial strain (U3) was ascertained (16s rRNA analysis) to belong to the Bacillus jeotgali specie. Batch experiments with different bacterial biomass and PTE (Cd, Cu, Hg, Pb and Zn) concentrations, pH and temperature were carried out in order to evaluate the biosorption capacity of Bacillus jeotgali strain U3. Except data from Zn experiments, all values were fitted to the adsorption Langmuir model. The maximum adsorption capacities (qmax) were 58 mg Cd g-1, 27 mg Cu g-1, 191 mg Hg g-1 (viable biomass), 21 mg Hg g-1 (non-viable biomass), 90 mg Pb g-1. Adsorption of Zn was 350 mg g-1, when equilibrium concentration in solution was 130 mg Zn l-1. According our data, Bacillus jeotgali strain U3 is considered as a suitable adsorbent and the presence of this microorganism in Estero de Urías coastal lagoon can produce a natural attenuation of potentially toxic elements pollution.
GS23A-04
Anthropogenic nitrogen in a subtropical coastal lagoon (SE Gulf of California): sources and ecological consequences using isotopes stables
Chemical and isotopic compositions of N were studied in anthropogenic effluents received by Altata-Ensenada- Pabellón lagoon (AEP), a typical coastal ecosystem along the SE GC. Human activities mobilize from 33,000 to 55,000 tons of N per year to the AEP, which the agriculture (70%), livestock (10%), and atmospheric deposition (10%) are the largest N sources. Other N sources including sewage, shrimp farming, poultry, and livestock effluents constituted less than 10% of N inputs. The N is distributed as inorganic N that accounts for an input of 72% (NO3- 65% and NH4+ 7%) and organic N for 28% (>90% of the organic N occurring as DON). The N isotopic composition in the different effluents vary 6.1-16.1‰ for 15N-NH4+ and 2.1-15.9‰ for 15N-NO3. The 15N-NO3- values in agriculture effluents are related to fertilizer, while the enriched values of 15N-NH4+ in sewage and animal effluents and 15N-NO3- in groundwater result of the high ammonification and denitrification during the transport to the lagoon. Overall the C/N ratios (5.3-21.1) and isotopic signatures (13C -30.6 to -21.4‰ and 15N 6.1-12.5‰) in the POM for the diverse effluents had measurable differences and consistent with their origins. The 15N-DIN values measured at the selected stations recording inputs into AEP lagoon waters oscillated from 4.4 to 6.5‰ for 15N- NO3-, 12.9 to 20.9‰ 15N-NH4+, and from 4.4 to 10‰ 15N-POM. Overall the 15N values predicted by mass balances are in the range of the measured isotopic composition. The N requirement in Pacific Mexican lagoons is estimated to be 155 to 400 kg N ha-1 y-1, however, the current level is 1480 kg N ha-1 y-1, with anthropogenic N inputs (1200 kg N ha-1 y-1) of 80%. This excess of primary productivity is evidenced by the phytoplankton and macroalgae blooms that occur year-round, mainly in the areas close to the nutrient discharges from AEP lagoon.
GS23A-05
Geo-environment studies applied to dumpsite remediation in a coastal river-lagoon system in southern Tamaulipas, Mexico.
The "Isteta del Zapote" dumpsite, located in Tampico was used for this purpose approximately for 28 years (1978-2003). The Dumpsite is 42 ha, with thickness of waste of 3-9 meters. The site has approximately 2.5 millions tons of waste accumulated mostly from household waste. The dumpsite was recently (2004) closed and an inter-institutional remediation project with academic character was started in order to develop an Executive Project. The preliminary results of the geo-environment approach about geochemistry, geo-technical and geophysical correlations were focused in the vertical profile of sediments in the Zapote Dumpsite. The metal concentrations in the upper layer (0-2m) of this profile were 60-20 mg/Kg, while the metal concentrations in the lower layer (2-11m) were below 30 mg/Kg. These concentrations were correlated with the Plastic Index results among the ranges of 45 to 20%. A 75 to 38% of Liquid Limit corresponded to the upper layer. The Plastic Index and Liquid Limit were below to 30 and 50% in the lower layer, respectively. The resistivity results in the upper layer were 0.5-0.2 ohm-m, while an increase of values up to1.6 ohm-m in the lower layer was found. These results suggest the presence of a natural liner (seal layer) at least in the southwest front of the Zapote dumpsite.