Abstract
A 210 Pb-dated sediment core from a small bay in the southern basin of Lake Petén Itzá, Guatemala documents recent cultural eutrophication. Increased sediment accumulation beginning ∼1930 A.D. coincided with catchment population growth and was a consequence of watershed deforestation and increased surface run-off. At the same time, geochemical records from the Lake Petén Itzá sediment core indicate increased phosphorus loading and organic matter accumulation. High nutrient concentrations after 1965 A.D. coincided with lower sediment C/N ratios, suggesting an increase in the relative contribution of phytoplankton to the organic matter pool. This inference is confirmed by the dominance of eutrophic and hypereutrophic diatom species. Organic matter δ 13 C values decreased after 1965 A.D., seemingly contradicting other indicators of recent eutrophication in the southern basin of Lake Petén Itzá. Relatively depleted δ 13 C values in recent sediments, however, may reflect a contribution from 13 C-depleted sewage effluent. Increased δ 15 N of organic matter after 1965 A.D. indicates changes in the dissolved inorganic nitrogen delivered to the lake. The relatively small increase in δ 15 N (∼0.6‰ ) is less than might be expected with nitrate loading from sewage and soils, and might be offset by the presence of nitrogen-fixing cyanobacteria with low δ 15 N values.
Original language | American English |
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Journal | Default journal |
State | Published - Jan 1 2004 |
Keywords
- Carbon isotopes
- Lake sediment
- Eutrophication
- Guatemala
Disciplines
- Biology