Aquatic Sciences Meeting, Albuquerque 2001

SS10 Human Activities and Their Effects on Aquatic Ecosystems (Environmental Connections; Science and Society Connections)

Date: Monday, February 12, 2001, Time: 11:15:00 AM

Location: La Cienega

Tribble, J, S, University of Hawaii, Honolulu, USA, jtribble@soest.hawaii.edu

Garrison, G, H, University of Hawaii, Honolulu, USA, garrison@soest.hawaii.edu

Glenn, C, R, Univesity of Hawaii, Honolulu, USA, glenn@soest.hawaii.edu

SEASONAL DEPOSITION IN A TROPICAL POND DURING THE HOLOCENE

Ordy Pond, a coastal, brackish water pond in Hawaii, has received continuous aquatic deposition since the early Holocene. Much of the 9780 yr, 13.5 m sedimentary record consists of alternating laminae of inorganically-precipitated carbonate and organic-rich, diatomaceous material thought to have been deposited in a seasonal cycle related to rainfall. Carbon and oxygen isotopic data are consistent with precipitation of calcite during relatively hot, dry summers and formation of nutrient-driven blooms of diatoms associated with winter rain events. The arrival of Polynesians in Hawaii roughly 950 yr BP coincided with a shift from dry forest to grassland in the Ordy Pond region, and a change from the laminated sequence to subtly banded, mixed carbonate/organic matter/diatomaceous sediment. An even more dramatic shift to faintly banded, sapropelic sediment corresponded to the arrival of European settlers in the islands and the advent of sugar cane and sisal cultivation. Carbon and oxygen stable isotopes vary inversely in the laminated sequence, but covary in the post-contact sediments. The current water column is highly eutrophic, poorly oxygenated to anoxic, and highly supersaturated with respect to calcite.

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Aquatic Sciences Meeting, Albuquerque 2001

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