Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

First Advisor

John W. Day, Jr

Abstract

Laguna de Terminos is Mexico's largest coastal lagoon. There is a high habitat diversity including open water, mangroves, seagrasses and marshes, which supports Mexico's most economically important fisheries. Understanding ecosystem processes is essential for effective management of the lagoon's resources. This research developed landscape-level models for aquatic primary production (LAPPTER model), and fish migration (ROE model) in Laguna de Terminos. The ROE model was developed first as a theoretical approach, and later integrated into the LAPPTER model as a submodule which utilizes simulated production as a food source. The ROE model includes behavioral rules for fish movement based on environmental tolerances and population parameters such as mortality and birth rates. LAPPTER describes landscape processes controlling aquatic primary production, and accounts spatially and temporally for fluxes and interactions among biotic and abiotic components in the water column. The output demonstrated patterns of production associated with rivers, rainfall and cloud cover. Modeled phytoplankton peaked during the maximum river discharge period (wet season). Seagrass production peaked when salinity and light were at a maximum (dry season). These patterns imply that phytoplankton are nutrient limited and benthic macrophytes are light limited. Spatial distribution of phytoplankton expanded with maximum river discharge, supporting the idea of nutrient limitation. The LAPPTER and ROE model combination examined spatial and biological population dynamics, giving a better analysis of fish behavior and habitat utilization. Spatial results for seasonal visitors into the lagoon indicated where ecological parameters combined "optimally". Modeled stenohaline visitors relied on presence of marine waters inside the lagoon, never utilizing resources available near the deltas. Euryhaline visitors used the lagoon more fully, concentrating in the deltas. All migrations agreed with life history observations of prior studies. Finally, an interactive and user-friendly computer interface was developed to expedite organization and information transfer of research about Laguna de Terminos, providing assessment data for environmental policy makers and managers. This interface provides access to information on ecological functions and effects of human activities, including simulations of fish migrations and aquaculture scenarios. This system delivers capabilities and data from a desktop computer which were previously accessible only from mainframe computers.

Pages

171

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