Decomposition patterns and nitrogen dynamics of black mangrove (Avicennia germinans)leaf litter in disturbed estuaries linked to the Lower Laguna Madre, Texas

Authors

Mario Alberto Marquez, University of Texas at Brownsville

Date of Award

11-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Alejandro Fierro-Cabo

Second Advisor

Dr. Carlos Cintra-Buenrostro

Third Advisor

Dr. Heather D. Alexander

Abstract

Estuaries are among the most productive aquatic systems in the world but are subject to both anthropogenic and natural disturbances. With increasing environmental concerns, efforts have become commonplace in assessing the status and trends of environmental conditions. In this study, an assessment of ecosystem status of various estuaries affected by different disturbances, was attempted through the examination of key functional processes such as leaf litter decomposition and nutrient dynamics during decay. Three estuaries located along the Brownsville Ship Channel near the southern terminus of the Lower Laguna Madre in Texas were studied. The overlying goal of this study was to compare the functional state of these estuaries, utilizing leaf litter decomposition rates and nitrogen dynamics. Black mangrove (Avicennia germinans) leaves were used as the decomposition substrate since it is endogenous to the Lower Laguna Madre system. Several aims were addressed in this investigation: 1) determine decomposition patterns (decay rates, half-­‐lives, recalcitrant pool sizes); 2) compare N content changes in decomposing mangrove leaves; 3) evaluate N immobilization/release during decay processes; and 4) appraise the value of decomposition process and N dynamics measurements as functional indicators in estuaries linked to LLM. Metrics derived from the decomposition process and concurrent N dynamics of leaf litter did discriminate among sites with different known disturbance histories. The ranking of the studied sites based in decomposition patterns did not fully correspond to the ranking obtained through the variables of N dynamics. v While these processes are linked by the activity of the decomposer community, they should be looked at separately to further classify the stability and ecological status of this type of estuarine systems in terms of ecosystem function.

Comments

Copyright 2013 Mario Alberto Marquez. All Rights Reserved.

Granting Institution

University of Texas Brownsville