ABSTRACT
CONTENTS Introduction ................................................................................................................................................ 5 Characteristics of Bioindicators................................................................................................................. 6 Application of Bioindicators in Estuarine Ecosystems............................................................................. 8
Direct vs. Indirect Effects ................................................................................................................ 8 Temporal Response Scaling ............................................................................................................. 9 Establishment of Causality............................................................................................................. 11 Environmental Profiling and Diagnosis ......................................................................................... 12 Integrated Effects Assessment........................................................................................................ 14
Conclusions and Synthesis ...................................................................................................................... 16 References ................................................................................................................................................ 16
Estuaries are complex ecosystems that are controlled and regulated by a variety of physicochemical and biological processes. In addition, estuarine organisms experience a variety of natural and anthropogenic stressors, both of which vary spatially and temporally. High variability of environmental factors combined with synergistic and cumulative interactions of these factors complicates the interpretation and evaluation of the effects of stressors on estuarine biota. Because of their complexity, estuaries present unique challenges relative to understanding the effects of stressors and the underlying causes of these effects on biological components of estuarine ecosystems. Understanding the relationships between environmental stressors, causal mechanisms of stress, and biological effects is critical for achieving effective management and regulation of estuarine resources. As reflected in the chapters in this book, many studies focus on the structural aspects of estuarine systems, such as identification and description of organisms, populations, and communities. Several chapters describe the occurrence, distribution, and abundance of estuarine biota relative to spatial and temporal patterns of various influential or controlling physicochemical and biological factors, such as salinity, nutrients, habitat availability, and food availability. Few studies, however, have focused on understanding the mechanisms or the functional processes responsible for observed changes in biological components of estuaries.
