The Ecology of a Salt Marsh

Ecologists have two long-standing ways to study large ecosystems such as lakes, forests, and salt-marsh estuaries. In the first, which G. E. Hutchinson has called the holological approach, the whole ecosystem is first studied as a "black box," and its components are investigated as needed. In the second, which Hutchinson has called the merological approach, the parts of the system are studied first, and an attempt is then made to build up the whole from them. For long-term studies, the holological approach has special advantages, since the general patterns and tentative hypotheses that are first worked out help direct attention to the components of the system which need to be studied in greater detail. In this approach, teams of investigators focus on major func­ tions and hypotheses and thereby coordinate their independent study efforts. Thus, although there have been waves, as it were, of investigators and graduate students working on different aspects of the Georgia salt-marsh estuaries (personnel at the Marine Institute on Sapelo Island changes every few years), the emphasis on the holo­ logical approach has resulted in a highly differentiated and well-coordinated long-term study. Very briefly, the history of the salt-marsh studies can be outlined as follows. First, the general patterns of food chains and other energy flows in the marshes and creeks were worked out, and the nature of imports and exports to and from the system and its subsystems were delimited.

Contenu

Ecosystem Structure and function.- 1. Ecology of Salt Marshes: An Introduction.- 1.1. Salt Marsh Ecology on Sapelo Island.- 1.2. Development of Salt Marshes.- 1.3. Ecological Processes in the Marsh.- 1.4. Carbon Mass Balance and Modeling.- 2. The Physical and Chemical Environment.- 2.1. Geomorphology.- 2.2. Physical Conditions.- 2.3. Water Chemistry.- 2.4. Hydrology and the Flux of Materials.- Salt Marsh Populations.- 3. Primary Production.- 3.1. The Community of Higher Plants.- 3.2. The Epibenthic Algal Community.- 3.3. Phytoplankton.- 3.4. Total Plant Production.- 4. Aquatic Macroconsumers.- 4.1. Foods and Feeding Categories.- 4.2. Impact of Macroconsumers on Salt Marsh Metabolism.- 4.3. Regulation of Salt Marsh Macroconsumers.- 5. Grazers on Spartina and Their Predators.- 5.1. Vertebrate Herbivory.- 5.2. Primary Production and Herbivory in Grasslands.- 5.3. Effects of Herbivory.- 5.4. Arthropod Primary Consumers.- 5.5. Vertebrate Predators.- 5.6. Arthropod Predators.- 5.7. Tidal Influences.- 5.8. Spatial and Seasonal Influences.- 6. Aerobic Microbes and Meiofauna.- 6.1. Microbial Standing Stocks.- 6.2. Aerobic Utilization of Organic Matter.- 6.3. Regulation of Microbial Communities.- 7. Anaerobic Respiration and Fermentation.- 7.1. Processes.- 7.2. Controls and Interactions.- The Salt Marsh Ecosystem.- 8. The Cycles of Nitrogen and Phosphorus.- 8.1. Phosphorus.- 8.2. Nitrogen.- 8.3. Net Flux of Phosphorus and Nitrogen.- 9. A Model View of the Marsh.- 9.1. What is a Model?.- 9.2. The Salt Marsh Model.- 9.3. First Generation Models.- 9.4. A Man-Environment Model.- 9.5. A Successional Model.- 9.6. Future Directions.- 10. The Salt-Marsh Ecosystem: A Synthesis.- 10.1. Diversity and Stability.- 10.2. Transport of Materials.- 10.3. Assimilation of Wastes.- 10.4. Aesthetics.- References.