CONTENTS 1. Introduction.................. 5 2. Methods................... 8 2.1. Sampling methods.............. 8 2.2. Sorting and preservation of the samples.......... 10 2.3. Measuring methods for the environmental factors....... 10 2.3.1. Introduction............... 10 2.3.2. The grain-size data............. 10 2.3.3. Amount of organic matter............ 12 2.3.4. The interstitial water............ 14 2.3.5. Exposure to waves............. 14 2.4. Mathematical methods.............. 15 3. The environment................. 17 3.1. Weather and climate............... 17 3.2. The morphology of the Delta area........... 19 3.3. Substrate and sediments.............. 20 3.3.1. Types of sediments and substrate.......... 20 3.3.2. Distribution of sediments..... ...... 22 3.3.3. Sorting of sediments............. 25 3.3.4. Important characteristics of sediments........ 25 3.3.4.1. Water circulation............ 25 3.3.4.2. Interstitial temperature.......... 29 3.3.4.3. Interstitial salinity........... 29 3.3.4.4. Oxygen in the interstitial environment...... 34 3.3.5. Organic matter.............. 35