3 - The Interstitial Environment

Abstract

This chapter provides a brief overview of the interstitial system of coastal environments. The interstitial system has its physical structure and dimensions defined by the granulometry of the sand, but its dynamics controlled by the process of water filtration through the beach face. Water filtration is driven by waves and tides. Reflective beaches typically consist of coarser sand with high permeability. They filter large volumes of water at fast rates, and are consequently well flushed and oxygenated. Dissipative beaches, by contrast, consist of finer sands with lower permeabilities, and filter smaller volumes of water at low rates. Waves are thus more important in reflective systems and tides in dissipative cases. Interstitial chemistry is primarily determined by a response to the balance between inputs of oxygen and organic materials, with the former more vigorous in reflective situations. Surplus organic input will lead to the development of anaerobic conditions. This is more likely to develop in dissipative situations, whereas reflective beaches are more likely to be physically dynamic with strong interstitial flows and desiccation during low tide. This chapter concludes with the discussion of optimum conditions required for the development of an abundant interstitial fauna.