Burrowing invertebrates

The penetration of the O2 into the soil depends on its rate of consumption in aerobic processes and its rate of transport by mass flow and diffusion, and in the floodwater-soil interface, mixing by burrowing invertebrates. Various aerobic processes take place in these oxygenated zones. 

In practice redox conditions in the burrows will oscillate as the oxygenation of the floodwater varies over the diurnal cycle. Aller (1994) found in a wide range of organic matter-rich sediments containing burrowing invertebrates that... 

The upper few centimetres of the soil are subject to mixmg by invertebrates burrowing through the soil and ingesting soil particles. If populations are sufficiently... 

Echinoderms have yielded a smaller range of secondary metabolites than other marine invertebrates such as sponges or ascidians, perhaps due to their ability to deter predators by other means. The ophiuroids are able to burrow into the substratum and reduce exposure to predators. Many echinoderms are nocturnal, moving and feeding when predator activity is at a minimum. The outer layer of most echinoderms is either calcified or composed of insoluble proteins, making the organism unfavorable as prey.120... 

Animals are separated into thirty-five phyla, only the more common of which will be discussed here (see Table 5.1). All but the Chordata are invertebrates, animals that have no vertebral column (backbone) nor a notochord, the primitive beginnings of one. Invertebrates inhabit all types of water, they fly, they burrow, and they crawl on the ground. About 98% of all living animals... 

Small mammals (e.g., moles, mice, and voles) and certain bird species that live or nest in subsurface burrows may inhale volatile pollutants that are evaporated out of the soil as a vapor. This pathway is likely to be significant only in those cases where poor ventilation allows vapors to collect and concentrate and where the receptor spends a lot of time (e.g., when nesting) in such a poorly ventilated space. There is, however, little information available about how to quantify this exposure pathway. Small mammals are more likely to be significantly exposed to pollutants that have been taken up in their food items (e.g., plants, soil invertebrates) or through incidental ingestion of polluted soil particles. 

Salt or brackish marshes are important ecosystems because they are the habitat of many birds and fish that feed on a wide variety of invertebrates including crabs, snails, and worms. Some of these organisms burrow into the sediments providing a path for oil to penetrate if a spill occurs. These marshes are also the nurseries for many land and sea birds and animals. Salt marshes are especially vulnerable to oil spills because they are flooded at high tide and their complex surface traps large quantities of oil. It is also difficult to get into a marsh to assess the damage and clean up the oil. 

FIGURE 6.23 Schematic representation of burrowing by benthic invertebrates in sediments. Aerobic soil layer around irrigated burrow environment. 

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