Food chains detrital

Laycock, R.A., 1974. The detrital food chain based on seaweeds. I. Bacteria associated with the surface of Laminaria fronds. Mar. Biol., 24 223-231. 

The free-standing water in peatlands does not transmit light well enough to support phytoplankton growth due to the presence of dissolved humic substances. Therefore in the aquatic phase of peatlands, light limitation and the acidity of the water favor detrital food chains based on bacteria to the near exclusion of autotrophic food chains based on phytoplanktons (Speigt and Blackith, 1983). Phytoplankton-based food chains are characteristic of many aquatic environments, such as lakes and oceans. 

There is one further major contributor to sedimentary organic matter, bacteria. A large proportion of the energy flow in ecosystems can pass through the detrital food chain, in which heterotrophic bacteria are prominent participants. Heterotrophic bacteria are important in all sedimentary environments, and although they consume organic detritus they supplement the organic matter with their own remains. In some environments autotrophic bacteria may also be important (e.g. the Black Sea see Section 3.4.3c). 

The rapid alteration of chlorophyll-a as phytoplankton leave the euphotic zone may well be expected to continue as passage through additional links in the food chain occurs. Thus, the detrital forms of chlorophyll-a, available to sedimentary diagenesis should contain a dominance of pheophorbide-a. 

The accumulation of xenobiotics into planktonic algae or plants (Section 3.1.3) may introduce the compound into higher organisms in the food chain such as fish, while the detrital material may eventually enter the sediment phase and be dispersed by any of the mechanisms noted in Section 3.5.1. 

Tenore, K.R., 1977. Food chain pathways in detrital feeding benthic communities a review, with new observations on sediment resuspension and detrital recycling. In B.C. Coull (Editor), Ecology of Marine Benthos. Belle W. Baruch Library Mar. Science No. 6. University of South Carolina Press, Columbia, S.C., pp. 37—54. 

Important elements of such turnover are trophic chains or food chains. These are series of biogenic elements and energy transfer with food from one group of organisms to another. Eugene Odum (1913-2002) proposed to distinguish two major types of trophic chains positioned at different levels pasturable trophic chains and detrital trophic chains. 

Detrital trophic chain is associated with the consumption and decomposition of dead organic matter, i.e., detritus. On the surface and in the soil layer this matter is represented by the remains of higher plants and serves as food for small animals often called meiofauna (bacteria, fungi, numerous insects, their larvae, ground worms, etc.). They are in turn con-siuned by soil mammals (moles, shrews, mice, gophers, etc.). The latter return substantial part of their organic matter back to the pasturable trophic chain. 

Estuaries, locations where freshwater from rivers mixes with seawater from the ocean, are another kind of biome in the hydrosphere (see Figure 12.5). Estuaries exhibit gradations of salinity, which vary with the ebb and flow of tides. The food chain in estuaries is based on both detrital food sources and phytoplankton. They are especially important as nurseries for marine fish and shellfish, in part because potential predators from the ocean are intolerant of the lower salinity of estuarine waters. 

The phytoplankton are the basis of all marine food chains. Then-primary productivity is constrained mainly by nutrient availability and is thus not uniform throughout the oceans. Moreover, the importance of the grazing pathway of energy transfer varies spatially along with detrital energy transfer (see Section 3.7) estimates of the latter vary from c. less than 10 percent to c. 90 percent. 

---