Hawaii FEP - Western Pacific Fishery Council

and include fish, mollusks, crustaceans, mammals, and other carnivorous and omnivorousorganisms. Decomposers live off dead plants and animals, and are essential in food chains asthey break down organic matter and make it available for primary producers (Valiela 2003).The microbial loop is the trophic pathway in aquatic environments where dissolved organiccarbon (DOC) is reintroduced to the food web through the incorporation into bacteria. Bacteriaare consumed mostly by protists such as flagellates and ciliates. These protists, in turn, areconsumed by larger aquatic organisms (for example small crustaceans like copepods). The DOCis introduced into aquatic environments from several sources, such as the leakage of fixed carbonfrom algal cells or the excretion of waste products by aquatic animals and microbes. DOC is alsoproduced by the breakdown and dissolution of organic particles. In inland waters and coastalenvironments, DOC can originate from terrestrial plants and soils. For the most part, thisdissolved carbon is unavailable to aquatic organisms other than bacteria. Thus, the reclamationof this organic carbon into food web results in additional energy available to higher trophiclevels (e.g., fish). Because microbes are the base of the food web in most aquatic environments,the trophic efficiency of the microbial loop has a profound impact on important aquaticprocesses. Such processes include the productivity of fisheries and the amount of carbonexported to the ocean floor.Marine food webs are complex representations of overall patterns of feeding among organisms,but generally they are unable to reflect the true complexity of the relationships betweenorganisms, so they must be thought of as simplified representations. An example of a marinefood web applicable to the western Pacific is presented in Figure 9. The openness of marineecosystems, lack of specialists, long life spans, and large size changes and food preferencesacross the life histories of many marine species make marine food webs more complex than theirterrestrial and freshwater counterparts (Link 2002). Nevertheless, food webs are an importanttool in understanding ecological relationships among organisms.50