2007 Wetland Inventory for the Eyre Peninsula

surveyed had very little aquatic vegetation abundance or diversity. The majority of vegetation was in theform of terrestrial-aquatic species such as samphires.20.0 AQUATIC INVERTEBRATE ANALYSIS20.1 BackgroundMacro and micro invertebrates are an essential component of the wetland food web. They are responsiblefor a significant proportion of the secondary production occurring in wetlands, and form two interconnectedwetland food chains, a grazing food chain and a detrital food chain, Davis and Rolls (1987). Invertebratescomprise much of the diet of waterfowl populations the diversity and abundance of waterfowl can be adirect consequence of the invertebrate food supply.20.1.1 Ecological benefitsYen and Butcher (1997) provide some examples of direct ecological benefits that invertebrates contribute.Tangible direct benefits:1. Plant pollination2. Effects on soil; soil formation and fertility.3. Decomposition; fragmentation and recycling of dead plant and animal material.4. Position in the food web; invertebrates are the principle food for many vertebrates. They form a basicelement in food chains and networks which underlie the general balance of nature5. Preditation and parasitism; involved in the natural regulation of populations of other species throughpredation and parasitism; and thus form the basis of biological control.Indirect ecological benefits:• Ecosystem stability: the loss of species from highly interrelated systems is likely to cause a cascade offurther losses.• Evolutionary time: diversity within ecosystems maintains greater diversity.20.1.2 Trophic dynamicsStanding water communities are dynamic systems which reflect change in many variables. The trophicstate of a wetland depends on nutrient inputs from the catchment and within the wetland (Boulton andBrock 1999). If samples from all trophic groups are collected, this could suggest that the aquatic ecosystemis a reasonable state of equilibrium. The top of the food chain is occupied by vertebrate predators, includingfish, water rats and water birds. Terrestrial predators can be considered to be on the top of the aquatic foodchain, and provide a pathway for export of nutrients and other material from the wetland ecosystem(Boulton and Brock 1999).Primary producersPrimary producers form two groups those that are suspended or floating and those attached to substrate orother plants. Attached macrophytes includes frindging reeds and submerged plants and periphyton (thebiota attached to submerged surfaces). Suspended or floating forms generally consist of the phytoplanktonand algae groups. Phytoplankton form the basic photosynthetic basis for the open water food web in moststanding watersConsumersThere are two main types of consumers based on diet: grazers that consume plants and predators thatconsume other animals.26