Aquatic Organisms Introduction
(Information compiled by Emily Banks)
The stream systems of the Colorado Front Range support a variety of aquatic organisms. These stream systems are inhabited by a range of macroinvertebrates and vertebrates which both play an active role in shaping aquatic ecosystems. Conversely, aquatic organisms in any given stream system are influenced by local characteristics such as primary production, geomorphic setting, and the process domain characteristics of the stream segment. Human alterations of the environment can also substantially impact aquatic life.
Click a link below to find out more about aquatic organisms in the stream systems of the Front Range:
Macroinvertebrate - Introduction
One important class of aquatic organisms are macroinvertebrates. Macroinvertebrates can be broken into five functional groups based on their modes of feeding within an aquatic ecosystem (Wallace 1996). These five basic groups are grazers, shredders, gathers, filter feeders, and predators. It is important to note that the distinctions between classification are not absolute; in any given stream system there are many different organisms that can be classified into the groups listed above. Macroinvertebrates are important components of stream systems and can have profound impacts on nutrient cycles, primary productivity, decomposition, and translocation of materials. In addition, they can be important indicators of stream health.
References
Macroinvertebrates - Classification
The functional groups of macroinvertebrates outlined below are summarized from an article by Wallace (1996).
Grazers are organisms that feed on benthic primary producers. These benthic primary producers consist of different types of green algae, cyanobacteria, and diatoms. As might be expected, grazer populations are directly dependent on the amount of primary producers, therefore environmental conditions which increase primary production will in turn affect grazer populations. Natural occurrences or human actions which increase sunlight or nutrient inputs may increase the numbers of grazers within a stream system. Also, environmental conditions of the stream segment, such as the process domain, may impact this functional group.
Shredder macroinvertebrates break down coarse particulate matter (CPOM) and use this as their food source. The CPOM that shredders break down often consists of leaf litter inputs into the stream. Shredders are particularly active in upland streams that are heavily forested because these areas receive large amounts of litter input. Shredder organisms are vital in these upland stream environments because they break down CPOM into fine particulate organic matter (FPOM), which is transported downstream and used by a variety of other stream organisms. In addition to breaking down CPOM, shredders also play an active role in wood decomposition.
Gatherers are organisms which are adapted to feeding on FPOM deposited on the substrate of the stream system. Because of their reliance on FPOM, gatherers rely on shredder organisms that break down CPOM into FPOM. Gatherers thus rely on litter inputs into a stream system.
Filter feeders are macroinvertebrate organisms that feed on particles suspended in the stream system. Filter feeders can be predatory, thus feeding primarily on animals in suspension, or they can filter and feed on FPOM suspended in the water column. Like gatherers, this functional group relies on FPOM and thus on shredder populations upstream that convert CPOM to FPOM. As discussed in Wallace (1996), this functional group has the potential to greatly impact nutrient and organic matter levels in downstream channel segments.
Predators are the final functional group of macroinvertebrates. As in other ecosystems, predators feed on other macroinvertebrates within the stream system. Also, this functional group has the ability to greatly affect and regulate their prey via consumption and population influences (reproduction and growth). Predators can also impact stream dynamics; for example, if shredder populations are targeted by predators, this could greatly impact the amount of CPOM processed and thus affect FPOM levels within the stream.
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References
Vertebrates
Aquatic vertebrates in the stream systems of the Colorado Front Range consist entirely of fish. Non-native species currently dominate these stream systems. These include brown trout (Salmo trutta), longnose sucker (Catostomus catostomus), longnose dace (Rhinichthys cataractae), common carp, white sucker (Catostomus commersonii) and rainbow trout (Oncorhynchus mykiss).
Fish populations in the Front Range have been impacted in recent years by whirling disease, a parasite which infects and kills fish. Whirling disease first appeared in the United States in 1956 in Pennsylvania and since then has spread across the country (Bergersen and Anderson, 1997). It first appeared in the Colorado Front Range in the mid 1980’s and has been impacting fish populations since.
