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Stream ecology: concepts and case study of macroinvertebrates in the Skeena Watershed, British Columbia

by Alexander K. Fremier

INTRODUCTION

When hiking, it’s hard for me not to ponder the abundance of species and their apparent organization over the landscape. So, when swimming in a would one see similar patterns of species diversity? Species distributions are seemingly as well organized in flowing water as on land; yet, the processes controlling the patterns are quite unique to the aquatic environment. It is not hard to imagine that ecological patterns are dynamic in four dimensions, the usual three spatial ones and time. The spatial distribution of terrestrial plant species is limited by large physical processes such as temperature and precipitation as well as small factors, say proximity to a stream or topographic position. Time also plays a key role in distributions from seasonal to geologic time scales. This seems like a rather straight forward summary, however researchers have not always found linking pattern to process to be this simple. Physical processes driving species distributions in space and time tend to vary in importance from place to place and vary with the scale of inquiry; and, species respond to these factors in a range of ways. Stream systems provide a particularly complex web to untangle considering the dynamic ways in which it flows over and alters the landscape. Flow characteristics (such as velocity) change over small spatial scales, e.g. from the side of a to the main channel; they can change upstream to downstream and over many scales of time including seasonal flooding and glacial periods. Stream ecologists have aimed to describe these general patterns in various ways using a holistic approach infusing knowledge of and to explain energy flows and ecological patterns. A few main concepts formed the structure with which investigators started to grapple with stream complexity, including the (Vannote et al. 1980), resource-spiraling concept (Elwood et al. 1983), serial discontinuity concept (Ward and Stanford 1983), -pulse concept (Junk et al. 1989), and hyporheic corridor concept (Stanford and Ward 1993). The scientific community continues to debate the merits and limitations of these concepts. More recent discussions have moved away

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from a linear concept of stream systems and tend to emphasize scalar hierarchies and discontinuity concepts (Petts and Amoros 1996; Montgomery 1999; Rice et al. 2001). This paper aims to flesh out the insights of these early approaches and present them as sub-concepts in the overreaching framework that is more closely aligned with scientific thought on issues in stream ecology. The latter section of the paper focuses on applying these concepts to the Skeena River watershed in British Columbia, Canada.

CONCEPTS IN RIVER ECOLOGY

River Continuum Concept The river continuum concept (RCC) posited that the physical variables in river systems, from headwaters to mouth, presented a continuous gradient of physical conditions that drive the biological strategies and river system dynamics (Vannote et al. 1980). This was largely argued from the standpoint that energy input, organic matter transport, storage, and use by macroinvertebrates functional feeding groups (i.e. how an organism retrieves its food), may be regulated largely by fluvial geomorphic processes. The continuum is described in the longitudinal direction using where a first order stream has no and, depending on the system, the last order (usually > 6) runs into or the ocean directly. It states that the energy in the system for biological production at a given site is derived from three sources: local inputs or organic matter from terrestrial (allochthonous), primary production within the stream (autochthonous production), and transport of organic material from upstream. The proportion of these energy sources changes along the length of the stream (figure 1). The headwaters are dominated by terrestrial inputs or coarse particulate matter (e.g. leaf litter) with periphyton (algae attached to ) also present. Middle reaches are mixed with coarse particulate matter, periphyton and vascular hydrophytes (aquatic plants) as well as the fine particulate matter lost from upstream communities. Further downstream receive less terrestrial inputs due to the increase area to perimeter ratio of the river channel. Lower reach energy sources are dominated by phyto- and as well as the upstream fine particulate input. Periphyton and hydrophytes are not abundant at the lower reaches because high turbidity reduces penetration of sunlight. communities can persist in these waters due to the decreased slope and increased . In

Page 2 of 21 A.K. Fremier May 26, 2004 general, the RCC describes a gradient of energy inputs upstream to downstream of terrestrial inputs to in-stream production and associated downstream transport.

Figure 1: The river continuum concept by Vannote et al. 1980. The proportion of invertebrate feed groups corresponds to changes in the physical factors in the longitudinal direction (Figure taken from USDA 2001).

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Reflecting this gradient, macroinvertebrates populations are predicted to show a pattern relating to how they capture these energy sources. The right side of Figure 1 details how the proportion of feeding functional groups changes with stream order. The upper reaches are dominated by shredders and collectors, mid-reaches collectors and grazers, and low reaches by collectors. Collectors are species adapted to amassing fine particulate matter out of the water and therefore are predicted to increase downstream. Shedders in the upper reaches represent more of the macroinvertebrate species because of the increased allochthonous input, while grazers dominate the middle reaches due to the presence of in-stream production.

Resource-Spiraling Concept A related concept in stream ecology is the resource-spiraling concept (RSC) (Elwood et al. 1983). It sets forth the concept that resources do not flow continuously downstream like the RCC suggests but are stored periodically in biological packages (e.g. organisms, detritus and waste products). Resources are released after decomposition and then can be recycled into new biological production. This does not entirely change the RCC but adds to the dialogue the spatial and temporal fluxes of resources. For example, Minshall et al. (Minshall et al. 1983) suggested that upper basin tend to conserve or store resources through high biological activity and physical barriers to organic matter. Conversely, large streams have lower rates of biological activity and retention. In addition, as discussed the next section, there is a lateral pattern to resource dynamics (Junk et al. 1989). Namely, flooding adds a significant supply of resources into the stream system by bringing about interactions with the . Resource spiraling in this context adds a larger spatial and temporal dynamic by proposing that resource inputs into the stream system are not limited to leaf litter and upstream particulate matter. The stream system includes the adjacent riparian lands. In this context, resource spiraling can incorporate resources that are stored in the surrounding over longer temporal scales.

Serial-Discontinuity Concept The RCC and RSC assume little to no human involvement on the river system. The lack the structure to adequately deal with developed systems became a sticking point for opponents of the RCC (Johnson et al. 1995). They are argued that many, if not all, have some level of human impact such as construction, channelization or riparian clearing, and therefore the RCC has little applied value on these rivers, the exact rivers that are trying to be restored. In

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response, the serial-discontinuity concept (SDC) (Ward and Stanford 1983; Stanford and Ward 2001) was formulated and tried to incorporate impoundment into RCC. The SDC conjectured that even though were discontinuities in the river continuum, the RCC should still correctly predict the biophysical responses as a function of ‘discontinuity distance’ – upstream or downstream impact by dam. This concept, as well as the RCC, has been criticized by more recent studies because it lacks the construct to deal with the lateral and vertical dimensions of river systems. Recently, Stanford and Ward (Lamouroux et al. 1995) incorporated floodplains into the SDC and continue to maintain its efficacy as a predictive tool.

Flood-Pulse Concept In contrast to the RCC, the flood-pulse concept (FPC) was derived on large floodplain rivers in temperate and tropical areas that caused investigators to consider the role of seasonal flooding in lotic systems (Junk et al. 1989). The RCC could be acceptably modified to account for brief and unpredictable in low-order streams; however, researchers recognized that as the size of a floodplain increased, the frequency of floods decreased, yet their predictability increased. This suggests that larger streams have a more stable flood regime. This predictability, they hypothesized, of the stream/floodplain exchange should result in adaptation of biota distinct from those species in streams dominated by stable lotic or lentic . Therefore, the FPC states that the most important hydrologic feature of large rivers is the annual flood pulse. Junk et al. (Junk et al. 1989) postulate that in unaltered large river systems with floodplains in the temperate, subtropical, or tropical belt, “the overwhelming bulk of the riverine animal derives directly or indirectly from production within the floodplains and not from downstream transport of organic matter produced elsewhere in the basin” (1989 page 112). In general, the main difference between the two concepts is the process of how resources are input into the system in large rivers. From the aquatic standpoint, the FPC recognizes that the predictable advance and retraction of water on the floodplain is the principal agent controlling the adaptation of most of the biota. Flooding, therefore, is not a disturbance, but a natural property on which the system depends. The FPC postulates that the flood pulse enhances biological and maintains diversity in the system through the seasonal interactions between plants, nutrients, detritus and in the floodplain. Junk et al. (1989) describe the aquatic/terrestrial transition zone

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(ATTZ), or moving littoral zone (area between low and high flooding) as the major zone of activity (figure 2). Flood waters pick-up nutrients from the floodplain that have been mineralized on land and redistribute them through the system. respond to the rising waters by spawning before or during the water’s rise. While the stream water is rising, fish and invertebrate production is high due to the release of nutrients from newly inundated soil (figure 2). Increased floodplain inundation also creates new nursery for fish and optimal environments for many invertebrate especially those allied with macrophytes.

Figure 2: The (Junk et al. 1989) argued that the effect of the complex interaction between floodplain and lotic system was not taken into account in the RCC (Figure taken from USDA 2001).

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Hyporheic Corridor Concept The hyporheic corridor concept (HCC) added to riverine ecology the pattern and importance of interactions in understanding biological patterns (Stanford and Ward 1993). The is the area below the contact point of water and the stream bed where water percolates through spaces between the rocks and cobbles, i.e. the interstitial space. The strength and direction of interaction between surface and groundwater transpires at multiple spatial scales (figure 3).

Figure 3: This diagram shows the hyporheic zones in the lateral dimension at multiple scales. (a) the HCC predicts gradients in relative size of the HZ, water retention and size, (b) at the reach scale, and downwelling zone alternate, generating gradients in nutrients, dissolved gases and subsurface fauna, and (c) at the sediment scale microbial and chemical processes occur on surfaces, creating microscale gradients (Boulton et al. 1998).

This physical pattern drives the biotic response. The hyporheic zone is home to copepods, aquatic earthworms, rotifers, midges, and early instars of other aquatic insects; they are mostly

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collector-gatherers or predators. Many stoneflies (Order Plecoptera) live their entire aquatic life in this zone. The importance of this concept to stream ecology is that it emphasizes the vertical dimension on streams at both the lateral and longitudinal dimension and through time. Moreover, it is an example of the development in thought that recognizes a discontinuous pattern in the longitudinal direction; in addition it directly includes the lateral and temporal components of the fluvial process and biotic patterns.

Shortcomings of Traditional Concepts Increased habitat heterogeneity and high productivity in larger rivers is thought to be the main cause of the high species diversity in larger river systems according to the FPC. The RCC, however, does not predict this pattern. It argues that the highest species diversity occurs in mid- order streams excluding higher order stream species that do not dwell in the active channel. The FPC argues that backwater habitats and species affected by the ATTZ should be included into diversity indices. Inclusion would make lower reaches extremely diverse and productive. Regardless of how the RCC and FPC measure diversity, the addition of flood pulsing into stream ecology is an important contribution. Empirical tests of the RCC and subsequent conceptual arguments quickly showed that it may not apply to large rivers, particularly with extensive floodplains (Bayley and Li 1992) and in arid regions (Davies et al. 1994). However, other reports on the (FPC) and the Salmon River in Idaho (RCC) showed that predictions of both concepts are upheld when floodplains are considered a significant variable. That is, the RCC did not function well on a floodplain river, but did on the Salmon River due to the fact that it is a constrained river with no lateral interaction with a floodplain. Analogously, the river areas on the Amazon River with the most interaction with floodplain were the most productive as concordant with the FPC. In general, these concepts are not mutually exclusive. They emphasize two main points in stream ecology: 1) the lateral and longitudinal dimensions of streams, and 2) the importance of geographic setting (geomorphology and hydrology). The RCC described the longitudinal dimension of river systems while the FPC emphasizes the lateral dimension in floodplain rivers. The of large river flooding encourages biota to adapt to the flood pulse while the stochastic and flashy nature of mid-to-headwater stream systems does not allow for this transformation. The hydrologic and geomorphic setting of a river constrains the universality of

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each concept. The FPC argued that the RCC was inaccurate in larger river systems due to increase floodplain interaction including side channels and oxbow , yet is confined itself to only those rivers with an ATTZ. The question remains whether if both concepts can be incorporated into one. As was noted when contrasting the RCC and the FPC, river systems vary due to the geographic setting, e.g. with a floodplain versus without. So what other system properties have the potential to alter river processes and patterns? The RCC and FPC are principally linear concepts. They assume that processes essentially function in the longitudinal and lateral dimension. Linear models in ecology have largely been thrown out because they rarely fit empirical data. More recent approaches emphasize patch mosaic dynamics and nested hierarchies (Pringle et al. 1988; Petts and Amoros 1996; Poole 2002). That is, riverine systems should be view as a mosaic of patches rather than a continuum and/or as higher levels of organization that change more slowly and provide the context within which lower levels function. For example, sediment particle size is a small scale pattern governed by a small scale process, i.e. flow characteristics. Smaller scale processes are contained with larger processes, such as a particular or . The present hypotheses largely assume that the physical characteristics drive the biological. On small scales this might not always be true. Local abundances of species and resource use can be controlled by community interactions such as (Power et al. 1995). In a given river profile the channel biota might be dominated by physical forces while in backwaters, community dynamics might control species interactions. Both the RCC and the FPC assume a dynamic equilibrium between the biological and physical features. Equilibrium theory focuses attention on the properties of the system at an equilibrium point, to which the community tends to return after a disturbance (Begon et al. 1996). This assumption has been difficult to accept in river systems that are dynamic and highly altered by humans (i.e. the serial- discontinuity concept). Current hypotheses for lotic systems are essentially descriptive and do not isolate the mechanism directing the pattern. Better methods and tools are needed, not only to guide management, but also to predict a river’s physical and biological characteristics along its length (Gore and Shields 1995; Power et al. 1995). More recent concepts are stronger than traditional approaches as they isolate the process driving the pattern (Benda et al. 2004); but, they are more limited in their scope.

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Contemporary Concepts The concepts discussed thus far have shown to be too simplistic for predicting the true pattern and process of stream systems worldwide. Although they have not been thrown out completely, they are still useful on a single river depending upon the geographic setting and the temporal and spatial scale of the analysis (Schiemer and Zalewski 1992). Moreover, they have a significant heuristic value for studies in stream macroinvertebrate ecology. One useful concept for understanding the stream systems is the fluvial hydrosystems approach (FHA). It is based on the idea that limiting analyses to the longitudinal and temporal dimensions is too simplistic to understand the true complexity of river systems. The FHA suggests that rivers should be viewed as three-dimensional systems (figure 4) over time (the 4th dimension) dependant on longitudinal, lateral and vertical transfers of energy, material and biota (Petts and Amoros 1996). Upstream to downstream fluxes (e.g. RCC, RSC, SDC), lateral interactions with the riparian area (e.g. FPC), and vertical exchanges with the groundwater of the alluvial (e.g. HCC) are all important.

Figure 4: The Fluvial Hydrosystem approach to understanding river systems emphasizes the lateral, longitudinal, and vertical dimensions (Petts and Amoros 1996).

The approach relates the variability of hydrological and geomorphological processes that determine the types of habitat patches present and the strength, duration, and frequency of their connectivity. It emphasizes bidirectional interactions between environmental variables and biological populations over a range of spatial and temporal scales. Another key interpretation of this approach is to look at the systems as a nested hierarchy of subsystems. Meaning, various processes act on various levels, which in turn create patterns of diversity at various levels. As

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described in the RCC and FPC, macroinvertebrate distributions are principally controlled by fluxes of resources acting along longitudinal and lateral gradients. However, at a meso-scale groups of taxa tend to arrange in pools and adjacent (HCC). At smaller scales, such as the microscale, species within a pool organize laterally within the channel primarily due to the shear stress of water flow. The scale of interest determines the scale of inquiry. Furthermore, the variables controlling species distributions most likely vary between stream systems and location along the stream network (Poole 2002; Benda et al. 2004). The recent emphasis of stream ecology away from continuous concepts into discontinuous has further joined the disciplines of stream ecology and geomorphology (Poole 2002). The patch or hierarchy approach now recognized acknowledges the intermittent nature of hydro-geomorphic processes in the longitudinal dimension. Analysis of the physical processes is used to classify rivers into smaller units (Montgomery and Buffington 1997). See Figure 5 for an example. Using a well-defined river classification schema, ecologists compare biota within and between nested channel reaches to construct a more accurate and predictive model. In addition, reaches have been broken down further into smaller units incorporating effects (Rice et al. 2001; Benda et al. 2004). This recent concept acknowledges the importance of tributary inputs (namely sediment and ) that result in discontinuous downstream patterns.

Figure 5. This is an example of how stream reaches are dissected by geomorphologists. It is a schematic of longitudinal profiles of alluvial channel profiles at low flow: (A) cascade, (B) step pool, (C) plane bed, (D) pool , and (E) ripple.

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These concepts represent a fundamental shift in perception in stream ecology. They emphasize the relationship between pattern and process at multiple scales. The approach is multidimensional in that it melds patterns observed at three spatial dimensions through time. However, it is important to notice that the antecedent concepts have not been wholly thrown out, but have been refined and united into a more overarching framework. To illustrate this idea the next section details a specific application of these concepts to the Skeena River and its tributaries.

APPLICATION IN THE SKEENA WATERSHED

This section examines the ways in which the heterogeneity of aquatic habitats influences the distribution of invertebrate communities at multiple spatial scales. A few basic questions will be addressed: how do we begin to analyze the distribution patterns related to the degree of connectivity with the river system at the macro-, meso- and micro-scales? What might be the distribution of macroinvertebrates between tributaries that are glacial, or feed or clear water streams? And, how do channel networks and affect the ecological patterns? In general, the analysis here will focus on how the theoretical concepts might predict macroinvertebrate population distributions throughout the system.

Geographic Setting The Skeena River is the largest river in North America unaffected by human alteration (Dynesius and Nilsson 1994). It flows 570 kilometers out of the Canadian Rocky Mountains through mixed mountain and highland system with complex zonation into the Pacific Ocean (figure 6). It drains a total area of 54,400km2. The geomorphic pattern of the river conforms to that of a typical stream to river system - steeper head water streams that flow into progressively larger , flat bottom rivers. The Skeena is best known for the anadromous fish runs it supports. There has been only minimal human influence in the watershed – mining, timber harvest and commercial fishing – making the watershed a particularly unique location to study natural and non-impacted macroinvertebrate population dynamics.

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Figure 6: Location map of the Skeena River

The Skeena River hydrology is strongly seasonal. Unlike most temperate rivers the Skeena River has a flood-pulse that comes twice a year (figures 7-9). The initial pulse comes as temperatures rise (April-October), peaking in June. In the late fall months of September and October a second, smaller peak appears with the return of the winter storms. The winter months on the Skeena see lower flows due to the fact that most precipitation falls as snow. Figure 7 shows flows on the Skeena near Usk, BC and Figure 8 shows a smaller but similar pattern of flow upstream of the with the Babine River. There is a clear patterned flood pulse (figure 9).

Figure 7: Mean daily discharge for the Skeena River at USK. Note the patterned flood pulse in both the and fall. Water Resource Branch of Canada, 2004.

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Figure 8: Mean daily discharge for the Skeena River above the Babine River. Note the patterned flood pulse, both in spring and fall (Water Resource Branch of Canada, 2004).

4,500

4,000

3,500 ) s 3,000 (cm

2,500 scharge i 2,000 e D

ag 1,500 ver A 1,000

500

-

v n r r n g p v c b o a a p u u e o e e N J M A J A S N D F Calender Day

Figure 9: Average of all mean flow per calendar day on the Skeena River at Usk. Plotted with 1 standard deviation from the mean to show that flooding is a highly regular pattern (Water Resource Branch of Canada, 2004).

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Stream Macroinvertebrates A logical way to organize the stream macroinvertebrates of the Skeena is by scale. At the macro- or catchment scale, the headwater communities are compared to lowland, i.e. a similar concept described in the RCC. The headwater sections of high altitude, high slope, turbulence and low temperatures change in the downstream direction into depositional, warmer, lowland reaches. Figure 10 shows an example of how the organisms might be organized. Depending on the source, most upstream habitats (namely springs) have a typical fauna (A) and give way to an assemblage of species adapted to fast flowing water (B). As the river enters the floodplain a new assemblage can be identified with species adapted to the slow moving, depositional zone (C), which leads to estuarine assemblages tolerant of saline conditions (D). At the transition point between each section of the river there is an overlap of taxa, with some species unique to each transition zone (T) (Greenwood and Richardot-Coulet 1996). An example of this transition occurs between the and stoneflies. In BC mayflies (Order Ephemeroptera) live in flowing or still water. The nymph feeds on algae, diatoms, and organic matter. Mayflies are characteristic of lower, warmer sectors of stream. The stoneflies (Order Plecoptera) are regarded as cold-water species. Stonefly nymphs require well oxygenated water so are consequently found in rivers and streams amongst the rocks and bottom debris; however, a few species can be found in the rocky of cold lakes. It is important to know however that these are the characteristic locations of the immature stages of these insects and that since the adult stages are mostly aerial, the system should be considered open.

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Figure 10: Diagram of the longitudinal dimension of river systems proposed by the FHA. (Petts and Amoros 1996)

At the mesoscale, riffle-pool sequences create divergent habitats characteristics. Examples of taxa strongly tied to riffles are Ephmeroptera, Tricoptera (), Plecoptera, and Simuliidae (Order Diptera, Blackflies). These groups are adapted to the high velocities of the channel (riffles compared to pools). Many take on the flows by anchoring themselves to the stream bed using a range of mechanisms (figure 11). In Figure 11, the mollusk has a stream lined shell designed to reduce shear stress and sticks to the bottom of the stream by ‘sucking’ on to the irregular surfaces. Likewise the blackfly larvae attaches itself to the stream bed and raises filaments to catch passing detritus. Alternatively, members of the orders of Odonata, Diptera, Coleoptera (Dytiscidae, diving beetles) and some Tricoptera are abundant in neighboring pools. In larger meandering streams species are distributed over the diverse habitats provided by the hydro-geomorphic dynamics of the river, such as cutoffs, braided stream beds, and bends.

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Figure 11: Adaptations by macroinvertebrates to live in flowing water. See text for details. (Petts and Amoros 1996)

Analysis at a microscale shows a variable environment which creates a mosaic of microhabitats for the macroinvertebrates. The specific characteristics of the mosaic depend on the characteristics of the catchment at a specific time. Within a riffle or a pool species are adapted to the transient nature of the mosaic. Some species take up positions in areas where there is a stable food supply such as the head of the riffle. Certain species may move from patch to patch as their life cycle progresses. Along the banks and margins, the water level and shape of the channel section creates a variety of habitats as well. The tributaries of the Skeena have varied characteristics. Three main types exist: clear water, glacial feed, and peatland drain streams (pers. comm. J. Mount). Each has their unique physical characteristics, including the water chemistry and amount of fine particulate matter. Each of these will play a significant role in macroinvertebrate patterns. The tributaries would

Page 17 of 21 A.K. Fremier May 26, 2004 probably have few species in common, the chironomids excepted; yet, they should have similar distribution of functional groups. Glacial fed streams tend to be primarily diatom based with very little primary production due to low light availability; while peatland feed streams have mostly fine particulate organic matter of low energetic value that is hard to break down. Glacial stream communities tend to have a Diamesanae based chironomid community, whereas peatland acid- based drainage communities are acid tolerant, low oxygen species such as Chironomus and Paratendipes (Erman 2004). Clear waters stream will have bit of everything with a high diversity. The organization of biota within these streams between reach lengths will differ due to the immediate hydrology. One can imagine that the cascade reach offers a vastly different set of physical parameters than does a dune-ripple reach (Refer back to Figure 5). Sediment supply and transport capacity should affect macroinvertebrate distributions in unique ways between the tributaries; yet, theory predicts that patterns should arise due to similar geomorphic and geographic conditions. Two interesting, and largely unexplored, questions come to mind regarding the distribution of macroinvertebrates on the Skeena River. The first is to analyze the three types of tributaries for patterns in species and functional group distributions. On the tributaries to the Skeena testing the predictability of the RCC might be the most appropriate. Here there are three types of rivers varying in physical conditions; yet, there are similar is many respects as well, including connectivity to the Skeena and climatic factors. From the head of each stream to where it meets the Skeena, do these streams conform to a pattern predicted by the RCC? Knowledge of similar systems informs us that clear water streams have the most promise, but if the theory is correct, it should hold true in more extreme less diverse communities such as glacial and peatland feed streams as well. The second is to look at the effect of tributaries on the geomorphology and biotic distribution. Rice et al. (Rice et al. 2001) empirically tested a discontinuity concept (Link Discontinuity Concept) by completing a longitudinal profile of a set of streams recording both the physical conditions, such as sediment size, water temperature, pH and width, and macroinvertebrate species abundances. The pattern of biota could be attributed to the character of the input source. A similar analysis could be completed at the geomorphic scale (e.g. riffle or pool) or at a channel cross section to look at the lateral dimension of tributary influence.

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The Skeena watershed offers a unique example of a near pristine system with an interesting array of streams to study macroinvertebrates, and in particular, the effects of tributaries and source waters on stream biota. For the purposes here, application of conceptual models provided a glimpse into how investigators view the biological diversity in streams.

CONCLUSION

Stream ecology research has largely focused on describing processes that effect biotic distributions. Research has identified the merits and limitations of proposed conceptual models. The objective of this paper was to review the predominate concepts of stream ecology and try to synthesize the main themes. It is clear that the waters are still muddy. However, of the concepts examined few were contradictory; in fact, they were quite the opposite. Arguably the first large scale concept in stream ecology (the RCC) is still incorporated into contemporary conceptual models, albeit in a more restricted version. The RCC emphasized the longitudinal dimension, the FPC the lateral, and the HCC the vertical. They were fastened together in the FHA for largely heuristic value. Research has shown that the RCC tends to be inaccurate in large floodplain river systems due to the great influx of material brought into the system by seasonal flood inundation patterns. The RSC offered a structure with which to understand resource fluxes in lotic waters both downstream and through floodplain features. The RCC was further refined when human influence was factored in. The SDC argued that impoundment affected the longitudinal continuum described in the RCC. The concept of discontinuity is being activity researched today. This research has benefited from integration with landscape ecology and again from geomorphology. Landscape ecology offered the view of system patterns acting in a nested hierarchy while geomorphology describes process-based stream classifications schemes as well as the effects of tributaries. Application of these concepts in the Skeena River was for the most part conceptual, although it offered a tangible approach to understand and formulate research questions in the area of stream ecology. This connection between concepts and application will help those interested in understanding the environment around them, allowing even the most casual observer to interlink process and pattern as they go for a dip in their favorite swimming hole.

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