2010 S.C. Water Resources Conference - Science and Policy Challenges for a Sustainable Futur

Marion, Cathy A

Scott, Mark C

English

Clemson University: TigerPrints

INFLUENCE OF LAND USE ON IN-STREAM SUBSTRATE AND SINGLE-METRIC FISH INDICATORS IN SOUTH CAROLINA COASTAL PLAIN STREAMS  Cathy A. Marion, Mark C. Scott _______________________________________________________________________________________ AUTHORS:  Research Biologists, South Carolina Department of Natural Resources, 311 Natural Resources Dr., Clemson, SC 29631 REFERENCE:  Proceedings of the 2010 South Carolina Water Resources Conference, held October 13-14, 2010, at the Columbia Metropolitan Convention Center _______________________________________________________________________________________      Abstract.  The South Carolina Department of Natural Resources initiated a statewide stream assessment (SCSA) in 2006 to evaluate the status of aquatic resources throughout the state, to understand how aquatic species composition varies across the landscape, and to study how human activities can disrupt the processes linking terrestrial and aquatic systems.  The identification and prediction of land use impacts on stream habitat and biological communities constitutes an essential, basal component of South Carolina aquatic resources management. However, there remains a sparsity of studies concerning land use change and subsequent effects on stream habitat and fish assemblages within South Carolina’s coastal plain.  We utilized data from 79 wadeable streams across three coastal plain ecobasins (sampling region based on EPA level IV ecoregion and major drainage basin), including the ACE Carolina Flatwoods, the Pee Dee Carolina Flatwoods, and the Pee Dee Atlantic Southern Loam Plains to evaluate relationships among regional catchment land use, in-stream substrate habitat, and four fish metrics.  This preliminary analysis used path analysis to evaluate a) the relative importance of large wood habitats to coastal plain fishes, and b) the relative influence of regional (catchment land use variables) versus local (in-stream substrate habitat variables) influences on coastal plain fish metrics.  Model results indicated that the relative pattern and strength of relationships between fish metrics and habitat / catchment land use were dependant upon the type of biological data used. Simple fish metrics richness and Shannon diversity showed positive, direct relationships with large wood occurrence, and indirect positive relationships with regional catchment land use, i.e. minimal forest loss.  Large wood acts as an intermediate response variable between landscape disturbance and simple fish metric response.  As natural forested coastal plain landscapes are lost, declines are observed in the occurrence of large wood, and cumulatively these terrestrial and habitat disturbances result in decreased richness and diversity of coastal plain fish assemblages. Complex metric guild breadth (a measure of functional diversity) was approximately equally influenced by regional land use (agrarian land use change over time) and local habitat (large wood), suggesting that the structure of coastal plain fish assemblages is determined by factors operating at multiple spatial and temporal scales.  In contrast, complex endemic abundance (abundance of Atlantic slope coastal plain endemic species) showed diminished strength of relationships with large wood and stronger, direct relationships with catchment-level landscape variables, minimal forest loss, and reversion of land from active row-crop agriculture to passive grassland/pasture.  Observed reductions in endemic taxonomic groups were more strongly associated with larger spatial and temporal-scale phenomena than with local in-stream habitat conditions. These results indicate that landscape perturbations active at larger spatial and temporal scales may play a greater role in the actual distribution of endemic coastal plain fishes than local habitat conditions.   INTRODUCTION      Numerous studies have emphasized the significance of large wood to southeastern coastal plain fishes; however few have investigated the interrelationships among catchment land use, large wood habitat, and assemblage structure.  The biotic composition of streams is inextricably linked to both in-stream habitat structure as well as terrestrial landscape features.  Large wood is the dominant source of in-stream habitat structure, and acts as a habitat ‘former’ in southeastern coastal plain streams.  Anthropogenic land disturbances such as deforestation (Jones et al. 1999), row crop agriculture (Lester and Boulton 2008), and urbanization (Paul and Meyer 2001) are known to alter in-stream habitat conditions, and have been well studied in southeastern piedmont and upland streams.  While the significance of large wood to coastal plain streams is well established (Benke 1995), the patterns of anthropogenic disturbance and pathways in which they alter coastal plain in-stream habitats and fishes remains largely unknown.  Of ultimate concern is that these terrestrial and habitat disturbances may potentially exceed individual tolerance limits and influence biotic interactions of aquatic organisms, a causal pathway that may ultimately alter biological structure (Karr 1991).     The objectives of this study were to 1) evaluate the importance of large wood to coastal plain fish assemblages relative to other habitat substrates, using two types of fish metrics, two simple numeric summary metrics (richness, Shannon diversity) and two complex metrics measuring aspects of assemblage functional (guild breadth) and taxonomic characteristics (endemic abundance), 2) identify relationships among catchment land use, in-stream substrate habitat, and fish metrics, 3) determine whether current catchment land use or catchment land use over time provides a better explanation of fish assemblage metrics and in-stream habitat, and 4) assess the relative influence of regional (catchment land use variables) versus local (in-stream habitat substrate variables) on coastal plain fish metrics.    METHODS      Data for this study are a subset of a larger evaluation of statewide aquatic resources initiated by the South Carolina Department of Natural Resources, termed the South Carolina Stream Assessment (SCSA).  Seventy-nine wadeable streams located across three coastal plain ecobasins (sampling region based on EPA level IV ecoregion and major drainage basin), including the ACE Carolina Flatwoods, the Pee Dee Carolina Flatwoods, and the Pee Dee Atlantic Southern Loam Plains were sampled for fishes and habitat; additionally, watershed land use for each sample location was derived (see Scott 2008. for details).      We utilized path analysis (Shipley 1997) using AMOS (PASW Statistics ™ v.17, AMOS™ v. 17).  Path analysis is a form of structural equation modeling that measures both direct and indirect causal relationships among variables. Our models defined direct relationships of land use ! fish metrics, land use ! in-stream substrate, in-stream substrate ! fish metrics, and indirect relationships of land use ! fish metrics via an in-stream substrate mediator variable.  Path analysis was chosen because the structure of our data was spatially hierarchical in nature; landscape level variables may be have both a direct (implicit relationship between land use and fish metric) and/or indirect (the impact of land use on fish metrics is mediated by an influence on the physical habitat (i.e. substrate) within coastal plain streams) effect on fish metrics.       RESULTS AND CONCLUSIONS      Path analysis models indicated that the relative strength of relationships between large wood occurrence and simple metrics richness and Shannon diversity were strongly and directly influenced by local large wood habitat. Guild breadth was also strongly and directly influenced by large wood habitat, but also directly influenced by catchment land use variables. The importance of large wood to coastal plain fish assemblages is not surprising, and associations between large wood and increased richness and diversity have been documented by various researchers (Angermier and Karr 1984).  Large wood is a major habitat-forming feature in coastal plain streams.  It influences stream morphology by altering velocity and depth, and can transform a coastal plain stream of uniform depth and velocity into a dynamic hydrological system with wood-formed runs, pools, and even riffle profiles (Lester and Boulton 2008).       One confounding issue in this analysis is the interdependency between large wood and the complex of habitat features that it can create.  The interdependency among habitat features (e.g. large wood, depth, velocity regime) can create difficulties when attempting to isolate one factor and establish cause and effect relationships with landscape disturbances, or change in biota (Smokorowski and Pratt 2007).  In this study, we focused on large wood rather than other potentially related variables, in part because of its documented habitat transformation properties.  For example, increased depth is a known function of woody debris dams; often the most important function of large wood is in creating and maintaining pool habitat (Fausch and Northcote 1992).  In this study, we found a significant positive correlation between depth and large wood (unreported data).  While others have found depth to be a significant factor in determining coastal plain fish richness (Sheldon and Meffe 1995), we believe the two variables to be interdependent, with depth acting as a function of large wood.       The general pattern elucidated from the path analyses indicated that traditional metrics richness and Shannon diversity were most strongly predicted by local habitat conditions of increased occurrence of large wood.  Concurrently, there was an increased occurrence of large wood in landscapes with minimal urban cover, and minimal forest loss over time, inferring an indirect relationship between richness and diversity and these land cover types.  Guild breadth was approximately equally influenced by regional land use (agrarian land use change over time) and local habitat (large wood), suggesting that the structure of coastal plain fish assemblages is determined by factors operating at multiple spatial and temporal scales.  In contrast, endemic abundance was solely determined by regional landscape factors (minimal forest loss and maximal agrarian loss), and was unrelated to local habitat conditions.    Richness and Shannon Diversity     The path analysis revealed that local in-stream wood habitat was the strongest driver of observed richness and diversity (direct relationship), and increased large wood occurrence was found to be related primarily to undisturbed, forested coastal plain catchments (indirect relationship) (Table 1, Figure 1a, 1b).  This indicates that the abundance of in-stream wood is dictated, in part, by the surrounding landscape.  Secondly, these findings indicated that as the natural forested coastal plain landscape is lost, and possibly replaced by human dominated agrarian and urban landscapes, we see declines in large wood, and cumulatively these regional (catchment) and local (in-stream habitat) disturbances result in decreased richness and diversity of coastal plain fish assemblages.  These findings highlight the importance of maintaining natural, undisturbed forested landscapes to coastal plain aquatic systems.    Guild Breadth     Guild breadth was intended to be a simplified measure of functional diversity.  The path analysis revealed almost equal, direct roles of factors representative of regional and local scales, indicating that both regional land use (agrarian land use change over time) and the local habitat template (large wood occurrence) synchronously influence the observed functional structure of coastal plain streams (Table 1, Figure 1c).  The top five guild categories lost in streams with reduced occurrences of large wood, and increased active maintenance of agrarian landscapes over time included benthic oriented fishes, plant/wood spawners, benthic omnivores, benthic invertivores/piscivores, and benthic invertivores.  Common species lost under disturbance scenarios included darters, madtoms and bullheads, suckers, topminnows, coastal minnow species, pygmy sunfish, swampfishes, and eels.     The direct relationship between guild breadth and large wood is evident.  Streams with complex habitats formed by large wood tend to have more fish and fish species than streams lacking complexity (Dolloff 2003).  In addition to diversifying depth and velocity regimes, large wood can partition habitat and visually isolate individual fish, allowing more fish per unit of available space.  This is commonly called the ‘condominium effect’, and gives credence to habitat partitioning.  In this study the observed communities of warmwater fish exhibited a greater breadth in habitat preferences, reproductive, and  feeding behaviors in streams with increased occurrences of large wood.      Unlike the relationship with large wood, the relationship between agrarian landscapes and guild breadth as measured by this study is less of a direct mechanism and more reflective of a cumulative suite of impacts associated with agriculture.  Because we found there to be a net loss in agrarian land over time, results indicated that there is some advantage or positive aspect to abandoning row crop agriculture.  An examination of raw spatial data indicated that agrarian land lost was most likely to revert to grassland or pasture, an arguably less intensive land use practice.  The negative repercussions of agrarian landscapes on fish communities have been well documented by other studies throughout the United States (Allan 2004); this ubiquitous suite of stressors are likely applicable to South Carolina’s coastal plain.         Endemic Abundance     Catchment land use, rather than the local habitat template was found to influence the observed abundance of coastal plain endemic species.  Land use variables minimal forest loss over time and maximal agrarian loss over time were found to play a dominant role in the distribution of coastal plain endemics; conversely, habitat conditions were insignificant (Table 1, Figure 1d).  We found the lack of relationship with large wood both counter-intuitive and surprising, primarily because most of South Carolina’s coastal plain endemics depend strongly on large wood habitats for some or all components of their life cycle.       The greater relative importance of regional land use change factors in determining coastal plain endemic abundance and distribution may be an artifact of past landscape disturbances that have effected these species ability to persist and disperse from source pools.  We can assume that historic impairments have impacted the distribution of SC coastal endemics; however uncertainty remains as to when impairments occurred and specific mechanisms active within landscapes that have caused declines.  However, our results indicate that streams within minimally disturbed landscapes or ‘healing’ landscapes are more conducive to housing endemic species.  This may indicate that it is possible to restore an endemic constituency by allowing landscapes to revert back to more natural conditions.  Unfortunately, little is known regarding the dispersal ability of many coastal plain endemics.  However, coastal plain fishes may be more readily able to mobilize and disperse due to a high natural connectivity of coastal water systems compared to their upland counterparts.  This supposition is reinforced by the fact that more endemics were found is systems actively undergoing a land reversion away from  Table 1: Summary results for path analysis showing significant model predictors, the standard strengths of both the direct and indirect effects of land use on in-stream substrate and fish metrics, and non-causal effects.    agriculture and towards an arguably more benign grass/ shrub landscape.  This phenomenon may indicate that endemic populations have the ability to rebound more quickly than we realize form agrarian and deforestation disturbance scenarios.  We do know that coastal plain endemics have evolved to withstand episodic cycles of     Figure 1: Path analysis models for mish metrics. Significant relationships (p! .05) indicated by solid-line arrows between variables. Standardized strengths and directions of relationship indicated by partial regression coefficients standardized for error. Figure 1a—richness; 1b—Shannon diversity; 1c—guild breadth; 1d—endemic abundance. hydrological abundance and drought; they are likely programmed to disperse quickly when suitable conditions  emerge.   LITERATURE CITED  Allan, J. 2004. Landscapes and riverscapes: the influence   of land use on stream ecosystems. Annual Review of   Ecological Evolutionary Systems 35:257-284. Angermeier, P. and J. Karr. 1984. Biological integrity   versus biological diversity as policy directives.   BioScience 44:690-697. Benke, A. 1995. Importance of snag habitat for animal   production in southeastern streams. Fisheries 10:8-13. Dolloff, C. and M. Warren. 2003. Fish relationships with   large wood in small streams. American Fisheries   Society Symposium 37, 179-193. Fausch, K. and T. Northcote. 1992. Large woody debris   and salmonid habitat in a small coastal British   Columbia stream. Canadian Journal of Fisheries and   Aquatic Sciences 49:682-693. Jones, E., G. Helfman, J. Harper, and P. Bolstad. 1999.   Effects of riparian forest removal on fish assemblages in   southern Appalachian streams. Conservation Biology   13:1454-1465. Karr, J. 1991. Biological integrity: a long-neglected   aspect of water resource management. Ecological   Applications 1:66-84. Lester, R. and A. Boulton. 2008. Rehabilitating   aqricultural streams in Australia with wood: a review.   Environmental Management. 42:310-326. Scott, M. 2008. A probabilistic stream assessment to   support freshwater conservation: preliminary results   from the coastal plain. Proceedings of the 2008 South   Carolina Water Resources Conference, held October   14-15, 2008, at the Charleston Area Event Center. Sheldon, A. and G. Meffe. 1995. Path analysis of   collective properties and habitat relationships of fish   assemblages in coastal plain streams. Canadian Journal   of Fisheries and Aquatic Sciences 52:23-33. Shipley, B. 1997. Exploratory path analysis with   application in ecology and evolution. The American   Naturalist 149:1113-1138. Smokorowski, K. and T. Pratt. 2007. Effect of a change   in physical structure and cover on fish and habitat in   freshwater ecosystems – a review and meta-analysis.   Environmental Reviews 15:15-41. Paul, M. and J. Meyer. 2001. Streams in the urban   landscape. Annual Review of Ecology and Systematics   32:333-365. 

Influence of Land Use on In-Stream Substrate and Single-Metric Fish Indicators in South Carolina Coastal Plain Streams

https://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=1120&amp;context=scwrc

Influence of Land Use on In-Stream Substrate and Single-Metric Fish Indicators in South Carolina Coastal Plain Streams

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