8382000 Estuarine Research Federation Estuaries Vol. 23, No. 6, p. 838–853 December 2000



# Responses of Tidal Creek Macrobenthic Communities to the Effects of Watershed Development

S COTT 

### B. LERBERG 1, 

### *, A. FREDERICK 

### H OLLAND 2 

### , and D ENISE 

### M. SANGER2

1 

### Virginia Institute of Marine Science, School of Marine Science, P. O. Box 1346, Gloucester Point, Virginia 23062

2 

### South Carolina Marine Resources Research Institute, 217 Fort Johnson Road, Charleston, South Carolina 29422

ABSTRACT: This study examined the effects of watershed development on macrobenthic communities in tidal creeks of Charleston Harbor, South Carolina, U.S. Two types of creeks were evaluated: upland creeks which drained watersheds consisting of at least 15% terrestrial land cover, and salt marsh creeks which drained no upland habitat (i.e., only intertidal habitat). Samples of macrobenthic organisms were taken along the longitudinal axis of twenty-three primary (first order) tidal creeks. Water and sediment quality data were also collected including measurements of dissolved oxygen, salinity, temperature, sediment characteristics, and toxic chemicals in the creek sediments. Hypoxic conditions occurred more than 15% of the time in both reference and developed creeks and were a natural attribute of these systems. The most severe and frequent hypoxia occurred in impacted salt marsh creeks. Salinity fluctuations were the greatest in developed upland creeks and salinity range was identified as a potentially reliable indicator of the degree to which watershed development has altered hydrodynamic processes. The creeks draining urban and industrial watersheds were degraded environments characterized by watersheds with high ( 50%) levels of impervious surface, broad fluctuations in salinity, severe hypoxia, and potentially toxic levels of chemicals in the sediment. These creeks had low macrobenthic diversity and abundance and were numerically dominated by the oligochaete Monopylephorus rubroniveus in mud sediments, and the polychaete Laeonereis culveri in sand sediments. Suburban watersheds had 15–35% impervious surface and creeks draining them were exposed to frequent hypoxia and broad salinity fluctuations. The levels of chemical contaminants in sediments of suburban and impacted salt marsh creeks were generally not different from the levels in reference creeks. Macrobenthic diversity and abundance were higher for suburban and impacted salt marsh creeks than for urban and industrial creeks. However, suburban and salt marsh impacted creeks were numerically dominated by a few pollution indicative species including the oligochaetes M. rubroniveus and Tubificoides brownae and the polychaete L. culveri. These creeks appear to be exhibiting early signs of degradation (e.g., a simplified food web). Two promising community-levelmacrobenthic metrics for assessing environmental quality were identified: the proportional abundance of pollution indicative taxa, and the proportional abundance of pollution sensitive taxa. These indicators were significantly (p  0.05) correlated with the salinity range, the level of chemical contaminants in sediments, and amount of impervious surface in the watershed.



### Introduction
Estuaries of the southeastern United States have 1.5–3.0 m tidal ranges, low relief, shallow depth, and expansive intertidal habitats (Nummedal et al. 1977; Wiegert and Freeman 1990). Spartina alterniflora and Juncus roemerianus salt marshes and the associated system of tidal creeks are characteristicfeatures of these environments (Teal 1962; Hackney et al. 1976; Wiegert and Freeman 1990). These creeks provide nursery habitats for many species of juvenile fish and crustaceans as well as feeding grounds for wading birds and adult fish (Shenker and Dean 1979; Weinstein et al. 1980; Wenner 1992; Wenner and Beatty 1993; Dodd and Murphy 1996). Hydrodynamic processes in tidal creeks also trap fine-grained sediments, organic material, and

* Corresponding author: tele: 804/684-7371; fax: 804/684- 7399; e-mail: lerbergs@vims.edu. 

### chemical contaminants (Biggs et al. 1989) andserve as both conduits and repositories for pollutants (Olsen et al. 1982; Horlick and Subrahmanyam 1983; Sanger et al. 1999a,b). Over the next several decades, the watersheds that drain tidal creeks in the southeastern UnitedStates, as well as globally, are projected to experience a high rate of human development (Edwards 1989; Culliton et al. 1990; Cohen et al. 1997). Theconstruction of highway systems, residential housing, and industrial facilities that are projected toaccompany this development will alter the topography and drainage patterns. These alterations will increase the rate and volume of freshwater inflow as well as the amount of fine sediments, toxicchemicals, organic materials, and nutrients introduced into estuaries (Driver and Troutman 1989; Vernberg et al. 1992; Fulton et al. 1993; Holland et al. 1996; Kucklick et al. 1997). Biological deg-Watershed Development in Tidal Creeks 

### 839

Fig. 1. Map of the Charleston Harbor Estuary showing the locations of the tidal creeks sampled (mouth at approximately 32  45  N 79  53  W). Circles indicate reference creeks. Diamonds indicate developed creeks.

### radation associated with human-induced alterations to the ecosystem has been reported in many freshwater river and stream environments (Karr 1991; Schueler 1994). If development proceeds inan uncontrolled manner, the productivity and processes of tidal creek ecosystems may be irreversibly degraded (Vernberg et al. 1992; Sanger et al. 1999a,b).

This study was part of a larger project (TidalCreek Project) evaluating the linkages between tidal creek environmental quality and human uses of coastal watersheds (Holland et al. 1996). The TidalCreek Project used a comparative watershed approach that contrasted the physical, chemical, and ecological characteristics of tidal creeks draining relatively undeveloped watersheds with creeksdraining urban, suburban, and industrial watersheds. Study elements included water quality, sediment quality, macrobenthic communities, and nekton communities. The specific objectives of this study were to evaluate the impacts of watershed development on macrobenthic communities and evaluate linkages with environmental parameters likely to affect them.

Materials and Methods

STUDY 

### A REA AND 

### SAMPLING 

### D ESIGN 

### Twenty-three tidal creeks located in Charleston Harbor were sampled from July 5 to September 10, 1994 (Fig. 1). Eleven creeks were dominated byurban, suburban, and/or industrial land cover (developed creeks), and eight drained undeveloped forested watersheds (reference creeks). Fourcreeks that drained predominately salt marsh vegetation were also sampled. Creeks were classified into two subpopulations for analysis: upland and salt marsh. Upland creeks were further classified into four land use categories: forested or reference (i.e.,  15% of the watershed as urban/suburban land cover and some freshwater inflow); suburban ( 45% urban/suburban land cover with a human population density 5 but  20 individuals per hectare); urban (i.e., 70% urban/suburban land cover with a human population density of 20 individuals per hectare); and industrial (i.e., 45% urban/suburban land cover and presence of industrial facilities). Salt marsh creeks were eitherlocated in regions of the Charleston Harbor Estuary far removed from any source of pollution (reference) or were located adjacent to highly developed (impacted) watersheds.

All creeks had a water depth of  10 cm at low tide, and were 2–3 m deep at high tide. The upper creek boundary was the point where depth atmean high tide was about 1 m, or where an impassable obstacle (a dike or security fence) was reached. The lower boundary was the point where the creek converged with another water body, or the depth in the channel exceeded 3 m at high tide. The creeks represented the range of salinity distributions, sediment characteristics, creeklengths (231 to 1491 m), watershed sizes, land cover types, and levels of human disturbance that occur in Charleston Harbor (Table 1). Creeks were stratified into 300-m reaches and macrobenthic community samples were collected randomly within each reach at approximately 1 m below the mean high tide line (mid-tide level). Six samples were collected with a 45.6-cm 2 

### coring device to a depth of 15 cm and sieved through a 500-

 m screen. All organisms retained on the screen were identified to the lowest possible taxonomic

### 840 S. B. Lerberg et al.

TABLE 1. Summary of land use and watershed condition indicators for upland and salt marsh creeks.

Watershed Type Creek Name, Code Linear Measurements

Watershed Size (ha) Creek Length

(m) Land Use Category

Forest (ha) Salt Marsh (ha) Water (ha) Barren/ Disturbed

(ha) Agriculture (ha) Urban/ Suburban

(ha) Watershed Condition Indicators

Population Density (# ha

 1 ) Impervious Surface

(%) Upland Creeks

Forested Forested Forested Forested Forested Forested Forested Forested Industrial Beresford Creek, BF Deep Creek, DP Foster Creek, FT Horlbeck Creek, HB Lachicotte Creek, LH Lighthouse Creek, LC Long Creek, LI Rathall Creek, RT Diesel Creek, DL 25.1 64.7 16.0 237.5

13.1 37.3 412.4

72.1 105.3 535 586 585 895 436 899 1,446 1,200

784 5.2 40.0

3.4 184.6

1.9 2.7 243.1

30.3

0.0 19.9 12.0 12.6 9.1 11.2 31.6 17.7 35.3 32.8 0.0 0.0 0.0 3.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17.9 0.0 3.0 43.8

6.5 8.9 0.0 12.7 0.0 22.3

0.0 0.0 101.8

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 0.0 63.6 0.0 0.0 0.0 0.1 0.0 0.0 0.3 0.6 6.9 0.0 4.1 0.0 1.8 0.0 0.0 2.2 0.8 50.0 Industrial Industrial Urban Urban Suburban Suburban Suburban Suburban Suburban Suburban Koppers Creek, KP Shipyard Creek, SH New Market Creek, NM Vardell Creek, VR Bull Creek, BL Cross Creek, CC Metcalf’s Creek, MC Parrot Creek, PC Shem Creek, SM Yacht Club Creek, YC 116.6 279.1 187.2 68.7 442.8 312.9 129.7 147.2 427.8

69.1 880 826 1,167

450 1,395

536 874 1,491 1,174

593 0.0 14.1 3.0 0.0 83.5 28.6 17.4 23.6 61.5

4.6 11.6 10.2 26.6

9.5 20.5

5.2 7.0 14.5 9.3 8.2 0.0 0.0 0.0 0.0 15.6 2.4 0.0 1.4 4.2 1.0 12.3 74.5 17.9 0.0 3.5 41.0 17.1 30.6 66.8

1.8 0.0 0.0 0.0 0.0 0.0 8.9 0.0 7.8 0.0 0.0 92.7 180.4 139.7 90.5 319.7 226.8

88.2 69.3 286.0

53.5 3.3 8.2 21.1 31.8 12.7 10.6 8.9 7.0 15.7 7.1 52.7 49.4 51.2 70.4 28.9 26.4 30.8 19.5 34.5 14.9

Salt Marsh Creeks

Reference Reference Impacted Impacted Battery Simpkin Creek, BS Grice Cove Creek, GC Dill Creek, PI Orange Grove Creek, OG 23.0 20.6 20.2 20.6 1,110 577 536 285 0.0 0.1 0.0 0.1 23.0 20.5 20.0 20.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0



### level and counted. Six surface (upper 2 cm) sediment samples were also collected and processed to determine percent moisture, percent silts and clays, and percent sand using the standard pipette protocol modified from Plumb (1981).

A Hydrolab DataSonde 3 (DS3) water quality monitoring system was deployed in the lower reach of each creek for 2 to 4 d prior to sampling. The DS3 was positioned approximately 5–10 cm abovethe creek bottom and measured salinity, water temperature, dissolved oxygen concentration, pH, and water depth at 30-min intervals.Surface sediments (upper 2 cm) were also collected during the summer of 1995 for chemicalanalyses at one randomly selected site from the upper-most and lower-most reach of each creek sampled in 1994. These samples were homogenized then divided into three aliquots. One aliquot was placed in an acid washed plastic jar for trace metalanalyses. The second aliquot was placed in a precleaned glass jar for organic contaminant analyses. The third aliquot was stored in a plastic bag for organic carbon analyses. The samples were then immediately placed on ice and stored at

 60  C. Analyses were performed for 14 trace metals, 24polyaromatic hydrocarbons (PAHs), and 20 polychlorinated biphenyls (PCBs) by the National Ocean Service Laboratory (National Oceanic and Atmospheric Administration [NOAA]-Charleston,South Carolina) using methods described by Sanger et al. (1999a,b). The contaminants measuredduring the study include the majority of the contaminants routinely monitored by NOAA’s National Status and Trends Program (1991).The boundary of each watershed was defined using topographic maps and Geographical Information System (GIS). The area was classified into landuse categories based on a modification of the Anderson Land Use Classification System (Anderson et al. 1976). Human population statistics for eachwatershed were obtained from the BerkeleyCharleston-Dorchester Council of Governments(TIGER/Line Files 1992). The percent of each watershed that was impervious surface was determined by point sampling a minimum of 200 randomly selected points within each watershed on 1: 4,800 blackline aerial photographs (photographed in 1989) and counting the number of points thatfell on roads, parking lots, roofs, or other impervious surfaces.

STATISTICAL 

### A NALYSES 

### Abundance data for the numerically dominanttaxa was evaluated as the estimated number of individuals m

 2 

### (absolute abundance) or as the percent of the total infauna (relative abundance) col-Watershed Development in Tidal Creeks 

### 841



### lected. Only the relative abundance data are presented in this paper. The absolute abundance data can be found in Lerberg (1997).

A two-way analysis of covariance (ANCOVA) using SAS (1989) with all significant interactionterms was used to contrast macrobenthic community characteristics among land use classes and between the upper-most and lower-most reaches of creeks. Community measures used included the number of species per sample, Shannon-Weiner Diversity Index (H’), total number of individuals per sample, percent dominance by most abundantspecies, and the relative abundance of the numerically dominant oligochaetes ( Monopylephorus rubroniveus, Tubificoides brownae, and Tubificoides heterochaetus), polychaetes ( Laeonereis culveri and Streblospio benedicti), and nemerteans. Covariates evaluatedincluded the mean creek salinity, the silt-clay content of the sediments, and the percent of the time the dissolved oxygen concentration was hypoxic (  28% saturation). Covariates were included in the model if they were significant at p  0.10. Abundance data were transformed using a log 10 

### transformation. Proportional data were transformed using an arcsine square root transformation. Estimates of least square means and pair-wise comparisons were obtained for each ANCOVA model. Theassumption that there were no significant differences in the slopes of the treatment lines was tested by determining if the covariate by main treatment effects interaction term was significant. Theequal slopes model is presented. All statistical analyses were considered significant at p  0.10. This probability level (p  0.10) was selected over a more standard p  0.05 to reduce the probability of making a Type II error. We compared our results using both a 0.05 and 0.10 probability level and found relatively few differences. Use of the p

 0.10 therefore provided for an increased likelihood of identifying potential ecologically important problems. In all cases we have provided theobserved p values and as much detail on the statistical testing as possible.

Wilcoxon rank sum and independent sample t

tests were also used to compare the physical-chemical data between reference and developed creeks.Associations (strength and direction) between environmental variables and macrobenthic community characteristics were evaluated using a Pearson’s product moment correlation coefficient (SAS 1989).

A mean effects range-low quotient (ERLQ) was developed to provide a cumulative measure of trace metal, PAH, and PCB contamination in thesediments of these tidal creeks. This calculation involved dividing each concentration by the ERL value published in Long et al. (1995), summing the ratio values, and dividing by the number of individual compounds included in the calculation (n

 23) (Long et al. 1998). The specific procedures used and analytes included in the calculations are described in Sanger (1998).

Results

L

AND 

### U SE AND 

### H UMAN 

### P OPULATION 

### DATA

### Watershed size in the population of creeks sampled ranged from 13.1 to 442.8 hectares (ha). The drainage areas of developed upland creeks (mean

 203.4 ha) were generally larger than the drainage areas of the reference upland creeks (mean  109.8 ha). The larger drainage basins had the most complex land cover patterns. The four salt marsh creeks had the smallest drainage areas (range  20.2 to 23.0 ha, mean area  21.1 ha), and consisted of primarily one land cover type—estuarine salt marsh. Population density in developed upland watersheds ranged from 0 to 31.8 individuals ha

 1

### (Table 1). The human population density in forested watersheds never exceeded 0.6 individuals ha

 1 

### . Creeks located in forested watersheds had little or no impervious surface in their drainage basins. Creeks in suburban and urban/industrial watersheds had 15–79% of their drainage area as impervious surface (Table 1). The amount of impervious surface in upland watersheds was significantly correlated (p  0.0001, r 2 

###  0.62) with human population density. When industrial watersheds were excluded from this analysis the r2 

### value increased to 0.98.

P HYSICAL AND 

### C HEMICAL 

### DATA 

### Salinity varied within creeks, among creeks, and among watershed classes (Fig. 2). Reference and developed creeks encompassed a broad range ofsalinities including euhaline (25–32 psu), polyhaline (18–25 psu), and mesohaline (5–18 psu) environments. Upstream-downstream salinity gradients (range  0–11.7 psu, mean  1.75 psu) weresmall because most of the volume of creeks (ranging in length from 231 to 1,491 m) was displaced on each tidal cycle. The mean salinity of upland creeks was about five psu lower during low tidethan the comparable high tide salinity. Rainfall occurred shortly before or during almost every sampling event, with a measurable rain event occurring on 36 d of the 68-d sampling period. The average rainfall event resulted in 1.79 cm of rain. During rain events (e.g., thunderstorms) large,rapid declines in the low tide creek salinity occurred, even for the salt marsh creeks. Salinity fluctuations, as represented by the salinity range, were significantly greater (p  0.01) in the suburban and urban/industrial creeks than in the reference (forested) upland creeks (Fig. 2). The salinity

### 842 S. B. Lerberg et al.

Fig. 2. The mean, median, and salinity range for each creek collected two to four days prior to each sampling event. The top of the bar represents the mean value and the shaded square represents the median value. The vertical line represents the range. The mean salinity range (mean SR

w SE) for each watershed class is as follows: Forested (6.9 psu 1.2), Industrial (12.8 psu 2.9), Urban (14.5 psu 1.4), Suburban (14.0 psu 3.2), Reference Salt Marsh (14.6 psu 5.5), and Impacted Salt Marsh (6.9 psu 1.9).



### range of upland creeks was positively correlated (p

 0.05) with the size of the drainage basin.

Dissolved oxygen (DO) values varied with time of the day and tidal stage. In general, highest DO levels (% saturation) occurred in mid-afternoon.The lowest DO levels occurred during early morning low tides (Fig. 3). Mean DO levels were similaramong watershed classes (Fig. 4). Values representing supersaturated conditions occurred during midday in upland and salt marsh creeks. Dissolved oxygen levels in both reference and developedcreeks were frequently below 28% saturation (hypoxic). The percent of time upland creeks exhibited low DO levels was similar among watershed classes (Fig. 5, p 0.10).

Mean creek water temperatures were 25  C. Extreme values occurred during daytime low tides ( 32  C). No significant differences in water temperature occurred among creeks. The pH of creekwater tended to be lower in forested (upland reference) creeks (7.1 versus 7.3) probably becauseof the higher levels of humic acids which are associated with runoff from forested environments. Sediments varied in a heterogeneous manneralong the lengths of creeks. Few consistent upstream-downstream gradients in the silt-clay content were found. Exceptions included the downstream increase in silt-clay content in Shem, Metcalf, and Diesel creeks. Silt-clay content in Parrot and Shipyard creeks exhibited the reverse pattern. Greater amounts of fine sediments were found in impacted salt marsh creeks than reference salt marsh creeks. Forested creeks were characterized by more fine sediment than suburban, industrial, or urban creeks. The urban creek class contained the greatest amount of sand sediments. Surface sediments in creeks draining industrial and urban watersheds contained significantly (p  0.0001) greater amounts of chemical contaminantsthan other creek classes particularly in their uppermost reaches (Fig. 6). A complete summary and analysis of the contaminant data is presented in Sanger et al. (1999a,b).

MACROBENTHIC 

### C OMMUNITY 

### DATA 

### A total of 8,034 individuals representing 97 taxawere obtained from the 417 samples. The assemblage was dominated by annelid worms, particularly oligochaetes (mean  2,208 individuals m

 2 

### ) and polychaetes (1,811 individuals m

 2 

### ). These taxa comprised 95.9% of the fauna. Molluscs (71 individuals m

 2 

### ) and crustaceans (45 individuals

m  2 

### ) accounted for only 2.8% of the fauna (Tables 2 and 3). Forty-four of the 97 taxa collected occurred in only one or two samples. Nine taxa ( M. rubroniveus,S. benedicti, Heteromastus filiformis, L. culveri, T. heterochaetus, T. brownae, Capitella capitata, Tharyx cf. acutus, and Neanthes succinea) accounted for 90% of the specimens collected (Table 3).Watershed Development in Tidal Creeks 

### 843

Fig. 3. Summary of dissolved oxygen and depth data for a representative (a) forested creek (Long Creek sampled July 24– July 28, 1994), (b) suburban creek (Shem Creek sampled July 18–July 21, 1994), (c) industrial creek (Diesel Creek sampled July 16–July 20, 1994), and (d) salt marsh impacted creek (Dill Creek sampled July 22–July 25, 1994). Fig. 5. The mean percent of time dissolved oxygen concentrations were less than 28% for creeks composing each watershed class. Error bars represent SE.

Fig. 4. The mean, median, and range of dissolved oxygen data for each creek two to four days prior to each sampling event. The top of the bar represents the mean value and the shaded square represents the median value. The vertical line represents the range. 

### MACROBENTHIC 

### C OMMUNITY 

### R ESPONSE TO 

### NATURAL 

### E NVIRONMENTAL 

### V ARIATION

### Few taxa exhibited abundance differences between the upper-most and lower-most creek reaches. The relative abundances of the oligochaete M. rubroniveus (p  0.0079), and the polychaete C. capitata (p  0.0403) were significantly higher in the upper-most creek reaches than the lower-mostreaches. Conversely, the abundance of the polychaete H. filiformis was significantly higher (p 0.0001) in the lower-most reaches. When upstream-downstream gradients in abundance were

### 844 S. B. Lerberg et al.

Fig. 6. Summary of the ERLQ (effects range-low quotient) values for the upper and lower reach of each watershed type. Error bars represent SE. TABLE 2. Summary of the macrobenthic data for upland and salt marsh creeks by major taxonomic group (n  417 cores).

Major Taxa No. of Individuals Collected Average Density (# m

 2 ) % Total Abundance Oligochaeta Polychaeta Gastropoda Nemertinea Crustacea—Others* Crustacea—Decapoda Platyhelminthes Pelecypoda Hirudinea Hemichordata Hydrozoa Sipuncula 4,198 3,443

132 130 61 24 20 19 4 1 1 1 2,208 1,811 69 68 32 13 11 10 2 1 1 1 52.25 42.85

1.64 1.62 0.76 0.30 0.25 0.24 0.05 0.01 0.01 0.01* This group includes Amphipods, Isopods, Tanaids, Ostracods, and Mysids.



### found, the actual amount of variation accounted for by longitudinal distance was relatively small (  5% of the total variation). The salinity covariate was significant (p  0.10) for 9 of the 14 metrics evaluated (Table 4) and was the most significant term in the ANCOVA model for five of these analyses accounting for at least10% of the model variance. Metrics that were positively associated with salinity included the number of taxa, the total number of individuals, and the relative abundance of all polychaetes, H. filiformis, and S. benedicti. The relative abundance of all oligochaetes, T. heterochaetus, L. culveri, and the nemerteans decreased with increasing salinity. The silt-clay covariate was significant for 7 of the 14 metrics evaluated (Table 4) and was the most significant term in the ANCOVA model for three metrics. However, the silt-clay covariate generally accounted for  2% of the variance in the ANCOVA models. The relative abundance of the polychaete L. culveri was the only metric evaluated that had substantial amounts of variance ( 14%) associated with the sediment covariate. Metrics thatwere negatively correlated with the sediment siltclay content included the number of taxa per sample, the relative abundance of all polychaetes, and the relative abundance of L. culveri, C. capitata, and T. heterochaetus. The total number of individuals per sample and the relative abundance of M. rubroniveus were positively correlated with silt-clay content. The dissolved oxygen covariate was significant for 6 of the 14 metrics evaluated (Table 4) and was the most significant term in the ANCOVA model for three metrics. However, it accounted for small(2–5%) amounts of the variance. Metrics that decreased in value with decreasing dissolved oxygen levels were the number of taxa per sample, and the relative abundance of the polychaetes, S. benedicti and L. culveri. Metrics that increased in value with increasing exposure to low dissolved oxygen werethe total number of individuals, the relative abundance of all oligochaetes, and the relative abundance of M. rubroniveus.

MACROBENTHIC 

### C OMMUNITY 

### R ESPONSES TO 

### D EVELOPMENT

### Tests comparing macrobenthic community metrics among watershed-types and reaches, and the identification of interactions between watershed and reach effects are presented in Table 5. Resultsfor the upland creek classes are discussed first followed by a discussion of salt marsh creeks. Data for industrial and urban creek classes were combined for these analyses because of the similarity in theamounts of impervious surface for the two watershed classes. This combination also increases thepower of significance tests to detect differences between this new urban/industrial watershed class and other creek classes. The number of taxa per sample was significantly higher in creeks located in the forested (p  0.0566) and suburban (p  0.0199) watershed classes than in creeks draining urban/industrial watersheds. This pattern resulted because crustaceansand bivalves were reduced in creeks draining urban and industrial watersheds. Rare taxa that werenot found in the industrial and urban creeks included T. cf. acutus, Fabricia sp., Potamilla sp., Leptochelia sp., Melita nitida, Gammarus mucronatus, Cyathura burbancki, Macoma tenta, Tellinidae, and Polymesoda caroliniana

.

The total number of individuals per sample washigher in upland creeks draining suburban watersheds than in creeks draining watersheds dominated by forested (p  0.0032) or urban/industrial (pWatershed Development in Tidal Creeks 

### 845

TABLE 3. Macrobenthic data collected from the upper-most and lower-most reaches of upland creeks and salt marsh creeks. Key to Major Taxonomic Groups: A  Amphipoda, G  Gastropoda, HE  Hemichordata, I  Isopoda, M  Mysidacea, N  Nemertinea, O  Oligochaeta, OS  Ostracoda, P  Polychaeta, PE  Pelycepoda, PLAT  Platyhelminthes, S  Sipuncula, T  Tanaidacea. Key to Species Code: PI  Pollution Indicative, PS  Pollution Sensitive, U  Ubiquitous, R  Rare.

Scientific Name Species Code Forested (n  93)

Avg. No.

m  2 % Total Suburban (n  71)

Avg. No.

m  2 % Total Urban/Industrial (n  56)

Avg. No.

m  2 % Total Marsh Ref. (n  24)

Avg. No.

m  2 % Total Marsh Imp. (n  17)

Avg. No.

m  2 % Total Monopylephorus rubroniveus (O) PI 787.6 22.6 1,868.7 44.2 806.7 36.1 1,928.0 28.6 7,198.2 84.8 Tubificoides heterochaetus (O) PS 573.0 16.4 262.5 6.2 50.9 2.3 Heteromastus filiformis (P) PS 474.0 13.6 139.0 3.3 82.2 3.7 849.8 12.6 270.9 3.2 Streblospio benedicti (P) PS 466.9 13.4 444.8 10.5 246.7 11.0 2,412.3 35.7 528.9 6.2 Capitella capitata (P) U 285.3 8.2 40.2 0.9 231.0 10.3 18.3 0.3 Neanthes succinea (P) U 207.5 6.0 139.0 3.3 78.3 3.5 173.6 2.6 38.7 0.5 Laeonereis culveri (P) PI 113.2 3.2 417.0 9.9 513.0 22.9 Nemertinea (N) PS 108.5 3.1 40.2 0.9 70.5 3.2 64.0 0.9 64.5 0.8 Tubificidae (O) U 84.9 2.4 83.4 2.0 39.2 1.8 100.5 1.5 90.3 1.1 Tubificoides brownae (O) PI 82.5 2.4 525.1 12.4 82.2 3.7 721.9 10.7 270.9 3.2 Tharyx cf. Acutus (P) PS 63.7 1.8 30.9 0.7 246.7 3.7 Fabricia sp. A (P) R 49.5 1.4 Potamilla sp. (P) R 42.4 1.2 91.4 1.4 Tubificoides wasselli (O) R 25.9 0.7 3.1 0.1 Leitoscoloplos fragilis (P) R 21.2 0.6 27.8 0.7 3.9 0.2 27.4 0.4 12.9 0.2 Monopylephorus irroratus (O) R 16.5 0.5 37.1 0.9 9.1 0.1 Polydora cornuta (P) R 14.1 0.4 18.5 0.4 27.4 0.4 Leptochelia sp. (T) R 11.8 0.3 Ostracoda sp. (OS) R 11.8 0.3 6.2 0.1 Eteone heteropoda (P) R 7.1 0.2 9.1 0.1 Mediomastus californiensis (P) R 7.1 0.2 3.9 0.2 Cassidinidea lunifrons (I) R 4.7 0.1 18.5 0.4 3.9 0.2 Melita nitida (A) R 4.7 0.1 9.3 0.2 Amphitrite ornata (P) R 2.4 0.1 Corbicula contracta (PE) R 2.4 0.1 Cyathura burbancki (I) R 2.4 0.1 6.2 0.1 9.1 0.1 Glycera americana (P) R 2.4 0.1 3.1 0.1 Hesionidae (P) R 2.4 0.1 3.1 0.1 3.9 0.2 Macoma tenta (PE) R 2.4 0.1 6.2 0.1 Sipuncula (S) R 2.4 0.1 Tellinidae (PE) R 2.4 0.1 Websterinereis sp. (P) R 2.4 0.1 Turbellaria (PLAT) R 18.5 0.4 3.9 0.2 Bocardiella sp. A. (P) R 15.4 0.4 Mysidopsis bigelowi (M) R 12.4 0.3 Gastropoda (G) R 9.3 0.2 Monticellina dorsobranchialis (P) R 9.3 0.2 18.3 0.3 Paraprionospio pinnata (P) R 9.3 0.2 Polydora socialis (P) R 6.2 0.1 Gammarus mucronatus (A) R 3.1 0.1 Hemichordata (HE) R 3.1 0.1 Lumbrineridae (P) R 3.1 0.1 Mysidopsis furca (M) R 3.1 0.1 Polymesoda caroliniana (PE) R 3.1 0.1 Prionospio sp. (P) R 3.1 0.1 Sphaeorsyllis longicauda (P) R 3.1 0.1 9.1 0.1 Corbiculidae (PE) R 3.9 0.2 Sabellidae (P) R 3.9 0.2 9.1 0.1 Terebellidae (P) R 3.9 0.2 Corophium lacustre (A) R 9.1 0.1 Gemma gemma (PE) R 9.1 0.1 Mulinia lateralis (PE) R 9.1 0.1 Acanthohaustorius intermedius (A) R 12.9 0.2



###  0.0002) land cover (Table 5). Most of the higherabundances found in suburban creeks were associated with the oligochaete fauna. The percent ofthe macrobenthic assemblage represented by oligochaetes and the relative abundance of the two most abundant oligochaete species, M. rubroniveus and T. brownae, were significantly higher in the suburban creek class than in the forested or urban/

### 846 S. B. Lerberg et al.

TABLE 4. Summary of the influence of environmental factors used as covariates in the ANCOVA models on community characteristics. A plus indicates a positive relationship between the covariate and the respective community characteristic. A minus sign indicates a negative relationship.

Habitat/Exposure Indicators Salinity (mean from DS3) Sediment Type (% silts and clays) Dissolved Oxygen (% time below 28% saturation) Community Parameters

Species Richness (# sample

 1 )  Shannon-Weiner Diversity (H  ) Total Number of Individuals (# sample

 1 ) Dominance by Most Abundant Species (% abundance

sample

 1 )

Dominant Taxa

Polychaetes 

Heteromastus filiformis Streblospio benedicti  Laeonereis culveri Capitella capitata  

 

Oligochaetes 

Monopylephorus rubroniveus Tubificoides brownae Tubificoides heterochaetus

  Nemertinea



TABLE 5. Summary of ANCOVA results evaluating the effects of watershed type and longitudinal position (reach) on community parameters. Values shown are p levels. Pairwise comparisons were analyzed using least square means. Treatments not connected by a common underline differed at p  0.10. SR  salt marsh reference, SI  salt marsh impacted, U  urban/industrial, SU  suburban, and F  forested (upland reference), ns  not significant. An asterisk indicates that the models for these species were accomplished using data for only creeks located on upland watersheds.

Macrobenthic Community Parameters Significant Covariates Watershed Type Reach Interaction Pairwise Comparisons Number of taxa (# sample

 1 ) DO, sal, mud 0.0084 ns ns SR SU F SI U SR SU F SI U Total number of individuals (# sample

 1 ) 0.0001 ns 0.0439 SI SR SU F U Shannon-Weiner Diversity (H  ) DO, sal, mud 0.0082 ns ns SR F SU U SI SR F SU U SI Dominance by most abundant species (% abundance sample

 1 ) 0.0145 ns 0.0433 SI SU U SR F SI SU U SR F Oligochaetes (% abundance sample

 1 ) DO, sal 0.0002 ns ns SI SU SR U F SI SU SR U F Monopylephorus rubroniveus mud, DO 0.0001 0.0079 ns SI SU SR U F SI SU SR U F Tubificoides brownae 0.0001 ns ns SR SU SI U F Tubificoides heterochaetus * sal, mud 0.0001 ns ns F SU U Polychaetes (% abundance sample

 1 ) sal, mud ns ns ns SR SU F U SI U F U SI Streblospio benedicti sal, DO 0.0609 ns ns SR F SI U SU SR F SI U SU

Laeonereis culveri * mud, DO, sal ns ns 0.0004 U SU F

Nemertinea (% abun sample

 1 ) sal 0.0047 ns ns F SR U SI SU F SR U SI SU 

### industrial classes (Table 5). Abundances of M. rubroniveus and T. brownae were lowest in creeks draining forested watersheds. The relative abundance of the polychaete L. culveri was significantly higher (p  0.0592) in creeks draining urban/industrial watersheds than increeks draining forested watersheds. The abundance of this species in creeks draining suburban watersheds was intermediate and not significantly different (p 0.10) from that in creeks draining urban/industrial or forested watersheds. Several other taxa had abundance patterns thatappeared to be negatively associated with increasing degrees of watershed development. For example, the relative abundances of T. heterochaetus (p

 0.0001), S. benedicti (p  0.0416), and the nemerteans (p  0.0271) were significantly higher in the forested creek class than in the suburban and urban/industrial creek classes (Table 5). Engle and Summers (1998) and Van Dolah et al. (1999) suggest that the H  measure of species diversity is positively correlated with estuarine envi-Watershed Development in Tidal Creeks 

### 847

TABLE 6. Summary of the responses of the macrobenthic community to watershed development. Values presented for mean number of taxa per sample, Shannon-Weiner diversity (H  ), % dominance by most abundant species, % relative abundance of rare taxa, % relative abundance of pollution indicative species, % relative abundance of potentially pollution sensitive taxa, % relative abundance of ubiquitous taxa, and mean total number of individuals per sample.

Macrobenthic Community Measures Upland Creeks

Forested Suburban Urban/Industrial Salt Marsh Creeks

Reference Impacted Number of taxa per sample 3.4 3.6 2.5 4.9 2.8 Shannon-Weiner Diversity (log10) 0.37 0.36 0.30 0.48 0.21 % dominance 48 58 52 48 80 % abundance of rare species 5.8 4.6 0.7 1.6 0.1 % pollution indicative species 27.3 64.8 60.5 38.7 84.3

Monopylephorus rubroniveus 21.9 43.1 34.8 28.2 81.2 Laeonereis culveri 3.1 9.6 22.1 0.0 0.0 Tubificoides brownae 2.3 12.1 3.5 10.5 3.1 % pollution-sensitive species 46.8 21.2 19.4 52.2 9.8

Tubificoides heterochaetus 15.9 6.1 2.2 0.0 0.0 Streblospio benedicti 13.0 10.3 10.6 35.2 6.0 Nemertinea 3.0 0.9 3.0 0.9 0.7 Heteromastus filiformis 13.2 3.2 3.5 12.4 3.1 Tharyx cf. acutus 1.8 0.7 0.0 3.6 0.0 % ubiquitous taxa 13.7 4.1 13.3 2.8 0.4

Capitella capitata 7.9 0.9 10.0 0.3 0.0 Neanthes succinea 5.8 3.2 3.4 2.5 0.4 Total number of individuals 3,348 4,294 2,562 6,402 8,423



### ronmental quality at the regional scale. This study found that H  was not significantly different among upland creek classes (Table 5). Diversity (H  ) values did tend to decrease as the degree of development increased. The dominance measure evaluated (relative abundance of the most abundant species) was significantly higher (p  0.0381) insuburban creeks than in forested creeks. Dominance values for urban/industrial creeks were intermediate between the values for suburban and forested creeks, but were not significantly different (p 0.10) from either class of creek (Table 5).

The salt marsh reference creeks had significantly higher numbers of taxa (p  0.0924) and diversity (p  0.0009) than the impacted salt marsh creeks. Much of this difference was due to the absence of rare taxa, particularly crustaceans and bivalves, from impacted salt marsh creeks. Rare taxa thatwere not found in impacted salt marsh creeks included T. cf. acutus, Eteone heteropoda, C. burbancki, Corophium lacustre, Mulinia lateralis, and Gemma gemma. In addition, the impacted salt marsh creeks had significantly higher dominance values than the other watershed classes sampled (p  0.0555). Macrofaunal abundance was consistently higherfor salt marsh creeks than for upland creeks, although there was no difference in total macrofaunal abundance between the two salt marsh creek populations. The oligochaete M. rubroniveus was the numerically dominant macrobenthic organism in salt marsh creeks. Densities of this species were significantly higher (p  0.0001) in impacted salt marshcreeks than in reference salt marsh creeks. The oligochaete, T. brownae, exhibited the opposite pattern and had significantly (p  0.0556) higher abundances in reference salt marsh creeks than in impacted salt marsh creeks. Two species, L. culveri and T. heterochaetus, that were numerically dominant in upland creeks were not found in salt marsh creeks. Both of these species appear to prefer sand habitats and the high levels of fine sediments that occur in the salt marsh creeks may have effectively excluded them from these environments.

A summary of the changes in relative abundanceof numerically dominant species and communitylevel metrics among watershed classes is presented in Table 6. The relative abundance of three of the numerically dominant species ( M. rubroniveus, T. brownae, and L. culveri) increased with increasing levels of watershed development and pollution stress. The two oligochaete species, M. rubroniveus and T. brownae, attained their highest abundancein the suburban creeks (Table 6). The high abundance of L. culveri in urban/industrial creeks may have resulted from the higher proportion of sand sediments in this class of creeks (e.g., Vardell and Shipyard). The oligochaete T. heterochaetus, the nemerteans, and the polychaete S. benedicti declined in abundance with increasing levels of watershed development (Tables 5 and 6). Most research on ma-

### 848 S. B. Lerberg et al.

Fig. 7. Relationships between (a) human population density, (b) salinity range, and (c) total chemical exposure and the amount of impervious surface on the watershed. The coefficient of determination (r 2 ) and p-value are presented. Fig. 8. Relationships between two indices of macrobenthic community measures and the amount of impervious surface in the watershed. Only data from the upland creeks were used. Potentially pollution sensitive taxa (a) include Tubificoides heterochaetus, Streblospio benedicti, Heteromastus filiformis, Tharyx cf. acutus, and Nemertinea. Pollution indicative taxa (b) include Monopylephorus rubroniveus, Tubificoides brownae, and Laeonereis culveri. The coefficient of determination (r 2 ) and p-value are presented.



### crobenthic indicators suggest that S. benedicti is relatively tolerant to pollution and list this polychaete as a pollution indicative organism (Pearson and Rosenberg 1978; Levin 1984; Weisberg et al. 1990; Engle et al. 1994). However, our findings and the experiments of Sarda et al. (1996) suggest that S. benedicti is not as tolerant to chronic pollution exposure or hypoxia as the oligochaete M. rubroniveus.

Other species that are potentially useful as indicators of pollution stress include T. cf. acutus and H. filiformis. Tharyx cf. acutus decreased in abundance as the degree of watershed development increased, however, this species only occurred in high polyhaline and euhaline environments. Heteromastus filiformis had lower relative abundance in creeks located on developed watersheds (Table 6). These differences were not significant (p 0.10) because of high within-habitat variability in creeks with forested watersheds. Lower abundances ofthese species in developed creeks do not unambiguously indicate the degree of development stress. In contrast, N. succinea and C. capitata were ubiquitous organisms which showed little differences in abundance with the type and degree of watersheddevelopment and appear to be not useful as indicators of pollution stress (Table 6).The amount of impervious surface in a watershed has been found to be a good indicator of watershed condition by a number of studies (Schueler 1994; Arnold and Gibbons 1996). In this study there was a significant relationship between the amount of impervious surface in the watershed sampled and the human population density, the salinity range as determined from the DS3 data, and the cumulative level of chemical contaminants in creek sediments as estimated by the ERLQ (Fig. 7). The slopes of all the lines were positive and significantly different from zero (p  0.025).Relationships between the amount of impervious surface in the watershed and two promisingmacrobenthic community-level metrics, the percent abundance of pollution indicative species ( L. culveri, M. rubroniveus, and T. brownae) and the percent abundance of potential pollution sensitive species ( T. heterochaetus, S. benedicti, Nemertinea, T. cf. acutus, and H. filiformis), are shown in Fig. 8.Watershed Development in Tidal Creeks 

### 849



### The relative abundance of potentially pollution sensitive taxa was negatively associated with the amount of impervious surface. The slope of the line was significantly different from zero (p 0.0027) with a marked decline in abundance occurring when the percent impervious surface exceeded 30%. The relative abundance of pollution indicative taxa increased with increasing amounts of impervious surface. The slope of this line was also significantly different from zero (p  0.0087).

DiscussionTidal creeks are the primary linkage between upland and estuarine environments. Tidal creeksfunction as repositories and conduits for sediments, organic materials, and chemical pollutants (Olsen et al. 1982; Sanger et al. 1999a,b). The highest levels of toxic chemicals were generally found in the upper reaches of industrial and urban creeks and were mainly associated with historicalindustrial point source discharges. Sediment contaminant concentrations in suburban creeks were not substantially different from values reported for forested creeks and did not attain levels likely to affect living organisms. Shem Creek was a notableexception in that it had elevated levels of both sediment trace metal and organic contaminants. This was not surprising since the Shem Creek watershed has a relatively high human population density ( 15 individuals ha

 1 

### ), receives runoff from commercial developments and a major highway corridor, and is used as a dockage facility for over 50 commercial fishing vessels and a dry stack boat storage yard (Sanger 1998; Sanger et al. 1999a,b). Suburban development produces few sources fortrace metal input and generally low levels of organic contaminant input to tidal creeks (Fortner et al. 1996; Sanger et al. 1999a,b).Sediments in salt marsh creeks were predominately fine grained pluff muds. Creek bottom habitats in upland creeks, particularly developed upland creeks, were frequently composed of large amounts of sand. Soils in the upland portion of the watersheds studied were predominately sandy. In addition, fine sediments may have been scouredfrom the creek channels due to altered hydrography and deposited on the marsh surface and/orin the deeper portions of the tidal creek and estuary.Tidal creek DO dynamics were complex. Concentrations in both upland (forested and developed) and salt marsh (reference and impacted) creeks were frequently hypoxic (  28% saturation)indicating exposure to low DO is a natural phenomenon in these systems. The observed DO levels were frequently within ranges reported to adversely affect macrobenthic distributions (Gaston 1985; Diaz and Rosenberg 1995). Impacted salt marsh creeks had the lowest and most variable DO levels. Dissolved oxygen dynamics in these creeks were similar to that reported for poorly flushed dead-end canals (Baca et al. 1988; Maxted et al. 1997). Developed creeks generally experienced more frequent exposure to low DO concentrations and had more pronounced tidal periodicity in DOthan reference creeks. For a more detailed description of the DO dynamics of the tidal creeks sampled refer to Wenner et al. (1999). The tidal creeks sampled tended to have lowerbiodiversity relative to comparable estuarine habitats (Engle et al. 1994; Weisberg et al. 1997). Inboth upland and salt marsh creeks, species richness, number of taxa per sample, and percentageof rare species decreased as watershed development and environmental impact increased. Thecreeks with the fewest species, particularly rare species, were also characterized by the most severeand prolonged exposure to the low dissolved oxygen levels, the highest levels of sediment contamination, and the largest salinity fluctuations. This finding is supported by a number of other studies (Pearson and Rosenberg 1978; Broom et al. 1991; Engle et al. 1994). Tidal creeks were numerically dominated by afew species of stress tolerant oligochaetes and polychaetes. Many of these species have life history characteristics which allow them to maintain high abundances in organically enriched environments that experience periodic hypoxia including rapidgrowth and development, multiple modes of reproduction including asexual reproduction, and the ability to recruit throughout much of the year (Grassle and Grassle 1974; McCall 1977; Pearson and Rosenberg 1978; Giere and Pfannkuche 1982; Levin 1984; Levin and Huggett 1990; LaSalle et al. 1991). Sarda et al. (1996) present evidence that long-term chronic exposure to organic enrichment and associated environmental conditions provide a competitive advantage to oligochaetes (e.g., Monopylephorus evertus), particularly during fall and winter when juvenile fish and crustacean predators are not abundant. These authors speculate that food resources and predation limit the abundances ofoligochaetes during summer and suggest opportunistic polychaetes (e.g., S. benedicti) may be better adapted to respond to disturbance from spring and summer predation. McCann and Levin (1989) further indicate that mobile subsurface deposit feeding oligochaetes (e.g., M. evertus ) inhibit growth of sedentary tubiculous polychaetes (e.g., S. benedicti) but not their recruitment. Additional information on the seasonal distribution of tidal creek macrobenthos and the effects of predation on recruitment patterns is needed. For example,

### 850 S. B. Lerberg et al.



### the data in Sarda et al. (1996) and Sanger (1998) suggest that winter sampling may provide a moresensitive measure of the effects of watershed development on macrobenthic communities. The ecological role of oligochaetes in estuarine systems is poorly understood (Diaz 1980; McCann and Levin 1989), although oligochaetes have high nutritional value and are a major food item in the diet of juvenile fish and crustaceans (Hunter and Arthur 1978; Van den Broek 1978; Giere and Pfannkuche 1982; Wiltse et al. 1984; McCann and Levin 1989). Many oligochaetes contain lipidswhich are critical for shrimp reproduction (Middleditch et al. 1979). The dominant oligochaete in South Carolina tidal creeks, M. rubroniveus, is ubiquitous in estuaries worldwide (Pfannkuche 1978)but little information is known about its environmental tolerances. A closely related Pacific species, Monopylephorus cuticulatus, is tolerant to anoxia, trace metal contamination, organic enrichment, and pulp mill effluents (Chapman et al. 1982). Our data suggest the same is true for M. rubroniveus. Additional research is needed to test this speculation.

Watersheds with urban and industrial development were associated with high levels of impervious surface ( 50%) and had severe impacts ontidal creek habitats including alterations to the hydrodynamic processes (as indicated by salinityrange), exposure to levels of chemical contaminants that cause mortality, altered growth, and reduced reproduction, and exposure to more frequent and severe hypoxia. The macrobenthic community in urbanized and industrialized creeks, especially the upper reaches, was characterized by low diversity, low numbers of rare and pollutionsensitive species, and low macrobenthic abundances (Table 6). The physical/chemical and the biological impacts reported by this study indicate a severe impact to the nursery functions of tidal creeks in urban/industrial watersheds.Suburban creeks had higher densities of pollution tolerant macrobenthic organisms, particularly the oligochaetes M. rubroniveus and T. brownae (Table 6). The levels of sediment contamination and hypoxia in these creeks were, however, generally not different than those in the forested upland creeks. The dominance in suburban creeks by a few species represents a trend towards a simplifiedfood web and may be an early warning of degradation (Diaz 1992). Simplification of food websmay cause irreversible changes in ecosystem processes (Fretwell 1987; Pimm and Kitching 1987).These findings suggest that macrobenthic responses in suburban creeks may be a more sensitive and reliable indicator of adverse effects than water or sediment quality data. The major physical alteration found for impacted salt marsh creeks was hypoxia. Elevated levels of sediment contaminants were not found in thesecreeks. Impacted salt marsh creeks were characterized by a high abundance of M. rubroniveus, a low abundance of S. benedicti and H. filiformis, and very low species diversity. Salinity fluctuations in tidal creeks appeared to have potential as a measure of the degree to which development had altered hydrodynamic processes including the rate and volume of non-point sourcefreshwater runoff. This metric was significantly correlated (p  0.005) with both of the promising community-level indicators identified. Changes in stream flow regime, resulting from modifications of the land surface with changing land use, is one of the primary environmental factors affecting the biological integrity of aquatic biota in freshwaterstream environments (Karr and Dudley 1981). Additional research in estuarine systems is needed to evaluate the effects of storm events, watershed size, and tidal creek type on this potential indicator of development impacts. Research is also needed todetermine how much of the variation in macrobenthic response, especially in suburban creeks, is due to alterations to salinity distributions. If the salinity range indicator were proven to be reliable,high quality salinity data could be collected routinely and economically with any number of available remote water quality monitoring systems. In freshwater stream environments, numerous studies (Miller and Mattraw 1982; Brown 1988; Schueler 1994; Arnold and Gibbons 1996) suggestthe amount of impervious surface is a good measure of the degree to which human development has altered watershed condition. In these studies, when the amount of impervious surface exceeded about 10%, the ecological condition of streams was impacted. When the amount of impervious surface exceeds about 30%, streams became permanentlydegraded (Arnold and Gibbons 1996). Our findings suggest a similar pattern occurs in the tidalcreeks. Clearly definable impacts to tidal creek water and sediment quality and macrobenthic communities did not occur until the percent impervious surface exceeded 30%. This is not surprising since South Carolina estuaries have relatively large tidal ranges ( 1 m) and large tidal mixing. The two promising community-level indicators developed by this study based on the data collected (i.e., the relative abundance of pollution indicativetaxa and the relative abundance of pollution sensitive taxa) were more sensitive indicators of ecological impact than other direct benthic metrics or measures of sediment and water quality. Otherbenthic metrics include the abundance of individual numerically dominant species and frequentlyWatershed Development in Tidal Creeks 

### 851



### used community-level metrics of condition (e.g., H  , McIntosh’s Dominance Index). Numerous studies have found community-level indicators or multi-metric indices (e.g., index of biotic integrity) developed from broad scale comprehensive data to be sensitive and reliable measures of ecological condition (e.g., Pearson and Rosenberg 1978; Karr 1981; Bilyard 1987; Warwick and Clark 1991; Diaz1992; Engle et al. 1994; Weisberg et al. 1997). Additional research is needed to validate these indicators at regional scales.

ACKNOWLEDGMENTS

We wish to thank C. Biernbaum, B. Roumillat, and C. Wenner for providing input into the design and analysis of this workand in the preparation of the manuscript. We also wish to recognize the efforts of George Riekerk, Lynn Zimmerman, Anita Black, Elizabeth Daniel, Jackie Thompson, and Bonnie Whitlockfor participating in fieldwork, sample processing, and data analysis. Funding for this research was provided by the Marine Fisheries Advisory Board, The Charleston Harbor Project, and the Department of Natural Resources. This paper is a portion of amaster’s thesis submitted to the University of Charleston, is contribution number 448 of the South Carolina Department of Natural Resources Marine Resources Division, and is contribution number 2325 of the Virginia Institute of Marine Science.



### LITERATURE 

### C ITED

A

NDERSON , J. R., E. E. HARDY , J. T. ROACH , AND R. E. W ITMER

. 1976. A Land Use and Land Cover Classification System forUse with Remote Sensor Data. U.S. Geological Survey Professional Paper 964, Reston, Virginia. A

RNOLD , C. L. AND C. J. GIBBONS . 1996. Impervious surface coverage. Journal of the American Planning Association 62:243–258. BACA, B. J., J. D INGMAN , AND T. E. L ANKFORD . 1988. Evaluation of the impacts of dead-end canals and impoundments on an estuarine ecosystem, p. 201–212. In W. L. Lyke and T. J. Hoban (eds.), Proceedings of the Symposium on Coastal Water Resources, American Water Resources Association. Bethesda, Maryland. B IGGS , R. B., T. B. D E M OSS , M. M. CARTER, AND E. L. B EASLEY

. 1989. Susceptibility of U.S. estuaries to pollution. Aquatic Sciences 1:189–207. B ILYARD , G. R. 1987. The value of benthic infauna in marine

pollution monitoring studies. Marine Pollution Bulletin 18:581– 585. B ROOM , M. J., J. M. DAVIES , B. H UTCHINGS , AND W. HALCROW

.

1991. Environmental assessment of the effects of polluting discharges: Stage I: Developing a post-facto baseline. Estuarine, Coastal and Shelf Science 33:71–87. B ROWN , R. G. 1988. Effects of precipitation and land use on

storm runoff. Water Resources Bulletin 24:421–426. C HAPMAN , P. M., M. A. F ARRELL , AND R. O. B RINKHURST . 1982.Relative tolerances of selected aquatic oligochaetes to individual pollutants and environmental factors. Aquatic Toxicology 2: 47–67. C OHEN , J. E., C. S MALL , A. M ELLINGER, J. G ALLUP , AND J. SACHS

. 1997. Estimates of coastal populations. Science 278:1211–1212. C ULLITON , T. J., M. A. W ARREN , T. R. GOODSPEED , D. G. R EMER, C. M. B LACKWELL , AND J. J. I. M C D ONOUGH . 1990. The Second Report of a Coastal Trends Series: 50 Years of PopulationChange along the Nation’s Coasts 1960–2010. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Rockville, Maryland. D IAZ , R. J. 1980. Ecology of tidal freshwater and estuarine Tubificidae (Oligochaeta), p. 319–330. In R. O. Brinkhurst and D. G. Cook (eds.), Aquatic Oligochaete Biology. Plenum Press, New York. D IAZ , R. J. 1992. Ecosystem assessment using estuarine and marine benthic community structure, p. 67–85. In G. A. Burton, Jr. (ed.), Sediment Toxicology Assessment. Lewis Publishing, Boca Raton, Florida. D IAZ , R. J. AND R. ROSENBERG . 1995. Marine benthic hypoxia: A

review of its ecological effects and the behavioral responses of benthic macrofauna. Oceanography and Marine Biology: An Annual Review 33:245–305. D ODD , M. G. AND T. M. M URPHY. 1996. Management Recommendations for Colonial Waterbirds in the Charleston Harbor Estuary. South Carolina Department of Natural Resources, Charleston, South Carolina. D RIVER, N. E. AND B. M. T ROUTMAN . 1989. Regression models

for estimating urban storm-runoff quality and quantity in the United States. Journal of Hydrology 109:221–236. E DWARDS , S. 1989. Estimates of future demographic changes in

the coastal zone. Coastal Management 17:229–240. E NGLE , V. D. AND J. K. S UMMERS . 1998. Determining the causes

of benthic condition. Environmental Monitoring and Assessment 51:381–397. E NGLE , V. D., K. J. S UMMERS , AND G. R. G ASTON . 1994. A benthicindex of environmental condition of Gulf of Mexico Estuaries. Estuaries 17:372–384. FORTNER, A. R., M. SANDERS , AND S. W. LEMIRE . 1996. Polynuclear aromatic hydrocarbon and trace metal burdens in sediment and the oyster, Crassostrea virginica Gmelin, from twohigh salinity estuaries in South Carolina, p. 445–476. In F. J. Vernberg, W. B. Vernberg, and T. Siewicki (eds.), SustainableDevelopment in the Coastal Zone. University of South Carolina Press, Columbia, South Carolina. FRETWELL , S. D. 1987. Food chain dynamics: The central theory

of ecology? Oikos 50:291–301. FULTON , M. H., G. I. S COTT , A. FORTNER, T. F. B IDLEMAN , AND

B. N GABE . 1993. The effects of urbanization on small high salinity estuaries of the southeastern United States. Archives of Environmental Contamination and Toxicology 25:476–484. G

ASTON , G. R. 1985. Effects of hypoxia on macrobenthos of the inner shelf off Cameron, Louisiana. Estuarine, Coastal and Shelf Science 20:603–613. GIERE , O. AND O. P FANNKUCKE . 1982. Biology and ecology of

marine oligochaeta. A review. Oceanography and Marine Biology: an Annual Review 20:173–308. GRASSLE , J. F. AND J. P. GRASSLE . 1974. Opportunistic life histories and genetic systems in marine benthic polychaetes. Journal of Marine Research 32:253–284. HACKNEY , C. T., W. D. B URBANCK, AND O. P. HACKNEY. 1976. Biological and physical dynamics of a Georgia tidal creek. Chesapeake Science 17:271–280. H OLLAND , A. F., G. H. M. R IEKERK, S. B. LERBERG , L. E. Z IMMER

MAN , D. M. SANGER, T. D. MATTHEWS , G. I. S COTT , M. H. FUL

TON , B. C. T HOMPSON , J. W. DAUGOMAH , J. C. D E V

ANE , K. M. B ECK, AND A. R. D IAZ . 1996. The Tidal Creek Project, InterimReport. Charleston Harbor Project. South Carolina Department of Natural Resources, Marine Research Division, Charleston, South Carolina. H ORLICK, R. G. AND C. B. S UBRAHMANYAM . 1983. Macroinvertebrate infauna of a salt marsh tidal creek. Northeast Gulf Science 6:79–89. H UNTER, J. AND D. R. A RTHUR. 1978. Some aspects of the ecology of Peloscolex benedeni Udekem (Oligochaeta: Tubificidae) in the Thames Estuary. Estuarine, Coastal and Shelf Science 6:197– 208. K

ARR, J. R. 1981. Assessment of biotic integrity using fish communities. Fisheries 6:21–27. K

ARR, J. R. 1991. Biological integrity: A long-neglected aspect of water resource management. Ecological Applications 1:66–84.

### 852 S. B. Lerberg et al.

K

ARR, J. R. AND D. R. D UDLEY . 1981. Ecological perspective on water quality goals. Environmental Management 5:55–68. K

UCKLICK, J. R., S. K. S IVERTSEN , M. SANDERS , AND G. I. S COTT

. 1997. Factors influencing polycyclic aromatic hydrocarbon distributions in South Carolina estuarine sediments. Journal of Experimental Marine Biology and Ecology 213:13–29. L

ASALLE , M. W., M. C. L ANDIN , AND J. G. S IMS . 1991. Evaluation of the flora and fauna of a Spartina Alterniflora marsh established on dredged material in Winyah Bay, South Carolina. Wetlands 11:191–208. LERBERG , S. B. 1997. Effects of watershed development on macrobenthic communities in tidal creeks of the Charleston Harbor area. Master’s Thesis. University of Charleston, Charleston, South Carolina. LEVIN , L. A. 1984. Life history and dispersal patterns in a dense

infaunal polychaete assemblage: Community structure and response to disturbance. Ecology 65:1185–1200. LEVIN , L. A. AND D. V. H UGGETT . 1990. Implications of alternative reproductive modes for seasonality and demography in an estuarine polychaete. Ecology 71:2191–2208. L ONG , E. R., L. J. FIELD , AND D. D. MAC D ONALD . 1998. Predicting

toxicity in marine sediments with numerical sediment quality guidelines. Environmental Toxicology and Chemistry 17:714–727. L ONG , E. R., D. D. MAC D ONALD , S. L. S MITH , AND F. D. CALDER

.

1995. Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments. Environmental Management 19:81–97. MAXTED , J. R., S. B. W EISBERG , J. C. C HAILLOU , R. A. E SKIN , AND F. W. K UTZ . 1997. The ecological condition of dead-end canals of the Delaware and Maryland coastal bays. Estuaries 20:319– 327. M C CALL , P. L. 1977. Community patterns and adaptive strategies

of the infaunal benthos of Long Island Sound. Journal of Marine Research 35:221–266. M C CANN , L. D. AND L. A. LEVIN . 1989. Oligochaete influence on

settlement, growth and reproduction in a surface-deposit feeding polychaete. Journal of Experimental Marine Biology and Ecology 131:233–253. M IDDLEDITCH , B. S., S. R. M ISSLER, D. G. W ARD , J. B. M CV EY

, A. B ROWN , AND A. L. L AWERENCE . 1979. Maturation of penaeid shrimp: Dietary fatty acids. Proceedings of the World Mariculture Society 10:472–476. M ILLER, R. A. AND H. C. J. MATTRAW. 1982. Storm water runoff

quality from three land-use areas in South Florida. Water Resources Bulletin 18:513–519. NATIONAL O CEANIC AND A TMOSPHERIC A DMINISTRATION NATION

AL S TATUS AND TRENDS P ROGRAM . 1991. Second Summary ofData on Chemical Contaminants in Sediments. National Oceanic and Atmospheric Administration Technical Memo. NOS ORCA 59. Office of Oceanography and Marine Assessment, Rockville, Maryland. N UMMEDAL , D., G. F. O ERTEL , D. K. H UBBARD , AND A. C. H INE

.

1977. Tidal inlet variability—Cape Hatteras to Cape Canaveral. Coastal Sediments: 5th Symposium of the Waterway. Port Coastal and Ocean Division, American Society of Engineers, New York. O LSEN , R., N. H. C UTSHALL , AND I. L. L ARSEN . 1982. Pollutantparticle associations and dynamics in coastal marine environments: A review. Marine Chemistry 11:501–533. P EARSON , T. H. AND R. ROSENBERG . 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanography and Marine Biology: An Annual Review 16:229–311. P FANNKUCHE , O. 1978. Abundance and lifecycle of littoral marine and brackish-water Tubificidae and Naididae (Oligochaeta), p. 103–111. In E. Naylor and R. G. Hartnoll (eds.),Cyclic Phenomena in Marine Plants and Animals: Proceedings of the 13th European Marine Biology Symposium. Pergamon Press, New York. P IMM , S. L. AND R. L. K ITCHING . 1987. The determinants of food chain lengths. OIKOS 50:302–307. P LUMB , J R., R. H. 1981. Procedures for Handling and Chemical

Analysis of Sediment and Water Samples. Technical Report EPA/CE-81–1. U.S. Environmental Protection Agency/Corps of Engineers Technical Committee on Criteria for Dredged and Filled Material. Environmental Laboratory, U.S. Army Waterways Experiment Station, Vicksburg, Mississippi. SANGER, D. M. 1998. Physical, chemical and biological environmental quality of tidal creeks and salt marshes in South Carolina estuaries. Ph.D. Dissertation, University of South Carolina, Columbia, South Carolina. SANGER, D. M., A. F. H OLLAND , AND G. I. S COTT . 1999a. Tidal

creek and salt marsh sediments in South Carolina coastal estuaries: I. Distribution of trace metals. Archives of Environmental Contamination and Toxicology 37:445–457. SANGER, D. M., A. F. H OLLAND , AND G. I. S COTT . 1999b. Tidal

creek and salt marsh sediments in South Carolina coastal estuaries. II. Distribution of organic contaminants. Archives of Environmental Contamination and Toxicology 37:458–471. SARDA, R., I. V ALIELA, AND K. FOREMAN . 1996. Decadal shifts ina salt marsh macroinfaunal community in response to sustained long-term experimental nutrient enrichment. Journal of Experimental Marine Biology and Ecology 205:63–81. SAS I NSTITUTE I NC . 1989. SAS/STAT User’s Guide, Version 6,

4th edition. SAS Institute Inc., Cary, North Carolina. S CHUELER, T. 1994. The importance of imperviousness. Watershed Protection Techniques 1:100–111. S HENKER, J. M. AND J. M. D EAN . 1979. The utilization of an intertidal salt marsh creek by larval and juvenile fishes: Abundance, diversity and temporal variation. Estuaries 2:154–163. T EAL , J. M. 1962. Energy flow in the salt marsh ecosystem of

Georgia. Ecology 43:614–624. TIGER/LINE FILES . 1992. Technical documentation. The Bureau

of the Census. The Bureau, 1993, Washington, D.C. V

AN DEN B ROEK, W. L. F. 1978. Dietary habits of fish populations in the Lower Medway estuary. Journal of Fish Biology 3:645–654. V

AN D OLAH , R. F., J. F. HYLAND , A. F. H OLLAND , J. S. ROSEN , AND T. R. SNOOTS . 1999. A benthic index of biological integrity forassessing habitat quality in estuaries of the southeastern United States. Marine Environmental Research 48:269–283. V

ERNBERG , F. J., W. B. V ERNBERG, E. B LOOD , A. FORTNER, M. H. FULTON , H. M CK ELLAR, W. M ICHENER, G. S COTT , T. S IEWICKI , AND K. E L FIGI . 1992. Impact of urbanization on high-salinity estuaries in the southeastern united states. Netherlands Journal of Sea Research 30:239–248. W

ARWICK, R. M. AND K. R. C LARKE . 1991. A comparison of somemethods for analyzing changes in benthic community structure. Journal of Marine Biological Association of the United Kingdom 71:225–244. W

EINSTEIN , M. P., S. L. W EISS , AND M. F. W ALTERS . 1980. Multipledeterminants of community structure in shallow marsh habitats, Cape Fear River Estuary, North Carolina, USA. Marine Biology 58:227–243. W

EISBERG , S. B., A. F. FRITHSEN , A. F. H OLLAND , J. F. PAUL , K. J. S OTT , J. K. S UMMERS , H. T. W ILSON , R. V ALENTE , D. G. H EIM

BUCH , J. GERRISEN , S. C. S CHIMMEL , AND R. W. L ATIMER . 1990.EMAP-Estuaries Virginian Province 1990 Demonstration Project Report. EPA-600/R-92/100. U.S. Environmental Protection Agency, Environmental Research Laboratory, Narragansett, Rhode Island. W

EISBERG , S. B., J. A. R ANASINGHE , D. M. DAUER, L. S CHAFFNER, AND R. J. D IAZ . 1997. An estuarine benthic index of biotic integrity. Estuaries 20:149–158. W

ENNER, C. 1992. Red Drum: Natural History and Fishing Techniques in South Carolina. Marine Resources Division, South Carolina Wildlife and Marine Resources Department, Charleston, South Carolina. W

ENNER, E. L. AND H. R. B EATTY . 1993. Utilization of shallowWatershed Development in Tidal Creeks 

### 853

estuarine habitats in South Carolina, U.S.A., by postlarval and juvenile stages of Penaeus spp. (Decapoda: Penaeidae). Journal of Crustacean Biology 13:280–295. W

ENNER, E., A. F. H OLLAND , AND D. SANGER . 1999. Assessing short-term variability in dissolved oxygen and other water quality variables in shallow estuarine habitats, p. 802–806. In Ocean Community Conference 1998 Proceedings, Volume 2,November 16–19, 1998. Marine Technology Society, Washington, D.C. W IEGERT , R. G. AND B. J. FREEMAN . 1990. Tidal salt marshes of the southeast Atlantic Coast: A community profile. United States Fish and Wildlife Service Biological Report 85:1–67. W

ILTSE , W. I., K. H. F OREMAN , J. M. TEAL , AND I. V ALIELA. 1984. Effects of predators and food resources on the macrobenthos of salt marsh creeks. Journal of Marine Research 42:923–942.

Received for consideration, May 26, 1999 Accepted for publication, August 1, 2000