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8.0
Howe Creek
Howe Creek was sampled for physical parameters, nutrients, chlorophyll a , and fecal coliform bacteria at five locations during 2003-2004 (HW-M, HW-FP, HW-GC, HW-GP and HW-DT, Fig. 8.1). Turbidity was low near the ICW and exceeded North Carolina water quality standards on only one occasion at HW-DT (Table 8.1; Appendix B). Dissolved oxygen concentrations were generally good in Howe Creek, with HW-GP below the standard of 5.0 mg/L on two occasions (Appendix B). Nutrient levels were generally low except for nitrate at HW-DT (Table 8.2). Nitrate levels showed a slight increase over levels in 2002-2003, especially at the uppermost stations (Mallin et al. 2004). Median inorganic molar N/P ratios were low, reflecting low nitrate levels, and, indicating that nitrogen was probably the principal nutrient limiting phytoplankton growth at all stations. There was one major algal bloom of 56 mg/L as chlorophyll a at HW-DT and a minor bloom of 28 mg/L at HW-GP. Since wetland enhancement was performed in 1998 above Graham Pond the creek below the pond at HW-GP has had fewer and smaller algal blooms than before the enhancement (Fig. 8.2).
Table 8.1. Water quality summary statistics for Howe Creek, August 2003-July 2004, as mean (st. dev.) / range.
Salinity
Diss. oxygen Turbidity
Chlor a
Fecal coliforms
(ppt)
(mg/L) (NTU)
(mg/L)
(CFU/100 mL)
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HW-M
34.2 (1.9)
8.0 (1.8)
4 (3)
1.2 (0.9)
3
31.5-37.5
5.2-10.8
0-11
0.3-2.8 1-18
HW-FP
33.7 (2.1)
7.9 (2.0)
4 (3)
0.9 (0.6)
5
30.4-37.3
5.0-11.0
0-10
0.3-1.9 1-41
HW-GC
29.3 (4.5)
7.6 (2.3)
6 (3)
1.3 (0.8)
21
23.0-36.8
4.0-11.6
1-14
0.4-2.4 4-139
HW-GP
14.5 (11.9)
7.4 (2.3)
10 (4)
6.5 (8.0)
185
0.6-30.1
4.1-10.9 3-18
0.9-27.9
46-465
HW-DT
4.2 (6.1)
8.6 (2.2)
15 (8)
10.2 (17.0) 419
0.2-18.7
6.1-12.6 4-28
0.7-56.1
70-1810
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Table 8.2. Nutrient
concentration summary statistics for Howe Creek, August 2003-
July 2004, as mean
(st. dev.) / range, N/P ratio as mean / median.
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Nitrate
Ammonium
Orthophosphate Molar N/P
ratio
(mg/L)
(mg/L)
(mg/L)
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HW-FP
0.007 (0.006)
0.013 (0.007)
0.008
(0.003) 5.4
0.003-0.022
0.008-0.029
0.006-0.015
4.3
HW-GC
0.008 (0.007)
NA
0.010 (0.004)
NA
0.003-0.026
0.006-0.019
HW-GP
0.022 (0.023)
0.019
(0.013)
0.011 (0.004)
8.2
0.003-0.067
0.008-0.045
0.006-0.021
6.8
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Fecal coliform
bacterial abundances were low near the Intracoastal Waterway, moderate in
mid-creek, and high in the uppermost stations (Table 8.1;
Fig. 8.3).
HW-GP exceeded the North Carolina human contact standard on five of ten
occasions, and HW-DT exceeded the standard on seven of nine occasions (Appendix
B). After several years of
improvement (i.e. lower fecal coliform counts in the upper two stations), in
2003-2004 Howe Creek experienced a degradation in bacteriological water quality
(Fig. 8.3). Both Station HW-GP and
HW-DT experienced a doubling in geometric mean fecal coliform counts compared
with the period 2001-2003. This
occurred in spite of the moving of Masons Inlet across the waterway.
The increase in coliform counts may be a result of the continuing
development occurring in the Howe Creek headwaters area along Military Cutoff.
It has been demonstrated for New Hanover County (Mallin et al.2000b) and
the Charleston, S.C. area (Holland et al. 2004) that increases in human
development on land are strongly correlated statistically with increases in
tidal creek fecal coliform bacteria counts.
This is particularly troublesome since Howe Creek is considered an
Outstanding Resources Water by the State of North Carolina.
