8.0  Howe Creek Water Quality 

            Howe Creek was sampled for physical parameters, nutrients, chlorophyll a , and fecal coliform bacteria at five locations during 2002-2003 (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-GC and HW-GP below the standard of 5.0 mg/L on two occasions each (Appendix B). 

Nutrient levels were generally low in 2002-2003 (Table 8.2).  Nitrate levels were similar to 2001-2002 (Mallin et al. 2003a).  Median inorganic molar N/P ratios were moderate, indicating that nutrients were relatively balanced at all stations.   There were algal blooms of 50 mg/L as chlorophyll a at HW-DT and 60 mg/L at HW-DT.  During the early and mid-1990s there were frequent algal blooms occurring in Howe Creek at station HW-GP, located just below Graham Pond.  In the late 1990s a wetland enhancement was performed in the upper portion of Graham Pond that involved increasing the retention time of water before it could flow downstream and into Howe Creek.  By increasing retention time, more nutrients would be taken up by the wetland plants and more denitrification would take place, reducing nutrient loading to the creek.  The results have been positive for Howe Creek (Fig. 8.2).  The severity of algal blooms has considerably decreased at HW-GP since 1998, demonstrating that wetland enhancement is a viable, and long-lasting means of reducing eutrophication in tidal creeks.  We recommend that further wetland acquisition and enhancement be undertaken in the upper Howe Creek watershed to reduce impacts to the creek from the ongoing construction along Military Cutoff.

Fecal coliform bacteria abundances were low near the Intracoastal Waterway, moderate in mid-creek, and high in the uppermost stations (Table 8.1).  HW-GC and HW-GP exceeded the North Carolina human contact standard on two of eleven occasions, and HW-DT exceeded the standard on four of eleven occasions (Appendix B).  Over the period 1993 – 2003 fecal coliform abundances have remained similar at the three lower creek stations (Fig. 8.3).  However, a decrease was noted at the upper two sites between 1993-2000 and 2001-2003.  During the early period a considerable amount of construction activity was ongoing close to the creek, first at Landfall and later on the north side of the creek.  After 2000 the near-creek construction activity slowed down greatly, allowing for revegetation and earth stabilization; this potentially accounted for the fecal coliform decrease at HW-GP and HW-DT.  Additionally, a severe drought occurred during the latter period (particularly during 2002) that reduced rainfall-driven runoff of pollutants into the tidal creeks, which would also help account for a fecal bacteria decrease.  At this writing a large amount of construction is occurring at the Mayfaire location along Military Cutoff.  A student study in spring 2003 demonstrated that runoff mitigative measures at Mayfaire during the earth-moving phase were doing a good job of keeping fecal coliform bacteria from running off-site toward Howe Creek.  We will continue to monitor this area during subsequent construction and residential development to assess any potential off-site pollutant runoff.

During early 2002 a new channel was dredged and Mason Inlet was subsequently moved from its previous location at the north end of Wrightsville Beach to a location 2500 ft north.  There had been speculation that such an activity along the barrier islands would improve tidal exchange in the tidal creeks and reduce fecal coliform counts.  Creek mouth dredging during 1995 and 1996 in Futch Creek had that effect, increasing salinities and reducing fecal coliform counts significantly.  Thus, we compared six calendar months of Howe Creek salinity and fecal coliform data collected before and after inlet moving to see if such a change did occur. 

Sampling in nearby Howe Creek, directly across the Atlantic Intracoastal Waterway from Mason Creek, showed little change either way in fecal coliform abundance at the lower and middle creek stations before or after dredging.  There was a 43% decrease in fecal coliform concentrations at the uppermost Howe Creek station following inlet relocation.  However, salinities collected at the same time as fecal coliforms actually showed lower values (rather than higher) in Howe Creek following the dredging of Mason Inlet.  Additionally, statistical analysis showed a positive correlation between rainfall and fecal coliform counts in upper Howe Creek.   Thus, the fecal coliform decrease in upper Howe Creek following inlet relocation appeared to be related to localized rainfall and runoff patterns rather than increased salinity resulting from inlet relocation.  The full report on the Mason Inlet monitoring project (Mallin et al. 2003b) is available on-line at http://www.uncwil.edu/cmsr/aquaticecology/TidalCreeks/Index.htm.

UNCW graduate student Jason Hales carried out a number of tidal exchange studies in the creeks during 1998-2000.  Results from Howe Creek showed an average daily tidal exchange rate of 46% in July 1998 (Hales 2001).  Repeating that study in Howe Creek in August 2003 (after inlet moving) showed a decrease in average daily tidal exchange rate to 38% (Hales 2003).  Thus, the dredging and moving of Mason Inlet did not improve the circulation of Howe Creek.  Hales (2003) did find an increase in tidal exchange rates from 2000 to 2003 in more distant Pages Creek, however.

                        Salinity          Diss. oxygen        Turbidity        Chlor a          Fecal coliforms
                        (ppt)                (mg/L)                   (NTU)            (mg/L)              CFU/100 mL
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HW-M             33.1 (1.9)     7.6 (2.1)                 6 (3)             1.6 (1.1)               3
                        28.2-34.9     4.7-10.8                 3-12              0.5-3.2                1-143 

HW-FP            33.1 (1.8)    7.5 (2.2)                5 (2)               1.3 (0.9)               1
                         28.7-34.9    4.7-10.8                2-10               0.4-3.1                 0-181 

HW-GC           29.7 (4.3)    7.2 (2.3)                8 (3)               2.4 (2.3)               23
                        20.3-34.4      4.3-11.0                3-14               0.4-7.4                 0-870 

HW-GP           19.2 (9.4)    6.9 (2.1)                 8 (4)               6.0 (6.2)              93
                        2.5-32.1        4.5-11.1                3-15               0.9-18.0              17-1455 

HW-DT            4.2 (5.6)      7.9 (2.1)                 13 (9)              20.3 (21.1)         201
                        0.1-15.2       4.9-11.5                  5-38               1.1-60.2             21-2020

Table 8.2. Nutrient concentration summary statistics for Howe Creek, August 2002-July 2003,
as mean (st. dev.) / range, N/P ratio as mean / median.
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                        Nitrate                         Ammonium               Phosphate    Molar N/P ratio
                        (mg/L)                         (mg/L)                         (mg/L)
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HW-M             0.007 (0.005)            0.022 (0.013)           0.004 (0.003)            24
                        0.001-0.018              0.004-0.049              0.001-0.009              16 

HW-FP           0.006 (0.007)            0.021 (0.012)            0.005 (0.003)           16
                        0.001-0.028              0.006-0.039              0.001-0.010             16 

HW-GC            0.008 (0.006)                  NA                       0.006 (0.004)           NA
                          0.002-0.023                                                 0.001-0.012                

HW-GP            0.012 (0.009)           0.023(0.013)             0006 (0.004)            26
                         0.001-0.029              0.008-0.041               0.001-0.011            14 

HW-DT            0.027 (0.029)            0.029(0.031)             0.008 (0.006)           24
                        0.001-0.078               0.007-0.117              0.001-0.020             17
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