Threat of Eutrophication at Waties Island Coastal System, South Carolina

Abstract:

Marine pollution has become a major topic over the years for scientific research teams, who set out to better understand these pollutants and how they are changing the environment. The present study analyses and discusses marine pollutants such as Eutrophication at Waties Island Coastal System. To understand the extremes at which eutrophication is occurring according to specific parameters. To also see if there is a correlation between estuary and beach systems and if there are any seasonal or tidal influences on the parameters which affect eutrophication. Temperature, salinity, coliform bacteria, plastics and water samples were all collected over a four-week period between January 28th and February 17th, 2019, then analyzed in the lab. It was found that there was a high threat of eutrophication in phosphorus with a moderate threat in nitrogen and chlorophyll A and signs of biological stress for dissolved oxygen. From this study it can be concluded that the Waties Island Coastal System can be influenced by eutrophication threats and other marine pollutants and varies with each environment (estuary vs beach). Marine pollutants have the potential to affect the entirety of the coastal system and actions should be taken to inhibit any more damage to the system.

Introduction:

Estuaries and beaches play a very important role within the environment (Borja & Bricker 2008). Estuaries act as highly productive ecosystems, they have many sources of organic carbon and are very nutrient rich. (Cloern 1987). Beaches contain patterns between wave climate, sand storage and climatic features that are considered relevant in the ‘age of extinction’ and biodiversity (McLachlan et al. 1993). Estuaries and coastal systems have been pushed from their baseline of rich, diverse, and productive ecosystems due to human impacts (Lotze et al. 2006). Since these two environments act as extremely productive and important parts of the ecosystem, it is paramount that they are monitored and studied to better understand how human impacts could change the environment. 

A major topic caused by human impacts is eutrophication of marine environments such as estuaries, marshes and beaches. Eutrophication is defined to be an over enrichment of nutrients in an aquatic environment (Carpenter 2005) If eutrophication levels are high enough, it could reach the point to be non-reversible (Carpenter 2005). Eutrophication has many parameters that control how apparent it is occurring in a system, these parameters include algal conditions (chlorophyll A), nutrients (nitrogen, phosphorus), dissolved oxygen (Bricker et al. 1999). Other anthropogenic impacts include salinity, turbidity, pH, bacteria and microplastics (Borja & Bricker 2008).

The present study took place at Dunn Sound and Waties Island Beach which are a part of Waties Island, the Anne Tilghman Boyce Coastal Reserve in Myrtle Beach, South Carolina, USA. Sample collection occurred over a four-week period starting January 28th 2019 to February 17th 2019. Waties Island is a 5 km long, 0.5km wide, mixed-energy barrier island located at the most northern part of South Carolina along the Grand Strand coastal system. (Wright et al. 2003). Waties Island acts as a good environment for the present study since it contains both an estuary system and a beach system and is surrounded by a highly populated location, Myrtle Beach.

Sampling at Dunn Sound (estuarine environment) and Waties Island Beach (beach environment) gave researchers a better understanding of how the two different environments are being affected by human impacts. Multiple water samples were collected over a four-week period to analyze parameters such as bacteria, plastics, salinity, chlorophyll, nitrogen, phosphorous, and oxygen. The main goal of the present study was to determine if human impacts such as eutrophication are occurring at Waties Island. It was also tested to see if there was a significant difference between Dunn Sound and Waties Island Beach for the mentioned parameters and if these parameters were affected by seasonal transitions.

Methods:

Site Description

Waties Island is a coastal reserve that was donated to Coastal Carolina University. The two sample locations for this research project were both at Waties Island. Samples of water were collected at Dunn Sound and Waties Island Beach (figure 1) for four weeks in row. The Dunn Sound location was at

The nitrate and nitrite would now be analyzed using the Hach method. NitraVer 6 reagent was added to two standard nitrate and nitrite samples. After approximately 2.5 minutes of constant mixing, the samples were allowed to settle for 10 minutes. The same process took place for both samples collected in the field. The decant from each tube was poured into a new tube leaving behind any settled remains. NitriVer 3 reagent was poured into the nitrite standard. This tube was only mixed for 30 seconds. The tube once mixed was allowed to settle for 15 minutes. The same process took place for both samples collected in the field. A spectrophotometer was set to measure absorbance at 543 nm. The spectrophotometer was zeroed out with DI water. The standards for both the nitrate and nitrite samples were poured into cuvettes and measured with the spectrophotometer. Concentration and absorbance values given by the spectrophotometer were documented. This process was completed for each field sample as well.

Ammonium

To analyze the ammonium, the Holmes method was used. A light sensitive mixing reagent was added to the tubes. Once added, the tubes were covered to not allow light exposure, and then they were left alone for 2 hours to react. Once left for ample time, the sample was added to a cuvette and placed in a fluorometer. The fluorometer was set to “Measure Fluorescence Raw” and the measurement was taken. Once completed, the second sample and the standard were tested identically. After all samples were tested, the concentrations could be calculated in each.

Phosphate

Using the Murphy and Riley method, phosphate can be analyzed. There was 1 mL of a mixing reagent added to each sample. The samples were then mixed for 15 seconds. After allowing the samples to rest for 15 minutes they were poured into cuvettes. A spectrophotometer was set to 880 nm. Once set, the cuvette was placed into the spectrophotometer and the absorbance was documented. The process was completed another time for the second sample and the standard sample.

Chlorophyll a/Phaeophytin a

To analyze Chlorophyll a and Phaeophytin a, the samples were placed in a centrifuge for 5 minutes. Once centrifuged, some of the sample was poured into a glass fluorometer tube. The fluorometer was set to “Measure Fluorescence Raw”. The value was recorded for both samples. Cuvettes were removed and 2 drops of HCL concentrate were added to each. The samples after this step were allowed to sit for 30 seconds until the samples were remeasured. These steps were done the same for the second sample as well. Using the RFU value found, the [chlorophyll a] and [pheophytin a] could be calculated.

$\left[\mathit{chlorophyll\; a}\right]=$ $F_s\mathit{ x}\left(\frac{r}{r–1}\right)\mathit{x }\left(R_B–R_A\right)\mathit{ x }\left(\frac{V_E}{V_S}\right)$

Where,

$V_E=$

mL of acetone extract $=$

10 mL

$V_S=$

mL of sample filtered $=$

25 mL

$F_S=$

0.000318

r $=$

1.866

$\left[\mathit{Pheophytin\; a}\right]=F_S\mathit{ x }\left(\frac{r}{r–1}\right)x\left(r{R}_A–R_B\right)\mathit{ x }\left(\frac{V_E}{V_S}\right)$

Where,

$V_E=$

mL of acetone extract $=$

10 mL

$V_S=$

mL of sample filtered $=$

25 mL

$F_S=$

0.000318

r $=$

1.866

Results:

Temperature

The average temperature in Dunn Sound measured with the Pro2030 on 1/28/19 was 10C, 12.75C on 2/3/19, 10.65C on 2/10/19 and 11.7C on 2/17/19 (Figure 2). The average temperature on Waties Island Beach measured with the Pro2030 on 1/28/19 was 10.9C, 11.6C on 2/3/19, 11.25C on 2/10/19 and 11.95C on 2/17/19 (Figure 2). The average temperature in Dunn Sound measured with the ProODO on 1/28/19 was 10.3C, 12.8C on 2/3/19, 10.45C on 2/10/19 and 11.8C on 2/17/19 (Figure 3). The average temperature on Waties Island Beach measured with the ProODO on 1/28/19 was 11C, 11.8C on 2/3/19, 11.25C on 2/10/19 and 12.05C on 2/17/19 (Figure 3).

Salinity

  According to the Pro2030, the salinity on 1/28/19 in Dunn Sound was 13.6ppt, 15.5ppt on 2/3/19, 14.8ppt on 2/10/19 and 21.8ppt on 2/17/19 (Figure 4). The average salinity at Waties Island Beach was 31.1ppt on 1/28/19, 30.9ppt on 2/3/19, 32.8ppt on 2/10/19 and 33.0ppt on 2/17/19 (Figure 4). Another method used to determine the salinity of the water was to do a titration of the sample. According to the titration, the salinity on 1/28/19 in Dunn Sound was 14.1ppt, 15.8ppt on 2/3/19, 15.1ppt on 2/10/19 and 22.6ppt on 2/17/19 (Figure 5). According to the titration, the salinity on 1/28/19 on Waties Island Beach was 31.7ppt, 31.4ppt on 2/3/19, 33.2ppt on 2/10/19 and 34.1ppt on 2/17/19 (Figure 5). According to (Figure 6), our accuracy was very high between our calculated titration salinity and documented YSI values due to our $R^2$

value of 0.99.

Oxygen

 There were two ways dissolved oxygen was measured. One process consisted of using a Pro2030, and the other was calculated via titration. At Dunn Sound, using the Pro2030 in $\frac{\mathit{mg}}{L}$

on 1/28/19 the dissolved oxygen $$

was 9.68, 8.8 on 2/3/19, 7.02 on 2/10/19, and 6.95 on 2/17/19 (Figure 7). On Waties Island Beach, using the Pro2030 in $\frac{\mathit{mg}}{L}$

on 1/28/19 the dissolved oxygen was 10.52, 10.95 on 2/3/19, 7.79 on 2/10/19, and 8.8 on 2/17/19 (Figure 7). The dissolved oxygen in Dunn Sound calculated via titration in $\frac{\mathit{mg}}{L}$

on 1/28/19 was 10.2, 9.1 on 2/3/19, 9.2 on 2/10/19 and 4.6 on 2/17/19 (Figure 8). The dissolved oxygen on Waties Island Beach calculated via titration in $\frac{\mathit{mg}}{L}$

on 1/28/19 was 11.0, 8.8 on 2/3/19, 7.9 on 2/10/19 and 5.5 on 2/17/19 (Figure 8). The titration values in $\frac{\mathit{mg}}{L}$

were also calculated in $\frac{\mathit{\mu mol}}{L}$

. The dissolved oxygen in Dunn Sound calculated via titration in $\frac{\mathit{\mu mol}}{L}$

on 1/28/19 was 317.7, 284.1 on 2/3/19, 286.5 on 2/10/19 and 144.4 on 2/17/19 (Figure 9). The dissolved oxygen on Waties Island Beach calculated via titration in $\frac{\mathit{\mu mol}}{L}$

on 1/28/19 was 342.6, 274.4 on 2/3/19, 247.3 on 2/10/19 and 170.7 on 2/17/19 (Figure 9).

 Using the Pro2030, ProODO and titration, oxygen percent saturation values were found for both Dunn Sound and Waties Island Beach. According to the Pro2030, the oxygen percent saturation in Dunn Sound on 1/28/19 was 93.7%, 83.55% on 2/3/19, 93.3% on 2/10/19 and 75% on 2/17/19 (Figure 10). According to the Pro2030, the oxygen percent saturation on Waties Island Beach on 1/28/19 was 102.3%, 105.45% on 2/3/19, 103.85% on 2/10/19 and 78% on 2/17/19 (Figure 10). According to the ProODO, the oxygen percent saturation in Dunn Sound on 1/28/19 was 86.4%, 83.2% on 2/3/19, 78.6% on 2/10/19 and 80.3% on 2/17/19 (Figure 11). According to the ProODO, the oxygen percent saturation on Waties Island Beach on 1/28/19 was 95.2%, 100.8% on 2/3/19, 88.6% on 2/10/19 and 90.3% on 2/17/19 (Figure 11). According to the titration, the oxygen percent saturation in Dunn Sound on 1/28/19 was 98.6%, 94.5% on 2/3/19, 90% on 2/10/19 and 49.1% on 2/17/19 (Figure 12). According to the titration, the oxygen percent saturation on Waties Island Beach on 1/28/19 was 121.3%, 98.4% on 2/3/19, 88.1% on 2/10/19 and 63% on 2/17/19 (Figure 12). The oxygen percent saturation values from the Pro2030 were compared to the values found via titration to reveal an $R^2$

value of 0.61431 (Figure 13).

pH

 The pH values in Dunn Sound were 7.45 on 1/28/19, 7.53 on 2/3/19, 7.77 on 2/10/19 and 7.69 on 2/17/19 (Figure 14). The pH values on Waties Island Beach were 7.11 on 1/28/19, 8.17 on 2/3/19, 8.23 on 2/10/19 and 8.14 on 2/17/19 (Figure 14).

Nitrate and Nitrite

 The $N{O}_3^{–}+N{O}_2$

values in $\frac{\mathit{\mu mol}}{L}$

in Dunn Sound were 1.8 on 1/28/19, 4.1 on 2/3/19, 3.0 on 2/10/19 and 3.5 on 2/17/19 (Figure 15). The $N{O}_3^{–}+N{O}_2$

values in $\frac{\mathit{\mu mol}}{L}$

  on Waties Island Beach were 1.1 on 1/28/19, 1.9 on 2/3/19, 2.8 on 2/10/19 and 3.6 on 2/17/19 (Figure 15).

 Dissolved Inorganic Nitrogen levels in $\frac{\mathit{mg}}{L}$

in Dunn Sound were 0.05 on 1/28/19, 0.1 on 2/3/19, 0.08 on 2/10/19 and 0.08 on 2/17/19 (Figure 16). Dissolved Inorganic Nitrogen levels in $\frac{\mathit{mg}}{L}$

on Waties Island beach were 0.03 on 1/28/19, 0.03 on 2/3/19, 0.05 on 2/10/19 and 0.05 on 2/17/19 (Figure 16).

To compare $N{O}_3^{–}+N{O}_2$

, ammonia and oxygen percent saturation in both Dunn Sound and Waties Island Beach, (Figures 17 and 18) were created.

Phosphate

In Dunn Sound, the phosphate levels in $\frac{\mathit{mg}}{L}$

were 0.02 on 1/28/19, 0.05 on 2/3/19, 0.01 on 2/10/19 and 0.03 on 2/17/19 (Figure 19). On Waties Island Beach, the phosphate levels in $\frac{\mathit{mg}}{L}$

were 0.01 on 1/28/19, 0.01 on 2/3/19, 0.01 on 2/10/19 and 0.03 on 2/17/19 (Figure 19). In Dunn Sound, the phosphate levels in $\frac{\mathit{mol}}{L}$

were 0.6 on 1/28/19, 1.5 on 2/3/19, 0.3 on 2/10/19 and 0.9 on 2/17/19 (Figure 20). On Waties Island Beach, the phosphate levels in $\frac{\mathit{mol}}{L}$

were 0.3 on 1/28/19, 0.4 on 2/3/19, 0.3 on 2/10/19 and 0.8 on 2/17/19 (Figure 20).

Turbidity

 Turbidity levels in NTU in Dunn Sound were 5.035 on 1/28/19, 19.6 on 2/3/19, 4.97 on 2/10/19 and 7.55 on 2/10/19 (Figure 21). Turbidity levels in NTU in Dunn Sound were 7.5 on 1/28/19, 11.3 on 2/3/19, 25.7 on 2/10/19 and 27.15 on 2/10/19 (Figure 21).

Coliform Bacteria

E. coli CFU per 100mL in Dunn Sound were 10 on 1/28/19, 104 on 2/3/19, 16.8 on 2/10/19 and 42 on 2/17/19 (Figure 22). E. coli CFU per 100mL on Waties Island Beach were 0 on 1/28/19, 1 on 2/3/19, 0 on 2/10/19 and 1 on 2/17/19 (Figure 22).

Non-E. coli CFU per 100mL in Dunn Sound were 371 on 1/28/19, 525 on 2/3/19, 261 on 2/10/19 and 395 on 2/17/19 (Figure 23). Non-E. coli CFU per 100mL on Waties Island Beach were 1104 on 1/28/19, 439 on 2/3/19, 410 on 2/10/19 and 19 on 2/17/19 (Figure 23).

(Figure 24) shows the total CFU’s per 100mL collected at both Dunn Sound and Waties Island Beach. To compare CFU correlation to the water’s turbidity, (Figure 25) was generated. This revealed a $R^2$

value of 0.12221.

Chlorophyll a/Phaeophytin a

 In Dunn Sound, Chlorophyll a levels were 2.8 on 1/28/19, 7.0 on 2/3/19, 2.3 on 2/10/19 and 3.0 on 2/17.19 (Figure 26). On Waties Island Beach, Chlorophyll a levels were 4.1 on 1/28/19, 5.8 on 2/3/19, 12.7 on 2/10/19 and 7.0 on 2/17.19 (Figure 26).

 In Dunn Sound, Phaeophytin a levels were 2.5 on 1/28/19, 9.2 on 2/3/19, 2.9 on 2/10/19 and 4.5 on 2/17.19 (Figure 27). On Waties Island Beach, Phaeophytin a levels were 3.2 on 1/28/19, 5.8 on 2/3/19, 13.1 on 2/10/19 and 8.1 on 2/17.19 (Figure 27).

 In Dunn Sound, Chlorophyll a/Phaeophytin a levels were 1.1 on 1/28/19, 0.8 on 2/3/19, 0.9 on 2/10/19 and 0.7 on 2/17.19 (Figure 28). On Waties Island Beach, Chlorophyll a/Phaeophytin a levels were 1.3 on 1/28/19, 1.1 on 2/3/19, 1.1 on 2/10/19 and 0.9 on 2/17.19 (Figure 28).

  To compare Chlorophyll a and turbidity, (Figure 29) was made. An $R^2$

value of 0.7398 was generated. To compare Phaeophytin a and turbidity, (Figure 30) was made. An $R^2$

value of 0.8171 was generated.

Microplastics

 Microplastics were counted per liter. The documented microplastic counts in Dunn Sound were 25 on 1/28/19, 121 on 2/3/19, 180 on 2/10/19 and 186 on 2/17/19 (Figure 31). The documented microplastic counts on Waties Island Beach were 18 on 1/28/19, 82 on 2/3/19, 417 on 2/10/19 and 80 on 2/17/19 (Figure 31).

 To see if turbidity had a correlation with the amount of microplastics found per liter, (Figure 32) was generated. The $R^2$

value from this figure was 0.1963.

(Figure 1)

Figure 2. The recorded temperate using the Pro2030 at both Dunn Sound (Grey) and Waties Island Beach (white) on each of the four sampling days.

(Figure 3)

Figure 4. The salinity taken in the field using the Pro2030 at both locations of Dunn Sound and Waties Island Beach.  These samples were taken on all four days of data collection.

(Figure 5)

(Figure 6)

Figure 7. The O₂ in mg/L collected using the Pro2030 in the field at Waties Island Beach and Dunn Sound on all four days of data collection.

Figure 8. The amount of O₂ mg/L recorded through titrations using water samples collected in the field at both Waties Island Beach and Dunn Sound.

Figure 9. The amount of O₂ in micro-moles/L recorded through titrations in the lab using water samples collected in the field at Waties Island Beach and Dunn Sound during all four days of data collection.

Figure 10. The O₂ in percent saturated that was recorded using the Pro2030 in the field at both Waties Island Beach and Dunn Sound during all four data collection days.

Figure 11. The O₂ in percent saturation of the water sample recorded by the ProODO in the field at both Waties Island Beach and Dunn Sound on all four days of data collection.

Figure 12. The O₂ in percent saturation found through titrations using samples collected form Waties Island Beach and Dunn Sound

Figure 13. The comparison between O₂ in percent saturation recorded through titrations and O₂ in percent saturation recorded by the Pro2030 and the ProODO from samples collected at all four data collection days at both Dunn Sound and Waties Island Beach.

(Figure 14)

(Figure 15)

(Figure 16) ADD LINE

(Figure 17) Dunn Sound

(Figure 18) WIB

(Figure 19)

(Figure 20)

Figure 21. The turbidity of both Dunn Sound and Waties Island Beach on each of the four data collection days

Figure 22. The E. coli CFU/100mL sampled at both Waties Island Beach and Dunn Sound on all four of the data collection days.

Figure 23. The non-E. coli coliforms of CFU/100 mL found at both Waties Island Beach and Dunn Sound on all four days of data collection.

Figure 24. The total CFUs/100mL sampled at both Waties Island Beach and Dunn Sound during the four days of sample collection.

Figure 25. The comparison of turbidity versus total CFUs found in samples from the field on all four days of data collection in both Dunn Sound and Waties Island Beach.

(Figure 26)

(Figure 27)

(Figure 28)

(Figure 29)

(Figure 30)

(Figure 31)

(Figure 32)

(Figure 33)

(Figure 34)

(Figure 35)

(Figure 36)

(Figure 37)

(Figure 38)

(Figure 39)

(Figure 40)

(Figure 41)