University of South Carolina, Baruch Marine Field Laboratory North Inlet Winyah Bay National Estuarine Research Reserve

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1 Nutrients, Algae and Suspended Sediments in Stormwater Detention Ponds How do Surfside Beach ponds compare to others along the Grand Strand? Erik M. Smith University of South Carolina, Baruch Marine Field Laboratory North Inlet Winyah Bay National Estuarine Research Reserve Presentation to the Town of Surfside Beach, October 22, 13

2 Research Projects Conducted in Surfside Beach: 1. Broad survey of water quality in 26 residential ponds along the grand strand (10) 2. Water and material transport through Dogwood and Withers swashes (12 13)

3 Research Projects Conducted in Surfside Beach: 1. Broad survey of water quality in 26 residential ponds along the grand strand (10) Surfside Beach ponds included in sampling: Dogwood Magnolia Cherry Floral Parameters measured: Nutrients Nitrogen (total & inorganic forms) Phosphorus (total & inorganic forms) Algal abundance Total suspended sediments Dissolved and organic carbon Oxygen concentrations Physical stratification Light attenuation Netecosystem ecosystem production

4 Research Projects Conducted in Surfside Beach: 1. Broad survey of water quality in 26 residential ponds along the grand strand (10) 2. Water and material transport through Dogwood and Withers swashes (12 13) Location of Dogwood sampling: 3 headwater locations within drainage basin Deerfield/Plantation Dr. Caropines/Glenns Bay Rd. Mallard Lakes Dogwood spillway Parameters measured: Hydrology Rainfall Surface flows Groundwater input Nutrients Algal abundance Total suspended sediments Organic carbon Primary production/respiration

5 Linking nutrients and algae: Plants (algae) are the base of the food chain. without nutrients there would be no algae without algae, ponds cannot support fish, wildlife, etc Problem becomes too much of a good thing. Excessive and/or noxious ( Harmful ) algal growth Decomposition of algae causes oxygen depletion, leading to fish kills Leads to potential water quality problems for receiving waters The Goldilocks dilemma: No nutrients = no life in pond. Right amount of nutrients = healthy, balanced pond ecosystem. Too much nutrients = unbalanced, dysfunctional pond ecosystem.

6 Water quality in 26 residential ponds along the grand strand How do nutrient levels vary with increasing development? How do ponds respond to nutrient enrichment? How do suspended sediments (turbidity) vary with increasing development? Study Ponds: 26 residential ponds 2 Undeveloped 7 Low residential development 10 Medium residential development 7 High residential development Surfside Ponds: Cherry Magnolia Dogwood Floral Pond size median Pond depth median : acres = 2.2 acres : 3 14 ft = 5 ft Sampled d8 times from May Sept.

7 Total nutrient concentrations among ponds: 00 No develop. Total Nit trogen ( g L 1 ) 0 Low Avg. = 466 Medium Avg. = 766 High Avg. = 1011 Low Medium High max mean 10 min Total Ph hosphorus ( g L 1 ) 10 Low Avg. = 14 Medium Avg. = 62 High Avg. =

8 Total nutrient concentrations among ponds: Total Nit trogen ( g L 1 ) Low Avg. = 466 Medium Avg. = 766 High Avg. = No develop. Low Medium High max mean min 0 Total Ph hosphorus ( g L 1 ) 10 Low Avg. = 14 Medium Avg. = 62 High Avg. = = Cherry 15 = Dogwood 16 = Magnolia 17 = Floral

9 Total Phosphorus is a strong predictor of algal abundance (as measured by Chlorophyll concentrations) Relationship for ponds not subject to routine algaecide treatments Am mount of Algae in Pon nd Chlorophy yll ( g L 1 ) y = 0.4x 1.02 r 2 = 0.65 Avg. values for: Magnolia Cherry Dogwood 10.0 Floral Total Phosphorus ( g L 1 )

10 Total Phosphorus is a strong predictor of algal abundance (as measured by Chlorophyll concentrations) Relationship does not significantly change for ponds treated with algaecide Am mount of Algae in Pon nd Chlorophy yll ( g L 1 ) y = 0.4x 1.02 r 2 = 0.65 y = 0.5x 0.85 r 2 = 0.53 Untreated ponds Treated ponds Total Phosphorus ( g L 1 )

11 Total suspended sediment concentrations among ponds: Sediments L 1 ) uspended S (mg Su No develop. Low Medium High max mean min TSS that t is organic (%) = Cherry 15 = Dogwood 16 = Magnolia 17 = Floral

12 Total suspended sediment concentrations: Upstream sites vs. Dogwood Winter Spring TSS (mg/ L) DF GB ML Dog Wood TSS (mg/l L) No da ata DF GB ML Dog Wood Fall Summer TSS (m mg/l) TSS (m mg/l) DF GB ML Dog Wood 0 DF GB ML Dog Wood

13 Questions? Contact Info: Erik Smith USC Baruch Marine Laboratory

14 Turbidity and rainfall Summer 13: Turbidity and Rainfall - Summer Turbidity (N NTU) Rainfall (m mm) /03 06/17 07/01 07/15 07/29 08/12 08/26 DateTime

15 Forms of Total Nitrogen and Phosphorus: Averages for Surfside Beach Ponds % TN as Dissolved % TP as Dissolved % TN Dissolved as Inorganic % TP Dissolved as Inorganic Cher rry Dogwoo od Magno olia Flo ral Cher rry Dogwoo od Magno olia Flo ral