Research


Field trial results:

Analysis of bloom biomass

The autotrophic biomass at site A1 declined from a maximum of 45% cover following  the installation of the filtration unit on June 24, 2014. This decline continued until July 31, 2014,  when the biomass reached a season minimum of 15%. Biomass increased again after this and  continued to fluctuate between 20 and 45% cover for the remainder of the season. A similar  fluctuating pattern of percent cover was observed in season 2, between a minimum of 0% cover  and a maximum of 25% cover. Site A2’s biomass rapidly declined from 100% initially to 0%  during the three week period following filter installation on July 8, 2014. Following this decline,  the percent cover by autotrophic biomass did not exceed 20% for the remainder of the first  sampling season. Blooms re­appeared shortly after the beginning of the second sampling season,
but did not exceed 15% surface cover for the remainder of the observation period. Site A3’s  biomass gradually declined during the first sampling season at a rate consistent with normal  growth patterns for the site, according to the property owner. Bloom biomass began to increase  gradually when the pond thawed in March of 2015 and did not exceed 75% cover by the end of  the observation period (Figure 3.3).

percent cover

Figure 3.3: ​  Percent of water surface covered with floating autotrophic biomass at primary  testing sites, June 2014­-July 2015.

The blooms at Site A1 displayed the lowest species richness, with only ​Spirogyra sp.  observed during the entire course of the experimental period. Site A2’s floating biomass was  initially dominated by ​Lemna  ​ sp​ . ​ , but following the decline in biomass in August 2014 ​Spirogyra  sp.  ​ also appeared in the pond. Site A3 displayed the highest species richness with four species  observed during the experimental period. Highest species richness at this site was observed  during the second sampling season, when ​P. crispus ​  appeared in the pond.

Table 3.3: Initial measurements of water chemistry parameters for primary field trial test sites

Site

Measurement Period Nitrate (ppm) Phosphate (ppm) Ammonia (ppm)

pH

A1

June 4-­24 2014 0-­10 0-­1 0-­0.25

8.1-­9.4

A2

July 8-­15 2014 0-­10 2-­3 0

7.6-­8.7

A3

July 17-­24 2014 0-­10 2­-8 (max) 0-­0.25

8.3-­9.0

 

Nitrate measurements at all three primary testing sites fluctuated between 1­8 ppm throughout the first sampling season. Site A1’s nitrate levels initially fell from 8 ppm to 1.2 ppm during August 2014. Dissolved nitrate levels remained below 4 ppm until October 2014. Site A2’s initial nitrate measurements were lower than those at Site A1, but followed an overall similar trend to that observed at Site A1 during the first sampling period. Site A3 initially had the lowest nitrate concentration at 4 ppm, which remained consistent for the first two weeks of August 2014. Nitrate levels at this site rapidly increased to 8 ppm in late August before falling again in September 2014; nitrate measurements at this site during the remainder of the sampling period followed a similar trend to those observed at Sites A1 and A2. At the beginning of the sampling season, dissolved nitrate levels at all three primary sites were initially between 5 and 10 ppm. Nitrate measurements at all three sites followed similar trends in this season, gradually declining at a similar rate until the end of the second sampling period. (Figures 3.9 and 3.10).

Dissolved nutrient concentration analysis

The baseline measurements of nitrate at each of the three test sites was between 0 and 10 ppm. Dissolved phosphate levels were highest at Site A3, with levels on the first day of observation exceeding the maximum value readable by the wide­range kits of 8 ppm. This level fell to 2 ppm the following week, so it was deemed low enough to not require dilution prior to testing with the more accurate Hach Kits. Ammonia levels at Sites 1 and 3 were detectable with levels between 0 and 0.25 consistent through their baseline measurement periods (Table 3.3).

nitrate con1

Figure 3.9: Dissolved nitrate concentration at primary testing sites, August-November 2014.

 nitrate con2

 



issolved nitrate concentration at primary testing sites, March-July 2015.

 

Dissolved phosphate concentrations at Sites A1 and A2 were initially 0.5 and 0.75 ppm. respectively. Site A1’s dissolved phosphate concentration fell gradually during August 2014 and remained below 0.25 for the remainder of the sampling season. Phosphate levels initially rose at Site A2 to a high of 1.6 ppm in mid­August before beginning to decline for the remainder of the month; concentrations proceeded to remain below 0.25 ppm until the end of November 2014. Site A3 yielded consistently higher dissolved phosphate measurements than those observed at the other primary sites, with measurements increasing rapidly from a low initial concentration of 0.25 ppm. Concentrations peaked at the maximum possible reading for the Hach phosphate kits of 3 ppm in August and September and did not decline until late September.

Phosphate levels at the beginning of the second sampling season were initially much lower than those observed during the first, with initial values below 0.5 ppm at all three sites. Concentrations declined to approximately 0 ppm between April and the first two weeks of July 2015. In late July, phosphate levels began to rise again just before the conclusion of sampling (Figures 3.11 and 3.12).

 

phos concen

Figure 3.11: Dissolved phosphate concentration at primary testing sites, August-November 2014.

 

phos concen 2

Figure 3.12: Mean dissolved phosphate concentration at primary testing sites, March-July 2015.

 

Dissolved ammonia concentrations in the first sampling season followed a similar distribution to that of phosphate at each site, with measurements at Sites A1 and A2 in August that steadily declined and remained below 0.2 ppm until November 2014. Site A3’s ammonia levels initially followed this trend, before rapidly increasing in September 2014 to the maximum value of 0.8 ppm measurable by the Hach ammonia kit. At the beginning of the second season, measurements of dissolved ammonia were initially much lower than those from the first, with no site observed to have a concentration higher than 0.08 ppm in the initial measurement. The ammonia concentration proceeded to rise and fall periodically at each site with no obvious trends; the highest measurement of the second sampling season was 0.19 ppm observed at site A2 in June 2015. Excluding this peak, ammonia levels at all three sites did not exceed 0.12 ppm for the entirety of the second sampling season (Figures 3.12 and 3.13).

ammon con1

Figure 3.13: Dissolved ammonia concentration at primary testing sites, August-November 2014.

ammon con2

Figure 3.14: Mean dissolved ammonia concentration at primary testing sites, March-July 2015.

 

Table 2.2: Overview of Site A1

Pond Type Artificial
Water source Groundwater, via pump
Surface Area 3365 m​2
Anthropogenic nutrient sources Residential and agricultural fertilizer runoff, ammonia from groundwater
Blooming autotrophs present Spirogyra ​sp.
Previous bloom treatments attempted Algicide, physical removal
Client goals for treatment 100% reduction in bloom biomass

 

stie of filter

Figure 2.4: Historic aerial photography of Site A1. A) 2006, prior to construction of the pond. B) 2008, housing and pond construction underway. C) 2009, construction complete, pond being filled. D) 2013, pond fully filled to current extent. Images from Google Earth.

Site A1 is an artificial pond located in Rush, NY. It was produced via excavation of part of an agricultural field between 2006 and 2008 and filled using an electronic groundwater pumping system. The pump continues to be used to regulate the water level, which varies from no more than 1 m in most of the pond to a maximum depth of 8 m near its center. The surrounding area is of mixed residential and agricultural use (Table 2.2, Figures 2.4 and 2.5)

 

site 2

Figure 2.5: Photoset of Site A1 taken on June 16, 2014. A) East side of pond, viewed from a hill to the west of the site. B) Macroalgae mats on the south side of the pond. C) East side of pond, including filter construction site. D) Closer view of macroalgae mats near the construction site.

 

pic1

Figure 3.4: Biodiversity of floating autotrophic biomass at Site A1, June 2014-­July 2015.

Table 2.3: Overview of Site A2.

Pond Type Natural
Water source Spring
Surface Area 1221 m​2
Anthropogenic nutrient sources Runoff from veterinary practice’s lawn, waste from resident goose and duck populations, fecal material in runoff from veterinary horse stables
Blooming autotrophs present Lemna ​sp.
Previous bloom treatments attempted Fountain aeration, physical removal
Client goals for treatment Reduction in bloom biomass without use of supplemental chemical treatments

pic2

Figure 2.6: Photoset of site A2 taken on July 17, 2014. A) View of the pond facing north from south bank. B) Dense mats of ​Lemna sp.​ collecting around the southern edge of the pond.

Site A2 is a natural spring­fed pond located in Mendon, NY on residential property between the pond owner’s home and a veterinary practice on the adjacent property. The pond is approximately circular with a maximum depth of approximately 3 m. With the exception of the nearby buildings and a mowed area along the south shore of the pond, much of this site’s surroundings are undeveloped forest and wetland habitat (Table 2.3, Figures 2.6 and 2.7).

pic3

Figure 3.6: Clear pond surface at Site A2 following decline of ​Lemna ​sp. blooms, July 29, 2014.

 

pic4

Figure 3.5: Biodiversity of floating autotrophic biomass at Site A2, July 2014­-July 2015.

Site A3 is one part of a two pond system located in Greece, NY; the pond that makes up Site A3 is the eastern pond of the pair. The system is located on the edge of a residential neighborhood near a forested area and a small creek. It was constructed in 2002 to act as stormwater retention and sediment settlement sites during the construction of the neighborhood. The ponds and their surroundings were eventually converted into the backyards of the last three houses built in the neighborhood; they are currently jointly maintained by the owners of these properties. Due to their original purpose as stormwater retention ponds, the depth of the ponds varies from 1­2 m, according to seasonal precipitation and runoff. During especially heavy precipitation and snowmelt, the water level of the ponds can rise sufficiently to combine them into a single pond. These events have caused the narrow strip of land between the two ponds to gradually erode, such that the ponds may eventually combine into a single system (Table 2.4, Figures 2.8­2.10).

Table 2.4: Overview of Site A3.

Pond Type Artificial
Water source Stormwater drainage
Surface Area 844 m​2
Anthropogenic nutrient sources Residential runoff in stormwater drainage
Blooming autotrophs present Wolffia​ sp., ​Lemna​ sp.
Previous bloom treatment attempted Fountain aeration
Client goals for treatment 100% reduction in bloom biomass, reduction in organic sludge present in the pond, reduction in sulfuric smell of pond

 

pic5

Figure 2.9: Photoset of site A3 taken on July 25, 2014. A) Experimental pond at site A3, from a hill north of the pond. B) View of the two­pond system that contains the experimental site, from the north shore of the treated (eastern) pond. C) View of the experimental pond at site A3, from the land bridge that separates the two ponds in the system. D) Outflow of Site A3, from a hill north of the pond.

 Dissolved nutrient concentration analysis

The baseline measurements of nitrate at each of the three test sites was between 0 and 10 ppm. Dissolved phosphate levels were highest at Site A3, with levels on the first day of observation exceeding the maximum value readable by the wide­range kits of 8 ppm. This level fell to 2 ppm the following week, so it was deemed low enough to not require dilution prior to testing with the more accurate Hach Kits. Ammonia levels at Sites 1 and 3 were detectable with levels between 0 and 0.25 consistent through their baseline measurement periods (Table 3.3).

pic6

Figure 3.8: Autotroph blooms at Site A3 during the second sampling season. (A) ​P. crispus blooms at Site A3 on May 15, 2015. (B) Diverse autotroph bloom at Site A3, July 10, 2015.

pic7

Figure 3.7: Biodiversity of floating autotrophic biomass at Site A3, July 2014­-July 2015.

Site B1 is a natural pond located in Delhi, NY on a mountain property. It is an oblong circular pond with a maximum depth of approximately 1 m. An underground spring supplies water to the pond as well as fresh drinking water for a guest house adjacent to the pond. It is one of a series of five small ponds on the mountainside that are maintained by the property owner (Table 2.5, Figures 2.11 and 2.12).

Table 2.5: Overview of Site B1

Pond Type Natural
Water source Spring
Surface Area 382 m​2
Anthropogenic nutrient sources Runoff from a duck pond located uphill, waste from resident duck population, nearby septic tank
Blooming autotrophs present Lemna​ sp.
Previous bloom treatment attempted Physical removal
Client goals for treatment 100% reduction in bloom biomass

The client at Site B1 reported no visible changes in the ​Lemna ​sp​.​ biomass in their pond following the filter installation at Site B1. NPS shipped an additional 19 L of suspended Chlorella ​sp​.​ culture to add to the system, but the addition appeared to have no effect on the Lemna ​sp. The bloom continued to cover 100% of the pond surface until it began to decline in mid­October 2014; the client reported that this pattern of decline was typical of the site in previous seasons prior to the installation of the filter unit. The ​Lemna​ sp. bloom returned at the start of the second observation season in March 2015 and continued to persist through July 2015 with 100% surface cover.

pic8

Figure 2.11: Aerial photograph of Site B1 from May 28, 2015. Image from Google Earth.

pic9

Figure 2.12: Photoset of Site B1 taken on July 7, 2014. A) East shore of the pond, viewed from the north. B) Western side of the pond, viewed from the north.

Site B2 is an artificial pond located in Perry, NY on a rural property. It was formed via excavation and filled using groundwater pumped from a nearby well to a maximum depth of approximately 3 m. The area around the pond is a forested zone of the owner’s property located between two agricultural fields. A cow barn was once located to the south of the site as well, but it has since been retired to convert the barn area into a residential area with a house (Table 2.6, Figures 2.13 and 2.14).

Table 2.6: Overview of Site B2

Pond Type Artificial
Water source Groundwater, via pump
Surface Area 2321 m​2
Anthropogenic nutrient sources Runoff from agricultural fields
Blooming autotrophs present Lemna​ sp.
Previous bloom treatment attempted Physical removal
Client goals for treatment Sufficient reduction in bloom biomass to use the pond for recreational activities

 

pic10

Figure 2.13: Aerial photograph of site B2 from May 9, 2011. Image from Google Earth.

Lemna ​sp​.​ biomass gradually declined in density in the weeks following the filter installation at Site B2. When NPS visited the site for maintenance on October 14, 2014, the duckweed biomass had declined to cover less than 30% of the pond surface. Patches of Spirogyra sp. ​were also observed during this visit. During the second observation season, Site B2 was visited on a monthly basis. ​Lemna ​sp​.​ replaced by ​Spirogyra ​sp​.​ as the dominant floating autotroph in the pond system. The ​Spirogyra ​sp​. ​biomass grew to cover approximately 40% of the pond’s surface by June 2015 and did not increase or decrease in extent for the remainder of the experimental period.

Site B3 is a natural pond located in Watkin’s Glen, NY on a property situated atop a mountain. It is a shallow L­shaped pond with a and a maximum depth of approximately 0.5 m. Due to the remote location of the property, the client relies on the pond as a source of drinking water (Table 2.7, Figures 2.15 and 2.16).

Table 2.6: Overview of Site B3

Pond Type Natural
Water source Spring
Surface Area 8718 m​2
Anthropogenic nutrient sources Residential runoff, nearby septic tank
Blooming autotrophs present Lemna​ sp.
Previous bloom treatment attempted Herbicide
Client goals for treatment Reduction in bloom biomass to prevent clogging of drinking water intake, sufficient bloom biomass reduction to reduce the need for herbicide treatments

NPS visited Site B3 two weeks following the installation of the filter at the site and observed patches of clear water appearing in the ​Lemna sp. ​biomass near the filtration unit outflow and drinking water intake. These patches were the only areas of the ​Lemna sp.​ biomass to decline prior to the usual seasonal decline in November 2014. At the start of the second observation season on March 2015, NPS visited the site for maintenance and discovered that the Lemna sp.​ had been replaced by ​M. spicatum​ (watermilfoil) as the dominant floating autotroph in the pond; the ​M. spicatum​ was covering 80% of the pond at the time of this visit. The ​M. spicatum ​biomass gradually died off in the following months and was replaced by ​Lemna ​sp​. once again, with only small areas surrounding the filter outflow remaining free of bloom biomass.

pic11

Figure 2.16: Aerial photograph of Site B3 from May 13, 2013. The client’s home is located in the residential area northwest of the pond.

pic12

Figure 2.15: Photograph of Site B3 on July 7, 2015, from western shore looking south.