2.4. Algal Blooms

2.4.1. Description and Significance

2.4.1.1. Blooms from microscopic algae

Phytoplankton (microscopic algae), including cyanobacteria (also called blue-green algae) photosynthesize and serve as the base of the food chain in lakes, rivers, streams, estuaries, and oceans.  Some species thrive in salt water, some in fresh water, and some tolerate wide ranges of salinity. Under certain conditions of nutrients, light, salinity and flow, these organisms can propagate rapidly and result in very high concentrations of the algae, creating what is called a “bloom,” which can have significant impacts on the local ecology of a river or lake (Figure 2.20).

Figure 2.20 Algae Blooms from 2013, 2016, and 2019. A. Ariel view of Doctors Lake (note the boat towards top of photo for scale). B. Pirates Cove with ducks. C-D. St. Johns River at East Palatka. For C, note the interface between the highly concentrated bloom on the right and the more natural looking tannic water on the left.  E. Lake George. F-G. Microscopic views of (F) Aphanizomenon and (G) Microcystis, Dolichospermum, and Aphanizomenon. Photos by (A) Gerry Pinto, (B) Andy Ouellette, and C-G from (TheScienceOf 2019).
Figure 2.20 Algae Blooms from 2013, 2016, and 2019. A. Ariel view of Doctors Lake (note the boat towards top of photo for scale). B. Pirates Cove with ducks. C-D. St. Johns River at East Palatka. For C, note the interface between the highly concentrated bloom on the right and the more natural looking tannic water on the left. E. Lake George. F-G. Microscopic views of (F) Aphanizomenon and (G) Microcystis, Dolichospermum, and Aphanizomenon. Photos by (A) Gerry Pinto, (B) Andy Ouellette, and C-G from (TheScienceOf 2019).

2.4.1.2. Types of impacts

Sight and smell – Algal blooms are often nuisances because of the odor, green water, and unsightliness of algal scum. However, the potential impacts go well beyond being a nuisance in several ways:

Decreased oxygen – Blooms can result in decreased oxygen levels in the water in two ways that are both based on respiration, which is a cellular process that consumes oxygen.  1) At night, when the algae respire, they can consume large amounts of dissolved oxygen. 2)  When algae cells die in large numbers (bloom decay), other microorganisms in the water respire at high rates while consuming the large amount of dead algae material.  Thus, when algal blooms die, many more microbes thrive, and can result in significant, rapid decreases of oxygen in the water column, which can stress many forms of aquatic life, and can result in fish kills.

Reduced sunlight – Blooms block sunlight from reaching the native submerged aquatic vegetation, thus preventing the plants from photosynthesize and grow, and live. Since submerged aquatic vegetation is important habitat for other organisms, this can start a cascade of ecosystem-disrupting events. See section 4.1 Submerged Aquatic Vegetation.

Toxins – Some cyanobacteria species produce toxins (cyanotoxins) that can reach high levels in a bloom, potentially creating public health problems and causing widespread deaths of fish and other aquatic organisms. Microcystins/nodularins have been detected in dolphins stranded in the LSJR and on the coast (Brown et al. 2018).

2.4.1.3. Toxins in freshwater harmful algal blooms

Cyanobacteria produce three broad classes of toxins known as hepatotoxins (microcystins, nodularin, cylindrospermopsins), neurotoxins (anatoxins, saxitoxins), and dermatotoxins (aplysiatoxins, lyngbyatoxin-a) that affect the liver, nerves, and skin, respectively, as well as cause general irritation (Chorus and Bartram 1999, Sivonen and Jones 1999; Williams et al. 2007; Burns Jr 2008).  Swimmers and anglers have complained of rashes after coming into contact with blooms (Steidinger et al. 1973).  As cyanobacteria concentrations increase, so does the potential for people to ingest toxins at levels that can cause adverse effects. Scums produced by some species such as Microcystis and Anabaena are particularly hazardous. They contain high levels of toxin, so it is important for the public and their pets to avoid exposure to them (Chorus and Bartram 1999). 

Microcystins and Cylindrospermopsins

Found in some blooms in the St. Johns River and its tributaries, microcystins and cylindrospermopsins are both liver and kidney toxins that can also cause headache, vomiting, and bloody diarrhea (EPA 2019b). They are the only cyanotoxins that the EPA has provided guidelines for.

    • Drinking water
      For drinking water, the EPA has issued informal health advisory guidelines for school aged children and adults of 1.6 mg/L for microcystins and 3.0 mg/L for cylindrospermopsin (EPA 2015a).  The World Health Organization (WHO) has set a drinking water “provisional consumption” limit of 1 mg/L for microcystin-LR (Chorus and Bartram 1999). Since the St. Johns River is not utilized for drinking water, the guidelines most relevant are those for recreational waters. 
    • Recreational waters
      In May 2019, the EPA published recommendations for national water quality criteria for microcystins and cylindrospermopsin with the goal of protecting swimmers and others engaged in recreational activities in natural waters (EPA 2019a; EPA 2019c). The swimming advisory levels, which are not to be exceeded on any day, are 8 ug/L for microcystins, and 15 ug/L for cylindrospermopsins. If a recreational water body does exceed either of these thresholds, then EPA recommends that a swimming advisory be issued.  The recommended criteria for impairment for other forms of water recreation are based on 10-day assessment periods across the recreational season.  If the waterbody exceeds the recommended criteria during three 10-day assessment periods, then that waterbody can be considered “not supporting recreational use.” While Florida has not adopted any guidance values for triggering waterbody closure or public health advisories, 21 U.S. states have created Guidance and Action levels for cyanotoxins, and these vary considerably (EPA 2017).

The WHO considers 10-20 µg/L microcystin-LR to have a moderate probability of adverse health effects for a 132-pound adult that ingests 3.4 oz. contaminated water. A 30-pound child would need to ingest less than 1 ounce for the same risk (Chorus and Bartram 1999).

Anatoxins and Saxitoxins

These nerve toxins are found in some blooms of the St. Johns River and its tributaries and can cause numbness, tingling, incoherent speech, and respiratory failure (EPA 2014).  Saxitoxin is among the most potent nerve toxin known and anatoxins are particularly fast acting.

BMAA

Another cyanobacterial molecule that has gained notoriety is BMAA (β-N-methylamino-L-alanine). BMAA is considered a neurotoxin based on cell and animal model studies, studies finding correlations between it and degenerative neurological diseases such as Alzheimer’s disease, Parkinson disease and amyotrophic lateral sclerosis (ALS), the proximity of lakes to such diseases, and the recent finding that stranded dolphins from Massachusetts and Florida that had BMAA in their brain tissues also had characteristic markers of human neurodegenerative diseases (Davis et al. 2019).

However, there are disagreements within the scientific community regarding methodology as well as data interpretation of many of these studies. The hypothesis that BMAA causes neurodegenerative diseases is controversial.  This is an important topic because many types of cyanobacteria have been shown to produce BMAA (Cox et al. 2005), and St. Johns River blooms that are analyzed for cyanotoxins are not tested for BMAA.

BMAA has been shown to biomagnify in the foodweb, which is when an animal that eats something toxic accumulates the toxin, concentrating it in its tissues. In the Florida Bay, a location with ongoing cyanobacterial blooms, BMAA has been found in blue crab, oysters, shrimp, and some fish (Brand et al. 2010). 

2.4.1.4. Nutrients

High levels of nutrients lead to algae growth and eutrophication, causing the ecosystem to become unbalanced with increased loading of organic matter to the system as a result (NRC 2000). The St. Johns River and its tributaries are impacted by excess nutrients in runoff and wastewater (section 2.3). Nutrients, including nitrogen- and phosphorus-based chemicals contained in garden, lawn, and agricultural fertilizer, are common causes of impaired waters in the LSJR and are crucial contributors to freshwater algal blooms.  Sewage sludge, aka biosolids, has been used as fertilizer around the Middle and Upper St. Johns River basins, contributing to phosphorus pollution in the headwaters of the St. Johns River (see section 2.3.).  A map of the biosolids application sites can be found here (DEP 2019e).

Thus, when nutrient levels are high and other appropriate conditions exist, the possibility of harmful algal blooms increases. Cyanobacteria growth rates and species distributions in an ecosystem are highly dependent upon light, temperature, and salinity. As a consequence, proximity to the mouth of the river (due to salinity levels), temperature fluctuations, color of the water, and the presence of other phytoplankton all determine whether an algal bloom will occur and which species will predominate. The major blooms have been in the more freshwater regions.  Rainfall also influences HABs; periods of low flow during drought increase the likelihood of algal blooms in the freshwater reach (Phlips et al. 2007), while high flow and hurricane rain events increase the likelihood of less concentrated but more widespread blooms in the downstream, Jacksonville reach of the river (Hendrickson 2013).

Nutrients promoting algal blooms also come from leaking septic systems, livestock, industry and runoff during and after heavy rain events. However, interesting work by Piehler et al. 2009 indicates some types of cyanobacteria can themselves increase nitrogen in waterbodies. During nitrogen fixation, a biological process, atmospheric nitrogen is taken up and used for growth by some species. The nitrogen is ultimately released into the water in forms that are more usable by biota that cannot use atmospheric nitrogen.

The question often arises about whether harmful algal blooms occurred historically and whether current blooms are a natural occurrence. Burns has this to say (Burns Jr 2008):

“Although there is little doubt that the phenomenon of cyanobacterial blooms predates human development in Florida, the recent acceleration in population growth and associated changes to surrounding landscapes has contributed to the increased frequency, duration, and intensity of cyanobacterial blooms and precipitated public concern over their possible harmful effects to aquatic ecosystems and human health. Toxic cyanobacterial blooms in Florida waters represent a major threat to water quality, ecosystem stability, surface drinking water supplies, and public health.”

Interestingly, algal blooms may have increased after successful eradication efforts to control the highly invasive water hyacinth in the 1970s and 1980s. In the past, hyacinth shaded much of the water column and limited algal growth. Reduction in the water hyacinth may have contributed to the change from a floating aquatic plant system to an algal-dominated system in the LSJR (Moody 1970; Hendrickson 2006; Hendrickson 2008).

2.4.2. Cyanobacteria in Florida and the LSJR

Potentially toxic cyanobacteria that are known to bloom in Florida waters include Microcystis aeruginosa (Figure 2.20), Anabaena circinalis, Cylindrospermopsis raciborskii, Anabaena flos-aquae, Aphanizomenon flos-aquae, and Lyngbya wollei (Chapman and Schelske 1997; Williams et al. 2007; Steidinger et al. 1999; Burns Jr 2008; Abbott et al. 2009).

1999-2000 – Extensive statewide sampling by Florida biologists in 1999-2000 showed that 88 out of 167 samples, representing 75 individual waterbodies, were found to contain potentially toxic cyanobacteria (Williams et al. 2001; Burns Jr 2008). Most bloom-forming cyanobacteria genera were distributed throughout the state, but waterbodies, such as Lake Okeechobee, the LSJR, the Caloosahatchee River, Lake George, Crescent Lake, Doctors Lake, and the St. Lucie River (among others) were waterbodies that supported extensive cyanobacterial biomass. Seven genera of cyanobacteria were identified in the statewide samples, with Microcystis (43.1%), Cylindrospermopsis (39.5%), and Anabaena (28.7%) the most frequently observed, and in greatest concentrations (Williams et al. 2001; Burns Jr 2008). In the same 1999-2000 survey, 55% of the samples in the LSJR basin contained the genus Anabaena, 53.9% contained Cylindrospermopsis raciborskii, and 47.6% contained the genus Microcystis (Williams et al. 2001; Burns Jr 2008), though it should be noted that many other species reside in the LSJR.

Algal blooms are now a yearly occurrence in the LSJR and its tributaries. A few of the well documented major blooms include:

2005 – Major blooms in the LSJR affected areas north of Crescent City to Jacksonville and caused large spikes in cyanotoxins and fish die-offs. The primary species was Microcystis aeruginosa (Williams et al. 2006; Williams et al. 2007).

2010 – From mid‐May through June of 2010, cyanobacteria blooms grew in great abundance in the freshwater reaches of the LSJR, beginning with blooms of Aphanizomenon flos‐aquae, which until then had never been recorded as the dominant species in the LSJR. With an increase in river salinity due to extended periods of reverse flow, the Aphanizomenon bloom decayed and was replaced by Microcystis, Cylindrospermopsis, Anabaena, and Pseudoanabaena (FWC 2010). Large spikes of a microcystins were measured in late May and June and elevated levels of Cylindrospermopsis in mid‐July through September (Hendrickson 2011).  A massive fish kill along a 30 miles of the river occurred, which was followed by the deaths of 11 dolphins in the St. Johns River.  These dolphin deaths were declared a marine mammal unusual mortality event, and the cause of those deaths are unknown (Borkowski and Landsberg 2012).

2013 – In October, the St. Johns Riverkeeper reported that microcystin (a cyanotoxin) concentrations in two LSJR-associated samples were >2,000 µg/L.  These concentrations are >250 times the new EPA recommendations for recreational waters (EPA 2019a; EPA 2019c) and are at a level that the World Health Organization classifies as posing a very high probability of acute health effects from recreational exposure (Inclan 2013; Patterson 2013; St. Johns Riverkeeper 2013a; EPA 2016). One of the toxin-sampling sites was in Doctors Lake (see Figure 2.20), which feeds into the St. Johns River and the other was in the more estuarine region of the river (at Jacksonville University). While both of these samples had very high levels of toxins, the chlorophyll-a samples in the STORET database for Doctors Lake that same month were less than 40 µg/L, and none of the 2013 estuarine samples in the analyzed data set were >40 µg/L chlorophyll-a. Thus, there were blooms that are not evident from looking at the chlorophyll-a levels from the STORET database, which illustrates a limitation of the chlorophyll-a-based analysis in this report (below).

2019 – Reminiscent of 2010, a >70-mile stretch of the St. Johns River experienced visible cyanobacteria in the water column, including at various sites, Aphanizomenon flos‐aquae, Dolichospermum, Cuspidothrix, Planktothrix, Anbaaena, and Microcystis, with some areas having very high levels of cyanobacteria (TheScienceOf 2019). The liver toxins microcystins/nodularins and cylindrospermopsin, and the nerve toxin saxitoxin were found in multiple locations on multiple dates.  The saxitoxin levels were among the highest ever reported in the freshwater portion of the St. Johns River (SJRWMD 2019b). Levels of phosphorus from the headwater region to Orange Park were elevated compared to mean values, which could explain why Aphanizomenon flos‐aquae was dominant in many areas of this bloom, since this cyanobacterium can use nitrogen from the atmosphere instead of relying on nitrogen from the water, so phosphorus is the limiting nutrient for this species.  This bloom was first reported on April 10, which is particularly early in the year, and algal blooms and toxins are being reported through the summer (DEP 2019a). 

The FDEP recently created an interactive Algal Bloom Sampling Status Dashboard, which includes a map of algal bloom sampling results, such as types of cyanobacteria and concentrations of select toxins, an interface for reporting blooms, and frequently asked questions (Figure 2.21).

Figure 2.21 Algal Bloom Sampling Status Dashboard. Screenshot from (DEP 2019a).
Figure 2.21 Algal Bloom Sampling Status Dashboard. Screenshot from (DEP 2019a).

Identification and quantitation of cyanobacteria and their toxins in the LSJR can be difficult, expensive, and time-consuming, though in recent years, there has been an expansion of different methods and approaches (Williams et al. 2007; Burns Jr 2008). The most consistent and complete data that reflect phytoplankton growth over many years are measurements of chlorophyll-a. Chlorophyll-a is a light-harvesting pigment used by photosynthesizing organisms. Elevated phytoplankton concentrations, including cyanobacteria, are accompanied by elevated chlorophyll-a concentrations so chlorophyll-a is often used as an indicator for HABs.

2.4.3. Chlorophyll-a Thresholds and Data Analysis

Chlorophyll-a values are used to determine relative phytoplankton abundance. Each water body is unique with respect to flow, shape, and water chemistry, all which affect phytoplankton growth and therefore also chlorophyll-a levels (DEP 2013d). Because salinity is a critical factor in cyanobacteria growth, it is useful to examine chlorophyll-a in different river regions. The marine/estuarine reach discussed in this report extends from the mouth at WBID 2213A to WBID 2213H, and the freshwater region extends from WBID 2213I upstream to WBID 2213N at the confluence of the Ocklawaha River (See Figure 2.1 for map of WBIDs).

2.4.3.1. Criteria and threshold values

Streams with chlorophyll-a concentrations that are below 3.2 µg/L are biologically healthy; however, some types of streams are stable and healthy at higher levels of chlorophyll-a/L. Therefore, a number of DEP chlorophyll-a impairment thresholds exist for Florida waterways ranging from general criteria to site-specific criteria. For example, the impairment threshold for estuaries and open coastal waters is 11 µg chlorophyll-a/L (annual geometric mean) (DEP 2013d). However, the marine/estuarine reach of the LSJR has an even lower, more stringent, site-specific chlorophyll-a criterion of 5.4 µg/L for long-term (7-year) annual averages (DEP 2013h; DEP 2016a). Thus, 5.4 µg/L is the threshold criterion we utilize in this report for the marine/estuarine reach (which is most appropriately compared to 7-year annual averages). 

For freshwater, the general impairment threshold in Florida is 20 µg chlorophyll-a/L (not to be exceeded more than once in a three year period), based on annual geometric means (DEP 2013d; DEP 2016g). However, the DEP uses a criterion of 40 µg chlorophyll-a/L not to be exceeded more than 10% of the time (or for more than 40 days) for the chlorophyll-a threshold for the Lower St. Johns River Basin (Magley and Joyner 2008; DEP 2014a). For this River Report, both freshwater criteria are used – the general 20 µg/L annual geometric mean threshold is used for general assessment of the freshwater regions of the river, and 40 µg/L chlorophyll-a/L is used as a threshold of bloom status when discussing individual water segments (WBIDs).

In this River Report, the current status and time trends of chlorophyll-a are examined in different ways. Both the marine/estuarine and the freshwater regions are presented as annual chlorophyll-a averages for direct comparison between the two regions (Figure 2.22). The marine/estuarine data are then displayed as annual averages as well as 7-year annual averages and are compared to the 5.4 µg/L chlorophyll-a criteria (Figure 2.23B). The freshwater data are presented as annual geometric means for comparisons to the 20 µg/L chlorophyll-a threshold (Figure 2.23B). To show the spread of the data, including the high and low values, box-and-whisker plots are presented for both the marine/estuarine and freshwater regions (Figure 2.24).

2.4.3.2. Data acquisition and processing

Chlorophyll-a data were obtained from the DEP STOrage and RETrieval (STORET) and Watershed Information Network (WIN) online portals. WIN/ STORET is the statewide environmental data system containing water quality, biological, and physical data. Method 10200-H was used to analyze chlorophyll-a that was corrected for pheophytin, which is a form of degraded chlorophyll. Only stations in the mainstem or near the mainstem in major tributaries, such as the Ortega River and Julington Creek, were included. Data were reviewed for quality and data points were discarded when samples appeared analytically compromised (contaminated blanks, poor recovery, poor replication, etc.) or were missing important information. All samples with qualifier codes K, L, O, V, Y, or ?, which indicate different data quality issues, were eliminated. If a reported value was below the method detection limit (MDL), it was used even if flagged. One-half the MDL was used for samples reported as “nondetect.” In a small number of cases, the MDL was estimated by determining the MDL reported most frequently for other samples during the same year. When routine and integrated vertical samples were obtained at the same time, the integrated samples were used for analysis in this report.

2.4.4. Current Status and Trends

Based on annual averages, the freshwater regions have shown consistently higher concentrations of chlorophyll-a compared to the marine/estuarine regions (approximately two to seven times higher per year; Figure 2.22A), which is not unexpected since the phytoplankton that cause algal blooms in the St. Johns River are freshwater species and there are higher nutrient concentrations upriver.  This is further illustrated using aggregated WBID data, which shows the decrease in chlorophyll-a concentrations when moving from the most upstream freshwater WBID N towards the end of the St. Johns River at the Atlantic Ocean (WBID B) (Fig. 2.22B).

Figure 2.22 Annual averages of chlorophyll-a concentrations in the freshwater section and the marine/estuarine reach for 1997-2018.  Blue denotes marine/estuarine data and green denotes freshwater data.  A. Annual averages per year.  B. Averages of annual averages for each WBID. For each WBID, the annual averages for all years were averaged, and the error bars represent the standard deviations for each average of averages. WBIDs A, C and F are not included due to lack of data from 2016 to present, 2014 to present, and 2009 to present, respectively.
Figure 2.22 Annual averages of chlorophyll-a concentrations in the freshwater section and the marine/estuarine reach for 1997-2018. Blue denotes marine/estuarine data and green denotes freshwater data. A. Annual averages per year. B. Averages of annual averages for each WBID. For each WBID, the annual averages for all years were averaged, and the error bars represent the standard deviations for each average of averages. WBIDs A, C and F are not included due to lack of data from 2016 to present, 2014 to present, and 2009 to present, respectively.

To assess the chlorophyll-a levels in the marine reach, the annual averages are compared to the impairment criterion value of 5.4 µg/L (Figure 2.23B). The annual average data (blue diamonds) show chlorophyll-a concentrations  below the 5.4 µg/L threshold the past five years, and the 7-year average (black squares) has reached the 5.4 µg/L threshold in 2018, thus, these data show the marine reach meeting the chlorophyll-a criterion, which is promising. However, the lack of recent data for WBIDs A, C, and F constrain the overall interpretation. 

Figure 2.23 Annual chlorophyll-a concentrations compared to threshold values in the Lower St. Johns River mainstem. A. Annual geometric means in the freshwater section; and B. Annual and 7-year averages in the marine/estuarine reach. The dashed lines represent the chlorophyll-a thresholds; 5.4 µg/L for the marine and estuarine portions (State criterion), and 20 µg/L for the freshwater portions (River Report threshold).
Figure 2.23 Annual chlorophyll-a concentrations compared to threshold values in the Lower St. Johns River mainstem. A. Annual geometric means in the freshwater section; and B. Annual and 7-year averages in the marine/estuarine reach. The dashed lines represent the chlorophyll-a thresholds; 5.4 µg/L for the marine and estuarine portions (State criterion), and 20 µg/L for the freshwater portions (River Report threshold).

The freshwater annual geometric means for the seven most recent years are below the 20 µg/L threshold that this River Report uses for comparison (Figure 2.23A), which looks promising regarding reduction in freshwater algae growth and blooms from the sites collected at those times.  While Figures 2.22 and 2.23 are useful for trends and comparison to threshold values, they do a relatively poor job of representing the data sets per year.  Furthermore, geometric means tend to be lower than arithmetic means (compare Figure 2.22A to 2.23A). Therefore, box and whisker plots are presented to show the spread of the data in 25% increments as well as the median value, the highest values, and the lowest values (Figure 2.24; see circled inset). The highest freshwater values for the past seven years and the highest marine values for the past five years are the lowest high-values for the 22 years analyzed for each segment of the river (Figure 2.24 A and B, respectively).

Figure 2.24 Yearly chlorophyll-a concentrations with an emphasis on the spread of the data in the Lower St. Johns River mainstem for freshwater and marine/estuarine regions. The dashed red lines represent the chlorophyll-a thresholds. Data are presented as box-and-whiskers plots that show the data compiled into 25% intervals (inset).  The median value is the number where 50% of the data is above, and 50% of the data is below, and is indicated by the horizontal line in the center of the boxes.  Whiskers indicate the ranges of the highest and lowest 25% of the data, including the maximum and minimum values. Note logarithmic scale on y-axis.
Figure 2.24 Yearly chlorophyll-a concentrations with an emphasis on the spread of the data in the Lower St. Johns River mainstem for freshwater and marine/estuarine regions. The dashed red lines represent the chlorophyll-a thresholds. Data are presented as box-and-whiskers plots that show the data compiled into 25% intervals (inset). The median value is the number where 50% of the data is above, and 50% of the data is below, and is indicated by the horizontal line in the center of the boxes. Whiskers indicate the ranges of the highest and lowest 25% of the data, including the maximum and minimum values. Note logarithmic scale on y-axis.

2.4.5. Limitations

While the trend of lower chlorophyll-a concentrations from these samples across the years is encouraging, there are multiple limitations to the chlorophyll data (below), and the aggregation of the data for the large freshwater region has its limitations.  The LSJR is large, and so the small number of samples from limited locations in the river can reveal only so much, and there are still sections of this region (WBIDs; Figure 2.1) that are experiencing elevated chlorophyll-a levels.  Therefore, it is worth discussing WBID-specific information instead of strictly the aggregated data from the freshwater portion.  First, Figure 2.22B illustrates historic differences between the WBIDs, including among the freshwater WBIDs, with K-N noticeably higher than H-J.  Second, the points below illustrate more in-depth localized analysis of data for freshwater WBIDs.  These specific examples are intended to highlight some issues with data limitations as well as how specific regions of the freshwater portion endure particularly elevated chlorophyll-a levels, including levels which indicate blooms, including toxic blooms.

A) Recent data for each WBID is from one sample per month maximum, and not all months are represented for all WBIDs, including warmer months, which are more prone to blooms.   As a lack-of data example, WBID K had only three data points in the database for 2016, with a high value of 43 µg/L and geometric average of 22 µg/L.  In 2017, the data do not go past July.  From January – July, the high was 40 µg/L and the geometric average was 22 µg/L.  Having no data past July, during months blooms occur, is problematic for analysis. In 2018, the high was 53 µg/L, with no data available for June or July.

B) For 2012 and 2013, 5 of the 6 annual chlorophyll-a geometric means of freshwater WBIDs K, M, and N were above the 20 µg/L threshold.

C) For 2016, 8 of 22 samples from WBID N exceeded the site-specific chlorophyll-a criterion of 40 µg/L. These 8 samples spanned May to September, and include all 5 samples from July 13 to September 7, indicating a prolonged bloom.  Furthermore, the annual geometric means for this WBID ranged from 20.4-22.7 µg/L for 2012, 2013, and 2016, slightly over the 20 µg/L threshold for each of those years.  Therefore, WBID N exceeds the two different thresholds used in this River Report, including the state criteria.

D) The DEP has analyzed chlorophyll-a data from WBID K (Racy Point), which is a location that it considers to be a “worst-case WBID,” along with nearby Dancy Point (WBID L), and reported the number of days per year that Racy Point experienced a nuisance bloom (designated as chlorophyll-a values >40 µg/L). That analysis reports a trend of decreasing days per year (from 1995-2013) when Racy Point is >40 µg/L chlorophyll-a (DEP 2014a). While that analysis shows a decrease in the longevity of these blooms at this location, it still has recurring blooms.

In that analysis, chlorophyll-a values derived from continuous measurements at Dancy Point (Using USGS data, which are not deposited in the DEP STORET database) are compared to the values of chlorophyll-a measured from discrete samples at Racy Point (that are in the DEP STORET database). That analysis shows many days during spring 2013 when Dancy Point (WBID L) was above the 40 µg/L threshold according to the continuous measurements, but these types of data are not in the DEP STORET database. This lack of WIBD L data for 2013 is an example of limitations of Figures 2.22-2.24, and illustrates the problem of our analysis missing key algal bloom events in the river.

The above discussion demonstrates that the chlorophyll-a datasets we are using have limitations in that there are recorded instances of high chlorophyll-a levels that are not captured in our analysis, and there are toxic algal bloom events that have occurred that are not represented in the chlorophyll dataset. Furthermore, the river sampling locations for chlorophyll-a are largely in the middle of the river channel, and it is known that Microcystis blooms can be concentrated along the shore and in coves due to the ability of these cyanobacteria to float and be pushed by the wind. Thus, some wind-driven blooms or elevated chlorophyll-a levels are missed with routine sampling at fixed locations. Sampling protocols can also miss more dense algae at the surface of the water.  Finally, the geographical region analyzed also affects the interpretation. While the data here were grouped as either freshwater or marine/estuarine for the main analysis (Figures 2.22-2.23), there are individual locations in the river and its tributaries that are particularly problematic regarding algal blooms.

2.4.6. Summary and Future Outlook

The St. Johns River and its tributaries continue to experience cyanobacterial blooms on a yearly basis.  The chlorophyll data analyzed above show recent years lower than the threshold values, and appear to be in compliance with state regulations, however, the data set is limited in scope and misses bloom events.  The annual appearances of blooms (including toxic events) indicate significant impact from cyanobacteria.  Coupled with the extensive, early 2019 algal blooms in Lake George and the mainstem that included nerve toxins (saxitoxin) and liver toxins (microcystins and cylindrospermopsins), and the increased mean phosphorus levels of 2018 compared to 2003-2017, the STATUS of the LSJR with respect to algal blooms is considered Unsatisfactory, and the TREND is Uncertain

Much of the outlook for algal blooms is closely tied to that for nutrients. Reduced nutrient loading in the LSJR may be lowering concentrations of some forms of nutrients in the mainstem (Section 2.3), and perhaps an overall accompanying reduction in algal concentrations is starting to be observed. However, more years of data coupled with the frequency and extent of blooms will be needed to understand whether this is a stable trend or a short-term phenomenon. Furthermore, the number of samples obtained from the database over the past few years is reduced compared to previous years, which makes trend analysis more complicated, particularly since algal blooms are being missed. And, even though substantial reductions of nutrients to the LSJR has occurred, approximately two thirds of the nutrients in the LSJR come from the middle basin so algal blooms in the LSJR are tied to the middle basin, which is tied to the upper basin (section 2.3, and COJ 2019b).  Thus, biosolids and other fertilizers used in the basins of the upper and middle St. Johns River impacts the LSJR (Rivers 2018).

The Jacksonville Waterways Commission recently convened a St. Johns River Algae Task Force, which developed seven recommendations that include continued nutrient reductions, increase public education, creation of a centralized statewide surveillance system, and reestablishing oyster reefs for improved water quality (COJ 2019b). A state level Blue-Green Algae Task Force has recently been created in response to the high profile, massive cyanobacterial blooms in Lake Okeechobee.  The mission is focused on Lake Okeechobee and its downstream tributaries, and the Everglades, and does not formally include the St. Johns River (DEP 2019f; DEP 2019b). 

In addition to the connectivity of the different basins of the St. Johns, the freshwater and marine/estuarine sections of the LSJR analyzed are large geographical areas. It is important to consider the complexity of the LSJR ecology and the difficulty in establishing healthy benchmarks and natural trends in a system with physical, chemical, and biological characteristics that naturally vary so widely in space and time.

2.4.7. Recommendations for Research

As discussed above, some bloom events are not represented in the FDEP WIN/STORET database, so our understanding of frequency, duration, and locations of blooms is not comprehensive.  Additional, extensive monitoring of chlorophyll-a and cyanotoxins, including BMAA, at locations known to have recurring blooms, combined with associated nutrient, temperature, and toxin data, could help form a clearer picture of these blooms and the extent to which they exist, how toxic they become, and determine drivers of bloom formation, such as nutrients and temperature.  Laboratory, mesocosm, and in situ studies that analyze growth rates, toxin production, and bloom collapse of HAB cyanobacteria isolated from the LSJR as a function of varied nutrients, salinity, and temperature are essential to understanding blooms of the LSJR.

 

Water Quality, Fisheries, Aquatic Life, & Contaminants