Anthropogenic sources of aluminum in aquatic systems include sludge from municipal water treatment plants, industrial discharge (e.g., pulp and paper mills), and fertilizer runoff (Moore 1991). Copper and zinc are two of the most widely used elements in the world and as such are common pollutants found in freshwater and marine ecosystems (Bielmyer-Fraser et al. 2017; Fig. 5.6). Copper enters aquatic systems through runoff from rivers adjacent to heavy metal mining areas (Bryan 1976); through sewage treatment discharge, industrial effluent, anti-fouling paints, refineries, as well as overflow from stormwater ponds (Guzman and Jimenez 1992; Jones 1997; Mitchelmore et al. 2003). Copper is also a constituent of several pesticides commonly used to control algae. Zinc is a major component of brass, bronze, rubber, and paint and is introduced into water systems via commercialized businesses (smelting, electroplating, fertilizers, wood preservatives, mining, etc.) and rainwater run-off (Eisler 1993). Although there are freshwater environments with only a few micrograms of zinc per liter, some industrialized areas may have problematic concentrations of over 1000 µg/L Zn (Alsop and Wood 2000). Along with copper and zinc, nickel-containing materials make major contributions to many aspects of modern life. The uses of nickel include applications in buildings and infrastructure such as stainless-steel production and electroplating; chemical production, such as production of fertilizers, pesticides and fungicides; energy supply, water treatment, and coin production (Nriagu 1980; Eisler 1988b; Hoang et al. 2004). The largest use of nickel alloys and a major use of copper and zinc are in corrosion prevention. Although these applications have provided many benefits, they have resulted in increased environmental concentrations, which may have significant impact on aquatic life (Pane et al. 2003; Hoang et al. 2004).  In the past, lead has also been used to a large extent in corrosion prevention, but legislation in the 1980s has limited the content of lead in paints, reduced the lead in gasoline, and eliminated the use of lead shot nationwide (Eisler 1988a). Current concerns about lead contamination in aquatic environments are mainly due to point-source discharges from mining, smelting, and refining processes, mostly for use in the production of batteries (Eisler 1988a; WHO 1995). Lead shot can also be problematic in some environments. Unsustainable disposal of sewage sludge may also be a cause of lead contamination in rivers (Shamuyarira and Gumbo 2014). Natural sources of lead such as erosion and atmospheric deposition from volcanoes and forest fires also contribute to the lead found in aquatic environments (WHO 1995). Elevated silver concentrations in aquatic animals occur near sewage outfalls, electroplating plants, mine waste sites, or areas where clouds have been seeded with silver iodide. Prior to 2010, the photographic industry was the major source of anthropogenic silver discharges in the United States (Eisler 1996); however, over the last decade the use of silver, as silver nanoparticles, has substantially increased, particularly for applications in catalysis, optics, electronics, biotechnology and bioengineering, water treatment, and silver-based consumer products. Vanadium has also been used in nanomaterials and in rust-resistant, high-speed tools, particularly in industrial and medical applications (USDHHS 2012). Additionally, vanadium may be released to the environment from oil refineries and power plants using vanadium-rich fuel oils and coal, as well as natural sources like volcanoes, marine aerosols, and continental dust (USDHHS 2012). Natural sources of selenium include weathering of sedimentary rocks and soils. Like many metals, selenium can be released into the environment via fossil fuel combustion, metal refining and smelting, and domestic wastewater (Moore 1991). Selenium is predominantly used in glass manufacturing, and significant emissions of selenium from glass furnaces are common (Scalet et al. 2006). Arsenic and many of its compounds are especially potent poisons, especially to insects, thereby making arsenic well suited for the preservation of wood, which has been its primary historical use. Chromated copper arsenate, also known as CCA or Tanalith, has been used worldwide in the treatment of wood; however, its use has been discontinued in several areas because studies have shown that arsenic can leach out of the wood into the soil, potentially causing harmful effects in animals and severe poisoning in humans (Rahman et al. 2004).

Once in aquatic systems, most waterborne metals exert toxicity by binding to and inhibiting enzymes on the gill or gill-like structure of aquatic animals (Bury et al. 2003; Bielmyer et al. 2006b). This leads to a disruption in ion and water balance in the organism and ultimately death, depending on the metal concentration and exposure time. In saltwater, fish drink water to maintain water balance and therefore, the intestine is another site for metal accumulation and ion disruption (Bielmyer et al. 2005b; Shyn et al. 2012). Ingestion of metal contaminated diets can also cause intestinal metal accumulation and potentially toxicity to the consumer (Bielmyer et al. 2005b; Bielmyer and Grosell 2011; Bielmyer et al. 2012b). Decreased respiration, decreased reproductive capacity, kidney failure, neurological effects, bone fragility, mutagenesis (genetic mutation), and other effects have been observed in aquatic biota after metal exposure.

Several water quality parameters can modify the toxicity of metals including: salinity, DO, dissolved organic carbon concentration (humic and fulvic substances), sulfide concentration, pH, water hardness and alkalinity, as well as other variables (Campbell 1995). The toxicity of metals may therefore vary in different parts of the LSJR, reflecting the changes in water chemistry (Ouyang et al. 2006) as well as the organisms that reside there. Seasonal changes as well as extreme weather events like hurricanes and storms may also substantially change water chemistry thereby influencing metal toxicity (Bielmyer-Fraser et al. 2020). Metal toxicological studies using organisms or water from the LSJR are scarce. Grosell et al. 2007 and Bielmyer et al. 2013 collected Fundulus heteroclitus (killifish) from the LSJR and used them in acute (96 h) toxicological studies in the laboratory to determine the influence of salinity on copper, zinc, nickel, and cadmium toxicity to the larvae. As salinity increased, toxicity generally decreased for the metals tested. In freshwater, significant mortality to larval killifish occurred after exposure to copper (Grosell et al. 2007), zinc (Bielmyer et al. 2012a), nickel (Bielmyer et al. 2013) and cadmium (Bielmyer-Fraser et al. 2018) at concentrations reported in the LSJR over the past five years (see section 2.7); however significant larval mortality was only observed after exposure to higher nickel concentrations than those found in the LSJR (Bielmyer et al. 2013). The presence of killifish is important in the LSJR because they are a common food source for many larger fish. Exposure to these metals for long time periods may cause deleterious effects, such as decreased growth and/or reproduction, in various species at even lower concentrations. Exposure to 50 µg/L for 21 days caused decreased growth in hybrid striped bass in freshwater; whereas, those exposed to the same concentration in saltwater did not suffer growth reduction (Bielmyer et al. 2006b). Generally, larval fish are more sensitive to metals than adults, and invertebrates can be even more sensitive than larval fish (Bielmyer et al. 2007). In water collected from Green Cove Springs, exposure to silver concentrations as low as 0.34 µg/L for the invertebrate crustacean, Ceriodaphnia dubia (common food sources for larval fish), and 6 µg/L for fathead minnows, respectively, caused 50% mortality to the organisms (Bielmyer et al. 2007). These silver concentrations have been reported to occur in parts of the LSJR.  Many zooplankton exposed to metals, particularly through their diets, have been shown to be very sensitive to metals (Bielmyer et al. 2006a; Jarvis et al. 2013) and to accumulate metals (Bielmyer et al. 2012b). Metal exposure to the lower trophic levels may impact higher-level consumers by decreasing food availability and/or by introducing metal exposure via the diet.  Sepúlveda et al. 2002 reported the accumulation of both metal and organic contaminants in the livers of Florida largemouth bass collected from four different locations in the LSJR: Welaka, Palatka, Green Cove, and Julington Creek.  The highest mean liver metal concentrations were found in bass from Julington Creek (silver, arsenic, chromium, copper, zinc) and Welaka (cadmium, mercury, lead, selenium, tin). The zinc concentrations accumulated in the liver of the fish from Julington Creek were similar to those observed in adult killifish after exposure to 75 µg/L Zn in the laboratory (Shyn et al. 2012). Lead can exist as an organometal and has a higher partition coefficient than the other metals discussed here; therefore, lead would be preferentially distributed in more hydrophobic compartments (Eisler 1988a).  Lead has been shown to exert toxic effects on a variety of aquatic organisms with sensitivity of some invertebrates as low as 4 µg/L (Grosell et al. 2006). Chronic lead toxicity in fish includes neurological and hematological dysfunctions (Davies et al. 1976; Hodson et al. 1978; Mager and Grosell 2011). Selenium mainly exerts toxicity by impairing reproduction and causing embryotoxicity and teratogenicity (Chapman et al. 2009; Chapman et al. 2010).

Recently, important aquatic plant species (submerged aquatic vegetation) in the LSJR have been shown to accumulate metals (Bielmyer-Fraser et al. 2022a), at levels that have been shown to exert toxic effects in laboratory studies (Bielmyer-Fraser et al. 2022b). These plants serve important ecological niches including serving as refugia for small fish, food sources for manatee and other organisms, nutrient cycling, and trapping sediment.

Total metal concentrations were used in this report, rather than the preferred dissolved metal concentrations, which are used in calculation of water quality criterion values. Total values were used because the dissolved metal concentrations were not reported to a large extent, and in many cases dissolved values only accounted for less than 5% of the total data reported. EPA methods 200.7, 200.8, and 206.2 were used to measure arsenic; EPA methods 200.7, 200.8, 213.2, and 6010B were used to measure cadmium; EPA methods 200.7, 200.8, 220.2, and 6010B were used to measure copper; EPA methods 200.7, 200.8, 249.2, and 6010B were used to measure nickel; EPA methods 200.7, 200.8, 272.2, and 6010B were used to measure silver; EPA method 200.8 was used to measure aluminum, EPA methods 200.7 and 200.8 were used to measure vanadium, and EPA methods 200.7, 200.8, and 6010B were used to measure zinc.

The metal data are compared to Florida ambient water quality standards with the noted exceptions below. The LSJR varies in salinity, with the mainstem predominantly freshwater and some of the tributaries ranging from fresh- to full strength seawater. Salinity may affect the toxicity of some metals to aquatic life therefore the EPA class III Water Quality Criterion (WQC) values may be different for freshwater and marine water. Likewise, for freshwater, hardness, defined as the total concentration of the divalent cations calcium and magnesium, has also been shown to reduce the toxicity of the metals cadmium, copper, lead, nickel, and zinc; therefore, the freshwater criterion is based on an equation which incorporates the hardness of the water body. For the hardness-dependent metals in this analysis, an average hardness value of 100 mg CaCO₃/L was used for generating the freshwater criteria. For aluminum, a multiple linear regression (MLR) approach has been used to derive the WQC (MLR normalized to pH = 7, hardness = 100 mg/L, DOC = 1 mg/L; EPA 2017). Currently, no water quality guidelines have been generated for vanadium in fresh- or saltwater.  To date, only a few studies have focused on the toxicity of vanadium to aquatic organisms. The WQC for marine (haline; surface chloride concentration ≥ 1,500 mg/L) waters was used for all the metals, except for silver and vanadium, for which no marine water quality criterion has currently been adopted by the U.S.EPA. The current proposed WQC value for silver has been used. It must be pointed out that the freshwater and marine WQC are the same for some metals, like arsenic, for example. However, for other metals, like cadmium, the freshwater WQC is substantially different (0.27 mg/L at 100 mg/L hardness) from the marine criterion of 8.8 mg/L. Therefore, for river segments or water bodies that have no saltwater influence, the potential for environmental impacts of certain metals may vary.

The data set for metals in the water column is more robust in some years and missing in others, which contributes error in the data trend analyses. Each metal is discussed in turn below.

Median and mean aluminum values have been stable since 2016 in the LSJR (Figure 5.7; 5.8). Maximum aluminum values were above the calculated freshwater criterion value in the LSJR mainstem and tributaries during that time (Figure 5.7; 5.8).

Arsenic values have been stable in the tributaries and freshwater portion of the mainstem since 2005, and no arsenic values have exceeded WQC since 2009 (Figure 5.9; 5.10; 5.27A). Alternatively, arsenic mean and median concentrations have been increasing in the SW portion of the LSJR mainstem since 2005, with fluctuations of maximum concentrations (e.g., in 2016 and 2018; Figure 5.9) above the WQC of 50 µg/L. All arsenic concentrations were below the WQC and within acceptable limits from 2019 to 2022 (Figure 5.9; 5.10).

Like arsenic, cadmium median and mean values have increased since 2009, especially in the SW portion of the LSJR mainstem, although values did not exceed the WQC in saltwater (Figure 5.11; 5.12). Median and mean cadmium concentrations in the freshwater part of the LSJR have been relatively stable and within acceptable limits. However, since 2017, maximum cadmium values have exceeded the WQC in freshwater (with the assumed hardness value of 100 mg/L) (Figure 5.11; 5.12). Changes in salinity may affect cadmium toxicity, as well as the toxicity of the other metals (Shyn et al. 2012; Bielmyer et al. 2012b; Bielmyer et al. 2013; Bielmyer-Fraser et al. 2018). In general, metals are more toxic in freshwater; metal toxicity decreases with increasing salinity (Bielmyer and Grosell 2011). Cd exceedances in Doctors Lake have been reported (Figure 5.27B).

Copper was one of the more commonly found metals in the LSJR, based on this data set. In the freshwater LSJR mainstem, maximum copper values have fluctuated above WQC since 2005; however, mean and median values have been below WQC and stable since 2010 (Figure 5.13; 5.14). In the saltwater mainstem and tributaries of the LSJR, maximum copper values have exceeded WQC since 2005 and mean and median values have increased in the saltwater mainstem over the past five years (Figure 5.13; 5.14). Copper has been most problematic in the tributaries, where many exceedances have been documented (Figure 5.13; 5.14; 5.27C).

Mean and median lead values have been relatively stable in the freshwater mainstem areas and tributaries of the LSJR since 2005 (Figure 5.15; 5.16). In saltwater areas of the mainstem, however, lead has fluctuated with maximum values periodically exceeding WQC (e.g., 2006-2008; 2018; Figure 5.15; 5.16). In several tributaries, particularly Big Fishweir Creek, Doctors Lake, Moncrief Creek, and Strawberry Creek, lead concentrations exceeding both freshwater and saltwater criteria have been documented (Figure 5.27D).

Mean, median, and maximum nickel concentrations decreased from 2005 to 2009, and then increased until 2018 when concentrations leveled (Figure 5.17; 5.18). Maximum nickel concentrations have fluctuated above WQC, particularly in the predominantly saltwater part of the mainstem, and to some extent in the tributaries (Figure 5.17; 5.18). These values have been stable in the freshwater part of the mainstem and within acceptable limits (Figure 5.17; 5.18). Since 1997, maximum nickel concentrations have been reported above WQC in several tributaries, particularly Doctors Lake, Dunns Creek, and Sixmile Creek (Fig. 5.27E).

Selenium median and mean values have been relatively stable since 2005 in the LSJR (Figure 5.19; 5.20). Mean values in the predominantly freshwater portion of the mainstem and tributaries have been at or above the WQC (Figure 5.20). Mean selenium values in the predominantly saltwater portion of the LSJR mainstem have been within acceptable limits, however, maximum values have fluctuated above the WQC (Figure 5.19; 5.20).

Mean and median silver concentrations have fluctuated in the LSJR main stem since 2005 with lower values observed during 2015 to 2017 (Figure 5.21; 5.22). Median and maximum silver concentrations in the saltwater portion of the LSJR mainstem have exceeded the WQC since 2018; however, mean values have been just below WQC. Mean silver concentrations in the tributaries and freshwater portion of the LSJR mainstem have frequently exceeded the WQC, as was the case in 2020 (Figure 5.22; 5.27F).

Vanadium concentrations have been stable in the LSJR since the majority of the data were available in 2016 (Figure 5.23; 5.24). Higher concentrations have been reported in the saltwater mainstem areas and tributaries as compared to the freshwater mainstem areas. Currently, no WQC has been developed for vanadium. Concentrations causing lethality in 50% of organisms (LC50) have been reported to range from 0.46-14.8 mg/L for invertebrate zooplankton species (e.g., Daphnia) and fish such as rainbow trout and fathead minnows (Meina et al. 2020). However, physiological effects may occur at much lower concentrations than those causing lethality.  More data is needed to assess if the concentrations found in the LSJR would affect the aquatic life.

Median and mean zinc concentrations in the LSJR have been below the WQC and within acceptable limits since 2005, however, maximum zinc concentrations in the tributaries and saltwater portion of the mainstem have fluctuated above WQC during that time (Figure 5.25; 5.26). All zinc values in the LSJR mainstem were within acceptable limits in 2022. Elevated maximum zinc concentrations were reported in Butcher Pen Creek, Goodbys Creek, and Strawberry Creek (Figure 5.27E).

The metals analyzed in this report are widely used and therefore continue to enter the LSJR through point and nonpoint sources. The ratings from these metals are for the water column only; sediments act as a reservoir and may still contain high metal concentrations (see below). If sediments are disturbed by dredging or other activities, metals may be remobilized into the water column and may negatively impact aquatic life in the LSJR. The magnitude of potential impact is dependent on many concurring abiotic and biotic factors.

Concentrations of almost all the metals, particularly cadmium, copper, and silver in the predominantly saltwater portion of the LSJR mainstem from 2016-2022 have increased. Dredging of the LSJR began in February 2018 by JaxPort, and Hurricane Mathew and Hurricane Irma impacted Jacksonville October 7, 2016 and September 10-11, 2017, respectively. These events and other storm events could have contributed to the changes in the contaminant concentrations observed.

Vanadium cannot be assessed because a WQC has not been developed.

The current overall STATUS of metals (excluding silver) in the water column that were evaluated in this study (including aluminum, arsenic, copper, cadmium, lead, nickel, and zinc) in the predominantly freshwater portion of the LSJR mainstem is satisfactory with a TREND of unchanged. The STATUS of silver and selenium in the water column of the predominantly freshwater portion of the LSJR mainstem is unsatisfactory with a TREND of unchanged.

The current overall STATUS of metals (excluding copper and silver) and selenium in the water column of the predominantly saltwater portion of the LSJR mainstem is satisfactory with a TREND of unchanged. The current overall STATUS of copper and silver in the water column of the predominantly saltwater portion of the LSJR mainstem is unsatisfactory with a TREND of unchanged.

 The current overall STATUS of metals (excluding arsenic) and selenium in the water of the tributaries of the LSJR mainstem is unsatisfactory with a TREND of unchanged. The current overall STATUS of arsenic and cadmium in the water of the tributaries of the LSJR mainstem is satisfactorywith a TREND of unchanged.

The metals in sediments that we have evaluated in this study include aluminum, arsenic, cadmium, copper, lead, mercury, nickel, silver, vanadium, and zinc (Figure 5.28). Selenium was also evaluated. These elements have been elevated over natural background levels in sediments all throughout the LSJR for more than two decades and continue to do so today. Many of the sediments that were analyzed since 2000 have had concentrations of chromium, zinc, lead, cadmium, or mercury (discussed in more detail below) that are greater than natural background levels (NOAA 2008), sometimes by very large amounts. Sediments in Rice Creek that were analyzed in 2002 had mercury levels that were about 100 times greater than natural background levels. High metal concentrations were found in sediments elsewhere throughout the river, including the Cedar-Ortega system, Moncrief Creek off the Trout River, Broward Creek, and Doctors Lake.

From 2008 to 2022, despite some hot spots, mean metal concentrations in sediments are generally present at concentrations near their TELs; however, for most metals, values above TELs have been reported (Figure 5.26). In particular, lead and mercury (discussed below) continue to be problematic in the LSJR (Figure 5.32).  Individually, metals may exert pressure to aquatic life; however, exposure to all metals together may cause synergistic toxic effects, constituting an important class of stressor to the river. It should be noted that the number of sediment samples analyzed for metals has decreased over the past ten years.

Each metal is discussed individually. Aluminum data have been available since 2017 and mean values have fluctuated slightly during that time (Figure 5.28a). No PEL, TEL, PEC, or TEC are available for comparison, however, the aluminum concentrations in the LSJR are within range of background levels reported in the sediment in other areas (Moore 1991). Mean arsenic concentrations in the sediments of the LSJR have fluctuated since 2009 but with some values exceeding the TEL and TEC levels (Figure 5.28b). The mean sediment arsenic concentration decreased from 2020 to 2022 to acceptable levels; however, maximum arsenic values (e.g., 13.5 mg/kg in 2019) have been above the TEL and TEC values since 2013 (data not shown). Mean cadmium concentrations in the sediments decreased in 2009 and have been stable since then with values below the TEL and TEC limits (Figure 5.28c). Alternatively, maximum cadmium values have been above the TEL and TECs consistently since 2017. Mean copper values in the sediments have fluctuated since 2009, often approaching or exceeding TEL and occasionally TEC values (Figure 5.28d). Mean lead significantly decreased from 2009 to 2017 and has slightly fluctuated since then. Most years, mean values have generally been at or just below the TEL and TEC limits (Figure 5.28e) and maximum values have consistently exceeded these thresholds since 2009. Mean nickel concentrations in the sediments have been relatively stable, with most values slightly under the TEL and TEC (Figure 5.28f). Maximum nickel values have regularly exceeded the TEL (Figure 5.28f). Mean sediment silver concentrations have been relatively stable from 2009 to 2020, and most values were within acceptable marine limits (lower than TEL and PEL; Figure 5.28g).

Mean selenium values in the sediment have decreased since 2009, with the lowest values observed in 2021 and 2022 (Figure 5.28h). In 2022, selenium values ranged from 0.43 to 8.9 mg/kg in the LSJR sediment. No PEL, TEL, PEC, or TEC are available for comparison. Selenium concentrations generally range from 0.1 to 30 mg/kg in sediment worldwide, with levels above 0.5 mg/kg representing contaminated above background conditions (Moore 1991). Many of the selenium concentrations in LSJR sediment were above this concentration. Mean zinc concentrations in the sediments have been below TEL and TEC limits since 2009, with notable increases in 2012 and 2013 and a slight increase in 2021 (Figure 5.28i). Maximum zinc values were below TEL and TEC values from 2014 to 2022, with the exception of 2021 (e.g., maximum value of 329 mg/kg). Mean mercury concentrations fluctuated above PEL and PEC limits from 2009 to 2016. Since then, mean values have decreased but remained elevated above TEC and TEL limits, and maximum values are still elevated above PEL and PEC limits (Figure 5.28j). There are isolated locations in the LSJR, particularly in Rice Creek and the Cedar-Ortega system, where mercury occurs at concentrations high enough to impair the health of organisms. It is possible that mercury will bioaccumulate in those fish, crabs, and shellfish that spend most of their lives at these highly contaminated sites.

The STATUS of metals in sediments is unsatisfactory, and the TREND is unchanged.

5.4.5.2. Current and Future: Mercury in LSJR Sediments

5.4.5.3. Mercury in LSJR Fish and Shellfish