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saltwater barrier line, and would decrease any benefit the CERP Coastal Wetlands
restoration could provide once implemented. NPS also pointed out the lands had been
previously identified as providing wildlife connectivity, and are frequented by several
endangered or threatened species including the Florida panther, indigo snake, wood
stork and state listed wading birds. NPS also expressed concerns about the lack of
supplies of water to meet the plants needs, disposal of same, archeological issues, and
the threats from sea level rise which would leave the facility as an island at some future
stage (NPS, 2007).
WATER QUALITY
Water quality issues of concern for Biscayne Bay and Biscayne National Park are
primarily caused by their proximity to Miami Metropolitan area, home to more than 2.4
million people, and also to agricultural activities in the Homestead area, and even to
agriculture south of Okeechobee Lake whose nutrients pesticides, and agro-chemicals
may be transported along the canal network and brought south to the Biscayne Bay
basin. All waters in Biscayne Bay are Class III, whose designated use is recreation and
propagation and maintenance of a healthy, well-balanced population of fish and wildlife.
Biscayne Bay is also a designated Outstanding Florida Water (OFW). Main water
quality issues are: water turbidity); nutrient loading and enrichment, bacterial
enrichment, chemical compounds derived from runoff, pesticides, and industrial and
stormwater pollutants (Lietz and Meyer 2006; http://www.miamidade.gov). Canal inflow
is the primary loading mechanism for pollutants to the bay followed by subsurface runoff
from the shallow, highly permeable Biscayne Aquifer, which allows rapid movement of
groundwater with direct subsurface connection to the bay and canals (Klein and Hull
1978; Lietz 1999; Alleman et al. 1995). Caccia and Boyer (2007) identified atmospheric
deposition as an important contributor to nutrient enrichment.
Contaminated runoff and groundwater have been identified as major sources of
pollutants (pathogens and toxicants) to the Dade County canal system (Long et al.,
1999, 2000, 2002, 2005), which finally reach the Bay. Polluted waters have been
exposed to leachates from agricultural fields, landfills and municipal dumps, through
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atmospheric deposition of pollutants derived from combustion sources, agricultural
applications, industrial discharges and vehicle emissions, and finally from direct
disposal and point sources. Three groups of contaminants have been consistently
targeted when environmental assessments of Biscayne Bay are conducted: trace
metals, chlorinated pesticides, polychlorinated biphenyls (PCBs) and polynuclear
aromatic hydrocarbons (PAHs).
Early studies of pollution were focused on the impact of raw sewage from open
sewers and septic tanks (Wakefield 1939; Moore et al. 1955; McNulty 1956). The
Mowry Canal had elevated phenol levels (Cheesman 1989) and the bay north of
Rickenbacker Causeway was more affected by chemical contamination and toxicity
than to the south of the causeway (Long et al. 1999). Organophosphates have been
detected in sediments at three sites including Military and North Canals (Cantillo and
Lauenstein 2004), but sediments in open areas of the park have generally low toxicity.
Lidz (2002) reported initial results of surface sediment samples analyzed for heavy
metals and concluded that deformed benthic foraminifera were common near the landfill
(Black Point area).
NOAA conducted intensive regional surveys to describe the incidence, severity,
and spatial extent of adverse biological effects associated with chemical contamination
in Biscayne Bay in 1995. Results showed high levels of sediment contamination and
severe toxicity in several peripheral canals and tributaries, notably the lower Miami
River. The 1995 data also showed sporadic low-level occurrence of sediment toxicity in
southern Biscayne Bay. From 1999 results it is apparent that contaminant plumes and
associated toxicity do not appear to extend seaward of the mouth of the canals in an
appreciable manner. Concentrations of contaminants in the sediments in open areas of
Biscayne and Manatee Bays are generally low (Cantillo and Lauenstein 2004)
Nutrient enrichment
Nutrient loading in Biscayne Bay is correlated to population density (Caccia and
Boyer 2007), agriculture and storm events (Briceño et al. 2010; Migliaccio and Castro
2009). Additionally, climatic cycles and events seem to affect nutrient loading to the bay
with increases in loading rates during wetter years (Caccia and Boyer 2007). Surface
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waters from the three most important land-cover types in Biscayne Bay watershed,
agricultural, urban and wetland cover, have different chemical characteristics. NOx
concentrations are higher in agricultural than in urban or wetland areas; concentrations
of ammonia, TP, and Chla tend to be higher in urban areas than in wetland or
agricultural areas; and TON concentrations are higher in wetland and urban areas than
in agricultural areas (Britt and Cheesman 1992; Lietz 1999; Haag et al. 1999; US DOI
NPS. 2003; Caccia and Boyer 2007; Migliaccio et al. 2008). Given the oligotrophic
nature of these waters the system responds very rapidly to small nutrient enrichment,
especially to increases of phosphorous, the limiting nutrient (Brand 1988, 2001).
Turbidity
Most turbidity in Biscayne Bay is produced by re-suspension of bottom
sediments, both naturally and anthropogenically generated. Natural agents of
resuspension are water currents (tidal driven), wind-produced waves (climate related)
and extreme events (storms and hurricanes). Anthropogenic re-suspension occurs
when boats are grounded and from boat wakes, as well as from canal discharges.
Storm induced turbidity is the principal mechanism for re-suspension along the reef
tract. The area north of BNP adjacent to Key Biscayne is affected by high turbidity from
the Miami River, caused by re-suspended flocculants (Harlem, 1979). Turbidity
problems in Biscayne National Park are reasonably well understood with good data on
the sources as well as the effects on organisms. As long as dredging projects are
restricted and boat usage regulated, this problem will be minimized. Turbidity in
northern sections of the Bay has been a long term problem and is likely to get worse as
the downtown Miami area continues to grow and the seaport is expanded.
Microbial contamination
Miami-Dade County beaches are regularly tested and other sites are
occasionally tested for microbial contamination. Typical microbial groups of concern
include fecal coliforms, enterococci, Clostridium perfringens, and coliphage and known
pathogens such as Escherichia coli, Serratia marcescens, and human enterovirus.
Endemic problems are largely confined to areas north of BNP and may not relate to
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conditions within the Park. High concentration of fecal coliform bacteria in the C-8
(Biscayne) Canal, the C-7 (Little River) Canal, the C-6 (Miami River), C-6 (Miami River)
Lower Segment, and the C-6 (Miami) Canal, within the Biscayne Bay Basin, have
rendered these waterbodies impaired. Threats posed by microbes are not only for
humans but for biota in general. Four bacteria have been previously implicated in coral
disease, Aurantimonas coralicida: white plague (type II) (Richardson et al. 1998),
Serratia marcescens: white pox (Patterson et al. 2002), Vibrio shilonii: bleaching
(Kushmaro et al. 1997), and Vibrio coralliilyticus: bleaching and necrosis (Ben-Haim and