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or anthropogenic changes in South Florida have influenced the seagrass habitat and the
environmental and physical conditions within the Port of Miami. Results showed that
there was minimal change in seagrass distribution, cover-density, and occurrence over the
collection period. The habitat in POM is stable, which is an improvement from the 2005
report of aerial photography, which reported a large decline in the North Biscayne Bay
basins from previous years (Blair et al. 2011). Monitoring has shown that restrictions and
regulations in the area have mostly been effective in reducing the loss of seagrass habitat.
The construction environmental safety regulations and mitigation have minimized any
major impact on the health of the port’s seagrass community.
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Some seasonal and annual patterns were evident in the environmental and
physical measurements within the basin. The research shows that turbidity has improved
since the start of the project with recordings currently half of what was seen in previous
years (Ecosummary Biscayne Bay 2002; Caccia and Boyer 2005). There is seasonal
variation in water temperature and salinity; the fall season has warmer water temperatures
and lower salinities after the summer rain. Air and water temperatures displayed an
overall increasing trend across the study period, which may negatively impact the
environment in the future.
In a few cases certain environmental and physical data were considered
significant enough to be used as predictors of seagrass cover-density or occurrence.
However, in most cases the environmental measurements supported the null hypothesis
when attempting to predict variation in vegetation cover-density or occurrence and were
removed from the regression models due to their lack of correlation or contribution. In
the POM the model showed that water depth is the major factor that determines the
cover-density and occurrence of the dominant habitat building seagrasses. The models
also revealed that sediment depth and turbidity also played an important role in the
seagrass cover-density and occurrence within the basin. Areas with lower turbidity and
deeper sediment depths are ideal for seagrass establishment and growth.
The seagrass habitats within the POM have been influenced by natural and
anthropogenic changes over time. Most of the significant changes seen in the measured
variables can be related to weather/storm events; however, some construction activity
during the study period could have contributed to slight increases in turbidity during
certain collections. The first collection year (2005) experienced major construction
(dredging) and heavy storm (hurricane) activity in the region which created higher
turbidity measurements within the POM for that year. The weather at the end of 2009
and throughout 2010 produced a prolonged cold period which negatively impacted
seagrass cover-densities.
The seagrass habitats in North Biscayne Bay have been subject to a number of
disturbances including storm scour, uprooting and overgrazing by animals, introduction
of invasive species, infection by pathogens and parasites, algal blooms, commercial
fishing practices, stress due to water quality degradation and reduced water clarity,
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physical impacts from dredge and fill operations, prop scaring, vessel wakes and
groundings, and physical and toxicological impacts due to spills of oil and other toxic
materials (Short and Wyllie-Echeverria 1996; Kemp 2000; Fourqurean et al. 2002; FMRI
2003; Orth et al. 2006; BBAP 2011). Even with the major direct and indirect impacts to
the region, the benthic habitat continues to persist in the area.
It is easy to relate large visible events to change in seagrass distribution, but there
are many other underlying causes involved in the process. A longer, more complete
study of the water quality within the region is recommended for future conservation and
management. The completion of the Deep Dredge Project leaves opportunity for future
research regarding the status of the Port habitat and environmental conditions. The
existing habitat has been documented and studied over the years through several
agencies. Although environmental and physical measurements from SFWMD agencies
were not completely consistent, they still provided a general record of measurements for
comparison. Future studies from DERM and USGS (2014-2016) (Daniels and Grimes
2016) and other agencies can examine possible habitat damage from the construction
activities that may help educate on successful and unsuccessful construction techniques
in marine habitats. If blasting and dredging techniques are implemented correctly, there
should be minimal impact to the surrounding seagrass habitats, as seen in 2005 and 2010.
Some environmental and physical conditions within the POM have improved and
the seagrasses have remained fairly stable over the course of the study, but several
potential threats may be an issue in the future. The global distribution of seagrass beds
has changed gradually over time in response to several factors for instance sea-level and
temperature, as well as extreme high and low storm activity; however, anthropogenic
pressures have been identified as currently having the largest impact on seagrass loss
change (Orth et al. 2006). South Florida, including Miami, continues to grow in
population and tourism, and in turn more direct modifications will be required to the
surrounding areas to support this trend. The potential for increased runoff and pollution
from inland sources, and the direct impacts from new construction and irresponsible
boating activity are a major threat to the seagrass habitats within the Port of Miami. The
global climate shift also has major potential to harm the coastal habitats with increased
intensity in air and water temperatures and storm activity, as well as the threat from sea
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level rise. The complex ecology and multiple roles that seagrass communities provide
are the reason to maintain and improve their habitat (Dawes 1998). Seagrasses are a vital
part of the South Florida coastal ecosystem and economy. With increased monitoring
efforts from environmental agencies and with more outreach and education to the public,
these valuable seagrass habitats will continue to sustain themselves in the future.
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6.0 Literature Cited
Abal, E. G. and W. C. Dennison. 1996. "Seagrass Depth Range and Water Quality in
Southern Moreton Bay, Queensland, Australia." Mar.Freshwater Res 47: 763-771.
Alleman, R.W., S.A. Bellmund, D.W. Black, S.E. Formati, C.A. Gove, and L.K. Gulick.
1995. An update of the surface water improvement and management plan for
Biscayne Bay. Technical Supporting Document and Appendices, South Florida
Water Management District, West Palm Beach, FL.
Allison, I., N.L. Bindoff, R.A. Bindschadler, P.M. Cox, N. de Noblet, M.H. England, J.E.
Francis, N. Gruber, A.M. Haywood, D.J. Karoly, G. Kaser, C. Le Quéré, T.M.
Lenton, M.E. Mann, B.I. McNeil, A.J. Pitman, S. Rahmstorf, E. Rignot, H.J.
Schellnhuber, S.H. Schneider, S.C. Sherwood, R.C.J. Somerville, K. Steffen, E.J.
Steig, M. Visbeck, and A.J. Weaver. 2009. The Copenhagen Diagnosis, 2009:
Updating the World on the Latest Climate Science. The University of New South
Wales Climate Change Research Centre, Sydney, Australia.
Bell, F.W. 1993. Current and projected tourist demand for saltwater recreational fisheries
in Florida. SGR-111. Florida Sea Grant College Program, Gainesville, Florida. 95
pp
Bialczak, M., J.R. Murley, and L. Cantral 2001. Biscayne Bay Partnership Initiative;
Survey team final reports. Miami, FL 320 pp.
Biebl, R., C.P. McRoy. 1971. Plasmatic resistance and rate of respiration and