ENVIRONMENTAL SURVEY RELATIVE TO THE EXPANSION AND DEVELOPMENT OF THE PORT OF FORT PIERCE

FINAL REPORT

SUBMITTED TO ST. LUCIE COUNTY PORT AND AIRPORT AUTHORITY

28 OCTOBER 1991

R. Grant Gilmore, Ph.D. and M. Dennis Hanisak, Ph.D.

Harbor Branch Oceanographic Institution, Inc.

5600 Old Dixie Highway

Fort Pierce, FL 34946

VI. FUTURE, IMPACTS OF PROPOSED HARBOR EXPANSION

There are two major categories of impacts associated with the expansion Of Fort Pierce Harbor: (1) primary or direct and immediate impacts, and (2) secondary, direct and indirect impacts which may take place over a considerably longer period of time, but as a result of harbor expansion.

Primary Impacts - Direct impacts will take place with construction of bulkheads and docks, and dredge/fill activities associated with harbor expansion. The proposed dredged basin development of bulkheads and docks along the perimeter of the study site at the land-water margin will eradicate all shallow water habitats. This loss of habitat will have profound effects on other trophic levels as it will eliminate all principal shallow water larval/juvenile nursery habitats within the study area, most notably the seagrass beds and shallow boulder reefs (Figs. 6.1, 6.2, and 5.2).

All vegetation will be removed. There will not be any recovery of the seagrasses as the resulting depths will be too great for adequate light penetration to the bottom in order to allow seagrass growth. All of the shallow-water attached algae will also be removed. Although the light requirements of algae are lower than those of seagrasses, the new water depth would still be too great for successful recolonization by most attached macroalgae. There would probably still be drift algae present in the Port, but they would likely accumulate from other sources rather than being produced on site.

Rock reef ledge and boulder habitats will also be eliminated at the locations studied, except for the ledges of the Intracoastal Waterway north of the present Marcona docking site (Fig. 6.1, 6.2, and 5.2). The presently planned ACE dredging project for expansion of the Fort Pierce Inlet channel and turning basin will remove boulder and ledge habitat within the. study site at locations that are noted in Figure 5.2. A well developed reef fauna occurred at this location.

There is potential for suspended sediments associated with the dredging operation to settle on other seagrass and algal habitats within the inlet, particularly if turbidity curtains are not effective in the high current zones of the inlet channels and Intracoastal Water-way. Ibis could reduce seagrass and algal growth and survival. The greatest concern over these impacts are their potential damage to the nearby, extensive Jim Island seagrass beds.

Complicating the impacts of dredging is the quality of sediments resuspended or disposed of during the dredging operation. Sediment contaminant studies presented in this report indicate that there are relatively high levels of certain contaminants at specific locations. These sediments, when disturbed, have the potential to contaminate the water. column and other regions of the inlet and lagoon. If they are placed at other locations within the lagoon Or along ocean beaches, they would then contaminate those locations also. Even without contaminates, sediment quality may have profound biological impacts where they are deposited as benthic communities (seagrass and associated vertebrate/invertebrate organisms) are highly dependent on sediment quality for proper community development.

Acute sedimentation turbidity impacts of Port development are primarily a function of how the dredging is performed. Historically, dredging has had well-documented major impacts on the seagrasses resources throughout the state and nation (previously discussed under "Vegetation Studies"). The biggest concern with seagrasses regarding acute impacts associated with dredging are due to increased turbidity and sedimentation. Although less of a concern than seagrasses locally, the benthic macroalgal community is also sensitive to reduction in water clarity following dredging (Richardson 1991). Increases in turbidity result in reduced water transparency which causes reduced growth and survival of submerged vegetation and loss of its function to fish, wildlife, and society (impacts on fish and wildlife are discussed in greater detail under "Fauna Studies" chapter). The permanent loss of vegetation in the study area will upset the natural balance of water column filtration by seagrasses in the Port area and could affect the stability and function of nearby established and developing seagrass communities. The impact of dredging can be long-lasting since such disturbance may create sediment conditions unsuitable for seagrass recolonization for a protracted period (Zieman 1975).

The magnitude of acute impacts associated with dredging depends on their intensity and duration. Dredging techniques should be selected to eliminate or to minimize increases in turbidity and sedimentation. In this regard, the concerns and recommendations of the participants of the National Turbidity Workshop held last year in West Palm Beach (Kenworthy and Haunert 1991) should be carefully considered. Emphasis needs to be placed on the light requirements (as Photosynthetically Active Radiation = PAR) of seagrasses relative to existing water quality conditions.
Every precaution should be taken to insure that no impacts occur outside of the immediate area to be dredged.

Secondary Impacts - These are impacts related to the long term human activity at tile study site and may be considered more significant than primary impacts. Presently, there are marina and dock facilities adjacent to the study site, in Taylor Creek and across from the Fort Pierce Oil Terminal. Sediment studies from Taylor Creek indicate that several petroleum based contaminants (eg. PAI-1) and, most notably, the heavy metal tin (typically originating from paints, including boat hull paints), concentrate where there is organic sediment deposition and a source of pollution.

We do not know the nature, quality or quantity of long term activities at the development site other than increased ship traffic and shore processing facilities for the cargo. 7lerefore, it is difficult to predict the nature of secondary impacts. Any increase in ship and boat traffic in the port area has the potential to impact manatee populations as boat-manatee collisions are known to be a significant source of manatee mortality. If the planned site development will increase petroleum combustion activity and sources of heavy metals, along with organic and clay sediment deposition, there is considerable potential for pollutants to enter sediments and biota around the harbor site. Through biomagnification heavy metals could be incorporated in top level predators through the food chain. Many of these top level predators are fishery species. Filter feeders such as the soft corals, tunicates, barnacles and bivalve mollusks could also concentrate metals and certain halogenated hydrocarbons. Therefore, the principal concern for secondary harbor development impacts is water and sediment quality deterioration through commercial or industrial, transportation (aquatic and terrestrial) and facility sources. Terrestrial industrial activities could decrease water transparency through increased runoff, and thus affect vegetation. Vegetation would also be influenced by elevated nutrients and the discharge of toxic materials, often associated with ports.

The magnitude of these impacts could range from negligible to severe, as they are primarily a function of how the Port will be used and what activities will be permitted by the development. The specifies of these impacts should be examined in greater detail prior to Port development of the final plan. These impacts need to be minimized as much as possible as seriously degraded water quality in the Port area could result in greater loss of submerged vegetation and critical faunal/fishery habitat than the primary impact of sediment vegetation removal by dredging.

Literature Cited

Kenworthy, W.J. and D.E. Haunert (eds.). 1991. The Light Requirements of Seagrasses: Proceedings of a Workshop to Examine the Capability of Water Quality Criteria, Standards and Monitoring Programs to Protect Seagrasses. NOAA Technical Memorandum NMFS - SEFC -287.

Richardson, J.P. 1991. Community description and monitoring of Cumberland Island Jetty at Kings Bay -- St. Mary's River Entrance, Georgia. Biological and Physical Aspects of Dredging Kings Bay, Georgia/Coastal Zone '91 Conference - ASCE, pp. 58-74.

Zieman, J.C. 1975. Tropical seagrass ecosystems and pollution. Chapter 4 in E.LF. Wood and R.E. Johannes, (eds.). Tropical marine pollution. Elsevier, New York.