🛳️ Key Findings from The Murray Report
In 2005, the City of Key West and the US Navy commissioned a comprehensive assessment on the impacts of the cruise ship industry in Key West.[1] Known as the Murray Report, it devotes 110 pages to the impact of cruise ships on the marine environment, drawing upon decades worth of scientific findings from more than 100 previous studies. Key conclusions are as follows:
1. THE PORT OF KEY WEST HAS UNIQUE PHYSICAL AND ENVIRONMENTAL CHARACTERISTICS. IT SUPPORTS PROTECTED SPECIES AND ECONOMICALLY IMPORTANT FISHERIES.
The Murray report explains why cruise ships pose a greater threat to Key West’s natural environment and its marine-environment-based economy than they do in other cruise ports. “Although a number of other ports in the U.S. (including Alaska and Hawaii), Bermuda, Mexico, and the wider Caribbean have addressed or are addressing many similar environmental issues related to cruise ships, including adequate harbor depths and infrastructure, and potential environmental degradation, this review deals mainly with activities of cruise ships and other large vessels in Key West. The situation in Key West appears to be unique in that a relatively shallow and narrow main channel and harbor (relative to vessel size) exist in close proximity to coral reef ecosystem habitats and communities that depend on clean, clear water.” “General categories of these habitats include coral reefs (bank or platform margin reefs and patch reefs) hardbottom, seagrass, and bare or lightly vegetated substrates.” “They are known to support important and economically valuable commercial and recreational fisheries and provide diving sites for a thriving dive industry around Key West.” “Natural habitats and productive benthic communities surround the dredged channel and harbor used by cruise ships.
Key West's ship channel crosses the Great Florida Reef Tract and the Florida Keys National Marine Sanctuary. It is approximately 6 miles long, with an average width of 300’. Although it has a controlling depth of 34’, live coral formations on either side of the channel rise to a depth of only 16’ or less. Cruise ships transiting the channel in recent years are as large as 1046’ in length and 130’ in width, with a draft of 28.5’.
These areas “provide habitat for a myriad of fishes, shrimps, crabs, and other species, and therefore have been designated as Essential Fish Habitat (EFH) by the South Atlantic Fisheries Management Council.” “Much of the area adjacent to the Key West channel and harbor, and particularly in Hawk Channel, includes patch reefs and hardbottom. Designated also for some species or species groups within EFH are Habitat Areas of Particular Concern (HAPC). HAPCs either play critical roles in the life history (e.g., spawning, feeding) of federally managed species or are those areas vulnerable to degradation from fishing or other human activities.” “HAPCs for queen conch exist in two areas near Key West, the hard bottom adjacent to the main channel, and off Fort Taylor and Boca Chica. Of the estimated 28,000 conch in the spawning stock from Eastern Dry Rocks to Looe Key during 2001, about 18,000 were found in the region extending from Eastern Dry Rocks to Eastern Sambo. This region, by far, represents the greatest reproductive output of Florida’s queen conch population, and any impacts, particularly elevated turbidity, could impact planktonic larvae and newly settled individuals. The southern portion of the channel intersects this area. In addition, juvenile and non-reproducing adult conch are common in hardbottom along the oceanside of Key West and on the west side of harbor (Navy 2003).”
Murray identifies a number of “species listed by the State as warranting protection that may use the channel and harbor or immediately adjacent marine area, and that may be affected by cruise ship activity.” These include protected, threatened, and endangered marine and avian species such as loggerhead, green, and hawksbill turtles; manatees, brown pelican, black skimmer, least tern, roseate tern, osprey, and pillar coral.’’
Murray also explains the connection between the marine environment and the local economy. “The high quality of recreational and commercial fishing in the Key West area is world renowned with a seemingly unlimited variety of species available for sport or harvest. These historic Keys and Key West industries significantly generate thousands of jobs in communities and tens of millions of dollars in income.” In particular, Murray emphasizes the commercial and recreational fisheries for spiny lobster, stone crab, snapper, and grouper, and the “adverse economic impacts resulting from the use of the Outer Mole and other cruise ship activity in Key West.”
2. CRUISE SHIPS IN KEY WEST’S NARROW, SHALLOW SHIP CHANNEL ARE DIRECTLY RESPONSIBLE FOR HIGH TURBIDITY LEVELS THAT ARE LETHAL TO SEA LIFE.
Section 3.B.2 of the Murray Report examines the impacts of turbidity and sedimentation on the marine environment, explaining that “along with phosphorus, turbidity is considered probably the second most important determinant of ecosystem health in the Florida Keys (Jones and Boyer 2002).” “Optimal coral survival, growth and recruitment occurs under low nutrient and low turbidity conditions, although coral decline in the Keys is considered to be a result of multiple stressors (Cook et al. 2002). Lower skeletal deposition of calcium carbonate in experimental transplants of hard corals into nearshore waters has been attributed to higher turbidity levels. Turbidity and water temperature have been described as major characteristics of nearshore waters that negatively affect corals on the Florida Reef Tract (Cook et al. 2002).”
“Measuring turbidity is in this case a surrogate for measuring sediment (silt, sand, rubble, organic matter, etc.) scoured off the bottom by vessel propeller generated turbulence and evidently by displacement pressure waves moving along the bottom. Simply, in waters 30+ feet deep, the level of turbidity measured in the upper water column is a function of what is happening to the bottom when a large vessel close to the bottom moves along or is turning…In these situations, larger particle sizes when redistributed in heavy loads can result in the greatest consequence for colonized or vegetated benthic habitats. Sediment resuspension apparently occurs in two ways – directly from propeller and thruster wash and turbulence, the other is the little addressed phenomena of surge waves moving laterally away from a large displacement vessel that resuspend sediment closer to the bottom.”
Murray acknowledges naturally occurring turbidity and isolates ship-generated turbidity as a remediable man-made problem. “It is acknowledged that high winds and storms result in naturally occurring resuspended sediment and water column turbidity.” “Turbidity levels were approximately three to four times higher during windy conditions than during the selected calm weather period (USACE 2003).” “Natural processes that result in large scale disturbance in Keys waters are episodic, often with long intervals between events.”
Royal Caribbean's Grandeur of the Seas disturbs bottom sediment while approaching the Port of Key West in October 2005. Cruise ships calling on Key West in recent years are much larger than Grandeur of the Seas. The average displacement of cruise ships calling on Key West has increased 30% since 2005; maximum ship size has increased 45% since that time.
“The growing number, size, and draft of recreational and commercial vessels now using Keys waters, such as Key West channel and harbor, are creating turbid conditions considered to be chronic in places. Vessel generated resuspended sediments is a growing concern in areas with high boat traffic, including open waters. Turbidity reduces water clarity, which reduces sunlight penetration through the water column (which can adversely affect the growth of submerged vegetation (Kruczynski and McManus 2002).”
“Presence of these resuspended sediments in the water column, as indicated by turbidity can interfere with feeding/respiration by aquatic organisms (FDEP 2005). Light levels are also reduced, which affects the health of seagrasses and corals as light extinction is directly related to water turbidity (Jones and Boyer 2002). Resuspended sediment and turbidity could also affect hard-bottom communities by smothering (Kruczynski and McManus 2002).”
“Lethal effects were known to result from excessively high sediment loads or high sedimentation that took place in a short period of time. More subtle lethal effects that can eliminate native species may occur at low but chronic sediment loads or sedimentation with long exposure. Under these conditions risks may exist to any life history stage, behavioral activity, reproductive ability, or metabolic function and result in decreased viability of any number of marine species in the vicinity of chronic resuspended sediment. (Sherk 1971)”
“Data and other available information indicate that impacts from cruise ship and other large deep draft vessels are occurring to water quality and benthic habitats in the area of the main channel and harbor in Key West. Bottom scouring, severe sediment resuspension and redistribution, plume turbidity far above background levels, interference with historic diving and fishing activities, and bottom excavation in the cruise ship anchorage are resulting from the passage of these vessels. State and federal laws and regulations related to the maintenance of water quality, protection of bottom habitats in the area, and protection of publicly owned submerged lands may be violated when these severe events occur. The fact that cruise ships and other large vessels resuspend bottom sediment in Key West channel and harbor and in the offshore anchorage and elevate turbidity levels in the water column is undisputed.”
“On March, 1, 1999, the DEP and the FKNMS measured turbidity in the wake of a cruise ship at the Outer Mole at nearly 20 times above background. The same day in the anchorage just west of Marker “9” (see Section 3.B.9) they measured turbidity at 7 locations within a plume from the Enchantment of the Seas that averaged 30 times the background average values of 3.7 NTU(FDEP 1999a). On March 3, 1999, FDEP monitoring of plumes created by cruise ship movement at the Outer Mole showed levels on average 11 times over background with many samples more than 29 NTUs (Class III standards) above background. Measurements in plumes offshore the same day showed levels as high as 193 NTUs while background levels were near 3 NTU (FDEP 1999b). On March 11, 1999 numerous measurements at the Outer Mole by FDEP (in plumes from cruise ships and tugboats) showed background levels averaging about 3 NTU and plume levels averaging nearly 50 NTU (FDEP 1999c).”
“Cruise ship traffic has been documented to create turbidity plumes during transit between the outer sea buoy and the docks in the harbor, a passage that is typically an hour long (Figure 3.B.8). In 2000 the FKNMS reported that there is evidence of a turbidity problem relative to movements of large vessels in the Key West area. Evidence included measurements of turbidity created by ship main engines and thrusters during docking maneuvers, visual observations of cruise ship-generated turbidity plumes and visual observations of seagrass and bottom damage from anchoring. The FKNMS also reports that measurements of ship-generated turbidity are orders of magnitude greater than measurements of background turbidity, and that these turbidity events last from one to several hours.”
“Turbidity levels have heavily impacted corals adjacent to the harbor and ship channel, especially to the west. Ship generated turbidity is clearly differentiated and distinguished from natural background turbidity.” (FKNMS 2003b). “In 2002, the FKNMS reported to the Large Vessel Working Group that ‘large plumes of resuspended sediment are observed with each pass of a cruise ship or other large deep draft vessel in and out of the channel, particularly on low tide. Turbidity levels observed with docking cruise ships greatly exceed state water quality standards and local fishermen observe and report the direct effect of turbidity plumes on the fish they are targeting.’ (FKNMS 2002).” “Ship generated turbidity is an added stressor to natural systems above and beyond the background and storm event turbidity impacts.”
3. CRUISE SHIPS HAVE GOTTEN MUCH LARGER SINCE THE MURRAY REPORT
Turbidity generated by large vessels is a function of how much water is displaced by the vessel, and displacement roughly correlates to a vessel’s gross ton weight. Compared to 2005, cruise ships calling at Key West today are 30% larger on average, while the largest ships today are 45% larger.
[1] “THE IMPACTS OF THE CRUISE SHIP INDUSTRY ON THE QUALITY OF LIFE IN KEY WEST”; RFQ No. 04-001; City of Key West Naval Properties Local Redevelopment Authority, Thomas J. Murray & Assocs. October 2005. Click here for full report.