In the past several decades, there has been a well-documented demographic shift toward higher concentrations of human settlement in the coastal zones of many countries including the U.S. (Culliton et al., 1990; Figure 3.5). More than half of the U.S. population now lives in coastal counties, a trend that is expected to continue to increase (Pew Oceans Commission, 2003; Cicin-Sain et al., 1999). This trend has increased the frequency and magnitude of impacts from activities such as the construction of residential developments, hotels and resorts, recreational facilities, and infrastructure such as roads and wastewater treatment plants (WWTPs).

Terriginous sediments in runoff from construction sites and roads are often a major threat to nearshore areas. Dredging of nearshore sediments for marina facilities, ship access and navigation, beach nourishment, and building materials can introduce significant quantities of particulate matter into the water column. While strong currents tend to dissipate some of the added sediments, nearshore areas with gentle slopes and low flushing rates tend to accumulate sediments, which can have detrimental effects on sessile invertebrates like corals (Rogers, 1990). Physical smothering may be the most obvious effect of sedimentation. Although most corals have some ability to rid themselves of foreign particles, the removal of sediments requires the diversion of energy from vital activities such as reproduction and feeding. The negative effects of the accumulation of sediments on corals can be exacerbated by wave action that repeatedly resuspends sediments into the water column (Rogers, 1990). Increased turbidity in the water column, whether episodic or chronic, reduces light availability for photosynthesis and growth. Increases in nearshore sediment loads have been shown to affect morphology of corals and gorgonians as well as inhibit the development and recruitment of coral larvae (Rogers, 1990). Coral species react differently to this stressor, and coral reefs in waters experiencing increased turbidity may exhibit a shift in community composition toward greater dominance of corals that are more tolerant of lower light levels and better adapted to remove sediments.

Alteration of watersheds and associated changes in vegetative cover often decrease the ability of the land to absorb rainfall, which flows through streams and channels, carrying sediments and pollutants into nearshore areas. Generally, runoff from developed watersheds carries higher sediment loads than from undeveloped areas, and this is more pronounced in areas where the topography is characterized by steep slopes. Removal of mangrove forests that normally trap sediments may allow a greater proportion of terriginous sediments to reach reef ares.

In addition to sediments, runoff from developed watersheds tends to have higher concentrations of waste products. Increased freshwater inputs are actually considered pollutants as they can decrease the salinity levels in some nearshore areas. Other contaminants derived from human use of nearshore areas include oil leaking from vehicles, pesticides and lawn fertilizers applied to yards, parks and golf courses, chemicals in asphalt that wash off roads, excrement from livestock and domesticated animals, and litter.

The development of infrastructure is also a major concern. In many areas, coastal development often occurs without a commensurate improvement in the wastewater infrastructure, and existing systems cannot adequately accommodate the added burden. As a result, untreated or partially-treated sewage overflows into nearshore areas. Outside of urban areas, many homeowners are not able to access WWTPs and often must rely on septic tanks, which are subject to corrosion and leakage. The hard-to-detect leaks often allow untreated sewage to seep into groundwater and nearshore waters. A recent report (Carter and Burgess, Inc., 2002) assessing the sustainability of tourism in Hawaii noted that many of the island’s municipal wastewater systems are nearing capacity. While most new developments have private WWTPs to satisfy permit conditions, many residents still rely on private systems, such as septic tanks, which are in various stages of disrepair. Though they considered myriad aspects of tourism, the authors of the study contend that such nonpoint source pollution is "one of Hawaii’s greatest environmental threats" (Carter and Burgess, Inc., 2002).

Other infrastructural issues include the problems of adequate waste disposal and the construction of docks and piers that can result in habitat loss. In summary, coastal development presents a wide range of challenges for coastal areas, especially in terms of the number and scale of construction projects, capabilities of infrastructure, intensity and type of land use, and increases in sedimentation and pollution levels.

Scientific studies have now shown that divers and snorkelers can have a significant negative impact on coral reefs in terms of physical damage and a concomitant reduction in their aesthetic appeal (Hawkins and Roberts, 1993; Hawkins et al., 1999; Rouphael and Inglis, 2001). For example, a snorkeling trail created in the Virgin Islands National Park’s Trunk Bay in the 1960s had deteriorated substantially when observed in 1986 with visitor numbers estimated at over 170,000 per year. Only 10 of 50 tagged Elkhorn coral colonies remained undisturbed during a seven-month period of observation (Rogers et al., 1988).

Overfishing has been identified as a major concern in all U.S. states and territories with coral reefs and has been identified by the USCRTF as a priority reason for the development of local action strategies. In most cases, the large number of species in these multi-gear, small-scale fisheries has made it impractical to conduct standard stock assessments for more than a fraction of the species (Table 3.4), and such data-intensive, single-species approaches have been criticized as unrealistic for most reef fish systems (Sale, 2002). There is evidence of serial depletion of reef resources in Florida and around all populated U.S. islands. In Hawaii, long-term catch rates suggest that stocks of nearshore fishes have declined by nearly 80% between 1900 and the mid-1980s (Shomura, 1987). Catch per unit effort (CPUE) of reef fishes in Guam fell by more than 50% between 1985 and 2000 (Birkeland et al., 2000), while the CPUE fell 70% in the American Samoan reef fishery, accompanied by a shift in species composition, over a period of 15 years between 1979 and 1994 (Birkeland, 1997). The Nassau grouper fishery, the highest value commercial fishery in Puerto Rico and the U.S. Virgin Islands (USVI), collapsed in the 1980s due to overexploitation of spawning aggregation sites and the species was identified as a candidate to be listed as threatened or endangered under the Federal Endangered Species Act (16 U.S.C. § 460 et seq.) in 1991. In the Florida Keys, the nation’s most extensive and long-term reef fish monitoring program has revealed that 77% of the 35 individual stocks that could be analyzed in Biscayne Bay
are overfished (Ault et al., 2001).

Because of long-term trends in the exploitation of mixed reef fisheries, there are few places that maintain relatively intact fish populations to serve as experimental controls. The Northwestern Hawaiian Islands (NWHI) and some of the uninhabited U.S. Pacific Remote Island Areas probably represent the closest approximation to unexploited coral reef ecosystems in U.S. waters. The average fish biomass in the NWHI is 2.6 times greater than in the Main Hawaiian Islands (MHI). More than 54% of the total fish biomass in the NWHI is composed of apex predators, compared to less than 3% in the MHI. These differences have been attributed to overfishing in the MHI (Friedlander and DeMartini, 2002).

Physical damage to the benthos from certain fishing techniques is well-documented. Traps set for fishes or lobsters can cause physical damage to corals, gorgonians, and sponges. They may also result in by-catch and "ghost fishing" if they are lost or not regularly checked. Trap fisheries are most common in Florida (lobster and stone crab) and the U.S. Caribbean (fish and lobster), and are generally less prevalent in the U.S. Pacific. Large gill and trammel nets have also been identified as a growing concern, particularly in St. Croix (USVI) and Hawaii. Large gill nets are set on reefs and their lead-lines can cause extensive damage when the nets are hauled into the boats. In addition to legal fishing activities, illegal techniques can cause severe damage to reefs. Use of chlorine bleach has been reported in Hawaii, Guam, and Puerto Rico (USCRTF, 1999), and traditional plant-derived poisons are still used occasionally in the subsistence fishery in American Samoa. The use of cyanide for fishing has not been reported on U.S. reefs, although the expansion of the live food fish trade to the Marshall Islands has raised concerns about its potential use there. Blast fishing, probably the most destructive technique, has rarely been reported on U.S. reefs.

Other indirect impacts to coral reefs associated with fisheries include anchor damage from fishing boats, which has been identified as a problem in Florida and the U.S. Caribbean. Trawling damage to coral areas has been identified as a problem in deeper coral areas in the Gulf of Mexico. It was also a major cause of destruction of the deep water Oculina coral banks off the east coast of Florida before the development of the Experimental Oculina Research Reserve. In general, such damage is inadvertent rather than due to directed fishing, but trawls can cause tremendous damage when hauled over hard bottoms with coral. Furthermore, groundings of fishing vessels have had major, albeit localized, impacts on certain reefs.

The use of cyanide has not been reported or observed in the U.S., with the possible exception of limited use in some of the Freely Associated States (e.g., Marshall Islands) associated with the live reef fish food trade.

The U.S. is the world’s largest consumer of ornamental coral reef species, importing 60-80% of the live coral, over 50% of the curio coral, 95% of live rock, and 50-60% of the marine aquarium fishes each year (Wood, 2001; Bruckner, 2003). The most important sources of coral are currently Indonesia, Fiji, and Vietnam (Bruckner, 2001). Indonesia and the Philippines each supply about 30% of the total global trade in reef fishes, with another 30% exported from five locations (Brazil, the Maldives, Hawaii, Sri Lanka, and Vietnam); Florida and Puerto Rico are currently the largest exporters from the wider Caribbean (Wood, 2001; Balboa, 2002).

Although it is illegal to harvest stony corals and live rock in U.S. waters, ornamental reef fishes and many motile invertebrates are collected in U.S. waters both for domestic use and export. In Florida, 318 marine species (181 fishes and 137 invertebrates) have been collected for commercial purposes, with a total annual value of up to $4.2 million. Over 200,000 ornamental reef fishes are landed in Florida each year, with a maximum of 425,781 fishes in 1994 (Larkin, 2003). Annual reported harvest of ornamentals from West Hawaii rose from 90,000 in 1973 to 422,823 in 1995 (Tissot and Hallacher, 1999).

Of all physical damage caused to coral reefs by human activity, ship groundings and the impacts of boats and anchors are perhaps the most destructive. The U.S. Coast Guard (USCG) reports that over 2,100 grounding accidents are reported annually, with about 440 vessels sinking each year. In addition, over 800 abandoned barges litter the inland and coastal waters of the U.S., many still loaded with hazardous cargo. As recreational and commercial boating traffic increases in nearshore ocean waters, these shipwrecks pose a threat to coral reef habitat. When anchors, especially the enormous anchors of cruise ships, are carelessly dropped and dragged on fragile reef, hundreds of meters of habitat can be destroyed. Recent studies demonstrate the extensive impacts of groundings when hazardous cargo is released. However, once cargo and fuel are spilled, the vessel may continue to cause repeated physical damage to the reef due to movement by wind and waves. Furthermore, abandoned barges can often become illegal dump sites for other hazardous materials, trap wildlife, and become public safety hazards (Helton and Zelo, 2003).

Initially many considered the impacts of grounded vessels to be significant only at a local level, but the widespread effects of these events have recently been the subject of closer examination (Precht et al., 2001; Ebersole, 2001). Damage resulting from ship groundings often continues well beyond the initial event of impact as a result of slow recovery and fragmentation of keystone species essential to reef structure and function. In particular, spur and groove reefs do not seem to recover their diverse fish assemblages following a ship grounding incident (Ebersole, 2001). The potential threats of grounded vessels became the subject of increased political attention in 1999 when nine vessels were cleaned, cut apart, and removed from a reef in Pago Pago, American Samoa and the grounding sites were restored by the USCG, NOAA, and American Samoan government. The increasing frequency of vessel groundings in coral reef environments led to the development of the National Action Plan to Conserve Coral Reefs (USCRTF, 2000) which recognizes the impact of grounded vessels to coral reefs and their associated habitats (Helton and Zelo, 2003). In response, NOAA initiated the Abandoned Vessel Project, which seeks to increase awareness of abandoned vessels, particularly where they occur in coral reef systems, as well as provide the technical assistance necessary to remove the vessels (NOAA OR&R, http://response.restoration.noaa.gov/dac.vessels/overview.html, Accessed 6/2/04).

A study conducted on the site of the 1984 grounding of the M/V Wellwood in the Florida Keys National Marine Sanctuary suggested that damaged spur and groove habitat will take decades to recover without substantial restoration efforts (Smith et al., 1998). A reduction of topographic complexity also influences local hydrodynamics and the structure of reef fish and invertebrate communities (Miller et al., 1993; Szmant, 1997).

The damage caused to a coral reef habitat by boat anchors is an additional threat resulting from frequent boat traffic. A study conducted in a 220 ha area of coral reef in Fort Jefferson National Monument, Dry Tortugas, Florida documented the extensive damage that can be caused by anchors (Davis, 1977). Cruise ship anchors present a significant and increasing threat to coral reefs. In Grand Cayman, an estimated 1.2 million m2 of coral
reef have been destroyed by cruise ship anchors (Smith, 1998), while cruise ships in the Cancun National Park in Mexico, are thought to have impacted over 80% of the coral reefs there (Schultz, 1998). Designation of anchorages in less sensitive areas, installation of mooring buoys, and identification of areas sensitive to anchor damage are necessary to reduce the destructive practice of unregulated anchor dropping and dragging.

Major vessel groundings in the FKNMS such as the M/V Alec Owen Maitland and M/V Elpis in 1989 and the R/V Iselin in 1994 are examples of events in which waves and currents occuring between the grounding and restoration resulted in further injury to the reef. Loose coral rubble threatened adjacent undisturbed coral habitat, and restoration efforts involved removing broken pieces of coral from the seafloor and re-attaching them before the arrival of winter storms. The extent of the broken coral can be extensive. For example, the 325-foot M/V Fortuna Reefer container ship ran aground near Mona Island, Puerto Rico in July 1997 and damaged over 6,400 m2 of elkhorn coral (Zobrist, 1998).

Globally, marine debris presents a continuous threat to the marine environment. Marine debris adversely impacts marine life through the destruction of essential habitat as well as entanglement and ingestion by marine organisms and seabirds. Typically, the majority of marine debris comes from land-based sources, particularly urban centers, but a significant proportion comes from ships.

All U.S. jurisdictions with coral reefs participate in the International Coastal Cleanup to remove marine debris from their shorelines and nearshore waters. Additional community-based cleanup efforts have been conducted at many locations, including South Point and Kahoolawe in Hawaii. Typical debris collected from the shorelines includes beverage cans and bottles, cigarettes, disposable lighters, plastic utensils, food wrappers, and fishing line (Figure 3.9). Underwater cleanups conducted by snorkelers and divers have found similar materials beneath the surface. The most notable impacts of marine debris on coral reef ecosystems come from derelict fishing gear including nets, fishing line, and traps. Prior to the 1950s, fishing gear was composed of natural fibers, such as cotton and linen, and was susceptible to environmental degradation. Since the 1950s, fishing gear has primarily been constructed with synthetic materials, such as nylon and polyethylene, which is less susceptible to environmental degradation. Synthetic nets and fishing line can persist in the ocean for decades and can be transported for thousands of kilometers.

The NWHI has been a focal point for the removal of abandoned fishing gear comprised of conglomerates of netting and fishing line that roll across coral reef habitats, crushing corals and dislodging sessile organisms (Figure 3.10). Fishing gear frequently becomes snagged on corals and continues to trap fish ("ghost fishing") and endangered monk seals and sea turtles (Boland and Donohue, 2003; Donohue et al., 2001; Henderson, 2001; Balazs, 1985). Since 2001, NOAA’s Pacific Islands Fisheries Science Center, Coral Reef Ecosystem Division (PIFSC-CRED) has led a large-scale interagency partnership to study and remove derelict fishing gear from the NWHI. NOAA collaborates with the State of Hawaii, City and County of Honolulu, U.S. Fish and Wild life Service (USFWS), USCG, U.S. Navy, University of Hawaii, Hawaii Sea Grant, Hawaii Metals and Recycling, Honolulu Waste Disposal, and other partners from local agencies, businesses, and non-governmental organizations. From 2001 to 2004, this large-scale effort removed 401,055 kg of fishing gear from these remote islands and atolls. Types of fishing gear removed included monofilament gillnet, seine net, and trawl nets, the majority of which was thought to have originated from fisheries operating around the continental shelves of the North Pacific Rim which are located thousands of kilometers from the NWHI.

Derelict fishing gear has also been a concern in other U.S. coral reef ecosystems. (Chiappone et al. 2002) surveyed the Florida Keys for fishing gear and other marine debris and concluded that lobster trap debris was often found in offshore and mid-channel patch reefs, while hook and line gear was more common in shallow and deep forereef areas. Since 1994, the FKNMS, The Nature Conservancy, The Bacardi Foundation, and local dive operators have supported an annual effort to clean the reefs around the Florida Keys. In 2002, divers removed over 1,800 kg of marine debris including fishing line from the Keys. In 2003 and 2004, Amigos de Amoná, Inc. and other partners removed 3,235 kg of marine debris from the islands in Puerto Rico’s Mona Channel. The debris consisted of fishing gear (48%), plastics (13%), glass (14%), metal (8%), and miscellaneous items such as refrigerator doors, rubber shoes, packing and insulation materials, and washing machines (17%; Amigos de Amoná, Inc., 2004).

Reef managers from nine regions consider coastal development, runoff, and sedimentation major threats to their coral reef ecosystems (Table 2). These areas include coral reefs off large continental population centers and close-to-shore reefs off urbanized islands (Fig. 49). Near-shore reefs off high islands with relatively low human habitation⁵⁶ also experience substantial runoff and sedimentation during tropical storms.

In the United States, over 10.5 million people live in coastal counties and on islands near coral reefs, particularly in Florida, Puerto Rico, and much of the Main Hawaiian Islands. The Pacific Freely Associated States has another 203,000 island residents.

Infrastructure development is necessary to support coastal residents and the expanding reef tourism industry. This includes a myriad of activities: filling in wetlands to increase land area, dredging sand to replenish beaches, building causeways and bridges over existing reef habitats, dredging channels, erecting marinas and other support facilities along tidal shorelines, and destroying upland vegetation.

The impact of increasing human population on reef condition can be both acute and chronic. Reefs and related habitats suffer acute physical damage during construction, when such activities such as dredging to maintain deep-water draft for ships, erecting shoreside docks, and building marinas near or over coral reefs are in progress. The resulting runoff, plumes of sediment, and turbid (discolored, opaque) water from these activities can destroy a much broader area of reef habitat.

After coastal development is completed, the structures that were built and the activities related to them often have chronic, long-term impacts. These include increased treated sewage effluent, water pollution from all the chemicals necessary to maintain boats and other apparatus necessary for tourists, and storm runoff from paved surfaces. There is also contaminant-laden runoff from industrial and agricultural⁵⁷ operations (Fig. 50). All degrade and can destroy sensitive reef, seagrass, and mangrove habitats.

Compounding these problems, deforestation and stripping vegetation on high islands for agriculture and housing results in extensive land and river runoff during rainstorms. Chronic turbidity and silt deposition smothers sessile invertebrates, creating biologically barren areas. Large sediment plumes and turbid water from construction activities taking weeks or months to complete may substantially reduce the light to below the level needed for survival of coral reef plants for weeks or months. When water is turbid, light cannot penetrate as far down the water column, so the stony coral symbionts (the zooxanthellae) can only marginally survive, if at all, and coral bleaching results. Death of entire coral colonies may soon follow.

Besides runoff, there are additional concerns about seepage and current storm water control practices. Bacteria, disease, hormones, and other chemicals in the water potentially alter coral polyp development, inhibit successful settlement onto solid substrate, and even impact the social, territorial, and feeding behaviors of other reef organisms. Wide variations in salinity that damage near-shore reefs could become more commonplace if global climate brings more storms and flooding.

Beaches erode from storms and natural wave action. Dredging to replace sand on bathing beaches is a most destructive activity. Silt from dredging activities buries corals and suffocates sensitive reef organisms. Replenishment degrades water quality during the operation. Not only costly, it affects everything within the areas where the sand is taken from as well as where it is deposited, and must be repeated every 5-10 years.

On some Pacific coral reef islands and atolls, coastal development has been influenced by their long history as strategic staging areas for national defense. In the late 1930s, the Japanese British, French, Americans, New Zealanders, and Australians began to fortify many islands in the central Pacific with garrisons, airfields, docks, and airplane refueling stations. All of these changed the structure of adjacent reefs (Woodbury 1946, Dawson 1959, Maragos 1993).

Bases were established on many islands⁵⁸. While remnants of this construction remain, most reef populations have recovered. Battles and bombing raids during World War II also damaged reefs⁵⁹ (Maragos in Grigg and Birkeland 1997). Postwar reconstruction resulted in additional damage to reefs from dredging, filling, and causeway construction⁶⁰ (Brock et al. 1965, 1966). Ballistic missile testing at Johnston and Kwajalein stimulated additional construction, shore protection, and land reclamation (Maragos 1993, Smith and Henderson 1978).

Between 1946 and 1958, the United States used Enewetak and Bikini Atolls in the Marshall Islands to test 67 nuclear devices (National Biodiversity Team RMI 2000). Both the physical blast and the radioactivity damaged the land and shallow lagoons. The Bravo blast in 1954 sent millions of tons of sand, plant, and sea life from Bikini reef, three nearby islands⁶³, and surrounding lagoon waters high into the air. Radioactive fission products, particle-activated products, and unspent radioactive fuel contaminated the debris. This radioactivity entered the aquatic environment of the atolls (Donaldson et al. 1997, Simon 1997, Walker et al. 1997, Robison and Noshkin 1999, Niederthal 2001). And atmospheric nuclear fallout rained on the inhabited atolls of Rongelap and Utirik, the uninhabited atoll of Rongerik, and other downwind atolls. Part of the U.S. government’s radiological cleanup activities on Enewetak involved mixing part of the contaminated soil, mostly from Runit Island, with cement and submerging it in nearby Cactus Crater (formed by a nuclear explosion in 1958). The remainder of the soil was mixed with concrete and made into a dome above the crater. A non-contaminated concrete cap was then constructed over the dome. A National Academy of Sciences committee examined the dome and concluded that the containment structure and its contents presented no credible hazard to the people of Enewetak, either now or in the future (Noshkin and Robison 1997).

From the studies done to date, the RMI marine ecosystem is considered essentially recovered (N. Vander Velde pers. comm.). But the Marshall Islands land environment has not been totally restored, despite the government’s cleanup. The U.S. Department of Energy advises people not to visit Runit Island or the northern islands, which remain too radioactive because they were not included in the cleanup effort focused primarily on the three southern islands (G. Johnson pers. comm.). The southern islands are now inhabited and used for growing food.

The USEPA estimates that 60% of water pollution comes from non-point sources of contamination (input from a general area rather than a single point like a discharge pipe) such as storm-water runoff from urban areas and agriculture (Eichenberg 1999). More than 75% of the pollutants entering oceans are from non-point, land-based sources (YOTO 1998). Non-point pollution from agricultural operations and elsewhere, urban runoff, and even atmospheric discharges of soot and toxic chemicals can impact the diversity of reef wildlife. Agriculture is the leading source.