At high tide, Gulf Stream waters flow from the mouth of the Lake Worth Inlet and envelop Peanut Island in a gradient halo of of glistening turquoise, its waves lapping into one another as shattering sunlight dancing just under the glassy surface, fading into the churning sea green that recedes from the periphery of the island. What makes these brackish Intracoastal waters so crystal clear? How has Peanut Island adapted to and thrived in its unique surrounding environment? Answering these questions first requires an understanding of the local environment, the components that make up the ecosystem of Peanut Island, and the environmental restoration efforts that have been implemented to maintain the health of the marine ecosystem.

The Estuary Ecosystem

Peanut Island lies within the Lake Worth Lagoon, a 20-mile stretch from North Palm Beach to Ocean Ridge, separated from the Atlantic Ocean by barrier islands, where ocean water enters through the Lake Worth and Boynton Inlets and mixes with freshwater from flood control canals. The mixture of freshwater with saltwater creates what is called brackish water, but on a greater level, this also creates an entirely unique ecosystem—the estuary. The estuary intersects with the Intracoastal Waterway, which is a network of channels, rivers, canals, and other bodies of water comprising the inland waters running along the Atlantic coast. As an estuary ecosystem, the Lake Worth Lagoon is a critical resource and habitat to local plants and animals.

So, how are the waters of Peanut Island so clear for brackish waters? The answer lies in Peanut Island’s location within the Lake Worth Lagoon. Peanut Island is situated at the mouth of the Lake Worth Inlet, which is one of two inlets that provide saltwater to the Lake Worth Lagoon. This means that Peanut Island is on the receiving end of a constant influx of ocean water, and as tide levels fluctuate throughout the day, high tide brings high visibility and crystal clear conditions. While the strategic location of Peanut Island yields advantages, the island is presented with its own set of challenges. That’s where environmental engineers factor in—restoration efforts are necessary to maintain the environment of Peanut Island, a man-made island, to adapt and thrive in the estuary ecosystem.

The Peanut Island Environmental Enhancement Project

Before the US Army Corps of Engineers intervened to restore, maintain, and preserve critical elements of the estuary ecosystem at Peanut Island, the island was overrun with non-native, invasive species, like the Australian Pine tree, that hindered the survival of native plant species that are necessary for the ecosystem to thrive. Thus, the US Army Corps of Engineers were contracted to implement the Peanut Island Enhancement Project in 2003, which removed over 60 acres of invasive non-native vegetation, created over 30 acres of native wildlife habitat, and, ultimately, transformed the dredged sand island into a richly biodiverse actor within the estuary ecosystem of the Lake Worth Lagoon. The habitat enhancement project replaced the Australian Pine trees with native and natural vegetation like gumbo limbo, seagrape, cabbage palm, sea-lavender, and railroad vine to replenish maritime hammock, dune habitat, and coastal strand habitat. The project also created the man-man reef system with rock ledges for fisheries to promote biodiversity, breakwaters and jetties to protect the coastline from erosion, and flushing tidal channels to maintain the mangrove system.

Man-Made Reefs

The reefs situated along the eastern side of Peanut Island are not naturally formed, but rather the product of local habitat restoration efforts throughout the Lake Worth Lagoon. Peanut Island itself was man-made in 1918, and so it should come as no surprise that its reefs and snorkeling lagoon are also man-made. The man-made reef systems were created under the Peanut Island Enhancement Project in 2003 and have been improved by revitalization projects over the years. Palm Beach County Environmental Resources Management and the U.S. Army Corps of Engineers initially contracted Coastal Systems International, Inc. to design the island’s snorkeling areas, which include “the creation of a 1.5-acre artificial reef habitat hydraulically connected to Lake Worth Lagoon on the seaward side and a 1.3-acre shallow water seagrass lagoon on the landward side.”

How was this feat possible? Coral reefs are naturally formed when coral larvae attach to underwater surfaces like rocks, and over time coral polyps colonize to construct entire coral reefs. The process of creating artificial reefs requires the installation of submerged surfaces for coral larvae to populate on, stimulating the natural development of coral reefs from man-made habitats. Artificial reefs are made from materials like concrete, steel, limestone, and rocks. As detailed in a report by Palm Beach County Environmental Resources Management, “Several habitat and snorkel reefs were part of the Peanut Island redevelopment. Limerock boulders provide breakwaters and reef habitat on the eastern side of the island, and limerock boulders were used to create reefs in the swimming/snorkel area.” Additionally, the artificial reefs and jetties function as critical coastal infrastructure to prevent coastal erosion and protect the island from currents, tides, and storm surges. The limestone rock structures and the jetty’s rocky outcroppings serve as breakwaters by buffering and redirecting the force of waves.

While Peanut Island’s artificial reefs are made from limestone, artificial reefs can be constructed from many types of structures. The field of coral restoration has gotten creative, as coral biologists frequently deposit recycled structures to encourage the growth of marine habitats, like sunken ships or construction debris. This has been observed to the north of Peanut Island in Phil Foster Park’s underwater snorkeling trail, another restoration project by Palm Beach County Environmental Resources Management, which features hammerhead shark statues, shipwrecks, and even shopping carts—a prosaic symbol of consumerism transformed into a bastion of environmental sustainability.

Peanut Island’s artificial reefs are instrumental in maintaining the health of the ecosystem. The submerged surfaces provide critical habitat for the propagation of coral colonies, which in-turn stimulates biodiversity, attracting a rich variety of marine species to the island. The health of any reef is indicated by its biodiversity and balanced trophic distribution. Trophic levels are essentially levels of the food chain, and balanced trophic levels are integral to the sustainability of the coral reef ecosystem. For example, the nutrient-rich producers of the reef like algae, phytoplankton, seaweed, called autotrophs, sustain coral, small fish, and invertebrates of low trophic levels, and consumers within high trophic levels, like bigger fish and sharks, eat those within the lower trophic levels to provide control over growing populations and ensure that certain levels don’t overpopulate, deplete resources, and threaten the sustainability of the reef in a process known as trophic cascade.

Biodiversity has been observed on Peanut Island through the prevalence of species representing all the trophic levels. According to The Reef Institute, a local coral conservation organization committed to environmental stewardship and the sustainability of local marine ecosystems, “the amount of marine life species inhabiting the lagoon alone is staggering and rivals that of natural reefs in the Florida Keys.” The Reef Institute has recorded over 18 species of coral on Peanut Island, which represents nearly “half of the most common reef-building coral species found in Palm Beach County,” including “several species that are rarely found this far north.” In terms of higher trophic levels, the Peanut Island Environmental Enhancement project monitored the reefs in 2007, 2008, and 2012, and Engineering With Nature reports that the US Army Corps of Engineers recorded 26 families and 63 species of fish on the island’s reefs, with grunts and parrotfish accounting for the most represented species. Additionally, The Reef Institute has compiled a catalog of marine species observed on Peanut Island, which ranges from fish of lower trophic levels, like sergeant major, to those of higher levels, like the majestic spotted eagle ray.

Mangrove Boardwalk

Mangroves are vital components of the Lake Worth Lagoon’s estuary ecosystem, and as a natural resource in coastal infrastructure, they provide critical habitat and nurseries for marine species like lemon sharks, prevent coastal erosion, and stabilize water quality as sediments are trapped and nutrients are absorbed by the plant. Mangroves are unique to tidal estuaries because they can withstand volatile water conditions as the freshwater to saltwater ratio changes and salinity concentrations fluctuate at semidiurnal intervals with the tides. In order to take advantage of the natural benefits and eco-services provided by mangroves, non-native invasive vegetation was removed from the island and replaced with local alternatives like mangroves. The Peanut Island Environmental Enhancement Project saw the installation of a 230-foot mangrove boardwalk, which allows visitors to marvel at the estuarine habitat. However, as the mangroves were intentionally planted in a man-made mangrove community, additional systems were required to sustain the mangroves and facilitate natural tidal conditions. This was achieved through another environmental engineering system by Coastal Systems International, Inc. for Palm Beach County Environmental Resources Management, which includes “a tidal pond and flushing channel system to provide more adequate tidal flushing and seawater inundation to an existing mangrove community.” This ensures that the mangroves can cycle through a constant flow of brackish intracoastal water, which is then synthesized by mangroves as nutrients are absorbed.

The eco-services facilitated by the Peanut Island Environmental Enhancement Project, through the creation of artificial reefs and mangrove systems, serve as a testament to the resilience of the island as it has adapted to and thrived in its unique position within the Lake Worth Lagoon.