Marine Scientist Warns: Proposed Rosewood Exuma Dredging Would Destroy 1.6 Acres of Healthy Coral Reef

Dr. Craig Dahlgren, Executive Director of the Perry Institute for Marine Science, found on surveying the North Bay that:

• The overall impact of the project is likely to be “moderate to high”, and he warns the harm would not stay inside the dock’s footprint: “the proposed service dock construction and operation will have a significant impact in the North Bay ecosystem and the species residing there.” 
• The hardbottom reef in the channel is the healthiest and most productive reef in the North Bay and there is no version of Yntegra’s dredging plan for Rosewood Exuma that spares it
• Dahlgren estimates the project would permanently destroy more than 13% of all the hardbottom reef in North Bay - roughly 1.6 acres around the service dock and another 1.5 acres in the channel
• Yntegra’s own numbers suggest their plan to reliably contain dredging turbidity is “unlikely” to be successful - and warns of sediment plumes that could smother the ecosystem
• The North Bay conch population is close enough to the edge that even a moderate loss of habitat quality could set it on a path of long-term decline
• “The most significant long-term risk is not limited to localized habitat loss, but rather the disruption of the physical processes that maintain habitat quality and ecosystem function.”

Turtlegrass is publishing a series of expert witness reports on the Yntegra Group’s proposed Rosewood Exuma resort on Sampson Cay. Each was prepared by a highly qualified specialist for the legal proceedings now before the courts, and we are releasing summaries so the public can see what the evidence says. The first two came from ecologists who reviewed Yntegra’s paperwork - Andrew Baker, who called the Environmental Impact Assessment “deeply flawed” and ornithologist Mark Gash, who went through the same material and reached the same conclusions, calling the EIA “wholly inadequate”. The third report is different. Dr Craig Dahlgren got in the water and surveyed the North Bay himself.

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Who is Craig Dahlgren?

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Dr Craig Dahlgren has studied Bahamian marine ecosystems since 1992. He holds a PhD in marine science and is Executive Director of the Perry Institute for Marine Science and the Bahamas Undersea Research Foundation. He has authored 50 peer-reviewed publications - more than 40 of them on marine ecosystems in The Bahamas - along with more than 50 technical reports for marine resource management agencies. He did his doctoral research on juvenile Nassau grouper in the Exuma Cays, has trained more than 30 Bahamians in coral reef health assessment, and currently serves on the Bahamas National Protected Areas Steering Committee, chaired by the Office of the Prime Minister, and the Bahamas National Trust Science Advisory Committee. His field work was supported by Bahamian marine biologist Dr Krista Sherman, President of the Bahamas Academy of Sciences. Turtlegrass’s attorneys instructed him to give independent evidence to the Supreme Court and the Subdivision and Development Appeal Board. He records that he has “no financial or other interest in the outcome of these proceedings.”

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What Dahlgren was asked to assess

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Dahlgren was asked to assess the current state of the marine habitats in the North Bay at Big Sampson Cay, and the likely impact on them of Yntegra’s proposed service dock, dredged access channel, breakwater, jetty and marina. Dahlgren and his team went to the site and over two days in March 2026 they mapped 155 acres of the bay with a drone and surveyed the habitats and species underwater - counting corals, fish, conch and other marine life along measured transects. His report, delivered in June 2026, sets out what is actually there and what the project would do to it.

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A conch nursery already on the edge

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The seagrass beds along the East Beach hold a working population of queen conch. Dahlgren recorded between 41 and 333 conch per hectare, with adults, subadults and juveniles all present. The presence of juveniles show the bed is still a nursery, producing the next generation. However, this is a conch population close enough to the edge that even a moderate loss of habitat quality could set it on a path of long-term decline, said Dahlgren.

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Adult densities, he found, “fall near the lower bound of commonly cited thresholds required to sustain effective reproductive activity” - which makes the population, in his words, “viable but vulnerable to reductions in density.” Conch need clean, well-sorted sand and the steady water movement that keeps it clean. The project would slow that flow and let finer sediment settle, which is exactly the condition conch cannot tolerate. 

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“Given that observed conch densities in portions of the study area are near known reproductive thresholds, even moderate declines in habitat quality are expected to result in reduced reproductive output and long-term population instability” - Dr Craig Dahlgren. 

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A living reef and the healthiest part is what they would dig up

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The hardbottom reef in the channel is the richest part of the system and the Yntegra project as designed would take out the healthiest, most productive reef in North Bay first, says Dahlgren. At two reef sites Dahlgren’s team counted 388 fish from 29 species along their transects, and saw 25 more species besides, including Nassau grouper (mostly juveniles, but some mature adults), mutton snapper, spiny lobster and sea cucumbers.

“The rates of active disease I recorded in the North Bay - 3.1% of coral colonies overall - are low and indicate that these remain relatively healthy coral reefs of high conservation value”.

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Where the service dock that Yntegra is proposing would go was the one coral area in the whole survey that showed no sign of disease. It held the highest densities of long-spined sea urchins (Diadema antillarum) that Dahlgren found anywhere in the bay. These urchins are a keystone grazer, still recovering from a region-wide die-off, that keeps reefs clear of algae so young corals can settle. He also recorded large numbers of small, young Porites corals, a sign the reef there is actively regenerating. 

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More than 13% of the reef would be gone for good

Across the system, Dahlgren estimates the project would permanently destroy more than 13% of all the hardbottom reef in North Bay - roughly 1.6 acres around the service dock and another 1.5 acres in the channel. This, he writes, is not ordinary reef. It is “the most structurally complex and biodiverse component of the study area“ with “relatively healthy coral reefs of high conservation value.” His surveys recorded 17 species of stony coral, at least eight soft corals and 19 kinds of sponge, including slow-growing, reef-building Orbicella corals, among the threatened and endangered species in the system. And it is unusually healthy: only 3.1% of coral colonies showed active disease, which Dahlgren notes is “well below the current levels for most reefs in The Bahamas.”

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There is no version of the Yntegra plan that spares the best of the reef. Yntegra has floated several channel depths that it may dredge to - 7, 9, 10 and 12 feet. Dahlgren modelled all of them. The deeper the dredge, the more is lost, but one finding holds across every version: “the highest-value dense hardbottom habitat is impacted the most by dredging.” 

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The promise to contain the damage does not hold up

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Yntegra’s own numbers suggest their plan to reliably contain dredging turbidity is “unlikely”. Dahlgren notes that Yntegra say the dredging turbidity will be “maintained at a maximum of 29 NTU above background” using silt curtains and a cutter-suction dredger. Yet Yntegra’s engineers measured currents in the bay running up to 1.5 metres per second. Published US Environmental Protection Agency guidance puts the limit for free-floating silt curtains at around 0.15 metres per second - roughly a tenth of that. In his words, “it is unlikely that turbidity curtains would provide reliable containment at this site given the current velocities documented in the project’s own modelling,” and the EIA “does not demonstrate how the stated 29 NTU limit would be achieved.”

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A 2023 dredging operation off Celebration Cay on Grand Bahama offers a cautionary tale, notes Dahlgren. It sent a sediment plume nearly two miles down the shore despite a silt curtain - and, Dahlgren notes, the currents there are much weaker than at Big Sampson Cay. The image is freely available on Google Earth. Once fine sediment is loose in a fast-moving system like North Bay it does not stay put: it settles on seagrass, smothers filter-feeding sponges, and stresses the corals least able to cope with it.

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Stop the work and reconsider

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Dahlgren assesses the overall impact of the project as “moderate to high,” and warns the harm would not stay inside the dock’s footprint: “the proposed service dock construction and operation will have a significant impact in the North Bay ecosystem and the species residing there.” He also notes that the wider development reaches well beyond the bay — 88 residential lots and provision for 150 units of staff housing, a second marina, and dredging that would disturb the inner-lagoon flats where bonefish live and the fishing that depends on them.

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This is the third independent expert to examine Yntegra’s project and conclude it would do serious, lasting harm to North Bay. Dahlgren found a conch nursery near its limit, the healthiest reef in the bay set for removal, and a plan to contain the damage that the bay’s own currents will defeat.

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Dahlgren’s survey shows exactly what’s at stake when you trade an extraordinary, living place for a dock that could be built somewhere else. 

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Read the full report for yourself, and watch for the rest.

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