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Carbonate mud represents one of the most important geochemical archives for reconstructing ancient climatic, environmental, and evolutionary change from the rock record. Mud also represents a major sink in the global carbon cycle. Yet, there remains no consensus about how and where carbonate mud is formed. Here, we present stable isotope and trace-element data from carbonate constituents in the Bahamas, including ooids, corals, foraminifera, and algae. We use geochemical fingerprinting to demonstrate that carbonate mud cannot be sourced from the abrasion and mixture of any combination of these macroscopic grains. Instead, an inverse Bayesian mixing model requires the presence of an additional aragonite source. We posit that this source represents a direct seawater precipitate. We use geological and geochemical data to show that "whitings" are unlikely to be the dominant source of this precipitate and, instead, present a model for mud precipitation on the bank margins that can explain the geographical distribution, clumped-isotope thermometry, and stable isotope signature of carbonate mud. Next, we address the enigma of why mud and ooids are so abundant in the Bahamas, yet so rare in the rest of the world: Mediterranean outflow feeds the Bahamas with the most alkaline waters in the modern ocean (>99.7th-percentile). Such high alkalinity appears to be a prerequisite for the nonskeletal carbonate factory because, when Mediterranean outflow was reduced in the Miocene, Bahamian carbonate export ceased for 3-million-years. Finally, we show how shutting off and turning on the shallow carbonate factory can send ripples through the global climate system.

Black corals (Hexacorallia: Antipatharia) are a major component of mesophotic and deep marine ecosystems. Due to their preference for light deprived environments, black corals have historically been considered azooxanthellate, yet recent works have found them in association with dinoflagellates of the family Symbiodiniaceae down to 396 m depth. While corals and Symbiodiniaceae generally establish a symbiotic relationship in shallow water environments, the implications of this association is less well understood at deeper depths, where low light penetration cannot sustain efficient photosynthetic activity for the algae. However, Symbiodinaceae are not obligate autotrophs, and their capacity for heterotrophic feeding categorizes themas mixotrophs. In this study, we investigated the presence and diversity of Symbiodiniaceae associated with the deep-sea black coral Bathypathes thermophila (Antipatharia: Schizopathidae), collected from 204 to 655 m depth in the Saudi Arabian Red Sea. Using high-throughput sequencing of the ITS2 region, we report (1) the deepest record to date of Symbiodiniaceae associated with an anthozoan from 655 m, and (2) the first Red Sea record of Antipatharia in association with Symbiodiniaceae. Our analyses revealed that 14 out of 27 colonies of B. thermophila were associated with Symbiodiniaceae of the genera Cladocopium and Durusdinium. We unveiled 16 novel ITS2 type profiles, possibly unique to black corals and/or to these depths, along with seven profiles that were already known from shallow-water hard corals. No significant pattern was detected in terms of community diversity in relation to depth or sampling locality. Our study supports the existence of black corals-Symbiodiniaceae association and warrants further research to better understand the evolutionary processes and physiological mechanisms driving this association, specifically in light deprived environments. [ABSTRACT FROM AUTHOR]

Suspension is the key mechanism by which fine‐grained sediment (≤125 μm) is winnowed and transported across shallow‐water carbonate platforms into adjacent deep waters. Unlike sliding and saltation, which deliver sedimentary structures via bedload, the sedimentological signature of suspended sediment is more cryptic. This study focuses on suspended sediment, and its drivers – wind, waves and tides – to better constrain the processes responsible for the transport of fine‐grained sediments. By building forward from remote sensing algorithms developed for deep‐waters, sediment suspension in the shallow water column can be mapped from satellite. By applying machine learning to Moderate Resolution Imaging Spectroradiometer data for Great Bahama Bank, this study demonstrates how the drivers of sediment suspension change over 18 years across this 100 000 km2 carbonate platform. Through time, both seasonal patterns of suspension, as well as those induced by El Niño‐Southern Oscillation and, more subtly, the Atlantic Meridional Overturning Circulation were tracked. El Niño‐Southern Oscillation modulates wind‐induced currents, while Atlantic Meridional Overturning Circulation affects local sea level. Across space, this study shows how the eastern margin of Great Bahama Bank, which is traditionally considered to be wind‐dominated, primarily owes its suspended sediment to tidal currents focused between islands. Sediment suspension across the leeward margin of Great Bahama Bank, meanwhile, can be attributed to wind‐induced currents and waves. The authors consider this work a step towards delivering a quantitative, reproducible, process‐based understanding of sediment suspension atop carbonate platforms using Earth observation data. [ABSTRACT FROM AUTHOR]

The Florida Keys comprise a unique ecological and archaeological setting in the southeastern United States yet have remained relatively understudied archaeologically for much of the twentieth century. Anecdotal accounts of "Spanish wells," employed by sailors and settlers during the colonial and early modern eras, have long posed questions about the availability of freshwater resources to Indigenous communities in the islands and how this availability may have impacted settlement patterns. Herein, we conduct the first systematic investigation of the "Spanish wells" in English-language historical records and compare their descriptions and locations to those of known Indigenous archaeological sites in the archipelago. In total, 22 distinct water sources in and near the Keys were attested to in documents and personal accounts from 1601 CE to 2021 CE. Geospatial analysis of their distribution relative to local archaeological sites returned few statistically significant results, however, likely influenced by the extensive history of site loss in the region. While the exact nature of most "wells" remains unclear, descriptions of their reliability and their broad spatial distribution bolsters the possibility of these water resources supporting year-round Indigenous communities in the archipelago prior to colonization. Future investigation focused on the identified water sources could shed further light on their exact nature and possible exploitation by Indigenous communities. [ABSTRACT FROM AUTHOR]

Profound changes in Earth's biogeochemical cycles are recorded in the sedimentology and geochemistry of carbonate sediments, with much of the early geological history of our planet recorded in carbonate mud precipitated from seawater. Despite their relevance for understanding early Earth, the trigger for whitings—carbonate spontaneously precipitated from the water column—remains intensely debated. Here, we used a neural network to map whitings imaged by daily MODIS Aqua satellite overpasses between 2003 and 2018 on Great Bahama Bank (GBB). Our results show that the frequency of whitings after 2011 increased by 3.3× compared to those recorded between 2003 and 2010, with the frequency of winter whitings increasing more than those in the summer. We contend that the period of increased whitings frequency was spurred by concurrent perturbations to the North Atlantic Oscillation, Atlantic Multidecadal Oscillation, and the El Niño Southern Oscillation in 2010 that facilitated enhanced hydrodynamic mixing between the waters atop GBB and those that surround it. We conclude that whitings can exhibit a sensitive but non‐linear response to ocean‐atmosphere dynamics which is unlikely to be resolved in the geological record using conventional stratigraphic techniques. This pronounced fluctuation in mud production on short timescales contrasts with expectations of persistent tranquility in the depositional environments that produce lime mud. Our results suggest that long‐established links between ocean‐atmosphere dynamics and the lime mud budget through Earth history may require reevaluation. Plain Language Summary: The size, composition, and distribution of carbonate sediment produced in the oceans are quantifiable features that enable reconstructions of environmental conditions throughout Earth history. Lime mud is a fine‐grained carbonate sediment that is commonly found in ancient rocks, but relatively rare in the modern oceans. However, Great Bahama Bank (GBB) has significant accumulations of lime mud thought to be produced by ongoing whitings. Whitings are a geological phenomenon that can be observed from orbit as milky white patches of seawater. Using a combination of satellite‐based remote sensing observations and deep learning, we created a two‐decade record of the frequency of whitings. Our results show, for the first time, that a pronounced change in ocean‐atmosphere dynamics more than tripled the frequency of whitings on GBB. Conventional geological methods cannot resolve such short‐time scale dependencies, so our study of modern lime mud formation provides useful insights into processes that happened in the ancient geological record, facilitating more accurate interpretations of environmental conditions throughout Earth history. Key Points: A perturbation to North Atlantic ocean‐climate dynamics in 2010 spurred a 3.3× increase in whitings lime mud productionLime mud production by whitings responds non‐linearly and disproportionately to subtle ocean‐atmosphere interactions on decadal timescalesClimate control on lime mud production provides new insight into one of the principal sedimentary archives of Earth's biogeochemical cycles [ABSTRACT FROM AUTHOR]

Marine ecological services provide goods, amenities, food resources, and economic benefits to millions of people globally. The loss of these services, attributed to the infiltration of marine invasive species such as the Indo-Pacific lionfish (Pterois volitans/miles), is measurable. The highly successful lionfish now flourishes in great densities in the US Gulf of Mexico and Atlantic waters and the entire Caribbean, yet the loss of ecological services attributed to the invader has not yet been assessed. In this study, we employ a derivative of a well-utilized method of ecosystem valuation known as habitat equivalency analysis to measure the time-value-adjusted loss of biomass- and recruitment-related ecosystem services brought by lionfish to Bahamian reefs. Drawing upon the literature examples of tangible lionfish damages in the Bahamas, we (1) quantitatively evaluate the loss of ecosystem services instigated by lionfish by measuring the total service-year losses partitioned over yearly time steps, (2) provide a metric by which ocean managers may value the remunerations of Bahamian lionfish controls when weighed against removal costs, and (3) deliver a tool to quantify changes in ecosystem services as a consequence of invasive species impacts and control. We found that the invader imposed losses of 26.67 and 21.67 years to recruitment and biomass services per km.sup.2 of Bahamian reef if left uncontrolled. In the same accord, the most conservative Bahamian lionfish removal regime modeled, i.e., which produced a 50 % recovery of pre-lionfish ecosystem function over 10 years, provided service gains of 9.57 and 4.78 years per km.sup.2. These data deliver a platform upon which to quantify present and future fiscal costs of the lionfish invasion and also to value lionfish control efforts., Author(s): Matthew W. Johnston[sup.1], Sam J. Purkis[sup.2], Richard E. Dodge[sup.2] Author Affiliations: (1) National Coral Reef Institute, Guy Harvey Research Institute, Halmos College of Natural Sciences and Oceanography, Nova Southeastern [...]