James W. Fourqurean

Florida International University | FIU · Institute of Environment and Department of Biological Sciences

“Blue Carbon” initiatives have highlighted the significant role of seagrasses in organic carbon (C org) burial and sequestration. However, global databases on the extent of C org stocks in seagrass ecosystems are largely comprised of studies conducted in monospecific beds from a limited number of regions, thus potentially biasing global estimates....

Extreme climatic events can trigger abrupt and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under climate change, the impact of these events on many foundation species and the ecosystems they sup-po...

Efforts to conserve globally declining herbivorous green sea turtles have resulted in promising growth of some populations. These trends could significantly impact critical ecosystem services provided by seagrass meadows on which turtles feed. Expanding turtle populations could improve seagrass ecosystem health by removing seagrass biomass and prev...

Developing a framework for assessing interactions between multiple anthropogenic stressors remains an important goal in environmental research. In coastal ecosystems, the relative effects of aspects of global climate change (e.g. CO 2 concentrations) and localized stressors (e.g. eutrophication), in combination, have received limited attention. Usi...

The protection of organic carbon stored in forests is considered as an important method for mitigating climate change. Like terrestrial ecosystems, coastal ecosystems store large amounts of carbon, and there are initiatives to protect these ‘blue carbon’ stores. Organic carbon stocks in tidal salt marshes and mangroves have been estimated, but unce...

The particulate organic matter buried in carbonate-rich seagrass ecosystems is an important blue carbon reservoir. While carbonate sediments are affected by alkalinity produced or consumed in seagrass-mediated biogeochemical processes, little is known about the corresponding impact on organic matter. A portion of particulate organic matter is carbo...

One of the world’s largest “blue carbon” ecosystems, Louisiana’s tidal wetlands on the US Gulf of Mexico coast, is rapidly being lost. Louisiana’s strong legal, regulatory, and monitoring framework, developed for one of the world’s largest tidal wetland systems, provides an opportunity for a programmatic approach to blue carbon accreditation to sup...

Seagrass ecosystems are recognized as important carbon sinks that accumulate organic carbon (C org ) in their biomass and underlying soils. In Bermuda, seagrass meadows have declined precipitously over the last two decades, potentially leading to loss of those C org stocks. This study found 45% lower C org stocks in Bermuda (ca. 32.3°N) compared to...

The first record of Halophila stipulacea is reported for the continental waters of the United States. In August 2024, a small meadow was identified inside Crandon Marina on Key Biscayne, Florida, USA. Following surveys have revealed that H. stipulacea has spread to adjacent areas immediately outside of the marina, often growing either in close prox...

Carbonate-associated organic matter (CAOM) is the organic matter associated with carbonate minerals, and a survey of carbonate-rich surface sediments suggests that it is incorporated at a consistent amount scaling with the internal surface area of the carbonate grains. As the carbonate sediment is sensitive to changes in saturation state due to ben...

Plant microbiomes are known to serve several important functions for their host, and it is therefore important to understand their composition as well as the factors that may influence these microbial communities. The microbiome of Thalassia testudinum has only recently been explored, and studies to-date have primarily focused on characterizing the...

Climate change is altering the functioning of foundational ecosystems. While the direct effects of warming are expected to influence individual species, the indirect effects of warming on species interactions remain poorly understood. In marine systems, as tropical herbivores undergo poleward range expansion, they may change food web structure and...

The ability to accurately measure organic carbon (OC) in marine sediments or soils is overall taken for granted in scientific communities, yet this seemingly mundane task remains a methodological challenge when the soil matrix contains calcium carbonate (CaCO 3 ), creating inaccuracies in Blue Carbon estimates. Here, we compared five common methods...

The organic carbon (Corg) stored in seagrass meadows is globally significant and could be relevant in strategies to mitigate increasing CO2 concentration in the atmosphere. Most of that stored Corg is in the soils that underlie the seagrasses. We explored how seagrass and soil characteristics vary among seagrass meadows across the geographic range...

Although seagrass ecosystems are valued for the services they provide, anthropogenic impacts have led to global declines in seagrass area. South Florida harbors one of the most extensive and iconic seagrass landscapes in the world, but historic seagrass losses appeared to threaten their integrity. The establishment of the Florida Keys National Mari...

Our knowledge of the factors that can influence the stock of organic carbon (OC) that is stored in the soil of seagrass meadows is evolving, and several causal effects have been used to explain the variation of stocks observed at local to national scales. To gain a global‐scale appreciation of the drivers that cause variation in soil OC stocks, we...

Long-term “Blue Carbon” burial in seagrass meadows is complicated by other carbon and alkalinity exchanges that shape net carbon sequestration. We measured a suite of such processes, including denitrification, sulfur, and inorganic carbon cycling, and assessed their impact on air-water CO2 exchange in a typical seagrass meadow underlain by carbonat...

We estimated the net exchange of nitrogen and phosphorus species using core incubations under light and dark conditions in estuarine lakes that are the aquatic interface between the freshwater Everglades and marine Florida Bay. These lakes and adjacent shallow water Florida Bay environments are sites where the restoration of hydrological flows will...

Coastal vegetated habitats like seagrass meadows can mitigate anthropogenic carbon emissions by sequestering CO2 as “blue carbon” (BC). Already, some coastal ecosystems are actively managed to enhance BC storage, with associated BC stocks included in national greenhouse gas inventories. However, the extent to which BC burial fluxes are enhanced or...

Seagrasses are often considered important players in the global carbon cycle, due to their role in sequestering and protecting sedimentary organic matter as “Blue Carbon”. However, in shallow calcifying systems the ultimate role of seagrass meadows as a sink or source of atmospheric CO2 is complicated by carbonate precipitation and dissolution proc...

Extreme climatic events (ECEs) and predator removal represent some of the most widespread stressors to ecosystems. Though species interactions can alter ecological effects of climate change (and vice versa), it is less understood whether, when and how predator removal can interact with ECEs to exacerbate their effects. Understanding the circumstanc...

Susan Lynn Williams (1951–2018) was an exceptional marine ecologist whose research focused broadly on the ecology of benthic nearshore environments dominated by seagrasses, seaweeds, and coral reefs. She took an empirical approach founded in techniques of physiological ecology. Susan was committed to applying her research results to ocean managemen...

Long-term “blue carbon” burial in seagrass meadows is complicated by other carbon and alkalinity exchanges that shape net carbon sequestration. We measured a suite of such processes, including denitrification, sulfur, and inorganic carbon cycling, and assessed their impact on air-water carbon dioxide exchange in a typical seagrass meadow underlain...

Subtropical seagrass meadows play a major role in the coastal carbon cycle, but the nature of air–water CO2 exchanges over these ecosystems is still poorly understood. The complex physical forcing of air–water exchange in coastal waters challenges our ability to quantify bulk exchanges of CO2 and water (evaporation), emphasizing the need for direct...

The paradigm for understanding the accumulation of organic carbon in vegetated coastal “blue carbon” habitats holds that burial of organic carbon (Corg) slows decomposition and leads to stability of carbon stocks. Further, it is generally assumed that the presence of the plant communities contributes to the buried organic matter and the stability o...

The net ecosystem productivity (NEP) of two seagrass meadows within one of the largest seagrass ecosystems in the world, Florida Bay, was assessed using direct measurements over consecutive diel cycles during a short study in the fall of 2018. We report significant differences between NEP determined by dissolved inorganic carbon (NEPDIC) and by dis...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The term Blue Carbon (BC) was first coined a decade ago to describe the disproportionately large contribution of coastal vegetated ecosystems to global carbon sequestration. The role of BC in climate change mitigation and adaptation has now reached international prominence. To help prioritise future research, we assembled leading experts in the fie...

The condition of seagrass habitat and the marine environment on the Bermuda Platform, a mid-oceanic shallow water habitat in the northwest Atlantic, has been monitored since 2006. The overall oceanic climate of the Platform is subtropical; the Platform supports communities of tropical marine seagrasses, including Thalassia testudinum, Syringodium f...

Hurricanes are some of the largest environmental drivers of change in coastal systems. We investigated the impacts of Hurricane Irma on benthic macrophyte communities in Florida Bay (FB) and the Florida Keys National Marine Sanctuary (FKNMS), USA. Spatiotemporal analyses were performed at multiple hierarchical levels (site, zone, region) to identif...

A central question in contemporary ecology is how climate change will alter ecosystem structure and function across scales of space and time. Climate change has been shown to alter ecological patterns from individuals to ecosystems, often with negative implications for ecosystem functions and services. Furthermore, as climate change fuels more freq...

Water flow through seagrass beds transports nutrients, affects sediment stability and chemistry, and imposes hydrodynamic forces on shoots that alter canopy configuration. Past studies done under diverse conditions yielded conflicting results about the effects of shoot density on flow through seagrass bed canopies. We used eelgrass, Zostera marina,...

The condition of seagrass habitat and the marine environment on the Bermuda Platform, a mid-oceanic shallow water habitat in the northwest Atlantic, has been monitored since 2006. The overall oceanic climate of the Platform is subtropical; the Platform supports communities of tropical marine seagrasses, including Thalassia testudinum, Syringodium f...

A foraminiferal proxy for seagrass abundance was developed, tested and used to construct a record of seagrass variability for Florida Bay, USA, since its initial flooding ~ 3800 cal years BP. Of 76 species recorded in the Bay, 13 seagrass-associated foraminifera were identified based on previously observed occurrences in seagrass beds of the region...

The net ecosystem productivity (NEP) of two contrasting seagrass meadows within one of the largest seagrass ecosystems in the world, Florida Bay, was assessed using direct measurements over consecutive diel cycles. We report significant differences between NEP determined by dissolved inorganic carbon (NEPDIC) and by dissolved oxygen (NEPDO), likely...

Calcium carbonates (CaCO3) often accumulate in mangrove and seagrass sediments. As CaCO3 production emits CO2, there is concern that this may partially offset the role of Blue Carbon ecosystems as CO2 sinks through the burial of organic carbon (Corg). A global collection of data on inorganic carbon burial rates (Cinorg, 12% of CaCO3 mass) revealed...

Nutrient pollution and thermal stress constitute two of the main drivers of global change in the coastal oceans. While different studies have addressed the physiological effects and ecological consequences of these stressors in corals, the role of acquired modifications in the coral epigenome during acclimatory and adaptive responses remains unknow...

Future increases in oceanic carbon dioxide concentrations (CO2(aq)) may provide a benefit to submerged plants by alleviating photosynthetic carbon limitation. However, other environmental factors (for example, nutrient availability) may alter how seagrasses respond to CO2(aq) by regulating the supply of additional resources required to support grow...

Limiting climate warming to <2°C requires increased mitigation efforts, including land stewardship, whose potential in the United States is poorly understood. We quantified the potential of natural climate solutions (NCS)—21 conservation, restoration, and improved land management interventions on natural and agricultural lands—to increase carbon st...

Seagrass ecosystems were traditionally assumed to be structured by competition as well as by “bottom up forces” such as resource availability and disturbance. However, a wealth of new evidence demonstrates that exertion of “top down control” by animals may be widespread. The strength and direction of top down control is context dependent, however,...

Seagrass ecosystems contain globally significant organic carbon (C) stocks. However, climate change and increasing frequency of extreme events threaten their preservation. Shark Bay, Western Australia, has the largest C stock reported for a seagrass ecosystem, containing up to 1.3% of the total C stored within the top metre of seagrass sediments wo...

Corals host diverse microbial communities that are involved in acclimatization, pathogen defense, and nutrient cycling. Surveys of coral-associated microbes have been particularly directed toward Symbiodinium and bacteria. However, a holistic understanding of the total microbiome has been hindered by a lack of analyses bridging taxonomically dispar...

Supplemental Figure 1. Maximum likelihood phylogeny with the partial 16S rRNA gene showing the phylogenetic relation between bOTU1, the top BLAST hits and all SAR116 bacteria in the SILVA reference alignment, with the exception of KJ589655, HQ673528 and KF271096 which clustered outside of the SAR116 clade. SAR116 bacterial sequences acquired from s...

CP23S Reference Alignment.

MOTHUR Pipeline Analysis.

cp23S Reference Classification FASTA file.

cp23S Reference Classification Taxa.

Supplemental Figure 2. Maximum likelihood phylogeny with the partial 16S rRNA gene showing the phylogenetic relation between bOTU3 and clonal sequences from corals, Candidatus Lariskella, Candidatus Midichloria and other Rickettsiales genera. The optimal model (GTR+I+G) was selected based on the AIC criterion. The maximum likelihood analysis was co...

Green sea turtles (Chelonia mydas) arrive on the geographically isolated Bermuda Platform as small juveniles and remain until they are approaching sexual maturity, at which point individuals depart for distant feeding and nesting sites. It has been reported that younger green turtles generally tend to carnivory or omnivory and that seagrasses becom...

Seagrass ecosystems have been identified as long-term carbon sinks whose conservation could serve as a tool to mitigate carbon emissions. Seagrasses alter landscapes in a way that stimulates carbon biosequestration, but discussions of their role in atmospheric CO2 mitigation disregard the co-occurring inorganic carbon cycle, whose antagonist effect...

The sediments of coastal wetlands contain large stores of carbon which are vulnerable to oxidation once disturbed, resulting in high levels of CO2 emissions that may be avoided if coastal ecosystems are conserved or restored. We used a simple model to estimate CO2 emissions from mangrove forests, seagrass beds, and tidal marshes based on known deco...

Extreme temperature events are predicted to become more frequent and intense as climate change continues, with important implications for ecosystems. Accordingly, there has been growing interest in what drives resilience to climatic disturbances. When a disturbance overwhelms the resistance of an ecosystem, it becomes vulnerable during recovery, wi...