EMERGING AREA
Seagrass
A Seagrass Invasion
Seagrass meadows provide key ecosystems services including enhancing water quality, coastal protection from erosion, carbon storage, providing food for fishes, sea turtles, invertebrates and marine birds, and serving as nursery grounds for commercially important animals, such as the queen conch (Aliger gigas). Worldwide, the area covered by seagrass meadows has decreased dramatically during the past decades because of habitat degradation and climate change and some seagrass species appear headed endangered species status.
A Sargassum Invasion
Golden tides are abnormal massive coastal accumulations of floating seaweed in the genus Sargassum that form as a result of surface circulation patterns. The algae interfere with navigation and fishing; result in die-offs of seagrasses, fishes and endangered sea turtles; and affect tourism and human health as algal biomass decomposes releasing sulfides and decreasing the appeal of swimming areas.
Photo by Dan Mele
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A Seagrass Invasion
Seagrass meadows provide key ecosystems services including enhancing water quality, coastal protection from erosion, carbon storage, providing food for fishes, sea turtles, invertebrates and marine birds, and serving as nursery grounds for commercially important animals, such as the queen conch (Aliger gigas). Worldwide, the area covered by seagrass meadows has decreased dramatically during the past decades because of habitat degradation and climate change and some seagrass species appear headed endangered species status.
Alien Seagrass
One of our emerging research goals is to improve our understanding of the ecology of the invasive seagrass Halophila stipulacea in Virgin Islands coastal waters. Research activities include studies of the invasive grass’ distribution and expansion in relation to environmental conditions and biological components such as the distribution of herbivores. The team will identify the animals that live in the invasive grass and use it as food and habitat and, how they compare to those in native seagrass beds.
Photo: Dan Mele
The Ecology of an Invasion
A additional significant threat to Caribbean seagrasses has been the invasion of Halophila stipulacea. This short seagrass native to the Red Sea and Indian Ocean was first identified in Grenada in 2002. Since then, it has been recorded at more than 20 Caribbean islands and continental coasts. Relatively little is known about the mechanisms favoring transportation and establishment of this seagrass, or its effects on Caribbean community and ecosystem processes. Studies have shown a reduction in the cover of native Caribbean seagrasses and shifts in fish and invertebrate communities where H. stipulacea has colonized, but many other potential effects of the invader remain unknown. Emerging research in this area will expand on our current knowledge by studying the effects of this invasive seagrass on native herbivores, invertebrate communities, and the effects of increasing water temperatures on competition between the invader and Caribbean seagrasses.
This project will measure the spread of the invasive seagrass Halophila stipulacea in the USVI and explore some of the mechanisms affecting its expansion. In particular we will learn if Caribbean herbivores, such as urchins, some crabs, sea turtles, and queen conch, for example, eat the invasive seagrass. The project will also examine changes in the invertebrate communities among beds of different seagrass species, how these differences relate to seagrass bed stability and function, and measure how native seagrass growth rates relate to invasion by Halophila.
Previous Mare Nostrum EPSCoR grant studies showed little difference in total associated invertebrates when beds of the invasive seagrass were compared to those of the native Syringodium filiforme. Those surveys will be expanded under this project to assess if these patterns change over time. Joining Dr. Cruz-Rivera in the identification of these complex animal communities and in the training of potential future taxonomists from the VI will be Dr. D. Christopher Rogers from the Kansas Biological Survey and the Biodiversity Institute of the University of Kansas.
The project also will examine growth rates of various seagrasses in relation to projected ocean temperature increases. This works builds from a current EPSCoR collaboration with Dr. Jay Stachowicz (University of California at Davis) looking at the relations between seagrass genetics and heat waves on the outcome of competition between the temperate seagrass Zostera marina and green algae on the California coast.
Photo: Dan Mele
Sargassum
The Emerging Areas of Research Team is also working to advance our understanding of the large influxes of the floating brown algae called Sargassum that have been increasingly inundating Caribbean coasts. The recent changes in the increased amounts of the algae have had significant impacts on coastal tourism and fishing economies from Belize and Mexico to the southern islands in the Lesser Antilles. However, the ecology of this floating Sargassum algae is not well understood. The team will study whether the large increases are due to genetic shifts in open ocean algal communities and identify the impacts of the decomposing algae on coastal water quality and animal diversity.
Golden tides are abnormal massive coastal accumulations of floating seaweed in the genus Sargassum that form as a result of surface circulation patterns. The algae interfere with navigation and fishing; result in die-offs of seagrasses, fishes and endangered sea turtles; and affect tourism and human health as algal biomass decomposes releasing sulfides and decreasing the appeal of swimming areas.
Photo: Dan Mele
Beginning in 2011, various severe golden tides have affected the Caribbean and Gulf of Mexico with data suggesting that the frequency and intensity of these events will increase in the future. Small Caribbean islands, such as the US Virgin Islands, whose economies are especially dependent on tourism and artisanal fisheries, are the most vulnerable. Although the significance of the problems caused by golden tides is broadly acknowledged, the effects of these large-scale phenomena, including their local impacts, ultimate fate, and cascading effects on ecosystems are poorly understood. Many groups around the Caribbean are actively engaged in unraveling the causes of these events and how to manage them. This component of the R2R will address various interconnected questions regarding the accumulation of Sargassum in coastal habitats of the USVI.
Among the central questions that will be studied are how the increased accumulations of seaweed mass and their decomposition affect the distribution and diversity of beach animals, and the fluxes and dynamics of nutrients on the coast. Dr. D. Christopher Rogers from the Kansas Biological Survey and the Biodiversity Institute of the University of Kansas will provide his taxonomic and biogeographic expertise by collaborating with Dr. Cruz-Rivera and VI students in this research.
Recent studies have suggested that the type of Sargassum causing golden tides is an uncommon growth form not usually found in the open sea. Another focus of this research will be to measure the genetic diversity of floating Sargassum in golden tides of the USVI. This work will be done in collaboration with Dr. Stacy Krueger-Hadfield from the University of Alabama, Birmingham.
“The changes affecting the Caribbean do not recognize borders or affiliations. If we are to arrest or reverse some of these changes the efforts must be coordinated across disciplines and nations.”
– Dr. Edwin Cruz-Rivera
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Edwin Cruz-Rivera, Ph.D.
Project Lead
I am an ecologist with broad interests and a fondness for invertebrates. My research interests have been largely focused on consumer-prey interactions, especially on the nutritional and chemical ecology of marine invertebrate herbivores and their algal, plant and cyanobacterial foods. My studies combine natural history observations and manipulative experiments in the lab and field to assess how consumer feeding and fitness are related. I have done research in a broad variety of environments, including the temperate North Atlantic and North Pacific coasts, the Chesapeake Bay, the Mediterranean Sea, both sides of the tropical Pacific, South Australia, the Red Sea, the Caribbean, brackish lakes in Egypt, temporary freshwater bodies in the Virgin Islands, and the South African intertidal. Therefore, I have been able to address fundamental ecological and environmental questions in tropical and temperate, marine and freshwater ecosystems.