11th ICRS Abstract book - Nova Southeastern University

9-5
Evaluation Of Biotic And Abiotic Factors That Facilitate And Maintain
Cyanobacteria Blooms And Phase Shifts in Coral Communities
Kathleen SEMON* 1 , Valerie PAUL 1 , Mark CLEMENTZ 2 , John Michael TRAPP 3 ,
Karen ARTHUR 1
1 Smithsonian Marine Station at Fort Pierce, Smithsonian Institution, Fort Pierce, FL,
2 University of Wyoming, Laramie, WY, 3 Rosenstiel School, University of Miami,
Miami, FL
The functional stability of coral communities is currently threatened by recurrent
cyanobacteria blooms. Cyanobacteria, such as Lyngbya species, are known to displace
macroalgae in turf communities, inhibit coral recruitment through allelopathy, smother
invertebrates, and alter nutrient and light regimes. Because cyanobacteria blooms impact
many physical and biological characteristics of coral communities, damaged coral
communities face altered community structure and reduced biodiversity. This study
examined both the biotic and abiotic factors that facilitate and maintain cyanobacteria
across Florida and Caribbean coral communities. Lyngbya spp. tissue and water samples
were collected from areas known to be oligotrophic (the Belize Barrier Reef), and from
areas adjacent to high human density and under significant anthropogenic influence
(throughout south Florida). Stable C and N isotopic signatures reflect different sources
contributing to cyanobacteria presence in Belize and Florida, and differences in ambient
dissolved and total iron levels were reflected in patterns of cyanobacteria abundance.
Correlations of ambient nutrient and temperature regimes and cyanobacteria presence and
abundance were also examined from benthic surveys conducted in Belize. Multivariate
analyses conducted in PRIMER v.5 revealed that Lyngbya spp. presence alone
significantly influenced percent cover of stony coral and macroalgae recorded from
benthic transects conducted in Belize. Crucial thresholds for coral community phase
shifts are suggested based on data collected in situ and on preliminary data compiled by
experimentally manipulating nutrient regimes in mesocosms known to influence
cyanobacteria primary production and biomass accumulation.
9-6
The Role Of Nutrients In Lyngbya Growth And Chemical Defense
Karen ARTHUR* 1 , Valerie PAUL 1 , Cliff ROSS 2 , Hans PAERL 3 , Jennifer JOYNER 3 ,
Judith O'NEIL 4
1 Smithsonian Marine Station at Fort Pierce, Smithsonian Institute, Fort Pierce, FL,
2 Department of Biology, University of North Florida, Jacksonville, FL, 3 Institute of
Marine Sciences, The University of North Carolina at Chapel Hill, Morehead City, NC,
4 Center for Environmental Science, University of Maryland, Cambridge, MD
Benthic cyanobacteria of the genus Lyngbya form harmful algal blooms (HABs) that
occur on reefs and associated communities. They may be detrimental to other benthic
organisms as they can smother corals and seagrass and because they are extremely
prolific producers of biologically active secondary metabolites, many of which deter
grazing by generalist herbivores. Nuisance blooms of Lyngbya may be triggered by
terrigenous nutrient inputs and may grow unchecked as grazers avoid consuming the
filaments containing secondary metabolites. In this study we examine the ecology of
Lyngbya blooms in Broward Country, Florida and assess the effects of nutrient additions
and light on Lyngbya growth and toxin production. We use a bioassay approach to assess
the role of nitrogen, phosphorus, iron and low light conditions on the growth and
secondary metabolite production of three species of Lyngbya. A significant increase in
Lyngbya polychroa growth resulted from the addition of chelated iron; however, this was
not the case for all Lyngbya species. Lyngbya spp. are also sensitive to light availability,
with each species apparently having niche environments with specific light requirements.
This study demonstrates the need to manage nutrient inputs into coral reef habitats to
ensure that future reefs are not dominated by Lyngbya and other benthic cyanobacteria.
Oral Mini-Symposium 9: Chemical Ecology on Coral Reefs
9-7
Ecological Consequences Of Cyanobacterial Blooms On Coral Reefs
Valerie PAUL* 1 , Cliff ROSS 2 , Raphael RITSON-WILLIAMS 1 , Linda WALTERS 3 , Karen
ARTHUR 1 , Sarath GUNASEKERA 1 , Theresa MEICKLE 1
1 Smithsonian Marine Station, Smithsonian Institution, Fort Pierce, FL, 2 Department of Biology,
University of North Florida, Jacksonville, FL, 3 Department of Biology, University of Central
Florida, Orlando, FL
A major concern on coral reefs worldwide is massive overgrowth by macroalgae and benthic
cyanobacteria (blue-green algae). Benthic cyanobacteria are becoming increasingly abundant
on reefs and produce nitrogenous secondary metabolites that can deter feeding by generalist
herbivores. Nuisance blooms of Lyngbya and Symploca occur regularly throughout Florida and
on the Belizean barrier reef. Crude extracts from some of these cyanobacteria deter feeding by
a natural assemblage of fishes and the sea urchin, Diadema antillarum. In addition
cyanobacterial secondary metabolites may be important for competition, and the function of
allelopathy (chemical inhibition) in mediating the interactions between chemically rich species
of cyanobacteria and different life history stages of the coral Porites astreoides was tested.
Extracts and isolated compounds (microcolins A and B, curacin D) from Lyngbya spp.
negatively influenced the settlement and metamorphosis of P. astreoides larvae. On reefs
experiencing increased abundance of chemically defended benthic cyanobacteria, the restocking
of adult coral populations may be slowed due to recruitment inhibition caused by cyanobacterial
natural products. More research is needed on how to control these harmful algal blooms as
they become more common on coral reefs around the world.
9-8
The Good, the Bad, and the Smelly: Positive and Negative Settlement Cues for Coral
Larvae
Raphael RITSON-WILLIAMS* 1 , Valerie J. PAUL 1 , Suzanne ARNOLD 2 , Robert S.
STENECK 2 , Ilsa B. KUFFNER 3 , Linda J. WALTERS 4 , Mikel A. BECERRO 1,5
1 Smithsonian Marine Station at Fort Pierce, Fort Pierce, FL, 2 Darling Marine Center, University
of Maine, Walpole, ME, 3 Florida Integrated Science Center, U.S. Geological Survey, St.
Petersburg, FL, 4 Department of Biology, University of Central Florida, Orlando, FL, 5 Center for
Advanced Studies, Blanes, Spain
How algal species proliferate in reef habitats and how they maintain “phase shifts” are critical
questions to managing coral reef habitats. Some common reef algae (but not all) use chemical
defenses to inhibit grazing by Caribbean reef fishes and the sea urchin Diadema antillarum.
Algal natural products also mediate competitive interactions between algae and scleractinian
corals. Some species of Lyngbya and Dictyota, as well as crude chemical extracts of some of
these species, caused either recruitment inhibition or avoidance behavior in coral larvae.
Conversely, coralline algae may be important indicators of suitable settlement substrata for
coral larvae. The larvae of three spawning coral species, Acropora palmata, A. cervicornis and
Montastraea faveolata were tested in the laboratory for their rates of settlement in response to
different species of coralline algae. Some species of coralline algae were settlement facilitators,
such as Hydrolithon boergesenii, Neogoniolithon affine and Titanoderma prototypum, but every
coral species had the highest rates of settlement in response to a different species of coralline
algae. Increased herbivory by more generalist consumers may shift the benthic community
composition away from coral recruitment-inhibitors towards facilitators such as some species of
coralline algae, thus improving the benthos for higher rates of coral recruitment.
69