University of North Florida

As coral reefs across the Caribbean decline in coral cover, larval recruitment is undoubtedly a key process that can promote the recovery of reef communities. Many stressors (both abiotic and biotic) have a direct effect on coral reef community structure by catalyzing mortality and promoting a loss of reproductive viability. Offhand we usually think of the environmental impacts on adult corals. But what about the larvae?..no larvae-no adults.
Coral larvae have a planktonic period prior to settlement and so are exposed to multiple stressors in the water column before they settle to the benthos and metamorphose. Our current research, in collaboration with the Smithsonian Marine Station and Mote Marine Laboratory, is focused on examining the impacts of sublethal (and at times lethal) stressors on coral larvae.
One such current project is entitled: Impacts of Red Tides and Associated Toxins on Scleractinian Coral Health and Settlement.
Toxic red tides (harmful algal blooms, HABs), caused by the dinoflagellate, Karenia brevis, occur annually along the Florida Gulf coast. Commonly referred to as the Florida Red Tide, these blooms occur most frequently along the south and southwest Florida coast with impacts that vary from minor blooms to intensive blooms that can persist up to 18 months. These blooms frequently pass through the Florida Keys (Fig. 1) as they are entrained into the Florida Current and Gulf Stream and transported into the north Atlantic. Although always present in low concentrations throughout the Gulf with no apparent adverse effects, high concentrations (blooms) of K. brevis produce sufficient neurotoxins (brevetoxins) to cause human and environmental impacts including massive fish kills, marinemammal, sea turtle and sea bird mortalities and benthic community die-offs.

Fig. 1) December, 2005 representative maps of the state of Florida and Florida Keys red tide monitoring stations (obtained from Florida Fish and Wildlife Research Institute & Mote Marine Tropical Research Laboratory)
While much work has examined the effects of K. brevis blooms or exposure of brevetoxins on a diverse array of higher organisms, there have been no reports studying the impact of K. brevis on coral reef physiology. In particular, it is not known if blooms of K. brevis can compromise the cellular integrity of coral larvae thus reducing settlement and recruitment. The basis for this research is to study the effects of live K. brevis and extracted biotoxins on larval settlement using the coral Porites astreoides as a model system. As a subsequent component, the stress responses of exposed coral larvae are evaluated by commercially available cell diagnostic assays. By measuring a suite of stress indices we can evaluate not only whether the larvae are stressed but also which cellular functions are impacted by K. brevis blooms. This will allow us to determine if K. brevis blooms are capable of impacting coral larvae to the extent that they are no longer viable for settlement and metamorphosis. Studies were conducted in May 2007 & 2008 at the Mote Marine Tropical Research Laboratory (TRL) at Summerland Key, FL.
	Waiting for slack tide prior to sample collection
	Collecting Stypopodium zonale (another study…. entitled the impact of algae on hair displacement)
	In between dives……
	Probably a Killer Whale (or giant squid)
	Adult colonies of Porites astreoides being cleaned of epiphytes back at Mote Marine lab
	Adults acclimating prior to larval release (each colony averages between 15-20cm in diameter)
	University of Florida Graduate student Jason Kwan (left) and University of North Florida Undergraduate researcher Brad Bullington (right) setting up plumbing for water tables.
	Each adult colony rests in a mixing bowl and contains an independent water source. The idea is that once larvae are released they’ll flow out the spout into the collection apparatus (bottom of pic). If you look (very) carefully you can see ~300 larvae. Each one is about 1mm in length.
	On a good night you can obtain ~18,000 larvae. How do we know……?
	Welcome to Coral boot camp (the counting begins……)
	…..and keeps going (idle conversation soon runs thin) Someone in this pic is not even counting! (He can’t believe he spent the day counting 7,000 larvae)
	…..they’re dropping like flies (the counters)
	Stock culture of Karenia brevis provided by Mote Marine Laboratory Center of Ecotoxicology
Post exposure (24 hours), samples are assayed for their settlement ability	Larvae samples were subjected to varying concentrations of K. brevis and associated brevetoxins (to determine if there is a biological vs. chemical effect on larval health). Incubation treatments include: (1) 1 x 105 cells L-1 (considered low bloom conditions); (2) 6 x 106 cells L-1 (considered high bloom conditions); (3) Low bloom count-lysed by ultrasonication; (4) High bloom count-lysed by ultrasonication; (5) Control (no exposure to K. brevis) [n=10 per treatment]
	Cliff Ross (UNF) and Dr. Valerie Paul (SMS) setting up settlement assays
A single (pre-conditioned) terracotta tile is used as a substrate.	Question: Post-exposure, what percent of surviving larvae can still settle?
	Settled larvae (spat) are counted (you become very good at counting on these trips)
Settled larvae	Post-incubation, Erich Bartels (Mote) extracting brevetoxin analogs from larval samples to measure actual exposure concentrations
Post-incubation, Jason measures larval oxygen consumption with a Hansatech Oxygraph System	Porites astreoides (mustard hill coral) colony. Inset: a single larva magnified x400 (note presence of zooxanthellae)