The Effects of the Harmful Algal Bloom Species Karenia brevis on Survival of Red Porgy (Pagrus pagrus) Larvae

Abstract

The harmful algal bloom species, Karenia brevis, forms annual, often intense blooms in the Gulf of Mexico, particularly along the west Florida shelf. Though the ability of K. brevis blooms to cause mass mortalities in juvenile fish are well documented, the direct effect of bloom concentrations on larval fish has not been studied extensively. To better understand the potential effect of K. brevis on larval fish survival, laboratory spawned red porgy (Pagrus pagrus) larvae from 4–26 days post-hatch were exposed to concentrations of K. brevis observed in the field for either 24 or 48 h. This species is representative of fish which spawn in regions of the Gulf of Mexico and whose larvae are epipelagic and may encounter K. brevis blooms. In this study, three different K. brevis strains varying in the amount of brevetoxin produced were tested. Larval survivorship was found to be inversely proportional to the amount of brevetoxin produced by each strain. The EC50 value from the combined 24 h experiments was ~163,000 K. brevis cells L−1, which corresponds to cell concentrations found in moderately dense blooms. Larval mortality also increased substantially in the 48 h versus 24 h exposure treatments. These findings indicate K. brevis blooms have the potential to contribute to natural mortality of fish larvae and further reduce inter-annual recruitment of fishery species whose stocks in the Gulf of Mexico may already be depleted.

Integrating satellite remote sensing into the standard operating procedure of a water utility

“…• Algal bloom: A proliferation of red or reddish-colored algae species might be the cause of the formation. Certain algae, like red tide algae (e.g., Karenia brevis), can create large formations with reddish hues that persist on the water surface [16].…”

Harmful Algae Impacting Aquatic Organisms: Recent Field and Laboratory Observations

“…Litaker et al investigated the acute survival of red porgy fish larvae, Pagrus pagrus, upon exposure to K. brevis , observing that larvae survival was inversely proportional to brevetoxin production and directly proportional to the exposure time (mortality at 48 h > 24 h). The effective concentration to kill 50% of the larvae (EC 50 ) was estimated at 163 cells mL −1 (24 h exposure); this concentration is equivalent to moderately dense K. brevis blooms, suggesting that moderate to dense blooms by K. brevis may impact fish stocks of ecological and commercial relevance in the Gulf of Mexico [ 30 ]. A previous study confirmed the sensitivity of the RTgill-W1 cells towards the two brevetoxins PbTx-2 and PbTx-3 purified from K. brevis , the karlotoxin KmTx-2 from the dinoflagellate Karlodinium veneficum , and paralytic shellfish toxins from Alexandrium spp.…”