Harmful Algal Blooms - Amy Grogan

Harmful algal blooms, HABs, are a growing concern in South Carolina’s estuary systems. The South Carolina (SC) coastal zone is undergoing some of the most rapid urbanization in the country, including the development of thousands of stormwater detention ponds as catchments for runoff (Lewitus and Holland 2003; Lewitus et al. 2005, 2008; Keppler et al. 2006; Kempton et al. 2008). With HABs on the rise, efforts are needed to better understand harmful species and their effects on marine organisms.

In bloom event fish kills documented by the South Carolina Algal Ecology Lab, (SCAEL) the raphidophyte Chattonella subsalsa has been one of the most prominent causative agents (Lewitus et al. 2008). However the means by which C. subsalsa produces ichthyotoxic events remain enigmatic (Landsberg 2002). C. subsalsa is likely to impact fish via one of two mechanisms: i) copious production of mucus on fish gills causing physical blocking or clogging, or ii) production of a bioactive compound or toxin (Keppler et al. 2006, Bourdelais et al.2002). It is crucial to identify and understand the method of mortality caused by C. subsalsa in order to evaluate its potential effects on the environment and natural resources.

Several bioactive compounds have been found in cultures of raphidophytes: (i) reactive oxygen species (ROS), (Yang et al. 1995, Oda et al. 1997, Woo et al. 2006), (ii) brevetoxin/brevetoxin-like compounds (Khan et al. 1996a, Khan et al. 1996b, Khan et al. 1997 and Bourdelais et al. 2002), (iii) free fatty acids (FFAs) (Marshall et al. 2003), (iv) hemagglutinins and hemolysins (Onoue & Nozawa 1989). These bioactive compounds may be driving forces in fish deaths associated with C. subsalsa but none have been identified as the primary cause of mortality.

The lysis or consumption related breakage of algal cells may be necessary for such compounds to be released but it is also possible C.subsalsa actively releases a toxic substance(s). In this case two broad possibilities exist; (1.) mortality is dependent on physical contact with algal cells or (2.) C. subsalsa has the ability to produce water borne agents capable of inducing fish mortality without the necessity of contact. These possibilities must be examined to begin to determine the mechanism driving C.subsalsa fish kills.

My research aims to identify if physical contact with C. subsalsa cells is required to induce fish mortality by simulating a bloom scenario in a controlled laboratory setting using a common estuary fish, Fundulus heteroclitus.

Fundulus heteroclitus is found ubiquitously throughout the estuaries of the southeast. Its relatively small size and abundance in the salt marsh makes F. heteroclitus an ideal food source for a variety of predators. Both an influential predator and prey this fish is considered important in the transition of energy within the salt marsh ecosystem (Kneib 1986). Both its biological history and its extensive use as a laboratory subject make F. heteroclitus an ideal fish species for this study.

Adult F. heteroclitus were collected from field sites and bred in laboratory facilities. Larvae produced from breeding wild fish were used for exposure experiments. The use of larvae allows for larger sample populations due to size and space constraints, superior control of parameters such as temperature and light via the use of an environmental chamber, a captive fish population free of parasites and other environmental consequence, and a continuous supply of experiment subjects without excess field collections.

The effects of C. subsalsa will be determined via examination of gill tissue of exposed fishes. Examining gill tissue is regularly used as an indication of fish health and has been utilized as an effective measure of damage to fishes exposed to harmful algal species and a variety of environmental toxicants (Rodger et al. 1994, Landsberg 2002, Marshall et al. 2003, Deeds et al. 2006, Shen et al 2011). Gill damage and respiratory distress are the generalized causative agents of C. subsalsa fish kills thus experimentally exposed fishes are expected to have substantial gill injury (Bourdelais et al.2002, Deeds 2006, Shen et al 2011, Imai & Yamaguchi 2012).

With HABs on the rise the South Carolina Algal Ecology Lab is actively working to monitor blooms in order to gain a fuller understanding of their origins and repercussions. As human activities have a great influence on this issue, and many environmental issues, it is important to educate the public about practices to prevent harmful algal blooms. It is crucial to educate young minds about science and the role of society in preserving our natural resources. Working as a GK-12 fellow I hope to inspire students to care about our local ecosystems and learn the many ways they can help keep South Carolina healthy and beautiful. Understanding environmental health and the impacts of human activity will be a key skill for promoting a bright future!

Want to Learn More?!? Check out these links! NOAA Harmful Algal Blooms 10 Things You Can Do to Save the Ocean! Ocean Conservancy Be an Ocean Guardian

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