Written by Emilie Wood, Writer and Event Coordinator, UCSB Living Lab
Every student fears the cold and flu season – an hour spent sitting in a lecture hall echoing with coughs, sniffles, and sneezes feels like a lifetime. It is experiences like these that teach us to think quite negatively about parasites and pathogens. We believe our vigilant use of hand sanitizers will protect us from these nasty, infectious bugs. However, not everyone views parasites with such disdain. These incredible creatures are not very well understood, and researchers like Dr. Kevin Lafferty at UCSB are attempting to understand the complex role of parasites.
Dr. Lafferty has somewhat of a love affair with Santa Barbara and the surrounding environment. After completing his bachelor degree at UCSB in aquatic biology thirty years ago, he stayed on to pursue a Masters in zoology and then completed his PhD in ecology. Now advising his own PhD students, Dr. Lafferty has come to focus on parasitic relationships and their role in ecosystems.
Dr. Lafferty explains that parasites are incredibly understudied; in fact, most conservation biology textbooks completely leave out any discussion of parasites and their impacts on ecosystems. “Disease is considered mostly from the view of a wildlife veterinarian who focuses on diagnosis and treatment as opposed to ecology and evolution,” Dr. Lafferty states. He holds a unique view regarding parasites, insofar as he urges us to think about the importance of infectious diseases for conservation. He argues that parasites can give us insight into environmental degradation, acting as an ironic indicator of biological health in a system. With increasing stressors on ecosystems, such as climate change and biodiversity loss, we can use parasites to monitor the effects on ecosystems. “Stressors change complex systems in ways that there can be winners and losers. For instance, warming will generally disfavor the local organisms and favor those from lower latitudes; we should see some parasites increase and others decline, depending on location,” Dr. Lafferty clarifies. As we continue to burn fossil fuels and develop more land for agriculture and urbanization, we increase the stress on these ecosystems and, therefore, shift the host/parasite relationships. But how do parasites really impact ecosystems in the first place?
Parasites are the major part of biodiversity in ecosystems (in terms of species diversity), and some parasites regulate host species populations. Dr. Lafferty gave us some examples of the importance of parasites by stating, “Some parasites are pretty spectacular – the nematode that lives in the ovary of the sperm whale is dozens of feet long! And others help regulate populations of things we don’t like in large numbers, such as flies and mosquitos. So, some parasites do our bidding for us.” In addition, parasites can make it easier for predators to catch their prey, a factor which can alter the food web of certain ecosystems.
One specific industry that currently uses parasites to monitor ecosystem health is fisheries. In a recent paper titled “How have fisheries affected parasite communities,” Dr. Lafferty expands on this idea of parasitic biodiversity and ecosystem monitoring. In most fisheries, only fish over a certain size can be legally caught, creating an ecosystem missing its oldest and largest members. “Many parasites accumulate over time in a host, so when you catch a big fish, you remove it and years worth of parasite colonists. And, when a fish host becomes rare, it is harder for parasites to find them, leading to local parasite extinction,” Dr. Lafferty adds. Some of his research focuses on a shark tapeworm that uses reef fish as an intermediate host. If Dr. Lafferty sees an abundance of larval tapeworms in a collection of reef fish, that is a clear indicator that many sharks use that reef. If you are interested in preserving the health of fisheries, try to avoid purchasing long-lived (and heavily parasitized) fishes, such as bluefin tuna, sharks, and some seabass, as these species take a long time to recover.
If we hope to continue to live on the planet sustainably, preserving resources, land, and food for future generations, then this understanding of the repercussions of our actions on all aspects of ecosystems we alter is imperative. Parasites may be understudied currently, but as our awareness of them grows, so does our appreciation of them as an important part of many ecosystems. Not only do they regulate host populations, but they can also be used as an indication of ecosystem health. Dr. Lafferty also has done extensive research on the role of parasites in causing human disease and the impacts of parasites on endangered species such as the black abalone. Dr. Lafferty reminds us that “humans are part of very complicated ecological systems. We both affect elements, and elements affect us.” It is exciting to learn about the research of Dr. Lafferty and his collogues who are working to unveil more about the significance of parasites and pathogens. Next time you are sitting in that lecture hall, plagued by the sounds of cold season, try and think positively about pathogens and remember all the great things we can learn from them.