Going with the Flow
Predators & Prey Respond to Estuary Impacts
By Nick Hayman, M.S. Candidate
Estuaries are special habitats. They support a high diversity of life and perform important ecosystem services like water filtration. But because estuaries are in close proximity to human populations, these habitats and the services they provide are threatened.
In San Diego, humans have affected estuaries by modifying the shape of their tidal channels, altering the natural flow of water through these habitats. Agricultural use of pesticides and herbicides can also disturb estuaries because these chemicals travel downstream and accumulate in estuarine water and sediments.
Fieldwork: Nick and his undergraduate assistant Jared use a sieve to find worms at the Tijuana River National Estuarine Research Reserve.
I am studying how human activities affect predator-prey relationships in estuaries. Specifically, I am testing how water flow speed and an insecticide, chlorpyrifos, change the feeding behavior of the California killifish and a small, tube dwelling worm.
The Laboratory Flume: This experimental setup allows Nick and the Hentschel lab to explore the effects of flow speed on estuarine organisms.
Water flow can dramatically alter how successfully fish can grab their worm prey. Think about trying to grab a shiny rock on the bottom of a fast flowing stream; it takes so much effort to maintain your position that it is difficult to snatch the stone. Grabbing stones is much easier in a calm stream.
The worms are "interface feeders," meaning they use different feeding strategies in high and low water flow. During high flow, worms extend their palps (feeding structure) into the water column and during low flow they spread their palps over the sediment looking for food particles.
I have discovered that fish exposed to an insecticide are lousy hunters and feed less. Exposed worms also feed less and spend more time withdrawn in their tube burrows.
My goal is to better understand these effects so that we can restore and manage these critical habitats.
A California killifish attacks a small, tube dwelling worm during Nick’s experiment. Notice the palps (the feeding structure of the worm) sticking out of a tube to the right of the fish attack.
A day in the life...
I spend most of my time collaborating with other researchers, trudging through the beautiful salt marshes around San Diego, and inspiring the next generation of marine scientists! I spend long days running flume trials, protein activity assays, and writing up my results. I am also a co-leader of MEBSA, so I spend a lot of time planning science outreach events in San Diego, including Marine Science Day March 15th!
Author: Nick Hayman, M.S. Candidate & MEBSA Co-Chair, contact at firstname.lastname@example.org
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