URI scientists create model to simulate changing food web in Narragansett Bay
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| URI graduate students Annie Innes-Gold and Maggie Heinichen pose with one of the fish they studied to develop a model of the Narragansett Bay food web. (Photo courtesy of Maggie Heinichen) |
A team of scientists at the University of Rhode Island is creating a series of computer models of the food web of Narragansett Bay to simulate how the ecosystem will respond to changes in environmental conditions and human uses.
The models will be used to predict how fish abundance will change as water
temperatures rise, nutrient inputs vary, and fishing pressure fluctuates.
“A model like this allows you to test things and anticipate changes before they happen in the real ecosystem,” said Maggie Heinichen, a graduate student at the URI Graduate School of Oceanography.
“You want to be able to prepare for changes that are likely to
happen, so the model provides a starting point to ask questions and see what
might happen if different actions are taken.”
Heinichen and fellow graduate student Annie Innes-Gold collaborated on the project with Jeremy Collie, professor of oceanography, and Austin Humphries, associate professor of fisheries. They used a wide variety of data collected about the abundance of marine organisms in Narragansett Bay, as well as life history information on nearly every species of fish that visits the area, and data about environmental conditions.
Their research was published last
month in the journal Marine Ecology Progress Series. Additional
co-authors on the paper are Corinne Truesdale at the Rhode Island Department of
Environmental Management and former URI postdoctoral researcher Kelvin Gorospe.
“We built one model to represent the
bay in the mid-1990s, the beginning point of the project,” said Innes-Gold,
“and another one that represents the current state of the bay. That allowed us
to predict how the biomass of fish in the bay would change from a historical
point to the present day and see how accurate the model was in its predictions.”
The model correctly predicted
whether each group of fish or fished invertebrates would increase or decrease.
The students are now expanding the
model using various fishery management scenarios and expected temperature
changes to assess its outcomes.
“What if there was no more fishing
of a particular species, for instance, or double the fishing? How would that
affect the rest of the ecosystem?” asked Innes-Gold. “I’m also incorporating a
human behavior model to represent the recreational fishery in Narragansett Bay.
I’ve run trials on whether unsuccessful fishing trips affect whether fishermen
will come back to fish later, and how that affects the biomass of fish in the
bay.”
Heinichen is incorporating the
temperature tolerance of various fish species into the model, as well as other
data related to how fish behave in warmer water.
“Metabolism rates and consumption
rates increase as temperatures go up, and this affects the efficiency of
energy transfer through the food web,” she said. “If a fish eats more because
it’s warmer, that affects the total predation that another species is subjected
to. And if metabolism increases as waters warm, more energy is used
by the fish just existing rather than being available to turn it into growth or
reproduction.”
In addition, an undergraduate at
Brown University, Orly Mansbach, is using the model to see how fish biomass
changes as aquaculture activity varies. If twice as many oysters are farmed,
for example, how might that affect the rest of the ecosystem?
The URI students said that the
models are designed so they can be tweaked slightly with the addition of new
data to enable users to answer almost any question posed about the food web of
Narragansett Bay. They have already met with fisheries managers from the Rhode
Island Department of Environmental Management to discuss how the agency might
apply the model to questions it is investigating.
“We’re making the model open access,
so if someone wants to use it for some question yet to be determined, they will
have the model framework to use in their own way,” Heinichen said. “We don’t
know all the questions everyone has, so we’ve made sure anyone who comes across
the model can apply it to their own questions.”
“There’s another element that could
also be added to the model in the future, and that’s spatial data,” added
Innes-Gold. “It could show how the distribution of fish might change throughout
the bay, which could open the door to asking all sorts of habitat questions as
well.”
The Narragansett Bay food web model
is a project of the Rhode Island Consortium for Coastal Ecology, Assessment,
Innovation and Modeling, which is funded by the National Science Foundation.
