As Sean Augustine, 8, tramped through City Park on Saturday morning, he was on a scientific mission.

The coolest part for him was the green tree frog he saw up close in the specimen bag kept by his group, which recorded all of the amphibians they observed during a morning walk through the Couturie Forest-Scout Island section of the park.

Sean, a student at Holy Cross School, also learned about the eggs of apple snails that adhere in clusters on far too many of the park’s aquatic plants.

“They’re bright pink; they look like bubble gum. But don’t eat them,” he said.

For four hours Saturday morning, about 100 volunteers of all ages and about a dozen scientists walked along soggy trails for BioBlitz, a biological inventory of the many species of plants and animals that exist within the park.

Groups were assigned a specific type of creature. Some looked for reptiles or fish; others tallied species of mammals, amphibians or insects. Later, at night, a group carrying special sonic monitors would begin to catalog the bat population.

Sean’s group also included St. Mary's Dominican High School biology teacher Crissy Giacona and her son, Brother Martin High School freshman Alex Giacona.

Alex, 13, was also impressed by the apple snails, which can grow to the size of a softball, he said. Yet, despite their “wow” factor, the snails are an unwelcome newcomer to Louisiana, Alex noted. “That’s because they eat lots of the vegetation and they multiply quickly because they have no natural predators.”

For “citizen-scientists” like the two boys, the BioBlitz was educational. But it’s also a kickoff for a much broader effort to determine how the 1,300-acre park is being managed and developed, said Bob Thomas, who heads up the Loyola Center for Environmental Communication and chairs the park’s Sustainability Committee.

The effort will document the park’s biodiversity, tracking whether native species may be disappearing and where invasive species are gaining a foothold.

In September, the park’s board will vote on what should be done with the 60-acre Couturie Forest-Scout Island area, which is now largely wild, known for its trees, waterways and trails covered with woodchips.

A detailed biological census will guide that decision, Thomas said: “We need to know what’s there. What can we plant there?”

He noted that some butterflies and other creatures depend on plants that don’t necessarily win landscaping awards. “If you 're-wild' an area, you don’t make it into a garden,” he said. “And weedy fields are real important in nature.”

Even before the BioBlitz, Thomas had started his own list of the park’s flora and fauna that already had reached eight pages, ranging from Acanthepeira stellata, the starbellied orb weaver spider, to Zizaniopsis miliacea, a native plant commonly known as giant cutgrass.

From now on, he expects the list to grow significantly, thanks to the volunteers and the eagle-eyed scientists he assembled with the help of his daughter, Aimee Thomas, an assistant biology professor at Loyola University who specializes in spiders.

Her student Michael Pashkevich, a recent Loyola graduate who has received a Gates Cambridge Scholarship to fund his doctoral studies at the famed English university, captivated a schoolchild with tales of wolf spiders and huntsman spiders whose blue eyes glitter at night when caught in the beam of a light. It's even better if the light catches a female spider that’s carrying babies on its back — "It’s like a disco ball,” he said enthusiastically.

In addition to the scientists who walked trails on Saturday, others are participating in the process by long distance, identifying species through photographs. They include a snail expert from Oklahoma, a fungus authority in Florida and a specialist at the Smithsonian Institution who looks at galls, abnormal plant growths, to determine what insect caused them.

Self-trained naturalists like Cathy DiSalvo, 67, are also essential to the survey. Her birding group didn’t see anything remarkable on Saturday. “Just the usual,” she said, rattling off what they’d seen: flycatchers, blue jays, Carolina warblers, downy woodpeckers and great blue herons.

The park sees many more bird species in the fall and spring. “This park is critical in the migratory path,” said DiSalvo, who routinely logs her sightings in a Cornell University birding database and so was a natural for BioBlitz.

Jennifer Lamb, 28, a biologist at Southeastern Louisiana University, spent the day helping her group sift through every puddle, looking for amphibians. They found a few different toads and frogs and a lot of skinks — small lizards that are essential to the food chain, she said.

Although the BioBlitz was staged in a part of the park known for its wildlife, Thomas is committed to scouring all corners of City Park.

He personally will walk the grounds of Tad Gormley Stadium. “I’m going to walk it several times to see if something is popping up in the grass there that we don’t see anywhere else,” he said.