Life among the mangroves

In January, Michael Marchetti, who teaches biology at Chico State University, escaped the Northern California cold by spending his intersession vacation on the coast in Mexico, where the weather was strictly of the T-shirt-and-shorts variety.

But Marchetti wasn’t there just to frolic on the beach or sip margaritas in a jalapa. He had something more important in mind: helping set up a two-year research and planning program designed to preserve the dwindling tropical mangrove systems of the area.

Marchetti is part of an interdisciplinary team established to study and protect a particular mangrove forest near La Manzanilla, a small fishing and tourist town in Jalisco state, south of Puerto Vallarta. He is joined in the program by professors from the University of Nevada–Reno, the University of South Florida, the University of Guadalajara and CSU Channel Islands.

The project is funded by EarthWatch, a nonprofit environmental-research group.

Joining Marchetti at a camp and research station set up under the thick canopy were six fellow teachers and 12 students. They shared the space with herons and egrets, a wide variety of fish and a number of endangered American crocodiles that were three to four meters long.

The mangrove system borders the town, but the team’s camp was set up on the beach, on the edge of a tropical bayou.

Mangroves grow in the waterlogged, salty soils of sheltered tropical and subtropical shores, serving as a bridge between terrestrial and marine environments. They have adapted to twice-a-day tidal flows, as well as twice-monthly spring and neap tides, and are noted for their distinctive nests of stilt-like roots that allow them to thrive in the salty, oxygen-poor soil of the coastal zone. The roots absorb oxygen from the air, while the trees’ leaves can excrete excess salt.

The forests are hosts for a wide range of aquatic and salt-tolerant plants, and together they provide nursery habitat for a vast array of aquatic animal species, including many coral reef and commercially important fish species.

La Manzanilla’s forest is located on a small tropical bayou. It’s a peaceful place, Marchetti says. Yes, there are crocodiles around, but the researchers stay in their boats, so there’s no danger. The sounds of the ocean drift into camp, but it’s fairly quiet during the day, except in the morning, when the air comes alive with bird sounds.

There are four distinct ecosystems in the area: stream, mangrove forest, marine and coral reef. As a fisheries biologist, Marchetti is interested in studying where ecosystems come together as well as possibly seeing how damage to one system can affect the others. Coral reefs and mangroves are often found in the same neighborhoods, and with both disappearing rapidly, scientists are eager to determine how degradation of the mangroves contributes to coral reef destruction.

Marchetti will return to La Manzanilla for the summer rainy season, and next January he’ll take several students with him to learn about the ecosystems, a rare opportunity for those attending landlocked Chico State.

The class will be on the fish ecology of Mexico, Marchetti explained, and the students will study the fish in all four of the ecosystems. “We will be using nets, traps, snorkeling—not with the crocodiles,” he said, laughing. “It’s hands-on stuff. We’ll be there collecting fish.”

When not chasing fish themselves, the students will be talking to local fishermen to build a history of the fish in the area—what kinds they are catching now and what they were catching before.

Mangrove systems are heavily threatened everywhere they exist, Marchetti said. That’s because they grow on the coast, where people like to build. Many are harvested for hardwoods, and others are cut down to free up land for farming.

“The town of La Manzanilla is growing by leaps and bounds, and one of the things they’re thinking of doing is dumping raw sewage into the mangroves,” Marchetti added. “This would clearly be a bad thing for the mangrove, and our group wanted to study the grove before the plant comes online and starts dumping sewage.”

Part of the program is working with the town to try to find a way to keep the mangrove system safe, and explaining just how impacts on the mangroves affect the local fisheries. “When the local people have an interest in the ecology of the system, they tend to take care of it,” Marchetti said.

While it is too early to tell, Marchetti said he is hopeful, saying that the locals really like the crocodiles and want to protect them. Land owners as well as the city are both willing to work with the new program, and over the next two years Marchetti and the rest of the group hope to find a way to protect the tropical bayou and its rare crocodiles while also allowing the town to grow.