No predators for invasive species

By M. Carolyn Black Barrie Examiner May 16 2012

TINY TWP. — Last year’s massive bird and fish die-off in Severn Sound along the shoreline of Tiny Township alarmed residents and sparked questions about human and animal safety and the integrity of the water supply.

What caused the die-off was eventually tied to botulism bacteria, which formed a deadly paralytic toxin after it was ingested by two of the most notorious invasive species in our waterways, zebra mussels and round gobi, a small fish.

“The presence of zebra mussels promoted the growth of filamentous algae, which is attached to the bottom of the lakebed,” Bob Bowles, a well-known naturalist, said while addressing the recent Severn Sound Environmental Association (SSEA) workshop on invasive species.

The zebra mussels ingested the bacteria present among the algae, the round gobi ingested the zebra mussels and the toxin made its way up the food chain, paralyzing diving ducks and larger fish that feasted on round gobi.

Another local fish die-off several years ago was connected to the koi herpesvirus, and the suspected cause was flushing infected koi or goldfish down toilets. Common carp are very susceptible to the disease, first found in North America in 1999, and it killed thousands of fish.

Ironically, native to Europe and Asia, many carp species are also considered to be invasive.

The link between these die-offs is the presence of an invasive species or disease resident fish have no defense against.

Everything that enters the water supply has the potential to cause lasting harm and the SSEA tries to limit the damage through ongoing community education and outreach.

One recent event the SSEA hosted was Bowles’ presentation to municipal partners on invasive species called ‘Aliens Among Us.’

In the presentation, Bowles said an invasive species is “any species that has been introduced to an environment where it is not native and has since become a nuisance through rapid spread and increase in numbers, often to the detriment of native species.”

Because invaders initially have no natural predators and they’re not affected by local diseases, they can quickly proliferate and impact the balance of local ecosystems — and it’s not just animal invaders that cause harm.

Bowles says glossy buckthorn, a shrub native to Europe, western Asia and northern Africa, is the worst invader in our area.

It grows pretty much anywhere and birds find its berries delicious and spread the seeds in a wide area through defecation. When the seeds grow into dense thickets they create shade and kill all native forest and wetland growth, creating a monoculture.

“Glossy buckthorn has the biggest impact in our area,” Bowles said. “I’ve done inventory for the Wye Marsh and SSEA and found wet areas completely dominated by it.

“It’s just a little green shrub, but it’s completely dominating regeneration so that in 30 or 40 years, we’re not getting new maple or beech trees or other native growth, we’re just getting glossy buckthorn.”

A changing landscaping courtesy of invasive species is not something the SSEA wants to happen and with continuing municipality and resident support, it can ensure it doesn’t.

“Back in the early 1990s, a remedial action plan (RAP) was developed in our area to address many specific environmental concerns,” said SSEA executive director Keith Sherman.

“The first stage described the environmental conditions and problems; the second stage was to lay out a plan for remedial action that would lead toward taking Severn Sound off the list of Great Lakes areas of concern by protecting good habitat and restoration of habitat that had been degraded.”