Can Bird $#!* Save the Bay?

Eelgrass in Long Island Sound

Scientists discover that marine animals disperse seagrass

...a recent study in Marine Ecology Progress Series documents that several species of marine animal are key to dispersing seagrass, overturning the assumption that seagrass was largely dispersed by abiotic methods (such as wind and waves).

"Traditional thinking is that eelgrass disperses by abiotic mechanisms such as floating seeds, floating reproductive shoots, or currents pushing seeds along the seafloor," explains lead author Sarah Sumoski with the Virginia Institute of Marine Science. "Our study shows that eelgrass seeds can also be dispersed through consumption and excretion by fish, terrapins, and birds—providing a means to bring seeds to isolated areas."

The researchers studied eelgrass (Zostera marina), a type of seagrass, in the Chesapeake Bay in the eastern U.S. Feeding nearly two thousand eelgrass seeds to five species—including three fish, one turtle, and one seabird—the researchers found that the seeds survived the passage through the animal's guts and germinated successfully. But survival isn't the only important thing to a plant: distance also matters. If a plant species is to colonize new areas it will need to ensure its seeds can go far.

"We estimate that the fishes could disperse eelgrass seeds 10s to 100s of meters, while the maximum dispersal distance for terrapins is around 1,500 meters, or about a mile. The scaup [seabird] was the champ, with a maximum dispersal distance of more than 10 miles," explains Sumoski.

While dispersal by winds and currents are also likely important, Sumoksi says that seagrass seeds dispersed by animals may have a better chance for survival.

"[Animals] prefer to live under the conditions that favor seagrass growth and thus will tend to carry seeds to areas where they'll germinate. Wind and currents can easily disperse seeds into areas unsuitable for seagrass growth."

The last is an important concept; seeds dispersed to unfavorable areas is wasted.  With an animal vector, the chance of the seed finding suitable habitat for living is much increased.  This reminds me of the old biblical passage, the parable of the sower, Mark 4:8.

And some fell among thorns, and the thorns grew up, and choked it, and it yielded no fruit. And other fell on good ground, and did yield fruit that sprang up and increased; and brought forth, some thirty, and some sixty, and some an hundred.

 I don't plan to make biblical quotes a habit.