Eyes on Seagrass

In Charlotte County, local Eyes on Seagrass volunteers have completed their seagrass surveys in upper Charlotte Harbor. This was the first year of our new citizen science survey, which involved trained volunteers collecting seagrass and seaweed information at 30 different sites during a two-week period in April and again in July.

This survey is important because increasing abundances of seaweed (scientists call it macroalgae) is growing concern for many estuary communities, including Charlotte Harbor. We chose April and July to survey because in Florida estuaries, macroalgae often display seasonal abundance patterns, peaking in spring and declining in the summer.

Of course, I say often, not always — and in our first survey, this seasonal pattern did not hold up. Where we had macroalgae in April, we also had it in July. Maybe not as thick, but we saw it over a wider area.

What this means, we don’t know yet. This was our first survey, so it’s really too soon to draw any conclusion. But we will be back out next year in April and July to do it all over again. And, as we finished up our annual surveys, the Charlotte Harbor Aquatic Preserve began their fall seagrass surveys using similar but expanded methods. Over time, we hope to better understand macroalgal bloom dynamics in shallow seagrass areas.

As I put together the methods for our seagrass surveys, it was important to be as specific as possible so everyone was collecting data the same way. We had 12 volunteer teams, so consistency is key. It is also important to make volunteering a fun and educational experience.

Seagrass Reproduction

One thing many volunteers were not aware of is that seagrasses are flowering plants. And, as flowering plants, they produce fruit. Most people, scientists included, have never seen a seagrass flower, much less a seagrass fruit or seed. This time of year, however, you might get lucky enough to see the fruits of turtle grass floating on the surface or washed up on shore.

What’s so important about seagrass flowers and fruits? In a nutshell, genetic diversity. Genetic diversity is important because it increases a population’s chance of survival when disturbance events such as disease outbreaks occur. New genetic diversity is only accomplished through sexual reproduction — making flowers, fruits and the seeds within, extremely important. Seagrasses flower in the early summer months, so volunteers were encouraged to look for flowers and fruit.

They weren’t the only ones looking for signs of seagrass reproduction. In Cedar Key, some of my colleagues at the University of Florida, along with scientists from FWC and the University of Southern Mississippi, were also out looking for flowers and fruit in an effort to better understand seagrass reproduction dynamics, which until now has been quite understudied.

What scientists already know is that seagrasses have a variety of strategies for producing seeds. Some, like turtle grass, produce fruits that can float over long distances. Other seagrasses — shoal grass, for instance — produce non-buoyant fruits. These fruits drop from of the parent plant just below the surface sediments. Seagrasses also use many strategies for dispersing the seeds contained inside the fruits. Seeds may be moved by winds and water currents or even by marine animals such as fish and birds.

Now, flowers and fruits is not the only way seagrasses reproduce. Like many plants, they can also reproduce through vegetative growth. Much like many upland grasses, seagrasses grow along a rhizome or underground stem. As the rhizome grows and extends through the sediment, new shoots are sent up with bundles of blades. Vegetative propagation is fast, but there’s one problem: Each new shoot is an identical clone of the parent, so the genetics remains the same. This makes flowers and fruits critical to the survival of seagrass communities, because it’s the only way new genetics are added to a population.

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