A big little deal

By Alee Knoell

It’s National Oyster Day! For most of us, this may simply mean one-dollar oysters at your favorite seafood restaurant. But, although the saying goes “It’s what’s on the inside that counts”, the oysters edible insides aren’t their only noteworthy attribute.

It’s likely that we’ve all at least seen an oyster, be it on a murky riverside or inside a seafood restaurant. But how many of us have put any thought into them? Whether you think they’re icky or delicious or just these things that are a part of the estuary, their importance is far-reaching.

Perhaps their most impressive trait, a full-grown oyster can filter up to 50 gallons of water a day, consuming or depositing excess nitrogen and sediment.

Aside from bettering the quality of the surrounding water, they are a great resource to a wide variety of marine species, serving as a nursery for a wide variety of organisms, from shrimp to blue crabs, who take advantage of the multitude of nooks and crannies that characterize oyster reefs. In doing so, they are also providing a diverse food source for many fish species.

And finally, oyster reefs offer erosion control, creating a natural barrier between the shore and incoming storms and tides (a very celebratory feature indeed, come hurricane season).

With this rich supply of ecosystem services, and historically low populations, oysters are naturally on the NERR’s radar. Oyster reefs throughout the intracoastal have been monitored since 2015. To supplement these findings, the reserve has supplemented this study with spat monitoring.

Spat is the term used for oyster larvae once they have attach themselves to a surface. Once they latch on, they are settled, and will then grow into the full sized oysters we all know and love.

But in the meantime, these little guys can be indicators of oyster health and recruitment. To do this, we use “spat trees”, (featured in the large photo to the left). These PVC contraptions each dangle an enticing string of squeaky clean (okay, maybe not that clean) oyster shells off either end. Replicating the oysters composing the reefs they hang above, these shells are also subject to spat settlement, thus enabling us to collect them once a month and pore over the four middle shells in search of baby oysters.

Because spat start off as teeny tiny little things (and are sometimes just downright tricky to see) this is done using a microscope. A lot look a little something like this:

Once all the shells that we collected have been processed, the data is wrapped up nice and neat in pretty little graph.

In 2018, you can see that spat settlement didn’t really start to kick off until around April. As we’ve noticed analyzing past years, we experience two peaks- a smaller rise mid-year, and then a larger one as the year comes to an end. Notice that, while not entirely uniform, each reef holds a similar pattern as far as the highs and lows of spat settlement.

With data from past years in mind, we expect this month’s spat counts to yield the largest spat count this year so far, then gearing up for the larger peak to fall somewhere between the months of September and November.

Stay tuned to see if our prediction are on the right path!

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