B on the Sea Hurricane Omar and the Seagrass Beds

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By Barbara Whitman My original plan was to begin to talk about coral reefs, but considering the events of the past week I concluded it would be timely to talk about the hurricane.” Considering most everyone on the island was out and about to see the damage from Hurricane Omar, I”m pretty sure most of you saw all the ‘seaweed” up on the shore.” It wasn’t actually seaweed.” The majority of it was manatee grass with a little turtle grass thrown in for variety.” If you had looked closely you would have seen the roots.” Seaweed doesn’t have roots. We have huge seagrass meadows just offshore ” thank goodness.” Without them the impact of the storm would have been a lot worse.” As you can see, the grasses took the brunt of the force from the waves.” That’s why seagrass is so great.” Well, that’s one of the reasons it’s so great.” It breaks up storm waves. Think of it this way.” Imagine (or you can actually do it) the flow of water from a hose along floor tiles.” If you were to take a broom or a scrub brush and block the flow with the bristles you could see how the stream of water would be broken into smaller rivulets.” That’s what the sea grasses do.” Each little blade of grass does its small part to decrease the force of surges and storms.” Without them the water would have travelled at higher speeds and force further inland and it would have brought a lot more sand along with it. So we have seen first-hand one of the benefits of large seagrass beds.” But there are more.” Fishermen, take note, seagrass is your friend.” Manatee and turtle grass make habitats that provide shelter and food for fish.” Baby fish hide in the grasses which make it easier for them to avoid being eaten by bigger fish and other predators.” More babies that survive means more big fish to catch.” Sounds good to me. Seagrasses are home to little lobster-like creatures called amphipods.” Amphipods are one of the main sources of food for fish.” Most people have never even heard of amphipods and yet they have a huge impact on the amount of fish available for us to eat.” These little guys are tiny and they have to wiggle around on their sides if you take them out of the water because they are so flat from side to side that they fall over if they try and stand up.” It’s comical. Sometimes when you pull in pot ropes or anchor lines or picked up some seaweed they get onto your fingers and wiggle around, so you may have seen them. There are other reasons seagrasses are great. You”ve all seen how brown the sea gets when it rains, right?” That is sediment being washed from the land into the sea.” If that dirt ended up on the corals it would kill them. Fortunately, the grasses slow the water down allowing the dirt to settle onto the grass beds rather than being carried out further to the coral reefs.” That being said, eutrophication (read “rotting”) is one of the major causes of seagrass loss.” A lot of the stuff that comes down the ghauts is toxic to seagrass.” Major offenders are nitrogen and phosphorous which are found in fertilizer ” and septic systems.” All of us are little manufacturers of nitrogen waste which we flush down the toilet. Now here’s where things get a little more complex.” More nitrogen means things start getting mucky on the seagrass beds.” Then to make matters worse, seaweed (algae) loves nitrogen.” It is fertilizer and seaweeds are plants.” So a lot of seaweed grows and starts to fill in the grass beds.” The seagrass dies.” Dead seagrass is basically more fertilizer for the algae.” More algae grows.” And so the cycle continues. Occasional overgrowths of seaweed are not a problem because there are sea animals like conch, shrimp and fish that eat it.” Unfortunately there aren’t as many of these animals around as there used to be.” I think any fisherman will tell you that the number and size of pot fish they are pulling in are less than they used to be.” Also conch divers must go further and deeper to get conch than they used to. These are all things to talk about another time.” The great thing is that we have large expanses of healthy seagrass beds that have done their bit to protect our shores.” And just one more little thing.” The Nevis Air and Seaport Authority did a good thing by putting in environmentally friendly moorings.” Before the moorings, boats had no choice but to anchor and I can tell you first hand that the seagrass beds were crisscrossed by long anchor scars from dragging anchors. So we are well on our way to making sure our incredibly import seagrass meadows remain intact.” Let’s hope the only thing that damages them is the occasional storm or hurricane and not us humans.” As you could see this past week, the grasses were sacrificed to protect our shores.” They”ll grow back quickly and live to work another day. – From Barbara: I’m a marine biologist and educator.” I have a Masters in Marine Biology.” Been teaching and doing research for 35 years.I’ll send the flyer which explains one of the things I do here.” Plus I have finally gotten help and funding to do a baseline survey of marine life around Nevis.” We begin this summer.

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