We were there to collect garbage, but we found lots of life on the Deer Island part of our adventure trip to the gulf.
Biota on the Deer Island Beach
Category: immersion
Collecting Garbage on the Beach: The Trip to Deer Island
To the left, a long, narrow, lightly-wooded island. Skeletal trees, dying on the upwind end; drowned by the attrition of the waves. To the right, a narrow, eager, urban strip. Hotels and casinos, pressing against the water’s edge; vying for access to the white sand beaches and gentle waters of the sound. Such different places on either side, yet the one on the right is the reason we’ve come to the one on the left. We’re here as part of our Adventure Trip to pick up any artificial debris that’s managed to float across the sound and collect and contaminate the quiet, isolated beaches of the island.
We’d gotten on a pontoon at the research lab right after breakfast, so the early adolescents were still a little groggy. Our vessel’s captain asked a question about team mascots which promptly woke up approximately 63.64% of the class, and served as a topic of conversation for the twenty or so minutes it took to get to the drop-off point on the west-north-western end of Deer Island.
Mostly unobserved by my busy students were the half dozen shrimp boats casting their nets in the sound. Long, spider-like, almost robotic arms spread out from the vessel to lower the nets. It’s quite an impressive sight. Commercial shrimping is a major industry all along the Gulf coast.
Deer Island (and its hike). View Coastal Sciences Camp, Gulf Coast Research Lab in a larger map
The island itself is long and thin, wedge shaped, no more than a couple hundred meters at its widest at the eastern end, but thinning to less than 100 meters to the west. Although wider, almost all the trees seem to have died on the eastern end. Then there is a gap and the trees are mostly alive. Looking at the satellite image, you can see a clear channel cutting through the island. From the image, I’d guess the channel is tidal, with water moving back and forth, filling and draining the sound with each cycle of the tides. The sediment deposited in the quieter waters of the sound (to the north) seem to be forming a small, white-sand delta; the equivalent deposits on the south are probably washed away by the longshore current pretty quickly since that shore is exposed to the wind and waves.
Deer Island is not an active barrier island: twelve kilometers to the south, Horn and Ship Islands do that job today. However, given the shape of Deer Island, it may have once been a barrier when the coastline was further inland. This is all part of the coastal plains deltas, which includes the Mississippi Delta and smaller rivers. These rivers transport sediment from the mountains inland and deposit them in the ocean, gradually building out the land. As the deltas build out, the barrier islands also push out to accommodate them.
The pontoon pulled up on a broad, sandy beach then retreated to deeper waters where the fishing is better. The white sand beach we landed on was an artifice, just like the East Beach Drive beach we’d walked the day before. Our first steps betrayed the secret. Breaking through a thin cover of sand, we sank knee-deep into a rich black mud that’s the natural sediment in a quiet waterway like the sound.
Our guide, on the other hand, seemed to have a preternatural ability to avoid sinking into the mud, or even getting her feet wet, or even touching the water.
References
The first image was distorted using a four point distortion method with ImageMagick.
> convert sc-deer-island-1843.jpg -matte -virtual-pixel transparent -distort Perspective ‘0,0,0,200 0,664,0,564 1000,0,1000,0 1000,664,1000,664’ tst2.jpg
> convert sc-deer-island-1841.jpg -matte -virtual-pixel transparent -distort Perspective ‘0,0,0,0 0,664,0,664 1000,0,1000,200 1000,664,1000,564’ tst.jpg
Squid Dissection
To follow up my own attempts at a fish anatomy lesson, I asked the people at the Gulf Coast Research Lab’s Marine Education Center to include a dissection in their program for our Adventure Trip. They chose squid.
Squid are nice because they’re mostly soft tissue and the organs are fairly easy to identify. They’re also quite charismatic, which piqued the students’ interest. These squid were going to be used as bait, so I didn’t feel too badly about using them for science.
Once again, our guide, Stephanie, was an excellent teacher. A good time was had by all, even though it was a bit gruesome.
I would have liked to have a little more time to draw some diagrams, but I don’t think my students would have had the patience. It was the Adventure Trip after all, and they’d much rather spend the time outside.
As for the future, I like this note about squid dissection:
… this … is a tactile experience. You may want to explore this aspect through sensory activities, written descriptions, poetry, and/or artwork. Encourage students to experience the many textures found inside and outside the squid’s body. Moving fingertips along the suckers is suggested as well – the suckers do not scrape or hurt if you are gentle with them.
–Center for Educational and Training Technology, Mississippi State University: Squid Dissection
This quote comes from a Mississippi State website, which also has a great set of calamari recipes in addition to dissection instructions. I’m always in favor of an interdisciplinary approach; food-preparation rather than purely dissection.
Finally, the University of Buffalo’s Biology 200 class has some excellent, labeled pictures, for reference.
Government and Geology in Nashville
Earlier this spring, we had an excellent immersion trip to Nashville. The primary purpose was to visit the capitol and meet with Memphis’ State Representative Mark Kernell.
But we also had time to visit the Abintra Montessori School in Nashville (who returned the visit last month), and have an excellent hike along a limestone-bedded stream in Montgomery Bell State Park. The hike, however, was not without some controversy.
Shilo and Pickwick Immersion
The Shiloh National Battlefield is only a couple hours east of Memphis (or west of Nashville), and its proximity to Corinth, MS, and a state park with a hydroelectric dam, make it an excellent place for an immersion trip during the cycle when we study the U.S. Civil War and electromagnetism. Two years ago, on a couple beautiful, sunny days in the middle of spring (early April), almost on the anniversary of the battle, we made the trip.
We drove over on a Tuesday morning, and since our very nice cabins at Pickwick Landing State Park were not quite ready yet, we ate the lunch we’d brought with us at a picnic shelter on the park grounds. The choice of picnic shelter number 6 was serendipitous, because not only was it beautifully located, but just down the hill, at the edge of the water, is an excellent outcrop of fossiliferous limestone.
After unloading at the cabins, we took a short, afternoon drive to see the hydroelectric dam.
The next morning we hiked along the Confederate line of advance during the Battle of Shiloh.
It was a relatively long hike, but useful in that it allowed students a feel at least for the scale of the battle, and the conditions the soldiers endured. There was also a nice museum at the end, with an interesting video and an excellent demonstration from one of the park rangers (you need to book an appointment ahead of time).
Finally, on Thursday morning, on our way back to Memphis, we stopped at the Civil War Interpretive Center in Corinth, Mississippi. The museum is excellent, especially the Stream of American History, which is abstract enough that it makes a great puzzle for students to figure out.
The map below shows the locations of the stops, and has links to the posts about each stop.
View Shiloh Immersion in a larger map
Blind Sampling of the Subsurface
On the first morning of the Coastal Science Camp, between dip netting and seining at the estuary, we tried sampling beneath the seabed using a little coring device which I seem to have to forgotten the name of.
Usually, they can see the little holes in the seabed where the benthic macrofauna live, but not this time. All the sediment pouring into the Mississippi Sound from this spring’s swollen rivers had made the waters too turbid to see through. So we were coring blind.
The corer is simply a metal (stainless steel) barrel with a rubber piston inside. The piston is connected to a handle at the top with metal rod. To sample, you put the tip of the barrel at the sediment-water interface and push the barrel into the sediment at the same time holding the handle steady to keep the piston from moving into the sediment. Holding the piston steady provides a little suction on the inside of the barrel, which helps the barrel move into the sediment, and keeps the sediment in the barrel when you pull it out. However, it does help to put your hand on the bottom of the barrel as soon as possible to keep the sediment from falling out, even if that means sticking your hand into the sediment itself.
Once you’ve recovered the sediment, you extrude it into a sieve. Sometimes you can see a little layering in the extruding sediment, but we did not take the time to try to interpret it since our focus was on finding benthic fauna.
The sieve’s mesh is pretty coarse, so anything sand sized or smaller is washed out as you gently rock it back and forth in the water. We did not find much. Mostly small pebbles. Without being able to see the seabed our sampling pattern was pretty random.
The more persistent groups (the class had been broken into groups of two or three) did find a couple things, including a polychaete, which is a segmented worm.
They also turned up a small, clawed, lobster-like organism:
We also found the burrow of an unknown organism, surrounded by a clayey cast. It looked very much like some of the fossilized burrow casts we saw at Coon Creek.
This type of sampling was not everyone’s cup of tea, however. Fortunately, the water was shallow and warm, so a good time was had by all.
Longshore Drift and Pufferfish
It was about 1.5 kilometers from the Research Lab to the estuary where we spent our first morning sampling (overview of the trip is here).
Walking along the beach to get there, we could see the beach houses to the right of us, across the narrow road of East Beach Drive, standing tall on columns to keep them above the reach of the storms. According to Stephanie, our guide, the storm surge from Hurricane Katrina in 2005, reached awfully close to the tops of the columns. The research lab, which is not elevated, lost an entire building to that hurricane. Indeed, much of the coast is still recovering from Katrina’s damage.
The white sandy beach, on the other hand, looked beautiful, which was a bit odd. After all, how did it survive the storm? Furthermore, when you think about it, this beach is located behind a string of barrier islands, which protect the coast from the full force of the waves coming out of the Gulf of Mexico, so how come there is enough wave energy to maintain a sandy beach. The relatively calm waters should allow finer grained sediment, like clay and silt, to settle out, and this area really should be a marsh. The answer, it seems, is that this is an artificial beach. Every few years, thousands of tons of sand are dumped along the coast to “replenish” the beachs.
This coastline really should be a tidal marsh, like the one we found when we got to the estuary. These Gulf-coast salt-marshes are fronted by a relatively short version of smooth cordgrass (spartina alterniflora), backed up by the taller, and more common black needlerush (Juncus roemerianus Scheele) .
Longshore Drift
Now, if this is a low-energy environment that allows silt and clay can settle out of the water column, where does the sand go so that it has to be replenished every so often? It is gradually moved along the coast by longshore drift.
Waves hit the beach at an angle. As they break, the turbulent swash pushes sand up the beach at the same angle as the movement of the waves. As the wave retreats, the backwash, drawn by gravity, pulls sand perpendicularly down towards the water. The net effect, is that sand gradually moves down the coastline with each swash and backwash of the waves.
Since dumping tons of sand is expensive, engineers try other things to prevent the sand from running off down the beach. Someone, a very long time ago, had the great idea to build a wall sticking out from the beach to impede the sand in its unwanted migration. This type of wall is called a groin (or sometimes a groyne in polite company), and it does stop the sand. In fact, the sand builds up on the upwind side of the groin. Unfortunately, it does not stop the longshore drift on the downwind side, and that results in the erosion of a bay on that side.
Pufferfish
Beaches are also great places to find random things washing up. We lucked upon an unusually large pufferfish (family: tetraodontidae). It was quite puffed up. It was also quite dead.
Pufferfish are famous for being extremely poisonous. According to the National Geographic page on pufferfish, their tetrodotoxin over a thousand times more poisonous than cyanide, and there is no known antidote.
Seining in the Sound
After surface sampling with the dip nets, and subsurface sampling with the little corers, we tried sampling the water column using a small seine.
Seining requires teamwork, and I was pleased to see everyone working well together, focused on the job at hand.
Hauling on the nets, with the smell of salt in the air, resurrected long neglected memories of fishermen at work on tropical, Atlantic beaches. Back then they were going after fish for the market, here, with our much finer meshed net, we were looking for anything interesting in the water column.
Everyone got touch a ctenophore (comb jelly), which I will note is not a jellyfish, and is also not poisonous.
Students also had a chance to hold a croaker (a fish of the family Sciaenidae), and feel it croak.
Our guide was great. She was quite knowledgeable about the fauna we ran into, and very good at sharing information.
Interestingly, we were not the only ones out seining that morning. There was a small group from the research lab looking for skates for a research project. I think they said that this was their third time out looking, but like us, they did not find any elasmobranchs (not counting the one dead specimen we ran into while dip netting).
