Sea Oats: Builder of Dunes & Guardian of the Coast

August 20, 2019

Coastal habitats can be really unforgiving to life. Anything that makes a living along the coast has to be tough and they don’t come much tougher than sea oats (Uniola paniculata). This stately grass can be found growing along much of the Atlantic coast of North America as well as along the Gulf of Mexico. What’s more, its range is expanding. Not only is this grass extremely good at living on the coast, it is a major reason coastal habitats like sand dunes exist in the first place. Its presence also serves to protect coastlines from the damaging effects of storm surges. What follows is a celebration of this amazing ecosystem engineer.

Sea oats is a dominant player in coastal plant communities. Few other species can hold a candle to its ability to survive and thrive in conditions that are lethal to most other plants. The ever-present winds that blow off the ocean bring with them plenty of sand and salt spray. Sea oats takes this in strides. Not only are its tissues extremely tough, they also help prevent too much water loss in a system defined by desiccation.

Photo © Don Henise licensed by CC BY 2.0

The life cycle of sea oats begins with seeds. Its all about numbers for this species and seat oats certainly produces a lot of seed. Surprisingly, many of the seeds produced are not viable. What’s more, most will never make it past the seedling stage. You see, sea oat seeds require just the right amount of burial in sand to germinate and establish successfully. Too shallow and they are either picked off by seed predators or the resulting seedlings quickly dry up. Too deep and the limited reserves within mean the seedling exhausts itself before it can ever reach the surface.

Still, enough seeds germinate from year to year that new colonies of sea oats are frequently established. Given the right amount of burial, seedlings focus much of their first few months on developing a complex, albeit shallow root system. Within two months of germination, a single sea oat can grow a root system that is as much as 10 times the size of the rest of the plant. This is because sand is not a forgiving growing medium. Sand is constantly shifting, it does not hold on to water very long, and it is usually extremely low in nutrients. By growing a large, shallow root system, sea oats are able to not only anchor themselves in place, they are also able to take advantage of what limited water and nutrients are available.

It is also this intense root growth that makes sea oats such an important ecosystem engineer in coastal habitats. All of those roots hold on to sand extremely well. Add to that some vast mychorrhizal fungi partnerships and you have yourself a recipe for serious erosion control. The interesting thing is that as sea oats grow larger, they trap more sand. As more sand builds up around the plants, they grow even larger to avoid burial. This process snowballs until an entire dune complex develops. As the dunes stabilize, more plants are able to establish, which in turn attracts more organisms into the community. A literal ecosystem is built from sand thanks to the establishment of a single species of grass.

As sea oats mature, they will begin to produce flowers, and the process repeats itself over and over again. As mentioned above, the sea oats seeds are subject to a lot of seed predation. This means that as sea oat populations grow, more and more animals can find food in and among the dunes. So, not only do sea oats build the habitat, they also supply it with plenty of resources for organisms to utilize.

The power of sea oats does not end there. Because they are so good at controlling erosion, they help stabilize the shoreline from the punishing blow of storm surges. Dune systems, especially those of barrier islands, help reduce the amount of erosion and the momentum of wave action reaching coastal communities. Many states here in North America are starting to realize this and are now protecting sea oat populations as a result.

Sea oats, though tough, are not indestructible. We humans can do a lot of damage to these plants and the communities they create simply by walking or driving on them. Pathways from foot and vehicle traffic kill off the dune vegetation and create a path of least resistance for wind, which quickly erodes the dunes. Apart from that, development and resulting runoff also destroy sensitive dune communities, making our coastlines that much more vulnerable to the inevitable storms that threaten their very existence.

As our climate continues to change at an unprecedented rate and storms grow ever stronger, it is very important that we recognize the role important species like sea oats play in not only providing habitat, but also protecting our coastlines. Dune stabilization and restoration projects are growing in popularity as a cost effective solution to some of the threats facing coastal communities. Among the many techniques for restoring dunes is the planting of native dune building species like sea oats. If you live near or simply like to enjoy the coast, please stay off the dunes. Foot and vehicle traffic make quick work of these habitats and we simply cannot afford less of them.

Watch our short film DUNES to learn more about these incredible ecosystems.

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3] [4] [5]

Freshwater Sponges

August 9, 2016

The first true love of my life was the underwater world. I was obsessed with everything aquatic, especially fish. My obsession with fish gave way to a collection of home aquaria that tested the limits of my parents’ patience. Most of my aquariums were landscaped with aquatic plants whose variety boggled the mind. The underwater world is full of incredibly varied habitats that are home to a wide variety of organisms including freshwater sponges. Though I was never able to grow any of them in home aquaria, seeing them in the wild was an incredible experience I won’t soon forget.

Though it is not readily apparent, sponges are animals. They aren't a single animal either. What functions as a single unit is actually a collection of individual organisms working in unison. The entire body of the sponge consists of these microscopic individuals connected by living tissue and held rigid by tiny rods made out of silica. I know what you're thinking, this is not a plant, why am I writing about it? The answer lies in the green color of this sponge.

There are many species of freshwater sponge throughout the world. Here in North America we have somewhere around 30. They are an indicator of clean, clear water. If you see sponges then you know it must be a healthy ecosystem. The freshwater sponges come in many different shapes, colors and sizes. Even within a species there can be a lot of variety between different colonies. Pictured here is a species of Spongilla. Not all Spongilla are green though. Many are brown. The green coloration comes from algae living symbiotically within the tissue of the sponge. Similar to lichens, the algae photosynthesize and provide food to the sponge in return for a safe place to grow.

Though not a plant, the need to photosynthesize has pushed these sponges to grow into shapes not unlike what is seen in the plant kingdom. Depending on water clarity, temperature, and light levels, sponge shapes range from prostrate, creeping forms to upright branching structures. Also similar to plants, sponges can reproduce both sexually and asexually. As the water begins to cool in the fall, the sponges produce what are known as gemmules. These little packets of dormant cells are quite hardy, resisting pretty much anything the environment can throw at them. When the water begins to warm in the spring, the gemmules will grow into new sponge colonies. During the warm summer months, sponges reproduce sexually. Males release sperm into the water in hopes that it will come into contact with receptive females. This is similar to what we see many wind-pollinated tree species do in the spring.

The idea that two completely different branches on the tree of life have converged onto similar biological strategies is a very exciting idea. Indeed, the similarities are striking. I went a long time before I knew that these freshwater sponges even existed. The fact that I live in the Great Lakes region and never encountered them tells me just how poorly we have treated our local waterways.

Further Reading: [1] [2] [3]

Aquarium Banana

September 18, 2015

One of my first true passions in life was maintaining freshwater aquariums. There is something about being able to observe a world totally foreign to our own that drew me in. It wasn't long before I discovered the splendor of planted aquascapes. I would have to say that my first foray into this realm probably planted the botanical seed that would later explode into the obsession it is today.

I was always rather perplexed by a plant that I would see for sale at the local aquarium shop. They were labelled as "banana plants" because of their peculiar root structures. They never seemed to fit my aesthetic in those early days so I largely passed them by. Recently I have gotten back into aquariums, only this time it is very plant centric. While perusing the plants offered here in town, I again came across the peculiar banana plant.

This time around, I am a bit more versed in taxonomy and this plant made more sense. I realized that the banana plants we see for sale for aquariums are small, immature specimens of some sort of "lily pad." A deeper investigation would prove me correct. Though not a true water lily (family Nymphaeaceae), the banana plants nonetheless take on a similar growth form with large, floating leaves emerging from an underwater rootstock.

Banana plants are known scientifically as Nymphoides aquatica. Their generic name comes from their striking similarity to the afore mentioned water lilies. However, this resemblance is merely superficial. Banana plants belong to the family Menyanthaceae, making it a relative of plants like buckbean (Menyanthes trifoliata). They grow native in calm bodies of water throughout southeastern North America. Whereas the young leaves grow immersed, larger adult leaves eventually make their way to the surface where they float.

Photo by Show_ryu licensed under Public Domain

From time to time, small white flowers are produced. This is when its familiar affiliation makes the most sense. This species is dioecious, though seed set is apparently sporadic. Regardless, banana plants readily reproduce vegetatively, either by fragmentation of their roots or by broken leaves settling in a spot and forming roots themselves.

So far this is an interesting aquarium specimen. It seems to have adjusted to my aquarium rather well and it grows pretty quickly. In time I hope it performs more like it does in the wild than as a sad, stunted specimen doomed to a slow death. Only time will tell.

Flower Pic: Show_ryu (Wikimedia Commons)

Why All the Lace?

January 26, 2015

All too often, botanizing is restricted to the land. Sure, there is the occasional foray to a marsh or bog but, for the most part, relatively few plant folk like to get wet in their quests to meet new and exciting plant species. There is an entire world of aquatic plants that don't get enough credit. One such plant is Aponogeton madagascariensis, the lace plant.

Anyone into planted aquariums has undoubtedly come across this species at least once. It is kind of a holy grail of aquarium gardening. Hailing from Madagascar, this is one of the truly aquatic Aponogeton species. Though there are a few different geographic variations, they are all easily recognized by the lacy appearance of their leaves. Known as "fenestration," the lacy structure is the result of programmed cell death during the development of the leaves. As interesting as that fact is in and of itself, the question remains, what is the function of fenestration?

There have been many hypotheses put forward to explain this phenomenon. Some believe it helps to reduce damage from turbulence wheras others believe it helps to increase movement around the leaves and helps avoid stagnation. The truth is, no one is entirely certain. However, a clue to the benefits of fenestration has come out of work done on an entirely unrelated terrestrial plant species.

The epiphytic arum commonly referred to as a Swiss cheese plant (Monstera deliciosa) also exhibits fenestrated leaves. Researchers at Indiana University in Bloomington have found that the holes in the leaves may actually help gather more light in a shaded environment. The understory of a rainforest and the underwater habitat in which the lace plant grows may be more similar in light availability than you would think. How would holes in the leaves allow the plant to gather more light?

As it turns out, a fenestrated leaf can grow much larger while still maintaining the same amount of surface area. By spreading out its surface area over a larger region, a fenestrated leaf is actually more efficient at gathering what limited light is available. More work needs to be done to see if this is truly the case for the lace plant but the idea is tantalizing to say the least. Sadly, like too much of Madagascar's wildlife, the lace plant is becoming quite rare in the wild due to habitat destruction. So, the next time you come across one of these in an aquarium store, make sure to give this plant the attention it deserves.

Further Reading: [1] [2] [3]

Mysterious Marimo

January 22, 2015

I was recently approached by a lady who was quite curious as to what mystical energies could have created the increasingly popular marimo balls that are often seen for sale in aquarium shops. Surely no natural force could create such spherical wonders in nature, right? She seemed quite disappointed by my answer and left feeling cheated of the super natural mechanism she was looking for. However, before we discuss the source of these fury green balls, let's start at the beginning.

Marimo balls or lake balls are a specific growth form of a macroalga known scientifically as Aegagropila linnaei. It belongs to the Cladophoraceae family and can be found in lakes throughout the northern hemisphere. They are most popularly known from lakes in Japan where they hold serious cultural significance. The word "marimo" is Japanese for "ball seaweed."

So, how does this species of alga form itself into a ball? The answer is not mystical, though it is quite specific. To start with, the ball form of this alga is not the only way it grows. Populations will also form as mats on the lake bed, carpeting rocks and other debris. When pieces break off and become free floating, tidal action gently rolls them around. As they grow and move, they become tangled up and gradually form themselves into this spherical shape. The overall shape and survival of the alga in this form is reliant on this tidal motion. All parts of the ball actively photosynthesize and if it is not exposed to light all over, the shaded parts die and the ball will be no longer. Luckily, the alga reproduces vegetatively so the broken parts can still go on living.

Sadly, marimo balls are not doing too well in the wild. As we have seen with so many other species, human impacts are taking their toll on Aegagropila linnaei. Eutrophication, logging, and development within the watersheds that feed these lakes are causing the once clear waters to become quite murky. As this issue increases, the alga can no longer photosynthesize on a level that can sustain its populations. Acid rain is another big issue. Marimo balls tend to grow in calcareous lakes. As the water acidifies, they are unable to cope. Finally, one of the other issues facing the marimo balls is their popularity. In some areas, they are being harvested for the aquarium trade at unsustainable levels. One source claims that a majority of marimo balls for sale in aquarium shops are sourced from the Ukraine, which means that those populations are under serious pressure.

Luckily, their popularity may also lead to more protective measures. For instance, they are so important to Japanese culture that they are now a protected species there. The Netherlands is also waking up to the decline of this species. Until more can be done, it is best to only buy from nursery grown sources. Formation of the balls has been done in an artificial setting. Truly, no species is safe from the irresponsible nature of modern man.

Photo Credit: mossball.com