Everglades Ecosystems

This week and next we’re taking a look at the largest subtropical wilderness in America, the Everglades. What we now know as Everglades National Park is just a fraction of the original Everglades, and unfortunately, almost daily it becomes a larger percentage of what of remains today. While what remains is an incredibly diverse variety of habitats, each with their own plants and animals, it is not without its challenges. We’ll explore what’s so special about this place as well as what’s going wrong there.

In its former glory, the Everglades was a huge watershed. Water flowed south from areas north of Lake Okeechobee and drained to the east, west, and south. Some of the water flowed east and west into the Atlantic Ocean and Gulf of Mexico, respectively, through traditional rivers and streams. Some water flowed out through the slow-moving “River of Grass”, as the Everglades became known as. Where the water goes and how much gets there determines the many different ecosystems.

Many other factors go into building an ecosystem, including geology and climate. To me, what gives an ecosystem its character is its plant life. The Everglades has quite the cast of characters, with grasses inhabiting the freshwater sloughs and marl and coastal prairies. Marl prairie is grassland of thin soil formed on top of limestone bedrock. The soil is high in calcite and the bedrock may be exposed in some areas. Rainwater becomes acidic as it dissolves plant material, and even a weak acid can easily dissolve limestone. The bedrock here is very porous. Marl prairies drain slowly.

Marl prairie (Florida Museum of Natural History)

Freshwater sloughs are main arteries for water flowing to the sea. The water moves very slowly and is very grassy. The sloughs are dotted with “islands” of trees and are bounded by the higher and drier marl prairies.

Freshwater slough (NPS)

Mangrove forests line the channels and rivers in the coastal and estuarine areas of the Everglades. Mangroves buffer the coast from storms, collect sediment to form new land, and harbor a vast array of birds, reptiles, mammals, and fishes. See my earlier blog post for more details.

Mangroves (NPS)

Hardwood hammocks are dense wooded areas on slight rises. Temperate and tropical tree species mingle here, and because the surrounding lowlands are either wet or not land at all, fire rarely reaches here. The dense canopy creates a dark and humid environment where ferns thrive.

Hardwood hammock (NPS)

Pine rocklands form on high ground around exposed limestone bedrock. These forests are less dense than hardwood hammocks. Fire keeps the understory open and hardwoods at bay.

Pine rockland (NPS)

Marine areas of Everglades National Park also have plant communities. Seagrasses stabilize the bottom, trap sediments, provide a nursery for fishes, and feed underwater herbivores. Lobsters, crabs, shrimp, corals, and sponges are also found offshore.

Florida Bay marine habitat (NPS)

Next week we'll look more at the plants and animals of the Everglades, as well as challenges the region faces. Information and photos this week come from the National Park Service.

I Wanna Rock!

Let’s explore a mystery of geology this week. I recently visited a nearby park known for its unusual rocks. Ringing Rocks features a boulder field of musically inclined rocks that ring like bells when struck with a hammer, rather than clunking like a rock.

Approaching the sonorous stones from the woods

The boulder field is surrounded by a hardwood forest. Within the forest are a few scattered boulders. None of the forest boulders were music to my ears, but supposedly the ones in the boulder field that clank are still ringing, just at a pitch too low for humans to detect. Somehow, the interaction with other boulders is what makes the ringing sound.

Boulder field of musical rocks

The rock type is olivine diabase, an iron-rich volcanic material. Being made from iron probably accounts for the metallic sound. The diabase broke into boulders thanks to Pennsylvania’s wonderful cycle of freezing and thawing. Water finds its way into a crack in the rock, expands when it freezes, and over time causes the rock to fracture.  

Me, demonstrating my musical prowess

The boulders in the field are available for you to gleefully tap with you hammer. On the one hand, this is great because anyone and everyone is free to experience the geological oddity. On the other hand, the boulders show noticeable pock marks from years of hammering. Eventually, the boulders will break. Will they lose their ability to carry a tune when that day comes? No one knows for sure.

This week's information comes from Unmuseum and S. S. McCray (Petrogenesis of the Coffman Hill diabase sheet, Easton Pennsylvania (unpublished B.S. thesis)).

This is a Crappy Subject

Now for the dirtier side of nature. Pretty much every living thing on this planet exists to be someone else’s meal. If you’re unlucky enough to become lunch, the next step is you become poop. No one likes to talk about it, look at it, or smell it. Even though it’s gross, it’s an essential element of the environment for a couple of reasons.

Raccoon scat

The most important function of poop, or scat as we call it in the science world, is a key role in the nutrient cycle. Every living thing needs an assortment of minerals in order to function properly. Minerals are absorbed from the soil by plants, then absorbed by herbivores that eat those plants, then absorbed by various levels of carnivores up through the food chain. Some minerals are present in the ground in rocks; others are returned to the soil through decaying organic matter (plant or animal) or through scat.

Nutrient cycle (from Exploring Nature.org)

Another important impact scat has on the environment is negative, and it goes beyond getting on your shoe. Nitrates and phosphates are common in scat, and also happen to be active ingredients in fertilizer. Excessive nitrates and phosphates in storm runoff causes high nutrient levels in lakes, streams, and even the ocean. Those high levels can cause an overgrowth of algae. Too much algae, even though it produces oxygen, can cause dead zones of little to no oxygen when the algae dies and decomposers feasting on it suck all the oxygen out of the water.

Algae bloom (Michigan Radio)

A third way scat is important is as a research tool. It allows people like myself who rarely observe animals in the wild to see what animals have been down the trail before. DNA samples can be pulled from scat, and population biologists can estimate population by counting turds. Ecologists can study an animal’s dietary habits from looking at scat.

The coyote that dropped this deuce ate a bird

Deer scat

Now that you’ve seen the usefulness of animal scats, maybe you will look at it in a whole new light on your next foray into the woods. Like anything else in nature (except maybe spiders), if you can overcome your aversion, you can learn to appreciate it.