Written by Mark Kramer

If most people were asked to imagine a healthy, productive waterway, they would probably visualize a clear mountain lake or salmon filled river. For most of us, clear water is associated with productive water. While gin clear alpine lakes and west coast rivers are beautiful, they pale in comparison to the volume and diversity of life found in estuaries. It turns out that the very nature of the turbid bayou water holds the secret ingredient to aquatic life.

Estuaries are defined by the ebb and flow of tidal exchange. Tide water mixes with rainwater from the surrounding watershed. Tidal streams, such as Armand Bayou are in a dynamic hydrological process. Freshwater rain runoff buffers high salinity levels pushed in by Gulf tides. A Houston sized rain event may drop bayou salinity from salty to fresh water overnight. Salinity levels drive the distribution of all plant and animal life in Armand Bayou. The magic happens where rivers meet the sea, producing an abundance of life that few other ecosystems rival.

The abundance is built on a theme that plays itself out from the arctic to the equator. The Bayou food web’s foundation is built on algae. Algae and plankton are among the simplest plants on the planet. They chase the sun in a slow-motion vertical migration, every day rising to the surface at dawn and then withdrawing into the night. These single celled free-floating algae in the water column are consumed by fishes and add oxygen to the water. 

Filamentous algae grows on the bayou bottom and on dead fallen trees | Photos by Mark Kramer 

Sometimes these simple organisms link together, forming long chains or strands. Filamentous algae grows in the shallows where sunlight penetrates to the bayou bottom. This photic zone only occurs in water less than a couple of feet deep on the tidal flats of Armand Bayou. These tidal flats support lush fields of filamentous algae and are important feeding habitat for many forms of marine organisms.

Sometimes algae may grow on other larger plants. Plants which grow attached to other plants are known as epiphytes. In Armand Bayou, epiphytic algae grow on the stems of marsh plants. Each stem of bulrush and cordgrass is a vertical reef where shrimp, crabs, and mullet graze within the protected, food-rich environment. 

Warm water, long days, abundant nutrients, and bright sunlight promote prolific algal growth in the summer months. It’s a beautifully meshed web of life where juvenile marine organisms drift in on the summer tide to find abundant algal nourishment during the most vulnerable stage of life.

Some of these algae eaters specialize in harvesting free floating plankton from the water. Special adaptations enable the filtering of these tiny plants where they are consumed. Some, such as the Rangia Clam are bivalves who siphon volumes of water through their system daily. During the lowest tides of winter, the mud flats where they live are dry and exposed for a uniquely rare viewing opportunity. This siphoning continues as they sip what water they can from the surrounding mud. They squirt a jet of water towards the sky as if a child with a water pistol was shooting from below.

These crustaceans use special feather-like appendages which sift floating algae from the water as the tide comes in. As the tide falls, the appendages withdraw and are protected inside the body until the next high tide.

Other algae eaters, such as the Bay Anchovy, Threadfin Shad, and Gulf Menhaden have a different filtering strategy. These filter feeders spend all day and most of their life swimming with their mouth open, gathering a meal from this super food. Menhaden and shad are among the most important fish in the Bayou food chain.

Omnivores find ample grazing in the Bayou waters. Crustaceans such as shrimp and crabs use specially adapted pincers to snip bite-size morsels of filamentous algae. 

Striped mullet and Armored catfish (aka Plecostomous) make a good living by feasting on epiphytic algae found on the stems of marsh plants. During the summer, Smooth Cordgrass stems dance as mullet lunge to grab a mouthful of living green velvet. 

Armored Catfish are sold through the aquarium trade as “Algae Eaters” to help keep aquarium glass clean. Home aquarium hobbyists contribute to the problematic spread of invasive species by releasing aquarium fish into public waters. 

 Notice the cluster of eggs attached to the shrimp’s abdomen | Photos by Mark Kramer

This gravid grass shrimp feasts on epiphytic algae along the marsh edge. As her young are born, they’re eaten by one of the most unusual fish in Armand Bayou. Gulf Pipefish are members of the seahorse family and are one of the most beautifully fragile of all bayou fish.   

Predators galore reap the bounty as sunlit energy passes from algae to the top of the food chain. Many of the most sought-after coastal gamefish build their populations through this complex food web.

Scavengers are the clean-up crew. Numerous species of freshwater and saltwater catfish and gar make an easy living.

Salinity levels drive the distribution of all plant and animal life in estuaries such as Armand Bayou. Saltwater fishes such as this Gafftop Catfish are found in the extreme southern reach of the bayou adjacent to Clear Lake where salty tides enter.  

Upper Armand Bayou is characteristic of any east Texas freshwater stream. Here, freshwater plants and animals compose the assembly of life. Bass, sunfish, catfish, crappie, smallmouth buffalo, and gar are some of the river species which occur.

Some aquatic species are newcomers to the bayou. Some of these animals found their way here accidently. Others were intentionally released into the waters of Texas. Asian Grass Carp were intentionally released into east Texas reservoirs by state agencies in an attempt to control invasive aquatic plants (hydrilla). Grass carp escaped from these lakes, migrated down rivers and entered into Galveston Bay. They migrated through the bay and entered into Armand Bayou where I first encountered them in 1995. The fish have pharyngeal teeth which enable them to consume large amounts of plant material. Asian Grass Carp are big fish which may weigh up to 60 pounds and may eat twice their body weight in plant material every day. This voracious appetite has been known to have significant impacts to valuable wetland habitats.

In a relatively short stream section, there is a tremendous diversity of freshwater and saltwater aquatic life. Traveling just under seven river miles on Armand Bayou, you’ll encounter many species typically found in Galveston Bay and others that are associated with east Texas river systems.

If only somehow, we get could get a glimpse of what is below the surface. If only I could use my Naturalist Magic Wand and we could transform the water to the clarity of a mountain lake, allowing us to see down twenty feet into the water, even if only for a few minutes.

If we could have that clarity of vision, we would have a mind-blowing experience. We would see shrimp and crabs clinging to the bulrush and cordgrass, browsing on the epiphytic algae on their stems. We would see schools of striped mullet grazing on fields of filamentous algae covering the shallow floor of tidal flats. We would be shocked to see huge schools of Gulf menhaden stretching shore to shore with hundreds of thousands of small fish in each school. Menhaden swimming choreographed like a huge flock of blackbirds, changing direction in unison. With our enhanced vision, we would see hundreds of ladyfish chasing those schools of menhaden into a tight ball, slashing through the water’s surface, erupting from their pursuit. We would see the Bayou’s only member of the seahorse family- the Gulf Pipefish- stalking through the marsh grasses, hoping to find tube worms or tiny grass shrimp for a meal. We would see wading birds of every shape hunting the marsh edge for an easy meal. We could see mullet just below the water’s surface with a hovering osprey overhead, locked on its prey, preparing for a spectacular dive. Looking into the depths of the bayou, there are large blue catfish and alligator gar cruising their domain for any scraps settling down from above. Shifting our gaze, we see the alligator quietly waiting, patiently anticipating that a Great Blue Heron might land within striking distance. We would see the fast and agile American river otter gracefully catching blue crab along the marsh edge. That’s all happening right now, typically hidden from view in this complex ecosystem. 

Here, life is built layer upon layer, interconnected and co-dependent, just like all of the old Indian chiefs said. It turns out that we are all related. From sunlight to algae. From algae to fish. From fish to my dinner table. The abundance of life is hidden below the surface, obscured from human view in the rich, cloudy bayou water. Because of the veil of algae hiding the life below the water’s surface, bayous don’t get the ecological respect that they deserve. If only we could get a glimpse into the secret world. Into these living waters.