Abandoned Mine Posts

by Andy McAllister, WPCAMR Watershed Coordinator

Crustaceans make up a significant portion of animal communities in all aquatic habitats, from the most extreme ephemeral desert pools to the oceans and everywhere in between. Crustaceans are probably the most well known arthropods because of their contributions to aquatic and terrestrial food webs — not to mention their impact on the economics of the world.

Though arguably the most numerous animals in the marine environment, crustaceans haven’t been quite as successful over the millennia in freshwater and terrestrial ecosystems where they share their habitat with more successful arthropods (principally insects). Still, the diversity of crustacean life in freshwater is astounding.

Crayfish
courtesy Andrews University

As crustaceans feed, they grow, and as they grow they must shed their hard outer covering, called an exoskeleton, and produce a larger one; this process is called molting. Crustaceans molt as they grow throughout their lives, but they molt most frequently during a process called metamorphosis, as they change from larvae to adults.

Seed Shrimp
courtesy Iowa State University

In addition to the most commonly recognized freshwater crustaceans in our streams, crawfish and scuds, aquatic ecosystems are home to some more unusual crustaceans. Ostracods, commonly called seed shrimp, are among the smallest crustaceans. At about the size of a grain of sand, they are easily missed in a stream sample. An ostracod looks like a small clam, but it is actually a type of crustacean that makes this clam-like shell. Although they spend most of their time in the bottom scavenging for tiny particles of dead and rotting material, they can and do swim readily, propelling themselves around like a jet-ski.

All Crustaceans brood their young: as the eggs are laid, they are collected by the female and incubated under or on the outside of the mother’s hard shell. Once the young crustaceans hatch, they leave the mother and are off on their own.

Crustaceans, like many other stream invertebrates, are adversely affected by pollutants, including acid mine drainage (AMD). The hard shell of most crustaceans consists largely of calcium compounds, which are very susceptible to being dissolved by the acids in AMD. According to many reports, crustacean diversity begins to be negatively affected at stream pH levels less than 6.0.

by Andy McAllister, Watershed Coordinator

Limpets, pond snails, sheepnose, heelsplitters, pocketbooks, pistolgrips: the names are as numerous and diverse as the mollusks themselves. The scientific divisions within the Phylum Mollusca are numerous as well.

In Pennsylvania, the most common mollusks are Gastropods (snails) and Bivalves (clams and mussels). The mussel fauna of the family Unionidae in particular, can be found in portions of the Ohio and Susquehanna River drainage basins in Western PA. Freshwater gastropods (snails and limpets), on the other hand, are found practically everywhere.

The feeding habits of the two types of mollusk vary as well. Clams and mussels burrow in the stream bottom and position themselves to pull in water through tubes called siphons and filter out food particles, whereas most snails scrape algae off of rocks and logs with a sort of rasping tongue.

As sedentary filter feeders, clams and mussels are particularly susceptible to being smothered by sedimentation. Mussel populations in Virginia, Tennessee, Kentucky, and other areas of the country with a historically rich mollusk fauna, have declined significantly due to sedimentation from mining sites, such as coal fines and AMD precipitate.

Acidity from mine drainage is another factor that can affect mollusks in a stream. Low pH from acid mine drainage has been shown to reduce the viability of glochidia, the tiny larval forms of mollusks, which in turn, affects the re-population rate (also known as recruitment).

Not only do our native mollusks have to contend with various types of pollution in their habitat, but recently they’ve also had to compete with invaders from other waters. Zebra mussels and Asiatic clams are two mollusks that have invaded the freshwater of the United States. Asiatic clams are small, round clams that compete with native fingernail clams for food and available habitat. The rapidly reproducing Zebra mussel has become the bane of water intake structures throughout the Ohio River and Mississippi River basins, clogging these structures as they attach by the thousands in search of a good spot to filter out their food. Zebra mussels are so abundant and so efficient at filtering food particles from water, that in some areas, they leave water crystal clear with almost no food particles left for the native mussels.

by Andy McAllister, Watershed Coordinator

Alas, the overlooked vermiform, or worm-like creatures, found living in the stream bottom are often misidentified, entirely ignored in the biological sample, or relegated to the most general of descriptions. As we delve into the world of the worm, we find that their world is infinitely more complex than it may seem, with a wide range of variations on the theme “worm.”

Horsehair worm escaping
from its blackfly host

North American Benthological Society

First, we have aquatic oligochaetes (commonly known as aquatic earthworms). Unlike their terrestrial cousins, aquatic oligochaetes are very small and often only slightly thicker than a human hair. These worms adapt well to places where organic pollution is present, such as that coming from an offending wastewater discharge or from cattle. As detritivores (animals that eat bits of dead and decaying organic matter), they happily plow thru the soft sediment, consuming just about anything small enough to fit into their mouths. But don’t be fooled: in spite of their ability to thrive in areas high in organic pollution, aquatic oligochaetes need just the right type of stream bottom. Without the right sediment, large numbers of a particular worm will have trouble surviving.

Oligochaetes are an interesting lot, exhibiting strange characteristics. Some aquatic oligochaetes can swim. Some reproduce asexually by creating long chains of zooids, miniature clones that eventually break off and become separate worms, resulting in population explosions. Some respire through their skin, while others have simple but beautiful gill structures to extract oxygen from the water.

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by Andy McAllister, WPCAMR Watershed Coordinator

Some of the most amazing things come in small packages, and so it is with bacteria. Often maligned and misunderstood, bacteria (plural of bacterium) are powerhouses in the living world, surviving on the most unlikely foods and adding to the complexity of the food chain.

Some bacteria produce toxins that are dangerous to humans, while others are absolutely vital for our survival and the survival of “higher” life forms in the stream. In streams, an enormous variety of bacterial life coats rocks, leaves, and woody debris. Several aquatic macroinvertebrates survive on these bacterial films, often “grazing” on the bacteria as if cows in a miniature field.

From near-boiling hot springs on the surface to geologic strata buried deep in the earth over thousands of years, bacteria can make a home just about anywhere. Some of the most inhospitable places for life are the flooded mine pools that underlie Coal Country and the mine tailings on the surface. Often draining a witch’s brew of dissolved metals and extreme acidity, this water is toxic to most aquatic life. Yet, bacteria survive and can even flourish in these harsh conditions.

Desulfovibrio vulgaris

Virtual Institute of Microbial Stress and Survival, Lawrence Berkeley National Laboratory

Thiobacillus ferrooxidans, for example, is a bacterium that can actually contribute to acid mine drainage (AMD) formation. In the presence of oxygen, T. ferrooxidans creates food for itself by catalyzing, or speeding up, the oxidation of the iron and sulfur, creating AMD. This bacterium, as part of its metabolic process, creates acidity.

Unlike T. ferrooxidans, which love oxygen, Desulfovibrio sp. is one of several Genera of sulfate-reducing bacteria that grow best in the anoxic conditions of some mine pools. They reduce sulfate (an ion present in AMD) to sulfide in a process that causes dissolved metals in the water to drop out and also increases the water’s pH. But these benefits are merely byproducts of Desulfovibrio using sulfates and hydrogen creating the organic compounds (food) it needs to live and grow. Over time, it became apparent to researchers that sulfate-reducing bacteria could become a miniature army in the fight against AMD, and today some passive treatment systems contain Sulfate-Reducing Bioreactors (SRBs). Sulfate-Reducing Bioreactor technology, while still being perfected, holds promise as another tool in the quest to treat AMD.

These microbial reminders not only help improve AMD treatment techniques, but they also help us appreciate the amazing world of the smallest, and seemingly most insignificant, creatures.