Estuary Basics
The Hudson is really two rivers: a freshwater river that starts in the Adirondacks and flows south to Troy, NY where it spills over the Federal Dam. The river’s identity changes from a fast moving mountain stream to a wider river that passes through upstate farms and forests, past old industrial plants including paper mills and the factories where GE disposed of PCBs. During this part of the journey, the river’s elevation drops from over 4,000 ft. to about 4 ft. From Troy to the Battery in NYC, a distance of over 150 miles, the river is barely above sea level. This means that it is subject to the tidal effects of the ocean. This section of the river is defined as an estuary, a place where fresh and saltwater meet and where the ocean’s tides are a major influence on the river’s flow.
This aspect of the Hudson is what seduced Henry Hudson into believing that the river might be the legendary Northwest Passage. The river was tidal, flowing south to north and then switching directions. It was also salty far upriver.
This saltwater-freshwater nature can prove challenging for fish, but some species can take advantage of this, spending part of their lives in the Hudson and another part in the ocean. Striped bass, American shad, and sturgeon spend much of their adult lives in the ocean, returning to the Hudson to lay their eggs (spawn). This strategy (used also by salmon, though there are no salmon in the Hudson) is called anadromous. American eels do the reverse, spending most of their lives in the freshwater part of the Hudson before returning to the ocean to spawn. This is called catadromous.
The Hudson is also a fjord, a drowned river valley cut by a glacier. Some 20,000 years ago, a miles worth of ice lay on top of the Hudson Valley. The massive glacier cut through the mountains and eventually left a pile of debris as it retreated became Long Island. The fjord nature of the river is evident in the Hudson Highlands near West Point.
Read The State of the Hudson! This is a comprehensive report published in 2009 by the New York Department of Environmental Conservation covering a variety of current issues on the river.
Fish
Over 200 species of fish live in the Hudson watershed. Some fish are native to the Hudson (white perch, Morone americana, while others, like the common carp, Cyprinus carpio, are invasive, unwelcome and sometimes destructive guests. The Hudson estuary is a great example of biodiversity. Giants like the Atlantic sturgeon, Acipenser oxyrinchus, patrol the river bottom eating shellfish and sometimes leaping into the air much to the astonishment of onlookers. Others are tiny, like the three-spined sticklebacks, Gasterosteus aculeatus, where males make nests by gluing together bits of vegetation.
You can tell a lot about a fish by its adaptations. Adaptations are tools for survival. For a fish, these include the shape and size of its mouth, coloration, ability to process salt, lateral line, and fin structure. The lateral line is a distinct line along the side of some fish. Inside the line are cells with tiny hairs that are sensitive to movement in the water, sort of like built in motion detectors. Look for this feature at the fish station.
When you visit the fish station, try to figure out what the fish’s niche is. A niche is the role a species plays in its ecosystem. Some fish are generalists, like carp, while others are very specialized, like a seahorse. Some fish are apex predators at the top of the food chain (striped bass). Other species swim in schools, like killifish and are often eaten by larger fish. Still others are scavengers, like catfish.
Hold the anchovies! Yes, the Hudson River has anchovies, though not the same ones found on pizza. Bay anchovies, Anchoa mitchilli, have eyes out of proportion to their heads, and a big overbite. They can open their mouths wide to strain the water for plankton. Plankton is anything living in the water that can’t swim faster than the current. Most plankton is small, although some jellyfish can reach dozens of feet long. Plankton is either phytoplankton (like a plant, photosynthetic) or zooplankton (animal). Plankton is a crucial part of the Hudson food chain.
Striped bass, Morone saxatilis, are predators that rule the top of the fish food chain in the Hudson, but they are only temporary visitors, spending most of their lives out in the ocean. American shad, Alosa sapadissima, also only visit the Hudson to spawn. Shad “roe” is considered a local delicacy, but shad numbers have dropped so low in the Hudson that fishing for them is no longer allowed.
What’s a hogchoker, Trinectes maculatus? We call them the “sole of the Hudson”. This little flatfish is the unofficial mascot of Clearwater. What is this fish’s niche? What are its adaptations? How did they get that bizarre name? Ask onboard.
Imagine a species of fish that has been around since the time of the dinosaurs, with bony ‘scutes’ instead of scales, and a mouth that looks like a vacuum hose. That’s the Atlantic sturgeon, the largest fish in the Hudson. Sturgeon eggs are valuable as caviar, an expensive delicacy. Once called “Albany beef” because they were so plentiful, but now fishing for sturgeon is no longer allowed. Why not?
Clearwater and many other river organizations are constantly monitoring and educating the public on our fish populations. Read the Pisces Report, published by Riverkeeper in 2008, which looks at thirteen key Hudson River fish species to discover the challenges our aquatic communities face today.
Invertebrates Station
Animals without backbones- in the Hudson, these can be tiny, Cyclops-like copepods or large blue crabs. The world of invertebrates is vast and diverse and they can serve as indicator species, telling us about the health of the ecosystem in which they live by their presence or absence. There are the mollusks, like oysters and clams. Crustaceans include crayfish, crabs, barnacles, and shrimps. The freshwater parts of the river are home to many insect larvae, which may eventually transform into adult mosquitoes, mayflies, midges, dragonflies, or beetles. Then there are shell-less worms, including leeches and clamworms.
At the Hudson River life station, the invertebrate you are most likely to encounter is the humble amphipod (Gammarus), often called a “scud”. Scuds look like tiny shrimp and scavenge along the river bottom, eating detritus, which is dead plant and animal material. A tremendous amount of energy enters the Hudson from dead plants, like leaves washing in from the tributaries. Scuds do a great job of cleaning up the bottom of the river and they provide food for a host of fish species.
Copepods are probably the most numerous animal group on the planet. They are vital to river and ocean food chains, providing food to larval fish that are just getting started in life. They’re very small, but you can see them with the naked eye.
Are there any zebra mussels, Dreissena polymorpha, in your sample? These invasive mollusks got into the Hudson River accidentally when free-swimming larvae escaped from the ballast water of ships from Eurasia. Once in the Hudson, zebra mussels reproduced at a fast rate. They attach themselves to any hard surface, including boats, pipes, docks, and even the shells of native clams, by secreting byssal threads. Zebra mussels also filter the water, removing plankton and oxygen from the water. You will only find zebra mussels in freshwater. They are intolerant of salt.
The Hudson is known for its blue crabs Callinectes (“beautiful swimmer”) sapidus (“savory”). These crustaceans move into freshwater parts of the river during the summer. Their ten legs have different jobs: the first pair are the dangerous claws; the middle three pair are walking legs; the back legs are flattened, serving as paddles and making this crab an effective swimmer.
Chinese mitten crabs, Eriocheir sinensis, are a recent arrival in the Hudson. They are potentially an invasive species (any animal or plant that has arrived from another place and has become destructive in the Hudson). Mitten crabs are known for the hair-like tufts on their claws that resemble mittens. The exact purpose of these “mittens” is unknown. These crabs lack the swimming feet and are designed more for walking and burrowing.
More invertebrate resources from this USEPA website.
History Station
2009 marked the 400th anniversary of Henry Hudson’s voyage to the river that bears his name, but we know that the Hudson’s history dates back long before it was called the Hudson River. The sloop Clearwater is like a time machine in many ways. The boat is a replica of cargo vessels that sailed the river from the 1700s through the 1800s. They were the tractor-trailers of their day, and the Hudson was the highway that served as the lifeline for communities like Albany, Hudson, Kingston, Poughkeepsie, Newburgh and New York. Hudson River sloops like the Clearwater carried just about anything that needed to be carried up and downriver, from bricks, stone, and hay, to live animals, the mail, and paying passengers.
Down below in the sloop’s main cabin you will get a taste of what it was like to live on a sloop and you’ll work through an interactive timeline of Hudson history that stretches from the time of the Native Americans through the Dutch settlers, the English and the America of today. Check out the stained glass windows that tell the story of the Hudson through time.
Why were beaver pelts once used as the equivalent of money? The cities of Hudson and Poughkeepsie were once home to whaling companies. Were there whales in the Hudson River? What part of the river once was blocked by a giant chain and why? What famous pirate once made New York City his home? Why did the river sloops fade from history? What replaced them? Why did the Native Americans call the Hudson River “Muheakannatuck”?
From the Hudson River School painters to the beginning of the modern environmental movement, the Hudson has helped shape America’s relationship with its land and water.
The Hudson River has changed dramatically since Henry Hudson first sailed upriver in 1609. How will the river change over the next 20 years?
Navigation Station
Whether it is biking to work, walking to school or giving directions to a friend, we use some form of navigation every day. When you come aboard Clearwater, you will find that our captain and crew do not rely on a GPS or digital chart plotter to navigate the ship. Students, volunteers and crew alike use paper charts of the river, compasses, visual aids and simple math for river navigation. Lighthouses, floating buoys, bridges and even church steeples are navigational aids for determining the location of the vessel as well as direction and speed of travel.
Unlike navigating on land, there are a few extra factors that must be taken into account when charting a course on the river.
Because the Hudson is a tidal estuary, the ever-changing current is often the most important influence on the boat’s progress along the river. On a three-hour sail, Clearwater might leave the dock with the tide going out, pulling us towards the ocean, only to return to the dock with the water flowing in the opposite direction. At times the strength of the current is so great that even with our sails full the boat moves backwards. When you are near the river, tossing a stick in the water is a great way to observe the direction and speed of the current. The amount of rainfall can affect the currents but they are primarily determined by the sun and moon’s gravitational pull, creating high and low tides. The tides can be predicted far into the future with great accuracy and these are published for mariners to consult in tide tables.
Wind in the sails is the power propelling Clearwater across the surface of the water. The speed and direction of this mighty force is constantly changing and affecting how fast and in which direction the boat will move. There are many ways to observe the wind’s activity; such as a wind speed indicator, surface water texture, a flag flying or the feel of it across your skin. The wind direction and strength will help the captain determine Clearwater’s course and when to make maneuvers such as, tacks or gybes. Our sail physics lesson goes into more detail here but, for more information on apparent wind, points of sail and trimming sail: click here.
Determining the water depth is also essential for fishing and sailing safely on the Hudson River. This can be done with a number of tools such as a sonar depth sounder or lead line. Clearwater was specifically designed for this river, so it goes only six and a half feet below the surface of the water with our centerboard up. With such a shallow draft, much of the Hudson is accessible to us, however, if we navigate into shallower water, the vessel would be resting on the bottom.
Water Quality Station
Water is known as the universal solvent. The waters of the Hudson have many chemicals dissolved in them, distilled from the rain that passes over the watershed, the surging ocean, and pollution. At the water chemistry station, you will measure some of the chemicals that affect the quality of the water and the life living in it.
Oxygen
Every breath we take has contains about 21% oxygen. That’s a huge amount compared to what’s available to fish in the water. Even though water is made up of oxygen (H2O), that oxygen is not useful for breathing. Instead fish and other aquatic organisms must rely on oxygen that’s dissolved in the water. Oxygen in the water is measured in parts per million (or milligrams per liter). Four parts per million (4ppm) is considered the minimum amount of oxygen to sustain fish life. Some species (like trout) need much more while others (like carp) can survive at very low levels.
On Clearwater, we test the oxygen levels using something called the Winkler method that involves titration. You will add drops of an indicator solution to a prepared sample of Hudson River water and look for a color change. Once the sample turns from yellow to clear, the test is over. The total number of drops represents the amount of dissolved oxygen (DO).
Just because the water may have 4 or more ppm of dissolved oxygen, that doesn’t mean it is healthy. What if the sample you tested had 5ppm but should have much more, maybe 9ppm? If the water isn’t holding all the oxygen it should be, that might be an indication of pollution, such as sewage. To figure this out, we take the water’s temperature. We know how much oxygen the water should hold at a given temperature. Colder water can hold more oxygen than warm water. Using a special chart and our DO and temperature data, we can see if the water is close to saturation, or if it should be holding more.
Sometimes sewage spills into the Hudson. That provides food for bacteria and the bacteria multiply, using up lots of oxygen. So the water may have 5ppm, but we can test to see if it should have more.
pH
We will test the acidity/alkalinity level of the Hudson using a simple pH test. The lower the number, the more acid a sample is. Seven on the pH scale is neutral. Rainwater is normally slightly acid at around 5.5, but acid rain can be much more acid (around 4). Each point on this scale represents 10 times more acidity, so a pH of 5 is ten times more acid than a pH of 6 and a hundred times more acid than 7. This is called a logarithmic scale. What was the pH of your sample?
Salinity
Even freshwater streams have some small amounts of salt dissolved from the land. But the Hudson is an estuary and the influence of the ocean can be strong. Saltwater moves far upriver, creating something called the salt front. This is the point where measured amount of ocean salt (100 mg/l) can be detected in the river. You couldn’t taste this amount of salt in the water, but it’s an indication of the ocean’s presence. Saltwater is denser than freshwater and this tends to inhibit mixing. During the spring, with all of the snowmelt from the mountains, huge volumes of freshwater push the salt front down toward the ocean. By late summer, much less water flows into the Hudson, so the ocean saltwater gets a chance to push north. To find out where the salt front is today, click this link: http://ny.water.usgs.gov/projects/dialer_plots/saltfront.html
This all proves a challenge to fish. Salt can be a limiting factor, determining whether or not a fish can live in a certain area. Some fish are not very salt tolerant (carp) and need freshwater. Some need to be in fairly salty water (sea robins). But in the Hudson, there are fish that can adapt to varying levels of salinity. Eels, white perch, banded killifish, and hogchokers are all in that category. Some fish, like shad and striped bass, spend most of their lives in saltwater and only come upriver to spawn. This is called anadromous. Eels, on the other hand, spend most of their adult lives in the river, returning to the ocean to spawn. This is called catadromous.
Turbidity
This is a measure of total suspended solids (TSS). The Hudson is naturally turbid. Much of this material washes in from the tributaries. It is mostly fine clay particles, so fine that the water keeps them in suspension. Too much turbidity is an indication of soil erosion. Hudson River fish generally have a high tolerance to turbidity. We can measure it using a Secchi disk, which measures the water’s transparency. The more turbid the water, the harder it is for light to pass through it. We have a Secchi disk on the boat. Try it out.
HRECOS
In 2010, Clearwater will be equipped with sophisticated water quality monitoring equipment and be part of a river-wide network that measures water quality. The network is called HRECOS (Hudson River Environmental Conditions Observing System) and provides real time data, relayed back to the Internet, where anyone can access it. Visit HRECOS here: www.hrecos.org. You’ll soon be able to track Clearwater on our website as well through this system.
Also, your school can be part of a river-wide assessment program- A Day in the Life of the Hudson River (Snapshot Day). Check out this site:
http://www.ldeo.columbia.edu/edu/k12/snapshotday/
Sail Physics Station
Geology Station
The geologic history of the Hudson River and the Hudson River Valley is not only important in understanding the topography or the regions and the formation of the river as an estuary, but also in the development of the region and its invaluable place in history.
Geology is the study of the Earth. The Earth is made up of rock and so geology is largely the study of rock. When you look around you at the landscape of the Hudson Valley you are looking at its geology. The rocks and terrain of an area hold the clues to that regions history. Each rock tells a story.
Rocks are classified based on their mineral and chemical composition, by their texture, and by the processes that created them. All rocks are made up of minerals. Minerals are a naturally occurring solid that have a specific chemical composition, ordered atomic structure, and specific physical properties. The Rock Cycle portrays the origin and formation processes of the three main types of rock: igneous, sedimentary, and metamorphic. We have examples of each type of rock, most found on the banks of the Hudson River for you to examine.
Hudson River Sloops carried rocks and minerals on their wide decks all up and down the river, sailing past cliffs and mountains. Iron ore, limestone, trap rock, emery, granite, and clay all natural resources found in the Hudson Valley, many are still transported on the water today. Bricks were made from glacial till deposites represented a huge industry in the Valley, we still find pieces of the red clay blocks near abandoned brickworks along the banks of the river.
Glaciers played a large part in the formation of the Hudson River Valley. As glaciers moved across the landscape they picked up silt, sand, rocks, and boulders and later set them down in deposits of glacial till.
During the glacial era, a large amount of water was trapped in the massive ice sheets. Sea level was more than three hundred feet lower than it is today so the river flowed miles farther across the continental shelf before reaching the sea. As the mile high glaciers began to melt, Glacial Lake Iroquois was formed which eventually burst its ice damn and flooded the Hudson Valley. The new path of the river allowed seawater to enter the mouth of the Hudson making it a tidal estuary and burying the Hudson Canyon under water.
There are many glacial formations that can be seen in the Hudson Valley region and without the geologic resources and the modern course of the Hudson River, the Hudson River Valley would never have been as important or as treasured as it was and is still is today.
Simple Machines Station
Simple Machines are tools sailors’ use aboard Clearwater to help make our work easier. We use many simple machines every day to steer the ship, raise the sails, open buckets, cut wood, fix planks, and lift heavy loads. There are six different simple machines: a lever, a pulley, a screw, an inclined plane, a wheel and axel, and a wedge.
Here are illustrations and descriptions of each simple machine! Notice how they are related to each other and where you might see them used: click here.
Even with these simple tools, you don’t get something for nothing. With each advantage these tools provide, we must give something up in return. For instance, Clearwater’s tiller is very long making it easier to turn the boat than if we had a short tiller. But what the crew gives up is a great deal of deck space. A longer lever makes a load feel lighter, but you have to push the end of the lever much farther than your load is ultimately transported. This is a dynamic example of the Mechanical Advantage formula: work = force X distance. Try it! When the captain gives you a tiller command, try pushing from the very end of the tiller and then from half way down the tiller.
Mechanical Advantage is the factor by which a simple machine magnifies the force applied, essentially making you stronger! If you are able to lift 50 pounds to your waist without breaking a sweat and then use a level that has a mechanical advantage of 2, you will be able to lift 100 pounds to your waist without breaking a sweat. It will take the same amount of work to lift twice as much weight with this simple machine. However, the end of the lever, just like our tiller, will move twice the distance of your waist to the ground.
Another great example of a simple machine used aboard Clearwater are the pulleys. Sailors call this useful tool a block. Everytime we raise the sails, blocks are used everywhere. When you come aboard, keep an eye out for the largest block and the smallest block. What you gain and give up by using a pulley is the same as with our tiller. We can haul up our 3,000 pound main sail with a class of fourth graders, but it takes a long rope, or halyard. Imagine how long the rope would have to be for one lonely sailor to lift the sail alone, at some point team work out weighs mechanical advantage.
Simple Machines are tools for helping sailors work smarter rather than harder. How do you use simple machines in your life? Do you see opportunities for using your salty skills and making your work more efficient?
Knot Tying Station
Sailors use knots every day to help make their lives and work easier or more efficient. Different knots are good for different jobs on and off a vessel. The knots you learn onboard Clearwater will help you at home, at work and are great for impressing friends! As a volunteer onboard the vessel, helping to sail Clearwater involves some use of knots. You will employ these skills when helping the crew set the sails, dock the ship and tidy the decks, as well as teaching them to students.
When we learn and teach knots, it can be fun to use a rhyme or story to go along with the twists and turns of rope. These can help you remember how to tie the knot and to which job it is best suited. Soon you will know which knots these adages are describing: “A bridge over two waters” or “bunny comes out of her den around the tree, and back in her den.”
Some of our favorites are the bowline, stopper knot, clove hitch, a round turn and two half hitches, square knot, daisy chain and the highwayman’s hitch. After you learn to tie your favorite knots onboard the deck of Clearwater, every time you use it for the rest of your life, memories of the challenges you faced and the skills you learned as a sailor will come back to you. Repetition and review of knots are always helpful so when you need to use the knot your hands remember the moves and you can tie like an old salt. Here are a few instructions for the knots to learn and practice before coming to the boat: Animated Knots
Art Station
