From the June 2010 Conservationist
DEC scientists evaluate stream health by counting critters
By John Razzano
Our truck crawls over a narrow tangle of roots and rocks that might be mistaken for a trail instead of a road. We're hemmed in on both sides by a thick canopy of trees that immerse us in deep shade. On this cool, clear, late-summer morning, I'm tagging along with a stream-sampling team, looking for a remote site on a creek somewhere in New York's Southern Tier. I glance at the rearview mirror for the other half of our crew, photographer Sue Shafer and biologist David Newman. "I think we lost them," I say. "Their car doesn't have the ground clearance," replies A.J. Smith, supervisor of DEC's Stream Biomonitoring Unit (SBU) and backwoods driver.
A.J. is one of the "bioneers" (a term I coined after spending time in the field with them) of stream biomonitoring. This nearly four-decades-old field of environmental biology combines both simple and increasingly sophisticated techniques to evaluate water quality in streams and rivers by examining their aquatic biology; specifically, their benthic macroinvertebrate communities.
Stonefly nymph (Photo: Missouri Dept.
of Natural Resources)
Benthic macroinvertebrates are creatures that live in a stream's bottom, and are at the bottom of the food chain. They are visible to the naked eye, and include everything from worms and leeches to the larval forms of beetles and flies. To a trained biologist, these organisms speak volumes about stream water conditions. They are ideal indicators of chronic, not just occasional, water contamination problems, because, unlike fish, they can't just swim away when pollutants degrade their habitat.
Since 1972, the SBU has sent out two-person teams to sample selected creeks and rivers across New York State. Visits are rotated annually among the 17 major basins of the state to try and sample all the collection sites at least once every five years. Today's trip is part of the study of the Delaware River basin.
"We should have seen the creek by now," A.J. says, jerking the truck to a stop. He unfolds a map, checking it against the screen of a handheld geographic positioning system (GPS) device. "I think we should have turned a few seconds ago," he says, shifting the truck into reverse.
We reunite with the others, and then pull off the road at the exact spot indicated on the GPS. Jumping from our vehicles, we clamber into hip boots-there's no graceful way to do it-and unload the sampling equipment we'll carry on the short walk to our first site on Kerr Creek in the Town of Walton, NY. Our equipment is a combination of high-tech electronics for measuring some of the stream's key physical and chemical properties, and low-tech tools like a rectangular collecting net mounted on a long pole.
Cool, clear, shaded mountian streams
contain plenty of dissolved oxygen - the
perfect condition for a variety of insect
and other invertebrate species. Carefully
analyzing which species thrive in an area
tells biologists a lot about a stream's
chemistry and water quality.
Bushwhacking our way down a steep bank, we reach the creek, a beautiful mountain stream with crystal clear water dancing over a rock-strewn bottom. Trees on both banks form a lush green umbrella over us.
The first order of business is figuring out the best place to sample. The water must be shallow enough to easily wade in our hip boots, but have a long enough stretch of riffles (shallow rapids) to provide a lively current over the required sampling distance.
Surveying the scene, A.J. leads us upstream. Jumping from boulder to boulder and picking our way over slippery rocks, we reach a good site. A.J. reads off the coordinates from the GPS while David notes the precise latitude and longitude.
Digital photographs are taken for a visual record, and then David uses an electronic instrument to measure some of the stream's physical and chemical properties, including stream conductivity, dissolved oxygen levels, pH and temperature. This information is correlated with the biological data to complete the picture of the stream's condition.
David continues to take notes as A.J. dictates a series of observations about the stream: estimated current speed; channel width and depth; vegetation, slope and soil stability of each bank; and make-up of stream bottom (gravel, sand, stone).
Preliminary tasks complete, it's time to discover what benthic macroinvertebrates live here. We'll snag our quarry using a simple technique called "kick sampling." Actually, the method could as easily be called "shuffle sampling." The idea is to hold the kick net before you as you shuffle along downstream for a prescribed time and distance, kicking up sediment, stones, plant debris and anything that lives on the bottom, and letting the current wash them into the net.
A.J. finds a good route through the stream, rinses the net to billow out its mesh, and begins shuffling his way downstream. After five minutes, he hauls out and sloshes over to a flat boulder where a shallow, white-enameled steel tray partially filled with water sits waiting.
Mayfly (Photo: David Cappaert,
Michigan State University, bugwood.org)
The net is emptied into the tray for a quick review of its contents. Stones and other larger pieces of detritus are discarded, but not before aquatic organisms are brushed off and saved with the rest of the sample. The tray instantly becomes a shallow aquarium, teeming with a host of bizarre but fascinating-looking creatures. I'm instantly transported back to my childhood when I use to turn over rocks in a nearby stream and wait until the water cleared to see what I uncovered.
The three macroinvertebrate groups that are the gold standard of clean water-larval forms of mayflies, stoneflies and caddisflies-are plentiful. Other creatures more tolerant of pollution, like aquatic worms and midge larvae, also occur, but in smaller numbers. A.J. makes a fast estimate of the relative diversity and density of various organisms, and, as expected, assesses the fauna at this site as "very good," with a healthy and diverse macroinvertebrate community.
Field assessment complete, the sample is strained and placed in a plastic jar. Back at the truck, 190-proof ethyl alcohol is poured into the jar, instantly pickling the organisms. The jar is labeled with the site name, number and date, and kept with other collected samples until the crew returns to the office in a few days. Piling back into our vehicles, we drive to another sampling site a mile downstream. Once again, the kick sample reveals a diverse, healthy community of bottom dwellers.
Finished with Kerr Creek, we move on to a site on the West Branch of the Delaware River in the Town of Beerston, NY. Here, I get a turn to do the "riffle shuffle" and haul in some water bugs.
As expected, the West Branch is much bigger than Kerr Creek. In fact, the channel is about 75 feet across, with clear water and a fast, strong current. As we hike along the shore to the sampling site, I stare nervously at the racing torrent.
Since this site has been sampled many times before, A.J. knows just where to go. Arriving at the spot, A.J. hands me the kick net, saying "Here you go. Walk out a few feet and start your run." The soft sand and gravel bottom near shore quickly turns to large, slippery stones. I gingerly concentrate on every step. "This isn't as easy as it looks!" I shout over the rushing water. "You're doing fine!" A.J. yells, "That's good! Start there!"
I turn downstream, steadying myself with the pole of the kick net. The force of the current instantly increases, pushing my legs from behind and pulling my arms as the net bulges with water before me. I advance slowly, digging in and turning each boot as I go. Even in thick rubber boots, this kick-twist motion is hard on my feet. After only about two minutes, much sooner than the usual five, the net is too heavy and I have to haul out.
We immediately see the problem-the net is full of large, round stones; so full in fact, that the mesh has started to tear! We all share a good laugh as I ask, "Is this going to be any good?" "Bring it over. We'll check it out," answers A.J.
Looking through my net full of rocks, we notice that some are capped with green toupees of aquatic plants. A.J. is concerned about this abundance of bottom vegetation, which can signify excess nutrients like nitrogen and phosphorus in the water. Excess nutrients can come from a number of sources, including leaking septic systems, runoff from fertilized farm fields and suburban lawns, or inadequately treated water from aging sewage treatment plants. Like many states, New York is facing a looming crisis with regard to updating our aging water treatment infrastructure.
Removing the contents of the net, we discover I caught more than just rocks. Beetle larvae called water pennies are attached to some of the rocks and we notice fingerling bullhead as well. A.J. scrapes off diatoms-a form of slimy algae-from some of the rocks, and we also find rusty crayfish, an invasive species named for the red spot on its carapace.
Because my run was cut short, A.J. decides to tie a knot in the torn net and take another sample. Despite his concerns that the abundance of weeds may indicate a potential problem, he assesses the aquatic habitat as "very good" because his sample reveals a healthy balance of mayfly, caddisfly and stonefly larvae. With that, the field component of our sampling is complete.
Three months later, my photographer colleague Sue and I pull into the SBU's offices in Troy to see what happens to the stream samples in the lab. Once again, A.J. is our tour guide.
While summer days are reserved for
stream sampling, winter lends itself to
laboratory analysis, wherein samples are
more completely indexed and the biota
more closely identified.
The lab is lined with shelves and cabinets filled with sample jars. Long countertops hold computer workstations, stereomicroscopes, and other equipment used to analyze samples. One entire wall of shelves has nothing but jars labeled with the Latin names of the macroinvertebrate species they contain. These are reference samples for use when biologists are trying to identify a particular specimen and need to compare it to a confirmed example.
A large, clear acrylic cylinder mounted on a metal control box contains several jars of fish and crayfish. It's explained that this is used for freeze-drying tissues of various organisms. The freeze-dried organisms are analyzed at another lab for contaminants that can accumulate in the tissues. This is usually only done when particular pollutants, like pesticides or toxic metals, are suspected.
A.J. introduces us to two aquatic biologists, Diana Heitzman and Brian Duffy, who count and identify macroinvertebrate species. As they analyze the faunal community in every sample, they log each species and their numbers into a computer database.
Samples are prepared for analysis by pouring off their alcohol preservative, removing larger pieces of detritus, and placing a small amount of material (a subsample) on a petri dish. This subsample is carefully examined under a stereomicroscope, and 100 organisms are counted out. Brian is sifting through a subsample with two pairs of forceps, poking and pulling macroinvertebrates into groups according to their biological family and genus. There is a digital camera attached to his microscope so he can create a permanent record of each organism. As he sorts, he counts the groups of various creatures: 23 Ephemeroptera (mayflies), 18 Plecoptera (stoneflies) and 15 Trichoptera (caddisflies), among others. These three families are called EPT for short. A sample rich in EPT species most likely came from water that is clean.
Once Brian has finished sorting and counting, he passes the sample to Diana who uses a stronger compound-lens microscope to look at very fine distinguishing details. Such close scrutiny is the only way species can be positively identified. As she works, Diana notes how many of each species she finds among the 100-organism subsample, further refining the census.
And so it goes, year after year. A.J., David, Brian, Diana and DEC's other stream "bioneers" continue to sample the state's vital network of water courses, finding satisfaction in discerning what the humble bottom dwellers they collect say about the health of the environment. For in studying these lowly creatures, they help ensure that our irreplaceable streams and rivers will continue to sustain all life on this water planet we ironically call Earth.
John Razzano is a contributing editor to Conservationist.
Photo: Susan Shafer