10 May 2014 found me admiring spreading willows and a magnificent old Burr Oak on the bank of the Trent River at a Conservation Area near Glen Miller, Ontario. We'd come for spring drifted mollusc shells, and we only noticed the "Line 9" pipeline river-crossing signs just as we were leaving. Our colleagues Amanda Bennett and Matt Keevil evidently hadn't noticed the pipeline crossing either, during years of launching their boat here as they studied the turtles in this stretch of the river. Our formal description of this “limestone savannah rare habitat” is “lawnpark bank of rapid canal-river, in residential area.”
After a day of collecting spring-drifted shells from creeks and rivers in Toronto we zoomed alog the 401 to the parking lot here and slept in the seats of the van until dawn. While I made breakfast, Fred sprinted for our traditional drift sample up near theTrent/Severn lock. He found handsfulls of chaffy drift from the eddy above the bridge. Much of the deposit was chunks of Cattail leaves hung up on the bedrock shore below Eastern Red Cedar and Common Juniper. As he returned to the van with bags of drift, a male Baltimore Oriole moved through the oaks above us, the second one we'd sighted this year.
On our way out of the Conservation Area we stopped at the sign identifying the Line 9 oil pipeline crossing and gathered another sample of somewhat sorted drift among limestone slabs at the river edge. There is so much plant material that we see very few shells in drift from here, but we gather it as a historical record of what's present each year, and the samples are available for study, preserving a history of what's washed down the river. Detailed sorting will find lots of tiny land and aquatic snails, insect parts, and the fruits and seeds of native and invasive plants.
Our visits to this site began on 16 April 1994 when we picked up handsfulls of storm drift, and then, across the river, heard no calling by Frogs as we established an nighttime auditory monitoring station. On 5 May Fred and Lee Ann Locker heard a small chorus of Toads, on 29 May a Woodcock was peenting and flight-singing, and on 31 July a few Green Frogs were calling, barely audible through industrial, highway and cricket noise. On 29 May we watched an Osprey (Pandion haliaetus) flying upstream over the river – a less frequent observation then than it is now, as the species' recovery from DDT is more complete and Ospreys are now often seen over many Ontario rivers.
On 22 April 2005 we began our regular sampling of drifted shells here from the surface of flat slabs of rocks that harden the shoreline, bordered by a wide floating mat of Cattail leaves and rhizomes. On 17 April 2006 we collected a sample of Eastern Elliptio mussel shells, old and worn, remnants from before the Zebra Mussels took over the river in the early 1990's - and on 25 April 2008 Fred noticed that "the site was advertised on a sign, as "limestone savannah," a "rare habitat." We didn't collect a bloated yellowish adult Whitetail Deer floating below the lock gates, but did take a sample of shells washed up on shore along a seething carpet of one-metre scale Cattail mats, some of them sprouting, 60 cm-wide bobbing sawn sections of Willow trunks, big rounded chunks of styrofoam, plastic water bottles, and smaller chunks of plastic – all in a matrix of Cattail leaf segments. We found a few remains of the invasive Orconectes rusticus (Rusty Crayfish) left by predators on the surface of the drift mat, and saw a Water Snake (Nerodia sipedon) that slipped into the floating mat from rocks on shore where it had been basking."
Amanda Bennett writes: “The Glen Miller Conservation Area runs along the shoreline of the Trent River between lock 2 (Sidney) and lock 3 (Glen Miller). This section of the Trent River was a focal point for my Master's research into the effects of locks and dams on Northern Map Turtle (Graptemys geographica) populations. For two springs and summers (2007 and 2008), Matt Keevil and I paddled and snorkeled around the Glen Miller Conservation Area in search of species-at-risk turtles. And we found them, more than we had imagined.
“In the two field seasons of capturing and marking turtles, we caught a total of 99 Northern Map Turtles between locks 2 and 3, including our only recapture for the section: an old female missing her two front legs affectionately known as “Stumpy”. Don't feel bad for her though, as it turns out she was still a faster swimmer than me, managing to escape in a moment of turtle madness before I could take her measurements for the recapture record.
“The lack of recaptures between our two field seasons seemed to be driven in part by the large population of Map Turtles in this section (calculated at 923 turtles, plus or minus 504: a lack of recaptures resulted in low precision) and by the fact that a lot of the turtles we were catching were juveniles, even hatchlings. As the river in this section has little in the way of shallow water habitats, it doesn't leave much space for baby turtles to hide, so a slow paddle and a keen eye can yield a surprising number of baby turtle sightings when launching from the Glen Miller Conservation Area.
“Interestingly, the small amount of shallow water habitat also appears to be limiting the growth of adult male Map Turtles, as we had a hard time catching any over 200 grams in weight upon which we could then attach radio-transmitters. This suggested to us that the high proportion of juveniles may be competing with the males for food resources in the shallower areas, whereas the females grow out of that limitation and feed instead on the nearly inexhaustible resource of Zebra Mussels found in the deeper waters.
“Radio-tracking female Map Turtles led us to the conclusions that the locks and dams were not blocking their passage along the Trent River, and that, indeed, turtles could lock through and move between sections as they pleased. Radio-tracking turtles between locks 1-2 also led us to the realization that some individuals were being swept into a holding tank at the water treatment facility from which there was no escape (except for a six-foot long handled dip net, which we left with the worker there so he could save any turtles he saw). In addition to that source of mortality, a couple of our radioed turtles disappeared and were last heard in the raging torrent at the dam intake. Talking with the folks who cleaned the intake grates led us to the conclusion that either yes, drowned turtles were frequently scraped off the grates, or no, no turtle had ever been trapped on the grate by the raging waters, depending on who you asked.
“Six Stinkpot turtles, including an adorable hatchling, were found in a small pond beside the rail bridge between locks 1-2, where Snapping Turtles, Painted Turtles, Bullfrogs, Banded Killifish, and a pair of Black-Crowned Night Herons also hung out (just to name a few of the creatures we encountered on our surveys).
“The Glen Miller Conservation Area was also a convenient place to launch our canoe from during our late fall and early spring tracking weekends, when we'd visit the river just before or after the ice came off to identify where our radioed turtles were hibernating. I say convenient because it turns out they hibernate in the deepest parts of the channel, more or less directly out into the middle of the river from the Conservation Area boat launch, right at the pipeline crossing, resulting in a thankfully short paddle in cold, cold canoe. It was in early spring too when we'd find Northern Leopard Frogs, Northern Watersnakes, and Eastern Gartersnakes emerging to bask on the rocky shoreline after their own long winters underwater or underground.
“Despite two years of intensive surveys, we barely scratched the surface of understanding the turtle populations between locks 2-3 of the Trent River. We don't even really know how many Map Turtles there are, given our lack of recaptures in the capture-mark-recapture population model. Additionally, Stinkpots inhabit the river both above and below this lock stretch, along with Painted and Snapping turtles (though with neither being listed as at-risk at the time, we didn't focus our efforts on these species). For what looks like a pretty boring section of rocky-bottomed river/canal, which boats only really visit to lock through, these parts of the Trent River turned out to be teeming with turtle life, precariously balanced at times with the dangers posed by a water treatment facility, dams, roads, and predators.
“Any failure of the pipeline through this area could significantly damage Map Turtle hibernation sites, not even considering the horrors a rupture would cause. This section of the river is only a lock away from the Bay of Quinte on Lake Ontario. I wouldn't even want to imagine the damage a rupture would cause to the Map, Stinkpot, Painted, and Snapping Turtle populations, let alone the fish, birds, mammals, invertebrates, plants, and people that call the waterway home.”