Vernal Pool Spring 2012
This year’s visit to this amphibian breeding pond helped consolidate the presence of several invertebrate species, as well as, serve as an indication of the variability of the number and kind of species making use of the spring conditions of this vernal pool.
Pond characteristics and surrounding vegetation
Figure 1. Vernal pool dimensions
The longest axis of the vernal pool has a west-east alignment measuring 28m. it is pear-shaped with a maximum width of 15m to the west and 12.7m to the east; and about 12m in its shortest width (see Figure 1, north upwards ). Water depth at maximum fill reaches about 60 to 80cm deep about 1 to 1.5m off its southern edge (see Figure 2, image rotated counter-clock wise). On may 11, depths measured were only around the 60cm to 40cm. The muck and leaf detritus layer is in the range of 25cm on the western edge to 17cm on the eastern edge. The underlying mineral soil layer below the muck is made of a heavy glay clay (Glay1 8/N) containing only a very small proportion of sand and gravel and less than 1% clay mottles. Also shown in Figure 2. is the few location of submerged grass.
Figure 2. Sketch of contour of the pool along the cut in the picture including measurements of water and muck depth to clay layer. Notice in the picture the location of submerged vegetation in the pool.
Figure 3 (north is up). maps the location and characteristics of trees, shrubs and forbs within 5m of the vernal pool. Of significance is the presence of two elms(probably Rock Elms Ulmus thomasii) with bdh of 40 to 50cm and 16 to 20m high. Elms this tall are very unusual. A cluster of young Rock elms – with bdh in the range of 10 to 15 cm, are growing in the proximity of these two older elms. Why these group of elms has remained unaffected by Dutch-elm disease is unclear, when just less than 100 meters to the west, clusters of dead elms attest to the effect of the elm disease. Notice the encroachment by ash and maple on the south-eastern bank of the pool.
Figure 3. North is up. Identification of major mature trees visible on the aerial picture and views of marked locations. The vernal pool is essentially framed by three distinct tree populations: Poplars to the northeast and east, Elms to the north-west and west and Silver Maple, White Ash and Sugar Maple mix to the south, The invasive Buckthorn (Rhamnus cathartica) to the north and Barberry (Berberis spp.) o the south are the main shrubs at the banks of the pool.
Account of species detected on April 21 2013 (visual survey)
Amphibian tadpoles: fewer overwintering Green frog tadpoles (~100mml; Lithobates clamitans) were observed this spring compared to last year.
Overwintering green frog (Lithobates clamitans) tadpoles
This year, at least two, if not three species of amphibians laid eggs in this pool.
One of the egg masses groups among the submerged plant clusters located on the northern edge of the pool.
Most abundant eggs masses were from, what seems to be, Wood frogs (Lithobates sylvatica).
Characteristic Yellow-spotted salamander egg masses (Ambystoma maculatum, white eggs in the early stages – acquiring symbiotic bacteria later in their development) were also laid close by or mixed with the frog egg masses. [Top picture taken on April 21st, bottom picture taken in May 7. Notice in the bottom image the snail on the lower edge to the right of center (possibly Radix auriculata)].
Small isolated egg mass with only a few large eggs without gelly capsule were also noticed. These egg masses were laid in more shaded areas and apart from all others. They could be blue-spotted salamander eggs (Ambystoma laterale).
Small cluster of large eggs. Possibly from Blue-spotted salamander
- Like last year, Central Newts (Notophtalmus viridescens lousianensis) were also noticed in the pool.
Central Newt (Notophtalmus viridescens louisianensis)
- A predaceous diving beetle (Dysticus spp.) drawn to a cluster of gray velvet springtails of the Poduridae family.
Notice the springtails on the lower right of the image.
- Only one occurrence of a large aquatic snail (?Radix auriculata) was noticed this year – compared to their relative abundance last year (see the Yellow-spotted salamander image above). Relatively large (about 10 to 20mm in diameter) snail egg sacs were found at the east end of the vernal pool. Last year’s egg sacs were smaller but were more frequently found.
About 1 to 1.3 cm on diameter snail egg sacks.
Account of species detected between May 7 and May 11 2013.
- One adult Green frog (Lithobates clamitans melanotus) seen on May 7.
Green frog (Lithobates clamitans malanotus)
- On May 11, a benthos sampling was performed. On surveying the location before and after benthic sampling, the following species were seen in the floating and submerged water layers:
Central Newt larva (see image below) and Central Newt adult (Notophtalmus viridescens louisianensis)
Swimming among the overwintering Green frog tadpoles was a number of smaller dark blackish tadpoles (~40mm; possibly wood frog tadpoles).
A variety of aquatic snails were found foraging on submerged and floating tree trunks and branches. Two kinds were seen: medium size (~1cm long) with pointed conical shells (Stagnicola spp.?), and flat coiled with ridges only a few millimeters in diameter. Also noticed was a large number of small gelly spherules on the mosses (?eggs).
snail activity on the underside of floating or submerged wood
Dobsonfly larva, Hellgrammite (~25 to 30mm) on underside of a submerged branch (Corydalus spp.). An indicator of relatively pure and undisturbed conditions.
Benthos Sampling results: Will be reported in an upcoming blog entry
Account of species absent in the 2013 survey compared to the 2012 spring survey.
- This spring there was no indications of the following species:
Leopard Frogs(Lithobates pipiens)
Midland Painted Turtles (Chrysemis picta marginata)
Water conditions for this spring
|DATE||TEMP ('C)||BANK SOIL TEMP ('C)||pH||CONDUCTIVITY (uS/cm)||ORP (mV)||Alkalinity (ppm)||Phosphate (ppm)||Nitrate (ppm)||Hardness (ppm)||Turbidity (FTU)|
|21 April 2013||8||5||7.3||245||182||110||>4||nd||250||84.7|
|11 May 2013||14||8.1||340||175||<1||nd||5.92?|