Start of Pond Surveying Season

In previous years I have monitored a few ponds in my local nature reserves. This year, I have been more ambitious and have extended both the number of sites to be covered and the scope of the surveys. As I am also wanting to gain experience and work towards my Great Crested Newt licence, I put a request out via my local ARG group to see if anyone would like to help me and have had an overwhelming response, with more than fifteen people coming forward. This means that I will always have someone with me when I go out surveying, which not only makes it more enjoyable but is also safer and I can do more night visits with confidence. The people helping me have a range of experience - some already hold a licence and others are wanting to learn more, so it's great that we can all support each other.

I have arranged to survey all three sites on alternate weeks.  This week was the first visit and was carried out during the day. The aim was to reconnoitre the site and gather environmental data, as well as doing a visual search of the ponds for signs of amphibians but mostly for frog spawn.

The environmental data provides an impression of the health of the pond, but also enables a Habitat Suitability Index to be generated. This provides a score that evaluates the suitability of the pond for Great Crested Newts based on ten factors. Being able to assess this is a requirement of the CIEEM competencies and the GCN licence, so I am trying to get as much experience as possible.  I have also been compiling the results into a summary document for each site to gain experience of producing ecological reports.

Our first visit was on Saturday to Letchmire Pastures. It took slightly longer than I envisaged to carry out the survey, but once I re-familiarise myself with the paperwork I am sure this will become easier. We found some frog spawn and stickleback in one pond, but not much else of interest.

On Tuesday, we surveyed Ledston Luck nature reserve. This was a much more interesting visit. Whilst looking for frog spawn, I stumbled across a feeding pile and latrine and confirmed water vole presence on the site. This was really exciting and totally unexpected and it made my day. We also saw signs of other mammals including fox, deer and field vole. There are two really nice ponds on site, two that are not so good as they are in very wooded areas, and some scrapes on the plateau that are unlikely to support amphibians.

On Thursday, we visited the largest site at Rothwell Country Park. I am more familiar with this site, as it's the one I have surveyed the most of the years. Although we did find frog spawn, there were no signs of newts although the water was very turbid in most of the ponds. I am not sure what is causing this as there has not been much rain recently.

On all of the surveys, we did a brief invertebrate sweep to assess the water quality. I do enjoy this part of the survey, and I would like to be able to identify more of the species, though I am getting more familiar with them already.

The most time-consuming part of the week has been compiling the results. I am transposing these onto my own spreadsheet, but they also have to be keyed onto the PondNet website.  I ultimately want to produce a report for each site, but am still experimenting with this and am researching what I should include and how this is best presented.

On Friday, I carried out an extra survey and went to Skelton Grange Environment Centre. As these are not part of my PondNet project, I carried out a shorter survey and just compiled the HSI scores for the ponds. This has given me good practice at writing up the results and thinking about their implications.

Tadpoles Developing

The last few weeks have been rather busy and a little bit stressful.  Several days elapsed until additional spawn was laid, and whilst I was waiting I was starting to panic that I wouldn't be able to complete my experiment. Since then, I have had over a dozen clumps of spawn. It has been a little difficult to catch this quickly once it has been laid, as the frogs tend to lay new spawn on top of existing spawn so that it forms a mat. I actually now have four replicates of the experiment running: all of the first batch (Replicate A) seems to have spoiled so I took a further batch (Replicate D) to ensure I had three sets of results to compare.

Another stressful moment was when my pH meter failed: I discovered that water had got into the battery compartment and fried the electrics. I ordered another on overnight delivery, and although it was much more expensive it seems a lot slower and only produces readings to 0.1 decimal place. I have taken to checking it against the calibration fluid before I start checking my water treatments as I am not overly confident in the new meter so am erring on the side of caution.

Now that I am over a week into the experiment and have three replicates running I am starting to get some good results. It was impossible to identify the early stages of development without a microscope, but once the embryo started to develop a tail bud I could allocate it to the appropriate Gosner stage.  Development seems to be progressing very quickly, with just a day or two between the tail bud first developing and the gills forming. The embryos are now moving, mostly curling and uncurling, within the central egg sack. The next stage to look for is a heart beat behind the gills, but I am not sure I would be able to see this without a microscope.

Although none of the embryos have hatched yet, there are some obvious developments. The least acidic treatment, at 5.5 pH, seems unaffected and is developing in line with my control group which is in neutral pond water.  The tadpoles in moderately acidic water of 4.5 pH seem to be about a day behind in development terms, and there are slightly more deformities/undeveloped eggs.

The most acidic treatment, at 3.5 pH, is much different - none of the eggs are developing. The inner sack has turned opaque and the eggs generally are cloudier and more condensed. In some of them, the nucleus seems to have broken apart. I am continuing to monitor them, but doubt any will hatch.

I have taken lots of photos and notes to remind me of each development stage, and this should make it easier when I come to write the discussion section of my dissertation.

Tadpole Experiments

As I'm close to completing my degree, in February I started my dissertation project, a 30-credit final year module on environmental science. I get to choose my own project, as long as it compares biotic and abiotic factors. I have chosen to study common frog tadpole hatching success at different levels of water acidity. This follows on from my second year project where I did some fieldwork in a local nature reserve, and found that amphibians were absent from one particularly acidic pond. After some literature research, I have set up a home experiments to assess at what point acidity is lethal, and at which point it can develop into frog spawn. Is there a tipping points or a gradient along which acid impacts development?  The last few weeks have been quite intense in planning and setting up the experiment.  I had to get approval from the module team early, as the deadline for my first assignment isn't for another ten days, but the frogs arrived in my pond in mid-February.  I am at a slight disadvantage as I am having to cram a lot of work up front, but it will mean that my data collection is over relatively quickly and I have the summer to write up and get involved in other conservation tasks.

Yesterday, activity in the pond increased and the first clump of spawn was laid. This happened at lunchtime, just as I was about to set off for an overnight trip. As I had committed to collect spawn within 24 hours of it being laid, needless to say my trip was delayed while I collected the spawn and decanted it into separate tanks.

First I split the clump of frog spawn into four different batches.  This was much harder than I imagined as the jelly stuck the eggs together very firmly. Three smaller clumps were put into my least acidic water to acclimitise, then two of the clumps were gradually moved to more acidic water.  One of the four clumps was returned to the pond.

The experiment has only been running a day and so it's not really possible to see if there is a difference between the spawn in the different water treatments.  The one in the most acidic water does look slightly more cloudy, but this could be my imagination. There are a couple of deformed eggs, but these occur in different treatments so it is not necessarily the acid that has caused it - it could have been damaged whilst I was splitting the spawn.

Hopefully the frogs will produce more spawn in the coming days as I need to carry out at least three replicates of the experiment. I am trying to photograph the spawn at different stages so hopefully there will be some interesting photos posted here over the coming weeks.