written by Susan Daniel, Erik Hartnett, Kit Hastings, and Brianne Tulumello
Although discomforting for scientists who like things to go as planned, these past two years were like an old friend that we didn’t know we needed to see. Due to the COVID-19 pandemic and subsequent shutdowns, we were unable to collect samples for the Great Lakes Biology Monitoring Program in 2020, resulting in a decrease in work for our staff. To remedy this unforeseen break between samples, EPA’s Great Lakes National Program Office (GLNPO) and the GLC worked closely together to create an alternative work plan that could benefit the benthic program. There were three main tasks detailed in the following sections. The work is ending now that sampling operations have restarted and we were able to collect new benthic samples in 2021.
In 1997, GLNPO added the collection of benthic macroinvertebrates to the Biology Monitoring program. Once these samples are collected and identified, organisms are preserved with ethanol or mounted on slides and stored for future use. The stored samples should be revisited every few years to refill preservative and inspect their condition. Missing the collection of the 2020 samples meant we had a rare opportunity to do a complete inventory and archive all samples. This was truly a team effort!
Erik Hartnett and Brianne Tulumello described the current state of each vial and microscope slide collected from 1997 to 2019, as well as all inhouse Cooperative Science and Monitoring Initiative (CSMI) archived samples (2012-2019). 18,538 vials and 17,122 slides from 1997 to 2019 were inventoried. Erik noted the 1997 vials were in overall poor condition, but out of the 870 vials inventoried for 1998 and 1999, the majority were preserved well. Brianne inventoried historic 1997-1999 slides, which was an involved and tedious process. To take an accurate inventory on the sites, counts, and condition of the slides, Brianne had to delicately separate some slides that were stuck together. Many of the 1997 slides were in poor condition, making the data hard to compare with records, while slides from later years were in much better condition.
Another unfortunate finding was that many sample slides we mounted in 2019 for CSMI Lake Erie had to be redone. To identify the many species of Oligochaeta and Chironomidae, specimens must be permanently mounted on microscope slides using a mounting media known as CMC. After a change in the formula of CMC from the manufacturer, it became apparent that most of the slides mounted for the 2019 sampling season had quickly begun to degrade. Over time, the exposed organisms would deteriorate and become unidentifiable if left unabated. This resulted in nearly 1,800 slides needing to be remounted to preserve the sample integrity for future use. Additional methods were developed to better understand the new CMC formula and to use different mounting media to reduce future slide failures, as well as reaching out to the manufacturer to find a formula to better meet our mounting needs.
When designing a new sampling procedure, there are bound to be some problems and lessons learned along the way; the early years of the GLNPO Biology Monitoring Program were no different. By statistically comparing data from the early years, we found that the 1997-1999 samples seemed to be identified somewhat differently than the subsequent years. To remedy this, we first verified that the records matched physical samples, and then identified major taxa to higher taxonomic resolution used in later years. In these early years, organisms were sometimes identified to genus instead of species, and we re-identified the same organisms to species level. Unfortunately, many organisms were missing or lost from samples collected in 1997, in contrast to samples collected in 1998 and 1999. This October, our laboratory submitted the corrections to GLNPO, and the data are currently in review. We are very grateful for the opportunity to reexamine these samples and data, which were preserved by GLNPO for over 20 years! This improvement will greatly increase our understanding of long-term trends observed in the Great Lakes.
Kit Hastings worked with Susan Daniel to create an image database for all Great Lakes species identified during the GLNPO Biology Monitoring Program. Kit focused first on the 59 oligochaete species found in our samples, writing up descriptions that highlight the distinguishing features of each species, other similar species that it could be confused with, and whether there is a genetic barcode reference from the Great Lakes in the BOLD database. So far, there are 21 Great Lakes oligochaete species profiled in the Great Lakes Benthic Invertebrate Reference Guide, along with pictures showing the distinguishing features that were taken by Susie during the Barcoding grant. As we move forward with our new 2021 samples, Kit and Susie will take pictures of relevant features to help add to the Reference Guide in the future, and eventually add other taxonomic groups like Chironomidae and Unionidae.
Photo gallery: GLC Alternative Work Plan 2021
Image caption: Erik Hartnett assessing the condition of archived vials.
