Beaver dam, Poland

Field activities within WAMBAF 2016

Water chemistry and Hg-content in biota samples have been monitored in beaver demo areas in Latvia, Sweden, Poland and Lithuania.

The purpose is work is to produce a "tailor made" data set for the testing and evaluation of the beaver dam tool, planned to be developed within WP3.3.The data will also be used to investigate the environmental effect of beaver dam removal.

Beaver demo areas

Suitable beaver demo areas had been identified by the participating project partners in the beginning of June 2016. The first water chemistry and biota samples were collected almost immediately after the final decision on which sites to be used had been made.

Water samples were collected in clean plastic containers and transported to the designated laboratories. Biota samples were collected with a macroinvertebrate net through "kick sampling" or by handpicking.

The beaver demo areas where sampled for Hg-content in biota in June, and a second time in September-October.

Water chemistry samples were collected at least at these two occasions and at some sites at tighter time intervals (e.g. in Lithuania, Latvia). At each beaver demo area at least one "upstream site" (upstream of "beaver activity", i.e. a reference site) and at least one "downstream site" (downstream of "beaver activity", ie. an affected site) has been sampled. Water chemistry- and biota samples have been collected on approximately the same spots, but not necessarily at the same times.

Collected animal groups

In the collection of biota samples for Hg-analysis some specific animal groups have been targeted. These can all be assorted into either of the two functional feeding groups (FFG´s) "grazers/scrapers" or "filter feeders" FFG is a way of grouping animals according to how and what they eat, reflected by various anatomical and physiological adaptations in the animals.

Examples of grazers/scrapers collected at one or several of the beaver demo areas sampled in 2016 include:

  • Freshwater snails (such as Lymnaea stagnalis, Potamopyrgus antipodarum, Viviparus contectus)
  • Certain species of may fly larvae (such as Baetis niger, Cloeon sp., Leptophlaebiidae sp.)

The filter feeders collected so far have been:

  • Small freshwater mussels (such as Pisidium sp., Spaerium sp.)
  • Black fly larvae (Simuliidae sp.)

Additionally, a few fish samples have also been collected, these all fall in the "predator" FFG category.

Sample preparation and analysis

The mollusk samples (snails and mussels) have been divided into two subsamples when possible, one sample containing only soft tissue and the other sample containing only shell. Prepared fish samples consist of muscle "filets" cut out from the collected fishes. These samples along with the samples containing insect larvae (whole animals) have been freeze dried at SLU and are ready to be analyzed for tot-Hg in the upcoming months.

More samples will be collected this year

In 2017 work will continue according to a somewhat extended sampling protocol. Biota samples will be collected in June and September-October like in 2016, one difference being that a removal of the beaver dam is scheduled for the summer 2017 at several demo areas. The autumn samples of 2017 will therefore constitute the first samples collected after this perturbation of the system.

The plan is also to collect sediment samples for Me-Hg and tot-Hg analysis in several beaver demo areas, samples will be collected from the bottom of the beaver reservoirs once before and once after dam removal.

Furthermore, samples for water Me-Hg and tot-Hg concentration will also be collected at the upstream and downstream sites. So we are looking forward towards an eventful and hopefully rewarding 2017 in the Beaver Hg team!

Joel Segersten, SLU, Sweden

  • Last Updated: 4/6/2017