To follow the process of colonization and succession of life on and in wood and to study the process of wood degradation we deployed our custom-designed BiOlogical Recruitment Grids (BORGs) in summer 2019. Our current FWF project “Environmental impact on giant ciliate mutualism” (2019-2023) is funding this project. Thanks for all the help to Tihomir Makovec, Miljan Sisko and Matej Marinac from the Marine Biology Station of Piran.

The three sites we chose were 1) the canal Lera of the Secovlje Salina Nature Park, 2) the shallow subtidal mudflat of the Strunjan Landscape Park, and 3) the area in front of the Marine Biology Station in Piran.

Wooden and plastic cubes are mounted on each BORG to collect a set each summer and winter for several years. The blocks are in fact plates put together so that the inside of the wood can also be sampled.

BORG at Lera 1. at deployment in summer 2019. Photograph: Tihomir Makovec. 2. BORG winter 2020 and 3. BORG in winter 2022. Photographs: Teresa Winter

BORG 1. at the Institute in winter 2020. Photograph: Tihomir Makovec. 2. and 3. BORG summer 2022. Photographs: Teresa Winter.

BORG 1. and 2. In Strunjan in winter 2020. Photographs: Renate Degen. 3. and 4. BORG summer 2022. Photographs: Teresa Winter

For the past three years between 2020 and 2022 we conduced field work to recover every summer and every winter 3 wooden and a control plastic block at each of the three sites in addition to measurements of abiotic conditions in the blocks and the surrounding seawater. We took samples of the surface of the wood, the surrounding water and the surrounding sediment for sequencing the community of bacteria, archaea, fungi, and eukaryotes. These samples are in progress now.

We are almost finished with the identification of animals growing on and in the wood. We found a total of more than 300 taxa, most of them identified to species level. Most of the animals were identified by Renate Degen and Sebastián Valerio. We are grateful to Borut Mavric, Thomas Schwaha and Jan Steger for their help with the identification of some animals.

Wood degrading animals, next to microbes, facilitated the fast degradation of our wood blocks. We identified by morphological and molecular gene markers the shipworms species Teredo navalis, Nototeredo norvagica and Lyrodes mersinensis. The animals live in symbiosis with xylotrophic and nitrogen fixing bacteria in their gills. These bacteria provide wood degrading enzymes to the host so that they can digest the wood. The gribbles, isopods of the genus Limnoria as well as the amphipod Chelura cerebrans also eat wood but without the help of bacterial symbionts.

Shipworm left (Photograph: Charles Roque Figueiredo) and gribble right (Micrograph: Monika Bright)

Many other animals were found to live on the wood or in the empty burrows inside of the wood. Here a collection of some of animals. Micrographs taken by Monika Bright.

Anthozoan and hydrozoans

Asteroidea (starfish) and Ophiuridea (brittle star)


Bivalves and an egg of Cephalopod


More Gastropods



Plathyhelminthes and Nemertea


More polychaetes