Biology subjects

Hancke, K.

Publications and source records attributed to Hancke, K..

3 recordsLinked to original sources

bioRxiv2025

Combining environmental DNA and traditional sampling to assess the role of kelp aquaculture as an artificial habitat in Norway

Kelp aquaculture is expanding rapidly in the temperate Atlantic, yet its ecological role as an artificial habitat remains poorly understood. This study assessed the biodiversity associated with wave-exposed kelp farms in coastal Norway using both environmental DNA (eDNA) and traditional sampling methods. Fish and invertebrate communities were surveyed at two kelp farms and compared to nearby natural kelp forests and pelagic control sites. Results from gill-net fishing, camera observations, and invertebrate sampling revealed lower species richness and abundance at kelp farms compared to natural habitats. eDNA analyses (12S and CO1 markers) showed few differences in community composition between sites, and no species were identified as indicators of kelp farms. Traditional sampling detected the presence of the amphipod Caprella mutica in the kelp farms, indicating that operators can play roles in alien species spread. Overall, kelp farms supported distinct but less diverse communities than natural kelp forests, being more similar to pelagic control sites. Finally, eDNA provided limited insights compared to traditional methods. These findings suggest that kelp farms currently provide limited habitat provisioning in Norway, likely as a result of how and where kelp aquaculture is currently performed. We suggest the need for population-level assessments for relevant species like Atlantic lumpfish (Cyclopterus lumpus) and locally based assessments in collaboration with authorities to define nature-positive or negative outcomes to balance ecological and economic goals in the growing seaweed aquaculture industries of the Atlantic.

ecology↗

bioRxiv2025

High-resolution three-dimensional mapping of eelgrass (Zostera marina) habitat and blue carbon using drone-borne LiDAR

The accessibility of flying drones (Unoccupied Aerial Vehicles) presents scientists and managers with reproducible and cost-effective methods to monitor submerged aquatic vegetation. In particular, drone-borne topobathymetric LiDAR provides high-resolution (cm-scale), three-dimensional information about the geometry and structure of surveyed areas, allowing for quantification of vegetation volume in addition to bathymetry. For habitat-forming submerged and intertidal vegetation like seagrass, this information can advance research regarding the structure and patchiness of canopies in relation to biodiversity, blue carbon storage, and hydrodynamic processes. Here, we report how drone-borne LiDAR can be used to estimate the habitat volume of eelgrass (Zostera marina) within a sheltered bay in south-eastern Norway. After classifying LiDAR points using a Random Forest model, we created a Digital Terrain Model of the sea floor and a Digital Surface Model of the eelgrass canopy. From these models, we estimated eelgrass canopy volume to range between 862 and 1099 m3 across the small study area. From the volume, we estimated above-ground carbon storage in living eelgrass tissue to range between 96 and 122 kg. To our knowledge, this is the first study to utilise drone-borne LiDAR to quantify the volume and carbon-storage potential of a marine habitat-forming species like eelgrass, thereby demonstrating the potential of drone-borne LiDAR as an efficient tool to provide reproducible and high-resolution data for submerged aquatic habitats, including seagrass meadows.

ecology↗

bioRxiv2023

The possible copepod link between kelp forests, the pelagic ecosystem and deep-sea carbon sequestration

Kelp forests are dynamic coastal habitats that generate large amounts of carbon-rich detritus. The fate of this detritus is largely unknown and considered a missing link in global carbon budgets. Kelp detritus can serve as food for benthic invertebrates and pelagic invertebrate larvae, but we know close to nothing about the role of kelp detritus as food source for other zooplankton. Lipid-rich pelagic copepods constitute a key link from primary producers to higher trophic levels in marine boreal and arctic ecosystems, and they transport vast amounts of carbon into the deep sea. We conducted feeding experiments to test if the copepod Calanus finmarchicus can feed on fragments of two dominant kelp species, Saccharina latissima and Laminaria hyperborea. Such feeding would constitute an undescribed pathway from blue forests to pelagic consumers and deep-sea carbon sequestration. The experiment indicated that C. finmarchicus can ingest kelp particles, but the digestion is limited compared to a regular phytoplankton diet. Moreover, the results provide initial evidence that L. hyperborea contains substances that are toxic to copepods, an observation that warrants further research. Using specific qPCR assays to trace the consumption of kelp, we found that kelp DNA amplification signals were stronger for copepods fed with S. latissima than L. hyperborea, but we were not able to conclusively separate consumed kelp from DNA attached to the outside of the copepods.

ecology↗