Seaweed biomass along the depth gradient in 2021:
In 2021, a total of 21 biomass dominant macroalgal taxa (11 Phaeophyceae, 6 Rhodophyta, 4 Chlorophyta) were collected along the depth transect. In contrast to the previous studies, six macroalgal taxa were not biomass relevant anymore as they were either absent (Phaeophyceae: Chorda filum , Haplospora globosa ,Laminaria solidungula ; Rhodophyta: Cystoclonium purpureum ,Odonthalia dentata ) or were only encountered in negligible amounts of <0.1g FW (Phaeophyceae: Battersia arctica ). Detailed FW and DW data of single species and sums of groups in 2021 are given in Appendix 3 and Appendix 4, respectively.
In the infralittoral zone (0m) the macroalgal community was most diverse with 15 taxa present and understory seaweed FW (2.2 kg FW m-²), ‘Other Phaeophyceae’ (1.2 kg FW m-²) as well as Rhodophyta (0.9 kg FW m-²) exhibited their maximum biomass. In contrast, the biomass peak of overall seaweed FW (11.5 kg FW m) and kelp FW (11.3 kg FW m) was at 2.5m. At 5 and 10m the kelp species A. esculenta (3.6 and 0.9 kg FW m, respectively) showed the highest biomass of all seaweeds. Because of the high A. esculenta FW, kelps were responsible for 95 and 56% of the overall seaweed FW at 5 and 10m, respectively. At 15 m the ground was almost exclusively covered with Rhodophyta (0.335 kg FW m) and dominated byPhycodrys rubens (0.317 kg FW m), whileA. esculenta (0.0009 kg FW m) was near to its lower distribution limit.