Page 116 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 5. Early Holocene carbon storage and microbial activity in North Sea peats
Local vegetation succession in the southern North Sea
At the Max Gundelach site, wet terrestrial vegetation was present at the start of peat accumulation 11,760 years BP, with the presence of Carex spp. (Fig. 4A). A certain degree of open water was present, as remains of invertebrates (Chironomid head capsules, Cladocera) together with Characeae oospores were found. These green algae are characteristic of lake waters in pioneer conditions with inputs of minerogenic material (Mauquoy and Van Geel 2007) and therefore indicative of eutrophic conditions. At 180 cm beneath the seabed, Cladocera resting eggs were found, suggesting harsher conditions for these invertebrates. All other open-water taxa disappeared.
From a depth of 170 cm onward, the environment became nutrient poor, as evidenced by the dominance of Sphagnum magellanicum. S. magellanicum is an important contributor to ombrotrophic peat bogs with a constant water table (Siebel and During 2006). Remains of woody plants, in the form of leaf scars, and charcoal were also present at this depth. This indicates the presence of vascular plants during peatland growth.
S. magellanicum declined and the brown moss Tomentypnum nitens, a species no longer existing in the Netherlands, became the main peat building component at 160 cm depth. T. nitens is an indicator species of mineral-rich fens, highlighting a change from nutrient-poor to nutrient-rich conditions. The presence of T. nitens indicates that calcium and nutrient-rich groundwater were seeping into the terrestrial environment (Bohncke, Van Haaster and Wiegers 1984; Hedenäs and Kooijman 1996; van Geel et al. 2020). From 150 cm depth onward, T. nitens was replaced by Warnstorfia sarmentosa and Drepanocladus sp. Both species are brown mosses, further indicating a transition to wet mesotrophic conditions. Carex sp. (sedges) rootlets were found in the top of the peat sequence.
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