Does Regional Development Influence Sedimentary Blue Carbon Stocks? A Case Study From Three Australian Estuaries

Mitigating climate change through the reduction of atmospheric CO2 levels is of interest,<br>particularly through maintaining and re-establishing natural ecosystems that act as<br>carbon sinks, such as coastal vegetated habitats or “blue carbon” systems. Here<br>we compare sedimentary blue carbon (C) stocks from 37 sediment cores collected<br>in pristine (n = 13), agricultural (n = 11), and urban (n = 13) estuaries within the<br>same geomorphological region, located on the eastern coast of Australia. The mean<br>estimated C stocks for each carbon system (seagrass, mangrove, and saltmarshes)<br>were 402 78, 830 109, and 723 100 Mg C ha􀀀1, respectively, conservatively<br>estimated up to 3 m depths. Analysis of variance revealed no significant difference<br>between C stocks per area (C ha􀀀1) considering each habitat type and between specific<br>estuaries. However, the total estuarine C stocks were found to be greater with increasing<br>levels of conservation, based on larger areas of blue carbon vegetation. The potential<br>loss of C to the atmosphere from these small regional estuaries are 500,574 118,635<br>tons of CO2 equivalent (CO2e), based on specific assumptions. The implication of these<br>results are that there are large C stocks in small regional estuaries which supports the<br>protection of blue C systems in developing coastal areas and highlights the uncertainties<br>of the CO2 emissions from potential blue C habitat degradation.