‘Blue Carbon’ and Nutrient Stocks of Salt Marshes at a Temperate Coastal Lagoon (Ria de Aveiro, Portugal)

Abstract

Ria de Aveiro is a mesotidal coastal lagoon with one of the largest continuous salt marshes in Europe. The objective of this work was to assess C, N and P stocks of Spartina maritima (low marsh pioneer halophyte) and Juncus maritimus (representative of mid-high marsh halophytes) combined with the contribution of Halimione portulacoides, Sarcocornia perennis, and Bolbochenous maritimus to the lagoon ≈4400 ha marsh area. A multivariate analysis (PCO), taking into account environmental variables and the annual biomass and nutrient dynamics, showed that there are no clear seasonal or spatial differences within low or mid-high marshes, but clearly separates J. maritimus and S. maritima marshes. Calculations of C, N and P stocks in the biomass of the five most representative halophytes plus the respective rhizosediment (25 cm depth), and taking into account their relative coverage, represents 252053 Mg C, 38100 Mg N and 7563 Mg P. Over 90% of the stocks are found within mid-high marshes. This work shows the importance of this lagoon’s salt marshes on climate and nutrients regulation, and defines the current condition concerning the ‘blue carbon’ and nutrient stocks, as a basis for prospective future scenarios of salt marsh degradation or loss, namely under SLR context.

Climate Change Impacts on Salt Marsh Blue Carbon, Nitrogen and Phosphorous Stocks and Ecosystem Services

“…Moreover, nonwoody succulent and grass-type plants such as S. perennis and S. maritima have higher carbon storage capacities and thus its coverage influence greatly the overall blue stock value (Figure 5). The values obtained here are higher but comparable to previous work where not all the different carbon storage capacities of the different species are considered [24]. On average, using a per-acre value of carbon disregarding the species composition and different carbon storage abilities induces about 10% overestimation on the blue carbon, nitrogen, and phosphorous stocks (data not shown), which can be translated into several tons per year.…”

“…Nevertheless, the majority of studies have focused on an areabased salt marsh valuation, disregarding the different services provided by different floristic inventories [9]. One of the most investigated ecosystem services provided by salt marshes is its carbon sequestration ability, commonly referred to as blue carbon sequestration [23][24][25][26].…”

“…Comparable to what happens with nutrient (nitrogen and phosphorous) sequestration, blue carbon storage is also highly dependent on the plant coverage, highlighting the need to evaluate the stock services of the ecosystem with species-specific values instead of average community values [24,27,28].…”

High variability of Blue Carbon storage in seagrass meadows at the estuary scale

“…Variation also exists among and within estuaries, in terms of turbidity and water flow, which may determine seagrass meadows' habitat extent or landscape configuration 30,31 and also species composition and structural traits, such as shoot density and cover 32 . Other coastal vegetated habitats, such as mangroves and saltmarshes can be present in estuaries also contributing to C org stocks 33,34 and to seagrass sedimentary C org stocks 35 . Variation is also reflected in sedimentation rates, which can be influenced by seagrass canopies trapping particulate organic materials, thus decreasing turbidity and increasing sedimentary C org stocks 36 .…”

Mitigating Negative Unintended Impacts on Biodiversity in the Natura 2000 Vouga Estuary (Ria de Aveiro, Portugal)

“…(1) Protection of existing populations from fragmentation and increase resilience by enhancing sediment stability through application of coconuts fibber mats (e.g., Sousa et al 2017a) (2) Transplantation of Z. noltei plots from selected donor sites within Ria de Aveiro (e.g., Suykerbuyk et al 2016) (1) Restoration of salt-marsh communities (Sousa et al, 2017b), namely Juncus maritimus, through revegetation of sheltered mudflats, considering submersion time. (2) Foster saltmarshes elevation through accretion.…”