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Research Project
Ecological production functions to evaluate ecosystem services delivered by seagrass beds ECOFUNGRASS
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Publications
Long-term effects of elevated CO2 on the population dynamics of the seagrass Cymodocea nodosa: Evidence from volcanic seeps
Publication . Mishra, A. K.; Cabaço, S.; de los Santos, Carmen B.; Apostolaki, E.T.; Vizzini, S.; Santos, R.
Population reconstruction techniques was used to assess for the first time the population dynamics of a seagrass,
Cymodocea nodosa, exposed to long-term elevated CO2 near three volcanic seeps and compared them with
reference sites away from the seeps. Under high CO2, the density of shoots and of individuals (apical shoots), and
the vertical and horizontal elongation and production rates, were higher than at the reference sites. Nitrogen
limitation effects on rhizome elongation and production rates and on biomass were more evident than CO2 as
these were highest at the location where the limitation of nitrogen was highest. At the seep where the availability
of CO2 was highest and nitrogen lowest, density of shoots and individuals were highest, probably due to CO2
effects on shoot differentiation and induced reproductive output, respectively. At the three seeps, there was
higher short- and long-term shoot recruitment than at the reference sites, and growth rates was around zero,
indicating that elevated CO2 increases the turnover of C. nodosa shoots.
Recent trend reversal for declining European seagrass meadows
Publication . de los Santos, Carmen B.; Krause-Jensen, Dorte; Alcoverro, Teresa; Marbà, Nuria; Duarte, Carlos M.; Van Katwijk, Marieke; Pérez, Marta; Romero, Javier; Sánchez Lizaso, José Luis; Roca, Guillem; Jankowska, Emilia; Perez-Llorens, Jose Lucas; Fournier, Jérôme; Montefalcone, Monica; Pergent, Gérard; Ruiz, Juan M.; Cabaço, Susana; Cook, Kevan; Wilkes, Robert J.; Moy, Frithjof E.; Trayter, Gregori Muñoz-Ramos; Arañó, Xavier Seglar; Jong, Dick J. de; Fernández-Torquemada, Yolanda; Auby, Isabelle; Vergara, Juan J.; Santos, Rui
Seagrass meadows, key ecosystems supporting fisheries, carbon sequestration and coastal protection, are globally threatened. In Europe, loss and recovery of seagrasses are reported, but the changes in extent and density at the continental scale remain unclear. Here we collate assessments of changes from 1869 to 2016 and show that 1/3 of European seagrass area was lost due to disease, deteriorated water quality, and coastal development, with losses peaking in the 1970s and 1980s. Since then, loss rates slowed down for most of the species and fast-growing species recovered in some locations, making the net rate of change in seagrass area experience a reversal in the 2000s, while density metrics improved or remained stable in most sites. Our results demonstrate that decline is not the generalised state among seagrasses nowadays in Europe, in contrast with global assessments, and that deceleration and reversal of declining trends is possible, expectingly bringing back the services they provide.
Snapshot of macroalgae and fish assemblages in temperate reefs in the Southern European Atlantic Ecoregion
Publication . Franco, João N.; Arenas, Francisco; Sousa-Pinto, Isabel; de los Santos, Carmen B.
Most of the biodiversity studies in the South European Atlantic Shelf ecoregion are limited to shallow subtidal or intertidal habitats, while deeper reef habitats, also of relevant ecological importance, are particularly understudied. Macroalgal communities, associated fauna, and sea surface temperature were studied in deep reefs (25-30 m) at two locations in this ecoregion: Parcel, North of Portugal (41 degrees N), and Tarifa, Southern Spain (35 degrees N). Specifically, algal assemblages were assessed using biomass collection and associated ichthyofauna was assessed using visual census techniques using scuba. Seawater surface temperature was higher (>3 degrees C) in the southern region-Tarifa, compared to the northern region-Parcel. Our survey revealed 18 fish species and 23 algae species. The highest abundance of cold-water species (both macroalgae and fish species) was recorded in Parcel and warm-water species were dominant in Tarifa. In light of climate global trends, both regions might experience biodiversity shifts towards tropicalization. Current knowledge on their biodiversity is imperative to further evaluate potential shifts.
Carbon and nitrogen stocks and burial rates in intertidal vegetated habitats of a Mesotidal coastal lagoon
Publication . Martins, Márcio; de los Santos, Carmen B.; Masqué, Pere; Carrasco, A. Rita; C. Veiga-Pires, C.; Santos, Rui
Coastal vegetated ecosystems such as saltmarshes
and seagrasses are important sinks of organic carbon (OC) and total nitrogen (TN), with large global
and local variability, driven by the confluence of
many physical and ecological factors. Here we
show that sedimentary OC and TN stocks of intertidal saltmarsh (Sporobolus maritimus) and seagrass
(Zostera noltei) habitats increased between two- and
fourfold along a decreasing flow velocity gradient
in Ria Formosa lagoon (south Portugal). A similar
twofold increase was also observed for OC and TN
burial rates of S. maritimus and of almost one order
of magnitude for Z. noltei. Stable isotope mixing models identify allochthonous particulate organic
matter as the main source to the sedimentary pools
in both habitats (39–68%). This is the second estimate of OC stocks and the first of OC burial rates in
Z. noltei, a small, fast-growing species that is widely
distributed in Europe (41,000 ha) and which area is
presently expanding (8600 ha in 2000s). Its wide
range of OC stocks (29–99 Mg ha-1
) and burial
rates (15–122 g m2 y-1
) observed in Ria Formosa
highlight the importance of investigating the drivers of such variability to develop global blue carbon models. The TN stocks (7–11 Mg ha-1
) and
burial rates (2–4 g m-2 y-1
) of Z. noltei were generally higher than seagrasses elsewhere. The OC
and TN stocks (29–101 and 3–11 Mg ha-1
, respectively) and burial rates (19–39 and 3–5 g m-2 y-1
)
in S. maritimus saltmarshes are generally lower than
those located in estuaries subjected to larger accumulation of terrestrial organic matter.
Vertical intertidal variation of organic matter stocks and patterns of sediment deposition in a mesotidal coastal wetland
Publication . de los Santos, Carmen B.; Lahuna, François; Silva, André; Freitas, Cátia; Martins, Márcio; Carrasco, A. Rita; Santos, Rui
Tidal coastal wetlands, common home to seagrass and salt marshes, are relevant carbon sinks due to their high capacity to accumulate and store organic carbon in their sediments. Recent studies demonstrated that the spatial variability of this organic carbon within the same wetland system can be significant. Some of the environmental drivers of this spatial variability remain understudied and the selection of the most relevant ones can be context dependent. Here we investigated the role of bed elevation, hydrodynamics, and habitat type (salt marsh and seagrass) on the organic matter (OM) net deposition-resuspension rate and superficial sedimentary stocks (top 5 cm) at the tidal wetlands of the Ria Formosa, a mesotidal coastal lagoon in South Portugal. Results showed that two vectors of spatial variation need to be considered to describe the intertidal sedimentary OM stocks: the bed elevation that imposes a decrease of the hydroperiod and thus the change of habitat from the lower seagrass Z. noltei to the upper saltmarsh S. maritimus, and the horizontal spatial variation along the secondary channels of the lagoon that imposes a decrease in the current flow velocity magnitude. The multiple linear regression analyses, using data from 40 sampling points, explained 59% of the variation of the superficial sedimentary stocks of OM in salt marshes and seagrasses of the Ria Formosa lagoon and revealed that stocks generally decrease with elevation, yet with variation among sites and habitats. It was also found that the decrease of the OM net deposition-resuspension rate with bed elevation was exponential. Our study emphasizes the importance of considering multiple environmental drivers and spatial variation for regional estimations of organic matter (and organic carbon) sedimentary stocks in coastal wetlands.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
OE
Funding Award Number
SFRH/BPD/119344/2016