75 research outputs found
Short-term growth and biomechanical responses of the temperate seagrass Cymodocea nodosa to CO2 enrichment
Seagrasses are often regarded as climate change 'winners' because they exhibit higher rates of photosynthesis, carbon fixation and growth when exposed to increasing levels of ocean acidification. However, questions remain whether such growth enhancement compromises the biomechanical properties of the plants, altering their vulnerability to structural damage and leaf loss. Here, we investigated the short-term (6 wk) effects of decreasing pH by CO2 enrichment on the growth, morphology and leaf-breaking force of the temperate seagrass Cymodocea nodosa. We found that the plant biomass balance under levels of acidification representative of short-term climate change projections (pH 8.04) was positive and led to an increase in leaf abundance in the shoots. However, we also found that plant biomass balance was negative under levels of acidification experienced presently (pH 8.29) and those projected over the long-term (pH 7.82). Leaf morphology (mean leaf length, thickness and width) was invariant across our imposed acidification gradient, although leaves were slightly stronger under [CO2] representative of short-term climate change. Taken together, these findings indicate that a subtle increase in growth and mechanical resistance of C. nodosa is likely to occur following short-to medium-term changes in ocean chemistry, but that these positive effects are unlikely to be maintained over the longer term. Our study emphasises the need to account for the interdependencies between environmental conditions and variations in multiple aspects of the structure and functioning of seagrass communities when considering the likely consequences of climate change.Mobility Fellowships Programme of the EuroMarine Consortium (European Commission Seventh Framework Programme) [FP7-ENV-2010.2.2.1-3]; Foundation of Science and Technology of Portugal [SFRH/BPD/119344/2016, PTDC/MAR-EST/3223/2014]; Natural Environment Research Council (NERC) through the UK Ocean Acidification Research Programme (UKOARP) [NE/H017445/1]info:eu-repo/semantics/publishedVersio
Snapshot of macroalgae and fish assemblages in temperate reefs in the Southern European Atlantic Ecoregion
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.info:eu-repo/semantics/publishedVersio
Microplastic retention by marine vegetated canopies: simulations with seagrass meadows in a hydraulic flume
Marine canopies formed by seagrass and other coastal vegetated ecosystems could act as sinks of microplastics for being efficient particle traps. Here we investigated for the first time the occurrence of microplastic retention by marine canopies in a hydraulic flume under unidirectional flow velocities from 2 to 30 cm s-1. We used as model canopy-forming species the seagrass Zostera marina with four canopy shoot density (0, 50, 100, 200 shoots m-2), and we used as microplastic particles industrial pristine pellets with specific densities from 0.90 to 1.34 g cm-3 (polypropylene PP; polystyrene PS; polyamide 6 PA; and polyethylene terephthalate PET). Overall, microplastics particles transported with the flow were retained in the seagrass canopies but not in bare sand. While seagrass canopies retained floating microplastics (PP) only at low velocities (<12 cm s-1) due to a barrier created by the canopy touching the water surface, the retention of sinking particles (PS, PA, PET) occurred across a wider range of flow velocities. Our simulations revealed that less dense sinking particles (PS) might escape from the canopy at high velocities, while denser sinking particles can be trapped in scouring areas created by erosive processes around the eelgrass shoots. Our results show that marine canopies might act as potential barriers or sinks for microplastics at certain bio-physical conditions, with the probability of retention generally increasing with the seagrass shoot density and polymer specific density and decreasing with the flow velocity. We conclude that seagrass meadows, and other aquatic canopy-forming ecosystems, should be prioritized habitats in assessment of microplastic exposure and impact on coastal areas since they may accumulate high concentration of microplastic particles that could affect associated fauna.FCT: UIDB/04326/2020/ SFRH/BPD/119344/2016info:eu-repo/semantics/publishedVersio
Microplastics in commercial bivalves harvested from intertidal seagrasses and sandbanks in the Ria Formosa lagoon, Portugal
Through seafood consumption, microplastic (MP) pollution is potentially threatening human health. Commercial bivalves in particular are a cause of major concern because their filter-feeding activity directly exposes them to MP in the water column and they are then ingested by humans. Here, we provide a quantitative and qualitative baseline data on MP content in the soft tissues of three commercially important bivalves (Ruditapes decussatus, Cerastoderma spp. and Polititapes spp.) collected in Ria Formosa lagoon, southern Portugal. The abundance of MPs (items per soft tissue weight) did not significantly differ among species. On average, R. decussatus exhibited the highest MP abundance (on average, 18.4 +/- 21.9 MP items g(-1) WW), followed by Cerastoderma spp. (11.9 +/- 5.5 MP items g(-1) WW) and Polititapes spp. (10.4 +/- 10.4 MP items g(-1) WW). Overall, 88% of the MPs found were synthetic fibres, the majority of which were blue (52%). Size categories >0.1-1 mm and >1-5 mm were the most common (60% and 34% respectively). The most represented polymers were polyethylene (PE) and polystyrene (PS). The unexpectedly high number of MPs recorded in the three commercially exploited species suggests that this semi-closed lagoon system is experiencing a higher anthropogenic pressure than are open coastal systems.Portuguese Foundation for Science and Technology:
PTDC/MAR-EST/3223/2014
IF/01413/2014/CP1217/CT0004
UIDB/04326/2020
SFRH/BPD/119344/2016info:eu-repo/semantics/publishedVersio
Superficial sedimentary stocks and sources of carbon and nitrogen in coastal vegetated assemblages along a flow gradient
Coastal vegetated ecosystems are major organic carbon (OC) and total nitrogen (TN) sinks, but the mechanisms that regulate their spatial variability need to be better understood. Here we assessed how superficial sedimentary OC and TN within intertidal vegetated assemblages (saltmarsh and seagrass) vary along a flow gradient, which is a major driver of sediment grain size, and thus of organic matter (OM) content. A significant relationship between flow current velocity and OC and TN stocks in the seagrass was found, but not in the saltmarsh. OC and TN stocks of the saltmarsh were larger than the seagrass, even though that habitat experiences shorter hydroperiods. Mixing models revealed that OM sources also varied along the flow gradient within the seagrass, but not in the saltmarsh, showing increasing contributions of microphytobenthos (17-32%) and decreasing contributions of POM (45-35%). As well, OM sources varied vertically as microphytobenthos contribution was highest at the higher intertidal saltmarsh (48%), but not POM (39%). Macroalgae, seagrass and saltmarsh showed low contributions. Local trade-offs between flow current velocities, hydroperiod and structural complexity of vegetation must be considered, at both horizontal and vertical (elevation) spatial dimensions, for better estimates of blue carbon and nitrogen in coastal ecosystems.Foundation of Science and Technology of Portugal (FCT)
PTDC/MAR-EST/3223/2014
UID/Multi/04326/2013
FCT UID/MAR/00350/2018
SFRH/BPD/119344/2016info:eu-repo/semantics/publishedVersio
Vertical intertidal variation of organic matter stocks and patterns of sediment deposition in a mesotidal coastal wetland
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.info:eu-repo/semantics/publishedVersio
Loss of surficial sedimentary carbon stocks in seagrass meadows subjected to intensive clam harvesting
Seagrass carbon stocks are vulnerable to physical disturbance. We assessed the effect of clam harvesting on the
organic carbon (Corg) stocks in surface sediments in four intertidal Zostera noltei meadows on the Iberian Atlantic
coast (Spain and Portugal), by comparing undisturbed and harvested areas. We also monitored the spatial cover
of the meadows throughout the growing season. Sedimentary Corg content and Corg stocks were about four times
lower in intensively harvested areas than in control areas, but there were not differences between areas with low
harvesting pressure and control areas. Reductions of 53–85% in sedimentary Corg stocks of Z. noltei meadows
were caused by intensive clam harvesting. The effect of intensive clam harvesting on Corg stocks increased
throughout the growing season, but the area covered by the seagrass increased from 21 to 37%, suggesting rapid
recovery of seagrass canopies and potential recovery of sedimentary Corg stocks.info:eu-repo/semantics/publishedVersio
Carbon and nitrogen stocks and burial rates in intertidal vegetated habitats of a Mesotidal coastal lagoon
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.DL57/2016/CP1361/CT0002; MinECo, MDM2015-0552info:eu-repo/semantics/publishedVersio
A survey-based assessment of seagrass status, management and legislation in Europe
Seagrass meadows are ranked amongst the most productive ecosystems on Earth,
providing high-value ecosystem services in coastal areas. Yet, seagrass habitats are
declining worldwide at an unprecedented rate as a consequence of both anthropogenic
and natural pressures, which suggests an inefficient management. Seagrasses are
widespread along European coasts and the knowledge on their conservation status and
management has been increased in the last decade although an overall view for the
whole Europe is lacking. The general aim of this survey-based study was to assess the
present status of seagrass habitat conservation, management and legislation in Europe
based on the expert judgement of 25 participants from 19 coastal European countries.
We specifically assessed the seagrass ecological status and their major threats; the level
of awareness; the effort in mapping, monitoring and restoration; and the state of
management plans and policy in each country. We furthermore reviewed the legislation
for seagrass habitats in order to assess the protection status of seagrasses in Europe.
The survey-based assessment revealed great differences among seagrass species and
countries regarding their awareness, ecological status, mapping, monitoring and
management. Several good examples of seagrass management, in cooperation with
scientists, were identified although many countries still lack the fundamental tools for a
proper management. A consistent body of legislation was compiled for most European
countries, yet their implementation was reported to be rather variable and weak. The
results of this study will provide guidelines for a more effective seagrass management
and policy in Europe.info:eu-repo/semantics/publishedVersio
New aspect in seagrass acclimation: leaf mechanical properties vary spatially and seasonally in the temperate species Cymodocea nodosa Ucria (Ascherson)
Seagrasses may acclimate to environmental
heterogeneity through phenotypic plasticity. In contrast to
leaf morphology, which has been a central point in seagrass
acclimation studies, plasticity in leaf biomechanics and
fibre content is poorly understood, despite being crucial in
plant ecological performance, especially regarding physical
forces. We hypothesised that mechanical traits (e.g.
breaking force, strength, toughness, and stiffness) and fibre
content of seagrass leaves vary as morphology does under
differential environments. Cymodocea nodosa was seasonally monitored at three locations around Ca´diz Bay
(southern Spain) with hydrodynamic regime as the most
noticeable difference between them. Leaves showed plasticity in both morphology and mechanical traits, with
wave-exposed individuals presenting short but extensible
and tough leaves. Leaf fibre content was invariant along the
year and with little spatial variability. Cross-sectional area
rather than material properties or fibre content differentiates leaf mechanical resistance. Seagrass capacity to thrive
under a range of mechanical forces may be dictated by
their plasticity in morpho-biomechanical traits, a key element for the hydrodynamical performance and, hence, for
species colonisation and distribution.info:eu-repo/semantics/publishedVersio
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