Cordgrass canopy elicits weak effects on sediment properties and microphytobenthic abundance in a harsh environment

Abstract

The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stresses increase, habitat amelioration by ecosystem engineers becomes more relevant. Moreover, the individual-and population-level traits of ecosystem engineers can affect their ability to reduce environmental stress. On the Patagonian shores of Argentina (SW Atlantic, 41°S), the intertidal community is exposed to harsh conditions. We predicted that in this severe environment, variation in the above-ground structure of the smooth cordgrass Spartina alterniflora should buffer the physical stress on the substrate through shading and reduction of wind and water flow energy, ultimately affecting the sediment properties and microphytobenthic biomass. To test this hypothesis, we experimentally manipulated cordgrass density at the edge and inner marsh of a S. alterniflora meadow during both summer and winter. In summer, evaporation and temperature were higher in clipped plots, while in winter, evaporation varied across densities and location treatments, with higher sediment water content in the inner marsh. No effect of S. alterniflora density or location were observed on sediment organic matter or chl a concentration, and mean sediment grain size was always smaller inside the marsh. In summer, extracellular polymeric substance (EPS) content was higher in clipped plots inside the marsh, however this did not differ from the other density treatments at this location. Overall, shading had weak effects on sediment properties and microphytobenthic biomass, and most observed differences were attributable to grain size. We speculate that the harsh conditions of this system overwhelm the ecosystem engineering effects of S. alterniflora, probably because of its relatively small aboveground biomass.

Mechanism of removal and retention of heavy metals from the acid mine drainage to coastal wetland in the Patagonian marsh

“…Some of them drain towards the endorheic depressions located inside the deposits, while another are mobilized in solution with the surface runoff towards the salt marsh. The water drainage accumulated above the mining waste deposits is then evaporated favoured by the arid climate (Firstater et al, 2016). The sulphates formed by total evaporation of the drainage water varies, in the mining waste deposits, according to the topographic features.…”

“…The climate is semi-arid, the mean annual precipitation is around 250 mm, and the mean annual air temperature is 15.1 C, fluctuating between mean extremes of À7.7 C in July to 41.4 C in February (Firstater et al, 2016). The mean annual wind speed is 18 km h À1 , reaching an average of 25 km h À1 in the hotter seasons (Firstater et al, 2016).…”

“…The climate is semi-arid, the mean annual precipitation is around 250 mm, and the mean annual air temperature is 15.1 C, fluctuating between mean extremes of À7.7 C in July to 41.4 C in February (Firstater et al, 2016). The mean annual wind speed is 18 km h À1 , reaching an average of 25 km h À1 in the hotter seasons (Firstater et al, 2016). The salt marsh is dominated by Spartina species, being Spartina alterniflora the only species present in the lower marsh zone, and the higher zones are inhabited by Spartina densiflora, and the shrubs Limonium brasiliense, Sarcocornia perennis and Atriplex spp (Bortolus et al, 2009;Idaszkin et al, 2015).…”

Epibiosis in sedimentary coastal environments: Effects of an introduced barnacle on a native mussel

“…The intertidal is characterized by extensive sediment‐covered flats with a wide range of grain sizes (silt, sand, and gravel—including granules, pebbles, cobbles and mollusk‐shell fragments; Firstater et al., 2016; Pereyra et al., 2009; Salas et al., 2016; Figure 2). In the mid‐intertidal, the mussel B. rodriguezii is found attached to the mobile substrate there, forming dense monolayered beds of variable extent.…”

“…The San Antonio Bay (40° 45 'S, 64° 56' W, Figure 1) is located in the northwest of the San Matías Gulf (Patagonia, Argentina) and has a semidiurnal tidal regime that varies between 6 m and 9 m of amplitude, with moderate waves influence. This bay is a hypersaline environment (37.6 ± 8.4‰) due to the low rainfall, lack of freshwater supply (Piola & Scasso, 1988;Saad et al, 2019), and a high evaporation rate (up to ~0.9 L.h -1 m -2 in summer; Firstater et al, 2016). The unique features of the physiography and hydrologic regime of this coastal region create an environment of particular ecological importance as a reservoir of biodiversity and for the conservation of seabirds (González et al, 1996(González et al, , 2003.…”