Paula Pratolongo

First record of the sea anemone Diadumene lineata (Verrill 1871) associated to Spartina alterniflora roots and stems, in marshes at the Bahia Blanca estuary, Argentina

We report the occurrence of the orange-striped green anemone Diadumene lineata (Verrill 1871) (=Haliplanella lineata) in salt marshes at the Bahía Blanca Estuary for the first time in August 2005. We also found this species attached to roots and stems of Spartina alterniflora, an association that has never been registered before. After their determination, sampling was performed during a year to evaluate seasonal abundance of this sea anemone. Results showed that D. lineata was present through the whole year, indicating the existence of a stable population. All individuals sampled were found attached to roots or stems of S. alterniflora, with the higher abundances detected in summer. Further studies are necessary to precise the potential effects of this exotic sea anemone on salt marsh communities.

Relating Biophysical Parameters of Coastal Marshes to Hyperspectral Reflectance Data in the Bahia Blanca Estuary, Argentina

ABSTRACT González Trilla, G.; Pratolongo, P.; Beget, M.E.; Kandus, P.; Marcovecchio, J., and Di Bella, C., 2013. Relating biophysical parameters of coastal marshes to hyperspectral reflectance data in the Bahia Blanca Estuary, Argentina. Salt marshes occupying the tidal fringe of estuaries and protected coasts provide valuable ecosystem services, and remote sensing is a powerful tool for their large-scale monitoring. However, in order to apply remote sensing techniques to evaluate the ecological state of salt marshes, a deeper understanding is needed about the interactions between field biophysical parameters and the sensors reflectance. The main objective of this work is to analyze and quantify the influence of different biophysical parameters characterizing stands of Spartina alterniflora marshes in the Bahia Blanca Estuary, Argentina, on their spectral response. Spectral reflectance at high resolution was measured in S. alterniflora canopies under natural conditions, manipulating standing biomass by means of successive harvestings. Reflectance data were acquired using a FieldSpec® spectroradiometer, which measures in the visible, near-infrared, and shortwave-infrared spectral bands. Based on these reflectance data, spectral indices such as the normalized difference vegetation index (NDVI) were calculated for each biomass condition. Biomass, leaf area index (LAI), percent canopy cover (PCC), water content, and soil properties were also evaluated. LAI, PCC, and biomass were positively correlated between each other. As a general trend, as biomass decreased, absorption in red wavelengths decreased and reflectance in near-infrared increased. Several indices explained the variability in LAI, biomass, and PCC. For example, NDVIRouse had a positive regression with PCC (R2 = 0.80, N = 75) and LAI (R2 = 0.67, N = 75). Results indicate that LAI, biomass, and PCC of Spartina alterniflora could be accurately determined from spectral data.

Ecological processes and biogeochemical cycling in salt marshes: synthesis of studies in the Bahía Blanca estuary (Argentina)

Here we offer an integrative review of biogeochemical cycling of carbon, nitrogen, phosphorus, and several metals in salt marshes of the Bahía Blanca Estuary, located in South America, which is a region underrepresented in the literature. The dominant species, Spartina alterniflora and Sarcocornia perennis, have low net aboveground primary productivity but play substantial and contrasting roles in the biogeochemical cycling of elements. S. perennis was more efficient at metal sequestration, whereas S. alterniflora was important in the immobilization of phosphorus. Because of the differences in net aboveground primary productivity between high and low marsh, plant position should be considered to evaluate the role of S. alterniflora on biogeochemical cycles. Some elements were also in high concentrations in belowground tissues but, based on our data, we could not accurately estimate net belowground primary productivity, a key process to evaluate elemental cycling in salt marshes. In spite of uncertainties in the estimations, the slower decomposition rates in S. alterniflora would be indicative of a higher contribution to the long-term storage of nutrients and metals within the marsh. Regardless shortcomings, our work represents a valuable tool for comparisons with salt marshes worldwide.

Coastal Environments in the Bahía Blanca Estuary, Argentina

The Bahia Blanca Estuary is a coastal system placed in a sharp transition between humid subtropical and semiarid climates, shaped by a unique combination of large interanual climatic variations and a transgressive sea level during the Holocene. In the region, the late Holocene marine transgresion resulted in low coastal landforms inherited from the former estuarine dynamics. These environments are commonly occupied by coastal ecosystems that can be roughly classified into intertidal and inland (perimarine) wetlands. Within the intertidal zone, most of the area is covered by extensive barren mudflats, and marshes are dominated by Spartina alterniflora or Sarcocornia perennis. A supralittoral zone can be defined in an intermediate position, irregularly inundated by sea water. Vegetation in this zone is sparse, with a mosaic of salt flats, halophytic steppes and shrubs forming mound-intermound complexes. The Old Marine Plain, in the inland limits of the marine transgression is not affected by tidal flooding, but an irregularly humid zone develops due to saline seepage from the uplands. These wetlands are subjected to episodic disappearance, and may get dry for several years, relying on the occurrence of rainy years during humid periods to resurge. Because of their highly dynamic nature, and the particular climatic settings of the area, these wetlands are sensitive indicators of climate change and variations in large scale circulation patterns. This chapter describes climatic patterns, geomorphological settings, and plant communities, as well as the major physical and biological interactions defining landscape structure.

Community Structure and Spatial Zonation of Benthic Macrofauna in Mudflats of the Bahía Blanca Estuary, Argentina

ABSTRACT Zapperi, G.; Piovan, M.J., and Pratolongo, P., 2018. Community structure and spatial zonation of benthic macrofauna in mudflats of the Bahía Blanca Estuary, Argentina. The variations in composition of the benthic community and specific physical variables of mudflats in the Bahía Blanca Estuary, across the intertidal gradient, are described. An upper mudflat, with a steeper slope and higher densities of crab burrows exists seaward of a gently-sloped lower zone, where the density of crab burrows progressively diminishes. Monthly samples were collected from both sections of mudflats to analyze the composition of macrozoobenthos, as well as physical and chemical variables in sediments. Neohelice granulata and Polydora sp. were representative species of the upper mudflat. N. granulata had significantly higher densities in January (236 ± 136 individuals per square meter [ind m−2]) and February (200 ± 68 ind m−2), and Polydora sp. had significantly higher densities in May (491 ± 398 ind m−2). N. granulata did not appear in samples from the lower mudflat. There, densities of Laeonereis culveri were significantly higher, with peaks in June (8604 ± 3341 ind m−2) and October (7604 ± 1908 ind m−2). In the upper section, a single peak was observed in September (2455 ± 1281 ind m−2). Chlorophyll-a concentrations in sediments from the upper mudflat showed a single peak in July (10.1 ± 0.77 μg cm−2). In the lower zone, two peaks were observed in July (10.4 ± 0.18 μg cm−2) and March (10.5 ± 3.1 μg cm−2). These occurred 2 to 3 months before the peak densities of L. culveri were observed. Bulk density, water content of sediments, and shear strength were significantly different between zones, suggesting sediments are more compact and less hydrated in the upper section and hence more resistant to erosion. Major differences were found between the upper and the lower section of mudflats in terms of their biological communities, their seasonal patterns of activity, and the characteristics of the physical environment leading to erodibility.

Effect of “Whitemouth Croaker” (Micropogonias furnieri, Pisces) on the Stability of the Sediment of Salt Marshes—an Issue To Be Resolved

Among the predators, fish are prevalent in intertidal soft-bottom zones, and many create substantial interruptions in the sediment surface through their feeding, thus affecting the movement of fluids in the sediment-water interface and therefore the rates of deposition and local erosion. This study was designed to determine whether or not Micropogonias furnieri—an ecologically significant benthophagic southwestern Atlantic Ocean predator—modified erosion and/or sedimentation processes in salt marshes. The results indicated that this species exhibited a preference for areas without vegetation cover at the time of feeding since a greater abundance of pits was found in those environments. Moreover, the volume analysis of the pits in the two areas indicated that the size of the fish that had foraged in the sediment was significantly larger in the nonvegetated areas. The results of the M. furnieri-exclusion experiment indicated that the presence of this sciaenid neither resulted in a decrease in benthic organisms in the nonvegetated areas nor affected the vertical distribution of the infauna. When M. furnieri was excluded, the sediment exhibited higher critical-shearing and frictional-velocity values than in areas where M. furnieri had access and therefore was less likely to be eroded. The data from these experiments enabled us to conclude that the foraging action of M. furnieri modified the stability of the sediment as a result of the predatory pressure that the fish exerted on the organisms inhabiting the salt marshes, thus resulting in the generation of elliptical depressions. That modification of the sediment stability was evidenced in two principal ways: (i) a negative effect on the microphytobenthic organisms that decreased the concentration of extracellular polymeric substances in the sediment and (ii) an increased roughness of the bottom and increased percentage of sand in the particle composition of the sediment, where the fish had foraged.