Papers by María Eugenia Fanjul
Aquatic Botany, 2015
We present a comparative analysis of the biomass dynamics of the two dominant Spartina plant spec... more We present a comparative analysis of the biomass dynamics of the two dominant Spartina plant species in South West Atlantic saltmarshes: Spartina densiflora Brong. (high intertidal zone) and Spartina alterniflora Loesel. (mid-low intertidal zone). We assessed aboveground biomass, live: dead ratios, net production, mortality and turnover rates, and then used this information to understand if saltmarshes dominated by one or the other Spartina species have different ecosystemic roles in the recycling of organic matter. Through field sampling we found that S. densiflora had larger live, dead and total biomass than S. alterniflora. When comparing within each species, S. alterniflora had larger live than dead biomass for most of the year, while S. densiflora had more dead than live biomass. Through the Weigert and Evans (1964) net aerial primary production (NAPP) estimating method we found that S. densiflora had larger annual NAPP, annual mortality and live turnover rates than S. alterniflora. In both species the amount of NAPP was similar to the amount of annual mortality. These results suggest that S. densiflora aboveground biomass is a carbon accumulation zone, while S. alterniflora is a carbon recycling one.
Journal of Sea Research, Sep 1, 2018
Polychaetes and burrowing crabs are widely distributed in intertidal soft bottom environments, pl... more Polychaetes and burrowing crabs are widely distributed in intertidal soft bottom environments, playing an important role in structuring infaunal assemblages through trophic and non-trophic interactions such as bioturbation. In southwestern Atlantic (SWA; 37°40′S, 57°23′W) intertidal mudflats, the polychaetes Laeonereis acuta and Neanthes succinea coexist with the burrowing crab Neohelice (Chasmagnathus) granulata. N. granulata and L. acuta strongly modify the sediment characteristics at different spatial scales, changing the infaunal assemblages and probably affecting feeding mode of N. succinea, which could prey upon L. acuta. Here, we experimentally evaluated the effects of constant densities of L. acuta and N. succinea on the benthic species assemblages and sediment organic matter (OM) content in two contrasting scenarios of crab bioturbation: inside and outside crab beds. We found that (1) both polychaetes did not affect the mean density of other macrofaunal organisms neither the meiofauna in general, but L. acuta modifies the abundance of specific groups such as foraminiferans; (2) polychaetes produced changes in meiofaunal spatial distribution probably by adding habitat heterogeneity; and (3) no evidence of predation of N. succinea on L. acuta were observed. Additionally, the variable effects of polychaetes on chlorophyll and OM content showed that they were species-specific and also modified by crab bioturbation. Moreover, effects of crab bioturbation on primary producers, quality and content of OM, and on some macro and meiofaunal organisms were found. Our results suggest that the effects of L. acuta and N. succinea on benthic species and OM content are mostly species-specific and, with regard to food sources (OM content and microphytobenthic biomass), strongly modified by larger scale crab bioturbation.
Journal of Sea Research, 2015
Organic matter (OM) remineralization plays a key role in controlling the biogeochemistry of marin... more Organic matter (OM) remineralization plays a key role in controlling the biogeochemistry of marine sediments. Through their burrowing activities, bioturbating macrofauna not only induces physical, chemical and biological modifications, which can affect microbial communities responsible for organic matter remineralization, but it could also directly affect the distribution and bioavailability of sedimentary organic matter. Through in situ experiments manipulating crab and burrow density in intertidal soft-bottoms, we assessed if crab-bioturbation affects benthic metabolism, and the amount, distribution, and bioavailability of sedimentary OM. Crab-bioturbation enhanced overall benthic metabolism and benthic flux of dissolved OM toward the water column at both mudflat and saltmarsh zones. Moreover, our results revealed that bioturbation also changes the quality, bioavailability and distribution of sedimentary OM in mudflats and saltmarshes. Overall, bioturbation enhanced the proportion of labile organic carbon of bioturbated sediments and homogenized the sediment column in terms of their proportion of labile organic carbon. However, crabs also generated biogenic structures (e.g., mounds) that could promote spatial heterogeneity of high nutritional-value OM. Bioturbation-induced changes on benthic metabolism and on OM availability would result in a reduction of the storage capacity of carbon in our intertidal systems. Previous works indicated that crab-burrows trap detritus and OM-rich sediments. Our results suggest that detritus are efficiently remineralized at bioturbated sediment, and finally they are quickly exported to the water column as CO 2 and DOC. Thus, crabs are modifying the OM processing at intertidal soft bottoms, and the ways in which carbon is exported to coastal waters.
Estuarine Coastal and Shelf Science, Jul 1, 2010
Marine Ecology Progress Series, 2007
Through field experiments and chemical analysis of the sediment and pore water, we investigated t... more Through field experiments and chemical analysis of the sediment and pore water, we investigated the effect of the burrowing crab Chasmagnathus granulatus on the distribution and availability of electron acceptors in mudflat sediments. The results show that the presence and activity of C. granulatus and its burrows determine the chemical characteristics of pore water and the redox state of mudflat sediments. Crabs enhance the transport of particulate material in the sediment column, completely mixing the upper 7 cm of sediment in a few days. Comparative analyses of pore water from areas (1) with crabs and burrows, (2) with unoccupied burrows, and (3) without burrows or crabs reveal a large increase in sediment oxygenation, modification of pore water salinity and the distribution of dissolved inorganic nitrogen and sulphate when crabs are present. Denitrification and organic matter (OM) degradation rates were estimated by a diagenetic model that searches for simultaneous agreement between measured and model-calculated depth profiles. OM degradation rates (kG) were found to be greater in bioturbated (kG = 10.6 ± 6.1 [SD] µM s-1) than in non-bioturbated sediments (kG = 4.9 ± 17.8 µM s-1 if unoccupied burrows were present; kG = 0.02 ± 0.013 µM s-1 without burrows). Model-estimated denitrification rates revealed that OM degradation pathways are also affected by C. granulatus activities and their burrows. These changes in the sediment chemistry that are directly and indirectly produced by C. granulatus could comprise the force that drives the pathways of microbial processes and nutrient flows to neighbouring systems.
Journal of Ecology, Jan 11, 2008
1. Arbuscular mycorrhizal fungi (AMF) can affect nutrient uptake of associated plants and can var... more 1. Arbuscular mycorrhizal fungi (AMF) can affect nutrient uptake of associated plants and can vary in function from mutualism to parasitism as nutrient availability increases; thus they may interact with nutrient availability to influence plant community structure. 2. We experimentally investigated the hypotheses that AMF can affect the community structure of salt marshes by affecting plant competitive ability. We focused on: Spartina densiflora , that dominates physically benign high marsh habitats and S. alterniflora , which dominates more stressful low marsh habitats. 3. Colonization by AMF increased S. densiflora growth at low nutrient levels, but reduced growth at high nutrient levels. Spartina alterniflora was not colonized by AMF and showed increased growth only with nutrient amendment. Nutrient or fungicide additions resulted in S. alterniflora migrating to higher marsh elevations, displacing S. densiflora. When nutrient and fungicide additions were made together, however, dominance of S. densiflora was maintained in the high marsh. 4. Synthesis. These results show that AMF can affect the competitive ability of plants and can have a large impact on plant community structure. The community impacts of these symbioses may be especially sensitive to human-induced eutrophication, given that nutrient supply can modulate whether AMF positively or negatively affect associated plants.
Estuaries and Coasts, Jun 3, 2014
Over the history of ecology, well-established generalizations were refined or even changed after ... more Over the history of ecology, well-established generalizations were refined or even changed after the appearance or consideration of new evidence. Here, we review results obtained in Southwestern Atlantic salt marshes (between southern Brazil −32°1′ Sand the Argentinean Patagonia −53°48′ S-). Most of these salt marshes are inhabited by the intertidal burrowing crab Neohelice granulata, a species that influences many ecological processes through bioturbation and herbivory. The experimental evaluation of these processes shows that in some cases, the results were not consistent with generalizations and models of salt marsh ecological functioning. However, this does not imply that the generalizations grounded mainly on the results from North American sites are not valid. In turn, we suggest that these apparently conflicting results emerged because two major processes, herbivory and bioturbation, have been overlooked until recently. Thus, their relative contribution has not been included in the models of salt marsh functioning. In conclusion, we believe that there is a need for performing parallel and simultaneous experiments comparing distant sites with varying environmental (i.e., abiotic and biotic) conditions to be able to uncover common processes and causes of contingencies. Particularly, Southwestern Atlantic salt marshes could lead the way in providing information to better incorporate herbivory and bioturbation into current models or paradigms about how salt marshes work.
Marine Ecology Progress Series, Sep 17, 2018
Despite long-standing interest in the hypothesis that strength of plant-herbivore interactions de... more Despite long-standing interest in the hypothesis that strength of plant-herbivore interactions decreases at higher latitude, supporting evidence is scarce and the data is conflicting. By field survey and two experiments we examined this hypothesis focusing on the herbivory by the stem-borer moth (Haimbachia sp. nov.) on the dominant SW-Atlantic marsh grasses (Spartina alterniflora and S. densiflora). Field surveys indicate that herbivore abundances and damage, although tend to decrease simultaneously, are unrelated to latitude. Herbivore abundances were related to latitude-dependent variables such as day length and temperature, and also to latitude-independent variables such as precipitation, salinity, and tide amplitude. Abundances were indirectly related to the effects of these variables and sediment characteristics on plant traits like density, height and tissue-composition. After 33-months, herbivore abundances and damage of high-latitude plants transplanted to low-latitude were 50-times greater than plants transplanted from low-to high-latitude sites. In a common-garden experiment (38º 56´ S) without herbivore pressure, differences persisted in plant traits from high and low latitude suggesting lack of herbivore induced effects on these plant traits. The persisting conspecific differences in plant-traits translocated along latitude suggest that these variations are under genetic control. Thus, our results provide evidence that although plantherbivory interactions are more important at lower latitude, many additional and contingent variables unrelated with latitude can divert this geographic pattern.
Helgoland Marine Research, Nov 13, 2007
Echinolittorina peruviana is the most common gastropod in the high intertidal zone of Peru, repre... more Echinolittorina peruviana is the most common gastropod in the high intertidal zone of Peru, representing more than 80% of the individuals present at that zone. Experimental removal of snails was used to evaluate their eVects on (a) abundance of epilithic bioWlm, (b) barnacle recruitment, and (c) abundance of macroalgae under "normal" conditions of the El Niño Southern Oscillation (ENSO). Experiments were carried out from October 2005 to April 2007 at two intertidal levels of a semi-protected rocky shore of central Peru. Results demonstrated that E. peruviana is able to control bioWlm abundance and barnacle recruitment at both heights investigated, with marked eVects in the lower zone. Erect macroalgae (Ulva spp. and Gelidium spp.) were less aVected by grazing; but negative eVects were observed on macroalgal crusts. Season and physical stress seem to play a more important role in the abundance of macroalgae in the high intertidal. Our results are similar to those reported elsewhere for high shore littorinids and represent baseline data to understand how the role of intertidal consumers will vary under the cold (La Niña) and warm (El Niño) phases of ENSO on these shores.
Journal of Sea Research, Jul 1, 2011
The reef-forming polychaete Ficopomatus enigmaticus is the main benthic suspension-feeding specie... more The reef-forming polychaete Ficopomatus enigmaticus is the main benthic suspension-feeding species of the Mar Chiquita lagoon (37°40′ S, 57°23′ W; Argentina) and exerts a strong top-down control on phytoplankton biomass. A large portion of the ingested material is rejected as faeces, and a fraction of the material filtered is packed and discarded as pseudofaeces, which could be deposited on the sediment or horizontally displaced by water flow. In this work we evaluate the effect of this biodeposition on the organic matter (OM) content and productivity of the sediment between reefs. Laboratory experiments show that the OM from biodeposition was 21 times higher than the sediment between reefs and with low C per mg matter/N per mg matter. Sediment traps underneath live reefs showed higher OM content compared to traps underneath dead reefs but only in areas with low water currents, suggesting the importance of hydrodynamic conditions for this process. In situ mesocosms showed that F. enigmaticus decreased up to 45% the phytoplankton biomass, up to 50% the turbidity and up to 20% the particulate OM of the water column and, consequently enhanced up to 50% the OM deposited on the bottom. But there were no differences in the OM of sediment with increased distance from the reefs. Sediment gross primary production was lower in the sediment closer to reefs, but when adults of the high-density local crab that live underneath reefs were excluded, the productivity increased, suggesting that the activity of the crabs could be counteracting the reef effect on sediment. In summary, biodeposits of F. enigmaticus can enrich the sediment, but crab activity and water currents can disperse the suspended and/or deposited material, decreasing the OM content of sediment close to the reefs. However, these effects (suspension feeding and biodeposition) are linked, and could increase flux of particles from water column to the bottom of the lagoon, increasing the benthic-pelagic coupling.
Estuaries and Coasts, Aug 8, 2008
... Southern West Atlantic salt marshes (southern Brazil to Northern Argentinean Patagonia) are d... more ... Southern West Atlantic salt marshes (southern Brazil to Northern Argentinean Patagonia) are dominated by the cordgrasses, Spartina densiflora and Spartina alterniflora (see ... maintenance results in sediment removal of up to 2.5 kg m −2 day in the marsh area (Iribarne et al. ...
Journal of Vegetation Science, Jul 30, 2020
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Journal of Sea Research, Aug 1, 2011
Two cordgrass species of the genus Spartina cohabit in SW Atlantic (southern Brazil 31º48′ S to A... more Two cordgrass species of the genus Spartina cohabit in SW Atlantic (southern Brazil 31º48′ S to Argentinean Patagonia, 43º20′ S) salt marshes. Some salt marshes are dominated by the dense-flowered cordgrass Spartina densiflora (which inhabits the upper intertidal level) and others by the smooth cordgrass Spartina alterniflora (which inhabits the lower intertidal level). We investigated how the different species dominance affects the detritus dynamics in the Bahia Blanca estuary (38º47′ S, 62º20′ W Argentina). Field measurements of annual detritus production using destructive methods show that both plants are similar. However, detritus of S. alterniflora shows higher decomposition rates than that of S. densiflora. This difference may be due to a larger N content, lower lignocellulose content and lower C/N ratio of S. alternifora when compared with S. densiflora. Moreover, field sampling shows that S. alterniflora has a larger amount of trapped litter that, according to the litterbag method, has higher decomposition rates. Therefore it is highly likely that S. alterniflora salt marshes contribute towards more profitable detritus for estuarine food webs than marshes dominated by S. densiflora. These results illustrate that the composition of the coastal plant community can determine the quality and profitability of the detritus that support estuarine food webs. They also illustrate that salt marshes belonging to a same biogeographic group and even coexisting in great proximity can have very different ecosystemic roles.
Estuarine Coastal and Shelf Science, Oct 1, 2021
Scientific Reports, 2017
Altered nutrient cycles and consumer populations are among the top anthropogenic influences on ec... more Altered nutrient cycles and consumer populations are among the top anthropogenic influences on ecosystems. However, studies on the simultaneous impacts of human-driven environmental alterations on ecosystem functions, and the overall change in system multifunctionality are scarce. We used estuarine tidal flats to study the effects of changes in herbivore density and nutrient availability on benthic microalgae (diversity, abundance and biomass) and ecosystem functions (N2-fixation, denitrification, extracellular polymeric substances -EPS- as a proxy for sediment cohesiveness, sediment water content as a proxy of water retention capacity and sediment organic matter). We found consistent strong impacts of modified herbivory and weak effects of increased nutrient availability on the abundance, biomass and diversity of benthic microalgae. However, the effects on specific ecosystem functions were disparate. Some functions were independently affected by nutrient addition (N2-fixation), mod...
Marine Ecology Progress Series, 2019
In coastal systems, benthic microalgae are important primary producers that significantly contrib... more In coastal systems, benthic microalgae are important primary producers that significantly contribute to global primary production. Microphytobenthic (MPB) community structure and the ecosystem functions that it mediates are modulated by biotic and abiotic factors. Through burrowing activity, different types of bioturbators can impact MPB in different ways. Through directed sampling and field experiments performed at the Mar Chiquita coastal lagoon (Argentina), we evaluated the effect of regenerative bioturbation (continuous digging and maintenance of burrows, with sediment transfer from depth to surface) by the intertidal burrowing crab Neohelice (Chasmagnatus) granulata on MPB. We compared sediment properties and MPB attributes between natural burrowed and non-burrowed areas. Moreover, we experimentally manipulated regenerative bioturbation to evaluate if MPB composition and primary production are altered by crab burrowing activity. Field sampling showed that MPB and sediment properties differed between natural burrowed and non-burrowed areas. Experimental results indicated that regenerative bioturbation by N. granulata increased sediment oxygen concentration at each measured depth and also changed MPB composition (due to the reduced total abundance of cyanobacteria), but nearly doubled primary production in comparison with plots without bioturbation. Thus, the net effects of regenerative bioturbation were positive for MPB productivity, reinforcing the idea that this kind of bioturbation is an important biological force that enhances primary production in intertidal systems.
Journal of Experimental Marine Biology and Ecology
Marine Ecology Progress Series, 2018
Table S1. Climate data: Temperature: maximum = MaxT (ºC), minimum = MinT (ºC), average = AverT (º... more Table S1. Climate data: Temperature: maximum = MaxT (ºC), minimum = MinT (ºC), average = AverT (ºC), and maximum thermal amplitudes = DelT (ºC); annual precipitation = Prec (mm), and differences en day length = Dlen (h). Physical condition of water that flood marshes: average of tides amplitudes =Tides (m), and water salinity = Salinity (PSU). Sediment characteristics: content in moisture = Moisture (%), mud = Mud (%), sand = Sand (%), grave = Grave (%), organic matter = OM (%) and oxygen: O 2 (umol x l-1) of both marshes (low dominated by Spartina alterniflora and high, dominated by S. densiflora) along 8 southwestern Atlantic coastal marshes: the outlet of Salado River (SAL), San Clemente (SC), Bahía Blanca (BB), Bahía Anegada (BA), the outlet of Rio Negro (RN), Bahía San Antonio (BSA), Riacho San Jose (RSJ), and the outlet of Rio Chubut (RCH). Different lowercase letters denote significant differences between sites at p < 0.05 with Tukey's honestly significant difference test.-: absence of plants at that location.
Estuarine Coastal and Shelf Science, 2021
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Papers by María Eugenia Fanjul