The Far Reaching Impacts of Aging

This presentation features the session\u27s panelists and Nebraska population statistics and projections

Differences in the macrozoobenthic fauna colonising empty bivalve shells before and after invasion by Corbicula fluminea

Bivalve shells can potentially alter the structure of aquatic benthic communities. However, little is known about the effect that different shell morphologies have on their associated fauna. This study aimed to understand how empty shells, from four different freshwater bivalve species, affect macrozoobenthic communities, using the River Minho (Iberian Peninsula) as a study area. Three native (Anodonta anatina, Potomida littoralis, Unio delphinus) and one non-indigenous (Corbicula fluminea) species were used for this research. Comparisons among species and between scenarios (i.e. before and after invasion by C. fluminea) were performed. Our results suggest that macrozoobenthic community structure did not vary among treatments, with the exception of species richness, which was higher on shells of native species. Furthermore, little difference was detected when comparing scenarios with and without C. fluminea shells, despite dissimilarities in size and morphology between species. The empty shells of C. fluminea partially (in terms of density and biomass, but not in species richness) replaced the role of empty shells of native species as a physical substratum for the associated macrozoobenthic community.Martina Ilarri is supported by a Post-doc grant (SFRH/BPD/90088/2012) from the Portuguese Foundation for Science and Technology – FCT through POPH/FSE funds. This study was conducted within the scope of the project ECO-IAS: Ecosystem-level impacts of an invasive alien species, supported by FCT and COMPETE funds (contract: PTDC/AAC-AMB/116685/2010) and was also partially supported by the European Regional Development Fund (ERDF) through COMPETE funds (PEst-C/MAR/LA0015/2011) and by FCT/MEC through Portuguese funds (PIDDAC – PEst-OE/BIA/UI4050/2014).info:eu-repo/semantics/publishedVersio

Trophic niche overlap between native freshwater mussels (Order: Unionida) and the invasive Corbicula fluminea

Freshwater mussels (Order Unionida) are highly threatened. Interspecific competition for food sources with invasive alien species is considered to be one of the factors responsible for their decline because successful invaders are expected to have wider trophic niches and more flexible feeding strategies than their native counterparts. In this study, carbon (δ13C: 13C/12C) and nitrogen (δ15N: 15N/14N) stable isotopes were used to investigate the trophic niche overlap between the native freshwater mussel species, Anodonta anatina, Potomida littoralis, and Unio delphinus, and the invasive bivalve Corbicula fluminea living in sympatry in the Tua basin (south-west Europe). The species presenting the widest trophic niches were C. fluminea and A. anatina, which indicate that they have broader diets than U. delphinus and P. littoralis. Nonetheless, all the species assimilated microphytobenthos, sediment organic matter, and detritus derived from vascular plants, although with interspecific variability in the assimilated proportions of each source. The trophic niche of the invasive species overlapped with the trophic niche of all the native species, with the extent varying between sites and according to the species. From the three native species analysed, Potomida littoralis may be at a higher risk for competition for food with C. fluminea in the Tua basin, if food sources become limited, because this native mussel presented the narrowest trophic niche across sites and the highest probability of overlapping with the trophic niche of C. fluminea. Given the global widespread distribution of C. fluminea, the implementation of management measures devoted to the control or even eradication of this invasive alien species should be a conservation priority given its potential for competition with highly threatened native freshwater mussels.V.M. and P.C. were supported by doctoral grants SFRH/BD/108298/2015 and SFRH/BD/131814/2017, respectively, from the Portuguese Foundation for Science and Technology—FCT through POPH/FSE funds. FCT also supported M.L.L. under contract (2020.03608.CEECIND). This study was conducted within the project FRESHCO – Multiple implications of invasive species on Freshwater Mussel coextinction processes, supported by FCT and COMPETE funds (contract: PTDC/AGRFOR/1627/2014). This study was also supported by national funds through FCT – Foundation for Science and Technology within the scope of UIDB/04423/2020 and UIDP/04423/2020. We thank Jacinto Cunha for providing Figure 1.info:eu-repo/semantics/publishedVersio

Two microcrustaceans affect microbial and macroinvertebrate-driven litter breakdown

1. Leaf litter degradation in fresh waters is a fundamental ecosystem process performed by a wide array of decomposers. The meiofauna is an important component of aquatic heterotrophic assemblages, which can provide a trophic link between plant detritus and associated microbial and macroinvertebrate communities, but their contribution to leaf breakdown remains poorly understood. 2. We hypothesised that, through their feeding activity, microcrustaceans influence the structure of fungal assemblages and consequently microbially mediated litter breakdown. Litter-associated microcrustaceans were predicted to change the pathways of energy transfer in the food web according to the positive (e.g. complementarity) or negative (e.g. predation) interactions with macroinvertebrate detritivore taxa. 3. We evaluated experimentally in the laboratory, over 6 and 13 days, the potential contribution of two freshwater microcrustaceans (a cladoceran and a copepod) to litter breakdown in the presence of microfungi (aquatic hyphomycetes), with and without macroinvertebrate detritivores (a trichopteran and a gammarid amphipod). 4. The presence of microcrustaceans enhanced leaf mass loss by 62 and 22% in treatments with fungi or trichopteran alone, respectively, while no significant effect was observed for treatments with the amphipod. Microcrustaceans strongly increased the production of fine particulate organic matter, particularly in treatments with fungi alone (+637%). The leaf consumption rate by the amphipod significantly decreased ( 61%) at 13 days in the presence of microcrustaceans, likely due to predation on cladocerans. 5. Our study supports the potential role of microcrustaceans in the detrital food web of streams and rivers. Interestingly, microcrustaceans may interact with microbial and macroinvertebrate decomposers in either positive or negative ways. Therefore, microcrustaceans add complexity to detrital food webs by increasing vertical diversity and modulating biotic interactions with important consequences for carbon and energy transfers in stream ecosystems

Sedimentary context controls the influence of ecosystem engineering by bioturbators on microbial processes in river sediments

By modifying the physical environment, ecosystem engineers can have inordinately large effects on surrounding communi- ties and ecosystem functioning. However, the significance of engineering in ecosystems greatly depends on the physical characteristics of the engineered habitats. Mechanisms underlying such context-dependent impact of engineers remain poorly understood even though they are crucial to establish general predictions concerning the contribution of engineers to ecosystem structure and function. The present study aimed to decrypt such mechanisms by determining how the environmental context modulates the effects of ecosystem engineers (bioturbators) on microorganisms in river sediments. To test the effects of environmental context on the role of bioturbators in sediments, we used mesocosms and recreated two sedimentary contexts in the labo- ratory by adding a layer of either fine or coarse sand at the top of a gravel-sand matrix. For each sediment context, we examined how the sediment reworking activity of a bioturbating tubificid worm (Tubifex tubifex) generated changes in the physical (sediment structure and permeability) and abiotic environments (hydraulic discharge, water chemistry) of micro- organisms. Microbial characteristics (abundances, activities) and leaf litter decomposition – a major microbially-mediated ecological process – were measured to evaluate the impact of bioturbation on biotic compartment. Our results showed that the permeability, the availability of oxygen and the activities of microorganisms were reduced in sediments covered with fine sand, in comparison with sediments covered with coarse sand. Tubifex tubifex signifi- cantly increased permeability (by about six-fold), restored aerobic conditions and ultimately stimulated microbial com- munities (resulting in a 30% increase in leaf litter breakdown rate) in sediments covered with fine sand. In contrast T. tubifex had low effects in sediments topped by coarse sand, where O2 was already available for hyporheic microorgan- isms. Our study supports the idea that context dependency mainly modulates the effects of engineering by controlling the ability of engineers to create changes on abiotic (O2 in the present study) factors that are limiting for surrounding communities

Impact of Dreissena fouling on the physiological condition of native and invasive bivalves : interspecific and temporal variations

The impact of Dreissena fouling on unionids has hardly been studied in Europe, despite the fact that in some ecosystems (e.g. Lake Balaton, Hungary) infestations of several hundreds to a thousand individuals per unionid have been observed. At present, the zebra mussel Dreissena polymorpha is a dominant species in Lake Balaton and in the last decade three other invasive bivalves were introduced, potentially increasing the pressure on native unionid survival. We examined whether the fouling of dreissenids (zebra and quagga (D. rostriformis bugensis) mussels) has a negative impact on native (Anodonta anatina, Unio pictorum and U. tumidus) and invasive (Corbicula fluminea and Sinanodonta woodiana) bivalves and whether there are any interspecific and temporal variations in fouling intensity and physiological condition measured by standard condition index and glycogen content. A significant negative impact was detected on native unionids only in July and September (no impact was detected in May), when the fouling rate was high. For invasive species, a significant negative impact was detected on S. woodiana with a high level of dressenid infestation; whereas no significant impact was detected on C. fluminea. Overall, this study confirms that Dreissena may threaten unionid species including the invasive S. woodiana, although high interspecific and temporal variations were observed. This situation should be taken into account in future ecological and conservational assessments because species respond differently to Dreissena fouling and effects seem to be more pronounced in late summer/early autumn. In addition, this study provides the first evidence that the invasive C. fluminea appear to be less vulnerable to dressenid fouling.The study was supported by the Hungarian Scientific Fund (KTIA-OTKA) under the contract No. CNK80140

Distribution of Corbicula fluminea (Müller, 1774) in the invaded range: a geographic approach with notes on species traits variability

Corbicula fluminea is considered one of the most important non-native invasive species (NIS) in aquatic systems mainly due to its widespread distribution and ecological and economic impacts. This species is known to negatively affect native bivalves, also with severe effects on biodiversity and ecosystem functioning. Throughout an exhaustive bibliographic survey and with the aid of Geographic Information Systems tools, this study tracks the species dispersion from its native range, including the description of important physical and environmental barriers. Additional analyses were conducted to examine possible influences of latitudinal/ temperature gradients on important traits (e.g. life span, maximum and mean body length, growth at the end of first year). Altitude and winter minimum temperature appear to be delaying the invasion worldwide, but it seems inevitable that the species will spread across the globe. Latitude and summer temperature show a relationship with growth and life span. Overall, the information gathered in this review may be relevant to forecast future distribution patterns of this NIS, and to anticipate the possible implementation of effective management measures. Moreover, it may constitute a valuabletool inthe prediction of population responses to an increasingly changing environment.This research was supported by FCT (Portuguese Foundation for Science and Technology), through a PhD grant attributed to D. Crespo (SFRH/BD/80252/2011), a post-doc grant attributed to S. Leston (SFRH/BPD/91828/2012) and M Dolbeth (SFRH/BPD/41117/2007) and BIOCHANGED project (PTDC/MAR/111901/2009), subsidized by the European Social Fund and MCTES (Ministério da Ciência, Tecnologia e Ensino Superior) National Funds, through the POPH (Human Potential Operational Programme), QREN (National Strategic Reference Framework) and COMPETE (Programa Operacional Factores de Competitividade).info:eu-repo/semantics/publishedVersio

The role of organisms in hyporheic processes : gaps in current knowledge, needs for future research and applications

Fifty years after the hyporheic zone was first defined (Orghidan, 1959), there are still gaps in the knowledge regarding the role of biodiversity in hyporheic processes. First, some methodological questions remained unanswered regarding the interactions between biodiversity and physical processes, both for the study of habitat characteristics and interactions at different scales. Furthermore, many questions remain to be addressed to help inform our understanding of invertebrate community dynamics, especially regarding the trophic niches of organisms, the functional groups present within sediment, and their temporal changes. Understanding microbial community dynamics would require investigations about their relationship with the physical characteristics of the sediment, their diversity, their relationship with metabolic pathways, their inter- actions with invertebrates, and their response to environmental stress. Another fundamental research question is that of the importance of the hyporheic zone in the global metabolism of the river, which must be explored in relation to organic matter recycling, the effects of disturbances, and the degradation of contaminants. Finally, the application of this knowledge requires the development of methods for the estimation of hydro- logical exchanges, especially for the management of sediment clogging, the optimization of self-purification, and the integration of climate change in environmental policies. The development of descriptors of hyporheic zone health and of new metrology is also crucial to include specific targets in water policies for the long-term management of the system and a clear evaluation of restoration strategies