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Invasive bivalves can drastically alter freshwater ecosystems and affect ecosystem services, but they can be influenced by external factors including calcium concentrations. When a common road salt, calcium chloride (CaCl2), enters freshwater ecosystems, it may be toxic to organisms or facilitate bivalves by serving as a calcium source. Therefore, CaCl2 could benefit invasive mollusks tolerant to chloride that require calcium to grow. We used mesocosms to investigate the impacts of CaCl2 (35–187 mg Ca²⁺ L⁻¹) and invasive bivalves (Asian clams, Corbicula fluminea; zebra mussels, Dreissena polymorpha) on a native lake food web. We hypothesized that invasive bivalves facilitate benthic algae because they reduce phytoplankton and excrete waste. These changes in primary producers would subsequently impact consumers. We also hypothesized that low to moderate CaCl2 concentrations promote the survival, growth, and reproduction of native and invasive mollusks, while causing few toxic effects. If so, we hypothesized that invaded communities exposed to CaCl2 experience stronger impacts from the invasive bivalves. We found that invasive bivalves decreased phytoplankton, which led to decreases in periphyton, zooplankton, and native clams. They caused increases in filamentous algae and isopods. While zebra mussels survived poorly in all treatments, moderate concentrations of CaCl2 substantially reduced Asian clams, which reduced their community effects. Our highest CaCl2 treatments also reduced zooplankton densities. Thus, while freshwater salinization from road salts poses a concern, we observed no indication that CaCl2 road salt will benefit Asian clams and zebra mussels. However, the community-wide consequences from Asian clams at low CaCl2 emphasize the extensive effects that invasive bivalves can have on freshwater communities and the immense concern surrounding their invasions.
Calcium chloride pollution mitigates the negative effects
of an invasive clam
Kayla D. Coldsnow .William D. Hintz .Matthew S. Schuler .
Aaron B. Stoler .Rick A. Relyea
Received: 20 December 2019 / Accepted: 19 December 2020 / Published online: 2 January 2021
ÓThis is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2021
Abstract Invasive bivalves can drastically alter
freshwater ecosystems and affect ecosystem services,
but they can be influenced by external factors includ-
ing calcium concentrations. When a common road
salt, calcium chloride (CaCl
), enters freshwater
ecosystems, it may be toxic to organisms or facilitate
bivalves by serving as a calcium source. Therefore,
could benefit invasive mollusks tolerant to
chloride that require calcium to grow. We used
mesocosms to investigate the impacts of CaCl
(35–187 mg Ca
) and invasive bivalves (Asian
clams, Corbicula fluminea; zebra mussels, Dreissena
polymorpha) on a native lake food web. We hypoth-
esized that invasive bivalves facilitate benthic algae
because they reduce phytoplankton and excrete waste.
These changes in primary producers would subse-
quently impact consumers. We also hypothesized that
low to moderate CaCl
concentrations promote the
survival, growth, and reproduction of native and
invasive mollusks, while causing few toxic effects. If
so, we hypothesized that invaded communities
exposed to CaCl
experience stronger impacts from
the invasive bivalves. We found that invasive bivalves
Supplementary Information The online version contains
supplementary material available at
K. D. Coldsnow (&)W. D. Hintz
M. S. Schuler A. B. Stoler R. A. Relyea
Department of Biological Sciences, Darrin Fresh Water
Institute, Rensselaer Polytechnic Institute, 110 8th St.,
Troy, NY 12180, USA
Present Address:
K. D. Coldsnow
Office of Pesticide Programs, Health Effects Division,
U.S. Environmental Protection Agency,
Research Triangle Park, NC, USA
Present Address:
W. D. Hintz
Department of Environmental Sciences and Lake Erie
Center, University of Toledo, Oregon,
Present Address:
M. S. Schuler
Department of Biology, Montclair State University,
Montclair, NJ, USA
Present Address:
A. B. Stoler
School of Natural Sciences and Mathematics, Stockton
University, Galloway, NJ, USA
Biol Invasions (2021) 23:1349–1366,-volV)(0123456789().,-volV)
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... However, most studies are single-organisms toxicity studies. A few community studies have investigated low concentrations and found few biotic effects (Coldsnow et al., 2021;Schuler et al., 2017), but moderate to high concentrations of these alternatives need to be examined to fully understand their effects on freshwater biota. In addition to biotic consequences, there are also abiotic consequences, such as changes in dissolved oxygen, pH, and nutrient concentrations Terry et al., 2020). ...
... Calcium is vital to the shells of many organisms and in the laboratory, low concentrations of CaCl 2 (relative to many road salt experiments; <130 mg Cl − /L) increased the growth and survival of bivalve species (Davis et al., 2015;Ferreira-Rodríguez et al., 2017). However in another mesocosm experiment, low to medium concentrations of CaCl 2 (30-260 mg Cl − /L) did not benefit any organisms in the community (Coldsnow et al., 2021), which is similar to what we found at our medium concentration. Despite the importance of magnesium in the carapace of ostracods, they did not increase when exposed to MgCl 2 . ...
... In addition, high NaCl (1000 mg Cl − /L) decreased amphipod abundance in a community study . While no long-term study has investigated high concentrations of the alternatives, one study that investigated low concentrations of MgCl 2 (50 and 100 mg Cl − /L) actually found an increase in amphipod abundance and one that investigated low to medium concentrations of CaCl 2 (30-260 mg Cl − /L) found no effect on amphipod abundance (Coldsnow et al., 2021). We also found no effects at medium concentrations. ...
Because of environmental and societal concerns, new strategies are being developed to mitigate the effects of road salt. These include new deicers that are alternatives to or mixtures with the most common road salt, sodium chloride (NaCl), improved techniques and equipment, and biotic mitigation methods. Using outdoor mesocosms, we investigated the impacts of NaCl and two common alternatives, magnesium chloride (MgCl2) and calcium chloride (CaCl2) on freshwater communities. We also investigated the mitigation ability of a common macrophyte, Elodea. We hypothesized that road salt exposure reduces filamentous algae, zooplankton, and macrocrustaceans, but results in increases in phytoplankton and gastropods. We also hypothesized that MgCl2 is the most toxic salt to communities, followed by CaCl2, and then NaCl. Lastly, we hypothesized that macrophytes mitigate some of the effects of road salt, specifically the effects on primary producers. We found that all three salts reduced filamentous algal biomass and amphipod abundance, but only MgCl2 reduced Elodea biomass. MgCl2 had the largest and longest lasting effects on zooplankton, specifically cladocerans and copepods, which resulted in a significant increase in phytoplankton and rotifers. CaCl2 increased ostracods and decreased snail abundance, but NaCl increased snail abundance. Lastly, while we did not find many interactions between road salt and macrophyte treatments, macrophytes did counteract many of the salt effects on producers, leading to decreased phytoplankton, increased filamentous algae, and altered abiotic responses. Thus, at similar chloride concentrations, NaCl alternatives, specifically MgCl2, are not safer for aquatic ecosystems and more research is needed to find safer road management strategies to protect freshwater ecosystems.
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Salinization of coastal freshwater ecosystems is already occurring in some regions of the world. This phenomenon raises serious concerns on the protection of coastal freshwater ecosystems, since many of them support and shelter a large number of species and are considered hotspots of biodiversity. This work intended to assess the adverse effects that salinization, caused by the intrusion of seawater (SW), may pose to freshwater organisms. In this study, three specific goals were addressed: (i) to assess if sodium chloride (NaCl) may be used as a surrogate of natural SW at early-stages of risk assessment; (ii) to identify the most sensitive freshwater species to salinity NaCl; and (iii) to determine if increased tolerance to salinity may be acquired after multigenerational exposure to low levels of salinization (induced with NaCl). A total of 12 standard monospecific bioassays were carried out by exposing organisms from different taxonomic groups (Cyano-bacteria: one species, Tracheophyta: two species, Rotifera: one species, Arthropoda: two species and Mollusca: one species) to a series of concentrations of NaCl (ranging from 0.95 to 22.8 mS cm–1) or dilutions of SW (ranging from 1.70 to 52.3 mS cm²¹). In general, NaCl exerted similar or higher toxicity than SW, both at lethal and sublethal levels, suggesting that it may be proposed as a protective surrogate of SW for first tiers of salinization risk assessment. Among all tested species, the cyanobacterium Cylindrospermopsis raciborskii, the daphnid Daphnia longispina and the rotifer Brachionus plicatilis were the most sensitive taxa to salinization (EC50 4.38 mS cm²¹). Given their position at the basis of the food web, it is suggested that small increments of salinity may be enough to induce structural changes in freshwater communities or induce changes in trophic relations. No clear evidences of increased tolerance after multigenerational exposure to low levels of salinity were found. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’. © 2018 The Author(s) Published by the Royal Society. All rights reserved.
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Road salts are altering and mobilizing heavy metals away from roadside soils, potentially into freshwater systems. Despite numerous studies investigating the mobilization of heavy metals by road salts, few studies have investigated (a) the movement rate and fate of heavy metals mobilized by road salts, (b) how road salts alter the bioavailable fraction of heavy metals, and (c) how road salts and heavy metals interact to affect freshwater organisms or human health. In this article, we discuss the consequences of increased concentrations of heavy metals and road salts, examine the mechanisms of heavy-metal mobilization, and highlight areas for future research. Future studies should investigate how metals and road salts alter ecosystem function and ecosystem services in freshwater habitats. Finally, increased research efforts will help assess whether the fate of heavy metals mobilized by road salts increases risks to human health by contaminating drinking water and water used for agriculture.
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Salt pollution and human-accelerated weathering are shifting the chemical composition of major ions in fresh water and increasing salinization and alkalinization across North America. We propose a concept, the freshwater salinization syndrome, which links salinization and alkalinization processes. This syndrome manifests as concurrent trends in specific conductance, pH, alkalinity, and base cations. Although individual trends can vary in strength, changes in salinization and alkalinization have affected 37% and 90%, respectively, of the drainage area of the contiguous United States over the past century. Across 232 United States Geological Survey (USGS) monitoring sites, 66% of stream and river sites showed a statistical increase in pH, which often began decades before acid rain regulations. The syndrome is most prominent in the densely populated eastern and midwestern United States, where salinity and alkalinity have increased most rapidly. The syndrome is caused by salt pollution (e.g., road deicers, irrigation runoff, sewage, potash), accelerated weathering and soil cation exchange, mining and resource extraction, and the presence of easily weathered minerals used in agriculture (lime) and urbanization (concrete). Increasing salts with strong bases and carbonates elevate acid neutralizing capacity and pH, and increasing sodium from salt pollution eventually displaces base cations on soil exchange sites, which further increases pH and alkalinization. Symptoms of the syndrome can include: infrastructure corrosion, contaminant mobilization, and variations in coastal ocean acidification caused by increasingly alkaline river inputs. Unless regulated and managed, the freshwater salinization syndrome can have significant impacts on ecosystem services such as safe drinking water, contaminant retention, and biodiversity.
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Human-dominated land uses can increase transport of major ions in streams due to the combination of human-accelerated weathering and anthropogenic salts. Calcium, magnesium, sodium, alkalinity, and hardness significantly increased in the drinking water supply for Baltimore, Maryland over almost 50 years (p < 0.05) coinciding with regional urbanization. Across a nearby land use gradient at the Baltimore Long-Term Ecological Research (LTER) site, there were significant increases in concentrations of dissolved inorganic carbon (DIC), Ca²⁺, Mg²⁺, Na⁺, and Si and pH with increasing impervious surfaces in 9 streams monitored bi-weekly over a 3–4 year period (p < 0.05). Base cations in urban streams were up to 60 times greater than forest and agricultural streams, and elemental ratios suggested road salt and carbonate weathering from impervious surfaces as potential sources. Laboratory weathering experiments with concrete also indicated that impervious surfaces increased pH and DIC with potential to alkalinize urban waters. Ratios of Na⁺ and Cl⁻ suggested that there was enhanced ion exchange in the watersheds from road salts, which could mobilize other base cations from soils to streams. There were significant relationships between Ca²⁺, Mg²⁺, Na⁺, and K⁺ concentrations and Cl⁻, SO4²⁻, NO3⁻ and DIC across land use (p < 0.05), which suggested tight coupling of geochemical cycles. Finally, concentrations of Na⁺, Ca²⁺, Mg²⁺, and pH significantly increased with distance downstream (p < 0.05) along a stream network draining 170 km² of the Baltimore LTER site contributing to river alkalinization. Our results suggest that urbanization may dramatically increase major ions, ionic strength, and pH over decades from headwaters to coastal zones, which can impact integrity of aquatic life, infrastructure, drinking water, and coastal ocean alkalinization.
Humans are altering environments by destroying habitats, introducing species, and releasing pollution. One emergent pollutant is the salinization of freshwater habitats from road deicing salts. Government agencies have set thresholds to protect freshwater ecosystems, yet many exceed these values. The present study investigated the tolerance of Asian clams (Corbicula fluminea), a common invasive bivalve, to the common road salt (sodium chloride, NaCl) and two alternatives (magnesium chloride, MgCl2; calcium chloride, CaCl2). A 4- and 8-d experiment revealed that Asian clams are very salt tolerant. The LC504-destimate was 2,162 mg Cl-/L for MgCl2, 3,554 mg Cl-/L for CaCl2, and > 22,581 mg Cl-/L for NaCl, which were all significantly different (p ≤ 0.05). The LC508-dwere significantly different (p ≤ 0.05) from each other and from the LC504-dand estimated to be 1,769 mg Cl-/L for MgCl2, 2,235 Cl-/L for CaCl2, and 10,069 mg Cl-/L for NaCl. Mortality was accessed using two methods: either no response after exposure or no response after being in fresh water following exposure. For the majority of the LC50s, these methods were not significantly different (p > 0.05). The high salt tolerance of Asian clams is a concern because of their transportation in ballast water between aquatic ecosystems. Furthermore, salt-tolerant organisms may outcompete sensitive organisms in salinized ecosystems, which may alter ecosystem services. This article is protected by copyright. All rights reserved.
Bivalves are ubiquitous members of freshwater ecosystems and responsible for important functions and services. The present paper revises freshwater bivalve diversity, conservation status and threats at the global scale and discusses future research needs and management actions. The diversity patterns are uneven across the globe with hotspots in the interior basin in the United States of America (USA), Central America, Indian subcontinent and Southeast Asia. Freshwater bivalves are affected by multiple threats that vary across the globe; however, pollution and natural system (habitat) modifications being consistently found as the most impacting. Freshwater bivalves are among the most threatened groups in the world with 40% of the species being near threatened, threatened or extinct, and among them the order Unionida is the most endangered. We suggest that global cooperation between scientists, managers, politicians and general public, and application of new technologies (new generation sequencing and remote sensing, among others) will strengthen the quality of studies on the natural history and conservation of freshwater bivalves. Finally, we introduce the articles published in this special issue of Hydrobiologia under the scope of the Second International Meeting on Biology and Conservation of Freshwater Bivalves held in 2015 in Buffalo, New York, USA.