An official website of the United States government
SUMMARY While the invasive zebra mussel Dreissena polymorpha has rapidly spread throughout the Great Lakes and inland waterways, it is being displaced by the quagga mussel Dreissena bugensis in shallow water habitats. However, zebra mussels remain dominant in areas with higher water velocity. We hypothesized that the persistence of zebra over quagga mussels in habitats with higher water velocity might result from greater rate and strength of byssal thread attachment. We examined whether zebra mussels relative to quagga mussels have: (1) higher byssal thread synthesis rate, (2) lower dislodgment in flow and (3) greater mechanical force required for detachment from substrate. Specifically, we examined byssal thread synthesis rate and dislodgment of both species in response to water velocities of 0, 50, 100 and 180 cm s–1. Byssal thread synthesis rate was significantly higher for zebra than for quagga mussels at all velocities. Dislodgment from the substrate increased for both species with increasing velocity but was significantly lower for zebra than for quagga mussels. We also tested the mechanical force to detach mussels after short (32 h) and long (two and three months) periods of attachment on hard substrate. Detachment force was significantly higher for zebra than for quagga mussels only after short-term attachment. Higher byssal thread synthesis rate in zebra mussels was a likely factor that minimized their dislodgment in flow and increased short-term attachment strength. Differences in byssal thread synthesis rate between the two species might partly account for the ability of zebra mussels to maintain dominance over quagga mussels in habitats with high velocities.
more »
« less
Calcium concentrations in the lower Columbia River, USA , are generally sufficient to support invasive bivalve spread
Abstract Dissolved calcium concentration [Ca2+] is thought to be a major factor limiting the establishment and thus the spread of invasive bivalves such as zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels. We measured [Ca2+] in 168 water samples collected along ~100 river‐km of the lower Columbia River, USA, between June 2018 and March 2020. We found [Ca2+] to range from 13 to 18 mg L−1during summer/fall and 5 to 22 mg L−1during the winter/spring. Previous research indicates that [Ca2+] < 12 mg L−1are likely to limit the establishment and spread of invasive bivalves. Thus, our results indicate that there is sufficient Ca2+in most locations in the lower Columbia River to support the establishment of invasive dreissenid mussels, which could join the already widespread and abundant Asian clam (Corbicula fluminea) as the newest invader to an already heavily invaded Columbia River ecosystem. These new data provide important measurements from a heretofore undersampled region of the Columbia River and have important implications for the spread of invasive bivalves and, by extension, the conservation and management of native species and ecosystems.
more »
« less
- Award ID(s):
- 1639458
- PAR ID:
- 10450165
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- River Research and Applications
- Volume:
- 37
- Issue:
- 6
- ISSN:
- 1535-1459
- Page Range / eLocation ID:
- p. 889-894
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Larix cajanderiforests, which occupy vast regions of Siberia, grow atop and protect carbon‐rich permafrost. Regeneration of these forests has important implications for long‐term feedbacks into the climate system and their regeneration is strongest following stand‐replacing fires. The goal of this project was to assess sources of regeneration limitation inL. cajanderiforests in northeastern Siberia. We focused on (1) regeneration potential of stands varying in tree density and (2) analyzing seedling establishment patterns in relationship to microsite conditions (safe sites) in the landscape. Seed sources were assessed through cone counts and stand surveys in the summers of 2017 and 2018 in 17 matureL. cajanderistands.L. cajanderirecruitment patterns in relationship to safe site availability were assessed in 15 areas, spanning approximately 800 km2along the northern portion of the Kolyma River (69.5477° N, 161.3641° E). Density of trees in a stand was negatively related to the number of cones that the average tree produced and stands of moderate density produced more cones per area than either high‐ or low‐density stands.L. cajanderiseedling establishment was facilitated by safe sites in the landscape. We discovered strong evidence that safe sites are considerably more important for seedling establishment in lowland sites than upland areas. The biological explanation for this pattern is presently unknown; however, we hypothesize this pattern is driven by persistently wet (marshy) soils in some lowland sites as a limiter of seedling establishment. Overall, these data suggest the potential for complex linkages between forest density, propagule availability, fire, safe sight colonization, and seedling establishment that may regulate long‐term dynamics in the understudiedL. cajanderiforests of the Siberian Arctic.more » « less
-
Urban runoff is a significant source of pollutants, including incidental and engineered nanoparticles, to receiving surface waters. The aim of this study is to investigate the impact of urbanization on the concentrations of TiO 2 engineered particles in urban surface waters. The study area boundaries are limited to the Lower Saluda and Nicholas Creek-Broad River from upstream, and outlet of upper Congaree River in Columbia, South Carolina, United States from downstream. This sampling area captures a significant footprint of the urban area of the city of Columbia. Water samples were collected daily from four sites during two rain events. All samples were analyzed for total metal concentrations following acid digestion and for particle number concentration and elemental composition using single particle-inductively coupled plasma-time of flight-mass spectrometry (SP-ICP-TOF-MS). The Ti/Nb ratios in the Broad and Congaree River samples are generally higher than those of natural background ratios, indicating contamination of these two rivers with anthropogenic Ti-bearing particles. Clustering of multi-metal nanoparticles (mmNPs) demonstrated that Ti-bearing particles are distributed mainly among three clusters, FeTiMn, AlSiFe, and TiMnFe, which are typical of naturally occurring iron oxide, clay, and titanium oxide particles, indicating the absence of significant number of anthropogenic multi-element Ti-bearing particles. Thus, anthropogenic Ti-bearing particles are attributed to single-metal particles; that is pure TiO 2 particles. The total concentration of anthropogenic TiO 2 in the rivers was determined by mass balance calculation using bulk titanium concentration and increases in Ti/Nb above the natural background ratio. The concentration of anthropogenic TiO 2 increases following the order 0 to 24 μg L −1 in the Lower Saluda River <0 to 663 μg L −1 in the Broad River <43 to 1051 μg L −1 in Congaree River at Cayce <58 to 5050 μg L −1 in the Congaree River at Columbia. The concentration of anthropogenic TiO 2 increases with increases in urban runoff. The source of anthropogenic TiO 2 is attributed to diffuse urban runoff. This study demonstrates that diffuse urban runoff results in high concentrations of TiO 2 particles in urban surface waters during and following rainfall events which may pose increased risks to aquatic organisms during these episodic events.more » « less
-
Abstract The transport of Ca2+across membranes precedes the fusion and fission of various lipid bilayers. Yeast vacuoles under hyperosmotic stress become fragmented through fission events that requires the release of Ca2+stores through the TRP channel Yvc1. This requires the phosphorylation of phosphatidylinositol‐3‐phosphate (PI3P) by the PI3P‐5‐kinase Fab1 to produce transient PI(3,5)P2pools. Ca2+is also released during vacuole fusion upontrans‐SNARE complex assembly, however, its role remains unclear. The effect of PI(3,5)P2on Ca2+flux during fusion was independent of Yvc1. Here, we show that while low levels of PI(3,5)P2were required for Ca2+uptake into the vacuole, increased concentrations abolished Ca2+efflux. This was as shown by the addition of exogenous dioctanoyl PI(3,5)P2or increased endogenous production of by the hyperactivefab1T2250Amutant. In contrast, the lack of PI(3,5)P2on vacuoles from the kinase deadfab1EEEmutant showed delayed and decreased Ca2+uptake. The effects of PI(3,5)P2were linked to the Ca2+pump Pmc1, as its deletion rendered vacuoles resistant to the effects of excess PI(3,5)P2. Experiments with Verapamil inhibited Ca2+uptake when added at the start of the assay, while adding it after Ca2+had been taken up resulted in the rapid expulsion of Ca2+. Vacuoles lacking both Pmc1 and the H+/Ca2+exchanger Vcx1 lacked the ability to take up Ca2+and instead expelled it upon the addition of ATP. Together these data suggest that a balance of efflux and uptake compete during the fusion pathway and that the levels of PI(3,5)P2can modulate which path predominates.more » « less
-
Abstract The West Pacific Warm Pool (WPWP)'s response to increasedpCO2during the Pliocene is a key model validation target. Different temperature proxies show different trends: The foraminiferal Mg/Ca sea surface temperature (SST) record shows Pliocene WPWP temperatures ~1.2°C cooler than today (Wara et al., 2005,https://doi.org/10.1126/science.1112596), whereas a TEX86study finds a cooling trend and claims the Pliocene WPWP was warmer than today (Zhang et al., 2014,https://doi.org/10.1126/science.1246172). We focus on understanding biases in Mg/Ca data as the best way to constrain the temperature of the Pliocene WPWP. The strongest nonthermal controls on foraminiferal Mg/Ca are Mg/Ca of seawater and dissolution. Dissolution, which imparts a cool bias to Mg/Ca temperatures, depends on Δ[CO32−], the difference from the carbonate ion concentration needed for calcite saturation. Thus, Pliocene proxy discrepancies might stem from varying Δ[CO32−] over time. To constrain the effect of changing dissolution on the Mg/Ca data, we collected benthic foraminiferal B/Ca data (a proxy for Δ[CO32−]) from the WPWP spanning 0–5.5 Ma. We find no long‐term trend in Δ[CO32−], but variations above and below the threshold of foraminiferal dissolution yield an ~0.4°C cold bias when averaged over the middle to early Pliocene. Changes in seawater Mg/Ca create an ~0.6°C cold bias in the Pliocene Mg/Ca data. After accounting for these biases, we find that the Pliocene WPWP was ~0.1°C cooler than the late Holocene, ranging from −0.5°C to +0.5°C including all uncertainties. Our reconstruction shows a much lower east‐west temperature gradient in the Pliocene tropical Pacific than today, supporting a permanent El Niño‐like “El Padre” state.more » « less
