More Like this

1. The importance of oxbow lakes in the floodplain storage of pollutants

   https://doi.org/10.1130/G49427.1  

   Thomas, Summer-Solstice; Constantine, José Antonio; Dethier, David; Thoman, John W; Racela, Jason; Blau, Emmett; Landis, Joshua D (December 2021, Geology)

   Abstract Oxbow lakes are important stores for fine-grained sediment, which potentially makes them critical sinks for sediment-associated pollutants. We leverage an exhaustive public archive of coring data, supplemented by our data collection, to provide a quantitative assessment of the role of oxbows as off-channel sinks. We investigated loading trends of sediment-sorbed polychlorinated biphenyls (PCBs) within oxbows of the Housatonic River, an actively meandering river in western Massachusetts, USA. Our results reveal the efficiency of oxbows as sinks, with average PCB concentrations (14.8 ppm) that are nearly twice that of the surrounding floodplain (7.56 ppm). Even though the 5.83 km2 floodplain is the largest sink of PCB-laden material, storing as much as 14.1 t of PCBs or 2.42 g m−2, oxbows store more than 20% of all PCBs (3.63 t of PCBs or 11.2 g m−2) while making up just over 5% of the floodplain surface area. Nearly 85% of the oxbow storage of PCBs occurs within the first 50 m of floodplain, making clear the significance of regular oxbow production to the off-channel storage of sediment-associated pollutants. 

   more » « less
2. Role of ecological interactions in saltmarsh geomorphic processes

   https://doi.org/10.3354/meps13554  

   Williams, BL; Johnson, DS (January 2021, Marine Ecology Progress Series)

   null (Ed.)

   Accelerated sea-level rise poses a significant threat to coastal habitats, such as salt marshes, which provide critical ecosystem services. Persistence of salt marshes with rising sea levels relies, in part, on vertical accretion. Ecogeomorphic models emphasize the role of plant production in vertical accretion via sediment trapping and belowground organic matter contribution. Thus, changes in plant production can influence saltmarsh persistence with sea-level rise. However, models of marsh accretion do not consider animal-mediated changes in plant production. We tested how 2 marsh crabs, Minuca pugnax and Sesarma reticulatum , which have contrasting effects (facilitation vs. herbivory) on Spartina alterniflora production, may indirectly influence sediment deposition and belowground production, through observational surveys and field manipulation. Minuca facilitated Spartina biomass in some marshes, but not sediment deposition, and had no effect on belowground organic matter contribution, suggesting that in isolation, Minuca has little indirect impact on saltmarsh geomorphic processes. Sesarma reduced Spartina biomass; however, sediment deposition increased, contrary to ecogeomorphic models, likely due to sediment resuspension by Minuca . When Minuca and Sesarma co-occur, the effect on Spartina production and sediment deposition depended on the amount of grazing. When Sesarma grazing is low, Minuca facilitates Spartina growth and mitigates the effect of grazing. However, when Sesarma grazing is high and vegetation is removed, Minuca can resuspend sediment through bioturbation, suggesting the net effect of these species may depend on their relative abundance. This study demonstrates that the effects of plant-animal interactions on marsh resilience against sea-level rise are context dependent. 

   more » « less
3. The Impact of Polychlorinated Biphenyls on the Development of Zebrafish (Danio rerio)

   https://doi.org/10.3390/biomedicines12092068  

   Moma, Megan; Lee, Abi; Olson, M Brady; Lemkau, Karin L; Cooper, W James (September 2024, Biomedicines)

   Polychlorinated biphenyls (PCBs) are a group of 209 highly stable molecules that were used extensively in industry. Although their commercial use ceased in 1979, they are still present in many aquatic ecosystems due to improper disposal, oceanic currents, atmospheric deposition, and hydrophobic nature. PCBs pose a significant and ongoing threat to the development and sustainability of aquatic organisms. In areas with PCB exposure high mortality rates of organisms inhabiting them are still seen today, posing a significant threat to local species. Zebrafish were exposed to a standard PCB mixture (Aroclor 1254) for the first 5 days post fertilization, as there is a gap in knowledge during this important developmental period for fish (i.e., organization of the body). This PCB mixture was formally available commercially and has a high prevalence in PCB-contaminated sites. We tested for the effects of PCB dosage (control (embryo water only; 0 mg/L), methanol (solvent control; 0 mg/L); PCB 1 (0.125 mg/L), PCB 2 (0.25 mg/L), PCB 3 (0.35 mg/L), and PCB 4 (0.40 mg/L)) on zebrafish survival, rate of metamorphosis, feeding efficiency, and growth. We found significant, dose-dependent effects of PCB exposure on mortality, feeding efficiency, and growth, but no clear effect of PCBs on the rate of zebrafish metamorphosis. We identified a concentration in which there were no observable effects (NOEC), PCB concentration above the NOEC had a significant impact on life-critical processes. This can further inform local management decisions in environments experiencing PCB contamination. 

   more » « less
4. Freshwater mussels alter fish distributions through habitat modifications at fine spatial scales

   Hopper, G.W.; DuBose, T.P.; Gido, K.B; Vaughn, C.C. (December 2019, Freshwater science)

   Aggregations of freshwater mussels create patches that can benefit other organisms through direct habitat alterations or indirect stimulation of trophic resources via nutrient excretion and biodeposition. Spent shells and the shells of living mussels add complexity to benthic environments by providing shelter from predators and increasing habitat heterogeneity. Combined, these factors can increase primary productivity and macroinvertebrate abundance in patches where mussel biomass is high, providing valuable subsidies for some fishes and influencing their distributions. We performed a 12-wk field experiment to test whether fish distributions within mussel beds were most influenced by the presence of subsidies associated with live mussels or the biogenic habitat of shells. We used remote underwater video recordings to quantify fish occurrences at fifty 0.25-m2 experimental enclosures stocked with either live mussels (2-species assemblages), sham mussels (shells filled with sand), or sediment only. The biomass of algae and benthic macroinvertebrates increased over time but were uninfluenced by treatment. We detected more fish in live mussel and sham treatments than in the sediment-only treatment but found no difference between live mussel and sham treatments. Thus, habitat provided by mussel shells may be the primary benefit to fishes that co-occur with mussels. Increased spatiotemporal overlap between fish and mussels might strengthen ecosystem effects, such as nutrient cycling, and the role of both fish and mussels in freshwater ecosystems 

   more » « less
5. Repetitive desiccation events weaken a salt marsh mutualism

   https://doi.org/10.1111/1365-2745.13178  

   Derksen‐Hooijberg, Marlous; Angelini, Christine; Hoogveld, Jasper_R_H; Lamers, Leon_P_M; Borst, Annieke; Smolders, Alfons; Harpenslager, Sarah_Fay; Govers, Laura_L; van_der_Heide, Tjisse; Randall_Hughes, ed., A. (April 2019, Journal of Ecology)

   Abstract Salt marshes suffered large‐scale degradation in recent decades. Extreme events such as hot and dry spells contributed significantly to this, and are predicted to increase not only in intensity, but also in frequency under future climate scenarios. Such repetitive extreme events may generate cumulative effects on ecosystem resilience. It is therefore important to elucidate how marsh vegetation responds to repetitive stress, and whether changes in key species interactions can modulate vegetation resilience.In this study, we investigated how moderate but repetitive desiccation events, caused by the combined effects of drought and high temperatures, affect cordgrass (Spartina alterniflora), the dominant habitat‐forming grass in southeasternUSsalt marshes. In a 4‐month field experiment, we simulated four consecutive desiccation events by periodically excluding tidal flooding and rainfall, while raising temperature. We crossed this desiccation treatment with the presence/absence of ribbed mussels (Geukensia demissa) – a mutualist of cordgrass known to enhance its desiccation resilience – and with grazing pressure by the marsh periwinkle (Littoraria irrorata) that is known to suppress cordgrass’ desiccation resilience.We found that each subsequent desiccation event deteriorated sediment porewater conditions, resulting in high salinity (53 ppt), low pH‐levels (3.7) and increased porewater Al and Fe concentrations (≈800 μmol/L and ≈1,500 μmol/L) upon rewetting. No effects on porewater chemistry were found as a result of snail grazing, while ribbed mussels strongly mitigated desiccation effects almost to control levels and increased cordgrass biomass by approximately 128%. Importantly, although cordgrass generally appeared healthy above‐ground at the end of the experiment, we found clear negative responses of the repetitive desiccation treatment on cordgrass below‐ground biomass, on proline (osmolyte) levels in shoots and on the number of tillers (−40%), regardless of mussel and/or snail presence.Synthesis. Even though the mutualism with mussels strongly mitigated chemical effects in the sediment porewater throughout the experiment, mussels could not buffer the adverse ecophysiological effects observed in cordgrass tissue. Our results therefore suggest that although mussels may alleviate desiccation stress, the predicted increased frequency and intensity of hot dry spells may eventually affect saltmarsh resilience by stressing the mutualism beyond its buffering capacity. 

   more » « less