Flow regime in a restored wetland determines trophic links and species composition in the aquatic macroinvertebrate community

Composition and sources of sediment organic matter in a western Iberian salt marsh: Developing a novel prediction model of the bromine sedimentary pool

Salt marshes are sensitive highly productive habitats crucial for carbon cycling. This study presents a comprehensive analysis of organic geochemical indicators and geochronology in the Mira salt marsh (SW Portugal) over eight centuries. The closely intertwined carbon and bromine (Br) biogeochemical cycles in these environments can influence the fluxes of volatile compounds such as ozone-depleting methyl bromide, emphasizing the importance of understanding sediment organic matter (OM) origin, budget, and composition in salt marshes. To characterize the strong Br-OM relationship, we used n-alkane signatures, bulk elemental data (total carbon, total nitrogen, Corg/Nat ratio), and stable isotopes (δ15N, δ13C) from a sediment core. Findings revealed a mixed composition of terrestrial and marine OM, posing challenges in distinguishing ex situ higher plant sources from in situ production by marsh vegetation. n-Alkanes (C15 to C31) were found in all the sediment samples, predominantly C25-C29. Changes in their presence were linked to marsh succession, evolving from a vegetation-free tidal flat to a C3 halophyte-dominated high marsh ecosystem. Despite the area's low industrial and population impact, regulation of water flow through the dam affected the balance between continental and marine waters. This study aimed to create a cost-effective predictive model for total Br, enhancing paleoclimatic studies using sedimentary samples. The n-alkane model had limited resolution, but an alternative infrared (IR) spectroscopy-based model, requiring less time and smaller sample sizes, was developed. Combining FT-IR spectra with statistical analysis enabled the creation of a reliable total Br concentration prediction model (mean absolute error = 14.39). These findings have implications for controlling Br enrichment in marsh environments and can be applied in various coastal wetlands with different mineralogical and organic characteristics.

Dissimilar behavioral and spatial avoidance responses by shrimps from tropical and temperate environments exposed to copper

Behavioral changes associated with exposure to pollutants represent the earliest response for organisms confronted by perceivable chemical signals. This study was carried out with the objective of evaluating behavioral responses associated with different scenarios of exposure to pollutants (non-forced vs forced) in two shrimp species (Penaeus vannamei and Palaemon varians), representative of different latitudes and using copper as a model contaminant. The effects on locomotion were evaluated by exposing the shrimps to a range of copper concentrations (0, 0.5, 5, 50, and 250 µg/L) in the forced scenario. After exposure, the movement patterns for each shrimp were recorded and used to estimate changes in the shrimps' locomotion. For the non-forced scenario, the avoidance response was assessed by placing shrimps in a multi-compartment system where they were able to move freely along a gradient of copper (0, 0.5, 5, 50, and 250 µg/L). In terms of locomotion, an opposite trend was observed between the species: movements were significantly reduced in P. varians with concentrations above 50 µg/L, while hyperactivity was observed for P. vannamei. When exposed to a gradient of copper in the multi-compartment system, both species significantly avoided the highest concentrations of copper, although the repellence of copper was stronger for P. vannamei. In summary, both species of shrimps were able to recognize and avoid copper; however, in terms of locomotion, they showed an opposite behavioral reaction. These results show that a contamination event can have different behavioral outcomes depending on the species and complementing forced and non-forced exposure with species-specific information can be helpful to characterize and predict the effects of contaminants at higher biological levels.

Isotopic niche provides an insight into the ecology of a symbiont during its geographic expansion

The study of the recent colonization of a symbiont and its interaction with host communities in new locations is an opportunity to understand how they interact. The use of isotopic ratios in trophic ecology can provide measurements of a species’ isotopic niche, as well as knowledge about how the isotopic niches between symbiont and host species overlap. Stable isotope measurements were used to assess the sources of carbon assimilated by the host species (the bivalves Mytilus galloprovincialis and Scrobicularia plana) and their associated symbiont pea crab Afropinnotheres monodi, which occurs within these bivalves’ mantle cavities. The mixing model estimates suggest that all of them assimilate carbon from similar sources, particularly from pseudofaeces and particulate organic matter in this symbiotic system based on filter feeding. The symbiotic species occupy comparable trophic levels and its association seems to be commensal or parasitic depending on the duration of such association. The pea crab A. monodi reflects a sex-specific diet, where males are more generalist than the soft females because the latter’s habitat is restricted to the host bivalve. The high isotopic overlap between soft females and M. galloprovincialis may reflect a good commensal relationship with the host.

Freshwater release into estuarine wetlands changes the structure of benthic invertebrate assemblages: A case study from the Yellow River Delta

Freshwater releases to wetlands degraded by excessive soil salinity in estuarine areas have been widely used to restore vegetation and maintain biodiversity of the wetland ecosystems. However, freshwater release also alters the physical and chemical properties of the water body, having a profound impact on the ecology of restored wetland ecosystems. In this study, physical and chemical parameters of water quality were compared between restored and non-restored tidal wetlands after 10 years of freshwater release in the Yellow River estuary. In addition, benthic invertebrates were used as bioindicators to reveal the effects of freshwater release on estuarine wetland ecology. The results showed that there was a significant difference in salinity between restored and non-restored wetlands (P < 0.05), which led to differences in the composition of benthic invertebrate communities (ANOSIM P < 0.001). The primary components of benthic invertebrate community were insects in restored wetlands, and in non-restored tidal wetlands the primary components were annelids, crustaceans, and gastropods. More long-term monitoring research of the impacts of freshwater introduction on degraded estuarine wetland ecosystems is needed to fully assess consequences.