Using watershed characteristics, sediment, and tissue of resident mollusks to identify potential sources of trace elements to streams in a complex agricultural landscape

A global synthesis of ecosystem services provided and disrupted by freshwater bivalve molluscs

Identification of ecosystem services, i.e. the contributions that ecosystems make to human well-being, has proven instrumental in galvanising public and political support for safeguarding biodiversity and its benefits to people. Here we synthesise the global evidence on ecosystem services provided and disrupted by freshwater bivalves, a heterogenous group of >1200 species, including some of the most threatened (in Unionida) and invasive (e.g. Dreissena polymorpha) taxa globally. Our systematic literature review resulted in a data set of 904 records from 69 countries relating to 24 classes of provisioning (N = 189), cultural (N = 491) and regulating (N = 224) services following the Common International Classification of Ecosystem Services (CICES). Prominent ecosystem services included (i) the provisioning of food, materials and medicinal products, (ii) knowledge acquisition (e.g. on water quality, past environments and historical societies), ornamental and other cultural contributions, and (iii) the filtration, sequestration, storage and/or transformation of biological and physico-chemical water properties. About 9% of records provided evidence for the disruption rather than provision of ecosystem services. Synergies and trade-offs of ecosystem services were observed. For instance, water filtration by freshwater bivalves can be beneficial for the cultural service 'biomonitoring', while negatively or positively affecting food consumption or human recreation. Our evidence base spanned a total of 91 genera and 191 species, dominated by Unionida (55% of records, 76% of species), Veneroida (21 and 9%, respectively; mainly Corbicula spp.) and Myoida (20 and 4%, respectively; mainly Dreissena spp.). About one third of records, predominantly from Europe and the Americas, related to species that were non-native to the country of study. The majority of records originated from Asia (35%), with available evidence for 23 CICES classes, as well as Europe (29%) and North America (23%), where research was largely focused on 'biomonitoring'. Whilst the earliest record (from 1949) originated from North America, since 2000, annual output of records has increased rapidly in Asia and Europe. Future research should focus on filling gaps in knowledge in lesser-studied regions, including Africa and South America, and should look to provide a quantitative valuation of the socio-economic costs and benefits of ecosystem services shaped by freshwater bivalves.

Distribution patterns of macroinvertebrate communities in a Chinese floodgate-regulated river and their relationships with river longitudinal connectivity

In this study, the Li River and the middle-lower reaches of the Shaying River in the Shaying River basin were selected for an investigation on the effects of floodgates on macroinvertebrate communities; additionally, the relationships among floodgates, macroinvertebrate communities and river longitudinal connectivity were explored. The Li and Shaying rivers had similar ratios of molluscs and scrapers, but their species compositions were significantly different. The water level fluctuations in the Li River were based on natural hydrological characteristics, and these were very different from the fluctuations in the reaches of the Shaying River that were divided by a serious of floodgates. The effects of floodgates resulted in a reduction in the number of taxa, Shannon-Wiener index, Margalef index, and Fisher index and an increase in the Harrison index. The upper reaches of the Li and Saying rivers had similar macroinvertebrate communities, but these were very different from the lower reaches of the Saying River. The total number of species and the number of aquatic insect species increased with the river connectivity gradient and the variations in the α-diversity and β-diversity indices along reaches confirmed the hypothesis that the longitudinal connectivity of the Shaying River was significantly affected by floodgates. The results of Pearson and PLS tests showed that some plankton variables and physical water parameters could possibly describe how the gradient of river longitudinal connectivity was related to the floodgates in the Shaying River basin. The results of partial correlations showed, even when excluding the effects of water pollution, the protozoa richness and electrical conductivity still had significant influences on the distribution patterns of macroinvertebrate communities. When considering the results of correlation analyses and regression together, these same variables could be used to describe how the gradient of river longitudinal hydrological connectivity is related to floodgates in future studies.

The impact of poultry litter application on sediment chemistry of the Broadkill River estuary system, Delaware

This project examined the impact of long-term poultry litter application on the chemical signatures of As, Cu, Zn, and P in stream sediments of the Broadkill River watershed within the Delmarva Peninsula, a region of intense poultry production. Thirty-seven sediment samples were collected from Broadkill River drainage systems and analyzed for litter-derived elements (As, Cu, Zn, P) and basic soil parameters such as particle size distribution, organic matter, and soluble salts. Results showed that concentrations of elements in stream sediments are approximately log-normally distributed. Spatial variability in concentrations of elements was evident, with most elements increasing in concentration and enrichment from upgradient headwaters to downgradient reaches draining predominantly agricultural areas. Results of correlation analyses showed positive significant correlation among elements; elements were also positively correlated with percent clay and silt in the sediment. Using GIS maps with overlays of hydrology and land use activities, statistical correlations between As, Cu, Zn, and P enrichment factors and land use were examined. Results showed statistically significant relationships between As, Mn, and Zn enrichment factors and residential areas within the watershed, but did not show a statistically significant relationship between element enrichment factors and agricultural land use. Factors that complicate this type of landscape-scale study include the presence of poultry processing plants, impoundments, changes in land use over time, and the influence of tides, all of which can have direct and indirect influences on element mobility.