Are structural and functional endpoints of soil communities similarly affected by metal mixtures? - A terrestrial model ecosystem approach.

Soils are habitat to a variety of flora and fauna in a linked ecosystem which provides essential ecosystem services. In soil, metals can accumulate at high concentrations, because of anthropogenic activities, leading to toxic effects, threatening the ecosystem and the services it provides. In most real-world contamination scenarios, metals occur as complex mixtures which can interact and produce different toxicity than predicted from individual metal data. Current regulatory guidelines are based on single species responses to individual metals and ignore indirect effects inherent to the inter-linked nature of ecosystems. Also, the evaluation of anthropogenic impacts to the soil communities is usually measured through structural endpoints (e.g. abundance) disregarding functional measurements (e.g. organic matter decomposition rates), which are often seen as tightly related, and thus, similarly affected. In this study we tested three mixture ratios of five metal oxides (lead, copper, nickel, zinc, cobalt) at three dose levels (Low, Med, High) in a terrestrial model ecosystem experiment and measured structural and functional endpoints. Exposure to metal mixtures for 16 weeks did not affect the microarthropod community, but produced severe effects on soil microbial activity (PNR and DHA) reducing activity below 50% compared to control levels, in all dosed treatments. Metal contamination also significantly affected feeding activity and organic matter decomposition, but effects were not as pronounced as on microbial activity. Data suggest that, in the risk assessment of metals and their mixtures, effects on ecosystem structure and functions must be considered to provide adequate environmental protection.

The impact of the sea anemone Actinothoe sphyrodeta on Mytilus galloprovincialis mussel cultivation (Galicia, Spain).

Marine mussel aggregations act as a substratum and refuge for many fouling species. Mussel cultivation in Galicia, Spain, is carried out on hanging ropes in subtidal systems. The fauna associated with this cultivation includes a large number of invertebrates that compete for space or food with the mussels, or use their clusters as a refuge from predators or water turbulence. Outbreaks of the epibiont anemone Actinothoe sphyrodeta have been reported in cultivated Galician mussels since 2013, but their impact has not been investigated rigorously. Here, the temporal and spatial variability of Actinothoe sphyrodeta on mussel shells throughout one year is presented. Sampling of mussel size, weight and byssus attachment strength allowed mussel tenacity (attachment strength relative to size) to be calculated. A higher presence of Actinothoe sphyrodeta correlated with lower mussel tenacity and greater biomass losses, suggesting that this species could be an economically important biofouling component.