Description: These datasets comprise data obtained during a 42 week-long exposure experiment of Mytilus spp. to two types of microplastics, namely spherical polystyrene (PS) particles and irregular polyvinylchloride (PVC) particles. This data was obtained from January 2018 to January 2019 from juvenile blue mussels with an initial size of 10mm. We recorded growth via shell length. Growth was measured every six weeks already during a three months acclimation period without exposure to microplastics. Mussels were exposed to three concentrations of PS (15, 1500, 15 000 particles/individual/week) and five concentrations of PVC (15, 1500, 15 000, 150 000 and 1 500 000 particles/individual/week) and one group to no particles at all as control.

Description: These datasets comprise data obtained during a 42 week-long exposure experiment of Mytilus spp. to two types of microplastics, namely spherical polystyrene (PS) particles and irregular polyvinylchloride (PVC) particles. This data was obtained from January 2018 to January 2019 from juvenile blue mussels with an initial size of 10mm. We recorded body condition index. Body condition was measured three times, at week 0, week 16 and week 32. At week 0 only one group of mussels not exposed to microplastic particles was measured, at the other two time points mussels were exposed to three concentrations of PS (15, 1500, 15 000 particles/individual/week) and five concentrations of PVC (15, 1500, 15 000, 150 000 and 1 500 000 particles/individual/week) and one group to no particles at all as control.

Description: These datasets comprise data obtained during a 42 week-long exposure experiment of Mytilus spp. to two types of microplastics, namely spherical polystyrene (PS) particles and irregular polyvinylchloride (PVC) particles. This data was obtained from January 2018 to January 2019 from juvenile blue mussels with an initial size of 10mm. Oxidative stress in the form of Malondialdehyde (MDA) concentrations was only measured once at the end of the experiment. Mussels were exposed to three concentrations of PS (15, 1500, 15 000 particles/individual/week) and five concentrations of PVC (15, 1500, 15 000, 150 000 and 1 500 000 particles/individual/week) and one group to no particles at all as control.

Description: These datasets comprise data obtained during a 42 week-long exposure experiment of Mytilus spp. to two types of microplastics, namely spherical polystyrene (PS) particles and irregular polyvinylchloride (PVC) particles. This data was obtained from January 2018 to January 2019 from juvenile blue mussels with an initial size of 10mm. Oxidative stress in the form of Superoxide (SOD) activity was only measured once at the end of the experiment. Mussels were exposed to three concentrations of PS (15, 1500, 15 000 particles/individual/week) and five concentrations of PVC (15, 1500, 15 000, 150 000 and 1 500 000 particles/individual/week) and one group to no particles at all as control.

Description: These datasets comprise data obtained during a 42 week-long exposure experiment of Mytilus spp. to two types of microplastics, namely spherical polystyrene (PS) particles and irregular polyvinylchloride (PVC) particles. This data was obtained from January 2018 to January 2019 from juvenile blue mussels with an initial size of 10mm. We recorded growth via shell length, body condition index, byssus thread production in 24 hours and clearance rate of the food algae R. baltica. Growth was measured every six weeks already during a three months acclimation period without exposure to microplastics, while byssus thread production and clearance rate were measured every six weeks only during microplastic exposure. Body condition index was measured two times, at week 16 and 32, while oxidative stress in the form of Malondialdehyde (MDA) concentrations and Superoxide (SOD) activity was only measured once at the end of the experiment. Mussels were exposed to three concentrations of PS (15, 1500, 15 000 particles/individual/week) and five concentrations of PVC (15, 1500, 15 000, 150 000 and 1 500 000 particles/individual/week) and one group to no particles at all as control.

Description: The blue mussel (Mytilus species complex) is an important ecosystem engineer, and salinity can be a major abiotic driver of mussel functioning in coastal ecosystems. However, little is known about the interactive effects of abiotic drivers and trematode infection. This study investigated the combined effects of salinity and Himasthla elongata and Renicola roscovita metacercarial infections on the filtration capacity, growth, and condition of M. edulis from the Baltic Sea. In a laboratory experiment, groups of infected and uninfected mussels were exposed to a wide range of salinities (6−30, in steps of 3) for 1 mo. Shell growth was found to be positively correlated with salinity and optimal at 18−24 at the end of the experiment, imposed by constraints in shell calcification under lower salinities. Mussel shell growth was not affected by H. elongata infection. While salinity had only a minor effect on tissue dry weight, infected mussels had a significantly lower tissue dry weight than uninfected mussels. Most interestingly, the combination of salinity and trematode infections negatively affected the mussels’ condition indices at lower salinity levels (6 and 9), suggesting that trematode infections are more detrimental to mussels when combined with freshening. A significant positive effect of salinity on mussel filtration was found, with an initial optimum at salinity 18 shifting to 18−24 by the end of the experiment. These findings indicate that salinity and parasite infections act as synergistic stressors for mussels, and enhance the understanding of potential future ecosystem shifts under climate change-induced freshening in coastal waters.

Description: Highlights: • First study to compare microplastic effects over a wide biogeographical range • Comparison between natural inorganic microparticles and plastic microparticles • Significant effects on byssus production, respiration and clearance rates, but small effect sizes • No ecologically relevant difference between impact of plastic and natural inorganic microparticles on Mytilidae Abstract: Microplastics are ubiquitous in the marine environment and studies on their effects on benthic filter feeders at least partly revealed a negative influence. However, it is still unclear whether the effects of microplastics differ from those of natural suspended microparticles, which constitute a common stressor in many coastal environments. We present a series of experiments that compared the effects of six-week exposures of marine mussels to two types of natural particles (red clay and diatom shells) to two types of plastic particles (Polymethyl Methacrylate and Polyvinyl Chloride). Mussels of the family Mytilidae from temperate regions (Japan, Chile, Tasmania) through subtropical (Israel) to tropical environments (Cabo Verde) were exposed to concentrations of 1.5 mg/L, 15 mg/L and 150 mg/L of the respective microparticles. At the end of this period, we found significant effects of suspended particles on respiration rate, byssus production and condition index of the animals. There was no significant effect on clearance rate and survival. Surprisingly, we observed only small differences between the effects of the different types of particles, which suggests that the mussels were generally equally robust towards exposure to variable concentrations of suspended solids regardless of whether they were natural or plastic. We conclude, that microplastics and suspended solids elicit similar effects on the tested response variables, and that both types of microparticles mainly cause acute responses rather than more persistent carry-over effects.

Description: Highlights: • Effects of microplastic on marine biota reflect the quality of experimental research. • The quality of published experiments can be quantified from an “ideal” experiment. • Previously published experiments have significantly deviated from “ideal”. • Implementation of proposed criteria can improve future microplastic experiments. Abstract: This article presents a novel conceptual blueprint for an ‘ideal’, i.e., ecologically relevant, microplastic effect study. The blueprint considers how microplastics should be characterized and applied in laboratory experiments, and how biological responses should be measured to assure unbiased data that reliably reflect the effects of microplastics on aquatic biota. This ‘ideal’ experiment, although practically unachievable, serves as a backdrop to improve specific aspects of experimental research on microplastic effects. In addition, a systematic and quantitative literature review identified and quantified departures of published experiments from the proposed ‘ideal’ design. These departures are related mainly to the experimental design of microplastic effect studies failing to mimic natural environments, and experiments with limited potential to be scaled-up to ecosystem level. To produce a valid and generalizable assessment of the effect of microplastics on biota, a quantitative meta-analysis was performed that incorporated the departure of studies from the ‘ideal’ experiment (a measure of experimental quality) and inverse variance (a measure of the study precision) as weighting coefficients. Greater weights were assigned to experiments with higher quality and/or with lower variance in the response variables. This double-weighting captures jointly the technical quality, ecological relevance and precision of estimates provided in each study. The blueprint and associated meta-analysis provide an improved baseline for the design of ecologically relevant and technically sound experiments to understand the effects of microplastics on single species, populations and, ultimately, entire ecosystems.

Description: Highlights: • Effects of microplastics on Mytilus spp. were assessed over the course of 42 weeks. • Effects were seen even at the lowest MP concentration (15 particles/individual/week). • At the highest PS dose, clearance rates decreased significantly only after 36 weeks. • SOD and MDA concentrations declined as a consequence of exposure to microplastics. Abstract: Microplastics have been found in all compartments of the environment, and numerous life forms are known to take up the anthropogenic particles. Marine filter feeders are particularly susceptible to ingest suspended microplastics, but long-term studies on the potential effects of this uptake are scarce. We exposed juvenile Mytilus spp. to environmentally realistic doses of irregularly shaped polyvinylchloride (PVC) particles (15, 1500, 15,000, 150,000, 1,500,000 particles/individual/week calibrated in the size range 11–60 μm) and regularly shaped polystyrene (PS) beads (15, 1500, 15,000 particles/individual/week, 40 μm) over 42 weeks. During this period, we monitored physiological traits such as clearance rate, byssus production, growth rate, superoxide dismutase (SOD) activity, malondialdehyde (MDA) concentrations, and the condition index (CI). Negative effects of the tested microplastics on mussel performance emerged late in the experiment and were rather weak. Interestingly, even after having received the lowest particle dose of PS, SOD activity in the gill was significantly lower in mussels exposed to microplastics compared to a group of conspecifics that were kept in clean water. However, growth and CI, which are both closely related to the fitness of the mussels, were not found to be impaired at the end of the exposure phase. This is the so far longest laboratory microplastic exposure study on mussels and we worked with particle doses that reflect todays pollution levels. The small effect sizes we observed for the response variables assessed suggest that these specific microplastics pose only a minor threat to blue mussel populations.

Description: Highlights: • The fate of PS microbeads in an exposure experiment was assessed over 50 h. • Targeted and realized MP concentrations can differ largely in controlled laboratory experiments. • Clearance rates of mussels were significantly decreased in the presence of MP. • Reduction of clearance rates was more pronounced in mussels that had recently spawned. Abstract: The fate of microplastic particles (MP) in exposure experiments is mostly unclear. We measured the recovery of polystyrene (PS) microbeads, which were applied in various concentrations from 0.07 to 47.47 beads/ml, from the different compartments of an experimental system with mussels (Mytilus spp.). At the end of the experiment, we detected a significant loss of MP indicating that the mussels were exposed to less particles than intended. If such a discrepancy remains un-recognized by the experimenter, observed effects are related to an inaccurate particle concentration. Additionally, we observed reduced clearance rates of the mussels in the presence of MP and the effect size increased with increasing particle concentration. This effect was more pronounced in mussels that had recently spawned than in mussels that still had mature gonads. This is a hint that effects of MP may depend on the reproductive status of an organism.