ALBERT

Description: This dataset comprises data obtained during a 6 week-long exposure experiment of mussels of the family Mytilidae to two types of microplastics, namely polymethyl methacrylate (PMMA) and polyvinylchloride (PVC) particles and two types of natural inorganic microparticles, namely diatoms and red clay. This data was obtained from May to September 2019 in five different bioregions, which are Tasmania, Chile, Japan, Cabo Verde and Israel. We recorded body condition index, byssus thread production in 24 hours, clearance rate of the food algae and respiration rate at the end of six weeks of exposure to the four different microparticles (with an exception of the groups exposed to PVC and red clay in Tasmania, which lasted 5 weeks). Mussels were exposed to three concentrations of each particle type, which were 1.5, 15 and 150 mg/l and one group to no particles at all as control.

Description: Mussels perform several key ecological functions in the oceans, such as water filtration, reef-building and the enhancement of the benthic-pelagic coupling. They are exposed to a variety of abiotic microparticles in their natural environment and have developed mechanisms to cope with these indigestible particles. A newly introduced type of microparticle in the oceans are microplastics (plastics 〈 5 mm) that mainly derive from the fragmentation of larger plastic debris. The production of plastic has increased exponentially over the last decades, and so has the pollution of the environment by plastics. It was shown that microplastics are ubiquitous in the marine environment, with largely unknown effects on marine life. For this reason, laboratory effect studies are required to find out whether microplastics pose a novel risk to marine biota or whether they can be treated as just another component of abiotic seston. In this study, I exposed juvenile farmed mussels (Mytilus galloprovincialis) in a controlled laboratory experiment to both microplastics (recycled PMMA, mean size: 120 μm) and natural inorganic particles (diatom shells, mean size: 86 μm). Both particles were irregularly shaped fragments that were constantly resuspended in the water column. The microparticles were applied at three different concentration levels (1.5 mg/l, 15 mg/l, 150 mg/l), to mimic seston concentrations naturally occuring in the oceans. After 42 days of exposure, the respiration rates (by up to 67 %), the dry weight (by up to 23 %) and the body condition index (by up to 20 %) were lower in mussels exposed to microplastics than in mussels treated with natural particles. The significant differences occured independently of particle concentrations. No effects were found for the clearance rates, the byssus thread formation and the mortality of the mussels. The negative effects of microplastics on the physiology of the mussels are presumably caused by oxidative stress and an altered feeding behaviour due to gill damages, as the mussels were always fed in the presence of microparticles. Nevertheless, M. galloprovincialis showed robustness against high particle loads, which verifies the fact that mussels originate from turbid environments and are well adapted to these conditions. The negative effects of microplastic exposure on the respiration rates of the mussels were only detectable after the long-term exposure of 42 days, which underlines the importance of extended exposure times in laboratory effect studies. Since the effects have always been negative for mussels exposed to microplastics compared to mussels treated with natural particles, I assume that microplastics have specific physical and chemical properties, e. g. surface tension, charge and hydrophobicity, that make them a novel stressor in the marine environment.

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.