Trophic transfer increases the exposure to microplastics in littoral predators.

Predators in aquatic environments can be exposed to microplastics (MPs) directly through water and indirectly through prey. Laboratory experiments were conducted to study the potential of MP trophic transfer in Baltic Sea littoral food chains of different lengths. The longest studied food chain had three trophic levels: zooplankton, chameleon shrimp (Praunus flexuosus) and rockpool prawn (Palaemon elegans). 10 µm fluorescence microspheres were used as tracer MP particles and MP ingestion was verified with epifluorescence microscopy. Transfer of MPs occurred up to both second and third trophic level. The number of ingested microspheres in both chameleon shrimp and rockpool prawn was higher when the animals were exposed through pre-exposed prey in comparison to direct exposure through the water. The results show that trophic transfer may be an important pathway of and increase the microplastic exposure for some animals at higher trophic levels in highly polluted areas.

Quantifying impacts of human pressures on ecosystem services: Effects of widespread non-indigenous species in the Baltic Sea.

Ecosystem services (ES) are the benefits natural ecosystems provide to society, such as food provisioning, water supply, climate regulation and recreational benefits. Biological invasions are a major driver of global change, and several non-indigenous species (NIS) may alter key ecological feedbacks with ultimate consequences to ES, livelihoods and human wellbeing. Nonetheless, the effects of NIS on ES supply remain largely unquantified. Here we present the first quantitative case study assessing the impacts of widespread NIS on ES in the Baltic Sea, by developing and employing a robust and repeatable data-driven approach. All NIS with a sufficient knowledge base pose large and highly significant effects on ES, resulting on average 55 % change in the intensity of ES. Most impacts affected regulation services, concerning both abiotic and biotic realms, with little evidence on cultural and provisioning services. The methodology can be easily employed beyond the current study realm e.g. to better understand the roles of human pressures on ES in any ecosystem. Importantly, the study also identified major biases not only in the availability of taxonomic and sub-regional evidence, but also in the different study types employed to create the evidence base.

The economic costs, management and regulation of biological invasions in the Nordic countries.

A collective understanding of economic impacts and in particular of monetary costs of biological invasions is lacking for the Nordic region. This paper synthesizes findings from the literature on costs of invasions in the Nordic countries together with expert elicitation. The analysis of cost data has been made possible through the InvaCost database, a globally open repository of monetary costs that allows for the use of temporal, spatial, and taxonomic descriptors facilitating a better understanding of how costs are distributed. The total reported costs of invasive species across the Nordic countries were estimated at $8.35 billion (in 2017 US$ values) with damage costs significantly outweighing management costs. Norway incurred the highest costs ($3.23 billion), followed by Denmark ($2.20 billion), Sweden ($1.45 billion), Finland ($1.11 billion) and Iceland ($25.45 million). Costs from invasions in the Nordics appear to be largely underestimated. We conclude by highlighting such knowledge gaps, including gaps in policies and regulation stemming from expert judgment as well as avenues for an improved understanding of invasion costs and needs for future research.

Testing citizen science as a tool for monitoring surface water microplastics.

The use of citizen science in the collection of surface water marine microplastics (MP) samples with manta trawl was tested in the Baltic Sea, where the collection of surface water samples is often hampered by environmental conditions. Sampling was carried out at 7 locations around the Baltic Sea with a custom-made manta trawl which was operated onboard a sailing boat. The total concentrations of ≥ 0.3 mm MP in the samples ranged from 0.45 to 1.98 MP m-3. Based on the results and experiences from this study, citizen science could be introduced into the toolbox of monitoring large MP. When the common basic constraints of surface water sampling within a regional sea are defined and agreed upon, citizen science could be used for strengthening the power of assessments on the state of the marine environment by increasing the spatial coverage of the monitored area.

A multi-criteria decision analysis model for ship biofouling management in the Baltic Sea.

Biofouling of ship hulls form a vector for the introduction of non-indigenous organisms worldwide. Through increasing friction, the organisms attached to ships' hulls increase the fuel consumption, leading to both higher fuel costs and air emissions. At the same time, ship biofouling management causes both ecological risks and monetary costs. All these aspects should be considered case-specifically in the search of sustainable management strategies. Applying Bayesian networks, we developed a multi-criteria decision analysis model to compare biofouling management strategies in the Baltic Sea, given the characteristics of a ship, its operating profile and operational environment, considering the comprehensive environmental impact and the monetary costs. The model is demonstrated for three scenarios (SC1-3) and sub-scenarios (A-C), comparing the alternative biofouling management strategies in relation to NIS (non-indigenous species) introduction risk, eco-toxicological risk due to biocidal coating, carbon dioxide emissions and costs related to fuel consumption, in-water cleaning and hull coating. The scenarios demonstrate that by the careful consideration of the hull fouling management strategy, both money and environment can be saved. We suggest biocidal-free coating with a regular in-water cleaning using a capture system is generally the lowest-risk option. The best biocidal-free coating type and the optimal in-water cleaning interval should be evaluated case-specifically, though. In some cases, however, biocidal coating remains a justifiable option.

Exposure to leachates from post-consumer plastic and recycled rubber causes stress responses and mortality in a copepod Limnocalanus macrurus.

Effects of household post-consumer plastics and tyre rubber on a Baltic Sea copepod Limnocalanus macrurus were assessed. Fragments of commercial recycled low-density polyethylene vegetable bags and rubber originating from recycled car tyres were incubated in seawater, and the copepods were exposed to the filtrate of the water. L. macrurus experienced erratic swimming behaviour and increased mortality in the filtrate of unwashed vegetable bags, containing elevated concentrations of alcohols, organic acids and copper. Responses of the antioxidant defence system (ADS) were recorded in copepods exposed to rubber treatments containing high concentrations of zinc. Significant responses in the ADS enzymes indicate that reactive oxygen species (ROS) formation was exceeding the detoxification capacity of the ADS which may further lead to prolonged state of oxidative stress. Observed effects of exposure on the biochemical level coincide with impaired swimming activity of the copepods, indicating possible irreversible cellular responses leading to behavioural changes and mortality.

The role of marinas in the establishment and spread of non-indigenous species in Baltic Sea fouling communities.

The study included the sampling of 12 marinas across six areas of the Baltic Sea with settlement plates and scraping of submerged structures to assess the role of marinas in the spread of non-indigenous species (NIS) via biofouling. 15 NIS were detected in the marinas and secondary spread of previously introduced NIS was detected in five out of six sea areas. Salinity and sea area significantly affected the composition of the fouling assemblages. Settlement plates appeared as the more efficient sampling method over scraping, while the seasonal analyses revealed that the monitoring effort should span over the summer and early autumn in the south-eastern, central, and northern Baltic Sea. The present findings indicate that marinas contribute to the spread of non-indigenous fouling organisms, and there is an increasing demand for the monitoring of marinas and stricter regulations regarding the biofouling management of leisure boats in the Baltic Sea.

Microplastic ingestion by small coastal fish in the northern Baltic Sea, Finland.

Microplastic (MP) ingestion by four species of small coastal fish from the northern Baltic Sea was investigated. The digestive tract contents of 424 specimens, caught across eight sampling sites along the Finnish coastline were analysed for the occurrence of MP ingestion. MP were found in 38 fish individuals (9% of sampled fish). Specimens from the urban area of Helsinki displayed the highest prevalence of ingested plastics (27.5%). No relationship was found between the size or species of the fish and the presence of ingested MP particles nor the amount of MP in seawater. The comparison to a previous study conducted using the same research methods indicates that the ingestion of MP is more common in coastal fish than in offshore fish in the northern Baltic Sea.

Validation of an imaging FTIR spectroscopic method for analyzing microplastics ingestion by Finnish lake fish (Perca fluviatilis and Coregonus albula).

Despite the ubiquitousness of microplastics, knowledge on the exposure of freshwater fish to microplastics is still limited. Moreover, no standard methods are available for analyzing microplastics, and the quality of methods used for the quantification of ingested microplastics in fish should be improved. In this study, we studied microplastic ingestion of common wild freshwater fish species, perch (Perca fluviatilis) and vendace (Coregonus albula). Further, our aim was to develop and validate imaging Fourier-transform infrared spectroscopic method for the quantification of ingested microplastics. For this purpose, enzymatically digested samples were measured with focal plane array (FPA) based infrared microscope. Data was analyzed with siMPle software, which provides counts, mass estimations, sizes, and materials for the measured particles. Method validation was conducted with ten procedural blanks and recovery tests, resulting in 75% and 77% recovery rates for pretreatment and infrared imaging, respectively. Pretreatment caused contamination principally by small <100 µm microplastics. The results showed that 17% of perch and 25% of vendace had ingested plastic. Most of the fish contained little or no plastics, while some individuals contained high numbers of small particles or alternatively few large particles. Perch from one sampling site out of five had ingested microplastics, but vendace from all sampling sites had ingested microplastics. The microplastics found from fish were mostly small: 81% had particle size between 20 and 100 µm, and most of them were polyethylene, polypropylene, and polyethylene terephthalate. In conclusion, the implemented method revealed low numbers of ingested microplastics on average but needs further development for routine monitoring of small microplastics.

Exceptions and exemptions under the ballast water management convention - Sustainable alternatives for ballast water management?

The International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM Convention) aims to mitigate the introduction risk of harmful aquatic organisms and pathogens (HAOP) via ships' ballast water and sediments. The BWM Convention has set regulations for ships to utilise exceptions and exemptions from ballast water management under specific circumstances. This study evaluated local and regional case studies to provide clarity for situations, where ships could be excepted or exempted from ballast water management without risking recipient locations to new introductions of HAOP. Ships may be excepted from ballast water management if all ballasting operations are conducted in the same location (Regulation A-3.5 of the BWM Convention). The same location case study determined whether the entire Vuosaari harbour (Helsinki, Finland) should be considered as the same location based on salinity and composition of HAOP between the two harbour terminals. The Vuosaari harbour case study revealed mismatching occurrences of HAOP between the harbour terminals, supporting the recommendation that exceptions based on the same location concept should be limited to the smallest feasible areas within a harbour. The other case studies evaluated whether ballast water exemptions could be granted for ships using two existing risk assessment (RA) methods (Joint Harmonised Procedure [JHP] and Same Risk Area [SRA]), consistent with Regulation A-4 of the BWM Convention. The JHP method compares salinity and presence of target species (TS) between donor and recipient ports to indicate the introduction risk (high or low) attributed to transferring unmanaged ballast water. The SRA method uses a biophysical model to determine whether HAOP could naturally disperse between ports, regardless of their transportation in ballast water. The results of the JHP case study for the Baltic Sea and North-East Atlantic Ocean determined that over 97% of shipping routes within these regions resulted in a high-risk indication. The one route assessed in the Gulf of Maine, North America also resulted in a high-risk outcome. The SRA assessment resulted in an overall weak connectivity between all ports assessed within the Gulf of the St. Lawrence, indicating that a SRA-based exemption would not be appropriate for the entire study area. In summary, exceptions and exemptions should not be considered as common alternatives for ballast water management. The availability of recent and detailed species occurrence data was considered the most important factor to conduct a successful and reliable RA. SRA models should include biological factors that influence larval dispersal and recruitment potential (e.g., pelagic larval duration, settlement period) to provide a more realistic estimation of natural dispersal.

Identifying biotic drivers of population dynamics in a benthic-pelagic community.

Benthic species and communities are linked to pelagic zooplankton through life-stages encompassing both benthic and pelagic habitats and through a mutual dependency on primary producers as a food source. Many zooplankton taxa contribute to the sedimentary system as benthic eggs. Our main aim was to investigate the nature of the population level biotic interactions between and within these two seemingly independent communities, both dependent on the pelagic primary production, while simultaneously accounting for environmental drivers (salinity, temperature, and oxygen conditions). To this end, we applied multivariate autoregressive state-space models to long (1966-2007) time series of annual abundance data, comparing models with and without interspecific interactions, and models with and without environmental variables included. We were not able to detect any direct coupling between sediment-dwelling benthic taxa and pelagic copepods and cladocerans on the annual scale, but the most parsimonious model indicated that interactions within the benthic community are important. There were also positive residual correlations between the copepods and cladocerans potentially reflecting the availability of a shared resource or similar seasonal dependence, whereas both groups tended to correlate negatively with the zoobenthic taxa. The most notable single interaction within the benthic community was a tendency for a negative effect of Limecola balthica on the amphipods Monoporeia affinis and Pontoporeia femorata which can help explain the observed decrease in amphipods due to increased competitive interference.

Meta-analysis on the ecological impacts of widely spread non-indigenous species in the Baltic Sea.

The introduction of non-indigenous species (NIS) is a major driver for global change in species biogeography, often associated with significant consequences for recipient ecosystems and services they provide for humans. Despite mandated by several high-level international legislative instruments, comprehensive quantitative evaluation on ecosystem impacts of marine NIS is scarce and lack a robust and data-driven assessment framework. The current study is aiming at fulfilling this gap, through quantitative assessment on the effects of the widespread NIS of the Baltic Sea on multiple ecosystem features and components including direct food-web effects. The outcomes of this study allowed identifying the most impacting widespread NIS, together with defining the processes underlying the most significant changes and outlined major sources of uncertainty. Lack and/or bias in the availability of evidence of impacts was recorded for several (both recent and early) introductions. Realizing a sophisticated, data and information-hungry framework for the evaluation of ecosystem impacts of NIS is not pragmatic for management purposes in the foreseeable future. Instead, simple approaches, such as application of common statistical parameters like absolute effect size, are more likely to result in tangible outcomes. As bearing no unit, effect sizes can be later easily aggregated across taxa, affected ecosystem features or spatial scales. The proposed approach enables performing systematic comparisons on the severity of impacts of different NIS along different study disciplines and ecosystems.

Microplastics accumulate to thin layers in the stratified Baltic Sea.

In the Baltic Sea, water is stratified due to differences in density and salinity. The stratification prevents water from mixing, which could affect sinking rates of microplastics in the sea. We studied the accumulation of microplastics to halocline and thermocline. We sampled water with a 100 µm plankton net from vertical transects between halo- and thermocline, and a 30 L water sampler from the end of halocline and the beginning of thermocline. Thereafter, microplastics in the whole sample volumes were analyzed with imaging Fourier transform infrared spectroscopy (FTIR). The plankton net results showed that water column between halo- and thermoclines contained on average 0.92 ± 0.61 MP m-3 (237 ± 277 ng/m-3; mean ± SD), whereas the 30 L samples from the end of halocline and the beginning of thermocline contained 0.44 ± 0.52 MP L-1 (106 ± 209 ng L-1). Hence, microplastics are likely to accumulate to thin layers in the halocline and thermocline. The vast majority of the found microplastics were polyethylene, polypropylene and polyethylene terephthalate, which are common plastic types. We did not observe any trend between the density of microplastics and the sampling depth, probably because biofilm formation affected the sinking rates of the particles. Our results indicate the need to sample deeper water layers in addition to surface waters at least in the stratified water bodies to obtain a comprehensive overview of the abundance of microplastics in the aquatic environment.

Polycyclic aromatic hydrocarbon sorption and bacterial community composition of biodegradable and conventional plastics incubated in coastal sediments.

Resistant to degradation, plastic litter poses a long-term threat to marine ecosystems. Biodegradable materials have been developed to replace conventional plastics, but little is known of their impacts and degradation in marine environments. A 14-week laboratory experiment was conducted to investigate the sorption of polycyclic aromatic hydrocarbons (PAHs) to conventional (polystyrene PS and polyamide PA) and bio-based, biodegradable plastic films (cellulose acetate CA and poly-L-lactic acid PLLA), and to examine the composition of bacterial communities colonizing these materials. Mesoplastics (1 cm2) of these materials were incubated in sediment and seawater collected from two sites in the Gulf of Finland, on the coast of the highly urbanized area of Helsinki, Finland. PS sorbed more PAHs than did the other plastic types at both sites, and the concentration of PAHs was consistently and considerably smaller in plastics than in the sediment. In general, the plastic bacterial biofilms resembled those in the surrounding media (water and/or sediment). However, in the sediment incubations, the community composition on CA diverged from that of the other three plastic types and was enriched with Bacteroidia and potentially cellulolytic Spirochaetia at both sites. The results indicate that certain biodegradable plastics, such as CA, may harbour potential bioplastic-degrading communities and that PAH sorption capacity varies between polymer types. Since biodegradable plastics are presented as replacements for conventional plastics in applications with risk of ending up in the marine environment, the results highlight the need to carefully examine the environmental behaviour of each biodegradable plastic type before they are extensively introduced to the market.

Citizen science provides added value in the monitoring for coastal non-indigenous species.

Continuous and comprehensive monitoring is one of the most important practices to trace changes in the state of the environment and target management efforts. Yet, governmental resources are often insufficient for monitoring all required environmental parameters, and therefore authorities have started to utilize citizen observations to supplement and increase the scale of monitoring. The aims of the present study were to show the potential of citizen science in environmental monitoring by utilising citizen observations of the non-indigenous Harris mud crab Rhithropanopeus harrisii in Finnish waters, where coastal monitoring is insufficient to estimate the distribution and spread of non-indigenous species. Harris mud crab has shown measurable impact locally and is considered invasive. For reporting the status of invasions to national and European authorities and planning for potential eradication efforts, up to date knowledge on NIS ranges are needed. Citizen observations on the species were collected from the first observation onwards between 2009 and 2018, at first via email and later through an active citizen observation web portal (Invasive Alien Species Portal). The outcomes of the study indicate that species-specific citizen observations can be a beneficial addition to supplement national monitoring programs to fulfil legislative reporting requirements and to target potential management. Recognizable species and geographical areas with low biodiversity provide a good opportunity to utilize citizen observations. Moreover, citizen observations may enable distribution assessments for certain species that would otherwise require excessive resources and sampling efforts.

How Copepods Can Eat Toxins Without Getting Sick: Gut Bacteria Help Zooplankton to Feed in Cyanobacteria Blooms.

Toxin-producing cyanobacteria can be harmful to aquatic biota, although some grazers utilize them with often beneficial effects on their growth and reproduction. It is commonly assumed that gut microbiota facilitates host adaptation to the diet; however, the evidence for adaptation mechanisms is scarce. Here, we investigated the abundance of mlrA genes in the gut of the Baltic copepods Acartia bifilosa and Eurytemora affinis during cyanobacteria bloom season (August) and outside it (February). The mlrA genes are unique to microcystin and nodularin degraders, thus indicating the capacity to break down these toxins by the microbiota. The mlrA genes were expressed in the copepod gut year-round, being >10-fold higher in the summer than in the winter populations. Moreover, they were significantly more abundant in Eurytemora than Acartia. To understand the ecological implications of this variability, we conducted feeding experiments using summer- and winter-collected copepods to examine if/how the mlrA abundance in the microbiota affect: (1) uptake of toxic Nodularia spumigena, (2) uptake of a non-toxic algal food offered in mixtures with N. spumigena, and (3) concomitant growth potential in the copepods. The findings provide empirical evidence that the occurrence of mlrA genes in the copepod microbiome facilitates nutrient uptake and growth when feeding on phytoplankton mixtures containing nodularin-producing cyanobacteria; thus, providing an adaptation mechanism to the cyanobacteria blooms.

Microplastic concentrations, size distribution, and polymer types in the surface waters of a northern European lake.

We examined microplastic concentrations, size distributions, and polymer types in surface waters of a northern European dimictic lake. Two sampling methods, a pump sieving water onto filters with different pore sizes (20, 100, and 300 µm) and a common manta trawl (333 µm), were utilized to sample surface water from 12 sites at the vicinity of potential sources for microplastic emissions. The number and polymer types of microplastics in the samples were determined with optical microscopy and µFTIR spectroscopy. The average concentrations were 0.27 ± 0.18 (mean ± SD) microplastics/m3 in manta trawled samples and 1.8 ± 2.3 (>300 µm), 12 ± 17 (100-300 µm) and 155 ± 73 (20-100 µm) microplastics/m3 in pump filtered samples. The majority (64%) of the identified microplastics (n = 168) were fibers, and the rest were fragments. Materials were identified as polymers commonly used in consumer products, such as polyethylene, polypropylene, and polyethylene terephthalate. Microplastic concentrations were high near the discharge pipe of a wastewater treatment plant, harbors, and snow dumping site. PRACTITIONER POINTS: Samples were taken with a manta trawl (333 µm) and a pump filtration system (300/100/20 µm) With pump filtration, small 20-300 µm particles were more common than >300 µm particles The average concentration of manta trawled samples was 0.27 ± 0.18 (mean ± SD) microplastics/m3 FTIR analysis revealed PE, PP, PET, and PAN to be the most common polymers.

Non-indigenous species refined national baseline inventories: A synthesis in the context of the European Union's Marine Strategy Framework Directive.

Refined baseline inventories of non-indigenous species (NIS) are set per European Union Member State (MS), in the context of the Marine Strategy Framework Directive (MSFD). The inventories are based on the initial assessment of the MSFD (2012) and the updated data of the European Alien Species Information Network, in collaboration with NIS experts appointed by the MSs. The analysis revealed that a large number of NIS was not reported from the initial assessments. Moreover, several NIS initially listed are currently considered as native in Europe or were proven to be historical misreportings. The refined baseline inventories constitute a milestone for the MSFD Descriptor 2 implementation, providing an improved basis for reporting new NIS introductions, facilitating the MSFD D2 assessment. In addition, the inventories can help MSs in the establishment of monitoring systems of targeted NIS, and foster cooperation on monitoring of NIS across or within shared marine subregions.

Monitoring of sessile and mobile epifauna - Considerations for non-indigenous species.

The present study aimed to develop monitoring methods for shallow water sessile and mobile epifauna with the main focus on enhancing the chance of early detection for new non-indigenous species (NIS) invasions. The field sampling was conducted between June and September in 2012, in the Archipelago Sea (Finland). The tested monitoring methods included baited traps that capture organisms and habitat collectors that provide habitat and refuges for organisms, as well as fouling plates. Catch efficiency of a trap/collector was defined as the number of NIS and all species caught, including their abundances. The American collector with oyster shells (habitat collector) caught the highest number of NIS, and their use is recommended in all places, where oyster shells are easily accessible. Sampling of all habitats of interest between 1 and 2 m depth is recommended with at least three habitat collectors per site.

Seafloor sediments as microplastic sinks in the northern Baltic Sea - Negligible upward transport of buried microplastics by bioturbation.

Microplastics (MPs) are ubiquitous in the marine environment. High concentrations of MPs are found from seafloor sediments, which have been proposed to act as their final sinks. Because bioturbation is an important process affecting the burial of MPs, a mesocosm experiment was established to study whether sediment infauna may also promote MP return to the sediment surface. Thin layers of frozen sediment containing an environmentally realistic concentration (<1300 MPs per kg of dry sediment) of MP fragments in two size classes (>500 µm and 100-300 µm) were added to depths of 2 cm and 5 cm in the experimental cylinders filled with sediment. The displacement of these MPs, made of acrylonitrile butadiene styrene (ABS), by a community of common benthic invertebrates in the northern Baltic Sea (clam Limecola balthica, polychaete Marenzelleria spp., gammarid Monoporeia affinis) was studied in a 10-week experiment. After the experiment, the MPs were extracted from each sediment layer and the animals were examined for MP ingestion. The results indicated that the transportation of MPs to the sediment surface by bioturbation was negligible. Thus, in the Baltic Sea, the seafloor may act as a sink for once sedimented MPs, reducing simultaneously the MP exposure of the macrofauna feeding on the sediment surface.