Coastal Marine Ecosystems Research Articles

Recovering high-quality bacterial genomes from cross-contaminated cultures: a case study of marine Vibrio campbellii

BackgroundEnvironmental monitoring of bacterial pathogens is critical for disease control in coastal marine ecosystems to maintain animal welfare and ecosystem function and to prevent significant economic losses. This requires accurate taxonomic identification of environmental bacterial pathogens, which often cannot be achieved by commonly used genetic markers (e.g., 16S rRNA gene), and an understanding of their pathogenic potential based on the information encoded in their genomes. The decreasing costs of whole genome sequencing (WGS), combined with newly developed bioinformatics tools, now make it possible to unravel the full potential of environmental pathogens, beyond traditional microbiological approaches. However, obtaining a high-quality bacterial genome, requires initial cultivation in an axenic culture, which is a bottleneck in environmental microbiology due to cross-contamination in the laboratory or isolation of non-axenic strains.ResultsWe applied WGS to determine the pathogenic potential of two Vibrio isolates from coastal seawater. During the analysis, we identified cross-contamination of one of the isolates and decided to use this dataset to evaluate the possibility of bioinformatic contaminant removal and recovery of bacterial genomes from a contaminated culture. Despite the contamination, using an appropriate bioinformatics workflow, we were able to obtain high quality and highly identical genomes (Average Nucleotide Identity value 99.98%) of one of the Vibrio isolates from both the axenic and the contaminated culture. Using the assembled genome, we were able to determine that this isolate belongs to a sub-lineage of Vibrio campbellii associated with several diseases in marine organisms. We also found that the genome of the isolate contains a novel Vibrio plasmid associated with bacterial defense mechanisms and horizontal gene transfer, which may offer a competitive advantage to this putative pathogen.ConclusionsOur study shows that, using state-of-the-art bioinformatics tools and a sufficient sequencing effort, it is possible to obtain high quality genomes of the bacteria of interest and perform in-depth genomic analyses even in the case of a contaminated culture. With the new isolate and its complete genome, we are providing new insights into the genomic characteristics and functional potential of this sub-lineage of V. campbellii. The approach described here also highlights the possibility of recovering complete bacterial genomes in the case of non-axenic cultures or obligatory co-cultures.

Flexible B12 ecophysiology of Phaeocystis antarctica due to a fusion B12–independent methionine synthase with widespread homologues

Coastal Antarctic marine ecosystems are significant in carbon cycling because of their intense seasonal phytoplankton blooms. Southern Ocean algae are primarily limited by light and iron (Fe) and can be co-limited by cobalamin (vitamin B12). Micronutrient limitation controls productivity and shapes the composition of blooms which are typically dominated by either diatoms or the haptophyte Phaeocystis antarctica. However, the vitamin requirements and ecophysiology of the keystone species P. antarctica remain poorly characterized. Using cultures, physiological analysis, and comparative omics, we examined the response of P. antarctica to a matrix of Fe-B12 conditions. We show that P. antarctica is not auxotrophic for B12, as previously suggested, and identify mechanisms underlying its B12 response in cultures of predominantly solitary and colonial cells. A combination of proteomics and proteogenomics reveals a B12-independent methionine synthase fusion protein (MetE-fusion) that is expressed under vitamin limitation and interreplaced with the B12-dependent isoform under replete conditions. Database searches return homologues of the MetE-fusion protein in multiple Phaeocystis species and in a wide range of marine microbes, including other photosynthetic eukaryotes with polymorphic life cycles as well as bacterioplankton. Furthermore, we find MetE-fusion homologues expressed in metaproteomic and metatranscriptomic field samples in polar and more geographically widespread regions. As climate change impacts micronutrient availability in the coastal Southern Ocean, our finding that P. antarctica has a flexible B12 metabolism has implications for its relative fitness compared to B12-auxotrophic diatoms and for the detection of B12-stress in a more diverse set of marine microbes.

Metagenomic insights into the dynamic degradation of brown algal polysaccharides by kelp-associated microbiota.

Marine bacteria play important roles in the degradation and cycling of algal polysaccharides. However, the dynamics of epiphytic bacterial communities and their roles in algal polysaccharide degradation during kelp decay are still unclear. Here, we performed metagenomic analyses to investigate the identities and predicted metabolic abilities of epiphytic bacterial communities during the early and late decay stages of the kelp Saccharina japonica. During kelp decay, the dominant epiphytic bacterial communities shifted from Gammaproteobacteria to Verrucomicrobia and Bacteroidetes. In the early decay stage of S. japonica, epiphytic bacteria primarily targeted kelp-derived labile alginate for degradation, among which the gammaproteobacterial Vibrionaceae (particularly Vibrio) and Psychromonadaceae (particularly Psychromonas), abundant in alginate lyases belonging to the polysaccharide lyase (PL) families PL6, PL7, and PL17, were key alginate degraders. More complex fucoidan was preferred to be degraded in the late decay stage of S. japonica by epiphytic bacteria, predominantly from Verrucomicrobia (particularly Lentimonas), Pirellulaceae of Planctomycetes (particularly Rhodopirellula), Pontiellaceae of Kiritimatiellota, and Flavobacteriaceae of Bacteroidetes, which depended on using glycoside hydrolases (GHs) from the GH29, GH95, and GH141 families and sulfatases from the S1_15, S1_16, S1_17, and S1_25 families to depolymerize fucoidan. The pathways for algal polysaccharide degradation in dominant epiphytic bacterial groups were reconstructed based on analyses of metagenome-assembled genomes. This study sheds light on the roles of different epiphytic bacteria in the degradation of brown algal polysaccharides.IMPORTANCEKelps are important primary producers in coastal marine ecosystems. Polysaccharides, as major components of brown algal biomass, constitute a large fraction of organic carbon in the ocean. However, knowledge of the identities and pathways of epiphytic bacteria involved in the degradation process of brown algal polysaccharides during kelp decay is still elusive. Here, based on metagenomic analyses, the succession of epiphytic bacterial communities and their metabolic potential were investigated during the early and late decay stages of Saccharina japonica. Our study revealed a transition in algal polysaccharide-degrading bacteria during kelp decay, shifting from alginate-degrading Gammaproteobacteria to fucoidan-degrading Verrucomicrobia, Planctomycetes, Kiritimatiellota, and Bacteroidetes. A model for the dynamic degradation of algal cell wall polysaccharides, a complex organic carbon, by epiphytic microbiota during kelp decay was proposed. This study deepens our understanding of the role of epiphytic bacteria in marine algal carbon cycling as well as pathogen control in algal culture.

Drivers of marine heatwaves in a stratified marginal sea

Marine heatwaves (MHWs) can cause devastating impacts in coastal marine ecosystems, particularly in shallow marginal seas, thereby making the understanding of the drivers of these events of paramount importance. Here, drivers for summer and winter MHWs are explored for the period 1980–2016 in the Baltic Sea, a mid-latitude marginal sea with a permanent haline water-column stratification located on the northwestern European shelf. It was found that summer MHWs are mainly forced by local meteorological conditions over the open water. They are caused by a dominant blocking over Scandinavia promoting anomalous strong shortwave downflux, calm winds, and low vertical mixing with colder sub-thermocline waters. Wintertime MHWs are linked to the advection of warm and moist air originating from the North Atlantic. These air masses lower the oceanic net heat loss at the sea surface primarily in the form of reduced latent and sensible heat losses. Vertical ocean dynamics are also affected during winter MHWs. This study finds a strengthened coastal up- and downwelling due to anomalous strong westerly winds during the time before MHWs culminate in their maximal surface extension.

Study of current benthic foraminifera as environmental bioindicators in the mediterranean coasts, northwest Morocco

In this project, we introduce a novel methodology for analysing the environmental conditions in the coastal area of Martil (Tétouan, Morocco) using benthic foraminifera as bio-indicators of marine ecological status. Benthic foraminifera have emerged as reliable indicators of environmental pollution, Their sensitivity to environmental changes, wide geographic presence, and short life cycle make them ideal for indicating the ecological status. Our study focused on the Mediterranean coastal region, along a radial perpendicular to the coast, at different depths, at the mouth of the Martil River, in addition to a control sample collected in the Azla region at a depth of 25 meters. Abiotic parameters like pH, temperature, and dissolved oxygen were measured on-site, complemented by detailed sedimentary analyses in the laboratory. A meticulous protocol was followed for the study of microfauna, particularly benthic foraminifera, involving washing, extraction, sorting, species identification, statistical counting, and microscopic imaging. Utilizing CA and AHC analyses, we identified factors influencing benthic foraminifera distribution, such as sediment depth and grain size variations. Specific indices derived from foraminifera data allowed us to assess stress levels accurately. This comprehensive approach provides valuable insights into evaluating the ecological health of Morocco's coastal marine ecosystems, paving the way for informed conservation efforts and sustainable management practices.

Spatiotemporal variability in the structure and diversity of understory faunal assemblages associated with the kelp Eisenia cokeri (Laminariales) in Peru

Kelp species function as foundation organisms in coastal marine ecosystems, where they alter environmental conditions and promote local biodiversity by providing complex biogenic habitat for an array of associated organisms. The structure and functioning of kelp forest ecosystems in some regions, such as along the Peruvian coastline, remain critically understudied. We quantified the structure and diversity of faunal assemblages within both holdfast and understory reef habitats within Eisenia cokeri forests. We sampled both habitat types within four subtidal kelp forests on multiple occasions between 2016 and 2020, and quantified fauna at a fine taxonomic level (mostly species). We recorded a total of ~ 55,000 individuals representing 183 taxa across the study, with holdfast assemblages typically exhibiting higher richness, abundance and biomass values compared with understory reef-associated assemblages. Holdfast assemblages were structurally and functionally dissimilar to those on reef surfaces and were less variable and consistent across sites and sampling events. Even so, assemblages associated with both habitat types varied significantly between sites and sampling events, with variation in upwelling strength, ocean currents, and grazing pressure among potential drivers of this ecological variability. Overall, E. cokeri supports diverse and abundant holdfast assemblages and functions as a foundation organism in Peru. Given that no other habitat-forming kelp species persist at the low latitudes of E. cokeri in mid-to-north Peru, the lack of functional redundancy suggests that effective management and conservation of this species is vital for wider ecosystem processes and biodiversity maintenance.

Eutrophication Mechanisms and Their Impacts on Coastal Marine Ecosystems

Eutrophication Mechanisms and Their Impacts on Coastal Marine Ecosystems

Evolution of Quaternary Landforms Between Vedaranniyam and Rameswaram - A Case Study

Coast is a significant place where land and sea or oceans meet that form the boundary between them. The coastal area is frequently susceptible to natural disasters like – tsunamis, cyclones, erosion, etc. and anthropogenic activities like the construction of harbor, jetties, breakwaters, and groins. These hazards are often affecting coastal zones and marine ecosystems. Usual aeolian, fluvial, tidal, and fluvial-tidal events primarily control the morpho dynamic changes along this coast. Tamil Nadu’s coastline, which makes up the south-eastern portion of the Coromendal coast, is parallel to the eastern ghat orogeny faults. The aerial photos and temporal, spatial data, with the help of Survey of India toposheets (1970) over the periods of 50 – 60 years, were used to identify different geomorphological features, strand lines (IRS 1B 1991, IRS 1C 2004, IRS P6 2004 and IRS 1D merged data (2006), erosional activities along the Vedaranyam to Rameshwaram coastal area. The present study attempts to place together all the physical evidence of whatever origin and nature, notwithstanding their contradictory directions and shift and evaluation them in the context of the evolving configuration of the coast. In Valinokam and Ramnad, red dunes are identified and aggregated between ~ 9 to 3 ka. This shows the deltaic evolution period between the late Pleistocene and Holocene and shoreline movement along the seaward side ~ [ to 65 km. This study will be helpful to government agencies like CZM authorities, Harbor development authorities etc.

MENINGKATKAN KESADARAN WISATAWAN DALAM MENJAGA KELESTARIAN EKOSISITEM WISATA PANTAI BAHARI DI KECAMATAN JAWAI SELATAN

One of the tourist attractions that attracts the attention of domestic and foreign tourists is the marine beach in Kec. South Java. Looking at the history of this Marine Tourism Beach, it has been around for a long time, this beach is an empty beach and forest that is not managed or developed, since 2019 one of the residents of Jawai Laut Village has taken the initiative to invite local residents to explore this still beautiful beach and form an awareness group. Marine Tourism Beach tourism which has 52 members. The aim of this background is to increase tourist awareness in preserving the marine coastal tourism ecosystem in the Javai Laut village, Javai sub-district. The methods used in the activity include counseling and discussion. Based on outreach activities at the maritime coast of Jawai Laut Village, Kec. This outreach program conveys information regarding tourist awareness in preserving the marine coastal tourism ecosystem in Jawai Laut village, Jawai sub-district the tourists were very enthusiastic in taking part in the outreach that was carried out.

Cadmium exposure experiments on calanoid copepods reveal significant shortfall in water quality criteria for managing coastal marine ecosystems in West Africa

Cadmium exposure experiments on calanoid copepods reveal significant shortfall in water quality criteria for managing coastal marine ecosystems in West Africa

Changes in threats to macroalgal forests (Cystoseira sensu lato) at three restoration sites in the Mediterranean Sea

Abstract Macroalgal forests, such as Cystoseira sensu lato, comprise crucially important habitats in the Mediterranean Sea, providing protection and structural complexity, enhancing productivity, food, shelter and spawning grounds in coastal marine ecosystems. However, due to increasing direct and indirect anthropogenic impacts, these habitats are rapidly declining. Due to their biological and ecological characteristics, the natural recovery of the populations belonging to these species is slow. For this reason, active restoration has been identified as an effective tool for their recovery. Since the mitigation of impacts is one of the prerequisites for restoration success, Modified Threat Reduction Assessments were used to estimate success of conservation measures in three areas of the central and north‐western Mediterranean Sea (Costa del Conero, Italy; Cala Bona and Port de la Selva, Spain). In particular, the assessment was conducted to: (i) identify and evaluate the changes in threats to Cystoseira s.l. species between 2019 and 2021; and (ii) propose management in relation to the ongoing restoration measures. A total of 13 threats were identified and determined negative Modified Threat Reduction Assessment Indices of approximately −46%, −14% and −13%, respectively, in Costa del Conero, Cala Bona and Port de la Selva. The study's findings, when combined, document the increase of the scale of threats during the second year of the survey period despite the lockdown due to COVID‐19.

Taxonomic and functional diversity of subtidal benthic communities associated with hard substrates at Crozet archipelago (sub-Antarctic, Southern Ocean)

Sub-Antarctic coastal marine ecosystems harbor rich and diverse benthic communities. Despite their ecological uniqueness and vulnerability to global changes, studies on benthic communities remain limited. Using underwater video-imagery, we investigated the taxonomic and functional diversity of benthic communities associated with hard substrates at Baie du Marin (Ile de la Possession, Crozet archipelago). The Baie du Marin species richness and diversity were additively partitioned to evaluate spatial patterns of species through the following spatial scales: within images, among images within transects, and among transects. We analyzed imagery data from seven transects located at different sites inside Baie du Marin and covering contrasting natural rocky habitats and underwater artificial cable substrates. A total of 50 faunal (mainly represented by Echinodermata and Porifera phyla) and 14 algae (mainly represented by Rhodophyta phylum) taxa were identified. Rocky substrates were dominated by high densities of the polychaetes Parasabella sp. and Lanice marionensis, whereas submarine cables were dominated by high densities of the bivalve Kidderia sp. attached to macroalgae. Our results show contrasted distribution patterns in the faunal and algal assemblages within the Baie du Marin, with significant ecological differences between submarine cables and natural rocky substrates. Larger spatial scale (i.e., among transects) accounted for most of the bay richness and diversity, highlighting a high-level of habitat heterogeneity within the bay. Through a trait-based approach, our findings revealed that Crozet benthic communities are characterized by low functional richness, evenness, and redundancy, highlighting a potential vulnerability to current and future natural and anthropogenic changes. This study provides a novel bentho-ecological baseline for future assessments of natural and anthropogenic impacts on the marine environment of the Crozet archipelago; and for the conservation management of these remote habitats that make part of the French Southern Territories Marine Protected Area, recently inscribed on the UNESCO World Heritage list.

Carbon Footprint Reduction and Climate Change Mitigation: A Review of the Approaches, Technologies, and Implementation Challenges

Since the Industrial Revolution, human economic activity and the global development of society in general have been heavily dependent on the exploitation of natural resources. The use of fossil fuels, deforestation, the drainage of wetlands, the transformation of coastal marine ecosystems, unsustainable land use, and many other unbalanced processes of human activity have led to an increase both in the anthropogenic emissions of climate-active gases and in their concentration in the atmosphere. It is believed that over the past ~150 years these phenomena have contributed to an increase in the global average temperature in the near-surface layer of the atmosphere by ~1 °C. Currently, the most pressing tasks facing states and scientific and civil societies are to reduce anthropogenic CO2 emissions and to limit the global air temperature increase. In this regard, there is an urgent need to change existing production systems in order to reduce greenhouse gas emissions and to sequester them. In this review, we consider up-to-date scientific approaches and innovative technologies, which may help in developing roadmaps to reduce the emissions of climate-active gases, control rising temperatures, decarbonize economies, and promote the sustainable development of society in general.

Assessing spatial impacts of historical pulp mill effluent on trophic dynamics in a coastal marine ecosystem using stable isotope (δ13C and δ15N) analysis

Boat Harbour, Nova Scotia was a tidal estuary that was converted into a wastewater treatment facility for pulp mill effluent in 1967. Treated effluent from Boat Harbour was discharged into the coastal Northumberland Strait, contributing significant nutrient and freshwater inputs into the coastal environment, potentially impacting local biogeochemistry and ecosystem structure. This study used stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) of representative taxa to assess spatial variability in nutrient sources and trophic dynamics. Results identified stable isotope variation with depleted δ13C and δ15N values in taxa near Boat Harbour. Blue mussel (Mytilus edulis) and mummichog (Fundulus heteroclitus) were the most suitable bioindicators for identifying variation in nutrient sources. Stable isotope signatures in this study may be reflective of residual pulp mill effluent-derived nutrients, differences in marine versus terrestrial nutrient sources, and a pronounced coastal salinity gradient. The present study defined the baseline nutrient conditions of the Northumberland Strait and will be useful in assessing the effectiveness of remediation activities.

Potential faunal evidence for western epicontinental seaway along the Narmada rift in peninsular India during the latest Cretaceous (Maastrichtian)

The pathways of marine incursions into central India around the Cretaceous-Paleogene (K-Pg) transition are a matter of ongoing debate. While there is a general consensus regarding marine incursions from the southeast coast of India along the Godavari rift, it is still highly controversial as to whether such incursions also took place from the western margin, along the Narmada-Tapti rift. Here we report the first fossil evidence (batoid and pycnodontid fishes) suggesting potential marine influences during the deposition of freshwater Deccan intertrappean sediments (late Cretaceous, Maastrichtian) in the lower Narmada valley of west-central peninsular India. The discovery of several isolated teeth of the stingray genus Igdabatis (I. indicus) along with a pycnodontid tooth in a predominantly freshwater intertrappean section at Mohanpura, district Dhar (Madhya Pradesh state) is significant, especially since living myliobatids are essential inhabitants of coastal marine ecosystems. Similar previously recorded occurrences of Igdabatis and pycnodontids from several other Maastrichtian infra- and intertrappean localities on the eastern and southeastern fringes of the Deccan Volcanic Province have been interpreted as evidence of marine incursions from India's eastern margin along the Godavari rift. The present records from district Dhar tentatively suggest the existence of a nearby epicontinental seaway (the Narmada Seaway) during the Maastrichtian. The Narmada Seaway extended hundreds of kilometres inland from India's western margin, beginning in the late Cenomanian with the deposition of long known Bagh Beds and continuing intermittently until the early Paleocene (Danian, Zone P1a).

Molecular investigation of waterborne protozoan contamination using marine Demospongiae

Sponges play important role within aquatic ecosystems due to their diverse abilities including filter-based feeding mechanisms. Hence, this study evaluated the potential use of sponges as ecological biomonitors for water safety surveillance, especially in the presence of Waterborne protozoan pathogens WBPP. Sponge specimens were collected from different Qatari marine ecosystems and subjected to gDNA extraction and real-time PCR using specific primer sets for the most common WBPP. Two sponges from the coastal marine ecosystems were found to be positive for Blastocystis sp., and one sponge was positive for Dientamoeba fragilis within offshore site. No Cryptosporidium spp., Giardia duodenalis, nor Toxoplasma gondii were detected. Further genotyping analysis revealed that the Blastocystis sp. positive samples were subtype ST3 (allele 34), which matched local clinical isolates and D. fragilis specimen was unambiguously clustering with Genotype 2. In conclusion, this study demonstrates the role of marine sponges as ecological biomonitors for WBPP screening and provide insights into these pathogens widespread and their potential transmission to marine and terrestrial organisms including human.

The combined effects of phenanthrene and micro-/nanoplastics mixtures on the cellular stress responses of the thick-shell mussel Mytilus coruscus

Pollution with complex mixtures of contaminants including micro- and nano-plastics (MNPs) and organic pollutants like polycyclic aromatic hydrocarbons (PAH) poses a major threat to coastal marine ecosystems. Toxic mechanisms of contaminant mixtures are not well understood in marine organisms. We studied the effects of single and combined exposures to polycyclic aromatic hydrocarbon phenanthrene (Phe) and MNPs mixture with sizes of 70 nm, 5 μm and 100 μm on the immune health and oxidative stress parameters in the thick-shell mussel Mytilus coruscus. Immune cells (hemocytes) were more sensitive to the pollutant-induced oxidative stress than the gills. In hemocytes of co-exposed mussels, elevated mortality, lower lysosomal content, high production of reactive oxygen species (ROS) and decrease mitochondrial were found. Disparate responses of antioxidant enzymes in the hemolymph (e.g. increased superoxide dismutase (SOD) activity without a corresponding increase in catalase (CAT) in Phe exposures and an increase in CAT without a change in SOD in MNPs exposures) suggests misbalance of the antioxidant defense in the pollutant-exposed mussels. Gill lacked pronounced oxidative stress response showing a decline in ROS and antioxidant levels. Tissue-specific single and combined effects of Phe and MNPs suggest variation in bioavailability and/or different sensitivity to these pollutants in the studied tissues. Notably, the combined effects of MNPs and Phe were additive or antagonistic, showing that MNPs do not enhance and occasionally mitigate the toxic effects of Phe on the hemocytes and the gills of the mussels. Overall, our study sheds light on the impact of long-term exposure to MNPs and Phe mixtures on mussels, showing high sensitivity of the immune system and modulation of the Phe toxicity by MNPs co-exposure. These findings that may have implications for understanding the impacts of combined PAH and MNPs pollution on the health of mussel populations from polluted coastal habitats.

High Light Intensity and CO2 Enrichment Synergistically Mitigated the Stress Caused by Low Salinity in Pyropia yezoensis

Macroalgae, playing a crucial role in coastal marine ecosystems, are subject to multiple environmental challenges due to tidal and seasonal alterations. In this work, we investigated the physiological responses of Pyropia yezoensis to ocean acidification (ambient CO2 (AC: 400 μatm) and elevated CO2 (HC: 1000 μatm)) under changing salinity (20, 30 psu) and light intensities (50, 100 μmol photons m−2 s−1) by measuring the growth, pigment content, chlorophyll fluorescence, and soluble sugar content. The key results are the following: (1) P. yezoensis exhibited better growth under normal salinity (30 psu) compared to hyposaline conditions (20 psu). (2) Intermediate light intensity increased phycoerythrin content, ultimately enhancing thalli growth without significant changes to the contents of chlorophyll a and carotenoids. (3) Ocean acidification alleviated hyposaline stress by enhancing pigment production in P. yezoensis only at a salinity of 20 psu, highlighting the complex interplay of these environmental factors. These findings indicate that higher light intensities and elevated pCO2 levels could mitigate the stress caused by low salinity.

Influence of marine habitat on microplastic prevalence in forage fish and salmon in the Salish Sea

Microplastics are increasingly prevalent in marine systems and are a growing concern as a marine pollutant and contaminant with consequences for high trophic level consumers, including humans. Given evidence that links plastics to degraded ecosystem functioning and organismal health, there is increased interest in understanding the prevalence, fate and consequences of marine plastics. Microplastics contain and absorb harmful chemicals which may serve as endocrine disruptors and have negative implications for growth, reproductive health, and longevity. To expand current knowledge on microplastics in coastal marine ecosystems and the potential for biomagnification in marine food webs, we conducted stomach analyses of microplastics in Pacific salmon (Oncorhynchus spp.) and Pacific sand lance (Ammodytes personatus), an important prey for salmon. Prevalence of microplastics was substantial; 77 % of all salmon and 25 % of all sand lance stomachs contained at least one microplastic. Fish were sampled at multiple sites throughout the inland Salish Sea, including beaches and sediment bedforms for Pacific sand lance and open-water pelagic habitat for Pacific salmon. Pacific sand lance sampled at beach sites had more microplastics compared to those sampled in subtidal sediments and there were more plastics in sand lance at a protected beach site as compared to an exposed beach site. Prevalence of plastics in salmon differed according to species and included analyses of pink salmon (Oncorhynchus gorbuscha), Chinook (Oncorhynchus tshawytscha), and Coho salmon (Oncorhynchus kisutch); plastics were predominantly fibers in all species, though there were relatively higher rates of ingestion of films and particles in Chinook. Comparisons between plastic concentrations and stomach fullness indicated a slight negative trend, suggesting that plastics may be retained. Further investigation is needed to develop a more thorough understanding of the prevalence and fate of microplastics in coastal marine systems such as the Salish Sea, their concentration within marine food webs, and the implications for species targeted in fisheries.

Temporal change in phytoplankton diversity and functional group composition

One of the key challenges in managing eutrophication in coastal marine ecosystems is the harmonized cross-border assessment of phytoplankton. Some general understanding of the consequences of shifting nutrient regimes can be derived from the detailed investigation of the phytoplankton community and its biodiversity. Here, we combined long-term monitoring datasets of German and Dutch coastal stations and amended these with additional information on species biomass. Across the integrated and harmonized dataset, we used multiple biodiversity descriptors to analyse temporal trends in the Wadden Sea phytoplankton. Biodiversity, measured as the number of species (S) and the effective number of species (ENS), has decreased in the Dutch stations over the last 20 years, while biomass has increased, indicating that fewer species are becoming more dominant in the system. However, biodiversity and biomass did not show substantial changes in the German stations. Although there were some differences in trends between countries, shifts in community composition and relative abundance were consistent across stations and time. We emphasise the importance of continuous and harmonized monitoring programmes and multi-metric approaches that can detect changes in the communities that are indicative of changes in the environment.