Suspension-feeding Invertebrates Research Articles

Ecologically significant shallow-water (0–30 m) marine animal forests in central New Zealand

Marine animal forests are habitats formed by dense aggregations of suspension-feeding invertebrates that are increasingly being recognised as biodiversity hotspots with key roles in ecosystem functioning. Despite being found across the world, these ecologically important ecosystems remain understudied in temperate seas. Furthermore, while temperate animal forests are typically associated with deeper water, they can also occur in the shallows (< 30 m). This study is the first to describe the diversity of shallow-water (0–30 m) marine animal forests in the Wellington Region of New Zealand using a combination of SCUBA, ROVs, and citizen science surveys. Through qualitative and quantitative surveys, we identified nine distinct biotic communities dominated by sessile invertebrates, including sponges, cnidarians, bivalves, brachiopods, and polychaetes. In Wellington Harbour, the most common communities were sponge beds formed by the massive sponge Suberites australiensis, often occurring with other sponges, the brachiopod Magasella sanguinea, and the bivalve Atrina zelandica. The S. australiensis beds occurred between 7 and 17 m, with densities up to 19 sponges per m2 and specimens up to 40 cm in diameter. Based on pumping rate measurements, we estimated the average filtration capacity of S. australiensis in the sponge beds to range between 1240 and 19,996 L m−2 day−1. Along Wellington’s open coasts, diverse sponge gardens were dominated by massive morphologies, such as Ecionema alata, together with fan, and branching sponges between 20 and 30 m deep. Community composition varied spatially, likely due to heterogeneity in currents, sedimentation, and food availability. Anthropogenic impacts on animal-dominated ecosystems in the harbour included widespread marine debris (e.g., plastics, fishing gear, and tyres), and substrate alteration from coastal development. The open-coast communities were comparatively undisturbed but might be vulnerable to anchoring and fishing activities. Our study revealed ecologically important marine animal forests in the shallow waters of Wellington, which are largely unprotected urban ecosystems. Conservation through mapping, monitoring, and strategic marine spatial planning is urgently needed to preserve these underappreciated biodiversity hotspots worldwide.

Dietary analysis of three important mariculture species in South Korea using DNA metabarcoding in fecal samples

Knowledge of dietary composition is crucial for understanding the trophic ecology of a mariculture species and the available food in aquafarms, which is fundamental for assessing ecosystem health status and determining ecological response to ecosystem variation to develop a better management plan for marine farming. For suspension-feeding invertebrates, the growth and development rely heavily on the availability and quality of phytoplankton. However, their growth rate can be severely impacted by food deficiency or exposure to harmful algae blooms (HABs) and pathogenic parasites, which are major causes of mass mortality in mariculture. This study aimed to conduct a dietary analysis of three important mariculture species — Magallana gigas, Halocynthia roretzi, and Mizuhopecten yessoensis — on three farms in South Korea using DNA metabarcoding. Sequence processing and filtering generated 304 validated amplicon sequence variants from six fecal samples, taxonomically identifying 15 phyla, 18 classes, 32 orders, 39 families, 43 genera, and 46 species. The DNA recovery of Dinoflagellata was predominantly detected in all fecal samples, followed by Apicomplexa, Bacillariophyta, and Ciliophora. Of the three mariculture species, the fecal assemblage of M. gigas exhibited the highest richness and diversity, with a high read proportion of phytoplankton (specifically Dinoflagellata), while such proportions were relatively low in the M. yessoensis samples. Excessive read proportions of parasites (Apicomplexa) were detected in the fecal samples of two H. roretzi, indicating a possible link to as substantial decrease in H. roretzi production observed in South Korea. A total of 27 key species were detected in six fecal samples, including a high read proportion of Prorocentrum triestinum, which is responsible for HABs in Korean coastal waters. These results emphasize the potential of fecal DNA metabarcoding in the genetic monitoring of aquaculture farms/ecosystems and could be a useful reference for develop effective management plans to guarantee sustainable mariculture production.

The Blob marine heatwave transforms California kelp forest ecosystems

Ocean warming has both direct physiological and indirect ecological consequences for marine organisms. Sessile animals may be particularly vulnerable to anomalous warming given constraints in food acquisition and reproduction imposed by sessility. In temperate reef ecosystems, sessile suspension feeding invertebrates provide food for an array of mobile species and act as a critical trophic link between the plankton and the benthos. Using 14 years of seasonal benthic community data across five coastal reefs, we evaluated how communities of sessile invertebrates in southern California kelp forests responded to the “Blob”, a period of anomalously high temperatures and low phytoplankton production. We show that this event had prolonged consequences for kelp forest ecosystems. Changes to community structure, including species invasions, have persisted six years post-Blob, suggesting that a climate-driven shift in California kelp forests is underway.

Filtration Rate of the Solitary, Pleated Tunicate Styela plicata on the Brown Tide-Forming Pelagophytes Aureoumbra lagunensis and Aureococcus anophagefferens

Recurring brown tide algal blooms of the pelagophyte Aureoumbra lagunensis in the northern Indian River, Mosquito, and Banana River lagoons on the Atlantic coast of central Florida, USA, have resulted in marked ecological impacts. Recent studies have investigated whether suspension feeding invertebrates could contribute to top-down control of these and other bloom-forming phytoplankton. While most studies focused on the effects A. lagunensis has on on bivalve filter feeding in the Indian River Lagoon, this study focused on feeding by the solitary pleated tunicate Styela plicata. Hourly filtration rates (FR) of individual S. plicata were measured after exposure to 5.0 x 105 cells mL–1 of either A. lagunensis or another pelagophyte Aureococcus anophagefferens. The latter species has not been observed in Florida estuaries but can also inhibit feeding. Tisochrysis lutea, an alga commonly used as feed in aquaculture was used as a control. Differences in hourly FR of either brown tide species compared to the control alga were statistically significant (p &amp;lt; 0.0001). Mean hourly FR of tunicates exposed to Aureoumbra lagunensis ranged from -282 mL hr−1 to 542 mL hr−1, whereas tunicates exposed to the control species Tisochrysis lutea had FR from 285 mL hr−1 to 2648 mL hr−1. Mean hourly FR of tunicates exposed to Aureococcus anophagefferens ranged from 343 mL hr−1 to 593 mL hr−1 compared to tunicates exposed to T. lutea which ranged from 600 mL hr−1 to 2482 mL hr−1. Further, to test whether cell density and a longer exposure time affected FR, individual S. plicata were initially exposed to cell densities of 103, 104, or 105 cells mL–1 of either A. lagunensis or T. lutea (control) for 24 hours. Subsequent measurement of hourly FR and showed cell density removal was not significantly different (p = 0.28 and 0.77, respectively). These results add to the body of literature on how organisms in the Indian River Lagoon filter-feeder community respond to brown tide exposure. The pleated tunicate may be an additional species contributing to top-down control of these bloom-forming microalgae.

Small suspension-feeding amphipods play a pivotal role in carbon dynamics around offshore man-made structures

The establishment of artificial hard substrates (i.e. offshore wind farms and oil and gas platforms) on marine soft sediments increases the available habitat for invertebrate communities that would otherwise be restricted to natural hard bottoms. Suspension feeding invertebrates clear a significant amount of particles from the water column and release organic matter in the form of feces, influencing the basis of marine food webs and affecting surrounding environments. Artificial structures in the southern North Sea are dominated by a suspension-feeding crustacean in terms of abundance and sometimes even biomass: the amphipod Jassa herdmani. Animal densities of this tiny biofouler are known to exceed 1 million individuals per m2. Despite their small body sizes and their simple filter apparatus, we hypothesized that J. herdmani is a highly effective suspension feeder with a significant impact on neighboring communities due to its high abundances. In a feeding experiment, individuals of J. herdmani were provided with either an algal or an animal diet under two different temperature regimes. Clearance rates and fecal-pellet carbon (FPC) were measured. The results revealed high clearance rates and subsequent FPC, which were more pronounced at the higher temperature. Furthermore, clearance rates and FPC varied insignificantly with different food items. We further used the current findings for upscaling calculations to the total number of offshore windfarms and oil and gas platforms in the southern North Sea. Our calculations indicated that J. herdmani alone clears 0.33–4.71 km3 water per year in the southern North Sea. At the same time, these amphipods release 255–547 tons of carbon per year by means of defecation, thus enriching the surrounding soft sediments with organic matter. Our study highlights that tiny amphipods can mediate indirect effects of man-made structures in the North Sea, which could have a profound impact on pelagic and benthic habitats.

Making Use of Relicts: Brisingid Seastars Aggregate on Hydrothermally Inactive Sulfide Chimneys Near Black Smokers

When hydrothermal activity ceases at black-smoker chimneys on mid-ocean ridges, populations of associated invertebrates hosting chemoautotrophic endosymbionts decline and then disappear, but the chimneys can persist on the seabed as relicts. Suspension-feeding brisingid seastars colonize hydrothermally inactive (relict) chimneys on the East Pacific Rise (EPR), though their distribution relative to available hard substrata and proximity to hydrothermal activity is poorly documented. In this study, brisingid abundance on sulfide and basalt substrata was assessed along an ∼3,700 m ROV Jason II transect at the summit of Pito Seamount (SE Pacific; ∼2,275 m). Brisingids were non-randomly distributed, with highest densities (up to ∼300 m–2) on relict sulfides chimneys near active black smokers. Brisingids were relatively uncommon on basalt substrata, and absent on black smokers. We infer that both relict sulfide structures and proximity to black smokers play key roles in the maintenance of dense brisingid populations on Pito Seamount and in similar environments on the EPR. Our observations suggest that experimental introduction of “artificial” relict chimneys providing microtopographic relief could test whether such an approach might mitigate potential impacts of mineral extraction on populations of suspension-feeding invertebrates.

Experimental demonstration of exclusively passive feeding in the sea-turtle barnacle Chelonibia testudinaria (Linnaeus, 1758) (Cirripedia: Coronulidae)

Abstract Barnacles are sessile suspension feeders whose feeding efficiency and behavior is largely determined by the movement of water through their environment. Barnacles expend energy to feed actively in environments with low flow velocity, whereas they may feed passively at higher flow velocities, which is more efficient than active feeding. Many intertidal barnacles have been shown to switch between active and passive feeding modes as water velocities change, but little is known about the behavior of epibiotic species attached to mobile hosts, which are exposed to more consistent feeding currents. To assess the response of epibiotic barnacles to flow, laboratory-reared sea-turtle barnacles, Chelonibia testudinaria (Linnaeus, 1758), were subjected to a wide range of water velocities in both the presence and absence of food particles. Their behaviors were video-recorded and categorized using an automated behavior recognition algorithm compiled in R. Individuals of C. testudinaria only displayed passive feeding behavior, but did not feed at lowest test velocities. This species fed most at flow velocities between 25 cm s–1 and 40 cm s–1 (linear mixed effects model, F = 19.30, P &amp;lt; 0.001), a range that correlates well with the average swimming speed of two common host species, the loggerhead and green sea turtles, on which C. testudinaria resides. Chelonibia testudinaria displayed longer average feeding durations when food particles were absent than when food was abundant (linear mixed effects model, F = 11.76, P = 0.001), a result that is in line with the expectations of optimal foraging theory for suspension-feeding invertebrates. Lack of active feeding in this species may have evolved following the establishment of its epibiotic nature and may make this obligate epibiotic species entirely reliant on its hosts’ movements to provide a feeding current. This is the only barnacle species known to not facultatively switch between active and passive feeding modes.

Early development of two species of Spirobranchus Blainville, 1818 (Polychaeta: Serpulidae) from the Southern Mexican Pacific

ABSTRACT Species of the genus Spirobranchus are sessile polychaetes with an important role in marine ecosystems since they are suspension-feeding invertebrates. However, for most species almost nothing is known about their early and larval development, so we describe the early development of two species of Spirobranchus from the Southern Mexican Pacific. The early trochophore larva of S. incrassatus was formed 12 h post-fertilization at 28°C and was described up to a 24-day-old metamorph, whilst it was only possible to follow S. cf. corniculatus to the eight-day-old early trochophore larva. With this study, we describe the early embryological stages, which provide an understanding of the reproductive biology of these polychaetes. Furthermore, this type of information is the basis for future experimental work on the possible response of embryos and larvae to changes in environmental variables, such as temperature.

Importance of benthic-pelagic coupling in food-web interactions of Kakinada Bay, India

Benthic components occupy the sediment layer of aquatic ecosystems and play a definitive role in overall system functioning and maintenance. The exchange of inorganic and organic materials between the sediment and water column through benthic-pelagic coupling plays a very important role especially in shallow water ecosystems. It is facilitated mainly by trophic interactions between the benthic and pelagic food webs, or specifically, between the coupling links i.e. the nodes that participate in coupling. Aquatic ecosystem models incorporating benthic food web in details have been few. In the present study, a food web model incorporating both benthic and pelagic food webs has been developed using EcoPath with EcoSim software, for Kakinada Bay ecosystem of Coastal Andhra Pradesh, India and has been analysed to get an idea about this system's functioning and integrity. Hypothetical perturbation scenarios (perturbation of biomass of two important benthic components – microphytobenthos and suspension feeding invertebrates) were applied to the model to study the effects of these two components on overall system robustness and integrity. The analysis of the base model revealed that while the bay system has not yet attained maturity, it also does not face much stress. While the system saw a decline in maturity with increase in microphytobenthos (MPB) biomass, increase in biomass of suspension feeding invertebrate (SFI) resulted in the exact opposite. Study of SFI biomass perturbation scenario also highlighted its role in coupling. Modelling studies incorporating benthic components as separate groups have been few. This work aims to provide a better insight into how benthic components may affect the whole system. Information regarding system health and resilience provided by such models can also be used as guidelines for fishery management and policy making.

Acute effects of back-to-back hurricanes on the underwater light regime of a coral reef

Some of the best-known disturbances affecting coral reefs are storms, yet their impacts on light are poorly known. Here, we describe the underwater light on a reef off St. John, US Virgin Islands (18°18′37.04N, 63°43′23.17W), during two hurricanes and multiple tropical waves that occurred between 17 August 2017 and 30 November 2017. Photosynthetically active radiation (PAR) was recorded at 19-m depth and at the surface, and rainfall was measured as a cause of turbidity affecting underwater light. Hurricanes Irma and Maria reduced maximum daily underwater photosynthetic photon flux density (PPFD) to < 14 µmol photons m−2 s−1 (< 0.001% of surface PPFD) and, from 1 September to 30 November, were associated with rainfall that was higher (107 cm) than has been recorded over this period since 1972. These reductions in underwater PPFD are unprecedented since at least 2014, and the corresponding values of the diffuse attenuation coefficients (Kd-PAR 0.268–0.426) are among the lowest recorded on a coral reef. Our study reveals the capacity for hurricanes to render a photic habitat temporarily aphotic, and over 69 days (and relative to 2016), to contribute to a 20% reduction in summed, daily integrated underwater PPFD. Large reductions in underwater PPFD have negative implications for photosynthetic taxa, but through the turbidity that reduces underwater light, they create opportunities for population growth by suspension feeding invertebrates.

Characterisation of the biofouling community on a floating wave energy device

Wave energy devices are novel structures in the marine environment and, as such, provide a unique habitat for biofouling organisms. In this study, destructive scrape samples and photoquadrats were used to characterise the temperate epibenthic community present on prototypes of the Pelamis wave energy converter. The biofouling observed was extensive and diverse with 115 taxa recorded including four non-native species. Vertical zonation was identified on the sides of the device, with an algae-dominated shallow subtidal area and a deeper area characterised by a high proportion of suspension-feeding invertebrates. Differences in species composition and biomass were also observed between devices, along the length of the device and between sampling dates. This research provides an insight into the variation of biofouling assemblages on a wave energy device as well as the potential technical and ecological implications associated with biofouling on marine renewable energy structures.

Mussels blow rings: Jet behavior affects local mixing

AbstractBenthic suspension feeders such as dreissenid mussels (Dreissena polymorpha and D. rostriformis bugensis) are often found in remarkably dense aggregations (i.e. &gt; 105 mussels m− 2), which is surprising, given their high clearance rates and limited mixing within the benthic boundary layer. Results from flow visualization in flow chamber experiments indicate that there is indeed limited mixing around mussel aggregations at low flows and that siphonal jets can increase mixing around and above these aggregations. Using particle image velocimetry (PIV) to further investigate the underlying hydrodynamics of these jets, we characterized differences in velocity and vorticity among four siphonal behaviors (e.g., slow flux, streaming, exhalant jets, and inhalant jets), including both continuous and pulsatile jets, the latter of which generate free vortex rings. Incorporating these hydrodynamic characteristics into a computational fluid dynamic (CFD) model revealed that siphonal jets increased mixing, expressed as vertical diffusivity in the benthic boundary layer. These differences were most pronounced at slow vs. fast cross‐stream velocities, but those differences diminished several body lengths (i.e. 10−1 m to 10−2 m) downstream. The results from PIV measurements and CFD modeling suggest that benthic suspension feeders can influence patterns of local mixing, which would affect mass transport and biogeochemical processes in the near‐bed region. This underscores the need for physical‐biologically linked models to incorporate the behavior of benthic suspension feeding invertebrates.

CAMBIOS HISTORICOS EN LA DISTRIBUCIÓN Y ABUNDANCIA DE PRADERAS DE PASTOS MARINOS EN LA BAHÍA DE CARTAGENA Y AREAS ALEDAÑAS (COLOMBIA)

The spatial distribution of seagrass beds within the Cartagena Bay and neighboring areas was reconstructed through comparative analyses of maps, aerial photographs and satellite imagery, as well as observations in the field for five time periods within the last six decades. From slightly more than 1,000 hectares of seagrass beds existing in 1935-45, only 76 remained in 2001, which is less than 8%. The loss rate of seagrass within the bay showed an inverse exponential pattern, whereas outside of the bay the tendency was linear. The almost disappearance of this community was probably raged by the reopening of the Canal del Dique early in the thirties, causing the introduction of important amounts of turbid freshwater and sediments into the bay, and subsequently accelerated by the rapid development of the industrial zone, spilling of polluted industrial and domestic waters, dredging and coastal development. The reduction of seagrass areas has been seemingly accompanied by changes in the structure of the animal community, becomig apparent through the evident disappearance of suspension feeding invertebrates which were so far dominant elements three decades earlier. The loss of seagrass beds in the bay during the 20th century seems likely to be part of the long lasting human transformation process of this ecosystem, which started three centuries before.

Trophic versus structural effects of a marine foundation species, giant kelp (Macrocystis pyrifera).

Foundation species create milieus in which ecosystems evolve, altering species abundances and distribution often to a dramatic degree. Although much descriptive work supports their importance, there remains little definitive information on the mechanisms by which foundation species alter their environment. These mechanisms fall into two basic categories: provision of food or other materials, and modification of the physical environment. Here, we manipulated the abundance of a marine foundation species, the giant kelp Macrocystis pyrifera, in 40×40-m plots at Mohawk Reef off Santa Barbara, California and found that its biomass had a strong positive effect on the abundance of bottom-dwelling sessile invertebrates. We examined the carbon (C) stable isotope values of seven species of sessile invertebrates in the treatment plots to test the hypothesis that this positive effect resulted from a nutritional supplement of small suspended particles of kelp detritus, as many studies have posited. We found no evidence from stable isotope analyses to support the hypothesis that kelp detritus is an important food source for sessile suspension-feeding invertebrates. The isotope composition of invertebrates varied with species and season, but was not affected by kelp biomass, with the exception of two species: the tunicate Styela montereyensis, which exhibited a slight enrichment in C stable isotope composition with increasing kelp biomass, and the hydroid Aglaophenia sp., which showed the opposite effect. These results suggest that modification of the physical habitat, rather than nutritional subsidy by kelp detritus, likely accounts for increased abundance of sessile invertebrates within giant kelp forests.

Utilization of organic matter by invertebrates along an estuarine gradient in an intermittently open estuary

In intermittently open estuaries, the sources of organic matter sustaining benthic invertebrates are likely to vary seasonally, particularly between periods of connection and disconnection with the ocean and higher and lower freshwater flows. This study investigated the contribution of allochthonous and autochthonous primary production to the diet of representative invertebrate species using stable isotope analysis (SIA) during the austral summer and winter (2008, 2009) in an intermittently open estuary on the south-eastern coast of Australia. As the study was conducted towards the end of a prolonged period of drought, a reduced influence of freshwater/terrestrial organic matter was expected. Sampling was conducted along an estuarine gradient, including upper, middle and lower reaches and showed that the majority of assimilated organic matter was derived from autochthonous estuarine food sources. Additionally, there was an input of allochthonous organic matter, which varied along the length of the estuary, indicated by distinct longitudinal trends in carbon and nitrogen stable isotope signatures along the estuarine gradient. Marine seaweed contributed to invertebrate diets in the lower reaches of the estuary, while freshwater/terrestrial organic matter had increased influence in the upper reaches. Suspension-feeding invertebrates derived large parts of their diet from freshwater/terrestrial material, despite flows being greatly reduced in comparison with non-drought years.

Methods, Mechanisms and Typical Bio-Indicators of Engineered Nanoparticle Ecotoxicology: An Overview

As nanotechnology industries increase production, increased release of engineered nanoparticles (NPs) to aquatic environments suggests a rising need for monitoring and evaluation of their potential toxicity. Based on previous and latest research results in the related field, this paper reviews methods, mechanisms, and typical bio-indicators of nanomaterials ecotoxicological research. It outlines detecting methods of NPs in ecotoxicologial studies, and discusses suspension methods of nanoparticles in this field. Proteomics and genomics technologies are predicted to be indispensable means in ecotoxicological studies of NPs. It also points out that biology of particle-induced oxidative stress is an important mechanistic paradigm, and so are solvent effects and the effects of NPs on other substances. Typical bio-indicators in aquatic systems are claimed to be determined to avoid unnecessary animal testing whenever possible and to reduce unnecessary testing costs. In ecotoxicological research of NPs, fish species are generally considered as preferred species; for nanoparticle ecotoxicity, suspension-feeding invertebrates may be a unique target group, therefore invertebrate testing is also very important; because of sensitivity to pollutants, phytoplankton testing should be strengthened. This paper also summarizes some conflicting results in current experiments, and gives some possible explanations. Finally, future research directions are proposed.

In vivo effects of n-TiO2 on digestive gland and immune function of the marine bivalve Mytilus galloprovincialis

Due to the increasing production of nanoparticles (NPs) and their potential release in the aquatic environment, evaluation of their biological impact on aquatic organisms represents a major concern. Suspension feeding invertebrates, in particular bivalve mollusks, may play a role in NP biotransformation and transfer through food webs and may represent a significant target for NP toxicity.In this work, the in vivo effects of titanium dioxide (n-TiO2), one of the most widespread NPs in use, were investigated in the bivalve Mytilus galloprovincialis, largely utilised as a sentinel for marine contamination. Mussels were exposed for 96h to different concentrations of n-TiO2 suspensions (1, 10 and 100μgL−1) and multiple responses were evaluated in the digestive gland and immune cells, the haemocytes. In the digestive gland, n-TiO2 affected lysosomal and oxidative stress biomarkers and decreased transcription of antioxidant and immune-related genes. In the haemocytes, n-TiO2 decreased lysosomal membrane stability-LMS and phagocytosis, increased oxyradical production and transcription of antimicrobial peptides; moreover, pre-apoptotic processes were observed. The effects of n-TiO2 on digestive gland and haemocytes were distinct, also depending on the endpoint and on nominal NP concentrations, with many significant responses elicited by the lowest concentrations tested. The results show that n-TiO2, at concentrations close to predicted environmental levels, significantly affected different functional and molecular parameters of mussel digestive gland and immune cells. In particular, the observed changes in immune parameters that represent significant biomarkers of exposure at the organism level suggest that exposure to n-TiO2 may pose a serious risk to mussel health.

Interactions among sea otters, sea stars, and suspension-feeding invertebrates in the western Aleutian archipelago

The structuring and organizing effects of apex predators on ecosystems are becoming increasingly well documented. The enhancement of kelp forests via sea otter predation on herbivorous sea urchins is among the earliest and best known examples. This study provides evidence for direct and indirect trophic interactions among sea otters, predatory sea stars, and filter-feeding mussels (Mytilus trossulus) and barnacles (Semibalanus cariosis). In western Massacre Bay at Attu Island (173°E, 53°N), subtidal transects showed sea star body size and biomass density declined markedly between 1983 and 1994 as sea otters reinhabited this area. Mussels and barnacles translocated from the rocky intertidal zone to shallow subtidal habitats to assess loss rates from sea star predation showed lower mortality rates after the arrival of sea otters. Prey mortality rates in subtidal caged controls were consistently low and similar to those of intertidal controls in both years. These findings elucidate a trophic pathway by which sea otters can influence ecosystems separate from the well-known sea otter/sea urchin/macroalgae cascade.

Immunomodulation by different types of N-oxides in the hemocytes of the marine bivalve Mytilus galloprovincialis.

The potential toxicity of engineered nanoparticles (NPs) for humans and the environment represents an emerging issue. Since the aquatic environment represents the ultimate sink for NP deposition, the development of suitable assays is needed to evaluate the potential impact of NPs on aquatic biota. The immune system is a sensitive target for NPs, and conservation of innate immunity represents an useful basis for studying common biological responses to NPs. Suspension-feeding invertebrates, such as bivalves, are particularly at risk to NP exposure, since they have extremely developed systems for uptake of nano and microscale particles integral to intracellular digestion and cellular immunity. Evaluation of the effects of NPs on functional parameters of bivalve immunocytes, the hemocytes, may help understanding the major toxic mechanisms and modes of actions that could be relevant for different NP types in aquatic organisms.In this work, a battery of assays was applied to the hemocytes of the marine bivalve Mytilus galloprovincialis to compare the in vitro effects of different n-oxides (n-TiO2, n-SiO2, n-ZnO, n-CeO2) chosen on the basis of their commercial and environmental relevance. Physico-chemical characterization of both primary particles and NP suspensions in artificial sea water-ASW was performed. Hemocyte lysosomal and mitochondrial parameters, oxyradical and nitric oxide production, phagocytic activity, as well as NP uptake, were evaluated. The results show that different n-oxides rapidly elicited differential responses hemocytes in relation to their chemical properties, concentration, behavior in sea water, and interactions with subcellular compartments. These represent the most extensive data so far available on the effects of NPs in the cells of aquatic organisms. The results indicate that Mytilus hemocytes can be utilized as a suitable model for screening the potential effects of NPs in the cells of aquatic invertebrates, and may provide a basis for future experimental work for designing environmentally safer nanomaterials.

Resource specialisation among suspension-feeding invertebrates on rock walls in Fiordland, New Zealand, is driven by water column structure and feeding mode

Resource specialisation among suspension-feeding invertebrates on rock walls in Fiordland, New Zealand, is driven by water column structure and feeding mode