Filter-feeding Research Articles

Long-term observations of a sponge in situ reveal a rich repertoire of contractile behaviors, including winter dormancy

Sponges are remarkably active animals with a range of behaviors that are broadly termed sneezes. Little is known about what triggers sneezes or how sneezes propagate in an animal that lacks either muscular or nervous systems. We explored the triggers of sponge behavior in situ in the demosponge Suberites concinnus. The placement of this tennis ball-sized sponge at the focal point of a camera array on an instrument platform in Barkley Sound, BC, Canada, provided a unique opportunity for our investigation. The observatory has a suite of environmental sensors measuring parameters such as photosynthetically active radiation (PAR), oxygen, turbidity, salinity, pressure, current speed, and temperature. An array of 8 cameras designed for 3D imaging was used to capture hourly images. Our findings revealed both long-term (annual) and short-term (daily) behaviors in S. concinnus. The sponge contracted for 2 mo each winter. In February, it gradually expanded and became very active with short-term full-body contractions each lasting 11 h through the summer. A meta-analysis of contraction behaviors in other species of sponge showed that contraction duration is a factor of sponge size and that all sponges contract faster than they expand. Invertebrates and fish were frequently in contact with the sponge, but no single interaction was found to correlate with patterns of sponge behavior. However, significant correlations between sponge behaviors and chlorophyll and turbidity were found using generalized additive mixed models. Our study underscores the dynamic nature of these sessile filter feeders and their responses to their environment.

Feeding strategies and habits of the coral guard‐crab Trapezia bidentata

AbstractThe crab Trapezia bidentata is a conspicuous crustacean characterized as an obligate symbiont with branching corals, such as species of Pocillopora. These crustaceans have been identified as strict corallivores with a feeding dependency on the mucus excreted by adult colonies in the genus Pocillopora. However, like other crustaceans, individuals of T. bidentata have a nutritional plasticity that has not been described. We used an integrative approach, including traditional taxonomy and high‐throughput sequencing of hypervariable region V9 of the 18S rRNA gene, to describe the mouthparts and the diet of individuals of Trapezia bidentata associated with adult colonies of Pocillopora verrucosa. The presence of setae on the ambulatory dactylus and maxillipeds, forming food brushes and combs, was evident. Sequencing and analyses of the intestinal content of the crustaceans found evidence of 18 phyla, mostly represented by Brachiopoda (28.1%), Arthropoda (31.7%), and Cnidaria (21.1%), but also small contributions (≤2%) of other animal groups such as Mollusca, Annelida, and Tunicata. In addition, a few traces (≤0.5%) of algae and fungi were identified. The feeding structures and intestinal content showed that individuals of T. bidentata are omnivorous and behave as suspension feeders and scrapers, obtaining nourishment from tissues transported in the water column and in the mucus and tissue of P. verrucosa. The results provide a clearer characterization of the role of T. bidentata, which is a crucial guard crustacean associated with P. verrucosa. We found both corallivorous and suspension‐feeding habits, which demonstrates feeding plasticity, a positive characteristic for the survival of the species.

New Spheromorphic Problematics Gaparella from the Lower Cambrian of Western Mongolia

From the lower part of the Tommotian Stage of the Lower Cambrian of Western Mongolia, ridge Hevte-Tsakhir-Nuruu described a new problematical sphaeromorhical microfossils Gaparella elenae sp. nov.; a new combination of generic and specific names Gaparella kuanchuanpuensis (Qian, 1977). has been proposed. Despite its very peculiar morphology, the genus Gaparella Missarzhevsky in Missarzhevsky et Mambetov, 1981 is more often mentioned in the list of synonyms of the genus Archaeooides Qian, 1977. The taphonomic variability of Mongolian Gaparella is shown and the morphology is reconstructed: these were hollow spheres, with a perforated double thin wall; between the holes, which were located chaotically on small elevations, a system of canals was developed; the wall may have been organic with an admixture of mineral components. Based on their lifestyle, these fossils were probably planktonic filter feeders. Their level of organization appears to have been consistent with Porifera; most likely these were juvenile forms.

Exploring the Freshwater Cladocera (Pleuroxus spp.) as New Potential Live Feed in Aquaculture

In freshwater lakes, cladocera play a crucial role in the food chain, as they are the primary source of nutrition for nearly all aquatic species. Pleuroxus spp. are very suitable for aquaculture due to their ease of handling, rapid growth, non-selective filter feeder, high nutritional value, and remarkable ability to adapt to many environmental conditions. Silver barbs are in high demand in the aquaculture business due to their excellent flavours and rapid development rate. In this study, Pleuroxus spp. was cultured in a control condition with water quality maintained at the room temperature of 26 ± 1 °C and pH of 7.0 ± 0.5. Five treatments of Pleuroxus spp. were prepared, which comprised of T1 (control) = unfed, T2 = coffee grounds, T3 = corn flour, T4 = wheat flour, and T5 = sugarcane waste. Pleuroxus spp. were fed with a selected diet solutions at a concentration of 0.5 g/L daily. The result shows that Pleuroxus spp. given T3 (24.88 ± 5.48 ind/mL) had a greater population density than T4 (22.13 ± 4.83 ind/mL), T2 (21.06 ± 5.27 ind/mL), and T5 (20.56 ± 4.92 ind/mL) dietary treatments. Pleuroxus spp. given T3 had the greatest survival rate (97.9 ± 9.8%) when compared to other diets, T4 (86.81 ± 19.07%), T2 (82.71 ± 16.56%), and T5 (75.00 ± 21.08%). Silver barb showed the highest amount of daily weight gain in treatment T3 (0.11 ± 0.001 mg/days; p < 0.05) compared with other dietary treatments. The maximum specific growth rate (SGR) (%) was achieved when fed with T3 (13.37 ± 0.02%; p < 0.05). The feed conversion ratio (FCR) was shown to be significantly different (p < 0.05). The FCR of larvae fed with different nutritional treatments ranged from 1.22 to 4.12, depending on the treatment. In comparison to other diets, the T3 treatment (1.22 ± 0.03) achieved the highest FCR ratio. In short, pre-feeding of zooplankton with prospective diets has built a baseline of improved aquaculture feeding procedures that may be employed in the future aquaculture businesses.

Large-scale oyster farming accelerates the removal of dissolved inorganic carbon from seawater in Sanggou Bay

While the direct impact of oyster calcification and respiration on the seawater inorganic carbon system is well-acknowledged, their indirect effect through filter feeding activities remains unclear. Here we studied the impact of large-scale oyster farming on the removal of dissolved inorganic carbon (DIC) from seawater. Field investigations showed that the DIC level in the oyster farming area in Sanggou Bay, China were significantly lower than that in the non-farming area. In-lab incubation showed that regardless of whether incubated in high or low-transparent environments, the DIC removal rate of seawater from the oyster farming area was significantly higher than that of the non-farming area. These results indicate that cultivated oyster facilitates the removal of seawater DIC in the farming area. To reveal the indirect effect of filter feeding activities on DIC removal, we used 6-m3 ponds to simulate the oyster-farming environment. Results showed that the average DIC level of the oyster-cultivating groups was 105.83 μmol/kg lower than that of the control groups (without of oyster) after a six-day cultivation. Surprisingly, the average concentration of Chl-a in oyster-cultivating groups was significantly higher than that of the control group at the end of the experiment. Similarly, DIC level declined faster while Chl-a concentration increased faster in seawater that previously experienced 12～20 hours of oyster cultivation than that in the control seawater. It was noticed that the transparence of seawater within 6-m3 ponds increased significantly just after hours of oyster cultivation. This enhanced transparency created a favorable light environment that supported phytoplankton photosynthesis and simultaneously accelerated the DIC removal rate. Overall, oysters not only remove the inorganic carbon in the seawater through calcification but also create a suitable environment for phytoplankton photosynthesis through their filtering activity, and subsequently accelerating the removal of inorganic carbon in the seawater of the oyster farming area.

What is hidden under our pontoons? Abundance and distribution of filter feeders (bivalves and tunicates) in the port area revealed. Artificial intelligence: an interesting analysis tool?

Urbanization is particularly prevalent along the coast, causing a considerable change in the ecology of the habitats found there. Ports, docks and all the structures linked to this anthropization modify the coastal environment by providing new niches, but also new constraints. Thus, ports are ecosystems in their own right, although they are rarely studied as such. In Europe’s largest marina (La Rochelle, France), among the multitude of organisms inhabiting it, four taxa seem particularly interesting to study: Mytilidae, Ostreïdae, Pectinidae and ascidiacea. Because these taxa, which belong to the bivalve and tunicate groups, are the stewards of the health of the port environment both as bio-indicators and as engineering species. The establishment of a systematic and regular census allows us to study the evolution of their populations and to determine what influences their distribution. To have as less impact as possible on the fauna studied, the census was carried out by underwater photography. The study shows that the populations are partly conditioned by the hydrodynamics of the environment and by the anthropic activity which is carried out there. Indeed, this study, which was carried out in a particular context (before and after the COVID-19 health crisis), shows the importance of anthropic pressure, particularly on the bivalve communities. A large amount of data is needed to understand what precisely governs bivalve and tunicate populations. Therefore, an innovative method, using artificial intelligence to automate the analyses, was tested in this study. This promising method should facilitate the census by reducing the analysis time.

Accumulation and depuration of 4,5-dihydro-KmTx2 from Karlodinium veneficum in the bivalves, Mercenaria mercenaria and Sinonovacula constricta

Bivalves (e.g., clams, oysters, mussels, scallops) are a significant part of the global diet and are harvested for their nutritional value, but as filter feeders they are susceptible to the accumulation of toxins produced by certain species of phytoplankton. Karlotoxins (KmTxs) are a class of amphidinol-like compounds with hemolytic, ichthyotoxic, and cytotoxic properties that have been associated with harmful algal blooms, and the dinoflagellate Karlodinium veneficum uses KmTxs to facilitate prey capture and deter grazing by other organisms. In this work, we examined the accumulation and depuration of 4,5-dihydro-KmTx2, a karlotoxin previously isolated from K. veneficum, in two bivalves with different life habits, i.e., Sinonovacula constricta Lamarck and Mercenaria mercenaria Linnaeus. After both bivalves received K. veneficum GM5 in their feed for a long period of 10 days, 4,5-dihydro-KmTx2 was accumulated considerably in the visceral mass, but there was almost no toxin accumulation in the muscle. The accumulation was more severe for M. mercenaria than S. constricta. The toxin was cleared almost completely from the bivalves 5 days after K. veneficum GM5 was removed from the feed. For both bivalves, the bait microalgae I. galbana slowed both the accumulation and the depuration of the toxin.

Influence of an innovative IMTA system (Mediterranean Sea, Italy) on environmental and biological parameters: Seasonal analysis

The influence of benthic suspension feeders as bioremediating organisms on water column seston and their ability to mitigate fish farm waste was assessed by monthly analyses for one year. A monthly monitoring from July 2020 to October 2021 of physico-chemical and biochemical variables of the water column and the sediment was performed in an in-shore mariculture plant located in the Mar Grande of Taranto (Italy), comparing two adjacent areas that differ in type of farming. The first (reference site) is a fish monoculture, while the second consists of an innovative Integrated Multi-Trophic Aquaculture system (IMTA site). The annual cycle of chlorophyll-a concentration showed values corresponding to mesotrophic/eutrophic conditions, with peak production in early fall (4.64 μg L−1). During the spring and summer sampling times, when the amount of aquaculture waste is greater than during the rest of the year, the reference site showed the highest lipid (151.73 μg L−1) and organic matter (189.00 mg g−1) values with respect to those at the IMTA site. The IMTA bioremediating organisms possibly acted as underwater gardens changing the seston quality and availability and providing protection and food for the zooplankton community, which showed higher abundance of individuals for most sampling times at the IMTA site, peaking during September and October in both 2020 and 2021 (max 232,985.20 ind m−3). Our results demonstrate the effectiveness of the considered IMTA system in mitigating the negative impact of organic matter release into the environment due to fish farming activities. The influence of bioremediating organisms on seston composition and concentration opened up mitigation as well as restoration scenarios.

Bivalve microbiomes are shaped by host species, size, parasite infection, and environment.

Many factors affect an organism's microbiome including its environment, proximity to other organisms, and physiological condition. As filter feeders, bivalves have highly plastic microbiomes that are especially influenced by the surrounding seawater, yet they also maintain a unique core set of microbes. Using 16S ribosomal RNA sequencing, we characterized the bacterial microbiomes of four species of bivalves native to the Mid-Atlantic East Coast of North America: Crassostrea virginica, Macoma balthica, Ameritella mitchelli, and Ischadium recurvum and assessed the impact of their external environment, internal parasites, and size on their microbial communities. We found significant differences in bacterial amplicon sequence variants (ASVs) across species, with each species harboring a core ASV present across all individuals. We further found that some C. virginica co-cultured with I. recurvum had high abundances of the I. recurvum core ASV. We identified ASVs associated with infection by the parasites Perkinsus marinus and Zaops ostreum as well others associated with bivalve size. Several of these ASV are candidates for further investigation as potential probiotics, as they were found positively correlated with bivalve size and health. This research represents the first description of the microbiomes of A. mitchelli, I. recurvum, and M. balthica. We document that all four species have highly plastic microbiomes, while maintaining certain core bacteria, with important implications for growth, health, and adaptation to new environments.

Declining bivalve species and functional diversity along a coastal eutrophication-deoxygenation gradient in the northern Gulf of Mexico

Coastal eutrophication and hypoxia are growing challenges globally, yet their impacts can be difficult to evaluate because of limited biomonitoring that typically postdates the onset of these stressors. We address this limitation by investigating how the taxonomic and functional diversity of marine bivalve communities vary with primary productivity, dissolved oxygen, temperature, and seafloor sediment properties across the northern Gulf of Mexico, a region that includes one of the world's largest dead zones. We hypothesized that taxonomic and functional richness would decline in eutrophic and hypoxic coastal environments. Live bivalve mollusks were sampled at 15 stations, spanning more than 600 km of continental shelf habitat. Individuals were identified to species and characterized based on feeding, mobility, fixation, life position relative to the sediment-water interface, and body size. Alpha and beta taxonomic and functional diversity were computed using Hill numbers and linear models used to assess their covariation with regional environmental conditions. Taxonomic and functional diversity were highest in less eutrophic environments characterized by normoxic conditions, and lowest in more eutrophic environments where oxygen was more limited. Community-level differences were underlain by functional shifts, with abundant shallow-infaunal, deposit and mixed feeders in more eutrophic settings, in contrast with less eutrophic settings where suspension feeders were more abundant. Median body size increased with eutrophication, possibly as a result of hypoxia-induced declines in predator and competitor populations. These results suggest that intensifying nutrient loading and deoxygenation in the coastal zone will cause declines in multiple dimensions of benthic biodiversity with implications for ecosystem function.

Assessment of climate change effect on environmental flows for macroinvertebrates using an integrated hydrological-hydraulic-habitat modelling

Study regionA short reach of the Jeziorka river and its upstream catchment in central Poland Study focusClimate change is expected to have significant impacts on freshwater ecosystems, particularly on temperate region streams resulting often in changes to spatiotemporal distribution of macroinvertebrate species, as well as losses in richness and aquatic biodiversity due to the loss of suitable habitat. This study aimed to evaluate the impact of climate change on the habitat suitability and environmental flow violations for the filter feeder functional group of macroinvertebrate communities in a temperate lowland river in central Poland. To achieve this, we have successfully integrated hydrological (SWAT+), hydraulic (HEC-RAS 1D and SRH-2D), and habitat (CASiMiR) models. We have forced the model cascade with GCM/RCM projections to determine changes in future habitat conditions for a selected reach of the Jeziorka river. New hydrological insights for the regionFuture habitat conditions may deteriorate, as reflected in overwhelmingly negative trends in the hydraulic habitat suitability (HHS) index. According to the projections, there will be fewer days with the necessary environmental flows for filter feeders in the future. The frequency and duration of environmental flow violations, caused by too low or too high flows, depend on the climate model scenarios and timeframes. Our findings will aid water resource planners in achieving sustainable water resource management and meeting environmental flow requirements in the face of a changing climate.

What is happening to the European Union aquaculture production? Investigating its stagnation and sustainability

While global aquaculture production has been highly successful in terms of production growth in recent decades, most developed countries including the European Union (EU) have not participated in this development to a significant extent. As recently as the 1970s, several EU countries were global leaders in aquaculture production, primarily focusing on filter feeders such as mussels and oysters. However, aquaculture production in the EU has largely stagnated over the past few decades. Despite political support, investment and research efforts over the last three decades, environmental regulations and competition with other activities have slowed down or even halted production growth in many cases. Recent EU legislation aimed at boosting food security and sustainable food systems, recognise aquaculture as a major potential contributor, focusing for example on sustainable or low environmental impact aquaculture, e.g. the production of low trophic level species. In this context, this article aims to contribute to the understanding of the EU aquaculture sector by examining the stagnation in production and its causes. We investigate the evolution of the EU aquaculture production in weight and value, as well as its average trophic level, length and diversity of the species produced. Results indicate an increase in the diversity of species produced, but a decline in the production of low trophic level species over the last two decades, and an increase in more challenging high trophic levels species, raising the overall average trophic level of the production. The decline in mussel and oyster production is mainly due to environmental and, to a lesser degree, economic factors. The rapid growth of carnivorous fish, such as seabream, seabass and salmon has slowed down since 2000, mainly due to regulations aiming at limiting environmental impacts.

Identification of Benthic Foraminifera Presence in The Marginal Environments of Biliran Island, Philippines.

Benthic foraminifera are unicellular marine micro-organism with a hard exoskeleton and commonly present in the benthic community of marine ecosystem. This study aimed to identify the benthic foraminifera present along the coastal areas of eight municipalities in Biliran Island, Philippines. Quadrat sampling was conducted and three samples per quadrant transect of 1 m × 1 m divided into nine squares were collected. The samples were then observed under the microscope, and the specimens seen were identified by comparing them with the images of the sample species from the website https://marinespecies.org/. The researchers conducted an in-situ collection of the foraminiferal shells from intertidal areas along shallow water coastlines of the island. Results showed that the coastal environment of Biliran Island has the presence of the genera Spirillina, Quinqueloculina, Marginopora and Sorites. The identified species were classified based on their feeding mechanisms as herbivory and passive suspension feeding. The presence of benthic foraminifera species along the coastal environments of Biliran Island provides a record of the environment where they are found, making them natural bioindicators of water quality. This study provides a baseline for further studies on the distribution and abundance of benthic foraminifera in the area and can contribute to the understanding of the environmental conditions of the coastal areas in Biliran Island.

Unravelling the Brachidontes variabilis species complex (Bivalvia: Mytilidae) of the Indo-Pacific region

ABSTRACT Members of the radially ribbed mytilid genus Brachidontes are often dominant filter feeders on hard intertidal substrata in the Indo-Pacific region. However, there is still a great deal of uncertainty and confusion over their species identities, taxonomy and phylogenetic relationships. At least six species names (crebristriatus, karachiensis, mutabilis, pharaonis, ustulatus and variabilis) have at one time or another been synonymized with each other and applied to these common intertidal mussels. They occur widely across the Indian and Pacific Oceans from East Africa to Hawaii. Our results, based on sequences of five genes and anatomical features, suggest there are at least eight closely related sibling species in three monophyletic clades: (1) Brachidontes variabilis-form A in the western Indian Ocean; (2) Brachidontes pharaonis in the Red Sea; (3) Brachidontes variabilis-form B, found from India to East Asia; (4) Brachidontes mutabilis, restricted to southern Japan and China; (5) Brachidontes crebristriatus, in the Indian Ocean through to Southeast Asia and Hawaii; (6) Brachidontes ustulatus, an endemic species in western and southern Australia; (7) Brachidontes maritimus, so far known only from Hawaii; and (8) Brachidontes erosus, a southern Australian endemic. The latter two species form a small clade (Clade 1) that is sister to two larger Clades 2 and 3, each comprising three species. Clade 2 contains Brachidontes crebristriatus, Brachidontes mutabilis and Brachidontes ustulatus, whilst Clade 3 is made up of Brachidontes pharaonis, Brachidontes variabilis-form A and variabilis-form B. The shells of these eight species are not only variable but can greatly overlap in morphology. Many are also nearly impossible to distinguish without geographical information. However, the absence or presence of plicate organs in the mantle cavity, and the shape of guard papillae lining the inhalant aperture, may serve as important diagnostic morphological characters when used alongside geographical provenance.

Ediacaran-type non-mineralized tube-dwelling organisms persisted into the early Cambrian (Terreneuvian) in Baltica

The Ediacaran taxon Conotubus hemiannulatus has been discovered in the Terreneuvian blue clays of Estonia. Alongside Conotubus, Gaojiashania-like tubes are also found in these clays. These tubes are fully compressed and pyritized. The well-developed peristomes of Conotubus might have provided stability if the living worm was partially buried in the soft sea floor, suggesting that Conotubus was a sessile suspension feeder. The presence of the archaic Conotubus hemiannulatus in the Fortunian of Estonia indicates that the tube morphology of some cloudinids did not change between the Ediacaran and the Terreneuvian. The existence of these old-fashioned cloudinids in the Terreneuvian suggests either that the early Cambrian ecosystem in Baltica was not significantly different from that of the Ediacaran, or that cloudinids with organic tubes were more resilient to ecological changes than previously thought. Most Terreneuvian faunas originate from lower latitudes, whereas Baltica, during the Terreneuvian, was located at middle-high latitudes and experienced a cold climate. We hypothesize that the cold climate zone ecosystem was more archaic in the Fortunian than the tropical ecosystem, providing a final refuge for the Ediacaran non-mineralized tubicolous organisms. The increased competition pressure from diverse modern animals in the tropics could have driven Ediacaran-type non-mineralized tubicolous organisms to seek refuge in the colder regions of the ocean, where the competition from more advanced animals was less intense.

Comparison of water quality, planktonic community, and volatile organic compounds in the seawater from five cage culture areas of large yellow croaker

The rapid development of marine fish cage farming has led to ecological damage, adversely affecting fish quality. Significant regional quality differences in large yellow croaker under similar farming conditions suggest that the water environment plays a crucial role in fish quality. Using full-length18s/16 s rRNA sequencing with bacterial absolute quantity and headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC–MS), we investigated the planktonic community and volatile organic compounds (VOCs) in seawater from cages housing large yellow croaker at five major mariculture sites in China, including ND (26.627°E, 119.638°N), NJ (27.479°E, 121.052°N), DT (27.981°E, 121.196°N), NC (28.470°E, 121.907°N), and DJ (30.198°E, 122.698°N). Notably, three dominant ciliates, Mesodinium rubrum, Strombidium sp., and Pseudotontonia simplicidens, were identified in NJ as bioindicators for water quality. Additionally, NJ cages had the highest bacterial biomass with 54 % Synechococcus CC9902, and the lowest abundance of bacteria with pathogenic activities. These may explain NJ's optimal water quality parameters and the highest eukaryotic biodiversity. In contrast, DT and DC contained only the core ciliate M. rubrum, with no dominant ciliate in ND. Styela gibbsii, a filter feeder, predominated in ND cages, adhering to the net. The occurrence of red tide-causing species and pathogenic bacteria or fungi was notable in DJ, DC, DT, and ND, including Akashiwo sanguinea, an unclassified Dinophyceae, Gyrodinium fusiforme, Pirum gemmate, Candida parapsilosis, Hortaea werneckii, and Pseudomonas juntendi. Bacterial functional analysis showed that ND cages harbored unique strains linked to ureolysis and various pathogenic activities. Co-association networks suggested that 2,4-Di-tert-butylphenol and pentadecane might play roles in communication within plankton communities. A rise in pleasant VOCs such as acetyl valeryl, pentadecane, butyl butyrate, tetradecane, and 5-butyldihydro-2(3H)-furanone was observed in DJ, DC, DT, and NJ, compared to ND. The results provide valuable insights for improving aquaculture practices and mitigating environmental impacts. The results provide valuable bioindicators for monitoring water quality using microbial communities and VOC profiles.

Functional traits and ecosystem implications in the Multiple Use Marine Protected Area Almirantazgo Sound: A baseline study of scallop banks and benthic communities

Amid escalating environmental challenges confronting marine ecosystems, the proliferation of coastal and marine protected areas (MPAs) has emerged as a pivotal strategy for mitigating biodiversity loss and fostering sustainable resource management. This research advocates for a paradigm shift towards a trait-based approach to assess functional diversity (FD) within MPAs, with a specific focus on the ecologically crucial Austrochlamys natans banks in Parry Bay, MPA Almirantazgo Sound. By surveying 28 invertebrate species across eight phyla, a PCA using fuzzy-coded functional traits revealed five distinct groupings primarily based on feeding, movement, and reproductive modes. Mobile predators and scavengers clustered distinctly from sessile suspension feeders and limited-mobility grazers, indicating a scarcity of mobile predator species in Parry Bay, which impacts the ecosystem's dynamics. FD indices highlighted low functional α-diversity, emphasizing trait redundancy that enhances resilience but relies heavily on a few unique and specialized species. The potential extinction or migration of these species could directly affect unique ecosystem properties. While revealing the resilience of the benthic community, this research underscores its dependence on a handful of species that are crucial for both ecological functions and regional commercial significance. Urgent conservation and management measures are imperative to protect these species and maintain the delicate balance of this ecosystem.

Lactiplantibacillus plantarum 299V fermented in microcapsules shows enhanced stability and could improve the microbial quality and safety of oysters through bioaccumulation.

In this study, microcapsules of Lactiplantibacillus plantarum 299V were prepared using an emulsification/internal gelation technique. Loads of the probiotics were condensed to 9.86±0.13logCFU/g after 24h fermentation of the microcapsules. Physical characterization revealed that L. plantarum 299V cells were uniformly distributed within the core of the microcapsules, with a mean diameter of 109.81±0.39µm and a span value of 0.36±0.00, which were comparable to those of the unfermented microcapsules (p>0.05). The viability of L. plantarum 299V in the fermented microcapsules was 2.08±0.15log higher than that of free cells at the end of 5h simulated gastrointestinal digestion (p<0.05). Oysters were able to accumulate the fermented microcapsules through filter feeding, resulting in a load of probiotics exceeding 6.00logCFU/g. The presence of L. plantarum 299V-carrying microcapsules in oyster tissues significantly suppressed spoilage-causing bacteria during 11 days refrigeration storage, suggested by the tested parameters, including total psychrotrophic bacteria, H2S-producing bacteria, and Pseudomonas spp. (p<0.05). Pathogenic bacteria, including Vibrio parahaemolyticus and Salmonella enterica artificially introduced into oysters, were also significantly suppressed by over 1.00-log within 4 days compared to control samples (p<0.05). In summary, oysters bioaccumulated with fermented L. plantarum 299V-carrying microcapsules, justified a novel probiotic-carrying product to exsert the health-promoting effect of probiotics. This solution could also enhance the microbial quality and safety of oysters during storage.

Silicon balance in an integrated multi-tropical aquaculture ecosystem, Sanggou Bay, China

Farmed aquaculture species play an important role in regulating nutrient cycles in farming systems. Compared with nitrogen and phosphorus, the role of farmed species in the silicon (Si) cycle remains poorly understood. To help reduce this uncertainty, we clarified the sources and sinks of silicate and quantified the Si pools in an aquaculture system in Sanggou Bay (SGB). The results showed that dissolved inorganic nutrient levels were significantly lower during the dry season than during the wet. Dissolved silicate (DSi) is a potential limiting factor for phytoplankton growth during spring, and phosphorus limitation occurs during summer. The budget results indicated that large amounts of nitrogen, phosphate (DIP), and DSi were buried in the sediment or transformed into other forms during both the wet and dry seasons. The nitrogen and DIP cycles were strongly influenced by bivalve excretion and farmed species harvesting; however, these processes had little impact on the Si cycle. Si availability depends on both external inputs and internal recycling. DSi was primarily supplied from the Yellow Sea, with a minor contribution from the river due to river discharge during spring. However, during summer, riverine inflow (accounting for 83% of the total influx) was the major DSi source followed by benthic flux (12%). Biogenic silica (BSi) burial efficiency in the sediment was estimated to be 78% during spring and 23% during summer. The BSi preservation efficiency in bivalves during spring was high (53%), leading to a higher Si retention than in river discharge. Bivalves biodeposition plays an important role in the Si burial process. We suggest that this high retention is essentially controlled by the biodeposition mechanism, which is directly controlled by the exotic suspension feeders. Bivalves have the potential to alter Si retention in the bay by producing large amounts of biodeposits and accelerating the silica cycle, which may lead to more carbon dioxide being absorbed by diatoms.

Cell differentiation controls iron assimilation in a choanoflagellate.

Marine microeukaryotes have evolved diverse cellular features that link their life histories to surrounding environments. How those dynamic life histories intersect with the ecological functions of microeukaryotes remains a frontier to understand their roles in essential biogeochemical cycles1,2. Choanoflagellates, phagotrophs that cycle nutrients through filter feeding, provide models to explore this intersection, for many choanoflagellate species transition between life history stages by differentiating into distinct cell types3-6. Here we report that cell differentiation in the marine choanoflagellate Salpingoeca rosetta endows one of its cell types with the ability to utilize insoluble ferric colloids for improved growth through the expression of a cytochrome b561 iron reductase (cytb561a). This gene is an ortholog of the mammalian duodenal cytochrome b561 (DCYTB) that reduces ferric cations prior to their uptake in gut epithelia7 and is part of an iron utilization toolkit that choanoflagellates and their closest living relatives, the animals, inherited from a last common eukaryotic ancestor. In a database of oceanic metagenomes8,9, the abundance of cytb561a transcripts from choanoflagellates positively correlates with upwellings, which are a major source of ferric colloids in marine environments10. As this predominant form of iron11,12 is largely inaccessible to cell-walled microbes13,14, choanoflagellates and other phagotrophic eukaryotes may serve critical ecological roles by first acquiring ferric colloids through phagocytosis and then cycling this essential nutrient through iron utilization pathways13-15. These findings provide insight into the ecological roles choanoflagellates perform and inform reconstructions of early animal evolution where functionally distinct cell types became an integrated whole at the origin of animal multicellularity16-22.