Filter-feeding Invertebrates Research Articles

Preliminary Assessment of Macrobenthos Associated with Red Coral Corallium rubrum (Linnaeus, 1758) Populations in the Northeastern Ionian Sea

The taxonomic composition, structure, and distribution patterns of the macrobenthos associated with Corallium rubrum were studied along the coast of Taranto (Ionian Sea), together with the main features of their red coral population. Underwater video transects were performed by professional divers at three sites in correspondence with coralligenous formations at depths from 50 to 65 m. The results revealed a patchy distribution of red coral, with colonies predominantly located in cavities on sub-vertical cliffs and large boulders. Biometric analysis indicated that young colonies predominated at all sites, while older colonies were lacking, likely because of illegal harvesting. The lower density values were recorded at S1, while S2 and S3 presented higher values. A total of 76 taxa were recorded. S1, the shallowest site, showed a prevalence of calcareous algae, while S2 and S3 showed a greater abundance of filter-feeding invertebrates (Porifera and Cnidaria) with the highest presence of Porifera at S3. The results emphasize the heterogeneity of the macrobenthos together with the high vulnerability of the red coral population, highlighting the necessity of site-specific conservation strategies to contribute to the conservation and management of benthic ecosystems in the northern Ionian Sea.

Selection of marine bacterial consortia efficient at degrading chitin leads to the discovery of new potential chitin degraders.

Chitin degradation is a keystone process in the oceans, mediated by marine microorganisms with the help of several enzymes, mostly chitinases. Sediment, seawater, and filter-feeding marine invertebrates, such as sponges, are known to harbor chitin-degrading bacteria and are presumably hotspots for chitin turnover. Here, we employed an artificial selection process involving enrichment cultures derived from microbial communities associated with the marine sponge Hymeniacidon perlevis, its surrounding seawater and sediment, to select bacterial consortia capable of degrading raw chitin. Throughout the artificial selection process, chitin degradation rates and the taxonomic composition of the four successive enrichment cultures were followed. To the best of our knowledge, chitin degradation was characterized for the first time using size exclusion chromatography, which revealed significant shifts in the numbered average chitin molecular weight, strongly suggesting the involvement of endo-chitinases in the breakdown of the chitin polymer during the enrichment process. Concomitantly with chitin degradation, the enrichment cultures exhibited a decrease in alpha diversity compared with the environmental samples. Notably, some of the dominant taxa in the enriched communities, such as Motilimonas, Arcobacter, and Halarcobacter, were previously unknown to be involved in chitin degradation. In particular, the analysis of published genomes of these genera suggests a pivotal role of Motilimonas in the hydrolytic cleavage of chitin. This study provides context to the microbiome of the marine sponge Hymeniacidon perlevis in light of its environmental surroundings and opens new ground to the future discovery and characterization of novel enzymes of marine origin involved in chitin degradation processes.IMPORTANCEChitin is the second most abundant biopolymer on Earth after cellulose, and the most abundant in the marine environment. At present, industrial processes for the conversion of seafood waste into chitin, chitosan, and chitooligosaccharide (COS) rely on the use of high amounts of concentrated acids or strong alkali at high temperature. Developing bio-based methods to transform available chitin into valuable compounds, such as chitosan and COS, holds promise in promoting a more sustainable, circular bioeconomy. By employing an artificial selection procedure based on chitin as a sole C and N source, we discovered microorganisms so-far unknown to metabolize chitin in the rare microbial biosphere of several marine biotopes. This finding represents a first important step on the path towards characterizing and exploiting potentially novel enzymes of marine origin with biotechnological interest, since products of chitin degradation may find applications across several sectors, such as agriculture, pharmacy, and waste management.

Physiological and molecular effects of contaminants of emerging concerns of micro and nano-size in aquatic metazoans: overview and current gaps in Antarctic species.

Although Antarctica is the most isolated continent on Earth, its remote location does not protect it from the impacts of human activities. Antarctic metazoans such as filter-feeding invertebrates are a crucial component of the Antarctic benthos. They play a key role in the benthic-pelagic carbon flux in coastal areas by filtering particles and planktonic organisms from the sediment-water interface. Due to their peculiar ecological niche, these organisms can be considered a wasp-waist in the ecosystem, making them highly sensitive to marine pollution. Recently, anthropogenic particles such as micro-nanoplastics and manufactured nanoparticles (MNP) have been classified as contaminants of emerging concern (CEC) due to their small size range, which also overlaps with the preferred particle size ingested by aquatic metazoans. Indeed, it has been demonstrated that some species such as Antarctic krill can ingest, transform, and release MNPs, making them newly bioavailable for other Antarctic filter-feeding organisms. Similarly, the production and use of anthropogenic MNP are rapidly increasing, leading to a growing presence of materials, such as nano-sized metal-oxides, in the environment. For these reasons, it is important to provide evidence of the adverse effects of such emerging contaminants at sub-lethal concentrations in environmental risk assessments. These contaminants may cause cascade effects with consequences not only on individuals but also at the community and ecosystem levels. In this review, we discuss the state-of-the-art knowledge on the physiological and molecular effects of anthropogenic MNP in Antarctic aquatic metazoans. We further highlight the importance of identifying early biomarkers using sessile metazoans as sentinels of environmental health.

Polyester Microfibers Exposure Modulates Mytilus galloprovincialis Hemolymph Microbiome.

Microplastic (MP) contamination in the aquatic environment is a cause of concern worldwide since MP can be taken up by different organisms, altering different biological functions. In particular, evidence is accumulating that MP can affect the relationship between the host and its associated microbial communities (the microbiome), with potentially negative health consequences. Synthetic microfibers (MFs) represent one of the main MPs in the marine environment, which can be accumulated by filter-feeding invertebrates, such as bivalves, with consequent negative effects and transfer through the food chain. In the mussel Mytilus galloprovincialis, polyethylene terephthalate (PET) MFs, with a size distribution resembling that of an MF released from textile washing, have been previously shown to induce multiple stress responses. In this work, in the same experimental conditions, the effects of exposure to PET-MF (96 h, 10, and 100 μg/L) on mussel hemolymph microbiome were evaluated by 16S rRNA gene amplification and sequencing. The results show that PET-MF affects the composition of bacterial communities at the phylum, family and genus level, with stronger effects at the lowest concentration tested. The relationship between MF-induced changes in hemolymph microbial communities and responses observed at the whole organism level are discussed.

Insights on long-term ecosystem changes from stable isotopes in historical squid beaks

BackgroundAssessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023.ResultsWe detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii’s trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century.ConclusionsOur results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids’ increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.

Microcystins in the benthic food-web of the Sacramento-San Joaquin Delta, California

Harmful cyanobacteria blooms are a growing threat in estuarine waters as upstream blooms are exported into coastal environments. Cyanobacteria can produce potent toxins, one of which—hepatotoxic microcystins (MCs)—can persist and accumulate within the food web. Filter-feeding invertebrates may biomagnify toxins up to 100× ambient concentrations. As such, bivalves can be used as an environmentally relevant and highly sensitive sentinel for MC monitoring. To date there has been little research on cyanotoxin bioaccumulation in estuaries. The Sacramento-San Joaquin Delta (Delta) aquatic food web has undergone a profound change in response to widespread colonization of aquatic invasive species such as Asian clams (Corbicula fluminea) in the freshwater portion of the Delta. These clams are prolific—blanketing areas of the Delta at densities up to 1000 clams/m2 and are directly implicated in the pelagic organism decline of threatened and endangered fishes. We hypothesized that Asian clams accumulate MCs which may act as an additional stressor to the food web and MCs would seasonally be in exceedance of public health advisory levels. MCs accumulation in Delta Asian clams and signal crayfish (Pacifastacus leniusculus) were studied over a two-year period. ELISA and LC-MS analytical methods were used to measure free and protein-bound MCs in clam and crayfish tissues. We describe an improved MC extraction method for use when analyzing these taxa by LC-MS. MCs were found to accumulate in Asian clams across all months and at all study sites, with seasonal maxima occurring during the summer. Although MC concentrations rarely exceeded public health advisory levels, the persistence of MCs year-round still poses a chronic risk to consumers. Crayfish at times also accumulated high concentrations of MCs. Our results highlight the utility of shellfish as sentinel organisms for monitoring in estuarine areas.

Biodegradation of polypropylene by filter-feeding marine scallop Mizuhopecten yessoensis: infrared spectroscopy evidence

The problem of environmental pollution by plastics is global in nature and needs to be addressed as soon as possible. Realization of the importance of this problem contributed to the study of degradation and biodegradation of synthetic polymers. It turned out that the driving force of plastic fragmentation along with abiotic factors can be biotic. Based on the above, we investigated the in vitro biodegradation of polypropylene (PP) fragments in digestive gland homogenates and crystalline styles of the bivalve mollusk Mizuhopecten yessoensis. Fourier transform infrared spectroscopy showed changes in the chemical composition of functional groups on the plastic surface. Enzyme complexes of crystalline styles enhanced the biodegradation of PP fragments to a larger extent than did digestive glands. The results obtained using M. yessoensis as an example suggest that marine phytophagous filter-feeding invertebrates may accelerate the biodegradation of synthetic polymers. The study provides a basis for rethinking the nature of relationships between marine invertebrates and microplastic polluting the marine environment.

Oxygen Extraction Efficiency and Tolerance to Hypoxia in Sponges

Sponges have always been filter feeders, in contrast to all the other filter-feeding invertebrate groups for which this feeding mode is a secondary adaptation. This study calls attention to this aspect, which explains why sponges are tolerant to hypoxia, but probably not more tolerant than the other filter-feeding invertebrates. The measurement of respiration rates at decreasing oxygen concentrations along with an estimation of the oxygen extraction efficiency in the marine demosponge Halichondria panicea have been used to understand why sponges are tolerant to low oxygen concentrations. It was found that the respiration rate was constant down to about 1.5 mL O2 L−1, which shows that the extraction efficiency increases with a decreasing oxygen concentration. It is argued that the relationship between the filtration rate and oxygen consumption in filter feeders is controlled by the resistance to the diffusion of oxygen across the boundary layer between the feeding current and the tissues of the body. A high tolerance to hypoxia is a consequence of the adaptation to filter feeding, and sponges do not have a special capacity to overcome hypoxic events.

Food acquisition by the intertidal filter feeder bivalve Perumytilus purpuratus: Can the gill explain a differential performance between smaller individuals and the larger ones?

The intertidal zone represents a challenging environment for filter-feeding marine invertebrates. Smaller individuals are more prone to intertidal stressors than their larger conspecific; thus, reaching refuge sizes is crucial for their survival. There is no clear consensus about the morphological adaptations that small filter-feeding individuals may use to compensate for its greater mass-specific metabolic requirement relative to that of a larger conspecific. Food acquisition in filter-feedings is not only determined by the gill size but also by the efficiency of particle retention and transport rate; trade-offs between these variables may explain why smaller individuals are more efficient at acquiring energy. In this study, we examined the mechanisms underlying feeding responses in relation to body size in the intertidal suspension-feeding bivalve Perumytilus purpuratus. Clearance rate, flow rate, particle transport rate, and gill cilia development were compared over a range of sizes (7–35 mm shell length). Our results showed that small individuals possess a gill activity that makes them more efficient at collecting and transporting food particles than their larger conspecifics. Water flow rate, clearance rate, and particle transportation throughout the gill were higher per standardized gill area in smaller than larger individuals. Although the gill filaments are not all fully developed in smaller individuals, the old filaments are functional in capturing and transporting particles, which makes them more efficient per gill area than larger specimens. Taken together, we demonstrated that juveniles of P. purpuratus are more efficient than their adult conspecifics in terms of feeding capacity.

Spatial compartmentalisation of bacteria in phoronid microbiomes

The phylum Phoronida comprises filter-feeding invertebrates that live in a protective tube sometimes reinforced with particulate material from the surrounding environments. Animals with these characteristics make promising candidate hosts for symbiotic bacteria, given the constant interactions with various bacterial colonizers, yet phoronids are one of the very few animal phyla with no available microbiome data whatsoever. Here, by sequencing the V4 region of the 16S rRNA gene, we compare bacterial microbiomes in whole phoronids, including both tube and living tissues, with those associated exclusively to the isolated tube and/or the naked animal inside. We also compare these communities with those from the surrounding water. Phoronid microbiomes from specimens belonging to the same colony but collected a month apart were significantly different, and bacterial taxa previously reported in association with invertebrates and sediment were found to drive this difference. The microbiomes associated with the tubes are very similar in composition to those isolated from whole animals. However, just over half of bacteria found in whole specimens are also found both in tubes and naked specimens. In conclusion, phoronids harbour bacterial microbiomes that differ from those in the surrounding water, but the composition of those microbiomes is not stable and appears to change in the same colony over a relatively short time frame. Considering individual spatial/anatomical compartments, the phoronid tube contributes most to the whole-animal microbiome.

Phylogeographic and Morphological Analysis of Botrylloides niger Herdman, 1886 from the Northeastern Mediterranean Sea

Botrylloides niger (class Ascidiacea) is an invasive marine filter-feeding invertebrate that is believed to originate from the West Atlantic region. This species of colonial tunicate has been observed in several locations along the coasts of Israel and around the Suez Canal, but it has not yet been reported on the coasts of the Northeastern Mediterranean Sea (NEMS), suggesting an ongoing Lessepsian migration. However, the extent of this invasion might be concealed by reports of other potentially misidentified species of Botrylloides, given that the strong morphological similarities within this genus renders taxonomical identification particularly challenging. In this study, we performed a phylogeographic and morphological analysis of B. niger in the NEMS. We collected 238 samples from 8 sampling stations covering 824 km of the coastlines of NEMS. We reported 14 different morphotypes, of which the orange-brown, orange, and brown-striped morphs were the most abundant. Using the mitochondrial cytochrome C oxidase I (COI) as a DNA barcode marker, we identified 4 haplotypes. The COI haplotypes clustered with the reference B. niger sequences from GenBank and differed significantly from the sister Botrylloides species. We confirmed our identification using three additional barcoding markers (Histone 3, 18S rRNA, and 28S rRNA), which all matched with over 99% similarity to reference sequences. In addition, we monitored a station for a year and conducted a temporal analysis of the collected colonies. The colonies were absent during the winter and spring, while new colonies were established in the summer and expanded during autumn. We performed demographic population analysis on our spatial data that identified a possible population subdivision at a sampling site, which might have been caused by local freshwater input. Herein, we present the first report on the presence of Botrylloides niger in the NEMS. This study represents a key step toward understanding the diversity and the propagation of this highly invasive species of colonial ascidians, both within the Mediterranean basin as well as globally.

Filter-Feeding Pacific Lamprey (Entosphenus tridentatus) Ammocetes Can Reduce Suspended Concentrations of E. coli Bacteria

Filter-feeding invertebrates such as bivalves have been shown to improve the health of aquatic systems by reducing concentrations of bacteria and other harmful suspended organisms, but it remains unknown if microphagous suspension-feeding fishes can provide similar ecosystem services for water quality. Here, we tested whether the presence of the filter-feeding larval ammocoete life-stage of Pacific lamprey (Entosphenus tridentatus) can reduce suspended concentrations of Escherichia coli bacteria. Aquaria containing either filter-feeding ammocoete lamprey larvae (1.5 fish·L−1), lamprey macropthalmia juveniles (1.5 fish·L−1) that do not suspension-feed, or no lamprey (control) were filled with water contaminated with E. coli bacteria and then monitored for 5 d for E. coli concentration changes in the water column. The presence of ammocoete larvae generated a significantly faster decline in E. coli abundance compared to aquaria containing either macropthalmia-stage lamprey or no fish, which showed similar E. coli concentration profiles over that 5 d period. A higher density of ammocoetes (4.3 fish·L−1) resulted in a more rapid decline in E. coli compared to the lower 1.5 fish·L−1 ammocoete density, further implying that ammocoetes augmented bacterial clearance. These observations provide evidence that filter-feeding larval ammocoetes of Pacific lamprey may help promote water-quality enhancement by reducing suspended bacterial concentrations.

Assessing the utility of marine filter feeders for environmental DNA (eDNA) biodiversity monitoring.

Aquatic environmental DNA (eDNA) surveys are transforming how marine ecosystems are monitored. The time-consuming preprocessing step of active filtration, however, remains a bottleneck. Hence, new approaches that eliminate the need for active filtration are required. Filter-feeding invertebrates have been proven to collect eDNA, but side-by-side comparative studies to investigate the similarity between aquatic and filter-feeder eDNA signals are essential. Here, we investigated the differences among four eDNA sources (water; bivalve gill-tissue; sponges; and ethanol in which filter-feeding organisms were stored) along a vertically stratified transect in Doubtful Sound, New Zealand using three metabarcoding primer sets targeting fish and vertebrates. Combined, eDNA sources detected 59 vertebrates, while concurrent diver surveys observed eight fish species. There were no significant differences in alpha and beta diversity between water and sponge eDNA and both sources were highly correlated. Vertebrate eDNA was successfully extracted from the ethanol in which sponges were stored, although a reduced number of species were detected. Bivalve gill-tissue dissections, on the other hand, failed to reliably detect eDNA. Overall, our results show that vertebrate eDNA signals obtained from water samples and marine sponges are highly concordant. The strong similarity in eDNA signals demonstrates the potential of marine sponges as an additional tool for eDNA-based marine biodiversity surveys, by enabling the incorporation of larger sample numbers in eDNA surveys, reducing plastic waste, simplifying sample collection, and as a cost-efficient alternative. However, we note the importance to not detrimentally impact marine communities by, for example, nonlethal subsampling, specimen cloning, or using bycatch specimens.

Leucothoid amphipod and terebellid polychaete symbiosis with description of a new species of the genus Leucothoe Leach, 1814 (Crustacea: Amphipoda: Leucothoidae)

The order Amphipoda is one of the largest orders in the Crustacea, many species of which are involved in symbiotic relations with other animals. Despite the considerable diversity of the Amphipoda both in number of species and ecology, polychaete-commensalism has been poorly known and described from few species. In particular, there has been little discussion of the evolutionary origins of polychaete-commensalism relationships. Amphipods in the family Leucothoidae are known as commensal inhabitants of filter-feeding invertebrates, where they utilize the feeding current produced by their hosts. Leucothoids are typically found from three types of filter-feeding hosts: sponges, ascidians, and bivalve molluscs. Relatively little is known about leucothoids that associate with other types of hosts. An undescribed species of the genus Leucothoe associated with burrows of terebellid polychaetes from Japan has been found. We herein describe this species as Leucothoe vermicola sp. nov., providing COI mtDNA and 18S rDNA sequences for DNA barcoding. This is the first record of a symbiotic association between Leucothoidae and Terebellidae. We also provide a hypothesis of the phylogenetic position of L. vermicola sp. nov. and evolution of the polychaete-commensalism in this species. The polychaete-commensalism in the present new species may have resulted from the entry of generalist species into polychaete hosts, rather than from host-conversion from a specialist species. http://zoobank.org/urn:lsid:zoobank.org:pub:4EBA42DD-EC19-4278-B712-8BEFBC519F8F

Size-Specific Growth of Filter-Feeding Marine Invertebrates

Filter-feeding invertebrates are found in almost all of the animal classes that are represented in the sea, where they are the necessary links between suspended food particles (phytoplankton and free-living bacteria) and the higher trophic levels in the food chains. Their common challenge is to grow on the dilute concentrations of food particles. In this review, we consider examples of sponges, jellyfish, bryozoans, polychaetes, copepods, bivalves, and ascideans. We examine their growth with the aid of a simple bioenergetic growth model for size-specific growth, i.e., in terms of dry weight (W), µ = (1/W) dW/dt = aWb, which is based on the power functions for rates of filtration (F ≈ Wb1) and respiration (R ≈ Wb2). Our theory is that the exponents have (during the evolution) become near equal (b1 ≈ b2), depending on the species, the stage of ontogeny, and their adaptation to the living site. Much of the compiled data support this theory and show that the size-specific rate of growth (excluding spawning and the terminal phase) may be constant (b = 0) or decreasing with size (b < 0). This corresponds to the growth rate that is exponential or a power function of time; however, with no general trend to follow a suggested 3/4 law of growth. Many features are common to filter-feeding invertebrates, but modularity applies only to bryozoans and sponges, implying exponential growth, which is probably a rather unique feature among the herein examined filter feeders, although the growth may be near exponential in the early ontogenetic stages of mussels, for example.

A Novel Approach to Bio-Friendly Microplastic Extraction with Ascidians

Microplastic pollution in water is now recognized as a devastating problem by many organizations, such as the National Oceanic and Atmospheric Administration, with recent studies estimating that the average American consumes around 52,000 of these plastic, toxic particles a year. A successful solution for the extraction of microplastics from oceans must be feasible to be implemented on a large scale and bio-friendly to not further disrupt the environment. To this end, the efficacy of using filter feeders (Ascidians) as biofilters to reduce microplastic pollution was explored. The efficacy of this filtration method was evaluated by adding ascidians to saltwater tanks contaminated with microplastics (experimental group) and comparing the water’s plastic concentration over time against a control. Water samples were then systematically tested with a fluorescence-activating microscope and fluorescent scanner. Fluorescent microplastics were used which allowed for the collection of both quantitative and qualitative data. The samples from the experimental group demonstrated a 24.7% (29.64mg) reduction in microplastics within the first day and a 94.7% (113.64mg) decrease by day 4. The control group showed negligible deviation in microplastic concentration. It is concluded that the Ascidians filtered microplastics from water through their natural feeding and respiratory process. We extrapolate that a 1m x 1m x 1m cage of Ascidians would filter approximately 300g of microplastics every day. This research demonstrates that microplastic filtration with invertebrate filter feeders is an effective and feasible option for extracting microplastics from polluted water.

Actual and Model-Predicted Growth of Sponges—With a Bioenergetic Comparison to Other Filter-Feeders

Sponges are one of the earliest-evolved and simplest groups of animals, but they share basic characteristics with more advanced and later-evolved filter-feeding invertebrates, such as mussels. Sponges are abundant in many coastal regions where they filter large amounts of water for food particles and thus play an important ecological role. Therefore, a better understanding of the bioenergetics and growth of sponges compared to other filter-feeders is important. While the filtration (pumping) rates of many sponge species have been measured as a function of their size, little is known about their rate of growth. Here, we use a bioenergetic growth model for demosponges, based on the energy budget and observations of filtration (F) and respiration rates (R). Because F versus dry weight (W) can be expressed as F = a1Wb1 and the maintenance respiratory rate can be expressed as Rm = a2Wb2, we show that if b1~ b2 the growth rate can be expressed as: G = aWb1, and, consequently, the weight-specific growth rate is µ = G/W = aWb1−1 = aWb where the constant a depends on ambient sponge-available food particles (free-living bacteria and phytoplankton with diameter < ostia diameter). Because the exponent b1 is close to 1, then b ~ 0, which implies µ = a and thus exponential growth as confirmed in field growth studies. Exponential growth in sponges and in at least some bryozoans is probably unique among filter-feeding invertebrates. Finally, we show that the F/R-ratio and the derived oxygen extraction efficiency in these sponges are similar to other filter-feeding invertebrates, thus reflecting a comparable adaptation to feeding on a thin suspension of bacteria and phytoplankton.

Comparative Food Web Analysis of Two Peruvian Bay Systems Along a Latitudinal Gradient: Resource Use and the Environmental Envelope

The coast of Peru lies within the tropics under the influence of the cold, nutrient-rich waters of the Humboldt Current and the interannual onslaught of the El Niño phenomenon. The Peruvian upwelling system is exceptionally productive and is comprised of subsystems at different scales along the coast. We aimed to understand the differences between two shallow coastal systems along a latitudinal gradient: Sechura Bay in the north (at the convergence of Humboldt and tropical waters) and Independencia Bay in the central-south (under typical upwelling conditions). We compared their biodiversity, trophic dynamics, community energetics, resource use and underlying abiotic conditions. Our analysis revealed that over the past two decades, Sechura has shown a warming trend, while Independencia has maintained its cold water conditions. Chlorophyll concentrations have risen significantly in both systems, higher values in Sechura suggesting there is an increase in local pressures that could lead to eutrophication. Trophic models of the La Niña 07/08 period revealed that both systems are bottom-up driven with high biomass and production at the lower trophic levels, though top-down controls were also shown, particularly in Sechura. While primary productivity was similar in both systems, differences were found in the structure and size of energy flows. More cycling and higher transfer efficiency were found in Independencia, where phytoplankton-based food chains played the main role in the overall dynamic. In contrast, the detritus food chain appears to be more relevant for energy flow in Sechura. Differences in biota and flow structure relate to the systems’ environmental conditions, i.e., more diverse warm-water species in the north and mostly cold water adapted species (mainly invertebrate filter-feeders and their predators) in the central-south. Catches in both systems were dominated by the diving fisheries and comprised mostly scallops (bottom-cultured), snails and fish in Sechura, and mussels, clams, crabs and fish in Independencia. Overall, system indicators suggest that Sechura is a comparatively less developed system. Independencia shall likely maintain its general highly productive system features, whereas Sechura will continue to be more frequently disturbed by El Niño and ongoing human-driven activities, reducing its overall stability and functionality. In the context of climate change, acknowledging these differences is essential for future adaptive management regimes.

The benefits of living together – studying marine symbioses to discover enzymes for biotechnology applications

Over the past 50 years, more than 15 pharmaceuticals derived from marine organisms have come to the market. Most of these come from filter-feeding invertebrates that contain a high proportion of microbial symbionts. Microbiology and molecular genetic studies have shown that many of these drug-like compounds are produced by the microbial symbiont. The enzymes that produce these compounds are promiscuous meaning they can process a diverse range of related substrates, making them extremely attractive to the biotechnology industry. Determining the structure of these enzymes makes them amenable to engineering, allowing them to process non-natural substrates. Using this approach, synthetic substrates can be treated with a cocktail of enzymes to prepare focused libraries of compounds to hit drug targets such as protein–protein interactions. These targets are involved in a range of diseases from cancer to immune disorders and are hard to modulate using small molecule drugs. Complex modified cyclic peptides produced using a chemoenzymatic process may be a promising approach to address these disease conditions.

Studying Tunicata WBR Using Botrylloides anceps.

Tunicates are marine filter-feeding invertebrates that can be found worldwide and which are the closest phylogenetic group to the vertebrates (Craniata). Of particular interest, colonial tunicates are the only known chordates that can undergo Whole-Body Regeneration (WBR) via vascular budding. In Botrylloides anceps, a fully functional adult regenerates from a fragment of the vascular system in around 2weeks after amputation. In this chapter, we present protocols to collect B. anceps colonies, confirm their species, breed them in the lab, monitor WBR and perform histological staining on cryosections.