Pelagic Filter Feeders Research Articles

Abundance and distribution of microplastics in benthic sediments and Cladocera taxa in a subtropical Austral reservoir.

Pollution of the natural environment by microplastics has become a global issue in ecosystems as it poses a potential long-term threat to biota. Microplastics can accrue in high abundances in sediments of aquatic ecosystems while also contaminating pelagic filter feeders, which could transfer pollutants up trophic webs. We assess the abundance and distribution of microplastics in benthic sediments and Cladocera taxa in a subtropical Austral reservoir using a combination of geospatial techniques, physicochemical analyses, diversity indices, and multivariate statistics between two seasons (i.e., hot-wet and cool-dry). We found particularly high densities of microplastics during the cool-dry season for both sediments (mean 224.1 vs. 189 particles kg-1 dry weight) and Cladocera taxa (0.3 particles per individual). Cladocera microplastic shapes were dominated by fibers with high densities of the transparent color scheme. Pearson correlation results indicated that sediment microplastic abundances were negatively correlated with chlorophyll-a concentration, temperature, and resistivity, whereas they were positively correlated with pH and salinity during the hot-wet season, with no variables significant in the cool-dry season. Cladocera microplastic abundances were positively correlated with conductivity and salinity during the cool-dry season, but no variables in the hot-wet season. These findings provide insights into the role of reservoirs as microplastic retention sites and the potential for uptake and transfer from lower trophic groups. These insights can be used to strengthen future monitoring and intervention strategies. Integr Environ Assess Manag 2024;20:2256-2270. © 2024 SETAC.

Sicklefin devilray and common remora prey jointly on baitfish

Devil rays are considered pelagic filter-feeders but direct observation of their foraging in the wild is very scarce and their feeding ecology is known essentially from indirect methods. On September 2018, a group of 16 sicklefin devil rays were observed preying on bait balls of longspine snipefish (Macroramphosus scolopax), together with their associated common remora (Remora remora), at Princess Alice seamount, Azores (mid-north Atlantic). Image analysis of these events and that of another devil ray feeding event on myctophids from the Pacific Ocean allowed the description of a new behavioural pattern (‘feeding pivot’). The significance of these behaviours is discussed in the broader context of mobulids’ feeding ecology, and a potential adaptive significance for the silver funnel surrounding the mouth of this species is proposed.

Evolutionary trends in large pelagic filter-feeders

ABSTRACT This paper attempts a synthesis of the evolution of large pelagic filter-feeding animals from the Cambrian to the present. Lineages known or suspected to have evolved large pelagic filter-feeding species are, in the order of their appearance, stem euarthropods, agnathan fishes, nautiloid cephalopods, placoderms, sharks, bony fishes, reptiles, ammonite cephalopods, and mammals. I discuss evolutionary trends which are apparent from the evolution of the large pelagic filter-feeding niche, which are 1. a size increase relative to their ancestral species, 2. the transition between taxonomic groups giving rise to pelagic filter-feeders, with vertebrates dominating the post-Cambrian, 3. the evolution of large pelagic filter-feeders from large carnivores in most, but not all cases, and 4. lengthy gaps in the record of pelagic filter-feeders around four of the big five mass extinctions.

Tube‐dwelling invertebrates: tiny ecosystem engineers have large effects in lake ecosystems

There is ample evidence that tube‐dwelling invertebrates such as chironomids significantly alter multiple important ecosystem functions, particularly in shallow lakes. Chironomids pump large water volumes, and associated suspended and dissolved substances, through the sediment and thereby compete with pelagic filter feeders for particulate organic matter. This can exert a high grazing pressure on phytoplankton, microorganisms, and perhaps small zooplankton and thus strengthen benthic‐pelagic coupling. Furthermore, intermittent pumping by tube‐dwelling invertebrates oxygenates sediments and creates a dynamic, three‐dimensional mosaic of redox conditions. This shapes microbial community composition and spatial distribution, and alters microbe‐mediated biogeochemical functions, which often depend on redox potential. As a result, extended hotspots of element cycling occur at the oxic‐anoxic interfaces, controlling the fate of organic matter and nutrients as well as fluxes of nutrients between sediments and water. Surprisingly, the mechanisms and magnitude of interactions mediated by these organisms are still poorly understood. To provide a synthesis of the importance of tube‐dwelling invertebrates, we review existing research and integrate previously disregarded functional traits into an ecosystem model. Based on existing research and our models, we conclude that tube‐dwelling invertebrates play a central role in controlling water column nutrient pools, and hence water quality and trophic state. Furthermore, these tiny ecosystem engineers can influence the thresholds that determine shifts between alternate clear and turbid states of shallow lakes. The large effects stand in contrast to the conventional limnological paradigm emphasizing predominantly pelagic food webs. Given the vast number of shallow lakes worldwide, benthic invertebrates are likely to be relevant drivers of biogeochemical processes at regional and global scales, thereby mediating feedback mechanisms linked to climate change.

Low cost sequencing of mitogenomes from museum samples using baits capture and Ion Torrent

The development of various target enrichment methods in combination with next generation sequencing techniques has greatly facilitated the use of partially degraded DNA samples in genetic studies. We employed the MYbaits target enrichment system in combination with Ion Torrent sequencing on a broad range of DNA quality, extracted from tissues obtained from both natural history archives and through various opportunistic sampling methods, to sequence the mitogenome of 11 mobulid rays and two closely related species. Mobulids are large, elusive pelagic filter feeders, for which conservation concerns have recently be raised in connection to their vulnerable life histories and increasing fishing pressure. We show that the MYbaits target enrichment method can be used to effectively sequence large parts of the mitogenome from heavily degraded DNA samples, and provide a time and cost effective alternative for genetic studies of rare and/or difficult to sample species.

A dated molecular phylogeny of manta and devil rays (Mobulidae) based on mitogenome and nuclear sequences

Manta and devil rays are an iconic group of globally distributed pelagic filter feeders, yet their evolutionary history remains enigmatic. We employed next generation sequencing of mitogenomes for nine of the 11 recognized species and two outgroups; as well as additional Sanger sequencing of two mitochondrial and two nuclear genes in an extended taxon sampling set. Analysis of the mitogenome coding regions in a Maximum Likelihood and Bayesian framework provided a well-resolved phylogeny. The deepest divergences distinguished three clades with high support, one containing Manta birostris, Manta alfredi, Mobula tarapacana, Mobula japanica and Mobula mobular; one containing Mobula kuhlii, Mobula eregoodootenkee and Mobula thurstoni; and one containing Mobula munkiana, Mobula hypostoma and Mobula rochebrunei. Mobula remains paraphyletic with the inclusion of Manta, a result that is in agreement with previous studies based on molecular and morphological data. A fossil-calibrated Bayesian random local clock analysis suggests that mobulids diverged from Rhinoptera around 30 Mya. Subsequent divergences are characterized by long internodes followed by short bursts of speciation extending from an initial episode of divergence in the Early and Middle Miocene (19–17 Mya) to a second episode during the Pliocene and Pleistocene (3.6 Mya – recent). Estimates of divergence dates overlap significantly with periods of global warming, during which upwelling intensity – and related high primary productivity in upwelling regions – decreased markedly. These periods are hypothesized to have led to fragmentation and isolation of feeding regions leading to possible regional extinctions, as well as the promotion of allopatric speciation. The closely shared evolutionary history of mobulids in combination with ongoing threats from fisheries and climate change effects on upwelling and food supply, reinforces the case for greater protection of this charismatic family of pelagic filter feeders.

Increasing Severity of Phytoplankton Nutrient Limitation Following Reductions in Point Source Inputs to the Tidal Freshwater Segment of the James River Estuary

We conducted monthly bioassay experiments to characterize light and nutrient use efficiency of phytoplankton communities from the chlorophyll-a maximum located in the tidal freshwater region of the James River Estuary. Bioassay results were interpreted in the context of seasonal and inter-annual variation in nutrient delivery and biomass yield using recent and long-term data. Bioassay experiments suggest that nutrient limitation of phytoplankton production has increased over the past 20 years coinciding with reductions in point source inputs and estuarine dissolved nutrient concentrations. Despite increasing nutrient stress, chlorophyll concentrations have not declined due to more efficient nutrient usage. Greater CHLa yield (per unit of N and P) may be due to feedback mechanisms by which the presence of toxin-producing cyanobacteria inhibits grazing by benthic and pelagic filter-feeders. Seasonal patterns in nutrient limitation indicate that phytoplankton in the James respond to variations in inflow concentrations of dissolved nutrients. This association gives rise to an atypical pattern whereby the severity of nutrient limitation diminishes with low discharge in late summer due to minimal dilution of local point sources inputs by riverine discharge. We suggest that this may be a common feature of estuaries located in proximity to urbanized areas.

Cladocerans respond to differences in trophic state in deeper nutrient poor lakes from Southern Norway

We investigated the role of trophic state in structuring the cladoceran assemblages in 35 relatively deep lakes of low nutrient levels in Southern Norway. The lakes cover gradients of altitude, latitude, longitude, area and total phosphorus concentration. The environmental control of the cladoceran assemblages was analyzed using canonical correspondence analysis. Total phosphorus was the most important variable in the minimal adequate model. Hence, the cladoceran assemblage changed with trophic state. Typical clear water species were displaced by indicators of eutrofication with increasing trophic levels. Littoral species constituted the majority of the species recorded. Littoral and pelagic species richness showed a unimodal relationship with trophic state. Along with the change in trophic state and shift in cladoceran assemblage, we observed an increase in the ratio of pelagic to littoral species as well as in the ratio of pelagic efficient bacterial feeders to total pelagic filter feeders. The study indicates that zooplankton could provide a valuable indicator of ecosystem’s structure and function in deeper nutrient poor lakes if included in water quality assessments according to the EU Water Framework Directive. Including sampling of the littoral zooplankton would improve diversity estimates and incorporate the response of the littoral zone to eutrophication.

Daphnia as a model organism in limnology and aquatic biology: introductory remarks

Cladocerans of the genus Daphnia are keystone pelagic filter feeders in many temperate ponds and lakes. They have also become popular model organisms in various biological disciplines, from aquatic ecology to biomedical sciences. The crucial features that make these organisms excellent experimental models are their cyclical parthenogenetic life cycle together with easy culturing and handling. Thanks to these characteristics, the number of publications dealing with Daphnia is rapidly growing. The special insert to the Journal of Limnology on Daphnia biology contains contributions that deal directly or indirectly with the reproduction and development of these water fleas, in relation to various ecological factors. These include predator-prey interactions and their impact on morphology, population dynamics, or senescence-related traits, growth of daphnids on a diet consisting of invasively spreading cyanobacteria, and also the impact of extreme floods on a Daphnia population (and particularly on its dormant ephippial egg bank) in a reservoir. Here, we discuss these presented works, and point out the potential lines of research that may improve the generalisation of their findings.

Filter feeding and plankton dynamics in a Danish fjord: a review of the importance of flow, mixing and density-driven circulation

Filter feeders are important components in coastal ecosystems where they remove suspended food particles from the water. A key to the understanding of spatial and temporal variations in pelagic biomass is knowledge of the circumstances under which filter feeding takes place. Frequently changing salinities caused by water exchange between the highly saline North Sea and the brackish Baltic create density-driven currents that are of great importance not only for the extent of grazing impact exerted by benthic filter-feeding macro-invertebrates (e.g. bivalves, ascidians and polychaetes), but also for the performance of pelagic filter feeders such as jellyfish and their zooplankton prey organisms. There is good evidence that the feeding demands and effectiveness of filter feeders explain variations in plankton biomass. In a recent project the hydrodynamic conditions in a Danish fjord (Kerteminde Fjord/Kertinge Nor) were brought into focus where it was found that the interaction between hydraulic processes and filter-feeding organisms (ascidians and jellyfish) could explain otherwise unaccountably large variations in the phytoplankton biomass. The interaction between hydrography and filter feeders is typically overlooked although of great importance for marine monitoring programmes using parameters such as phytoplankton biomass routinely in the assessment of environmental conditions.1998 Academic Press Limited

On detritus as a food source for pelagic filter-feeders

Data on the amount of organic detritus within the particle size fraction 1 to 150 μ are presented for the Western Kiel Bight. Grouped into a mixed surface layer and a stratified lower layer in accordance with the main hydrographic features of the Western Baltic Sea, the rounded-off values show a seasonal variation between 100 and 600 mg m-3 expressed as dry weight of organic matter. The overall average for both layers is about 200 mg m-3. Organic detritus thus comprises more than 40% of total organic matter in the above size class, which is the class most easily accessible to the relatively small filter-feeders in this area. Attempting to trace the origin of organic detritus, a positive correlation to phytoplankton standing stock was found in some cases, suggesting the predominance of autochthonous detritus. Proceeding from the assumption that pelagic filter-feeders select their food mainly by size and not by taste, it is concluded that organic detritus plays an important role as a supplementary food source, being ingested together with phytoplankton and small nonmotile heterotrophs. The nutritive value of detritus is increased by the adsorption of dissolved organic matter and above all through the subsequent colonization by bacteria, which utilize the dissolved substances. Detritus particles serving as a substratum for bacteria thus form a means whereby dissolved organic substances reenter the food chain. The ingestion of detritus by filter-feeders is, therefore, thought to be instrumental in increasing the effectivity of energy transfer from the primary to the secondary food-chain level.

Energy Flow in Euphausia pacifica

To understand relationships within food webs in the sea, with an eye to predicting and perhaps ultimately improving the efficiency of the production of commercially important species, we must understand the energetics of the lower elements of the food web. Energy flow more accurately represents the significance of a species in a community than either the numbers or the biomass of the species1. Euphausiids (class Crustacea) are pelagic filter-feeders of world-wide distribution which serve as forage for a wide variety of marine animals, including whales2 and salmon3. Euphausia pacifica Hansen, the principal species in the North Pacific, often represents the largest biomass of the macroplankton in the subarctic and transitional water masses4. The species is a vertical migrant, inhabiting depths of roughly 100–500 m during the day and ascending to surface waters at night4. It is exposed to water temperatures of about 5°–15° C off Oregon (depending upon season and depth of migration); 10° C is the approximate average5. Day length varies off Oregon from about 8 h in winter to 16 h in summer, so that the time spent in waters of different temperature varies seasonally6.