Gut Pigment Research Articles

Seasonal and developmental variation in feeding by the copepod Calanus sinicus in the Yellow Sea

We investigated feeding by Calanus sinicus in the Yellow Sea over four seasons in 2019–2022 using the gut pigment method. Studying the feeding of copepods is important for understanding processes within food webs, but little is known about the feeding ecology of C. sinicus, a major consumer of primary production in the Yellow Sea. The seasonal mean ingestion rate of C. sinicus was 16.6–42.1 for copepodite stage I (CI), 24.1–41.8 for CII, and 32.7–58.5 ng chl ind.−1 d−1 for CIII, with different seasonal fluctuations in each stage. The seasonal mean ingestion rate was 45.8–114.4 for CIV, 50.2–189.3 for CV, 96.9–438.9 for females, and 69.8–132.3 ng chl ind.−1 d−1 for males, with higher values in spring and lower values in summer. The combined grazing impacts of C. sinicus from the CI to adult stages were 1.66%, 1.43%, 2.04%, and 0.65% in spring, summer, autumn, and winter, respectively. The ingestion rate of later developmental stages from CIV to adults was positively related to chlorophyll-a concentration rather than water temperature or salinity, according to a redundancy analysis. These results suggest that C. sinicus population in the Yellow Sea actively feeds on phytoplankton in spring and that most of the grazing impact is attributed to females.

The Interplay of Mycosporine-like Amino Acids between Phytoplankton Groups and Northern Krill (Thysanoessa sp.) in a High-Latitude Fjord (Kongsfjorden, Svalbard).

We investigated pigment and mycosporine-like amino acid (MAA) concentrations of phytoplankton and Northern krill (Thysanoessa sp.) in sub-Arctic Kongsfjorden. Chlorophyll a (Chl-a) concentrations in the surface and middle-layer water were 0.44 μg L−1 (±0.17 μg L−1) and 0.63 μg L−1 (±0.25 μg L−1), respectively. Alloxanthin (Allo, a marker of cryptophytes) was observed at all stations, and its mean values for surface and middle-layer water were 0.09 μg L−1 (±0.05 μg L−1) and 0.05 (±0.02 μg L−1), respectively. The mean MAA-to-Chl-a ratios at the surface (3.31 ± 2.58 μg (μg Chl-a)−1) were significantly higher than those in the middle-layer water (0.88 ± 0.49 μg (μg Chl-a)−1), suggesting that these compounds play an important role in reducing UV photodamage. In gut pigment levels of Northern krill, the most abundant accessory pigment was Allo (2.79 ± 0.33 μg g−1 dry weight; d.w.), as was the accumulation of Chl-a (8.29 ± 1.13 μg g−1 d.w.). The average concentration of MAAs was 1.87 mg g−1 d.w. (±0.88 mg g−1 d.w.) in krill eyes, which was higher than that in all other body parts (0.99 ± 0.41 mg g−1 d.w.), except for the gut. Thysanoessa sp. was found to contain five identified MAAs (shinorine, palythine, porphyra-334, mycosporine-glycine, and M-332) in the krill eye, whereas shinorine and porphyra-334 were only observed in the krill body, not the eyes and gut. These findings suggest that Northern krill accumulate MAAs of various compositions through the diet (mainly cryptophytes) and translocate them among their body parts as an adaptation for photoprotection and physiological demands.

The effect of phytoplankton properties on the ingestion of marine snow by Calanus pacificus.

Marine snow, formed through the aggregation of phytoplankton and other organic matter, can be consumed by various types of zooplankton, affecting both planktonic trophic dynamics and the export of carbon to depth. This study focuses on how two factors—phytoplankton growth phase and species—affect copepod feeding on marine snow. To do this, we conducted a series of grazing experiments using gut pigment and stable isotope methods to quantify the ingestion of the copepod, Calanus pacificus, on both marine snow aggregates and individual phytoplankton. Results demonstrate that marine snow can represent a substantial food source for copepods, comparable to rates on individual phytoplankton. Moreover, we found that both the overall ingestion and the relative ingestion of aggregates vs. individual phytoplankton depended on phytoplankton growth phase for experiments conducted with the diatom Thalassiosira weissflogii. Although copepods consumed aggregates composed of Skeletonema marinoi at similar rates as those composed of T. weissflogii, no effect of growth phase was observed for S. marinoi. These findings suggest that marine snow can be an important source of nutrition for copepods, but that its role in planktonic food webs may differ depending on the phytoplankton community composition and the stage of phytoplankton blooms.

Diel Feeding Rhythm and Grazing Selectivity of Small-Sized Copepods in a Subtropical Embayment, the Northern South China Sea

Small marine copepods are key components of the pelagic food webs in Chinese coastal waters, but very few studies have addressed their trophodynamics, with even fewer studies addressing their diel feeding rhythms. In this study, the diel feeding rhythm and grazing selectivity of the copepod assemblage in Daya Bay during September 30 to October 2, 2014, were studied based on gut pigment analysis. Small copepods (body length < 1.5 mm) including Paracalanus parvus, Temora turbinata, Acrocalanus gibber, Temora stylifera, Euterpe acutifrons, and Acrocalanus gracilis, accounted for 73.9–100% of the total copepod abundance. The copepod assemblage generally exhibited a diurnal feeding pattern, characterized by a higher gut pigment content and ingestion rate during the daytime, consistent with variation in the ambient Chl α concentration. Fifty-five percent of the phytoplankton standing stock per day was consumed by the copepod assemblage, wherein diatoms, prymnesiophytes, and cyanobacteria were the main prey items with average contributions of 19.4–32.9% to the gut pigment contents. The copepod assemblage showed a strong feeding preference for prymnesiophytes, a weak feeding preference for diatoms, and avoidance of cyanobacteria. These results suggest a strong top-down control on phytoplankton community, especially on small groups from small copepods in the Daya Bay ecosystem.

Implications of Pyrosoma atlanticum range expansion on phytoplankton standing stocks in the Northern California Current

Coinciding with the marine heat wave in 2014 and a strong El Niño in 2016, blooms of the tropical-temperate pelagic colonial tunicate, Pyrosoma atlanticum, expanded into the Northern California Current (NCC). Given the high densities of P. atlanticum colonies observed in the NCC, and their potential for high grazing rates, we hypothesized that the species could have a substantial negative effect on the phytoplankton standing stock in the Northeastern Pacific Ocean. In the late winter, spring and early autumn of 2018, we measured abundances and length frequencies of P. atlanticum colonies off the coast of Oregon and estimated their spring grazing impact on the local phytoplankton standing stock. Abundances of P. atlanticum peaked in late winter (0.7 colonies m−3), dropped off in spring (0.42 colonies m−3), and declined to near-absent in early autumn (0.07 colonies m−3). We observed a doubling in the median size of P. atlanticum colonies from late winter to spring, followed by a decline in size in early autumn. With their high individual colony gut pigment contents and bloom densities, the overall spring grazing impact of P. atlanticum was substantial, reaching a maximum of 22% of the available phytoplankton standing stock.

Data on distribution, demographic structure and grazing of the dominant mesozooplankton species in the Yenisei estuary and adjacent shelf in early summer.

The data article refers to the paper “Distribution and grazing of the dominant mesozooplankton species in the Yenisei estuary and adjacent shelf in early summer (July 2016)” (Drits et al., 2020). The data were collected along quasi-longitudinal transect “Yenisei estuary – Kara Sea shelf” on 24–28 July 2016. Here we present data on the spatial and vertical distribution, demographic structure and gut pigment content of the dominant zooplankton species as well as the grazing impact on autotrophic phytoplankton in the three distinguished zones: freshwater zone, frontal zone of the Yenisei plume and marine shelf zone. The related article (Drits et al., 2020) considers the structure and functioning of zooplankton community in relation to environmental characteristics such as temperature, salinity, phytoplankton abundance, timing of ice retreat. Information presented in this article can be used by marine biologists for studies of structure and functioning of estuarine pelagic communities, ecology of zooplankton in the Siberian seas. Besides the data could provide a baseline for the assessment of the ecological role played by climate change events (e.g., increased precipitation, permafrost thawing, elevated river discharge) on the Arctic ecosystems.

Mesozooplankton connect the microbial food web to higher trophic levels and vertical export in the New Zealand Subtropical Convergence Zone

The Subtropical Convergence Zone (SCZ) in the Chatham Rise region east of New Zealand supports productive fisheries and benthic ecosystems and is an important CO2 sink. The SCZ trophic system is underpinned by a microbially-dominated food web, requiring an efficient link between pico-sized producers and larger consumers to support the necessary trophic transfers. However, the role of mesozooplankton (>200 μm body size) as intermediaries in this trophic transfer is not well understood. This study investigated the trophic role of mesozooplankton in subantarctic (SA) and subtropical (ST) waters of the SCZ, south and north of the Chatham Rise, in summer 2000. Mean summer biomasses of mesozooplankton were low in SA and ST waters (181 and 137 mg dry weight m−2, respectively) relative to other seasons. Mesozooplankton biomass was dominated by copepod nauplii, copepodites and small adults (Oithona, Calocalanus, Clausocalanus) and pre-adult euphausiids, while pelagic tunicates (salps and pyrosomes) were rare. Copepod gut pigment contents showed high weight-specific phytoplankton grazing, and feeding incubations showed rapid consumption of ciliates by all sizes of copepods, indicating omnivory as an important trophic mode. Irrespective, consumption by mesozooplankton had only minor impacts on water column phytoplankton and microzooplankton biomass, and production, and nutrient regeneration. Linear Inverse Ecosystem Models (LIEMs) were used to investigate the overall role of mesozooplankton in carbon (C) cycling among autotrophs, heterotrophs, and export fluxes, based on measured plankton rates and biomasses from summer 2000 in SA and ST waters. LIEMs indicated a dominant role for protistan zooplankton (ciliates and heterotrophic nanoflagellates) in consumption of primary biomass and production (71–97%) and a strong protistan – mesozooplankton trophic link. The summer mesozooplankton were shown to be important in transferring energy from the microbially-dominated food web to sinking fluxes and to higher trophic levels (~12 mg C m−2 d−1 to each), the latter equivalent to ~0.42 of mesozooplankton C consumed by higher trophic levels annually in the Chatham Rise SCZ.

Sex-specific grazing dynamics of the recently described copepod, Lovenula raynerae, in an ephemeral pond in the Eastern Cape province of South Africa

This study investigated the temporal changes in the sex specific ingestion rates of the recently described calanoid copepod, Lovenula raynerae, which numerically and by biomass dominates the plankton community in ephemeral ponds in the Eastern Cape province of South Africa. Ingestion rates of the copepod were investigated on two occasions, one week after emergence and two weeks thereafter, employing the gut fluorescent technique. Results of the study indicate the absence of any diel patterns in feeding for both sexes on both sampling occasions (p > 0.05 in both cases). Moreover, there was no significant differences in gut pigment contents between adult male and females during either of the surveys (p > 0.05). Daily rations of the adult copepods during the two studies were equivalent to <2% (range 0.8 to 1.8%) body carbon per day suggesting that they are consuming alternative carbon sources to meet their daily carbon requirements. The main findings of this study suggest that L. raynerae can be considered as a generalist omnivore.

Grazing Impact of the Copepod Calanus sinicus on Phytoplankton in the Northern East China Sea in Late Spring

We investigated the feeding habits of Calanus sinicus during its four developmental stages as copepodite 4 (CIV), copepodite 5 (CV), adult males and females in early June 2015 at 12 sampling stations along the southern coast of Korea to the northern East China Sea, to better understand the role of C. sinicus in controlling phytoplankton stocks. Ingestion rate, daily ration as body carbon, population ingestion rate, and grazing impact were estimated using the gut pigment method. The mean biomass of CVs was the greatest (13.5 mg C m–3) and that of adult males was the lowest (0.7 mg C m–3). The ingestion rate per C. sinicus individual tended to increase with developmental stage, with the highest rate in adult females (519 ng chl ind–1 d–1) and the lowest rate in CIVs (305 ng chl ind–1 d–1). A significant correlation was found between ingestion rate and temperature, but not salinity or chlorophyll-a concentration. The daily ration of C. sinicus as body carbon significantly decreased with increased body weight, with the highest value found in CIVs (66.4%) and the lowest value in adult males (30%). Despite the high ingestion rate of the adults, the mean grazing impact of C. sinicus on phytoplankton biomass, in terms of chlorophyll-a concentration, was the highest in CVs (2.6%), followed by CIVs and adult females, and was the lowest in adult males (0.1%). The higher grazing impact of copepodites than adults underscores the importance of evaluating copepodite stages in the feeding studies of marine food webs.

Food availability on the shore: Linking epilithic and planktonic microalgae to the food ingested by two intertidal gastropods

Research on the interaction of primary producers and consumers is crucial for understanding trophic transfer in intertidal food webs. This study explores the association between epilithic and planktonic microalgae, and gut contents of two targeted intertidal gastropods, the periwinkle Echinolittorina radiata (splash zone) and the limpet Cellana toreuma (mid-intertidal zone). With the application of gut fluorescence technique and metabarcoding, this study investigates the quantity and composition of two different sources of microalgae (epilithic and planktonic) and the food ingested by the gastropods. The results suggest the following findings: 1) The planktonic microalgae have higher compositional similarity to the gut contents of grazing gastropods. 2) Increased gut pigment content in C. toreuma is observed with increasing abundance of epilithic and planktonic microalgae. However, there was no such pattern observed for E. radiata. This difference could be attributed to potentially divergent foraging behaviours of the two species that inhabit different shore heights.

Diel changes of food sources and their contributions to nutrition of Orientomysis mitsukurii in a sandy shore environment

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 26:229-244 (2017) - DOI: https://doi.org/10.3354/ab00690 Diel changes of food sources and their contributions to nutrition of Orientomysis mitsukurii in a sandy shore environment Kazutaka Takahashi1,*, Akira Kuwata2, Takeo Suzuki3, Tatsuki Toda3, Keiichiro Ide2 1Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan 2Tohoku National Fisheries Research Institute, 3-27-5 Shinhama-cho, Shiogama, 985-0001, Japan 3Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan *Corresponding author: akazutak@mail.ecc.u-tokyo.ac.jp ABSTRACT: Diel changes in feeding habits and the relative contributions of daytime and nighttime diets to the nutrition of the mysid Orientomysis mitsukurii in a sandy shore environment were determined by field sampling and additional laboratory experiments. O. mitsukurii was distributed just above the bottom during the daytime but a subpopulation swam up into the water column at night. Nighttime swimming activity was prevalent in small individuals but progressively decreased at larger body sizes, while the gut pigment contents of all mysid size classes consistently increased at night. Stomach content analysis revealed that O. mitsukurii individuals of all size groups ingested sedimented particulate organic matter (POM) containing large quantities of clay minerals during the daytime, whereas they mainly foraged on planktonic diatoms in the water column at night. Estimated in situ algal ingestion rates at night accounted for approximately 80-95% of the daily carbon assimilation. O. mitsukurii also exhibited high efficiency in grazing on planktonic diatoms in laboratory experiments. Conversely, daytime sedimented POM carbon accounted for only a minor proportion (5-20%) of the daily carbon assimilation. The utilisation patterns of the different food sources were confirmed by carbon and nitrogen stable isotopic signatures in the benthic community. Our results suggest that efficient utilisation of primary producers, such as planktonic diatoms, by O. mitsukurii is beneficial for maintaining the species’ high abundance from an ecological transfer efficiency perspective, and that sedimented POM is an alternative food source for securing the basic energy required for their survival, particularly when phytoplankton availability is low. KEY WORDS: Mysidae · Omnivore · Nighttime feeding · Vertical migration · Sandy shore environment · Detritus · Diatoms Full text in pdf format PreviousCite this article as: Takahashi K, Kuwata A, Suzuki T, Toda T, Ide K (2017) Diel changes of food sources and their contributions to nutrition of Orientomysis mitsukurii in a sandy shore environment. Aquat Biol 26:229-244. https://doi.org/10.3354/ab00690 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 26. Online publication date: December 04, 2017 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2017 Inter-Research.

Feeding, egg production, and respiration rate of pteropods Limacina in Arctic seas

The feeding, egg production, and respiration rate of the dominant pteropod Limacina helicina have been studied in Russia’s Arctic seas. The sinking rates of fecal pellets and dead individuals have been measured to estimate their role in vertical carbon flux. As has been shown, the rate of ecophysiological processes taking place in the pteropods is higher than that of copepods, the main consumers of phytoplankton. The gut pigment content in Limacina (3084 ng ind–1 as a maximum) was two orders of magnitude higher than in copepods. The egg production rate in Limacina even without feeding reached 4000 eggs ind–1 versus 350–450 egg ind–1 typical of the dominant copepods even with excess food. A close correlation between the pteropod feeding rate and individual body weight was observed for Limacina rather than a correlation with food concentration. The experimentally estimated sinking rate of Limacina fecal pellets was 270 m day–1, higher than for most copepods. The sinking rate of dead pteropods reaches 2000 m day–1. According to the literature, discarded mucous feeding nets sink at a rate of 80 to 1080 m day–1. Evidently, pteropods play a significant role in biogeochemical cycles by accelerating sedimentation. High rates of all studied processes suggest that Limacina are an important component of plankton communities and play the most important role in trophodynamics at sites of their accumulation.

Temporal variability in copepod gut pigments over the central western continental shelf of India

The Indian Western continental shelf (IWCS) is amongst the most productive regions of the world, being noteworthy for upwelling (south-west monsoon) and downwelling (north-east monsoon) that tunes the water biogeochemistry. The present study provides baseline information on temporal variation of in situ copepod gut pigments from IWCS. The copepods were collected between November 2011 and October 2013 and gut pigment contents and composition were estimated using the gut fluorescence method. Results revealed that copepods procured high gut pigment content in monsoon that coincided with ambient water pigment credited to discrete upwelling. Fluorometric analyses of copepod orders revealed presence of gut chlorophyll a (Chl a) throughout the study with highest gut Chl a (0.31 ± 0.25 ng copepod−1; N = 21) and total gut pigments (2.01 ± 2.15 ng copepod−1; N = 21) recorded in Calanoida. Consecutively, Calanoida and Poecilostomatoida chiefly consumed autotrophic biomass that was evident from presence of canthaxanthin and astaxanthin as dominant gut pigments. Interestingly, the marker pigment of Cryptophyceae was present only in Calanoida during monsoon and post-monsoon. Collectively these results conclude that copepods predominantly showed omnivory with discrete temporal variability by grazing upon autotrophic biomass that in turn probably supports the fishery.

Copepod summer grazing and fecal pellet production along the Western Antarctic Peninsula

Copepods are important grazers on phytoplankton and contributors to carbon export, but their role is poorly understood in the Western Antarctic Peninsula (WAP), a region of high productivity and rapid climate warming. We conducted grazing and egestion experiments with large, dominant copepods each January from 2012 to 2014. We found higher gut evacuation rates (k), initial gut pigment and ingestion rates (I) for Calanus propinquus and Rhincalanus gigas compared with Calanoides acutus. Since k and I linearly increased with chlorophyll a for most species, ingestion rates were 4–70 times greater in more productive coastal regions than offshore, slope waters. Copepods have a low grazing impact on phytoplankton biomass (<1%) and productivity (1%, up to 11%) compared with the dominant WAP macro- and microzooplankton. Egestion rates were high (0.8–37.3 µgC ind.−1 day−1); however, ∼58% of fecal pellets are retained in the upper water column. Daily carbon rations of ∼1% indicated feeding on other carbon sources (protozoans and metazoans) to meet metabolic demands. However, during a coastal phytoplankton bloom, daily C rations increased to up to 13%, indicating increased reliance on phytoplankton. Future changes in the WAP plankton community may affect food web carbon flow and export.

Feeding dynamics of the fiddler crab (Uca annulipes) in a non-tidal mangrove forest

To investigate the lack of tidal influence on the feeding dynamics of fiddler crabs, we used an in situ gut fluorescence technique to measure gut pigment content of Uca annulipes in the non-tidal mangrove habitat of the St Lucia Estuary. Measurements were taken over a 24-h cycle and in the two extreme seasons, austral summer and winter, to examine any diel and seasonal shifts in feeding. Three hour gut evacuation experiments were conducted to determine the gut evacuation rate and potential sexual differences in feeding. It was found that under lack of tidal fluctuations, U. annulipes feeding is influenced by diel rhythms. In summer, males displayed a bimodal pattern of feeding, becoming more active in the morning and late afternoon with a gut evacuation rate of 0.795h–1, whereas females remained generally inactive and displayed short bouts of feeding during the day with a gut evacuation rate of 0.322h–1. The summer grazing impact of U. annulipes on microphytobenthos was higher compared with winter. In winter both sexes were fairly inactive, but displayed a greater consumption efficiency (65% compared with 45% in summer). U. annulipes feeding dynamics in a non-tidal habitat are shown to vary seasonally, daily and among sexes.

Short-term changes in the mesozooplankton community and copepod gut pigment in the Chukchi Sea in autumn: reflections of a strong wind event

Abstract. To evaluate the effect of atmospheric turbulence on a marine ecosystem, high-frequency samplings (two to four times per day) of a mesozooplankton community and the gut pigment of dominant copepods were performed at a fixed station in the Chukchi Sea from 10 to 25 September 2013. During the study period, a strong wind event (SWE) was observed on 18 September. After the SWE, the biomass of chlorophyll a (Chl a) increased, especially for micro-size (&gt; 10 μm) fractions. The zooplankton abundance ranged from 23 610 to 56 809 ind. m−2 and exhibited no clear changes as a result of the SWE. In terms of abundance, calanoid copepods constituted the dominant taxa (mean: 57 %), followed by barnacle larvae (31 %). Within the calanoid copepods, small-sized Pseudocalanus spp. (65 %) and large-sized C. glacialis (30 %) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with the SWE. The dominance of accumulated lipids in C5 and C6 females with immature gonads indicated that they were preparing for seasonal diapause. The gut pigment of C. glacialis C5 was higher at night and was correlated with ambient Chl a (Chl a, and a significant increase was observed after the SWE (2.6 vs. 4.5 ng pigment ind.−1). The grazing impact by C. glacialis C5 was estimated to be 4.14 mg C m−2 day−1, which corresponded to 0.5−4.6 % of the biomass of the micro-size phytoplankton. Compared with the metabolic food requirement, C. glacialis feeding on phytoplankton accounted for 12.6 % of their total food requirement. These facts suggest that C. glacialis could not maintain their population by feeding solely on phytoplankton and that other food sources (i.e., microzooplankton) must be important in autumn. As observed by the increase in gut pigment, the temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition.

Diel distribution and feeding habits of Neomysis mirabilis under seasonal sea ice in a subarctic lagoon of northern Japan

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 23:183-190 (2015) - DOI: https://doi.org/10.3354/ab00620 Diel distribution and feeding habits of Neomysis mirabilis under seasonal sea ice in a subarctic lagoon of northern Japan Kazutaka Takahashi1,*, Norio Nagao2, Satoru Taguchi3 1Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan 2Institute of Bioscience, Universiti Putra Malaysia, 43400 Serdang, Selangor Darul Ehsan, Malaysia 3Faculty of Engineering, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577, Japan *Corresponding author: akazutak@mail.ecc.u-tokyo.ac.jp ABSTRACT: We investigated the diel distribution and feeding habits of the mysid Neomysis mirabilis under seasonal sea ice in a subarctic lagoon of northern Japan. Although large individuals (>11 mm total length) were present in the eelgrass beds regardless of the time of day, smaller individuals only migrated to the eelgrass beds at night, possibly from shallower waters. Investigation of their stomach contents revealed that N. mirabilis is primarily dependent on eelgrass epiphytes as a food source, in addition to small crustaceans. Calculations based on gut pigment analysis indicated that epiphytes were sufficient for large mysids to fulfill their metabolic requirements, whereas small mysids needed to ingest additional food items, such as small crustaceans, possibly because they were less able to graze the highly adhesive prostrate epiphytes. This study suggests that grazing on epiphytes could be a third option in the feeding habits of mysids (in addition to suspension-feeding and predation), and is beneficial in maintaining their high biomass, even during the winter. KEY WORDS: Crustaceans · Mysidacea · Overwintering · Distribution · Sea ice · Eelgrass · Epiphytes Full text in pdf format PreviousCite this article as: Takahashi K, Nagao N, Taguchi S (2015) Diel distribution and feeding habits of Neomysis mirabilis under seasonal sea ice in a subarctic lagoon of northern Japan. Aquat Biol 23:183-190. https://doi.org/10.3354/ab00620 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 23, No. 2. Online publication date: February 10, 2015 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2015 Inter-Research.

Early reproduction by Calanus glacialis in the Northern Bering Sea: the role of ice algae as revealed by molecular analysis

Calanus glacialis initiated feeding and reproduction under extensive sea ice in the northern Bering Sea during late winter despite very low mean water column chlorophyll a concentrations. A peptide nucleic acid (PNA)-PCR and clone library analysis of prey 18S rDNA in the guts of C. glacialis, together with the quantification of the more abundant prey species with quantitative PCR (qPCR), demonstrated feeding on sea ice algae. The ice algal diatoms, Fragilariopsis cylindrus, Fragilaria sp. and Pseudonitzschia sp. were the dominant prey species while the most abundant species in the water column, Thalassiosira antarctica, was not important. The total of these speciesspecific ingestion rates was strongly correlated (r 1⁄4 0.93) with, and similar to, those estimated from gut pigments. The increase in feeding and reproduction during the study was significantly related to air temperature lagged by 2 or 3 days. We suggest that warmer temperatures led to a release of ice algae into the water column stimulating feeding and reproduction. The availability of ice algae over an extended period during colder winters when sea ice cover is more extensive and lasts longer will lead to larger population sizes of C. glacialis compared with warmer years with less extensive ice cover.

Feeding capabilities and limitations in the nauplii of two pelagic estuarine copepods, Pseudodiaptomus marinus and Oithona davisae

In most aquatic ecosystems, copepod nauplii outnumber all other mesozooplankton. Although thousands of studies have examined feeding by later life history stages, the feeding habits of nauplii are poorly known. We offered conspecific adult and naupliar stages of the current‐feeding calanoid copepod Pseudodiaptomus marinus and the ambush‐feeding cyclopoid copepod Oithona davisae 14 species of phytoplankton from various functional and taxonomic groups that spanned a wide size range. Using a novel epifluorescence microscopy method, we calculated an index of gut pigment for copepods fed each phytoplankton species. We also measured adult and naupliar feeding rates on three species of phytoplankton: the cryptomonad Rhodomonas salina, the prasinophyte Tetraselmis suecica, and the diatom Thalassiosira pseudonana, by an improved gut fluorescence method using a microplate reader. Despite their smaller size, weaker swimming and sensory capabilities, and rudimentary feeding apparatus, nauplii fed on a large range of cell sizes and were capable of consuming many of the same phytoplankton as adults.

Mummichog Fundulus heteroclitus responses to long-term, whole-ecosystem nutrient enrichment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 492:211-222 (2013) - DOI: https://doi.org/10.3354/meps10495 Mummichog Fundulus heteroclitus responses to long-term, whole-ecosystem nutrient enrichment Konner C. Lockfield1, John W. Fleeger1,*, Linda A. Deegan2 1Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA 2The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA *Corresponding author. Email: zoflee@lsu.edu ABSTRACT: The effects of eutrophication on coastal plants and sessile animals are becoming well known, but responses of mobile species are less well studied. Here, we link variation in abundance, biomass, body size, growth rate, and resource utilization in mummichogs Fundulus heteroclitus >40 mm in length to experimental nutrient enrichment in Plum Island Sound, Massachusetts, USA. To mimic cultural eutrophication, dissolved fertilizer was released into replicate saltmarsh creeks on each rising tide throughout entire growing seasons. In the summer of the sixth year of enrichment, we released coded-wire tagged mummichogs into nutrient-enriched (n = 3733 fish) and reference (n = 3894 fish) creeks and recaptured them over the next 2 mo. We found increased abundance (by 37%), biomass (58%), body size (8%), and herbivory (115%, measured as photosynthetic gut pigment content) in nutrient-enriched creeks, although body condition was unaffected. However, individual growth rates were 43% lower in nutrient-enriched creeks. Nutrient enrichment stimulated primary production, causing a bottom-up enrichment of the food web which fostered increased biomass and body size. However, the reduction in growth rate indicates an adverse consequence of long-term nutrient enrichment. This negative effect occurred in the absence of increased hypoxia in these highly tidally (4 m amplitude) flushed study creeks. The mummichog is an important predator/grazer in salt marshes, and nutrient-induced alterations in biomass or resource utilization will directly or indirectly affect lower trophic levels, including benthic algae, thereby impacting the ecosystem-wide response to eutrophication. KEY WORDS: Fundulus heteroclitus · Mark and recapture · Eutrophication · Decimal coded-wire tags · Growth rate · Salt marsh Full text in pdf format PreviousNextCite this article as: Lockfield KC, Fleeger JW, Deegan LA (2013) Mummichog Fundulus heteroclitus responses to long-term, whole-ecosystem nutrient enrichment. Mar Ecol Prog Ser 492:211-222. https://doi.org/10.3354/meps10495 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 492. Online publication date: October 31, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.