Benthic food web structure in the southeastern Chukchi Sea: an assessment using ��13C and ��15N analyses

The benthos of the southeastern Chukchi Sea shelf is typified by high faunal abundance and biomass resulting from settlement of a large proportion of seasonal phytoplankton under highly nutritious offshore Bering Shelf Anadyr Water (BSAW). In contrast, inshore Alaska Coastal Water (ACW) is much less productive. Yet the Chukchi Bight and Kotzebue Sound, located under ACW in the southeastern Chukchi Sea, contain a substantial faunal abundance and biomass of invertebrates, fishes and marine mammals. We examined food web structure to gain an understanding of how a relatively rich benthic fauna with a high biomass can be supported under ACW with a supposedly low flux of carbon to the benthos. We measured stable isotope (δ¹³C and δ¹⁵N) values of selected organisms (from zooplankton to fishes) as markers of food sources and trophic position to compare fauna on the shelf under BSAW with that in the Chukchi Bight and Kotzebue Sound under ACW. Relative isotope position of organisms in all three regions was similar, even though some pelagic species within the Sound were depleted in δ¹³C compared to the other regions. We attribute the depletion to the influence of terrestrially derived carbon. We suggest that the hydrodynamics along an oceanic front between the Chukchi Shelf and the Chukchi Bight support the advection of nutrient-rich POC into the Bight and Sound as additional food sources to local production. We conclude that local conditions and multiple POC sources in the Bight and Sound support the substantial population of benthic invertebrates and the fishes, seabirds, and marine mammals that feed on them.     

Southeastern Chukchi Sea (Alaska) epibenthos

Epibenthos of the southeastern Chukchi Sea, inclusive of Kotzebue Sound, was sampled in 1976. Crustaceans dominated abundance while echinoderms, mainly sea stars, dominated biomass. Spatial distribution of fauna was determined by cluster analysis. Scavenger-predators were dominant trophic groups, although suspension feeders dominated some regions. Unexpected high abundance and biomass under Alaska Coastal Water and factors related to presence and distribution of fauna are discussed. Dissimilarities between the benthic systems of the southeastern and northeastern Chukchi Seas are attributed to more complex water mass and flow patterns in the southern system. Entrained particulate organic carbon disperses through the area to support an abundant and apparently highly productive benthic fauna, which sustains resident and transient populations of demersal fishes and marine mammals. Epibenthos was sampled again in 1998 and, although little change was apparent in community composition, many taxa had higher abundance and biomass than 22 years earlier, a trend similar to findings observed in the northeastern Bering Sea.Electronic Supplementary Material Supplementary material is available for this article at     

Macro- and megabenthic communities in the high Arctic Canada Basin: initial findings

We investigated the macro- and megabenthos of the Canada Basin, one of the biologically least known areas of the Arctic deep sea. Macro-infauna was collected with 11 box cores at six stations ranging from 640 to 3,250 m water depth. Total abundance ranged from 3 to 265 individuals 0.04 m^–2 (75–6,625 individuals m^–2) and decreased with increasing depth. Biomass ranged from 0.04 to 228 mg wet weight 0.04 m^–2 (1–5,700 mg wet weight m^–2) and followed the same trend. Polychaetes, crustaceans and bivalves dominated the faunal densities, biomass and species numbers. At Northwind Ridge (800 and 1,800 m), apparently historic (~5,000 years BP) fish otolith deposits were abundant. The invertebrate epi-megafauna was qualitatively analyzed from 9.2 h of video and 853 still images collected at four remotely operated vehicle stations. The epifauna was dominated by polychaetes, crustaceans, echinoderms, cnidarians and fish, with most suspension-feeders occurring in the Northwind Ridge area. A total of 90 benthic invertebrate species/taxa from four biogeographic affinities were identified, including at least three new species of Isopoda. The evident low abundances and biomass are in agreement with findings from the Eurasian Arctic deep sea.     

Some results on quantitative investigations of macrozoobenthos in the Scotia Arct (Antarctica)

Summary Abundance and biomass of macrozoobenthos off South Orkney Islands, Elephant Island and the Antarctic Peninuula were studied by grab sampling in November/December 1984 and February to April 1985. Polychaetes, molluscs and crustaceans dominate in abundance, echinoderms and polychaetes in biomass. Differences in abundance and biomass were observed between the northern and south-western shelf areas of the Peninsula. Mean invidivual weight (B/N) is rather high. Biomass and B/N are not depth dependent within the range 60 to 850m. The importance of the infauna is stressed.     

Unusual abundance of macrobenthos and biological invasions in the Chukchi Sea

The data from the expedition of the program RUSALCA conducted in 2004 showed unexpectedly high quantitative indices of macrobenthos in the southeastern Chukchi Sea. Extensive areas of the bottom northwest of the Bering Strait were dominated by the bivalve Macoma calcarea. The greatest biomass of benthos in Macoma-dominated areas was 4232 g/m² with an average of 1382 g/m² for the investigated region. Such a high biomass of soft-bottom communities, which is extremely uncommon even in the temperature regions of the oceans, is reported for the Arctic for the first time. The long-term existence (more than 70 years) of highly productive benthic communities dominated by Macoma calcarea in one and the same area of the Chukchi Sea can most likely be attributed to gyres, which constantly arise in the region northwest of the Bering Strait. These cyclonic gyres carry nutrient-rich bottom water to the surface and hinder larval transport away from mother populations. They also keep and concentrate major food sources of benthos (live and dead phyto-and zooplankton and fecal pellets) over the benthic community locations. Most likely, a significant proportion of the primary production in the southeastern Chukchi Sea is used by benthos within the investigated Macoma community. Findings of three relatively large warm-water Pacific species near Point Hope in the Chukchi Sea are probably indicative of the progressive climate warming during the last century.     

Mesozooplankton beneath the summer sea ice in McMurdo Sound,Antarctica: abundance,species composition,and DMSP content

The summer Phaeocystis antarctica bloom increases under-ice phytoplankton biomass in McMurdo Sound, Antarctica. The magnitude of mesozooplankton grazing on this bloom is unknown, and determines whether this production is available to the pelagic food web. We measured mesozooplankton abundance and body content of dimethylsulfoniopropionate (DMSP) during the McMurdo Sound austral summer (2006 and 2006–2007). Abundance varied from 20 to 4,500 ind. m⁻³ (biomass 0.02–274.0 mg C m⁻³), with peaks in mid-December and late-January/February. Abundance was higher but total zooplankton biomass lower in our study compared to previous reports. Copepods and the pteropod Limacina helicina dominated the zooplankton in both abundance and biomass. DMSP was detected in all zooplankton groups, with highest concentrations in copepod nauplii and L. helicina (95 and 54 nmol mg⁻¹ body C, respectively). Experiments suggested that L. helicina obtains DMSP by directly grazing on P. antarctica, which often accumulates to high biomass under the summer sea ice in McMurdo Sound.     

The current state and long-term changes of zoobenthos in the Novosibirsk reservoir

The composition, structure, and spatial distribution of zoobenthos in the Novosibirsk reservoir have been analyzed. A decrease in species richness an increase in invertebrates abundance from upper to low sites of the reservoir, caused by changes in bottom sediment types, have been observed. A comparative analysis of the benthos community structure for a 50-year period (1959–2008) clearly demonstrates that, with an increase in the biomass of invasive species in the reservoir, the biomass of large bivalve mollusks decreases.     

Distribution,abundance and ecology of the meiofauna in a tropical estuary along the west coast of India

The distribution and abundance of subtidal meiofauna in Mandovi estuary of Goa were studied from June 1983 to June 1984. Monthly faunal abundance ranged from 491 to 2791/10 cm² and dry weight biomass from 0.16 to 2.80 mg 10 cm². Free living nematodes were the dominant group contributing over 75% of the total density and 30 to 42% of the total biomass. Among nematodes the deposit feeders were more abundant in fine muddy substratum while epigrowth feeders dominated in sandy substratum.Harpacticoids were next, comprising 6.9 to 8.7% of the total meiofauna number, followed by turbellaria (3.8–4.5%), polychaeta (2.8–3.2%) and ostracods (1.6–4.5%) The contribution of other groups to faunal density was 4.5–6.2%. In the biomass the ostracods contributed most (29.8–54.7%), followed by nematodes (23.8–34.6%). Over 60% of the fauna occurred in the top 2 cm of the sediment and the faunal density reduced significantly with increasing depth in the sediment. The vertical distribution of meiofauna was positively correlated to the vertical distribution of Eh, chlorophyll a and interstitial water. Seasonality was greatly influenced by the south-west monsoon and the fauna quickly repopulated after the monsoon. Salinity, temperature and food influenced the faunal abundance.     

Die Biomasse mariner Makrobenthos-Gesellschaften im Einflußbereich der Klärschlammverklappung vor der Elbemündung

The macrofauna of a dumping area in the eastern part of the German Bight (North Sea) was investigated in July, August and November, 1978 at five stations situated on a transect including central and peripheral areas of the dumping region. Abundance and biomass (ash free dry weight) of the macrofauna and its variation from July to November were analysed as well as the biomass of different taxa. Molluscs dominated over polychaetes, crustaceans and echinoderms. A positive correlation seemed to exist between mud content and biomass at the peripherally situated stations. In the central sewage sludge area, however, the biomass values were reduced. In late autumn the biomass decreased in the entire area due to the death ofDiastylis rathkei, Abra alba andPectinaria koreni. These species were replaced by the molluscNucula turgida and polychaeteNephtys hombergii. In autumn the biomass values also showed a distinct minimum at the central stations.     

Use of the photo method in the study of the composition and abundance of soft-bottom macrobenthos

The composition and abundance of the macrobenthic fauna associated with soft-bottom beds of the large bivalve mollusks Crenomytilus grayanus and Modiolus modiolus were studied in the inner part of Vostok Bay (Sea of Japan) in spring 2010. More than 30 taxa of animals were found in the mussel beds. Comparison of the data obtained with three different methods of studying muddy-bottom mussel communities showed that 80% of their biomass and only up to 25% of the species composition and 19% of the abundance can be estimated by the photo method. Photo surveys disregard small and/or juvenile animals, as well as infaunal organisms, and thus do not give a complete picture of the species, size, and age composition and abundance of biota.     

Pelagic fish and zooplankton species assemblages in relation to water mass characteristics in the northern Bering and southeast Chukchi seas

This research explores the distributions and community composition of pelagic species in the sub-Arctic and Arctic waters of the northern Bering and central and southern Chukchi seas during September 2007 by linking pelagic zooplankton and fish assemblages to water masses. Juvenile saffron cod (Eleginus gracilis), polar cod (Boreogadus saida), and shorthorn sculpin (Myoxocephalus scorpius) were most abundant in warm, low salinity Alaska Coastal Water (ACW) of the central Chukchi Sea, characterized by low chlorophyll, low nutrients, and small zooplankton taxa. Adult Pacific herring (Clupea pallasii) were more abundant in the less stratified Bering Strait waters and in the colder, saltier Bering Shelf Water of the northern Bering and southern Chukchi seas, characterized by high chlorophyll, high nutrients, and larger zooplankton taxa. Juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon were most abundant in the less stratified ACW in the central Chukchi Sea and Bering Strait. Abundances of large zooplankton were dominated by copepods (Eucalanus bungii, Calanus glacialis/marshallae, Metridia pacifica) followed by euphausiids (juvenile Thysanoessa raschii and unidentified taxa), whereas small zooplankton were dominated by bivalve larvae and copepods (Centropages abdominalis, Oithona similis, Pseudocalanus sp.). Pelagic community composition was related to environmental factors, with highest correlations between bottom salinity and large zooplankton taxa, and latitude and fish species. These data were collected in a year with strong northward retreat of summer sea ice and therefore provide a baseline for assessing the effects of future climate warming on pelagic ecosystems in sub-Arctic and Arctic regions.     

The faunal structure of a mid-Cretaceous rudist reef core

The macrofaunal distribution of the mid-Cretaceous El Abra Limestone reef core is quantified from two measured sections in Taninul Quarry, San Luis Potosi, central Mexico. The faunal structure is transitional between typical Lower Cretaceous reefs dominated by corals with low-density rudist bivalve packing; and densely-packed, rudist-dominated Upper Cretaceous reefs. The macrofauna is predominantly associations of unconnected individuals of caprinid rudists, with a low diversity of other shelly mollusks and corals. An examination of the alternation of paleocommunities defined by the dominant caprinid taxa reveals no pattern of biotic succession within the reef core. Large-scale sedimentologic features of mud and debris content, coupled with rudist growth type, suggest that paleocommunities may have been physically controlled.     

Spatial variation of intertidal macroinvertebrates and environmental variables in Robbins Passage wetlands,NW Tasmania

Macroinvertebrate composition, abundance and biomass were investigated at four intertidal sites throughout the Robbins Passage wetlands, Tasmania, over a 12-month period, in order to identify differences among and within sites, and to determine whether environmental variables could explain these differences. As this region is the most important shorebird area in Tasmania, we wanted to quantify the potential food source for shorebirds within the wetlands. Thirty-five taxa from 28,928 individuals were identified, with a mean abundance of 6026.6 ind m⁻² and biomass of 27.1 gDW m⁻². Bivalves and gastropods dominated the assemblage in terms of abundance and biomass (79% and 60%, respectively). There was a significant interaction among tidal level, site and season for invertebrate abundance and diversity, while biomass differed significantly among sites. In general, the mid-intertidal stratum had the greatest invertebrate density and diversity, while the low intertidal stratum had the greatest biomass. Community composition varied among the four sites, with the bivalve Paphies elongata dominating at two of the sites, while gastropods and polychaetes were more abundant at the other sites. Differences in invertebrate composition and abundance could partly be explained by seagrass biomass, i.e., dry mass of seagrass leaves and roots. Areas with seagrass had increased invertebrate abundance and diversity, but mean sediment particle size, % organic carbon and % seagrass cover had no significant effect. These results will assist in the investigation of habitat use by shorebirds and the identification of important shorebird feeding areas within the wetlands. Handling editor: P. Viaroli     

Zooplankton composition and distribution off the coast of Galicia, Spain

During June and September 1984, zooplankton samples were collectedwith other hydrographic and biological data along the Galiciancoast (NW of Spain). In June copepods contributed {small tilde}60%to the total zooplankton community, with larvaceans, siphonophoresand cladocerans also abundant. In September >90% of the zooplanktonsampled were copepods. The dominant species of copepods in bothJune and September were Acartia clausi, Paracalanus parvus andTemora longicornis. The meroplankton was dominated by echinoderms,bryozoans, barnacle larvae and bivalve larvae. In June the averagezooplankton biomass was 31.08 mg C m^–3; the Septemberaverage was 41.69 mg C m^–3. The relationship between theslopes of the regression equations (biomass versus abundance)suggests that the zooplankton assemblage in June was composedby larger animals than in September. The major concentrationof zooplankton was between 0 and 50 m, with both June and Septemberdaytime surface samples having 6–7 times the amount oforganisms than the lower water column (50–100 m). Therewere no distinct differences in total zooplankton abundancesat the inshore and offshore stations; however, the inshore stationsoften had a higher percentage of meroplankton than the offshorestations. In June zooplankton abundance at the northern transectsand the western transects was similar. In September there weregreater concentrations of zooplankton in the western Galicianshelf as compared with the northern shelf. These differencesin the horizontal distribution of the zooplankton were relatedto upwelling events.     

Structure of macrozoobenthos in the Gorky Reservoir at the beginning of XXI century

The taxonomic, trophic, and quantitative structures of the macrozoobenthos in the deepwater part of the Gorky Reservoir were studied in autumn 2005. A total of 51 species of bottom macroinvertebrates were revealed, most of which were represented by chironomids, oligochaetes, and mollusks. The detriti-vores—swallowers dominated in number; phytodetritivores—filtrators + gatherers dominated in biomass. An analysis of the long-term dynamics of the macrozoob enthos structure in the Gorky Reservoir revealed that the average abundance and biomass decreased at the beginning of the XXI century.     

Food of the platypus (Ornithorhynchus anatinus) with notes on the food of brown trout (Salmo trutta) in the Shoalhaven River,N.S.W.

Feeding in the platypus (Ornithorhynchus anatinus) was investigated by identifying material found in the cheek pouches of animals trapped in nets in a study area on the upper Shoalhaven River, N.S.W. Benthic samples were taken in the rapids and pools of the river and the relative abundance of food items available was related to the food found in the platypus cheek pouches. The main food organisms found were insect larvae, notably Trichoptera, Diptera, Coleoptera, Ephemeroptera and Odonata. Subsidiary food items found included freshwater shrimp (Paratya australiensis), bivalve mollusks (Sphaerium sp.) and one anuran. The main food items were generally taken in direct proportion to their numerical abundance in the river. Comparisons are made with the food selected by the brown trout (Salmotrutta) from the area. Estimates are made of the weights of invertebrate food necessary to maintain a platypus in various seasonal conditions.     

Horizontal distribution of microprotist community structure in the western Arctic Ocean during late summer and early fall of 2010

The western Arctic Ocean is composed of two regions: the southern shelf and the northern basin, whereas the marine ecosystem structure is expected to vary between the regions, little information is available, particularly for the planktonic protist community. In this study, we surveyed the horizontal distribution of microprotists (diatoms, dinoflagellates and ciliates) at 59 stations in the western Arctic Ocean during September and October of 2010. The abundances of diatoms, dinoflagellates and ciliates were 0–138,640, 0–16,460 and 0–10,933 cells L^?1, respectively, and all of the abundances were higher on the Chukchi Sea shelf. Cluster analysis based on abundance separated the microprotist community into five groups, which contain 25, 22, 6, 4 and 2 stations. The largest group was observed on the Chukchi Sea shelf, showing a high abundance predominated by diatoms (78 % of total abundance). The second group was observed from the East Siberian Sea to the Canada Basin, characterised by low abundance and ciliate dominance (36 % of total abundance). Because of the high abundance and predominance of diatoms, the former group is characterised by eutrophic waters, which are enhanced by the continuous inflow of the nutrient-rich Pacific Water through the Bering Strait. Due to the low abundance and the dominance of ciliates, the latter group is dominated by organisms of the microbial food web. The remaining three groups were smaller and located between the two large groups. The distribution of these three groups may be based on complex physical structures, such as the anticyclonic eddy near the shelf break.     

A quantitative scuba-diving survey of the sublittoral macrobenthos at subantarctic Marion Island

Summary A SCUBA-diving survey of the macrobenthos of hard substrata in the sublittoral zone at subantarctic Marion Island was conducted during March and April 1988. Dense beds (12 kg m^–2) of the kelp Macrocystis laevis occur in depths > 5 m. Durvillaea antarctica is found along the infralittoral fringe and Desmarestia rossi and Durvillaea sp. occur in a narrow zone from 3 m–6 m. Under-storey algae (chiefly rhodophytes) tend to decrease in biomass with depth, with mean values of 1.57 kg m^–2 at 5m, 0.75 kg m^–2 at 10m and 0.49 kg m^–2 at 15 m. Encrusting coralline algae are particularly abundant in shallow areas (¯x = 0.92 kg m^–2) but are insignificant in deeper areas. Total biomass of macrozoobenthos increased with depth with mean values of 0.12 kg m^–2 at 5 m, 0.34 kg m^–2 at 10 m and 0.46 kg m^–2 at 15 m. Polychaetes, crustaceans, echinoderms, molluscs, sponges and bryozoans dominated the macrozoobenthos in terms of biomass. Approximately 200 species of macrobenthic animals were recorded and numerically, polychaetes, crustaceans, molluscs, nematodes and echinoderms dominated. The sublittoral benthos at Marion Island is compared with that occurring at other subantarctic and Antarctic islands, in particular, the Kerguelen Island group. Zoogeographic trends and the possible effects of nutrient input from seabird guano are briefly discussed.     

Relicts of the Tethyan fauna in the Recent oceans

In tropical, two subtropical, low boreal, and notal zones of the Recent oceans, the distribution of benthic relict animal taxa is clarified for brachiopods, mollusks, echinoderms, and some other taxonomic groups. The richest places for relict taxa are situated at the depths of the bathyal zone (intermediate zone between shallow water and the abyss). Preservation of relicts is a result of oceanic asymmetry and the disposition of faunal centers in the western parts of the oceans. This asymmetry in hydrological and biological structure of the oceans depends on the global peculiarities of the Earth. The Atlantic and Indian ocean centers show faunal exchanges and their origin from West Tethyan ancestors.     

Fauna and Predator-Prey Relationships of Ettling,an Actinopterygian Fish-Dominated Konservat-Lagerst?tte from the Late Jurassic of Southern Germany

The newly recognized Konservat-Lagerstätte of Ettling (Bavaria), field site of the Jura-Museum Eichstätt (JME), is unique among Late Jurassic plattenkalk basins (Solnhofen region) in its abundant, extremely well preserved fossil vertebrates, almost exclusively fishes. We report actinopterygians (ginglymodins, pycnodontiforms, halecomorphs, aspidorynchiforms, “pholidophoriforms,” teleosts); turtles; and non-vertebrates (echinoderms, arthropods, brachiopods, mollusks, jellyfish, sponges, biomats, plants) in a current faunal list. Ettling has yielded several new fish species (Bavarichthys incognitus; Orthogonikleithrus hoelli; Aspidorhynchus sanzenbacheri; Macrosemimimus fegerti). Upper and lower Ettling strata differ in faunal content, with the lower dominated by the small teleost Orthogonikleithrus hoelli (absent from the upper layers, where other prey fishes, Leptolepides sp. and Tharsis sp., occur instead). Pharyngeal and stomach contents of Ettling fishes provide direct evidence that Orthogonikleithrus hoelli was a primary food source during early Ettling times. Scarcity of ammonites and absence of vampyromorph coleoids at Ettling differ markedly from the situation at other nearby localities in the region (e.g., Eichstätt, Painten, Schamhaupten, the Mörnsheim beds), where they are more common. Although the exact biochronological age of Ettling remains uncertain (lack of suitable index fossils), many Ettling fishes occur in other plattenkalk basins of Germany (e.g., Kelheim) and France (Cerin) dated as Late Kimmeridgian to Early Tithonian (eigeltingense horizon), suggesting a comparable geologic age. The Ettling deposits represent an independent basin within the larger Upper Jurassic “Solnhofen Archipelago”, a shallow subtropical sea containing scattered islands, sponge-microbial and coral reefs, sandbars, and deeper basins on a vast carbonate platform along the northern margin of the Tethys Ocean.