Epibenthic Organisms Research Articles

Toxicokinetics and bioaccumulation of polycyclic aromatic compounds in wood frog tadpoles (Lithobates sylvaticus) exposed to Athabasca oil sands sediment

We performed accumulation-elimination experiments of polycyclic aromatic compounds (PACs) in wood frog tadpoles (Lithobates sylvaticus) using river sediment from Canada’s Athabasca oil sands region. The PACs in wood frog tadpoles were ∼2x higher on average when the animals were in direct contact with PAC-contaminated sediment than when they were separated from the sediment with a screen and exposed only to aqueous PACs. These results suggest that sediment exposure/ingestion contributes as much to PAC accumulation in tadpoles as exposure via aqueous pathways. Alkyl-substituted PAC concentrations in exposed tadpoles exceeded those of the unsubstituted (parent) PACs by about 10 × . Bioaccumulation factors ranged between 0.01 and 4.93, with parent PACs having higher bioaccumulation factors than alkylated PACs. Wood frog tadpoles efficiently eliminated and metabolized most parent and alkyl-substituted PACs, though some compounds (e.g., C4-naphthalenes) had higher bioaccumulation potential and may serve as effective markers of exposure. Here we present a comprehensive analysis of the toxicokinetics and bioaccumulation of PACs (52 analytes) in amphibian larvae, and highlight the importance of sediment exposure when considering the bioaccumulation and potential biological impact of PACs in benthic and epibenthic organisms.

LARGE-SCALE EXPANSION OF HYPOXIA AT MARINE BENTHAL ZONE IN GEOMORPHOLOGICALLY COMPARABLE BAYS-FJORDS OF CRIMEA PENINSULA UNDER DIFFERENT TECHNOGENIC LOADS

Aim. Comparative analysis of the aeration features of the bottom waters during the different seasons of the year between the Sevastopol and Donuzlav Bays as geomorphological similar in configuration semi-closed sea reservoirs of the Black Sea under different anthropogenic loads. Material and methods. Sevastopol and Donuzlav Bays, located in the Western part of the Crimean Peninsula, were studied. The concentration and total consumption of dissolved oxygen in the water column and the bottom layer were determined in situ using a digital LDO analyzer. The redox potential in bottom sediments was measured using a platinum electrode. Results. Aeration of the water column in the Sevastopol seaside is suitable for normal life of pelagic and epibenthic organisms. At the same time, in the Sevastopol and Donuzlav Bays the large-scale anoxia in the surface layer of bottom sediments was found. Also, the muddy sediments of the Sevastopol Bay’ bed can be an oxygen-deficient extreme biotope for most of the year, the minimum concentration of O2 in the bottom water is not higher than 0.11-0.36 mg/l. The benthal zone here was well aerated only at the end of November. Conclusion. The general patterns of benthic hypoxia were identified for such coast objects as Sevastopol and the Donuzlav Bays, which are similar by their contours and recent seabed structures. Benthal zones of both investigated bays-fjords can be attributed to hypoxic high-gradient habitats, that have a whole generality with oxygen-deficient marine waters habitats – estuarine zones, areas of gas seeps, etc. Strong oxygen deficiency, toxic H2S contamination coupled with organic enrichment a typically benthic environment for such biotopes.

Transcriptome analysis of the midgut gland of the brown shrimp Crangon crangon indicates high polymorphism in digestive enzymes

Tolerance of organisms towards heterogeneous and variable environments is highly related to physiological flexibility. An effective strategy to enhance physiological flexibility is the expression of polymorphic enzymes. This seems to be the case in the brown shrimp Crangon crangon. It shows high reproduction rates, feeds opportunistically on endo- and epibenthic organisms, and is apparently well adapted to variable environmental conditions. Previous electrophoretic studies revealed a high level of polymorphism and no consistent phenotype of digestive enzymes between individuals. In order to understand the underlying biochemical processes, we carried out a transcriptome-based study of digestive enzymes of C. crangon. Detailed sequence analyses of triacylglycerol lipase, phospholipase A2, alpha amylase, chitinase, trypsin and cathepsin L were performed to identify putative isoforms. The number of isoforms, and thus the degree of polymorphism varied among enzymes: lipases and carbohydrases showed higher numbers of isoforms in enzymes that besides their extracellular function also have diverse intracellular functions. Furthermore, cysteine proteinases showed a lower polymorphism than serine proteinases. We suggest that the expression of enzyme isoforms improves the efficiency of C. crangon in gaining energy from different food sources.

Presence of microplastics in benthic and epibenthic organisms: Influence of habitat, feeding mode and trophic level

The exponential production and use of plastics has generated increasing environmental release over the past decades, and microplastics (MPs) have been reported across all the oceans. Field studies have documented the occurrence of MPs in several species, but important knowledge gaps still remain. In the present study, we characterized the distribution of MPs in ten sediment-dwelling and epibenthic species representative of different habitat, feeding modes and trophic levels within the inner Oslofjord (Oslo, Norway), an area subjected to moderate anthropogenic pressures. Analysed species included fish, bivalves, echinoderms, crustaceans and polychaetes. MPs were present in all the species with a frequency up to 65% of positive individuals for some species. In most cases, 1 or 2 MPs were found per individual, but some organisms contained up to 7 particles. A total of 8 polymer typologies were identified, with PE and PP being the most common according to our extraction protocol. MP sizes ranged from 41 μm to lines as long as 9 mm. Our results indicate that occurrence of MPs in analysed biota is not influenced by organism habitat or trophic level, while characteristics and typology of polymers might be significantly affected by feeding mode of organisms.

Seasonal diversity and composition of epibenthic organisms on a North Carolina, USA continental shelf hard bottom

Subtidal marine hard bottoms are valuable habitats that support diverse epibenthic and fish communities. The degree to which hard bottom community structure varies spatially and temporally is not fully understood. Identifications of macroalgae and sessile invertebrates in scraped quadrats were done at three separate times (May, July, and September 2016) at three sites along the 5-mile ledge hard bottom in Onslow Bay, North Carolina. Spatial and temporal epibenthic community diversity and composition were measured. Diversity did not vary over time (p=0.065) or between sampling sites (p=0.130). There was, however, a change in community composition over time (p <0.003) and between two of the studied sites (p=0.012). Bottom water temperature might partially explain the observed temporal variation in composition, and site wide patchiness might explain the spatial variation in composition. These findings indicate that seasonal sampling of multiple sites is required to establish community baselines for these valuable habitats.

A critical analysis of diet in seventeen deep sea fishes along the South-eastern Arabian Sea

Diet analysis of 1190 fishes belonging to 17 species of deep sea fishes were conducted. The samples were collected from the South-eastern Arabian Sea in bottom trawl by the research vessel FORV Sagar Sampada (cruise no. 322 and 345) during January 2014 and October 2015, between lat. 7- 150N and long. 78 - 720E in the depth range 200 - 1000 m. Diet composition, feeding strength, size range, depth range, distribution and index of preponderance were ascertained for all the species. It was observed that the deep sea fishes mainly feed on benthic and epibenthic organisms such as fishes, shrimps, crabs and squids, revealing their carnivorous nature. Deep sea shrimps are one of the major diet components of these fishes, which is an indication of the availability of good quantity of deep sea shrimps, along the South-eastern Arabian Sea and this abundant population can be commercially utilised in order to lessen the pressure of overexploitation being experienced in case of coastal shrimps.

A geochemical study of the Ediacaran discoidal fossil Aspidella preserved in limestones: Implications for its taphonomy and paleoecology.

The Ediacara biota features the rise of macroscopic complex life immediately before the Cambrian explosion. One of the most abundant and widely distributed elements of the Ediacara biota is the discoidal fossil Aspidella, which is interpreted as a subsurface holdfast possibly anchoring a frondose epibenthic organism. It is a morphologically simple fossil preserved mainly in siliciclastic rocks, which are unsuitable for comprehensive stable isotope geochemical analyses to decipher its taphonomy and paleoecology. In this regard, three-dimensionally preserved Aspidella fossils from upper Ediacaran limestones of the Khatyspyt Formation in the Olenek Uplift of northern Siberia offer a rare opportunity to leverage geochemistry for insights into their taphonomy and paleoecology. To take advantage of this opportunity, we analyzed δ13 Ccarb , δ18 Ocarb , δ13 Corg , δ34 Spyr , and iron speciation of the Khatyspyt Aspidella fossils and surrounding sediment matrix in order to investigate whether they hosted microbial symbionts, how they were fossilized, and the redox conditions of their ecological environments. Aspidella holdfasts and surrounding sediment matrix show indistinguishable δ13 Corg values, suggesting they did not host and derive significant amount of nutrients from microbial symbionts such as methanogens, methylotrophs, or sulfide-oxidizing bacteria. δ13 Ccarb , δ18 Ocarb , and δ34 Spyr data, along with petrographic observations, suggest that microbial sulfate reduction facilitated the preservation of Aspidella by promoting early authigenic calcite cementation in the holdfasts before matrix cementation and sediment compaction. Iron speciation data are equivocal, largely because of the low total iron concentrations. However, consideration of published sulfur isotope and biomarker data suggests that Aspidella likely lived in non-euxinic waters. It is possible that Aspidella was an opportunistic organism, colonizing the seafloor in large numbers when paleoenvironments were favorable. This study demonstrates that geochemical data of Ediacaran fossils preserved in limestones can offer important insights into the taphonomy and paleoecology of these enigmatic organisms living on the eve of the Cambrian explosion.

Rheotaxis in the Ediacaran epibenthic organism Parvancorina from South Australia

Diverse interpretations of Ediacaran organisms arise not only from their enigmatic body plans, but also from confusion surrounding the sedimentary environments they inhabited and the processes responsible for their preservation. Excavation of Ediacaran bedding surfaces of the Rawnsley Quartzite in South Australia has provided the opportunity to study the community structure of the Ediacara biota, as well as the autecology of individual organisms. Analysis of two bedding surfaces preserving large numbers of Parvancorina illustrates that individuals display a preferred, unidirectional orientation aligned with current, as indicated by the identified current proxies: tool marks, overfolded edges of Dickinsonia, felled fronds and drag structures generated by uprooted frond holdfasts. Taphonomic and morphological evidence suggests that the preferred orientations of Parvancorina individuals are not the result of passive current alignment, but represent a rheotactic response at some stage during their life cycle. These results illustrate a previously unrecognized life mode for an Ediacaran organism and arguably the oldest known example of rheotaxis in the fossil record. The morphology and previously suggested phylogenetic affinities of Parvancorina are also re-evaluated. Apart from possessing a bilaterally symmetrical body, there are no unequivocal morphological characters to support placement of Parvancorina within the Euarthropoda or even the Bilateria.

Trophic ecology of Atlantic seabob shrimp Xiphopenaeus kroyeri: Intertidal benthic microalgae support the subtidal food web off Suriname

A combination of stomach content analyses and dual stable isotope analyses was used to reveal the trophic ecology of Atlantic seabob shrimp Xiphopenaeus kroyeri off the coast of Suriname. This coastal penaeid shrimp species has a rather omnivorous diet, feeding opportunistically on both animal prey and primary food sources. The species is a predator of hyperbenthic crustaceans, including copepods, amphipods and the luciferid shrimp Lucifer faxoni, which are mainly preyed upon during daytime, when these prey typically reside near the seabed. Benthic microalgae (BM) from intertidal mudflats and offshore sedimentary organic matter (SOM) were important primary food sources. Due to their depleted 13C values, coastal sedimentary and suspended organic matter, and carbon from riverine and mangrove-derived detritus were not incorporated by X. kroyeri. An ontogenetic diet shift was observed from postlavae to juveniles and adults. Adult X. kroyeri were located higher in the food chain, mainly preying on larger benthic organisms. Intertidal BM were an important food source for all life stages of X. kroyeri, contributing up to 64% to the overall diet based on a Bayesian mixing model. Because X. kroyeri is the main epibenthic organism found at high densities in nearshore waters up to 30 m depth, the species plays a crucial role in transferring energy from low trophic level prey and primary food sources up to higher levels in the food chain. Our results indicate that primary production on intertidal mudflats, through BM, forms an important energy source for the subtidal turbid-water food web in muddy tropical coasts. Conservation of intertidal areas and their associated mangrove systems will therefore likely benefit coastal shrimp production and fisheries in tropical ecosystems.

Deeply hidden inside introduced biogenic structures – Pacific oyster reefs reduce detrimental barnacle overgrowth on native blue mussels

In sedimentary coastal ecosystems shells of epibenthic organisms such as blue mussels (Mytilus edulis) provide the only major attachment surface for barnacle epibionts, which may cause detrimental effects on their mussel basibionts by e.g. reducing growth rate. In the European Wadden Sea, beds of native blue mussels have been invaded by Pacific oysters Crassostrea gigas, which transformed these beds into mixed reefs of oysters with mussels. In this study, we determined the spatial distribution of M. edulis and their barnacle epibionts (Semibalanus balanoides) within the reef matrix. Mean mussel density near the bottom was about twice as high compared to the mussel density near the top of an oyster reef, whereas barnacles on mussels showed a reversed pattern. Barnacle dry weight per mussel was on average 14 times higher near the top than at the bottom. This pattern was confirmed by experimentally placing clean M. edulis at the top and on the bottom of oyster reefs at two sites in the Wadden Sea (island of Texel, The Netherlands; island of Sylt, Germany). After an experimental period of five weeks (April and May 2015, the main settlement period of S. balanoides), the number of barnacles per mussel was at both sites significantly higher on mussels near the top compared to near the bottom. We conclude that the oyster reef matrix offers a refuge for M. edulis: inside reefs they are not only better protected against predators but also against detrimental barnacle overgrowth. This study shows that alien species can cause beneficial effects for native organisms and should not be generally considered as a risk for the recipient marine ecosystems.

THE POTENTIAL OF ARTIFICIAL LIVE ROCK AS SUBTRATE FOR CORAL SPAT AND EPIBENTHIC ORGANISMS

Over-exploitation on natural live rock promotes the degradation of ocean ecosystem. This concern has been raised since harvesting may reduce the density of marine ornamentals and degrade marine habitat quality. This study aims to develop artificial live rocks (ALR) that potentially to be used as one of the alternatives to reduce the overharvesting activity toward natural live rocks. The study was conducted at Bidong Island, Terengganu started from April to October 2014. There were 2 types of ALR used in this study; rough and smooth surfaces. A total of 64 pieces of ALR were deployed in April 2014 and retrieved in June, August and October 2014 respectively. Identification in terms of coral spat species and macrobenthic organisms was done after the each retrieval. Coral spat was identified based on the morphology of their columella, septa and corallite wall by using Dinolight Digital Camera. Four species of coral juveniles (Pocillopora damicornis, Stylophora pistillata, Seriatopora hystrix and Acropora millepora) were found attached on ALR surfaces. Whereby, there were 11 phyla of epibenthic organisms were found to attach on ALR which dominated by turf algae and red algae. Percentage coverage of epibenthic calculated using Coral Point Count with Excel extension (CPCe) shown ALR was dominated by turf algae after 2 months (69%) and 4 months (20%) of deployment respectively. Afterward, Red algae (31%) dominated after 6 months of deployment. There was significant difference between coral species and the surfaces (p&lt;0.05). However, no significant difference between types of surfaces with sessile macrobenthic organisms (p&gt;0.05). This finding showed that ALR has a potential to be upgraded as artificial reef towards marine habitat restoration.

Community composition of epibenthic megafauna on the West Greenland Shelf

Epibenthic organisms are a critical component of the marine environment, functioning as ecosystem engineers, habitat and food for other organisms. Our knowledge of the diversity, complexity and sensitivities of these habitats is limited, particularly at higher latitudes and greater depths. The West Coast of Greenland is the site of a commercially important shrimp trawl fishery, but there are few published records describing the benthic community structure of the region. Here we report results from benthic camera surveys conducted at 119 sites, over 3 years, spanning 1400 km of the West Greenland continental shelf (61–725 m depth). A total of 29 classes of epibenthic taxa were identified from the images. There are significant differences of composition and diversity in sites with hard and soft substrate. Hard-substrate communities are relatively diverse with higher abundances and are characterised by sessile, attached groups such as Hydrozoa, Anthozoa, Bryozoa and Porifera. Soft-sediment sites are less diverse and dominated by Polychaeta and have specialist Malacostraca such as the commercially exploited shrimp, Pandalus borealis. Distribution patterns and variation in epibenthic megafauna are related to substrate and the environmental parameters depth, temperature and current speed. This study represents the first quantitative characterisation of epibenthic megafaunal assemblages on the West Greenland continental shelf. These data constitute an important baseline, albeit in a region heavily impacted by trawl fisheries, and demonstrate the utility of benthic photography for examining and monitoring seabed diversity and change.

Variación espacial y temporal de los organismos de un intermareal rocoso: Bahía Panamá, Pacífico Norte, Costa Rica

&lt;p&gt;The intertidal rocky shore of Bahía Panama, within Bahía Culebra in the North Pacific coast of Costa Rica, was sampled to study the biodiversity and the spatial patterns (three sites with differences in wave exposure, and five strata, from low to high tide levels) and temporal variation (a single date in 2007 and 2013) in different microhabitats (over and under rock surface, and crevices). The epibenthic organisms were sampled with quadrats of 25 x 25 cm in each stratum, and cryptic fauna was accounted by both visual census and manual collecting. The general pattern of vertical zonation of organisms at each site showed an increase in variety toward the infralittoral level, as well as in the composition of assemblages or partially in identity of taxa in each stratum. The sheltered section of the rocky coast, with shallow sand bottom (&amp;lt; 1 m), low wave action and greater sedimentation rate, had lower diversity, cover and abundance that increased towards the wave-exposed section, with more abrupt slope in the edge of rocky platform, lower turbidity, and deeper sand bottom (2-3 m). The horizontal change was more evident in epibenthic organisms, followed by the under rock surface inhabitants and finally in crevices. For the epibenthic organisms, a temporal change in assemblages (cover and abundance) was found between the 2007 and 2013, at each site and level (possibly by seasonal upwelling influence), but the spatial structure (vertical and horizontal) of the rocky shore seems the main cause of change in the composition of species. The spatial pattern of change in the biota (sheltered to exposed gradient) could be expected in similar shores of the Central American Pacific. Finally, the 157 species found (16 autotrophic taxa, 22 fishes, and 119 invertebrates) indicate the high biodiversity of this habitat in the tropics, and the importance of their conservation. Rev. Biol. Trop. 62 (Suppl. 4): 85-97. Epub 2014 Diciembre 01.&lt;/p&gt;

Morphological and genetic analysis of the Coolia monotis species complex with the introduction of two new species, Coolia santacroce sp. nov. and Coolia palmyrensis sp. nov. (Dinophyceae)

The dinoflagellate genus Coolia Meunier is an important epi-benthic organism that is commonly found in association with other dinoflagellates known to cause ciguatera. Two closely related taxa, Coolia monotis and Coolia malayensis, make up the C. monotis species complex. In this study we introduce two new toxic species that should be included in that complex, Coolia palmyrensis Karafas, Tomas, York sp. nov. and Coolia santacroce Karafas, Tomas, York sp. nov., collected from the Palmyra Atoll in the Pacific Ocean and Saint Croix, US Virgin Islands, respectively. These two species can be distinguished morphologically by size, pore shape, pore density, and the relative size of the apical pore complex. The ITS1/5.8S/ITS2 and the D1/D2 regions of the LSU rDNA were used to provide molecular support of morphological observations using maximum likelihood and Bayesian analyses. Furthermore, C. palmyrensis and C. santacroce both showed cytotoxic effects on human derived cells in vitro.

Distribution and composition of the epibenthic megafauna north of Svalbard (Arctic)

Benthic communities north of Svalbard are less investigated than in other Arctic shelf regions, as this area was covered by sea-ice during most of the year. Improving our knowledge on this region is timely, however, since climate change is strongly evident there, particularly with regard to the extent of sea-ice decline and its huge ecological impact on all marine biota, including the benthos. Moreover, longer ice-free periods will certainly lead to an increase in human activity levels in the area, including bottom trawling. In two adjacent shelf and slope regions off northern Svalbard, we studied the composition of epibenthic megafauna and seafloor habitat structures by analyzing seabed images taken with both still and video cameras. In addition, we also used an Agassiz trawl to catch epibenthic organisms for ground-truthing seabed-image information. A wide variety of mostly sessile organisms 141 epibenthic taxa were identified in the images. The brittle star Ophiura sarsii and the soft coral Gersemia rubiformis were the most common species. At all stations >300 m in depth, evidence of trawling activities was detected at the seabed. The distribution of the benthic fauna in the study area exhibited a clear depth zonation, mainly reflecting depth-related differences in seabed composition. We conclude that natural factors determining the composition of the seafloor mostly affect the distribution and composition of epibenthic assemblages. Anthropogenic impact indicated by the trawl scours found is likely also important at smaller spatial scales.

Identifying sea scallops from benthic camera images

The article presents an algorithmic framework for the automated analysis of benthic imagery data. The data are collected by an autonomous underwater vehicle for the purpose of population assessment of epibenthic organisms, such as scallops. The architecture consists of three layers of processing: visual attention, graph‐cut segmentation methods, and template matching. The visual attention layer filters the imagery input, focusing subsequent processing only on regions in the images that are likely to contain target objects. The segmentation layer prepares for subsequent template matching. Finally, template matching classifies filtered objects into targets and distractors. The significance of the proposed approach is in its modular nature and its ability to process imagery datasets of low resolution, brightness, and contrast.

Benthic Habitats Around Iceland Investigated During the IceAGE Expeditions

Abstract During the IceAGE (Icelandic marine Animals – Genetics and Ecology) expeditions in waters around Iceland and the Faroe Islands in 2011 and 2013, visual assessments of habitats and the study of surface sediment characteristics were undertaken in 119–2750 m water depth. Visual inspection was realized by means of an epibenthic sled equipped with a digital underwater video camcorder and a still camera. For determination of surface sediment characteristics a subsample of sediment from box corer samples or different grabs was collected and analyzed in the lab. Muddy bottoms predominated in the deep basins (Iceland Basin, Irminger Basin, deep Norwegian and Iceland Seas), while sand and gravel dominated on the shelves and the ridges, and in areas with high currents. Organic contents were highest in the deep Norwegian and Iceland Seas and in the Iceland Basin, and at these sites dense aggregations of mobile epibenthic organisms were observed. Large dropstones were abundant in the Iceland Sea near the shelf and in the Denmark Strait. The dropstones carried diverse, sessile epibenthic fauna, which may be underestimated using traditional sampling gear. The paper supplies new background information for studies based on IceAGE material, especially studies related to ecology and taxonomy.

Ecological shifts in Mediterranean coralligenous assemblages related to gorgonian forest loss.

Mediterranean gorgonian forests are threatened by several human activities and are affected by climatic anomalies that have led to mass mortality events in recent decades. The ecological role of these habitats and the possible consequence of their loss are poorly understood. Effects of gorgonians on the recruitment of epibenthic organisms were investigated by manipulating presence of gorgonians on experimental panels at 24 m depth, for Eunicella cavolinii, and at 40 m depth, for Paramuricea clavata, at two sites: Tavolara Island (Tyrrhenian Sea) and Portofino Promontory (Ligurian Sea). After 4 months, the most abundant taxa on the panels were encrusting green algae, erect red algae and crustose coralline algae at 24 m depth and encrusting brown algae and erect red algae at 40 m depth. Assemblages on the panels were significantly affected by the presence of the gorgonians, although effects varied across sites and between gorgonian species. Species diversity and evenness were lower on panels with gorgonian branches. Growth of erect algae and recruitment of serpulid polychaetes were also affected by the presence of the gorgonians, primarily at Tavolara. Crustose coralline algae and erect sponges were more abundant on E. cavolinii panels at 24 m depth, while encrusting bryozoans were more abundant on P. clavata panels at 40 m depth. Effects of gorgonians on recruited assemblages could be due to microscale modification of hydrodynamics and sediment deposition rate, or by a shading effect reducing light intensity. Gorgonians may also intercept settling propagules, compete for food with the filter-feeders and/or for space by producing allelochemicals. Presence of gorgonians mainly limits the growth of erect algae and enhances the abundance of encrusting algae and sessile invertebrates. Therefore, the gorgonian disappearances may cause a shift from assemblages characterised by crustose coralline algae to filamentous algae assemblages, decreasing complexity and resilience of coralligenous bioconstructions.

Macroinvertebrate Prey Availability and Fish Diet Selectivity in Relation to Environmental Variables in Natural and Restoring North San Francisco Bay Tidal Marsh Channels

Tidal marsh wetlands provide important foraging habitat for a variety of estuarine fishes. Prey organisms include benthic–epibenthic macroinvertebrates, neustonic arthropods, and zooplankton. Little is known about the abundance and distribution of interior marsh macroinvertebrate communities in the San Francisco Estuary (estuary). We describe seasonal, regional, and site variation in the composition and abundance of neuston and benthic–epibenthic macroinvertebrates that inhabit tidal marsh channels, and relate these patterns to environmental conditions. We also describe spatial and temporal variation in diets of marsh-associated inland silverside, yellowfin goby, and western mosquitofish. Fish and invertebrates were sampled quarterly from October 2003 to June 2005 at six marsh sites located in three river systems of the northern estuary: Petaluma River, Napa River, and the west Delta. Benthic/epibenthic macroinvertebrates and neuston responded to environmental variables related to seasonal changes (i.e., temperature, salinity), as well as those related to marsh structure (i.e., vegetation, channel edge). The greatest variation in abundance occurred seasonally for neuston and spatially for benthic–epibenthic organisms, suggesting that each community responds to different environmental drivers. Benthic/epibenthic invertebrate abundance and diversity was lowest in the west Delta, and increased with increasing salinity. Insect abundance increased during the spring and summer, while Collembolan (springtail) abundance increased during the winter. Benthic/epibenthic macroinvertebrates dominated fish diets, supplemented by insects, with zooplankton playing a minor role. Diet compositions of the three fish species overlapped considerably, with strong selection indicated for epibenthic crustaceans—a surprising result given the typical classification of Menidia beryllina as a planktivore, Acanthogobius flavimanus as a benthic predator, and Gambusia affinis as a larvivorous surface-feeder. Fish diets were influenced by position along the estuarine gradient and season. Overall, our data show that local-scale site effects and marsh position within the estuary influence invertebrate community composition and abundance. Additionally, we show that restoring marsh ecosystems can subsidize fishes similarly to reference marshes. We, thus, recommend that managers focus on the ability of restoring marshes to produce food subsidies for target species when planning and designing tidal marsh restoration projects, especially those targeted for food web support.

New Ediacara fossils preserved in marine limestone and their ecological implications

Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preserved in sandstones and siltstones. Here we report several iconic Ediacara fossils and an annulated tubular fossil (reconstructed as an erect epibenthic organism with uniserial arranged modular units), from marine limestone of the 551–541 Ma Dengying Formation in South China. These fossils significantly expand the ecological ranges of several key Ediacara taxa and support that they are marine organisms rather than terrestrial lichens or microbial colonies. Their close association with abundant bilaterian burrows also indicates that they could tolerate and may have survived moderate levels of bioturbation.