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Levin, LA, Nittrouer CA.  1987.  Textural characteristics of sediments on deep seamounts in the eastern Pacific Ocean between 10°N and 30°N. Seamounts, islands, and atolls. ( Keating BH, Fryer P, Batiza R, Boehlert GW, Eds.).:187-203., Washington, D.C.: American Geophysical Union Abstract
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Levin, LA, James DW, Martin CM, Rathburn AE, Harris LH, Michener RH.  2000.  Do methane seeps support distinct macrofaunal assemblages? Observations on community structure and nutrition from the northern California slope and shelf Marine Ecology-Progress Series. 208:21-39.   10.3354/meps208021   AbstractWebsite

Although the conspicuous epifauna of reducing environments are known to exhibit strong morphological, physiological, and nutritional adaptations for life in these habitats, it is less clear whether infaunal organisms do so as well. We examined metazoan macrofauna from methane-seep sediments on the northern California slope (500 to 525 m depth) and from seep and non-seep sediments at 3 locations on the shelf (31 to 53 m depth) to determine whether the community structure and nutritional sources of seep infauna were distinct from those in non-seep, margin sediments. Seep macrofauna consisted mainly of normal slope and shelf species found in productive settings. Several macrofaunal taxa, such as Capitella sp., Diastylopsis dawsoni, and Synidotea angulata, exhibited a preference for seeps. Other taxa, such as the amphipods Rhepoxynius abronius and R, daboius, avoided seeps. Species richness of shelf macrofauna, evaluated by rarefaction and diversity indices (H' and J'), generally did not differ in seep and non-seep sediments. Similarly, stable isotopic composition (delta C-13, delta N-15) Of active seep and non-seep macrofauna did not differ at the 3 shelf sites. Stable isotopic analyses of calcareous material confirmed the presence of methane-influenced pore waters at the slope study site. At one slope clam bed, macrofaunal delta C-13 signatures were lower and delta N-15 values were higher than at another clam bed, inactive slope sediments and shelf sites. However, only 1 of 14 macrofaunal taxa (a dorvilleid polychaete) exhibited isotopic evidence of chemosynthetic nutritional sources. At these sites, seep influence on the ecology of continental margin infauna appears spatially limited and relatively subtle. At their current level of activity, the northern California slope and shelf seeps appear to function as ephemeral, small-scale disturbances that are not sufficiently persistent to allow chemosynthesis-based trophic specialization by most infauna. Rather, we suggest that many of the infauna inhabiting these seep sediments are shelf and slope species preadapted to organic-rich, reducing environments.

Levin, LA, McGregor AL, Mendoza GF, Woulds C, Cross P, Witte U, Gooday AJ, Cowie G, Kitazato H.  2013.  Macrofaunal colonization across the Indian margin oxygen minimum zone. Biogeosciences. 10:7161-7177.   10.5194/bg-10-7161-2013   AbstractWebsite

There is a growing need to understand the ability of bathyal assemblages to recover from disturbance and oxygen stress, as human activities and expanding oxygen minimum zones increasingly affect deep continental margins. The effects of a pronounced oxygen minimum zone (OMZ) on slope benthic community structure have been studied on every major upwelling margin; however, little is known about the dynamics or resilience of these benthic populations. To examine the influence of oxygen and phytodetritus on shortterm settlement patterns, we conducted colonization experiments at 3 depths on the West Indian continental margin. Four colonization trays were deployed at each depth for 4 days at 542 and 802 m (transect 1-16 degrees 58 ' N) and for 9 days at 817 and 1147 m (transect 2-17 degrees 31 ' N). Oxygen concentrations ranged from 0.9 mu M (0.02 mLL(-1)) at 542 m to 22 mu M (0.5 mLL(-1) ) at 1147 m. All trays contained local defaunated sediments; half of the trays at each depth also contained C-13/N-15-labeled phytodetritus mixed into the sediments. Sediment cores were collected between 535 m and 1140 m from 2 cross-margin transects for analysis of ambient (source) macrofaunal (> 300 mu m) densities and composition. Ambient macrofaunal densities ranged from 0 ind m(-2) (at 535-542 m) to 7400 ind m(-2), with maximum values on both transects at 700-800 m. Macrofaunal colonizer densities ranged from 0 ind m(-2) at 542 m, where oxygen was lowest, to average values of 142 ind m(-2) at 800 m, and 3074 ind m(-2) at 1147 m, where oxygen concentration was highest. These were equal to 4.3 and 151% of the ambient community at 800 m and 1147 m, respectively. Community structure of settlers showed no response to the presence of phytodetritus. Increasing depth and oxygen concentration, however, significantly influenced the community composition and abundance of colonizing macrofauna. Polychaetes constituted 92.4% of the total colonizers, followed by crustaceans (4.2%), mollusks (2.5%), and echinoderms (0.8%). The majority of colonizers were found at 1147 m; 88.5% of these were Capitella sp., although they were rare in the ambient community. Colonists at 800 and 1147 m also included ampharetid, spionid, syllid, lumbrinerid, cirratulid, cossurid and sabellid polychaetes. Consumption of C-13/N-15-labeled phytodetritus was observed for macrofaunal foraminifera (too large to be colonizers) at the 542 and 802/817 m sites, and by metazoan macrofauna mainly at the deepest, better oxygenated sites. Calcareous foraminifera (Uvigerina, Hoeglundina sp.), capitellid polychaetes and cumaceans were among the major phytodetritus consumers. These preliminary experiments suggest that bottom-water oxygen concentrations may strongly influence ecosystem services on continental margins, as reflected in rates of colonization by benthos and colonizer processing of carbon following disturbance. They may also provide a window into future patterns of settlement on the continental slope as the world's oxygen minimum zones expand.

Levin, LA.  1983.  Drift tube studies of bay-ocean water exchange and implications for larval dispersal. Estuaries. 6:364-371.   10.2307/1351395   AbstractWebsite

Surface water transport and larval dispersal potential within Mission Bay, San Diego, California and along the southern California coast were studied with drift test tubes. Drift tubes, released once during each season at six sites inside Mission Bay, traveled up to 173 km north and 205 km south of Mission Bay at maximum rates of 36 cm per s (north) and 50 cm per s (south). These findings were used to estimate probability of larval transport out of Mission Bay for the intertidal spionid polychaete Pseudopolydora paucibranchiata (Okuda) which occurred in the back of the bay. Outer coast drift tube returns were used to determine potential for gene flow, via larval exchange, between populations in isolated bays along the California coast. Drift tube recoveries and larval abundances in the plankton indicate that few Pseudopolydora larvae leave Mission Bay, but that longshore currents can carry those which do to other suitable bay habitats.

Levin, LA, Dibacco C.  1995.  Influence of sediment transport on short-term recolonization by seamount infauna. Marine Ecology-Progress Series. 123:163-175.   10.3354/meps123163   AbstractWebsite

Rates and mechanisms of infaunal recolonization in contrasting sediment transport regimes were examined by deploying hydrodynamically unbiased colonization trays at 2 sites similar to 2 km apart on the flat summit plain of Fieberling Guyot in the eastern Pacific Ocean. Both study sites experienced strong bottom currents and high shear velocity (u* exceeding 1.0 cm s(-1) daily). Macrofaunal recolonization of defaunated sediments on Fieberling Guyot was slow relative to observations in shallow-water sediments, but rapid compared to other unenriched deep-sea treatments. Microbial colonization was slower but macrofaunal colonization was faster at White Sand Swale (WSS, 585 m), where rippled foraminiferal sands migrate daily, than at Sea Pen Rim (SPR, 635 m), where the basaltic sands move infrequently. Total densities of macrofaunal colonizers at WSS were 31 and 75% of ambient after 7 wk and 6.4 mo, respectively; at SPR they were 6 and 49% of ambient, respectively. Over 3/4 of the colonists were polychaetes (predominantly hesionids and dorvilleids) and aplacophoran molluscs. Species richness of colonizers was comparable at SPR and WSS and did not differ substantially from ambient. Most of the species (91%) and individuals (95%) recovered in colonization trays were taxa present in background cores. However, only 25% of the taxa colonizing tray sediments occurred in trays at both WSS and SPR. Sessile species, carnivores and surface feeders were initially slow to appear in colonization trays, but after 6.4 mo, colonizer feeding modes, life habits and mobility patterns mirrored those in ambient sediments at WSS and SPR. Defaunated sediments were colonized by larvae, juveniles and adults at both sites. These experiments provide the first observations of infaunal colonization on seamounts, and in deep, high-energy settings. Passive bedload transport appears to be a dominant colonization mechanism in unstable foraminiferal sands at WSS. Based on the rapid recovery of infauna in trays and low diversity at WSS, we infer that disturbance is a natural feature of this site and that the ambient fauna of WSS retains features of early succession. Infaunal colonization is slower in the stable substrate at SPR, where physical disturbance may occur much less frequently.

Levin, LA, Dayton PK.  2009.  Ecological theory and continental margins: where shallow meets deep. Trends in Ecology & Evolution. 24:606-617.   10.1016/j.tree.2009.04.012   AbstractWebsite

Continental margins, where land becomes ocean and plunges to the deep sea, provide valuable food and energy resources, and perform essential functions such as carbon burial and nutrient cycling. They exhibit remarkably high species and habitat diversity, but this is threatened by our increasing reliance on the resources that margins provide, and by warming, expanding hypoxia and acidification associated with climate change. Continental margin ecosystems, with environments, constituents and processes that differ from those in shallow water, demand a new focus, in which ecological theory and experimental methods are brought to bear on management and conservation practices. Concepts of disturbance, diversity-function relationships, top-down versus bottom-up control, facilitation and meta-dynamics offer a framework for studying fundamental processes and understanding future change.

Levin, LA, Huggett CL, Wishner KF.  1991.  Control of deep-sea benthic community structure by oxygen and organic-matter gradients in the eastern Pacific Ocean. Journal of Marine Research. 49:763-800.   10.1357/002224091784995756   AbstractWebsite

At boundaries of oxygen minimum zones (OMZs), bathyal faunas experience steep gradients in oxygen and organic-matter availability. The present study compares changes in microbial, meiofaunal, macrofaunal and megafaunal benthic assemblages along these gradients on Volcano 7, a 2.3-km high seamount in the eastern tropical Pacific. Faunal tolerance to dysaerobic (low oxygen) conditions varies with organism size; microbial and meiofaunal abundances are less affected than macro- and megafaunal abundances. At the exceedingly low concentrations (< 0.1 ml/1) encountered on the upper summit of Volcano 7, oxygen appears to exert primary control over abundance, composition and diversity of macrofauna, overriding other factors such as food availability and sediment grain size. When oxygen concentration is sufficient, food availability in sediments (indicated by the presence of labile material such as chlorophyll a) is highly correlated with meiofaunal and macrofaunal abundance. Four distinct physical zones were identified on Volcano 7: (1) the coarse-grained upper summit zone (730-770 m) where near-bottom oxygen concentrations were usually lowest (often < 0.1 ml/1) and organic-matter (% organic carbon and chlorophyll a) availability was high, (2) the coarse-grained lower summit (770-1000 m) where near-bottom oxygen concentrations were usually slightly higher (0.11 to 0.16 ml/1) and organic-matter availability remained high, (3) the coarse-grained flank (1000-2000 m) where oxygen concentration was intermediate (0.7-0.9 ml/1) and sediment organic-matter content was very low, and (4) the finer-grained base (2000-3500 m) where oxygen values exceeded 2.5 ml/1, sediment organic carbon was moderate, and chlorophyll a was low. Abundances of larger forms (megafauna and macrofauna) were severely reduced on the upper summit, but attained high values (2.25/m2 and 8,457/m2 respectively) just tens of meters below. The smaller forms (bacteria and meiofauna) attained peak abundances on the low-oxygen upper summit, however, abundances of harpacticoid copepods were greatly reduced on the upper and lower summit, presumably due to oxygen limitation. Macrofaunal abundance and diversity patterns along the Volcano 7 oxygen/enrichment gradient resembled those typically observed along shallow-water gradients of organic pollution. Low densities of a few soft-bodied, low-oxygen tolerant species resided on the upper summit, a high-density, low-diversity assemblage inhabited the lower summit, and low-density, high-diversity assemblages occupied the flank and base sediments. The infaunal communities on Volcano 7 support the idea that OMZ boundaries are regions of enhanced biological activity. Modern faunal distributions and biogenic structures at OMZ boundaries may be useful in reconstructing oxygenation histories of ancient marine basins.

Levin, LA, Talley TS.  2002.  Natural and manipulated sources of heterogeneity controlling early faunal development of a salt marsh. Ecological Applications. 12:1785-1802.   10.2307/3099938   AbstractWebsite

Ecosystem recovery following wetland restoration offers exceptional opportunities to study system structure, function, and successional processes in salt marshes. This study used observations of natural variation and large-scale manipulative experiments to test the influence of vascular vegetation and soil organic matter on the rate and trajectory of macrofaunal recovery in a southern California created salt marsh, the Crown Point Mitigation Site. During the first three years following marsh establishment, macrofaunal density and species richness recovered rapidly within the Spartina foliosa (cordgrass) zone; densities in the created marsh were 50% of those in the natural marsh after 16 mo and 97% after 28 mo. However, the early successional assemblage had a lower proportion of tubificid and enchytraeid oligochaetes, and a higher proportion of chironomids and other insect larvae than did the mature natural marsh. Most of the colonizers arrived by rafting on sea grass and algae rather than by larval dispersal. Initial planting of S. foliosa had no influence on macrofaunal recovery, perhaps because of variable transplant survival. However, subsequently, both positive and negative correlations were observed between densities of some macrofaunal taxa and shoot densities of S. foliosa or Salicornia spp. (pickleweed). Salinity and measures of soil organics (belowground biomass, combustible organic matter, and chlorophyll a) also were correlated with macrofaunal densities and taxon richness. Of foul added soil amendments (kelp, alfalfa, peat, and Milorganite), Milorganite (a sewage product) and kelp both promoted macrofaunal colonization during year 1, but effects were short lived. The most significant sources of heterogeneity in the recovering marsh were associated with site history and climate variation. Faunal recovery was most rapid in highly localized, organic-rich marsh sediments that were remnants of the historical wetland. Elevated sea level during the 1998 El Nino corresponded with similarity of macrofaunal communities in the created and natural marshes. The large spatial scale and multi-year duration of this study revealed that natural sources of spatial and temporal heterogeneity may exert stronger influence on faunal succession in California wetlands than manipulation of vegetation or soil properties.

Levin, LA, Baco AR, Bowden DA, Colaco A, Cordes EE, Cunha MR, Demopoulos AWJ, Gobin J, Grupe BM, Le J, Metaxas A, Netburn AN, Rouse GW, Thurber AR, Tunnicliffe V, Van Dover CL, Vanreusel A, Watling L.  2016.  Hydrothermal vents and methane seeps: Rethinking the sphere of influence. Frontiers in Marine Science. 3   10.3389/fmars.2016.00072   AbstractWebsite

Although initially viewed as oases within a barren deep ocean, hydrothermal vent and methane seep communities are now recognized to interact with surrounding ecosystems on the sea floor and in the water column, and to affect global geochemical cycles. The importance of understanding these interactions is growing as the potential rises for disturbance from oil and gas extraction, seabed mining and bottom trawling. Here we synthesize current knowledge of the nature, extent and time and space scales of vent and seep interactions with background systems. We document an expanded footprint beyond the site of local venting or seepage with respect to elemental cycling and energy flux, habitat use, trophic interactions, and connectivity. Heat and energy are released, global biogeochemical and elemental cycles are modified, and particulates are transported widely in plumes. Hard and biotic substrates produced at vents and seeps are used by “benthic background” fauna for attachment substrata, shelter, and access to food via grazing or through position in the current, while particulates and fluid fluxes modify planktonic microbial communities. Chemosynthetic production provides nutrition to a host of benthic and planktonic heterotrophic background species through multiple horizontal and vertical transfer pathways assisted by flow, gamete release, animal movements, and succession, but these pathways remain poorly known. Shared species, genera and families indicate that ecological and evolutionary connectivity exists among vents, seeps, organic falls and background communities in the deep sea; the genetic linkages with inactive vents and seeps and background assemblages however, are practically unstudied. The waning of venting or seepage activity generates major transitions in space and time that create links to surrounding ecosystems, often with identifiable ecotones or successional stages. The nature of all these interactions is dependent on water depth, as well as regional oceanography and biodiversity. Many ecosystem services are associated with the interactions and transitions between chemosynthetic and background ecosystems, for example carbon cycling and sequestration, fisheries production, and a host of non-market and cultural services. The quantification of the sphere of influence of vents and seeps could be beneficial to better management of deep-sea environments in the face of growing industrialization.

Levin, LA, Demaster DJ, McCann LD, Thomas CL.  1986.  Effects of giant protozoans (Class Xenophyophorea) on deep-seamount benthos. Marine Ecology-Progress Series. 29:99-104.   10.3354/meps029099   AbstractWebsite

Biogenic sediment structures have been proposed to enhance diversity in deep-sea sediments. To evaluate this hypothesis we examined the influence of xenophyophores, giant sediment-agglutinating protozoans, on the structure of metazoan communities inhabiting sediments of deep (1000 to 3300 m) seamounts in the eastern Pacific Ocean. Xenophyophores provided habitat for 16 major metazoan taxa. Sediments immediately surrounding xenophyophores exhibited elevated faunal densities and species richness relative to control sediments collected 1 m from the tests. Amphipods were exclusively associated with the protozoan tests or sediments beneath them. Crustaceans, molluscs, and echinoderms exhibited enhanced infaunal densities in the presence of xenophyophores but polychaetes did not. Both horizontal and vertical distributions of infauna appear to be influenced by these protozoans. 234Th measurements suggest that xenophyophores and their associated fauna increase the particle flux of fine-grained material to the seabed and enhance subsurface mixing on a 100 d time scale. We propose that xenophyophores alter hydrodynamic conditions and provide deep-sea metazoans with substrate, food, and refuge. The resulting habitat heterogeneity may contribute to maintenance of high benthic diversity.

Levin, LA, Talley TS, Hewitt J.  1998.  Macrobenthos of Spartina foliosa (Pacific cordgrass) salt marshes in southern California: Community structure and comparison to a Pacific mudflat and a Spartina alterniflora (Atlantic smooth cordgrass) marsh. Estuaries. 21:129-144.   10.2307/1352552   AbstractWebsite

Environmental attributes (vegetation and sediment properties) of and macrofaunal community structure in sediments of five southern California Spartina foliosa marshes (San Diego Bay, Mission Bay, Upper Newport Bay, Bolsa Chica Lagoon, and Anaheim Bay) were examined during October 1994. Macrofaunal densities in Pacific S. foliosa marshes (avg. 122,268 indiv. m(-2) > 300 mu m) were 3 to 10 times higher than observed in Atlantic S. alterniflora and S. anglica marshes. The macrofauna of S. foliosa marshes was composed mainly of enchytraeid, naidid, and tubificid oligochaetes (66%), with the enchytraeids dominant at all sites except Bolsa Chica Lagoon. Polychaetes, insects, and peracarid crustaceans accounted for most of the remaining fauna. Multivariate analyses indicated greatest faunal similarity between the two southernmost marshes (Mission Bay and San Diego Bay), and between Anaheim and Newport Bay marshes, with Bolsa Chica Lagoon exhibiting a distinct assemblage. There were strong positive associations of faunal abundance and composition with percent organic matter and percent open area, and negative associations with percent sand and dry weight of algae. For the vegetated marsh in Mission Bay, faunal comparisons were made with an adjacent mudflat and with a S. alterniflora marsh in North Carolina, USA. The unvegetated mudflat exhibited similar macrofaunal densities but higher species richness than the adjacent Spartina marsh. The macrofaunal assemblage of the Mission Bay S. foliosa marsh differed from that of the Atlantic S. alterniflora marsh and the Pacific mudflat in having a greater proportion of oligochaetes, especially Enchytraeidae, and fewer polychaetes. This study represents the first published description that we are aware of for macrofauna in S. foliosa vegetated marsh sediments. The findings document faunal variation among southern California embayments and suggest that differences in macrobenthic community structure occur between marsh and mudflat habitat as web as between east and west coast Spartina marshes. Observed differences may have significant implications for wetland conservation and restoration efforts.

Levin, LA, Sibuet M.  2012.  Understanding Continental Margin Biodiversity: A New Imperative. Annual Review of Marine Science, Vol 4. 4( Carlson CA, Giovannoni SJ, Eds.).:79-+., Palo Alto: Annual Reviews   10.1146/annurev-marine-120709-142714   Abstract

Until recently, the deep continental margins (200-4,000 m) were perceived as monotonous mud slopes of limited ecological or environmental concern. Progress in seafloor mapping and direct observation now reveals unexpected heterogeneity, with a mosaic of habitats and ecosystems linked to geomorphological, geochemical, and hydrographic features that influence biotic diversity. Interactions among water masses, terrestrial inputs, sediment diagenesis, and tectonic activity create a multitude of ecological settings supporting distinct communities that populate canyons and seamounts, high-stress oxygen minimum zones, and methane seeps, as well as vast reefs of cold corals and sponges. This high regional biodiversity is fundamental to the production of valuable fisheries, energy, and mineral resources, and performs critical ecological services (nutrient cycling, carbon sequestration, nursery and habitat support). It is under significant threat from climate change and human resource extraction activities. Serious actions are required to preserve the functions and services provided by the deep-sea settings we are just now getting to know.

Levin, LA.  1981.  Dispersion, feeding behavior and competition in two spionid polychaetes. Journal of Marine Research. 39:99-117. AbstractWebsite

Spatial analysis, laboratory and field experiments, and feeding observations indicate contrasting patterns of aggression in the polychaetes Pseudopolydora paucibranchiata (Okuda) and Streblospio benedicti (Webster) and provide the 1st evidence of territoriality in a spionid polychaete (Pseudopolydora). On the intertidal mudflats of Mission Bay in San Diego, California, Pseudopolydora is spaced more evenly than expected from a random distribution; the dispersion of Streblospio does not depart significantly from random. Recruitment patterns in Pseudopolydora indicate that uniform spacing is initiated during settlement and enhanced by subsequent interactions between individuals. Field manipulations provide evidence for adult interactions with settling larvae which may also play a role in generating non-random dispersion in Pseudopolydora. Differences between Pseudopolydora and Streblospia in aggressive behavior (palp fighting and biting) and feeding mechanisms are correlated with different space requirements for feeding and tube building. Laboratory observations of surface deposit and suspension feeding indicate that Pseudopolydora is more aggressive and frequently uses its mouth and palps to acquire food particles. These species differ in their site of food particle selection. Streblospio relies primarily on lips and mouth to taste particles; Pseudopolydora more frequently uses its palps. Pseudopolydora defends palp territories necessary for the acquisition of food and tube building materials. The spatial analysis, in conjunction with experimental results and behavioral observations, suggest strong competition in Pseudopolydora but not in Streblospio.

Levin, LA, Leithold EL, Gross TF, Huggett CL, Dibacco C.  1994.  Contrasting effects of substrate mobility on infaunal assemblages inhabiting two high-energy settings on Fieberling Guyot. Journal of Marine Research. 52:489-522.   10.1357/0022240943077028   AbstractWebsite

The influence of seamount-intensified flows on the structure of infaunal assemblages was examined at two sand-covered sites located 2.3 km apart atop the summit plain of Fieberling Guyot (32-degrees 27.6'N 127-degrees 48.0'W). Both sites experience strong, tidal bottom currents with flows exceeding 20 cm/ s on a daily basis (4 mab). Estimates of shear velocity (u*) did not differ significantly between the two sites. However, differences in sediment composition and density produced different sediment transport regimes at the two sites. At Sea Pen Rim (SPR), located on the NW perimeter (635 m), sedimentary particles were composed primarily of basaltic sands that experienced negligible transport during the study period. At White Sand Swale (WSS, 580 m), a narrow valley enclosed on three sides by basalt outcrops, sediments were composed almost entirely of foraminiferal sands that moved daily. Sediment organic content and microbial abundances were similar at the two sites. Infauna (> 300 mum) had higher densities at WSS (1870/m2) than SPR (1489/m2), but lower expected species richness. Although the 2 sites shared nearly 50% of identified species, peracarid crustaceans, echinoderms, sponges, and bryozoans were proportionally more important in the stable substrates of SPR, while turbellarians, bivalves, and aplacophorans were better represented in the shifting sands of WSS. The infauna of WSS lived deeper in the sediment column (> 50% below 2 cm) than that of SPR (> 50% in the upper 1 cm), at least partly because the majority (83%) at WSS were subsurface burrowers with motile lifestyles. Tube-building and epifaunal lifestyles were more common at SPR than WSS, as were surface-deposit and filter-feeding modes. Fences and weirs were deployed at the study sites for 6.5-wk and 6-mo periods to manipulate bottom stress. Changes in faunal patterns within weirs at WSS reinforced our conjecture that contrasting sediment transport regimes explain between-site differences in community structure. Fence effects varied with deployment period and site. Topographic features on Fieberling Guyot produce heterogeneous sedimentary settings characterized by different transport regimes. Our results suggest that substrate mobility exerts primary control over infaunal community structure at the two high-energy sites.

Levin, LA, Neira C, Grosholz ED.  2006.  Invasive cordgrass modifies wetland trophic function. Ecology. 87:419-432.   10.1890/04-1752   AbstractWebsite

Vascular plants strongly control belowground environments in most ecosystems. Invasion by vascular plants in coastal wetlands, and by cordgrasses (Spartina spp.) in particular, are increasing in incidence globally, with dramatic ecosystem-level consequences. We examined the trophic consequences of' invasion by a Spartina hybrid (S. alterniflora X S. foliosa) in San Francisco Bay (USA) by documenting differences in biomass and trophic structure of benthic communities between sediments invaded by Spartina and uninvaded sediments. We found the invaded system shifted from all algae-bascd to a detritus-based food web. We then tested for a relationship between diet and tolerance to invasion, hypothesizing that species that consume Spartina detritus are more likely to inhabit invaded sediments than those that consume surface algae. Infaunal diets were initially examined with natural abundance stable isotope analyses and application of mixing models, but these yielded an ambiguous picture of food sources. Therefore, we conducted isotopic enrichment experiments by providing N-15-labeled Spartina detritus both on and below the sediment surface in areas that either contained Spartina or were unvegetated. Capitellid and nereid polychaetes, and oligochaetes, groups shown to persist following Spartina invasion of San Francisco Bay tidal flats, took up N-15 from labeled native and invasive Spartina detritus. In contrast, We found that amphipods, bivalves, and other taxa less tolerant to invasion consumed primarily surficial algae, based oil C-13 enrichment experiments. Habitat (Spartina vs. unvegetated patches) and location of' detritus (on or within sediments) did not affect N-15 uptake from cletritus. Our investigations support a "trophic shift" model for ecosystem response to wetland plant invasion and preview loss of key trophic support for fishes and migratory birds by shifting dominance to species not widely consumed by species at higher trophic levels.

Levin, LA, Huggett DV.  1990.  Implications of alternative reproductive modes for seasonality and demography in an estuarine polychaete. Ecology. 71:2191-2208.   10.2307/1938632   AbstractWebsite

The consequences of alternative developmental patterns for the seasonal dynamics and demography of benthic marine invertebrates were examined by comparing two local demes (1.5 km apart) of the polychaete Streblospio benedicti Webster (Spionidae). One was dominated by individuals exhibiting planktotrophy, where large numbers of offspring develop from small eggs as feeding larvae, and the other was dominated by individuals exhibiting lecithotrophy, in which fewer numbers of larvae develop from large eggs without feeding. Over a 2.5-yr period we studied development mode, benthic abundances, recruitment, recolonization of disturbed areas, size structure, and reproductive output at the two sites, to evaluate possible effects of larval development mode on: (a) level of population fluctuation, (b) colonization ability, (c) secondary production, and (d) demographic properties. Size-structured population models were used to evaluate seasonal and annual population growth rates (@l). Sensitivity and life-table response analyses were carried out to examine the relative contribution of fecundity and survivorship to differences in @l between demes and among seasons. Strong similarity was observed between planktotroph- and lecithotroph-dominated demes in magnitude and timing of fluctuations in recruitment and total abundance, in benthic population size structure, and in secondary production, average production: biomass ratio, and annual population growth rates. S. benedicti data and a review of the literature provide no support for Thorson's (1950) hypothesis that species with planktotrophic development experience much greater levels of population fluctuation than those with lecithotropic development. However, in this study the planktotrophs exhibited superior colonization ability. They also exhibited stronger seasonality and more variability in production and some demographic properties. These factors combined suggest that populations with planktotrophic development should exhibit different patch dynamics than those with lecithotrophic development. The lecithotroph-dominated deme exhibited a consistent survivorship advantage in larval and juvenile stages that was balanced almost precisely in the planktotroph-dominated deme by a fecundity advantage in early adult stages. This led to similar population growth rates (@l wk^-^1), calculated from annual projection matrices, at both sites in both years (range: 1.004 to 1.078 wk^-^1). At both sites seasonal (cohort) population growth rates were lowest in spring (0.46-0.76) and highest in early summer and fall (usually @>1.10). Population growth potential for the plankotroph-dominated deme was always greater than for the lecithotroph-dominated deme in early summer; the reverse was true for the fall, overwintering cohort. Comparison of this study with an age-structured analysis of laboratory-reared S. benedicti populations from the same location, but subject to excess food and no predation or seasonality (Levin et al. 1987), revealed greatest demographic similarity between the lab populations and the fall, overwintering cohort from the field. The similar demographic consequences of planktotrophy and lecithotrophy have significance for efforts to model the evolution of life-history patterns, and for understanding the intraspecific and interspecific occurrence of contrasting developmental modes.

Levin, LA, Gooday AJ, James DW.  2001.  Dressing up for the deep: agglutinated protists adorn an irregular urchin. Journal of the Marine Biological Association of the United Kingdom. 81:881-882.   10.1017/s0025315401004738   AbstractWebsite

A specimen of the deep-water, spatangoid urchin. Cystochinus loveni, wearing a costume of agglutinated protists, was collected from 3088 m in the Gulf of Alaska, north-east Pacific. Over 24 putative taxa of living and dead foraminiferans and xenophyophores, as well as a sipunculan.. polychaete tanaid, and two isopods, were collected from the dorsal surface of this single individual, This is the first report of a deep-sea urchin using rhizopod protists and it is proposed that the urchin acquires camouflage or benefits from increased specific gravity associated with the protistan cloak.

Levin, LA, Honisch B, Frieder CA.  2015.  Geochemical proxies for estimating faunal exposure to ocean acidification. Oceanography. 28:62-73.   10.5670/oceanog.2015.32   AbstractWebsite

Growing concern over the impacts of modern ocean acidification (OA) and interest in historical pH excursions have intensified the development of geochemical proxies for organism exposure to acidification and other components of the carbonate system. The use of carbonate structures produced by foraminifers, coccolithophores, corals, mollusks, brachiopods, echinoderms, ostracods, and fish for paleoreconstructions is an active area of study, and the resulting proxy development offers new opportunities for studying modern faunal exposures. Here we review information from field studies and laboratory experiments on carbonate system geochemical proxies in protists and metazoa. Geochemical proxy development for foraminifers and corals is most advanced; studies of fish and echinoderms are in their infancy. The most promising geochemical proxies are those with a mechanistic link to changes in seawater carbonate chemistry, such as boron isotopes (delta B-11), B/Ca, and U/Ca ratios recorded in skeletal hard parts. We also discuss indirect geochemical proxies (other trace elements and carbonate polymorphs) along with their potential uses and limitations due to modification by physiological processes, precipitation rate, and degree of calcification. Proxy measurements in modern skeletal structures, otoliths, statoliths, and other hard parts could reveal environmental exposures of organisms from larval through adult stages, and could advance inferences about effects of OA (and other stressors) on survival, growth, population connectivity, and other ecological attributes. Use of geochemical proxies in live, field-collected organisms is an underutilized and underdeveloped approach to studying OA consequences, but it may offer a powerful, complementary approach to laboratory observations.

Levin, LA.  1986.  Effects of enrichment on reproduction in the opportunistic polychaete Streblospio benedicti (Webster): a mesocosm study. Biological Bulletin. 171:143-160.   10.2307/1541913   AbstractWebsite

The influence of organic enrichment on growth and planktotrophic development of the spionid polychaete Streblospio benedicti Webster was examined in two mesocosm experiments conducted at the MERL facility, University of Rhode Island. Specimens of S. benedicti were collected and their reproductive traits monitored near the conclusion of a two-year eutrophication experiment, and in the middle of a sludge addition experiment. Nutrient (N, P, and Si) enrichments at 8× and 32× the average aerial input into Narragansett Bay, Rhode Island, resulted in increases in body length, segment number, and length per segment, and a doubling of brood size in S. benedicti females. These increases were substantially higher during May (12°C) than August (20°C). Enrichment effects were stronger in the 8× than 32× nutrient treatment. In the sewage sludge experiment body size increased 20% over control values at the highest (8×) sludge treatment level (nitrogen loading equivalent to the 8× nutrient treatment) but no significant increase was noted at the 4× sludge level, which received half as much nitrogen as the 8× sludge treatment. Mean brood size increased by a factor of 4.6 over controls in the 8× sludge treatment and by a factor of 2.3 in the 4× sludge treatment. Within the range of adult body sizes observed, brood size enhancement occurred independent of increased length or segment number in both nutrient and sludge enrichment treatments. The ability to translate elevated food supply directly into increased reproductive output may underly opportunistic dynamics in macrobenthos. Brood size enhancement of the magnitude observed probably contributes to the high S. benedicti densities found in polluted or organically enriched settings.

Levin, LA, Edesa S.  1997.  The ecology of cirratulid mudballs on the Oman margin, northwest Arabian Sea. Marine Biology. 128:671-678.   10.1007/s002270050134   AbstractWebsite

Mudball-building cirratulid polychaetes have been described previously only from the southern California margin. During a study of oxygen minimum-zone benthos in fall 1994, we observed dense aggregations of agglutinated mudballs at 840 to 875 m on the Oman margin in the northwest Arabian Sea. These were inhabited, and probably constructed, by a cirratulid polychaete species in the genus Monticellina. The mudballs were cigar-shaped, 4.5 to 25 mm long, and positioned vertically so as to protrude several millimeters above the sediment-water interface. Total mudball densities were similar to 16000 m(-2). Occupied mudballs occurred at densities of 2112 m(-2); 89% were in the uppermost 2 cm of sediment, and no occupied mudballs were found below 10 cm. Organisms other than the cirratulid were present on 1.7% of the mudballs examined, and included epizoic polychaetes, agglutinated and calcareous Foraminifera. Various polychaetes, a nemertean and nematodes were found inside tests. Mudball abundance exhibited positive associations with densities of several paraonid polychaete species, and with densities of burrowing and subsurface-deposit-feeding polychaetes. Negative associations were observed between mudballs and three tube-building taxa (two polychaetes and an amphipod). Mudball-inhabiting cirratulids are abundant in at least two low-oxygen, margin settings. We expect further sampling of bathyal environments to yield additional systems in which cirratulid mudballs are common. Such observations are valuable because mudballs appear to represent a significant source of heterogeneity that can influence macrofaunal community structure in deep-sea sediments.

Levin, LA, Mendoza GF, Gonzalez JP, Thurber AR, Cordes EE.  2010.  Diversity of bathyal macrofauna on the northeastern Pacific margin: the influence of methane seeps and oxygen minimum zones. Marine Ecology-an Evolutionary Perspective. 31:94-110.   10.1111/j.1439-0485.2009.00335.x   AbstractWebsite

The upper continental slope in the northeastern Pacific Ocean is intercepted by a deep oxygen minimum zone (OMZ; 650-1100 m) and punctuated by conduits of methane seepage. We examined the effects of these two dominant sources of heterogeneity on the density, composition and diversity of heterotrophic macrofauna off Hydrate Ridge, Oregon (OR; 800 m water depth), where the seeps co-occur within an OMZ, and off the Eel River, Northern California (CA; 500 m), where seeps are overlain by better oxygenated waters. We hypothesized that seeps (containing clam beds and microbial mats) should contribute a suite of distinct species to the regional margin species pool but that OMZ-associated hypoxia would dampen seep-related heterogeneity. Macrofaunal densities were highest (23,000-33,510 ind.m(-2)) in the CA seep sediments and in the OR near-seep samples, intermediate in the OR seep, CA near seep and CA and OR 500-m margin sediments (10,05419,777 ind.m(-2)), and lowest in the CA and OR OMZ habitats at 800 m (42697847 ind.m(-2)). Annelids constituted over 50% of the taxa in all but the CA clam bed and OR microbial mat sediments, where mollusks were abundant. Approximately 50% of seep species appeared to be habitat endemic; species present in microbial mats largely formed a subset of those present in the clam beds. Dorvilleid and ampharetid polychaetes were dominant in the seep sediments; non-seep margin sediments at 500 and 800 m were populated heavily by branckiate polychaetes including cossurids and paraonids. Alpha diversity (Es[20] calculated per core) was lowest and rank 1 dominance was highest in the CA and OR microbial mat habitats. Pooled analyses of Es[100] revealed highest species richness in the CA clam bed and near-seep habitats (30.3 and 29.6, respectively), and lowest species richness in the OR microbial mat and near-seep habitats (16.5 and 17.9, respectively). Non-seep sediments (500 and 800 m) off both CA and OR were more homogeneous (55-57% within-habitat similarity) than clam bed and microbial mat sediments (only 32-37% within-habitat similarity). CA sediment macrofauna generally exhibit higher alpha diversity, and as habitats are combined, a higher rate of increase in the slope of the species accumulation curves than do OR margin macrofauna. Methane seeps in the NE Pacific introduce significant heterogeneity that increases margin biodiversity at multiple spatial scales. However, our hypothesis that the OMZ would lessen the seep contributions to diversity was not supported. The better oxygenated CA seeps at 500 in shared more of the background margin fauna (at 500 m) than did the OR seeps at 800 m (with OMZ fauna at 800 in). Geographical differences in the fluxes of methane-rich fluids and the increased reliance on chemosynthetic food sources with increased depth could explain these results.

Levin, LA, Huggett D, Myers P, Bridges T, Weaver J.  1993.  Rare earth tagging methods for the study oflarval dispersal by marine invertebrates. Limnology and Oceanography. 38:346-360. AbstractWebsite

Rare-earth elements (REEs) are proposed as a label for invertebrate larvae (clams, barnacles, and polychaetes) and passive larval mimics (polystyrene spheres) to be used in field studies of larval dispersal. Different elements, their uptake levels, retention times, and effects on larval survivorship were examined to assess suitability of REEs as larval tags. Lu, Sm, and Eu were selected for labeling work based on extremely low levels in natural plankton and seawater and due to the high sensitivity of neutron activation analysis to these elements. Adequate label retention occurs on time scales of hours to days in both larvae and microspheres. Combined use of Eu-labeled microspheres and Lu- and Sm-labeled larvae in release-recapture mode offers a highly sensitive method for studying trajectories and behavior of larvae in natural settings. However, dilution factors may limit experimentation to small and intermediate spatial scales (meters to kilometers) in the field.

Levin, LA, Ziebis W, Mendoza GF, Growney VA, Tryon MD, Brown KM, Mahn C, Gieskes JM, Rathburn AE.  2003.  Spatial heterogeneity of macrofauna at northern California methane seeps: influence of sulfide concentration and fluid flow. Marine Ecology-Progress Series. 265:123-139.   10.3354/meps265123   AbstractWebsite

Relationships among fluid flow, sulfide concentration, sulfur bacteria and macrofaunal assemblages were examined at methane seeps on the northern California margin, near the mouth of the Eel River (512 to 525 m). Over a 6 mo period, sediments covered with microbial mats exhibited significant but variable outflow of altered fluids, with no flow reversals. This fluid flow was associated with high porewater sulfide concentrations (up to 20 mM) and almost no oxygen penetration of sediments (<0.1 mm). Vesicomya pacifica (clam) bed and non-seep sediments exhibited little net fluid outflow and similar oxygen penetration (3 and 4 mm, respectively); however, sulfide concentrations were higher in subsurface clam-bed sediments (up to 2 mM) than in non-seep sediments (<200 muM). Macrofaunal densities did not differ among the 3 habitats (13 800 to 16 800 ind. m(-2); >300 mum), but biomass and diversity (no. species per core, E(S-100), H') were lower and composition varied in the sulfidic microbial mat sediments relative to clam-bed and non-seep sediments. The community in microbial mat-covered sediments consisted largely (82%) of 6 species in the polychaete family Dorvilleidae, whereas the clam-bed and non-seep microhabitats supported a mixture of annelids, peracarid crustaceans, nemerteans, and mollusks. Vertical microprofiling of sulfide in animal cores indicated that most taxa avoid H2S concentrations >1 mM. However, sulfide-oxidizing filamentous bacteria, dorvilleid polychaetes and bivalves (mainly V. pacifica) exhibited highest densities at sulfide concentrations of 1 to 5 mM sulfide. Horizontal and vertical patterns of sulfide availability have a strong influence on the fine-scale distribution, structure and composition of macrofaunal assemblages inhabiting methane seeps and must be accounted for when characterizing the microbiology and ecology of seep habitats.

Levin, LA, Thomas CL.  1988.  The ecology of xenophyophores (Protista) on eastern Pacific seamounts. Deep-Sea Research Part a-Oceanographic Research Papers. 35:2003-2027.   10.1016/0198-0149(88)90122-7   AbstractWebsite

Large, agglutinating protozoans of the class Xenophyophorea are the dominant epifaunal organisms on soft and hard substrates of many bathyal seamounts in the eastern Pacific Ocean off Mexico. Observations made with the submersible Alvin and remotely towed camera sleds on 17 seamounts at 31°, 20°, 13° and 10°N revealed more than ten distinct xenophyophore test morphologies. Most of these appear to represent previously undescribed species. Reticulate forms are numerically dominant at 20°, 13° and 10°N. Xenophyophore abundances increase with decreasing latitude, being rare at 30°N, present at densities of 0.1–1.0 m−2 at 20° and 13°N and often exceeding 1.0 m−2 at 10°N, occasionally reaching 10–18 m−2. Highest concentrations are observed on caldera floors near the base of steep caldera walls, at depths between 1700 and 2500 m. Most individuals select sand-size pelagic foraminiferan tests (63–500 μm) and exclude pebble, silt and clay-size particles for test construction.Xenophyophore on seamounts modify the structure of metazoan communities and may play a role in maintenance of infaunal diversity. Twenty-seven xenophyophore tests were found to provide habitat for 16 major macrofaunal taxa (152 individuals) and three meiofaunal taxa (333 individuals). The presence of xenophyophores also enhances the abundance of isopods, tanaids, ophiuroids, nematodes and harpacticoid copepods dwelling in sediments surrounding the tests. Mobile megafauna are attracted to sediment beneath and adjacent to xenophyophores. We suggest that xenophyophores, which are abundant on many topographic features in deep water (e.g. guyots, trenches, canyons and continental slopes), are a functionally important component of deep-sea benthic communities and require further autecological and synecological investigation.

Levin, LA, Talley T.  2000.  Influences of vegetation and abiotic environmental factors on salt marsh benthos. Concepts and controversies in tidal marsh ecology. ( Weinstein M, Kreeger D, Eds.).:661-708., Dordrecht ; Boston: Kluwer Academic Abstract
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