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2018
Neira, C, Ingels J, Mendoza G, Hernandez-Lopez E, Levin LA.  2018.  Distribution of meiofauna in bathyal sediments influenced by the oxygen minimum zone off Costa Rica. Frontiers in Marine Science. 5   10.3389/fmars.2018.00448   AbstractWebsite

Ocean deoxygenation has become a topic of increasing concern because of its potential impacts on marine ecosystems, including oxygen minimum zone (OMZ) expansion and subsequent benthic effects. We investigated the influence of oxygen concentration and organic matter (OM) availability on metazoan meiofauna within and below an OMZ in bathyal sediments off Costa Rica, testing the hypothesis that oxygen and OM levels are reflected in meiofaunal community structures and distribution. Mean total densities in our sampling cores (400-1800 m water depth) were highest with 3688 ind. 10 cm(-2) at the OMZ core at 400 m water depth, decreasing rapidly downslope. Nematodes were overall dominant, with a maximum of 99.9% in the OMZ core, followed by copepods (13%), nauplii (4.8%), and polychaetes (3%). Relative copepod and nauplii abundance increased consistently with depth and increasing bottom-water O-2. Meiofaunal composition was significantly different among sites, with lower taxonomic diversity at OMZ sites relative to deeper, oxygenated sites. Vertical distribution patterns within sediments showed that in strongly oxygen-depleted sites less meiofauna was concentrated in the surface sediment than at deeper slope sites. Highest meiofaunal abundance and lowest diversity occurred under lowest oxygen and highest pigment levels, whereas highest diversity occurred under highest oxygen-concentrations and low pigments, as well as high quality of sedimentary pigment (chl a/phaeo) and organic carbon (C/N). The lower meiofaunal diversity, and lower structural and trophic complexity, at oxygen-depleted sites raises concerns about changes in the structure and function of benthic marine ecosystems in the face of OMZ expansions.

2015
Maloney, JM, Grupe BM, Pasulka AL, Dawson KS, Case DH, Frieder CA, Levin LA, Driscoll NW.  2015.  Transpressional segment boundaries in strike-slip fault systems offshore southern California: Implications for fluid expulsion and cold seep habitats. Geophysical Research Letters. 42:4080-4088.   10.1002/2015gl063778   AbstractWebsite

The importance of tectonics and fluid flow in controlling cold seep habitats has long been appreciated at convergent margins but remains poorly understood in strike-slip systems. Here we present geophysical, geochemical, and biological data from an active methane seep offshore from Del Mar, California, in the inner California borderlands (ICB). The location of this seep appears controlled by localized transpression associated with a step in the San Diego Trough fault zone and provides an opportunity to examine the interplay between fluid expulsion and restraining step overs along strike-slip fault systems. These segment boundaries may have important controls on seep locations in the ICB and other margins characterized by strike-slip faulting (e.g., Greece, Sea of Marmara, and Caribbean). The strike-slip fault systems offshore southern California appear to have a limited distribution of seep sites compared to a wider distribution at convergent plate boundaries, which may influence seep habitat diversity and connectivity.

2014
Neira, C, Levin LA, Mendoza G, Zirino A.  2014.  Alteration of benthic communities associated with copper contamination linked to boat moorings. Marine Ecology-an Evolutionary Perspective. 35:46-66.   10.1111/maec.12054   AbstractWebsite

Although copper (Cu) is an essential element for life, leaching from boat paint can cause excess environmental loading in enclosed marinas. The effects of copper contamination on benthic macrofaunal communities were examined in three San Diego Bay marinas (America's Cup, Harbor Island West and East) in Southern California, USA. The distribution of Cu concentration in sediments exhibited a clear spatial gradient, with hotspots created by the presence of boats, which in two marinas exceeded the effect range medium (ERM). Elevated sediment Cu was associated with differences in benthic assemblages, reduced species richness and enhanced dominance in America's Cup and Harbor Island West, whereas Harbor Island East did not appear to be affected. At sites without boats there were greater abundances of some amphipods such as the species Desdimelita sp., Harpinia sp., Aoroides sp., Corophium sp., Podocerus sp., bivalves such as Lyonsia californica, Musculista senhousia, Macoma sp., and polychaetes such as Diplocirrus sp. In contrast, at sites with boats, densities of Pseudopolydora paucibranchiata, Polydora nuchalis, Euchone limnicola, Exogone lourei, Tubificoides spp. were enhanced. The limited impact on Harbor Island East suggests not only lower Cu input rates and increased water flushing and mixing, but also the presence of adequate defense mechanisms that regulate availability and mitigate toxic impacts. At all three marinas, Cu in tissues of several macrobenthic species exhibited Cu bioaccumulation above levels found in the surrounding environment. The annelids Lumbrineris sp. and Tubificoides spp., and the amphipod Desdimelita sp. contained high levels of Cu, suggesting they function as Cu bioaccumulators. The spionid polychaetes Polydora nuchalis and Pseudopolydora paucibranchiata had much lower Cu concentrations than surrounding sediments, suggesting they function as Cu bioregulators. The macrobenthic invertebrates in San Diego Bay marinas that tolerate Cu pollution (e.g. P.nuchalis, P.paucibranchiata, Euchone limnicola, Typosyllis sp., Tubificoides sp.) may function as indicators of high-Cu conditions, whereas the presence of Cu-sensitive species (e.g. Podocerus sp., Aoroides sp., Harpinia sp., Macoma sp., Lyonsia californica) may indicate healthier conditions (less Cu-stressed). Parallel responses by faunas of Shelter Island Yacht Basin, also in San Diego Bay, suggest potential for development of regional Cu contamination assessment criteria, and call for functional comparisons with other marinas and coastal water bodies.

2012
Hunter, WR, Levin LA, Kitazato H, Witte U.  2012.  Macrobenthic assemblage structure and organismal stoichiometry control faunal processing of particulate organic carbon and nitrogen in oxygen minimum zone sediments. Biogeosciences. 9:993-1006.   10.5194/bg-9-993-2012   AbstractWebsite

The Arabian Sea oxygen minimum zone (OMZ) impinges on the western Indian continental margin between 150 and 1500 m, causing gradients in oxygen availability and sediment geochemistry at the sea floor. Oxygen availability and sediment geochemistry are important factors structuring macrofaunal assemblages in marine sediments. However, relationships between macrofaunal assemblage structure and sea-floor carbon and nitrogen cycling are poorly understood. We conducted in situ C-13:N-15 tracer experiments in the OMZ core (540 m [O-2] = 0.35 mu mol l(-1)) and lower OMZ boundary (800-1100 m, [O-2] = 2.2-15.0 mu mol l(-1)) to investigate how macrofaunal assemblage structure, affected by different oxygen levels, and C:N coupling influence the fate of particulate organic matter. No macrofauna were present in the OMZ core. Within the OMZ boundary, relatively high abundance and biomass resulted in the highest macrofaunal assimilation of particulate organic carbon (POC) and nitrogen (PON) at the lower oxygen 800 m stations ([O-2] = 2.2-2.36 mu mol l(-1)). At these stations the numerically dominant cirratulid polychaetes exhibited greatest POC and PON uptake. By contrast, at the higher oxygen 1100 m station ([O-2] = 15.0 mu mol l(-1)) macrofaunal C and N assimilation was lower, with POC assimilation dominated by one large solitary ascidian. Macrofaunal POC and PON assimilation were influenced by changes in oxygen availability, and significantly correlated to differences in macrofaunal assemblage structure between stations. However, macrofaunal feeding responses were ultimately characterised by preferential organic nitrogen assimilation, relative to their internal C:N budgets.

2009
Gooday, AJ, Levin LA, da Silva AA, Bett BJ, Cowie GL, Dissard D, Gage JD, Hughes DJ, Jeffreys R, Lamont PA, Larkin KE, Murty SJ, Schumacher S, Whitcraft C, Woulds C.  2009.  Faunal responses to oxygen gradients on the Pakistan margin: A comparison of foraminiferans, macrofauna and megafauna. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 56:488-502.   10.1016/j.dsr2.2008.10.003   AbstractWebsite

The Pakistan Margin is characterised by a strong mid-water oxygen minimum zone (OMZ) that intercepts the seabed at bathyal depths (150-1300 m). We investigated whether faunal abundance and diversity trends were similar among protists (foraminiferans and gromiids), metazoan macrofauna and megafauna along a transect (140-1850 m water depth) across the OMZ during the 2003 intermonsoon (March-May) and late/post-monsoon (August-October) seasons. All groups exhibited some drop in abundance in the OMZ core (250-500 m water depth; O(2): 0.10-0.13 mL L(-1) = 4.46-5.80 mu M) but to differing degrees. Densities of foraminiferans >63 mu m were slightly depressed at 300 m, peaked at 738 m, and were much lower at deeper stations. Foraminiferans >300 mu m were the overwhelmingly dominant macrofaunal organisms in the OMZ core. Macrofaunal metazoans reached maximum densities at 140 m depth, with additional peaks at 850, 940 and 1850 m where foraminiferans were less abundant. The polychaete Linopherus sp. was responsible for a macrofaunal biomass peak at 950 m. Apart from large swimming animals (fish and natant decapods), metazoan megafauna were absent between 300 and 900 m (O(2) <0.14-0.15 mLL(-1) = 6.25-6.69 mu M) but were represented by a huge, ophiuroid-dominated abundance peak at 1000 m (O(2) similar to 0.15-0.18 mLL(-1) = 6.69-8.03 mu M). Gromiid protists were confined largely to depths below 1150 m (O(2) > 0.2 mLL(-1) = 8.92 mu M). The progressively deeper abundance peaks for foraminiferans (> 63 mu m), Linopherus sp. and ophiuroids probably represent lower OMZ boundary edge effects and suggest a link between body size and tolerance of hypoxia. Macro- and megafaunal organisms collected between 800 and 1100 m were dominated by a succession of different taxa, indicating that the lower part of the OMZ is also a region of rapid faunal change. Species diversity was depressed in all groups in the OMZ core, but this was much more pronounced for macrofauna and megafauna than for foraminiferans. Oxygen levels strongly influenced the taxonomic composition of all faunal groups. Calcareous foraminiferans dominated the seasonally and permanently hypoxic sites (136-300 m); agglutinated foraminiferans were relatively more abundant at deeper stations where oxygen concentrations were >0.13 mLL(-1)( = 5.80 mu M). Polychaetes were the main macrofaunal taxon within the OMZ; calcareous macrofauna, and megafauna (molluscs and echinoderms) were rare or absent where oxygen levels were lowest. The rarity of larger animals between 300 and 700 m on the Pakistan Margin, compared with the abundant macrofauna in the OMZ core off Oman, is the most notable contrast between the two sides of the Arabian Sea. This difference probably reflects the slightly higher oxygen levels and better food quality on the western side. (C) 2008 Published by Elsevier Ltd.

2006
Levin, LA, Ziebis W, Mendoza GF, Growney-Cannon V, Walther S.  2006.  Recruitment response of methane-seep macrofauna to sulfide-rich sediments: An in situ experiment. Journal of Experimental Marine Biology and Ecology. 330:132-150.   10.1016/j.jembe.2005.12.022   AbstractWebsite

Hydrodynamically unbiased colonization trays were deployed for 6 months (Oct. 2000 to April 2001) on the northern California margin (Eel R. region; 525 m) to examine macrofaunal colonization rates at methane seeps. The influence of sulfide on recruitment and survival was examined by deploying sediments with and without sulfide added; effect of seep proximity was evaluated by placing trays inside and outside seeps. The trays contained a two-layer system mimicking vesicomyid clam bed habitat geochemistry, with 89 9 mM sulfide in a lower agar layer at the start of the experiment. After 6 month on the seabed, the lower agar layer contained 2-4 mM H2S. We observed rapid macrofaunal colonization equivalent to 50% of initial non-seep ambient densities. There was no difference in total colonizer densities, number of species, or rarefaction diversity among 3 treatments: (1) controls (no sulfide added) placed outside seeps, (2) trays with sulfide added placed outside seeps and (3) trays with sulfide added placed inside seep patches. Colonization trays with sulfide placed at seeps had different species composition from trays without sulfide place outside seeps; there were more amphipods (non-ampeliscid) and cumaceans in the seep/sulfide treatment and more nemerteans, Nephtys cornuta and tanaids in the non-seep/no-sulfide treatment. Outside seeps, annelids comprised <15% of tray colonists; within seep patches, annelids comprised 5 of the top 10 dominant colonizing taxa (24% of the total). The polychaetes Mediomastus sp., Aphelochaeta sp., Paraonidae sp., and Nerillidae sp. exhibited significantly higher densities in sulfide additions. Tanaids, echinoderms, and N. cornuta exhibited sulfide avoidance. At least 6 dorvilleid polychaete species colonized the experiments. Of these, 4 species occurred exclusively in trays with sulfide added and 80% of all dorvilleid individuals were found in trays with sulfide placed inside seep sediments. Counts of large sulfur bacterial filaments were positively correlated with maximum sulfide concentration in each tray, and with proximity of sulfide to the sediment surface. However, total macrofaunal densities were not correlated with tray sulfide concentrations. As a group, tray assemblages achieved some but not all characteristics of ambient seep assemblages after 6-month exposure on the sea floor. Distinctive colonization patterns at methane seeps contribute to the dynamic mosaic of habitat patches that characterize the eastern Pacific continental margin. Overall, proximity of seep habitats had at least as great an influence on macrofaunal colonization as tray sulfide concentrations. Taxa characteristic of seep sediments were more likely to settle into trays placed inside rather than outside seep patches. Whether this is due to limited dispersal ability or local geochemical cues remains to be determined. (C) 2005 Elsevier B.V. All rights reserved.

2004
Gallardo, VA, Palma M, Carrasco FD, Gutierrez D, Levin LA, Canete JI.  2004.  Macrobenthic zonation caused by the oxygen minimum zone on the shelf and slope off central Chile. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 51:2475-2490.   10.1016/j.dsr2.2004.07.028   AbstractWebsite

The relationship between macrobenthic (greater than or equal to 300 mum) zonation and the oxygen minimum zone (OMZ: O(2) < 0.5 ml L(-1)) was studied in shelf and slope sediments (122-840 m depth) off Concepcion Bay, central Chile. Four study sites were sampled during March-April 1999 for abiotic factors, macrofaunal density, biomass, mean individual size, and diversity. Within the OMZ (122-206 m), the macrofaunal density was high (16,478-21,381 individuals m(-2)) and 69-89% of the organisms were soft-bodied. Density was highest (21,381 individuals m(-2)), biomass lowest (16.95 g wet weight m-2), and individual size smallest (0.07 mg C individuals) at the shelf break site (206 m). Polychaete worms made up 71% of the total abundance, crustaceans 16%, and mollusks only 2%. Total abundance beneath the OMZ (mid-slope site, similar to840 m) was 49% crustaceans and 43% polychaetes. Although existing literature originally led to the hypothesis that both diversity and biomass within the OMZ would be lower than beneath the OMZ, in the present study this was only true for diversity. Biomass distribution, on the other hand, was concave along the depth gradient; the highest values were near the upper edge of (122 m) and beneath (840 m) the OMZ. Indices of the macrofaunal community structure varied in relation to bottom-water oxygen concentration, chlorophyll-alpha, phaeopigments, and sulfide concentration, but not in relation to grain size, C, N, mud, porosity, redox potential, a bottom-water temperature. (C) 2004 Published by Elsevier Ltd.

2001
Talley, TS, Crooks JA, Levin LA.  2001.  Habitat utilization and alteration by the invasive burrowing isopod, Sphaeroma quoyanum, in California salt marshes. Marine Biology. 138:561-573.   10.1007/s002270000472   AbstractWebsite

In recent years the pace of exotic species introduction and invasion has accelerated, particularly in estuaries and wetlands. Species invasions may affect coastal ecosystems in many ways. Alteration of sedimentary environments, through structure formation and burrowing, has particularly dramatic effects on coastal habitats. This study examines modification of channel bank and marsh edge habitat by the burrowing Australasian isopod Sphaeroma quoyanum Milne Edwards, in created and natural salt marshes of San Diego Bay and San Francisco Bay. Abundance and distribution patterns of this isopod species, its relationships with habitat characteristics, and its effects on sediment properties and bank erosion were examined seasonally, and in several marsh microhabitats. Mean isopod densities were 1541 and 2936 individuals per 0.25 m(2) in San Francisco Bay, and 361 and 1153 individuals per 0.25 m(2) in San Diego Bay study sites during December and July 1998, respectively. This isopod forms dense, anastomosing burrow networks. S. quoyanum densities did not differ as a function of location within creeks or location in natural versus created marshes. Burrows, which are on average 6 mm wide and 2 cm long, were associated with firm sediments containing high detrital biomass. Although erosion is a natural process along salt marsh banks, enclosure experiments demonstrated that isopod activities can enhance sediment loss from banks. In areas infested with S. quoyanum, losses may exceed 100 cm of marsh edge per year. The effects of habitat alteration by this invading species are likely to increase in severity in the coastal zone as these ecosystems become degraded.

Ewel, KC, Cressa C, Kneib RT, Lake PS, Levin LA, Palmer MA, Snelgrove P, Wall DH.  2001.  Managing critical transition zones. Ecosystems. 4:452-460.   10.1007/s10021-001-0106-0   AbstractWebsite

Ecosystems that function as critical transition zones (CTZs) among terrestrial, freshwater, and marine habitats are closely connected to the ecosystems adjacent to them and are characterized by a rapid flux of materials and organisms. CTZs play various roles, including mediating water flows, accumulating sediments and organic matter, processing nutrients, and providing opportunities for recreation. They are particularly difficult to manage because they tend to be small, albeit important, components of large watersheds, and managers may not have control over the entire landscape. Moreover, they are often the focus of intensive human activity. Consequently, CTZs are critically important zones, and their preservation and protection are likely to require unique collaboration among scientists, managers, and stakeholders. Scientists can learn a great deal from the study of these ecosystems, taking advantage of small size and the importance of fluxes, but a good understanding of adaptive management strategies is needed to establish a dialogue with managers and stakeholders on technical and management issues. An understanding of risk analysis is also important to help set meaningful goals and establish logical strategies that include all of the interested parties. Successful restoration of a CTZ is the best test of the quality of knowledge about its structure and function. Much has already been learned about coastal CTZs through restoration projects, and the large number of such projects involving riparian CTZs in particular suggests that there is considerable opportunity for fruitful collaborations between scientists and managers.

2000
Gage, JD, Levin LA, Wolff GA.  2000.  Benthic processes in the deep Arabian Sea: introduction and overview. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 47:1-7.   10.1016/S0967-0645(99)00095-8   AbstractWebsite
n/a
1998
Levin, LA, Gage JD.  1998.  Relationships between oxygen, organic matter and the diversity of bathyal macrofauna. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 45:129-163.   10.1016/s0967-0645(97)00085-4   AbstractWebsite

The relationships of environmental factors with measures of macrobenthic community diversity were examined for the total fauna, and for polychaetes only, from 40 bathyal stations in the North Atlantic, eastern Pacific and Indian Oceans (154-3400 m). Stepwise multiple regression revealed that depth, latitude, sediment organic-carbon content and bottom-water oxygen concentration are significant factors that together explained 52-87% of the variation in macrobenthic species richness (E[s(100)]), the Shannon-Wiener index (H'), dominance (D), and evenness (J'). Percent sand and percent clay were not significant factors. After removal of depth and latitudinal effects, oxygen and organic-carbon concentrations combined accounted for 47, 67, 52 and 32% of residual variation in macrobenthic E(s(100)), H', D, and J', respectively. Organic carbon exhibited a stronger relationship than oxygen to measures of community evenness, and appeared to have more explanatory power for polychaetes than total macrobenthos. When only stations with oxygen < 1mll(-1) were considered, oxygen concentration became the dominant parameter after depth. Results suggest existence of an oxygen threshold ( < 0.45 mi l(-1)), above which oxygen effects on macrobenthic diversity are minor relative to organic matter influence, but below which oxygen becomes a critical factor. Our regression results lead us to hypothesize that for bathyal faunas, oxygen at low concentrations has more influence on species richness, while organic carbon regulates the distribution of individuals among species (community evenness). Examination of rarefaction curves for Indo-Pacific stations reveals that total macrobenthos, polychaetes, crustaceans and molluscs all exhibit reduced species richness within oxygen minimum zones (OMZs). However, representation under conditions of hypoxia varies among taxa, with polychaetes being most tolerant. Molluscs and crustaceans often (but not always) exhibit few individuals and species in OMZs, and sometimes disappear altogether, contributing to reduced macrobenthic diversity and elevated dominance in these settings. The linear negative relationship observed between bathyal species richness and sediment organic-carbon content (used here as a proxy for food availability) may represent the right side (more productive half) of the hump-shaped, diversity-productivity curve reported in other systems. These analyses suggest then are potentially strong influences of organic matter and oxygen on the diversity and composition of bathyal macrobenthos, especially in the Indo-Pacific Ocean. (C) 1998 Elsevier Science Ltd. All rights reserved.

1996
Levin, LA, Talley D, Thayer G.  1996.  Succession of macrobenthos in a created salt marsh. Marine Ecology-Progress Series. 141:67-82.   10.3354/meps141067   AbstractWebsite

Early succession of macrofauna was examined over several years in a created Spartina alterniflora marsh located on the Newport River Estuary, North Carolina, USA. Epifauna and infaunal community structure and composition were compared at 2 elevations in plots planted with S. alterniflora, plots left bare of vegetation and vegetated plots in a nearby natural S, alterniflora marsh. No significant successional differences were observed between vegetated and unvegetated sediments in the created marsh. The earliest stages of colonization involved recruitment by opportunistic estuarine polychaetes: Streblospio benedicti, Capitella spp, and Polydora cornuta. Capitella spp. dominated the macrofauna a month after marsh creation, but thereafter S. benedicti was the most abundant species. During the first few years, the artificial marsh retained early successional characteristics, with S, benedicti, Capitella spp. and turbellarians accounting for 75 to 95% of the total macrofauna. Fiddler crabs were common epifaunal colonists. After 4 yr, species richness increased and dominance by the early colonists diminished. Taxa lacking planktonic larvae and swimming adults were particularly slow to recover in the created marsh, but accounted for over 25% of the infauna by Year 4. Oligochaetes, which comprised over 50% of the fauna in the natural marsh, remained absent or rare in the artificial system throughout the study. Infaunal recovery appears to be more rapid in lower than upper marsh elevations. Although macrofaunal densities and species richness of sediments in the lower created marsh came to resemble those of the natural marsh within 6 mo, species composition and faunal feeding modes did not. These observations suggest there may be significant functional differences between young artificial marshes and older natural marshes. Consideration of the timing of marsh creation, marsh configuration, continuity with natural marshes, seeding of taxa with poor dispersal, and attention to species habitat requirements are recommended to accelerate infaunal colonization of created Spartina marshes.

Levin, L, Caswell H, Bridges T, Dibacco C, Cabrera D, Plaia G.  1996.  Demographic responses of estuarine polychaetes to pollutants: Life table response experiments. Ecological Applications. 6:1295-1313.   10.2307/2269608   AbstractWebsite

Capitella sp. I and Streblospio benedicti are infaunal, deposit-feeding polychaetes that occur in estuaries and littoral wetlands throughout much of the United States. Life table response experiments (sensu Caswell 1989a) were carried out in the laboratory to compare the demographic responses of these species to three common sources of estuarine contamination or enrichment: sewage (Milorganite), blue-green algae (Spirulina sp,), and hydrocarbons (No. 2 fuel oil). Life table data were used to generate two population projection models (a fully age-classified model and a simple two-stage model) for each species in each treatment and in a salt marsh sediment control. These models were used to quantify the effects of treatments on survival, reproduction, and age at maturity, and hence on population growth rate. For both species, survival was high in all treatments except the blue-green algae treatment, where oxygen depletion (to <1 mL/L) occurred. Treatments had dramatic effects on age at maturity, fertility, and generation time, which differed between species and among contaminants. Population growth rates (lambda) were higher in Capitella sp. I than in S. benedicti for all treatments, primarily due to earlier maturation and a fertility advantage exhibited by Capitella during the first few weeks of reproduction, In Capitella sp. I, explosive increases in lambda were seen in the sewage (lambda = 5.31) and algae (lambda = 2.81) enrichments relative to the control (lambda = 1.86) and the hydrocarbon treatments (lambda = 1.67), Reduced maturation time and increases in age-specific fertility associated with rapid growth and large body size were responsible, Hydrocarbons reduced lambda primarily through delayed maturation and reduced age-specific fertility. population growth rates of S. benedicti in the hydrocarbon treatment (lambda = 1.11) and algae treatment (lambda = 1.09) were reduced relative to the control (lambda = 1.46) and sewage treatments (lambda = 1.41), The hydrocarbon reduction resulted from delayed maturity and reduced fertility, whereas the algal effects were caused by reductions in both juvenile survival and fertility. Our analyses revealed that Capitella sp. I's population growth rate was less sensitive than that of S. benedicti to these three common forms of estuarine contamination, that different sources of organic enrichment (sewage and blue-green algae) introduced at the same C and N levels could have varying demographic effects, and that when two contaminants (hydrocarbons and blue-green algae) caused similar reductions in population growth rate in a species (Streblospio), the underlying mechanisms may have differed. For both species all demographically important effects of contaminants occurred early in life, suggesting a need to focus on juveniles and young adults in held and laboratory testing. The experiments performed here demonstrated the sensitivity of polychaete demographic properties to the condition of estuarine sediments, This sensitivity may be exploited to evaluate organic enrichment and hydrocarbon contamination in field settings.

1991
Moy, LD, Levin LA.  1991.  Are Spartina marshes a replaceable resource? A functional approach to evaluation of marsh creation efforts Estuaries. 14:1-16.   10.2307/1351977   AbstractWebsite

Marsh creation has come into increasing use as a measure to mitigate loss of valuable wetlands. However, few programs have addressed the functional ecological equivalence of man-made marshes and their natural counterparts. This study addresses structural and functional interactions in a man-made and two natural marshes. This was done by integrating substrate characteristics and marsh utilization by organisms of two trophic levels. Sediment properties, infaunal community composition, and Fundulus heteroclitus marsh utilization were compared for a man-made Spartina salt marsh (between ages 1 to 3 yr) in Dills Creek, North Carolina, and adjacent natural marshes to the east and west. East natural marsh and planted marsh sediment grain-size distributions were more similar to each other than to the west natural marsh due to shared drainage systems, but sediment organic content of the planted marsh was much lower than in either natural marsh. This difference was reflected in macrofaunal composition. Natural marsh sediments were inhabited primarily by subsurface, deposit-feeding oligochaetes whereas planted marsh sediments were dominated by the tube-building, surface-deposit feeding polychaetes Streblospio benedicti and Manayunkia aestuarina. Infaunal differences were mirrored in Fundulus diets. Natural marsh diets contained more detritus and insects because oligochaetes, though abundant, were relatively inaccessible. Polychaetes and algae were major constituents of the planted marsh Fundulus diet. Though natural-marsh fish may acquire a potentially less nutritive, detritus-based diet relative to the higher animal protein diet of the planted marsh fish, Fundulus abundances were markedly lower in the planted marsh than in the natural marshes, indicating fewer fish were being supported. Lower Spartina stem densities in the planted marsh may have provided inadequate protection from predation or insufficient spawning sites for the fundulids. After three years, the planted marsh remained functionally distinct from the adjacent natural marshes. Mitigation success at Dills Creek could have been improved by increasing tidal flushing, thereby enhancing access to marine organisms and by mulching with Spartina wrack to increase sediment organic-matter content and porosity. Results from this study indicate that salt marshes should not be treated as a replaceable resource in the short term. The extreme spatial and temporal variability inherent to salt marshes make it virtually impossible to exactly replace a marsh by planting one on another site.

Levin, LA, McCann LD, Thomas CL.  1991.  The ecology of polychaetes on deep seamounts in the eastern Pacific Ocean. Ophelia. :467-476. AbstractWebsite

Polychaetes were collected by the submersible ALVIN on 18 deep (788-3,353 m) seamounts in the eastern Pacific Ocean at 10-degrees, 13-degrees, 20-degrees and 30-degrees N off western Mexico. Polychaetes comprised 57.7% of all macrofauna collected. Average density over all locations was 942 polychaetes/m2. Thirty-eight families were represented among the 1,422 infaunal polychaetes collected. Five families, the Paraonidae, Cirratulidae, Syllidae, Ampharetidae, and Sabellidae, attained average densities > 1 individual/196 cm2 core. We evaluated effects of latitude, local setting, depth, and substrate on polychaete abundance, taxonomic composition, and lifestyles. Unusually high polychaete densities (7,194/m2) and low diversities were observed in a shallow caldera (788 m) at 13-degrees N. Excluding this site, the latitude exhibiting the highest polychaete densities (xBAR = 939/m2) was 10-degrees N. Of the seven settings examined, pit craters (within seamount calderas) supported the highest densities (xBAR = 1031/m2), and hydrothermal oxide fields and seamount bases exhibited the lowest polychaete densities (xBAR = 576-612/m2). Rippled foraminiferal sands on volcano summits supported large numbers of filter feeders, particularly sabellids. Regressions of total polychaete abundance on depth and on percent sand were not significant. Large, epifaunal, sediment-agglutinating protozoans (Phylum Sarcodina: Class Xenophyophorea) provided habitat for 34 polychaete species. Polychaete abundance and family composition were generally similar to those reported for other nearshore, deep-sea environments at comparable depths. With the exception of the shallowest site, species richness was typically high.