Life after death: shallow‐water Mediterranean invertebrate communities associated with mammal bones

Invertebrate and microbial marine communities associated with mammal bones are interesting and poorly understood habitats, mainly known from studies on deep‐water whale remains. In order to characterize these communities in the shallow‐water Mediterranean, we present here the results of a pioneering experiment using mammal bones. Minke whale, pig and cow bones were experimentally deployed on three different background communities: rocky substrate, soft‐bottom and a Posidonia oceanica meadow. Bones were deployed for a year at about 20 m depth and collected every 3 months, and the invertebrate fauna colonizing the bones was identified to the lowest possible taxonomic level. As expected, mammal bones showed remarkable differences when compared with background communities. Within bones, four different clusters could be identified, primarily on the basis of the polychaete fauna, the most abundant and diverse group in the survey. Clusters A1–A3 corresponded to high to moderately altered successional stages composed by a fauna closer to that of anthropogenically enriched shallow‐water environments. These clusters were characterized by the occurrence of the opportunist polychaetes Ophryotrocha puerilis, Neanthes caudata (Cluster A1), Protodorvillea kefersteini (Cluster A2) and Ophryotrocha alborana (Cluster A3). Cluster B was characterized by the presence of the polychaete Oxydromus pallidus together with typical invertebrate background fauna, which suggests that this community, after a year of deployment, was closer to that found in natural conditions. As opposed to similar shallow‐water studies in other geographic areas, no occurrence of the polychaete Osedax (commonly known as bone‐eating worms) was reported from our experiments. Apart from the study on the invertebrate communities, insights about the population dynamics of three of the most abundant species (O. puerilis, O. alborana, N. caudata) are given as well as remarks on a hypothetical trophic network based on fecal pellet analysis.     

Improved in situ gamma-ray transmission densitometer for marine sediments

The first-generation University of Illinois gamma-ray transmission densitometer, designed for the in situ measurement of sediment bulk density, was modified by incorporating in the detector probe (1) an Americium-241 alpha particle pulser and an anti-walk gain stabilization control to maintain better temperature stability and (2) a small power supply and a IC preamplifier to eliminate the need for a high-voltage coaxial cable between the detector and external signal conditioning electronics package. This second-generation Lehigh University system has been successfully deployed since 1971 in routine use from ships and submersibles in the Atlantic and Pacific Oceans and the Gulf of Mexico. Results are presented of system operations to (1) measure bulk density over the range of 1.2–1.8 Mg/m³ in the Hudson Canyon, (2) penetrate 1.9 m into the seafloor in the San Diego trough and, (3) be lowered to a water depth of 3.6 km in the Gulf of Mexico.     

The impact of implanted whale carcass on nematode communities in shallow water area of Peter the Great Bay (East Sea)

In May, 2007 we sank the remains of a Minke whale (Balaenoptera acutorostrata) in the East Sea, Peter the Great Bay, at 30 m of water near the coast of Big Pelis Island. In the present study we describe the nematode communities in sediments under the implanted whale carcass. Abundance of nematodes increased with the distance from the carcass. Dominant trophic group was non-selective deposit feeders. The highest values of indexes of a specific diversity and evenness were noted in sediments under the whale, while domination index occurred at the highest distance from the whale. The suggestion is made that the cause of low density of nematodes in sediments under the whale is an extreme increase in number of macrofaunal animals, and predation and food competition between macro- and meiofauna. The changes noted in nematode assemblages living in an implanted whale in shallow waters are similar to those in deep-sea assemblages.     

Community structure of infaunal macrobenthos around vestimentiferan thickets at the San Clemente cold seep,NE Pacific

The San Clemente cold seep lies within 100–200 km of other reducing habitats in the NE Pacific, offering an opportunity to compare diversity and species overlap among reducing habitats (i.e. whale‐, kelp‐, and wood‐falls) at similar depths within a single region. Video observations from the research submersible Alvin at the San Clemente seep (1800 m depth) indicated clumps (‘thickets’) of vestimentiferans distributed as meter‐scale patches interspersed with vesicomyid clam beds and black sediments. Sediment‐core samples were collected at distances of 0 to 80–200 m along randomly oriented transects radiating outward from vestimentiferan thickets to evaluate changes in macrofaunal community structure from thickets into the background community. Macrofaunal abundance was elevated at distances of 0–1 m compared to 80–200 m (i.e. the ‘background’ community). The tube‐building frenulate worms Siboglinum spp., along with peracarid crustaceans, dominated sediments within 1 m of vestimentiferan thickets. Species diversity was depressed within 1 m of thickets but with high rates of species accumulation, suggesting that seep sites greatly increase sediment heterogeneity and facilitate colonization by non‐background macrofaunal species. Stable isotope data indicate chemosynthetic nutrition for some dominant macrofaunal species within 1 m of tubeworm thickets. The macrofaunal community near vestimentiferan thickets in San Clemente seep contains intermediate levels of species richness and diversity compared to other deep‐sea seep areas in the northeast Pacific. There was low species overlap between the San Clemente seep macrofauna and communities in reducing habitats near wood‐, whale‐, and kelp‐falls at similar depths within the region, suggesting that seeps harbor a distinct infaunal community.     

Discovery of a recent,natural whale fall on the continental slope off Anvers Island,western Antarctic Peninsula

Whale falls provide a substantial, nutrient-rich resource for species in areas of the ocean that may otherwise be largely devoid of food. We report the discovery of a natural whale fall at 1430 m depth in the cold waters of the continental slope off the western Antarctic Peninsula. This is the highest-latitude whale fall reported to date. The section of the carcass we observed—the tail fluke—was more complete than any previously reported natural whale fall from the deep sea and in the early stages of decomposition. We estimate the entire cetacean to measure 5–8 m in length. The flesh remained almost intact on the carcass but the skin was missing from the entire section except for the end of the fluke, clearly exposing blubber and soft tissue. The absence of skin indicates rapid and Homogeneous loss. The dominant macrofauna present were crustaceans, including most prominently the lithodid crab Paralomis birsteini, and zoarcid fish typical of the ‘mobile-scavenger’ successional stage. The density of mobile macrofauna was greatest on the carcass and declined to background levels within 100 m, indicating that they were attracted to the whale fall. This whale fall offers an important opportunity to examine the decomposition of a carcass under deep-sea conditions at polar latitudes.     

Deformation and patterns of sedimentation,South San Clemente Basin,California Borderland

Seismic reflection profiling in the South San Clemente Basin and the southern portion of the San Diego Trough has revealed at least six sedimentary units exhibiting varying stages of deformation. Four of the units are interpreted to be marine turbidites supplied by adjacent submarine canyons. Sediments comprising the Descanso Plain and correlative material within the South San Clemente Basin are attributed to a southerly source (Banda Canyon), while the more recent Quaternary turbidites from Coronado Canyon filled the southern San Diego Trough and then spilled over into South San Clemente Basin. The relatively high but intermittent rates of sedimentation, together with shifting sources and areas of deposition, have resulted in sedimentary units that were emplaced in comparatively short episodes but which were subjected to relatively continuous tectonic activity. Consequently, the sedimentary layers of each unit appear uniformly affected by deformation which increases in successively older units.     

Three-year investigations into sperm whale-fall ecosystems in Japan

We report the first study of sperm whale‐fall ecosystems, based on mass sinking of whale carcasses at shelf depths in the northwest Pacific. We conducted three observations over a 2‐year period on replicate sperm‐whale carcasses implanted at depths of 219–254 m off the southern part of Japan from July 2003 to August 2005. The study was made possible by a mass stranding of sperm whales in January 2002, and the subsequent sinking of 12 carcasses in the waters off Cape Nomamisaki. Dense aggregations of unique chemosynthesis‐based fauna had formed around the whale carcasses after 18 months (July 2003). The mytilid mussel Adipicola pacifica was the most abundant macrofaunal species and covered most of the exposed bone surfaces. The general composition of the fauna was similar to that of deep‐water reducing habitats, but none of the species appearing in this study has been found at hydrothermal vents, cold seeps or deep‐water whale falls. A new species of lancelet, which was the first record of the subphylum Cephalochordata from reducing environments, a new species of Osedax; a rarely encountered benthic ctenophore, and a rare gastropod species were discovered at this sperm whale‐fall site. Benthic communities were similar across all the carcasses studied, although the body sizes of the whales were very different. The succession of epifaunal communities was relatively rapid and the sulphophilic stage was considerably shorter than that of other known whale falls.     

The discovery of a natural whale fall in the Antarctic deep sea

Large cetacean carcasses at the deep-sea floor, known as ‘whale falls’, provide a resource for generalist-scavenging species, chemosynthetic fauna related to those from hydrothermal vents and cold seeps, and remarkable bone-specialist species such as Osedax worms. Here we report the serendipitous discovery of a late-stage natural whale fall at a depth of 1444 m in the South Sandwich Arc. This discovery represents the first natural whale fall to be encountered in the Southern Ocean, where cetaceans are abundant. The skeleton was situated within a seafloor caldera, in close proximity (<250 m) to active hydrothermal vents. We used a DNA barcoding approach to identify the skeleton as that of an Antarctic minke whale (Balaenoptera bonaerensis). The carcass was in an advanced state of decomposition, and its exposed bones were occupied by a diverse assemblage of fauna including nine undescribed species. These bone fauna included an undescribed species of Lepetodrilus limpet that was also present at the nearby hydrothermal vents, suggesting the use of whale-fall habitats as stepping stones between chemosynthetic ecosystems. Using Remotely Operated Vehicle (ROV) videography, we have quantified the composition and abundance of fauna on the whale bones, and tested a hypothesis that varying concentrations of lipids in the bones of whales may influence the microdistribution of sulfophilic whale-fall fauna. Our data supported the hypothesis that more lipid-rich bones support a greater abundance of sulfophilic bacterial mats, which are also correlated with the abundance of grazing limpets (Pyropelta sp.). The abundance of Osedax sp. on bones however, showed a negative correlation with the bacterial-mat percentage cover, and hence greatest abundance on bones predicted to have lowest lipid content.     

Miocene Blanca Fan,Northern Channel Islands,California: Small fans reflecting tectonism and volcanism

Blanca fan is a submarine fan composed of Miocene volcaniclastic strata. Parts of the fan system are exposed on Santa Cruz and Santa Rosa Islands, and possibly correlative strata crop out on San Miguel and Santa Catalina Islands. The Blanca fan and underlying breccia reflect regional transcurrent faulting in the California Continental Borderland and development of a system of rapidly subsiding basins and uplifted linear ridges during early and middle Miocene time. Erosion of uplifted crystalline basement rocks followed by the onset of silicic volcanism created linear sediment sources for the alluvial and submarine fans, respectively.     

Miocene Blanca Fan, Northern Channel Islands, California: Small fans reflecting tectonism and volcanism

Blanca fan is a submarine fan composed of Miocene volcaniclastic strata. Parts of the fan system are exposed on Santa Cruz and Santa Rosa Islands, and possibly correlative strata crop out on San Miguel and Santa Catalina Islands. The Blanca fan and underlying breccia reflect regional transcurrent faulting in the California Continental Borderland and development of a system of rapidly subsiding basins and uplifted linear ridges during early and middle Miocene time. Erosion of uplifted crystalline basement rocks followed by the onset of silicic volcanism created linear sediment sources for the alluvial and submarine fans, respectively. Margin setting represents fan and/or source area     

A comparison of intertidal species richness and composition between Central California and Oahu,Hawaii

The intertidal zone of tropical islands is particularly poorly known. In contrast, temperate locations such as California's Monterey Bay are fairly well studied. However, even in these locations, studies have tended to focus on a few species or locations. Here we present the results of the first broadscale surveys of invertebrate, fish and algal species richness from a tropical island, Oahu, Hawaii, and a temperate mainland coast, Central California. Data were gathered through surveys of 10 sites in the early 1970s and again in the mid‐1990s in San Mateo and Santa Cruz counties, California, and of nine sites in 2001–2005 on Oahu. Surveys were conducted in a similar manner allowing for a comparison between Oahu and Central California and, for California, a comparison between time periods 24 years apart. We report a previously undocumented richness of intertidal species in both locations: 516 for Oahu and 801 for Central California. Surprisingly, when differences in search efforts are controlled, overall (alpha) diversity appears to be similar between locations, although site level (beta) diversity is much higher in California. Species richness in California generally increased along a wave exposure gradient and distance from an urban area. Much higher numbers of both invasive and endemic species were found on Oahu. In California, more invertebrate species were found in the 1990s, likely due to an improvement in taxonomic resources since the 1970s, and species composition was different in the two surveys due to the high incidence of rare species. Although some southern species increased in number between the two time periods and some northern species decreased, we detected little evidence of change favoring southern or northern species. These results are in line with recent findings that water temperatures in the Monterey Bay have been in a cooling trend since the 1980s, in contrast to many locations elsewhere in the world.     

Geotechnical aspects of fine-grained mass flow deposits: California Continental Borderland

Seismic reflection profiling demonstrates the importance of mass movement in the north-central California Borderland. Bulk properties of surficial hemipelagic sediments in the Santa Barbara, Santa Cruz, and San Nicolas basins show that different types of mass-transported sediments have different properties, although their general sedimentologic characteristics are very similar. Slump deposits have moderate water contents (48% wet weight basis), high plasticity indices (46%), and moderate activities (1.6). For debris flows these values are low: 28%, 5%, and 0.3, respectively, and for other types (liquefied flow, mudflows, and turbidities) the values are high: 54 to 63%, 49 to 58%, and 1.2 to 1.5, respectively.     

San Diego trough geotechnical test area

Abstract

The San Diego Trough Geotechnical Test Area, located about 24 km southwest of San Diego in a water depth of about 1.2 km, lies near the base of the Coronado Escarpment directly north of the Coronado Fan. A new bathymetric map delineates a shallow basin in the soft, highly plastic, clayey silts flooring the Test Area. Measurements of shear strength by vane and static cone pene‐trometer, and bulk density by nuclear densitometer, were made in place from the submersible Deep Quest. Sixteen short (< 1.6 m) gravity cores were collected from ships.

The geotechnical properties show little areal variation and generally change uniformly with depth within the 55 km² Test Area. Silt is the predominant grain size, averaging about 62%. In‐place bulk density shows little change with increasing depth, values range from 1.23 to 1.26 Mg/m³; laboratory density values increase with depth, ranging from 1.30 to 1.52 Mg/m³ between the surface and a depth of about 1.1 m. The difference between the in place and laboratory values may indicate sampling densification of the cored sediment. Water content in the cores decreases uniformly within the range of 249 to 43% dry weight. Shear strength increases linearly with depth. The laboratory shear strength values are lower than the in place values, which range from 4 kPa at the surface to about 29 kPa at a depth of 3.27 m. Predictor equations relate Atterberg limits, bulk density, water content, and laboratory and in place shear strength to depth. Sedimentation‐compression e log p curves have an equivalent compression index of 1.5 to nearly 2. Excluding rurbidite layers and sampling disturbance effects, all cores indicate a uniform depositional environment in the surface to 1.6 m of sediment sampled. The geotechnical properties indicate that the sediments in the west central and southwest parts of the Test Area exhibit vertical heterogeneity due to thin silt‐sand layers, presumably of turbidity current origin, that originated from the Coronado Canyon.     

Toxicological effects of potash brine on bay of Fundy marine organisms

The acute lethality and sublethal heavy metal contamination potential to marine organisms of a waste brine solution from a potash mining operation were determined. The brine was acutely lethal to marine organisms of the Bay of Fundy, Canada, at concentrations between 47 and 55‰ salinity (96-h LC₅₀ values: threespine stickleback, Gasterosteus aculeatus, 47·7‰; polychaete worm, Nephtys incisa, 52·5‰; blue mussel, Mytilus edulis, lethal to whole animal and reduced ciliary activity of gills above 55‰).The brine diluted to sublethal concentrations (≤40‰) contained manganese (≤ 49·5 ×), copper and zinc (≤ 5·2 ×), lead (≤ 2·6 ×) and cadmium (≤ 0·7 ×) in decreasing order of enrichment relative to control seawater. Copper was accumulated in mussels exposed to these solutions over 44 days to the greatest degree (4 ·4 ×), followed by manganese and lead. Tissue lead concentration reached a steady value within 44 days and cadmium was not accumulated.     

Assessing site-specific effects of TBT contamination with mussel growth rates

During nine field transplant tests in San Diego Bay (1987–1990), juvenile mussels were exposed to mean concentrations of tributyltin (TBT) in ambient seawater ranging from 2 to 530 ng liter⁻¹ for 12 weeks under natural conditions. A total of 79 cages with 18 mussels each were monitored at 18 different sites. Growth and seawater TBT concentrations were measured weekly or on alternate weeks (biweekly). Mean growth rates ranged from 17 to 505 mg week⁻¹ (0·2 to 2·5 mm week⁻¹). Accumulation of TBT in mussel tissues was measured at the end of each 12-week test exposure and ranged from 0·1 to 3·2 μg g⁻¹ TBT wet weight. The frequency of the measurements and the integration of chemical and biological measurements improved the accuracy of the assessment over more traditional approaches. Growth was significantly related to seawater and tissue TBT. The statistical relationships with growth effects were used to estimate chemical effect zones for TBT in San Diego Bay. Site-specific differences were distinguished by additional statistical analyses and consideration of environmental significance.     

Lipid biomarkers of deep-sea hydrothermal vent polychaetes—Alvinella pompejana, A. caudata, Paralvinella grasslei and Hesiolyra bergii

The lipid composition was determined for 5 species of polychaete annelids collected by the Deep Submergence Vehicle ALVIN from high temperature chimneys at the 2500 m depth hydrothermal vent field of the East Pacific Rise. These are the first lipid biomarker analyses reported for these hydrothermal vent polychaetes. Lipid content was low in all samples (1.6–35.9 mg g^–1 wet mass) and was dominated by polar lipid (78–90% of total lipid) with 8–19% sterol (ST), and very low storage lipid (triacylglycerol and wax ester). Total polyunsaturated fatty acids (PUFA) were moderately high (22–31% of total fatty acids (FA)) with extremely low or no docosahexaenoic acid (DHA, 22:6(n-3)). Eicosapentaenoic acid (EPA, 20:5(n-3)) levels were 5–6% in Alvinella pompejana and A. caudata and 10.3–13.7% in an errantiate polychaete (likely Hesionidae) and Hesiolyra bergii. There were greater PUFA and a greater EPA/AA (AA is arachidonic acid, 20:4(n-6)) ratio in the anterior versus the posterior half of A. pompejana, which may correlate to the strong temperature gradient reported in its tube. Total nonmethylene interrupted diunsaturated fatty acids (NMID) were 4–9% of total FA for most polychaete species and included several 20:2 and 22:2 components. The principal monounsaturated fatty acids (MUFA) included 18:1(n-7)c (14–19%), 16:1(n-7)c (2.6–10%) and 20:1(n-11)c (3–7% of total FA). These polychaete species may desaturate and elongate the bacterial-derived 18:1(n-7)c to obtain the essential FA EPA and AA. The major ST in the polychaetes is cholesterol (89–98% of total ST) with less cholesterol in the gut contents of A. pompejana. Other ST included 24-ethylcholesterol (1.5–5% of total ST) with lesser amounts of 24-methylenecholesterol, desmosterol, lathosterol, 24-methylcholesterol, 24-ethylcholesterol, and the stanols dehydrocholestanol and cholestanol. The high ST levels could play a role in thermal adaptation of membranes at the hydrothermal vent environment. Differences in the FA profiles separated the closely related species A. pompejana and A. caudata from Paralvinella grasslei, H. bergii, and the errantiate polychaete (likely Hesionidae).     

Autocovariance function and power spectrum of the vertical temperature gradient in the thermocline

The nature of the autocovariance function and power spectrum of time series of spike-array type is discussed. As the spacing of spikes is not easily seen directly in power spectrum, prudence should be exercised in interpreting the gradient spectrum of oceanic fine-structure. We calculated the autocovariance function and lag joint probability density of the record of the vertical profile of the vertical temperature gradient measured in the San Diego Trough. The results obtained support the results of the bispectral analysis in the previous paper (Nagata, 1978) that the predominant length scale of about 5 m has two meanings: spacing of the spikes and wavelength of a sinusoidal wave. The results seem to show the existence of nernal waves having a vertical wavelength the same as the spacing of the spikes or the thickness of the homogeneous layer in the oceanic fine-structure.     

A laboratory and field comparison of sediment polycyclic aromatic hydrocarbon bioaccumulation by the cosmopolitan estuarine polychaete Streblospio benedicti (Webster)

Polycyclic aromatic hydrocarbon (PAH) bioaccumulation by the polychaete worm Streblospio benedicti (Webster) was measured under exposure to PAH-contaminated sediments in the field and for 28 d in the laboratory. Streblospio benedicti collected from field sediments contaminated at 2.94, 1.07, and l.52 μg g⁻¹ fluoranthene (FLU), benz[a]anthracene (BAA), and benzo[a]pyrene (BAP), bioaccumulated those PAHs at 1.53, 0.215, and 0.332 μg g⁻¹, while worms isolated from less contaminated field sediments (0.399, 0.228, 0.288 μg g⁻¹ FLU, BAA, and BAP) had FLU, BAA, and BAP body burdens of 0.543, 0.236, and 0.083 μg g⁻¹. Worms incubated for 28 d in PAH-spiked sediments (1.52, 0.991, 0.504 μg g⁻¹ FLU, BAA, and BAP) bioaccumulated those PAHs at 0.382, 0.966, and 0.602 μg g⁻¹, respectively. Data normalization to organism lipid and sediment organic carbon (biota-sediment accumulation factors [BSAFs] strongly suggest that Streblospio PAH bioaccumulation was directly related to percent sediment organic carbon, but BSAFs were substantially lower than predicted by equilibrium partitioning theory. BSAFs decreased with increasing PAH log K_ow, in worms collected from field sediments, but in spiked sediments BSAFs increased with increasing PAH hydrophobicity. This disparity may have been caused by insufficient spiked-sediment equilibration time (1.5h) in the case of the laboratory test sediments.     

Bispectra of spike-array type time series and their application to the analysis of oceanic microstructures

Bispectral analysis is applied to records of the vertical profile of the vertical temperature gradient in the oceanic thermocline in the San Diego Trough. The bispectra exhibit three notable features; (1) bispectral peaks at the points (0.2 m^–1, 0.2 m^–1) and (0.2 m^–1, 0.1 m^–1), (2) bispectral ridges along the lines ( ₁= ₀, ₂= ₀ and ₁+ ₂= ₀ corresponding to peak wavenumbers ₀ in power spectra, and (3) array of bispectral peaks of interval of 0.2 m^–1 The results are compared with the bispectra of several modeled time series of spike-array type. The periodicity of 5 m found in the records seems to have two meanings: spacing of predominant spikes and wavelength of predominant sinusoidal wave. If this indicates the existence of internal waves having a vertical wavelength the same as the scale of homogeneous layers, it would suggest the possible importance of internal waves in the formation and maintenance mechanisms of oceanic microstructure.