Wood-fall Communities Research Articles

Sunken trees in the deep sea link terrestrial and marine biodiversity.

Wood in the deep sea serves as a substantial food source in an otherwise barren environment, forming specialized, endemic, and diverse community assemblages. This biodiversity reliance on a terrestrial source creates a linkage by which anthropogenic impacts on land can alter the deep oceans. Knowledge of the alpha- or beta-diversity of entire wood-fall communities, and wooden drivers of each would elucidate the terrestrial and deep-sea linkage. We report on a multifactorial experiment in the deep ocean in which alpha- and beta-diversity of 43 wood falls and 11 tree species are quantified over time, wood density, and wood size. We tested multiple hypotheses seeking to link how biodiversity on land may impact the biodiversity in the deep oceans. A tremendous biodiversity occurred among these wood falls in the deep Gulf of Mexico; 114 invertebrate species from 10 phyla. Time, wood hardness, and wood size all impacted various components of community structure. In many cases, these effects were additive. Species occurring on softwoods versus hardwoods and small versus large wood falls were compositionally different. Although various processes can control community structure, this experiment suggests a strong influence of environmental filtering and host specificity of wood-fall invertebrates suggesting an intimate coupling to tree biodiversity and biomass on land.

Stable Isotopic Evidence of Mixotrophy in Xylophagaids, Deep-Sea Wood-Boring Bivalves

Deep-sea wood-boring xylophagaid bivalves are thought to ingest only wood and to use nitrogen fixed by their symbiotic microbes. Reconsidering this assumption, we tested whether d13C and d15N isotopic values of ten species in four xylophagaid genera collected between 18 m and 4626 m depth suggest that some may use different trophic strategies. Isotopic signatures of six species were entirely consistent with predicted xylophagy, but four species, three members of the Xylophaga dorsalis clade and Abditoconus heterosiphon, had d15N signatures over 3.7‰, significantly higher than the value predicted for nitrogen fixed by bacteria. These species may supplement freshly fixed nitrogen with an alternate source, such as particulate organic material. Although the animals’ reduced palps and the lack of microbes in the gut of laboratory-maintained specimens were cited as arguing against filter feeding, the animals may filter feed opportunistically. Abditoconus heterosiphon was unique in having d13C signatures more negative than the wood into which they bored, inconsistent with cellulose consumption, and d15N values higher than predicted for nitrogen fixed by bacteria. We suggest that greater trophic diversity may exist among xylophagaids than has been expected. Ecological studies of wood-fall communities cannot assume that the entire community is sustained only by wood-bound energy. We attribute variation in d13C signatures among 42 specimens of X. s.l. zierenbergi from six collections, five at the same depth, to variation in the type of wood bored. Investigators beginning food web studies should sample xylophagaids and wood itself; if the deployment is large, repeated samples of the wood, closely matched to xylophagaids, may be necessarily to fully define the substrate’s stable isotopic signal.

Energetic increases lead to niche packing in deep-sea wood falls.

Mechanisms leading to variation in diversity over energetic gradients continue to challenge ecologists. Changes in diversity may reflect the environmental capacity to support species' coexistence through increased niche packing or niche space expansion. Current ecological theory predicts that increases in energy may lead to both scenarios but not their relative strengths. We use experimental deep-sea, wood-fall communities, where energy supply can be controlled, to test for the importance of niche expansion and packing in functional space over an energetic gradient. Invertebrate communities were identified and counted from 16 Acacia sp. logs ranging in size from 0.6 to 20.6 kg in mass (corresponding to energy availability) deployed at 3203 m in the Pacific Ocean for 5 years. We use four fundamental energetic species-level functional traits-food source, trophic category, motility and tiering-to characterize species niches. Increases in energy on wood falls lead to increases in species richness. This higher species richness resulted from a substantial increase in mean niche overlap, suggesting that increases in energy may afford reduced competition.

New and Mesozoic-relict mollusks from Paleocene wood-fall communities in Urahoro Town, eastern Hokkaido, northern Japan

AbstractFive species of bivalves and two species of gastropods are described from late Selandian to earliest Thanetian wood-fall communities from the Katsuhira Formation in Urahoro Town, eastern Hokkaido, northern Japan. Three bivalves and two gastropods are new to science:Thyasira(Thyasira)oliveriAmano and Jenkins, new species,Astarte(Astarte)paleocenicaAmano and Jenkins, new species,Poromya katsuhiraensisAmano and Jenkins, new species,Neverita majimaiAmano and Jenkins, new species, andBiplica paleocenicaAmano and Jenkins, new species.Poromya katsuhiraensisn. sp. andNeverita majimain. sp. are the earliest records of their genus.Astarte paleocenican. sp. is the last species before the genus disappeared from the northern Pacific region during the Eocene, only to reappear with the opening of the Bering Strait during the latest Miocene. Moreover, two bivalve species and one gastropod genus are Cretaceous relict forms:Propeamussium yubarense(Yabe and Nagao, 1928),Myrtea ezoensis(Nagao, 1938), andBiplicaPopenoe, 1957. These species and other relict protobranch bivalves had wide geographical ranges in the deep sea during the Cretaceous, which helped them to survive the end-Cretaceous mass extinction. The chemosynthesis-based speciesBathyacmaea? sp.,Myrtea ezoensis, andThyasira oliverin. sp. were recovered, but small bathymodioline mussels have not been found. This confirms that the small deep-sea mussels did not appear in the wood-fall communities at least by the earliest Thanetian.UUID:http://zoobank.org/125bd4ab-b172-43d9-80b9-57b75a805150

Increased energy differentially increases richness and abundance of optimal body sizes in deep-sea wood falls.

Theoretical and empirical studies suggest that the total energy available in natural communities influences body size as well as patterns of abundance and diversity. But the precise mechanisms underlying these relationships or how these three ecological properties relate remain elusive. We identify five hypotheses relating energy availability, body size distributions, abundance, and species richness within communities, and we use experimental deep-sea wood fall communities to test their predicted effects both on descriptors describing the species-richness-body-size distribution, and on trends in species richness within size classes over an energy gradient (size-class-richness relationships). Invertebrate communities were taxonomically identified, weighed, and counted from 32 Acacia sp. logs ranging in size from 0.6 to 20.6kg (corresponding to different levels of energy available), which were deployed at 3,203m in the Northeast Pacific Ocean for 5 and 7yr. Trends in both the species-richness-body-size distribution and the size-class-richness distribution with increasing wood fall size provide support for the Increased Packing hypothesis: species richness increases with increasing wood fall size but only in the modal size class. Furthermore, species richness of body size classes reflected the abundance of individuals in that size class. Thus, increases in richness in the modal size class with increasing energy were concordant with increases in abundance within that size class. The results suggest that increases in species richness occurring as energy availability increases may be isolated to specific niches, e.g., the body size classes, especially in communities developing on discrete and energetically isolated resources such as deep sea wood falls.

Abundance–occupancy relationships in deep sea wood fall communities

The generally positive relationship between the number of sites a species occupies and its average abundance within those sites provides an important link between population processes occurring at different spatial scales. Although such abundance–occupancy relationships (AORs) have been documented across a very wide range of taxa and in many different environments, little is known of such patterns in Earth's largest ecosystem, the deep sea. Wood falls – derived from natural or anthropogenic inputs of wood into the oceans – constitute an important deep‐sea habitat, habouring their own unique communities ultimately entirely dependent on the wood for chemical energy. In this study we take advantage of the unique features of an experimental wood fall deployment to examine AORs for the first time in deep‐sea invertebrates. The study design combines advantages of both experimental (tractability, control of key environmental parameters) and observational (natural colonisation by taxonomically diverse communities) studies. We show that the interspecific AOR is strongly positive across the 48 species occurring over 32 wood fall communities. The precise form of the AOR is mediated by both species‐level life history (body size) and by the colonisation stage at which communities were harvested, but not by environmental energy (wood fall size). Temporal dynamics within species are also generally consistent with positive intraspecific AORs. This support for positive AORs in the deep sea is an important extension of a macroecological generality into a new environment offering considerable potential for further testing and developing mechanistic macroecological theories.

Macroinvertebrate community assembly on deep-sea wood falls in Monterey Bay is strongly influenced by wood type.

Environmental filtering, including the influence of environmental constraints and biological interactions on species' survival, is known to significantly affect patterns of community assembly in terrestrial ecosystems. However, its role in regulating patterns and processes of community assembly in deep-sea environments is poorly studied. Here we investigated the role of wood characteristics in the assembly of deep-sea wood fall communities. Ten different wood species (substrata) that varied in structural complexity were sunk to a depth of 3,100m near Monterey Bay, CA. In total, 28 wood parcels were deployed on the deep-sea bed. After 2yr, the wood parcels were recovered with over 7,000 attached or colonizing macroinvertebrates. All macroinvertebrates were identified to the lowest taxonomic level possible, and included several undescribed species. Diversity indices and multivariate analyses of variance detected significant variation in the colonizing community assemblages among different wood substrata. Structural complexity seemed to be the primary factor altering community composition between wood substrata. For example, wood-boring clams were most abundant on solid logs, while small arthropods and limpets were more abundant on bundles of branches that provided more surface area and small, protected spaces to occupy. Other factors such as chemical defenses, the presence of bark, and wood hardness likely also played a role. Our finding that characteristics of woody debris entering the marine realm can have significant effects on community assembly supports the notion of ecological and perhaps evolutionarily significant links between land and sea.

Xylotrophic bivalves: aspects of their biology and the impacts of humans

Bivalves of the families Teredinidae and Xylophagaidae bore into and eat wood in shallow water and the deep sea, respectively. After an introduction to these sister taxa, I consider how they bore, focussing on the evolution of the cephalic hood in teredinids, which could contribute to the depth separation between the families. If the hood serves as a counter pressure to the foot, it may be vital in allowing teredinids to bore wood that contains air. The availability of wood has been suggested to determine the distribution of these animals. Mangrove habitats with abundant wood sustain the highest diversity, about one-third of all known teredinids. The open ocean, where wood is all but nonexistent, presents a nearly impassable barrier to most wood borers. Only after wooden sailing ships transported teredinids between ports did introduced species become problematic. Despite the rarity of wood in the open ocean, some xylophagaids live there as, it is hypothesized, do a limited number of teredinids; wood in the open ocean is predicted to be large because large size enhances buoyancy. The life history of open-ocean species may differ fundamentally from that of nearshore species. Physical stressors of temperature, salinity and desiccation appear to affect teredinids minimally; xylophagaids on the seafloor do not experience these variables. How biotic interactions such as competition and predation affect wood borers is yet to be thoroughly studied, but their impact may be greater than has been recognized, especially among teredinids. Although humans regard teredinids as pests that destroy wooden structures, and attempt to eradicate them from some areas, these animals play vital ecological roles. Teredinids make the energy and nutrients locked into wood available to the local community. Xylophagaids are nearly unique in breaking down cellulose and are analogous to primary producers in sustaining the diverse deep-sea wood-fall communities. The survival of borers requires wood to be present. The reduction of trees near water courses, removal of driftwood from navigable rivers and the destruction and fragmentation of the world’s mangrove habitats all threaten the predictable supply of wood in the sea and may seriously threaten the survival of these molluscs.

A new Miocene deep-sea chiton and early evidence for Teredinidae-sustained wood-fall communities

A new Miocene deep-sea chiton and early evidence for Teredinidae-sustained wood-fall communities

Beta-diversity on deep-sea wood falls reflects gradients in energy availability

Wood falls on the deep-sea floor represent a significant source of energy into the food-limited deep sea. Unique communities of primarily wood- and sulfide-obligate species form on these wood falls. However, little is known regarding patterns and drivers of variation in the composition of wood fall communities through space and time, and thus, how wood falls contribute to deep-sea biodiversity. Eighteen Acacia logs varying in size were placed and retrieved after five years at a 3200 m site in the Pacific Ocean. We found that the taxonomic composition and structure of deep-sea wood fall communities varied considerably and equated with considerable differences in energy usage and availability. Our findings suggest that natural variability in wood falls may contribute significantly to deep-sea diversity.

Non-actualistic wood-fall associations from Middle Jurassic of Poland

Kaim, A. 2010: Non-actualistic wood-fall associations from Middle Jurassic of Poland. Lethaia, Vol. 44, pp. 109–124. The oldest modern-type wood-fall (sunken wood) associations so far known, were reported from the Upper Cretaceous of Japan. Here, four Middle Jurassic fossil associations collected from logs of sunken driftwood are documented from clay and silt sediments of the Czestochowa Ore-bearing Clay Formation in Poland. The associations are composed of almost entirely different set of molluscs when compared to modern examples of wood-fall communities. The exceptions are leptochitonid polyplacophorans and alleged cocculinoid gastropods, both of which are typical of modern sunken wood communities. It is hypothesized here that the associations represent Jurassic wood-fall communities, which in contrast to their modern counterparts do not contain associated chemosymbiotic animals. This disparity results from the absence of xylophagain wood-boring bivalves, which since the Cretaceous have produced significant amounts of faecal pellets, the decomposition of which increases the amount of sulphide around sunken driftwoods. The associations are considered as benthic rather than pseudoplanktonic because the wood logs were colonized only on their upper side, the abundant crinoids belong to benthic genera rather than to pseudoplanktonic, associations include numerous infaunal organisms, and there are too many clingers in the associations. The most typical and numerous members of the investigated associations are the gastropods Cosmocerithium and Astandes, both having uncertain taxonomic positions. It is suggested here that Cosmocerithium could be a grazer of bacterial mats, and represents an ecological counterpart of modern Provannidae. □chitons, cocculinoids, deep sea, ecology, evolution, Wood-fall communities.

Fossil evidence for micro- and macrofaunal utilization of large nekton-falls: Examples from early Cenozoic deep-water sediments in Washington State, USA

Whale and fish carcasses and wood in the deep-sea host diverse and specialized faunas related to the hydrothermal vent and hydrocarbon seep biota. Fossil examples of such food-falls were found in the Eocene to Oligocene Crescent, Humptulips, Lincoln Creek, and Pysht formations in western Washington State, USA. They are used to document paleoecologic and taphonomic features of such sites. Paleontological evidence for ecologic processes occurring at ancient whale falls include: shark teeth indicating the presence of scavengers; bored bone surfaces showing microbial bone degradation; and bivalves belonging to chemosymbiotic groups. The latter indicator shows that sulfide was released from the anaerobic decay of carrion and/or bone lipids. It appears that the type of taxa and the low number of specimens mark a ‘chemotrophic opportunist stage’ that lasted only a few years. Furthermore, detritus in the marrow spaces of cancellous bones indicate that the bones were hollow for a significant length of time before burial, perhaps 1000 years or more. These spaces are now mostly filled with clotted micrite and other cement phases, the δ 13C values of which are in the same range as those of the concretionary matrix enclosing the bones, indicating cement formation within the sediments. A piece of wood from the Pysht Formation shows evidence for two generations of wood-boring bivalves, such that some boreholes have calcitic linings characteristic for teredinids, and some are lined with a crust of decomposed wood characteristic for xylophagains. Several investigated fossil wood-falls show that wood-boring bivalves were active on the seafloor: fecal pellets composed of woody detritus are abundant in the concretionary matrix surrounding the wood. The excellent preservation of these fecal pellets indicates that these concretions with wood and associated mollusks represent undisturbed, in situ wood-fall communities. In sum, undisturbed deep-water sediments can preserve evidence of life and ecologic processes at short-lived nekton-falls. However, the data also indicate a long time interval between the macrofaunal utilization of the substrates, and the cementation and fossilization of these associations. Thus using mineral deposits such as clotted micrite and pyrite as evidence for microbial activity during the macrofaunal utilization of the substrates is doubtful.

Wood‐fall associations from Late Cretaceous deep‐water sediments of Hokkaido, Japan

Kiel, S., Amano, K., Hikida, Y. & Jenkins, R.G. 2008: Wood-fall associations from Late Cretaceous deep-water sediments of Hokkaido, Japan. Lethaia, Vol. 42, pp. 74-82. Sunken wood (wood-fall) in the deep sea today is colonized and consumed by diverse invertebrate communities that show phylogenetic relationships to the chemotrophic fauna on whale carcasses, hydrothermal vents and hydrocarbon seeps. Here we document Late Cretaceous examples of wood-fall communities from deep-water sediments of the Yezo Group on Hokkaido, Japan, consisting of provannid, skeneiform, and patelliform gastropods, and thyasirid and nuculanid bivalves. These species are similar or identical to those found on plesiosaur bones and at hydrocarbon seeps in the same sediments, showing that many members of the modern chemotrophic deep-sea fauna colonized this range of habitats at least since Late Cretaceous time. We also document for the first time faecal chimneys in boreholes in these wood fragments, which were presumably built by xylophagain bivalves.