Infaunal Community Research Articles

SPI-ing on the seafloor: characterising benthic systems with traditional and in situ observations

This work aimed to show that the sea bed of two environmentally-different regions of the North Sea varies both spatially and temporally with respect to their biological communities and bioturbation characteristics. The two contrasting sites studied were north of the Dogger Bank (ND) (85 m) and the Oyster Grounds (OG) (45 m). The physical environment varied between and within sites, mainly influenced by sediment chlorophyll a content and water temperature. Our data revealed that the depth of the apparent Redox Potential Discontinuity (aRPD) layer at OG varied between 2.2 cm in February and 6.5 cm in October; evidence of bioturbation activity (e.g., feeding voids) was observed within the sediment profile. In contrast, at the ND site the aRPD values ranged from 1.7 cm in February to 2.5 cm in May and feeding voids and infaunal burrows were restricted to sediment depths far shallower than those observed at OG. Communities at ND were dominated by a number of surficial-sediment dwelling polychaete species (e.g., Notomastus latericeus, capitellids) while those of OG were dominated by the brittlestar Amphiurafiliformis, together with significant numbers of deeper-dwelling taxa such as the ghost shrimp Callianassa subterranea and the bivalve mollusc Corbula gibba. Our data imply that regions of the North Sea which experience dissimilar environmental conditions not only possess different infaunal communities but also contrasting seasonal fluctuations and bioturbation capacities. The ecological implications of these findings, including inferences for carbon and nutrient cycling, are discussed in relation to the wider North Sea ecosystem.

Infaunal biodiversity and ecological function on a remote oceanic island: The role of biogeography and bio-physical surrogates

Understanding and predicting the processes determining biological assemblages and marine biodiversity is critical to managing and conserving marine ecosystems. Infauna are a substantial component of shelf biodiversity and important contributors to ecological function. To examine the bio-physical relationships structuring infaunal assemblages across the Lord Howe Island (LHI) shelf, we mapped broad-scale physical and habitat-related features of the seabed using high-resolution multibeam sonar and sampled sediments and infauna across the shelf using a Smith-McIntyre grab. Broad-scale biogeographic processes were important determiners of the infaunal shelf assemblage. Shelf sediments supported an impoverished infaunal assemblage, with a high proportion of rare species, and many new and endemic species. This, combined with the numerical dominance of brooding endemics relative to lower densities of mainland taxa suggests that much of the islands infaunal diversity reflects transient dispersers rather than self-recruiting island populations. Local-scale physical processes, such as disturbance and current-borne nutrients, were also important in structuring the infaunal assemblage. Three geomorphic zones (drowned lagoon, relict reef and outer shelf) were strong predictors (or surrogates) of infaunal community and trophic structure over broad-scales (the extent of the shelf), while sediment composition (e.g. sorting and mean grain size) and seafloor structure (e.g. topography) were important predictors of population abundances and finer-scale (within-zone) community patchiness. Species richness and abundance were highest offshore on the outer shelf. Here, topographically raised sites subjected to oceanic currents supported high densities of suspension feeders and the highest levels of infaunal diversity. In contrast, the dynamic rippled sediments of the drowned lagoon supported an impoverished assemblage with a reduced trophic structure indicative of harsh physical environments. While biogeographic isolation in part explains low localised densities of non-endemic species, overall numbers per species indicate that many individuals are successfully arriving at LHI, but that sediment conditions – particularly in the drowned lagoon and to a lesser extent across the relict reef – may be too dynamic to provide suitable habitat for many of these species. These results suggest that interactions between shelf topography, physical wave disturbance and nutrient supply from oceanic currents are important factors structuring oceanic shelf assemblages. This study highlights that seabed habitat mapping when explicitly integrated with fine-scale bio-physical surveys can provide substantial insight into the spatial distribution and ecological function of benthic assemblages, and provides an essential ecological and spatial framework to predict the future structure of these populations and assemblages in response to natural and anthropogenic change.

Effects of tidal inundation on benthic macrofauna associated with the eelgrass Zostera muelleri

Processes, such as sea level rise, that alter tidal inundation regimes have the potential to modify the structure of seagrasses and their dense and diverse faunal communities. This study tested the hypothesis that seagrass-dwelling invertebrate communities would vary across a tidal inundation gradient as a result of direct effects of tidal inundation and indirect effects, arising from changes in seagrass morphology across this gradient. First, we conducted mensurative sampling across tidal inundation gradients to assess how above- and below-ground seagrass biomass, and epi- and infaunal invertebrate communities co-varied with depth. Second, we ran a manipulative field experiment, utilising artificial seagrass rhizomes of varying morphologies, to separate out direct effects of tidal inundation on infaunal communities from indirect effects arising from changes in seagrass root morphology. Mensurative sampling revealed that the abundance and taxon richness of seagrass epi- and infauna, and the above- and below-ground biomass of seagrass each increased with depth across a tidal elevation gradient extending from the high intertidal to the shallow subtidal. The manipulative experiment revealed that the relative importance of direct and indirect effects of tidal inundation in determining the distribution and abundance of infauna were taxon-specific. In general, however, the facilitative effects of rhizome structure were more evident at the intertidal compared to the subtidal elevation. Our results indicate that changes to tidal inundation regime will affect seagrass-dwelling macroinvertebrates through a combination of direct and indirect effects. Therefore, future changes in tidal inundation should be taken into account in developing conservation plans for protecting seagrasses and the biodiversity they sustain.

Benthos and demersal fish habitats in the German Exclusive Economic Zone (EEZ) of the North Sea

We compiled data from different monitoring surveys to analyse and compare community and diversity patterns of fish, epi- and infauna in the German Exclusive Economic Zone (EEZ) of the North Sea in order to identify benthic habitats common to all faunal components. We found congruent community patterns of fish, epi- and infauna for the coastal waters, the Oysterground and the area called “Duck’s Bill”, which coincided with specific abiotic characteristics of these regions. The three regions were defined as special habitats for fish, epi- and infauna species in the German EEZ. The differences in the seasonal variability of abiotic factors seem to be the most important discriminating abiotic characteristic for the three habitats. The spatial distribution of fish, epifauna and infauna communities remained stable over time although habitat characteristics such as sea surface temperature increased due to climate change. However, it is expected that the coastal habitat will be more sensitive to future climate change effects in contrast to the Oysterground and Duck’s Bill habitat.

Evaluation of sampling sizes on the intertidal macroinfauna assessment in a subtropical mudflat of Hong Kong

In this study, two types of sediment cores with different diameters were used to collect sediment samples from an intertidal mudflat in Hong Kong to investigate the influence of sampling unit on the quantitative assessment of benthic macroinfaunal communities. Both univariate and multivariate analyses were employed to detect differences in sampling efficiencies by the two samplers through total abundance and biomass, species richness and diversity, community structure, relative abundance of major taxa of the infaunal community. The species-area curves were further compared to find out the influence of the sampling units. Results showed that the two sampling devices provided similar information on the estimates of species diversity, density and species composition of the benthos in main part of the mudflat where the sediment was fine and homogenous; but at the station which contained coarse sand and gravels, the significant differences were detected between the quantitative assessments of macrobenthic infauna by the two samplers. Most importantly, the species-area curves indicated that more and smaller samples were better in capturing more species than less large ones when comparing an equal sampling area. Therefore, the efficiency of the sampler largely depended on the sediment properties, and sampling devices must be chosen based on the physical conditions and desired levels of precision on the organisms of the sampling program.

Spatial variation of benthic infaunal communities in baie de Gaspé (eastern Canada) — Influence of mussel aquaculture

This study examines the effect of mussel farming on benthic infaunal communities in baie de Gaspé, eastern Canada, at two spatial scales: 10m (directly under vs. between mussel longlines — Position) and 100m (between mussel farm and reference locations — Treatment, each of which was replicated at 4 Sites). None of the evaluated univariate descriptors of benthic communities (abundance, taxonomic richness, Shannon–Weiner diversity, AMBI, and M-AMBI) differed between Treatments or among Positions within Sites in any consistent way. Similarly, multivariate community structure also did not differ among Treatments. In contrast, multivariate community structure directly under mussel lines differed from that between mussel lines in 3 of 4 mussel farm sites whereas none of the reference sites showed such 10m-scale variation. Of the species that accounted for the greatest proportion of the dissimilarity between Positions within mussel farm sites, second-order opportunistic species (Prionospio steenstrupi and Pectinaria granulata) were consistently more abundant directly under mussel lines than between them. Species belonging to other ecological groups did not show any consistent trends. It is suggested that studies that do not consider within-site (10m-scale, below vs. between longlines) variation may fail to detect the influence of suspended bivalve culture in some cases. Overall, effects of mussel culture in baie de Gaspé were slight and within the natural variation of benthic communities in the area. This suggests that the current industry should be sustainable. However, plans to expand the industry in the region remain to be evaluated with respect to the ecological carrying capacity of the entire bay.

Benthic infaunal community variability on the northern Svalbard shelf

Marine benthic communities are effective indicators of environmental change. Yet in the Arctic, there are few empirical tests of how sustained climatic change may influence community structure. Northern Svalbard is influenced by both warm Atlantic and cold Arctic water masses, providing an opportunity to assess potential effects of long-term environmental changes by examining spatial variation in community structure. We examined benthic macroinfaunal communities and sediment pigments under Atlantic and Arctic water masses on the northern shelf and fjords of Svalbard. We report on infaunal biomass, abundance, species composition, and diversity at 10 stations spanning 79°–81°N and ranging in depth from 200 to 500 m. Benthic biomass averaged 128 g WW m−2 (48–253 g WW m−2), mean density was 3,635 ind. m−2 (780–7,660 ind. m−2), and species richness varied from 45 to 136 taxa stn.−1. Abundance-based community structure clustered stations in groups related to water mass characteristics, with Atlantic and Arctic shelf stations being well distinguished from each other. Dominant taxa were different in Atlantic- and Arctic-influenced locations. Faunal biomass was highest in the Atlantic-influenced fjords, followed by Arctic fjords and Arctic shelf stations, with Atlantic shelf stations having the lowest biomass. Species richness and diversity were inversely related to biomass. Patterns in faunal biomass were strongly correlated with sedimentary pigments (R 2 = 0.74 for chl a and R 2 = 0.77 for phaeopigments), with large differences in sedimentary pigment concentration among stations. These relationships suggest that benthic fauna on the northern Svalbard shelf are food limited and dependent on predictable, albeit episodic, delivery of organic matter from the water column.

Influence of ‘bouchot’ mussel culture on the benthic environment in a dynamic intertidal system

The present study examines the influence of mussel aquaculture structures (bou- chots) in the intertidal zone of the Chausey Archipelago (Normandy, France) where strong tidal currents are predicted to disperse biodeposits. Six sites were sampled to determine the spatial variability of organic matter content, sediment grain size, and benthic infaunal community char- acteristics. The influence of bouchots on the benthic environment was evident at both the meso- scale (i.e. km-scale, between farm and reference sites) and small-scale (i.e. m-scale, spatial struc- ture within farms but not reference sites). This influence was also apparent for sediment grain size distribution and most metrics of macrobenthic community structure, but not for sediment organic matter. Mussel culture structures likely modify natural flow patterns within farm sites, which increases shear stress around individual bouchots, thereby increasing the heterogeneity of ben- thic communities, altering the dominance of particular species within farms and differentiating them from reference sites.

Marine Ecological Impact Considerations for Cruise Liner Facility Development at Two Coastal Sites in the Maltese Islands

ABSTRACT DEIDUN, A and VELLA, P., 2011. Marine Ecological Impact Considerations for Cruise Liner Facility Development at Two Coastal Sites in the Maltese Islands. In: Micallef, A. (ed.), MCRR3–2010 Conference Proceedings, Journal of Coastal Research, Special Issue, No. 61, pp. 114–122. Grosseto, Tuscany, Italy, ISSN 0749–0208. The insatiable demand for cruise liner berthing spaces as a result of the spectacular increase in cruise-mediated tourism has prompted Maltese authorities to identify additional sites to around the Maltese Islands accommodate such a development, including the Grand Harbour in Malta and Mgarr Harbour in Gozo. The study gives a broadbrush overview of the benthic infralittoral biocoenoses and assemblages and attempts to anticipate the significance of cruise terminal development-related impacts on the same habitats and communities. Ecological sampling techniques included scraping for fouling assemblages, coring for infaunal communities and semiquantitative visual census for benthic and ...

Environmental Factors Controlling the Distribution of Sediment Infauna, Az-Zour Area, South of Kuwait

The special distributions of meiofaunal and macrofaunal groups of Az-Zour area, south of Kuwait were investigated. Sediment samples were collected during July, 2004 at equilateral distances comprising eight parallel transects perpendicular to the shore. A total of 25 species of meiofauna were identified. Generally, nematodes, crustaceans and polychaetes dominated the samples with other groups forming only a minor part. 31 species of macrofauna groups were recorded. Annelida macrofauna dominated the samples with 14 species followed by Mollusca (11 species), followed by crustaceans (5 species) and Echinodermata was represented with one species and was considered very rare. The infaunal communities of the study area could be grouped into three main groups, the active borrowers, the scrapers and the filter feeders. The present investigation showed that high abundance and species diversity of the infaunal groups were recorded in the middle zone of the study area. This could be related to different sediment characteristics such as sediments grain size, total organic carbon, heavy metal and water temperature that could enable meiofaunal enrichment for the middle zone.

Spatial delineation of the depositional footprint of the Motueka River outwelling plume in Tasman Bay, New Zealand

Progress towards development of a river plume ecosystem basis for management of coastal resources requires a thorough understanding of the nature and spatial extent of terrestrial influences on receiving water and seabed characteristics. As a case study, we estimate suspended sediment (SS) loading rates from the Motueka River catchment into Tasman Bay, New Zealand and describe benthic characteristics along a series of transects encompassing the coastal river plume. A mineral-rich geological formation in the headwaters of the river was identified as a storm-generated source of highly elevated concentrations of nickel and chromium in river margin sediments, and coastal sediments extending >5 km offshore. A major storm in 2005, focused in the upper catchment, resulted in an estimated SS discharge of 161,000 tonnes into the Bay. Spatial gradients of a suite of sediment trace metal signatures, organic content and infauna community structure were used to define a river plume depositional footprint of c. 180 km2. We suggest that the boundaries of the Motueka catchment be redefined to include this area in order to facilitate engagement of marine stakeholders in management decisions that may affect coastal biological resources.

Influence of environmental factors on the dynamics of macrobenthic crustaceans on soft-bottoms of the Ebro Delta continental shelf (northwestern Mediterranean)

Short-term temporal variability in infaunal crustacean communities was evaluated against environmental variability. The area of study was located at two stations at 45 and 60 m depth under the influence of the Ebro River. Differences in the relative abundance of crustacean species between sites might be related to the distance from the river, with higher organic matter supply and finer mud content near the river. There was a marked seasonal variability linked to high phytoplankton production in spring, which supplied organic matter to the benthos, inducing higher crustacean abundance. In late summer there was a reduction in the infaunal crustacean abundance and species richness that could have been caused by two factors: the establishment of the thermocline, which could limit the availability of organic matter to the seabed, and the high water temperatures, which caused the production of phytoplankton exudates and accumulation of mucilaginous aggregates over the seabed. The 45-m site was under the influence of otter-trawl fishing and precisely in this area the seasonal variability was not observed, probably masked by the effects of trawling impact.

Influence of suspended and off-bottom mussel culture on the sea bottom and benthic habitats: a review1This review is part of a virtual symposium on current topics in aquaculture of marine fish and shellfish.

Aquaculture is the fastest growing sector of the food industry, raising concerns about the influence of this activity on the environment. We take a holistic approach to review off-bottom and suspended mussel culture effects on the benthic environment and benthic communities. Both longline and “bouchot” mussel culture add much physical structure (infrastructure and mussels) to the environment, altering hydrosedimentary processes by modifying currents and increasing sedimentation locally, and providing habitat for many benthic organisms. Biodeposition from mussels and these organisms increases benthic organic loading and linked biogeochemical processes to influence O2, pH, redox potentials, dissolved sulphides, and other sediment parameters, benthic respiration and nutrient fluxes, and benthic infaunal communities. Mussel culture may also influence seagrasses and algae, although this has not been well-studied. Far-field effects on the benthos may occur through a number of mechanisms, including aggregation of epibenthic macrofauna in culture sites, alteration of plankton communities, and the enhancement of exotic and indigenous pest species owing to the addition of physical structure to the environment. Quantitative relationships between farming level and benthic influences are lacking, making predictions of effects difficult.

Benthic mats in Antarctica: biophysical coupling of sea-bed hypoxia and sediment communities

Transient white and grey mats were observed in depressions and enclosed basins in marine sediment in the Windmill Islands, East Antarctica. These patches have not been described in the Antarctic marine environment previously although a similar phenomenon has been described in the Arctic. Our aim was to describe the sediment geochemical and biological properties inside the patches and to determine their similarity to each other. We compared the benthic infaunal communities and the chemical properties of the sediment in the white patches to nearby sediment without white mats. We observed differences in sediment pH, Eh and elemental concentrations inside and outside patches. The benthic infaunal communities inside the patches were significantly different, lower in abundance and diversity, compared to outside the patches. The structure of the microbial communities within the mats was described by constructing clone libraries from four different patches. These clone libraries were dominated by bacteria from the bacteroidetes phylum. Clones closely related to sulphur-oxidising bacteria from the gammaproteobacteria and/or the epsilonproteobacteria were present in all libraries. This is the first detailed description of these patches in the Antarctic and demonstrates the link between physico-chemical factors and microbial and infaunal community structure. It appears that this phenomenon may be driven by the formation and persistence of sea-ice, and as both the spatial extent of sea-ice and its persistence in polar regions are likely to change under predicted climate change scenarios, we suggest this is a previously undocumented mechanism for climate change to impact polar ecosystems.

The impact of a coastal invasive predator on infaunal communities: Assessing the roles of density and a native counterpart

Our understanding of the influence of many predatory invaders in areas of increasing overlap with native counterparts remains elusive. In Atlantic Canada, the European green crab, Carcinus maenas, overlaps with the native rock crab, Cancer irroratus, but surprisingly little is known about their effects in the light of their potential interactions. In this study we used short-term cage inclusion experiments to assess the impact of low and high green crab densities upon infaunal communities. Then, we re-assessed this impact by running identical manipulations combining green crabs with rock crabs of comparable size and at similar overall predator densities. Our results indicate that both low and high green crab densities accounted for severe declines in infaunal organisms with respect to ambient cages. Polychaetes, the group best represented in this trial, accounted for most of such decline with densities at least 50% lower in the green crab inclusions. A similar (~ 50%) decline in infaunal density was observed when green crabs and rock crabs were combined at low predator densities. However, at high predator densities their impact on polychaetes, molluscs and total infauna was less severe and non-significant with respect to ambient cages. Our results indicate that between-predator interactions have serious indirect effects on benthic prey and contrast previous results on the role played by these crab species. We propose a re-assessment of the role played by native counterparts while searching for management alternatives to minimize the impact of invasive predators in areas heavily invaded.

Joining forces: Combined biological and geochemical proxies reveal a complex but refined high-resolution palaeo-oxygen history in Devonian epeiric seas

Two Devonian black shale intervals were analysed using a carefully integrated palaeontological–geochemical approach to interpret relative bottom water oxygen levels at a resolution and sensitivity possible only through the combined approach. Biological data presented as both trace and body fossil abundance and size suggest generally low bottom water oxygen conditions. The frequently laminated sediments would be viewed traditionally as recording appreciable intervals of anoxic and/or euxinic (anoxic and H 2S-containing) bottom waters. The inclusion of parallel geochemical results, however, refines this perspective. Well-established iron proxies for depositional redox tell us that anoxic and euxinic conditions were intermittent and short-lived, if present at all. Manganese and molybdenum data point to conditions with a likelihood of very low oxygen in bottom waters during intervals with high pore-water concentrations of hydrogen sulphide near the sediment–water interface. These elevated sulphide concentrations under iron limited diagenetic conditions varied with organic content and may have further inhibited benthic colonization, and an active infaunal community more specifically. The combined palaeontological and geochemical data sets point to depleted bottom water oxygen contents with evidence for hydrogen sulphide limited dominantly or exclusively to the pore waters. Anoxia and euxinia, if present, occurred only intermittently and lasted only briefly, perhaps on seasonal time scales tied to primary productivity cycles or climatically induced variation in water column stratification. The time scales and mechanisms of rapid redox variation remain to be studied. The details of such transitional and dynamic settings are best viewed from a multi-proxy, biogeochemical and palaeoecological perspective. As an important byproduct, geochemical methods refined in multi-proxy studies of Phanerozoic shales can then be extended with greater utility to Precambrian strata without trace and body fossils.

Decadal changes in the benthic invertebrate community in western Lake Erie between 1981 and 2004

Faunal surveys of western Lake Erie showed a dramatic change in the species composition and abundance of the invertebrate mud-bottom community. Abundances of formerly dominant ostracods, tubificid and naidid oligochaetes, and chironomids declined 85%, 87%, 80%, and 72%, respectively, between 1982 and 2003. The majority of the declines occurred between 1982 and 1993, when dreissenid abundances were increasing rapidly. Hexagenia nymphs became important members of the infaunal community after 1993. Faunal declines were uncorrelated to weather-related variables. The frequency and magnitude of thermal stratification with accompanying hypoxic conditions during the study period remained within the normal range of variation observed in western Lake Erie. Significant wind events and storm driven seiches that might cause benthos mortality were not correlated with the decadal patterns of faunal decline. Nor were the faunal declines associated with the historical decrease in organic loading, because most of the decrease occurred prior to the study period. Nearly all abundant species declined significantly between 1982 and 1993, but deposit-feeding fauna, eutrophic indicator species, small organisms, and nearshore mud-bottom stations adjacent to dreissenid mussel habitat were most severely affected. These patterns suggest that a systemic change in the trophic structure of western Lake Erie occurred, due mostly to the invasion of dreissenid mussels nearshore and an accompanying diversion of organic matter away from deeper offshore muds. Trophic group amensalism may operate differently in marine and freshwater habitats, although dreissenids may exert ecosystem effects in the Great Lakes similar to oysters in Chesapeake Bay.

Similar effects on sediment structure and infaunal community of two competitive intertidal soft-bottom burrowing crab species

The intertidal crabs Neohelice granulata and Cyrtograpsus angulatus are common on the south-west Atlantic coast but they rarely share the same microhabitat. They are similar in size and in several life history traits which promote competition. Neohelice granulata is the dominant species in intertidal soft-sediment and salt-marsh areas from southern Brazil to northern Patagonia Argentina, where it forms extensive burrowing beds. Its burrowing activity affects sediment characteristics as well as the infaunal community. When both species coexist N. granulata constrains the distribution and modifies some population characteristics and burrowing behaviour of C. angulatus. However, C. angulatus live in burrows forming dense burrowing beds in soft-bottom intertidal areas where N. granulata is absent. Where both species coexist, C. angulatus rarely constructs burrows and N. granulata clearly dominate soft-sediment areas forming conspicuous burrowing beds. This suggests that these crab species could have similar ecological roles in some effects on sediments related to burrowing activities. In this study, we experimentally compare their effects on sediment characteristics and infaunal community. The results of the experiment showed that C. angulatus modify sediment water and organic matter contents and grain size–frequency distributions similarly to N. granulata. Neither N. granulata nor C. angulatus affected the mean abundance of infaunal organisms during the experiment but their variances showed the same patterns in many cases, indicating similar effects. These results indicate that C. angulatus can modify sediment characteristics similarly to N. granulata, and has similar interactions with infaunal species.

Habitat–diversity relationships in rocky shore algal turf infaunal communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 424:119-132 (2011) - DOI: https://doi.org/10.3354/meps08960 Habitat–diversity relationships in rocky shore algal turf infaunal communities Simon F. Thrush1,2,*, Mariachiara Chiantore1, Valentina Asnaghi1, Judi Hewitt2, Dario Fiorentino3, Riccardo Cattaneo-Vietti1 1DipTeRis, Università di Genova, Corso Europa 26, 16132 Genoa, Italy 2National Institute of Water and Atmospheric Research, PO Box 11-115 Hillcrest, Hamilton, New Zealand 3Laboratory of Zoology and Marine Biology, DiSTeBA, University of Salento, Strada provinciale Lecce-Monteroni, 73100 Lecce, Italy *Email: s.thrush@niwa.cri.nz ABSTRACT: Relationships between habitat complexity and biodiversity are a cornerstone of ecology. On many rocky shores, the cryptic macrofauna that live in the biogenic habitat created by larger organisms adds considerably to biodiversity. Algal turfs are commonly considered to facilitate high species richness of resident organisms by moderating the physically stressful characteristics of the rocky shore. We conducted a multi-scale study to describe scales of patchiness within sites and define the strength of local habitat and broader environmental variables on infaunal turf communities. Species richness contributed by sampling turf dwelling infauna increased our estimates of rocky shore diversity by >100% compared to traditional visual quadrat sampling. Generalised linear models of the species density and abundance of infaunal turf organisms and canonical correspondence analysis of community structure did not indicate a strong role for algal turf habitat complexity. Multivariate partitioning was used to assess the importance of processes operating on site and regional scales in influencing the infaunal turf community. The analysis demonstrated the importance of cross-scale relationships and high levels of unexplained variation. Analysis of biological traits demonstrated widely dispersing species were strongly influenced by broad-scale environmental factors. Feeding traits indicated that the infaunal turf community was dominated by species capable of switching strategies between autotrophic and detrital based foodwebs, with the exception of suspension feeding species. Overall, and contrary to previous studies, our results indicate wide niches for infaunal turf species and weak relationships between the infaunal community and turf habitat characteristics. Spatial variation in turf habitat characteristics was not the main driver of spatial variation in turf-dwelling organisms, implying that the habitat variability we observed was not strongly influencing physical stresses, such as temperature and wave disturbance. KEY WORDS: Algal turf · Infauna · Diversity–habitat relationships · Biological traits · Spatial scale · Mediterranean Sea Full text in pdf format PreviousNextCite this article as: Thrush SF, Chiantore M, Asnagi V, Hewitt J, Fiorentino D, Cattaneo-Vietti R (2011) Habitat–diversity relationships in rocky shore algal turf infaunal communities. Mar Ecol Prog Ser 424:119-132. https://doi.org/10.3354/meps08960 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 424. Online publication date: March 01, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Linking invertebrate burrow distributions (neoichnology) to physicochemical stresses on a sandy tidal flat: implications for the rock record

AbstractInvertebrate burrow distributions (neoichnology) across a modern tidal flat are presented as an analogue for interpreting the ichnology of palaeo‐tidal‐flat successions. Burrow distributions are linked to physical and chemical (physicochemical) stresses to establish the main controls on the distribution of biosedimentary structures. Across the tidal flat, there is clear heterogeneity in both the diversity of traces and the intensity of burrowing. This heterogeneity reflects a myriad of physicochemical stresses, with the sedimentation rate dominating burrow distributions. Across all substrates, the total area occupied by organisms rarely exceeds 3% of the tidal‐flat surface, and is commonly <1%; this equates to a bioturbation index value of one. To reach bioturbation index values of two to six, sediments must be available to biogenic reworking and/or recolonization. With an increasing sedimentation rate, substrates are rapidly buried and re‐exposed, which limits the time when a substrate is available to colonization. For palaeo‐ichnological studies, this research presents several key results. (i) Burrow cross‐cutting relationships in tidal‐flat successions commonly reflect natural heterogeneities in the areal distribution of infaunal communities, rather than infaunal tiering. (ii) Ichnofabric analysis of palaeo‐tidal flats with a high sedimentation rate would yield fabrics that reflect heterogeneities in the areal distribution of infaunal communities rather than variability in the physicochemical stresses of the environment. (iii) The composite trace‐fossil assemblage of tidal flats cannot be attributed to a single ichnofacies, but instead comprises elements typical of multiple ichnofacies. (iv) The main controls on trace assemblages across tidal flats in fully marine settings are sedimentological and include the sedimentation rate and, to a lesser extent, grain size.