Macrofaunal Species Research Articles

Associations Among Ground-Surface Spiders (Araneae) and Other Arthropods in Mesic Flatwoods

Mesic flatwoods in Florida are increasingly threatened by anthropogenic activities, and although they are known to be important for many species of macrofauna, little is known of the arthropod assemblages that inhabit them. As arthropods can be utilized as indicator taxa, we characterized the assemblages of ground-surface spiders (Araneae) and other arthropods at 2 mesic flatwood sites in Hillsborough County, Florida, and used the Chao 2, ICE (incidence-based coverage estimator), and Michaelis-Menten means species richness estimators to extrapolate the true species richness of ground-surface spiders. Sampling was conducted over a 4-month period at the sites using pitfall traps, with spiders being identified to the level of genus or species, and other arthropods to the level of order. We identified 31 spider species from 27 genera in 12 families, with Lycosidae being the dominant spider family at both sites. However, Collembola and Formicidae were the most abundant arthropod taxa. Ground-surface spiders were not strongly associated with any typical prey groups, indicating that environmental factors might also be important in structuring this community. Our results indicate that more intensive sampling of these habitats would be required to comprehensively sample and identify all of the species present, but from a management perspective, our results appear to be relatively consistent with previous surveys elsewhere.

Differential effects of microorganism-invertebrate interactions on benthic nitrogen cycling

Infaunal invertebrate activity can fundamentally alter physicochemical conditions in sediments and influence nutrient cycling. However, despite clear links between invertebrate activity and microbially mediated processes such as nitrification, the mechanisms by which bioturbating macrofauna affect microbial communities have received little attention. This study provides strong evidence for differential stimulation of microbial nitrogen transformations by three functionally contrasting species of macrofauna (Hediste diversicolor, Corophium volutator, Hydrobia ulvae). Despite increased nitrification, abundance of ammonia-oxidising bacteria (AOB) and ammonia-oxidising archaea (AOA) at the sediment-water interface did not significantly change in the presence of macrofauna. However, species-specific differences in macrofaunal activity did influence ammonia oxidiser community structure, increasing AOB abundance relative to AOA in the presence of C.volutator or H.ulvae, but with no change in H.diversicolor and no-macrofauna treatments. Denaturing gradient gel electrophoresis profiles were similar between macrofaunal treatments, although one AOB band increased in relative intensity in the presence of C.volutator, decreased in the H.diversicolor treatment and was unchanged in the H.ulvae treatment. These data suggest that links between bioturbating macrofauna and nutrient cycling are not expressed through changes in the abundance of ammonia oxidisers in surface sediments, but are associated with changes in the AOA:AOB ratio depending on the invertebrate species.

Shore height and differentials between macrobenthic assemblages in vegetated and unvegetated areas of an intertidal sandflat

Intertidal macrobenthic faunal assemblages of a dual seagrass/callianassid-structured sandflat system were investigated in subtropical Moreton Bay, Queensland. Consistently across all 20 stations, the gastropod-dominated seagrass supported greater abundance (2.5×) and species richness (2×) than the amphipod-dominated sandflat. There was no evidence of along-shore or up-shore variation in the overall assemblage properties such as total abundance, species richness or diversity within either habitat type, except for variation in sandflat abundance between sites. But seagrass and sandflat assemblages both varied significantly in composition from site to site, and seagrass assemblage composition also varied with shore height. Shore height and site, however, only accounted for ≤41% of total variation. The two faunal assemblages showed a Bray–Curtis dissimilarity of 97.7% and within-habitat similarities of <20%. There was no consistency in distribution of greater diversity, dominance or evenness. No differential between any assemblage features in adjacent sandflat and seagrass samples changed with shore height, supporting hypotheses that such differentials are not maintained by predation. Macrofaunal species richness and diversity were closely coupled within sandflat stations but were uncoupled within seagrass ones, questioning the value of diversity as a comparative measure.

Nutrient recycling by coastal macrofauna: intra- versus interspecific differences

In the context of global change, improving our understanding of how species communities shape ecosystem functioning and stability is a key issue. Therefore, we have to adopt a functional approach by considering the role of organisms in ecosystem processes. Nutrient recycling is important for sustaining primary productivity in aquatic systems but has been largely overlooked for macro-organisms. In a Mediterranean coastal ecosystem we found that per capita ammonium and phosphate excretion rates for the 9 dominant nektonic macrofauna species exceeded those of 3 benthic bivalves by factor 100. Body mass and species identity together significantly explained these interspecific differences in excretion rates. Significant differences in the effect of body mass on nutrient excretion rates were also found among the 7 fish species. More studies are needed to further explore the biological determinants of the intra-and interspecific variability of excretion rates as well as their consequences on marine ecosystem functioning.

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats: Insights from a case study in Tillamook Bay, Oregon, USA

This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared benthic macrofaunal Bray–Curtis similarity and the means of eight benthic macrofaunal community measures across seven habitat types in Tillamook Bay, Oregon, USA: intertidal eelgrass (Zostera marina), dwarf eelgrass (Zostera japonica), oyster (Crassostrea gigas) ground culture, burrowing mud shrimp (Upogebia pugettensis), burrowing ghost shrimp (Neotrypaea californiensis), sand and subtidal. Benthic macrofaunal Bray–Curtis similarity differed among all the habitats except ghost shrimp and sand. The habitat rank order on mean benthic macrofaunal species richness, abundance and biomass was dwarf eelgrass ≈ oyster ≥ mud shrimp ≈ eelgrass > sand ≈ ghost shrimp ≈ subtidal. The benthic macrofaunal habitat usage pattern in Tillamook Bay was, with a few exceptions, similar to that in two other US Pacific Northwest estuaries. The exceptions indicate variants of eelgrass and ghost shrimp habitat that differ in benthic macrofaunal usage perhaps due to differences in the coarseness of the sand fraction of the sediments in which they live. The similarities indicate periodic benthic macrofaunal usage patterns across the other habitat types extend over a wider geographic scale and range of environmental conditions than previously known.

Experimental evidence for the interacting effects of forest edge, moisture and soil macrofauna on leaf litter decomposition

Forest ecosystems have been widely fragmented by human land use. Fragmentation induces significant microclimatic and biological differences at the forest edge relative to the forest interior. Increased exposure to solar radiation and wind at forest edges reduces soil moisture, which in turn affects leaf litter decomposition. We investigate the effect of forest fragmentation, soil moisture, soil macrofauna and litter quality on leaf litter decomposition to test the hypothesis that decomposition will be slower at a forest edge relative to the interior and that this effect is driven by lower soil moisture at the forest edge. Experimental plots were established at Wytham Woods, UK, and an experimental watering treatment was applied in plots at the forest edge and interior. Decomposition rate was measured using litter bags of two different mesh sizes, to include or exclude invertebrate macrofauna, and containing leaf litter of two tree species: easily decomposing ash (Fraxinus excelsior L.) and recalcitrant oak (Quercus robur L.). The decomposition rate was moisture-limited at both sites. However, the soil was moister and decomposition for both species was faster in the forest interior than at the edge. The presence of macrofauna accelerated the decomposition rate regardless of moisture conditions, and was particularly important in the decomposition of the recalcitrant oak. However, there was no effect of the watering treatment on macrofauna species richness and abundance. This study demonstrates the effect of forest fragmentation on an important ecosystem process, providing new insights into the interacting effects of moisture conditions, litter quality, forest edge and soil macrofauna.

Variability of macrofaunal assemblages on the surroundings of a brine disposal

Desalination plants generate large volumes of hypersaline brine, likely affecting recipient communities. We aimed to assess whether proximity to a brine discharge point altered the abundance, assemblage structure and diversity of macrobenthic fauna. Collection of samples took place twice (May 2008 and January 2009) at 0, 15 and 30m away from a brine discharge point. Total macrofaunal abundance increased with increasing distance from the brine discharge point, though the magnitude of differences was inconsistent between successive years, probably as a result of a change in particle size distribution. Proximity to the brine discharge point also altered patterns in macrofaunal assemblage structure. The macrofaunal species density was higher at 15 and 30m than at 0m. In conclusion, proximity to a brine discharge point significantly altered the ecological pattern of macrobenthic fauna, though disentangling the effect of the increase in salinity from particle size distribution remains undetermined.

Do changes in microhabitat availability within a Marine Reserve reduce the species richness of small mobile macrofauna and meiofauna?

Extensive beds of the mussel Perumytilus purpuratus are a common feature of the mid-intertidal along the Chilean coast. The beds are an alternative stable state that results from the anthropogenic removal of the keystone predator Concholepas concholepas. The mussel beds constitute an important microhabitat that supports a large number of small mobile macrofaunal and meiofaunal species. This paper seeks to determine if the absence of extensive mussel beds within a Marine Reserve results in a reduced species richness. We used ‘live’ artificial mussel beds on plates to determine the species richness of fauna both inside and outside the Marine Reserve. There were no significant differences in the species richness (Smean) on plates inside and outside the Marine Reserve but there were differences with the natural mussel beds. Though the assemblages on the plates did not reach maturity ‘live’, artificial mussel beds could prove a useful tool for assessing the species richness of small mobile macrofauna and meiofauna.

β-diversity as a measure of species turnover along the salinity gradient in the Baltic Sea, and its ­consistency with the Venice System

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 436:101-118 (2011) - DOI: https://doi.org/10.3354/meps09219 β-diversity as a measure of species turnover along the salinity gradient in the Baltic Sea, and its ­consistency with the Venice System S. Bleich1,*, M. Powilleit1, T. Seifert2, G. Graf1 1Institute of Biological Sciences-Marine Biology, University of Rostock, Albert Einstein Strasse 3, 18059 Rostock, Germany 2Leibniz Institute for Baltic Sea Research, Warnemünde, Seestrasse 15, 18119 Rostock, Germany *Email: steffen.bleich@googlemail.com ABSTRACT: Transition zones between marine and freshwater environments are characterized by a pronounced salinity gradient and concomitant variation in invertebrate species richness. Here we use the β-diversity concept to depict the species turnover of macrobenthic species along the salinity gradient of the Baltic Sea with salinities ranging from 34 in the transition zone to the North Sea to less than 5 in the Bothnian Sea. Based on 250 data sets from 72 locations that were grouped into 2 habitats defined according to their depths and sediment types (shallower: 15 to 19 m, fine to medium sand; deeper: 20 to 35 m, silt to silty sand), we calculated the ­Jaccard dissimilarity index (β1–J) as a measure of species turnover. To keep the focus on the salinity gradient, sediment characteristics and the time period covered by the data sets (spring and summer 1995 to 2005) were predefined. The mean hydrographic parameters, including temperatures, salinities and dissolved oxygen (DO) concentrations of the sample locations were derived from model ­calculations based on data gathered over a 3 yr period before sampling. At the deeper stations, the total number of macrofaunal species was 255, while at the shallower ones, 172 taxa were found. Statistical analyses revealed salinity to be the main structuring factor for macrobenthic species turnover. High correlations between the β1–J index and mean salinities in both habitats (Spearman’s rank correlation coefficient ρ = 0.88 in shallower and ρ = 0.86 in deeper areas) confirmed these findings. β-diversity values with median β1–J varied between 51 and 65% within the salinity classes eu-, poly-, α-meso- and β-mesohaline, while values of 75 to 100% characterized between-group comparisons. Furthermore, these high β-diversity values depict a discontinuous change in the communities and are found at salinities of around 10, 18, and 30, which ties in fairly well with the existing salinity boundaries postulated by the Venice System. KEY WORDS: Species turnover · β-diversity · Salinity gradient · Macrofauna · Venice System · Baltic Sea Full text in pdf format PreviousNextCite this article as: Bleich S, Powilleit M, Seifert T, Graf G (2011) β-diversity as a measure of species turnover along the salinity gradient in the Baltic Sea, and its ­consistency with the Venice System. Mar Ecol Prog Ser 436:101-118. https://doi.org/10.3354/meps09219 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 436. Online publication date: August 31, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Secondary production in a Laminaria hyperborea kelp forest and variation according to wave exposure

The secondary production of mobile invertebrate fauna in the Laminaria hyperborea (Gunn.) Foslie kelp forest increases with wave exposure level. This faunal group has a key function in transferring kelp carbon to higher levels in the food web. By using a size-frequency method the calculated production was 68 (±18) g D.W. m −2 yr −1 (±S.E.) at low, 250 (±57) at medium and 308 (±64) at high exposure levels. The calculations included 30 macrofauna species, which accounted for 96% of the specimens registered, with Gastropods, amphipods and bivalves being the most abundant taxa. The calculated secondary production is high, but comparable to that previously reported from other macrophyte systems and was 3%, 8% and 8% of the total primary production at low, medium and high exposure levels, respectively. Our results indicate that large quantities of Laminaria kelp are exported from the system, although the production of sessile animals was not taken into account. The most important factor in determining faunal densities and secondary production was probably habitat size but at low exposure levels the percentage of egg-carrying crustacean females and juveniles were lower than at medium and high exposure levels, thereby indicating lower fitness for animals at low exposure stations.

Spatial and temporal distribution of macrobenthos in different mangrove ecosystems of Tamil Nadu Coast, India

This paper deals with the spatial distribution and diversity of macrobenthos and their relationships between physico-chemical parameters of the water and sediment in different mangrove habitats of Tamil Nadu, India during different seasons (2008). Among the different ecosystems of mangrove benthic faunal assemblages, macrofauna species number, density, richness, and Shannon-Wiener index were the highest and the Simpson dominance index was medial at riverine mangrove community. However, the Pielou Evenness index of riverine mangrove community was slightly lower than other communities. The similarities among the macrobenthic communities at different sampling sites were determined using Bray-Curtis similarity coefficient and ordinations of non-metric multidimensional scaling (MDS). Thirty-one species were recorded in developing (16 polychaetes, six bivalves, seven gastropods, and two crustaceans), 35 species were recorded in riverine (20 polychaetes, six bivalves, five gastropods, and four crustaceans) and 31 species were recorded in island mangrove ecosystem (19 polychaetes, four bivalves, five gastropods, and three crustaceans). Among the three ecosystems, a total of 46 benthic macrofauna consisting of 27 species of polychaetes, eight species of gastropods, seven species of bivalves, and four species of crustaceans were recorded. However, there were obvious differences among the community structures in the three mangrove habitats. This result implied that the different mangrove ecosystem had different effects on the macrofauna communities and shed light on the macrofauna adaptation capability to specific habitats.

Use of benthic vs planktonic organic matter by sandy-beach organisms: A food tracing experiment with 13C labelled diatoms

Benthic diatoms are assumed to be of minor importance as food sources in sandy-beach food webs, since they are typically scarce in sandy-beach sediments; whereas organic matter derived from land and sea is known to be more important in sandy-beach food webs. In order to test if benthic and planktonic diatoms play a minor or major role, respectively, in sandy-beach food webs, a laboratory experiment was conducted. Labelled planktonic and benthic diatoms, enriched in the stable carbon 13C isotope, were offered as food sources to sandy-beach macrofauna and meiofauna communities. Uptake of both types of diatoms occurred with most of the species, but benthic diatoms were preferentially consumed by two macrofaunal species and all meiofaunal species. This result reveals the importance of benthic carbon sources in both macrofaunal and interstitial food webs, and suggests a link between both food webs through the common use of benthic diatoms.

Soft‐bottom macrofaunal assemblages in the Gulf of Salerno, Tyrrhenian Sea, Italy, an area affected by the invasion of the seaweed Caulerpa racemosa var. cylindracea

AbstractThe spread of the introduced chlorophyte alga Caulerpa racemosa (with its variety cylindracea) in the Mediterranean Sea has been dramatic in the past decade due to its ability to cover substantial bottom areas and modify invaded habitats. From its first appearance in the mid‐1990s, C. racemosa var. cylindracea has proliferated along the soft bottom of the Gulf of Salerno (Tyrrhenian Sea), which in its central part was largely unvegetated. A long‐term assessment of the macrofaunal assemblages from this area was conducted based on a comparison between a historical dataset of macrofaunal species and abundances obtained in 1981, before the introduction of the alga, and datasets derived from sampling performed in 2006 and 2007 at the same stations. The aim of the comparison was to explore whether a detectable change occurred in the degree of diversity and in the composition of macrofaunal assemblages and, if this occurred, whether such change could be attributed, at least in part, to the C. racemosa colonization in the area. Although overall local diversity did not change in the study area, the composition of the macrofaunal assemblages in 2006–2007 differed from that in 1981. The most conspicuous changes were a decline in infaunal bivalve molluscs and an increase of mobile epibenthic forms (notably the mollusc Nassarius pygmaeus); these may be linked to the influence of C. racemosa on sediment properties. The dominance of some species (mainly polychaetes) may be associated with other environmental factors such as the intensity of riverine inputs. The impact of the invasive alga appears to vary according to the habitat invaded.

Contamination on sandflats and the decoupling of linked ecological functions

AbstractBenthic macrofauna can influence inputs and transformations of energy and matter in estuaries, affecting both the stocks of vital materials (e.g. carbon, oxygen) and the rates of key processes (e.g. organic matter decomposition, nutrient uptake). Although a number of studies have identified shifts in functional groups or biological traits in relation to anthropogenic stressors, there have been few field‐based assessments of changes in functioning associated with stress gradients. We used a comparative experimental approach to investigate functioning on two sandflats with differing exposures to urban contaminants. Apart from significant differences in sediment contaminant concentrations (43.2 ± 1.8 mg kg−1Zn and 15.6 ± 0.9 mg kg−1Pb at the Pollen site; 17.7 ± 0.7 mg kg−1Zn and 7.9 ± 0.9 mg kg−1Pb at the Waiheke site), the two sandflats were readily comparable: both had similar sediment grain size distributions and were dominated by the same macrofaunal species; and both were in non‐eutrophic New Zealand marine reserves with low ambient sediment organic matter content. To better understand the effects of contaminants on biologically mediated transformations of organic matter into inorganic nutrients, we manipulated sediment organic matter content and macrofaunal abundance in standardized treatments at each site. Fluxes of oxygen and ammonium, which are linked to key sandflat processes such as organic matter decomposition and benthic photosynthesis, were measured as response variables 1 week after the experimental manipulations. We predicted more efficient organic matter processing on the uncontaminated flat and thus expected to see elevated ammonium efflux in response to organic enrichment treatments at this site. Higher rates of benthic photosynthesis were predicted for plots with higher ammonium efflux, as ammonium is a readily utilizable form of limiting inorganic nitrogen. We documented significant positive relationships between ammonium uptake and benthic primary production on the uncontaminated flat, but weaker/insignificant relationships at the contaminated site. Our data were consistent with theories of increased variability and a decoupling of system processes with increasing amounts of stress.

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats in the US Pacific Northwest

This study shows that spatially and temporally recurring benthic macrofauna–habitat patterns validate the ecological relevance of habitat types to benthic macrofauna and suggest they can serve as elements in ecological periodic tables of benthic macrofaunal usage. We discovered patterns across nine habitat types (intertidal eelgrass [ Zostera marina], dwarf eelgrass [ Zostera japonica], oyster [ Crassostrea gigas] ground culture, burrowing mud shrimp [ Upogebia pugettensis], burrowing ghost shrimp [ Neotrypaea californiensis], shell, sand, mud, and subtidal) on a variety of benthic macrofaunal community state variables in Grays Harbor, Washington, USA and compared them to those in Willapa Bay, Washington, USA. There were nominal differences in benthic macrofaunal Bray–Curtis similarity between all the habitats investigated except eelgrass and oyster in both estuaries. Across-habitat patterns on mean benthic macrofaunal species richness, abundance, biomass, abundance of deposit, suspension and facultative feeders, a dominance and a diversity index for the five habitats common to both studies were the same on a rank measurement scale: eelgrass ≈ oyster > mud shrimp > ghost shrimp ≈ subtidal. The patterns for most of the habitats and benthic macrofaunal measures were the same on a ratio measurement scale.

Antarctic intertidal limpet ecophysiology: A winter–summer comparison

The Antarctic intertidal zone is one of the world's most extreme marine environments. As well as having a typically high annual temperature variation (~ 30 °C), it is affected by frequent ice scouring in summer and ice encasement in winter, as well as substantial salinity fluctuations during tidal cycles. For many years the Antarctic intertidal was believed to host only migratory species during summer, however, recent studies have found several permanently resident macrofaunal species, including the limpet Nacella concinna. Here we present results of the first seasonal comparison of different ecophysiological parameters in this species collected from the intertidal in both winter (August and September) and summer (January and February) on Adelaide Island (West Antarctic Peninsula). There was clear evidence of seasonal acclimatisation with a shift in thermal window between winter and summer limpets. The seasonal change in metabolic rate did not show increased costs in winter ( cf metabolic cold adaptation) and the seasonal increase in oxygen consumption was within the range expected due to the physical effects of temperature alone. O:N ratios indicated that the animals were using the same metabolic substrate (mainly protein) all year round. There was no significant difference in condition factor between winter and early summer individuals. However comparisons with subtidal N. concinna showed that those from the intertidal had a lower condition factor than those permanently immersed. Whilst remaining in the ice-encased intertidal during winter may give access to ice-algae and microphytobenthos in the shallows and provide a feeding advantage early in the season, there are clearly extra costs to living in the intertidal per se. Hence N. concinna may not derive any obvious fitness advantage but may simply be occupying an available niche and surviving the physical challenges in the shallows.

Changes in North Sea macrofauna communities and species distribution between 1986 and 2000

The North Sea Benthos Project 2000 was initiated as a follow-up to the 1986 ICES North Sea Benthos Survey with the major aim to identify changes in the macrofauna species distribution and community structure in the North Sea and their likely causes. The results showed that the large-scale spatial distribution of macrofauna communities in the North Sea hardly changed between 1986 and 2000, with the main divisions at the 50 m and 100 m depth contours. Water temperature and salinity as well as wave exposure, tidal stress and primary production were influential environmental factors on a large (North Sea-wide) spatial scale. The increase in abundance and regional changes in distribution of various species with a southern distribution in the North Sea in 2000 were largely associated with an increase in sea surface temperature, primary production and, thus, food supply. This can be most likely related to the North Sea hydro-climate change in the late 1980s influenced by the variability in the North Atlantic Oscillation (NAO). Only one cold-temperate species decreased in abundance in 2000 at most of the stations. Indications for newly established populations of offshore non-native species were not found. Differences in macrofauna community structure on localised spatial scales were predominantly found north of the 50 m depth contour off the British coast along the Flamborough Head Front towards the Dogger Bank, off the coast of Jutland and at the Frisian Front. These changes were most likely attributed to stronger frontal systems in 2000 caused by the increased inflow of Atlantic water masses in relation to the hydro-climate change in the late 1980s.

Little change in the distribution of rocky shore faunal communities on the Australian east coast after 50 years of rapid warming

Rocky shore faunal communities are tractable systems which are sensitive to climate change. Here, we resurveyed a historical census of rocky shore fauna conducted in the 1940s and 1950s to assess whether there were latitudinal changes in distribution and abundance consistent with global climate change along Australia's east coast. This region has undergone rapid warming, with increases in temperature of ~ 1.5 °C over the past 60 years. We also tested a historical hypothesis that a dramatic transition from tropical species to temperate species at 25°S represents a biogeographical boundary caused by environmental transitions in wave action and dispersal barriers. Twenty-two rocky shores were sampled between 23°S and 35°S, covering 1500 km of the coastline. A total of 80 species of macro-fauna were identified. Historical comparison of the 30 most common species revealed little change in species distribution with warming ocean temperature. We conclude that the environmental transition driven by wave exposure, local currents and the presence of large sand islands, and not temperature, is the primary factor influencing biogeographic distributions along the subtropical east coast of Australia.

Pliocene–Pleistocene stratigraphy and macrofauna of the Farasan Islands, South East Red Sea, Saudi Arabia

The stratigraphy of the Farasan Islands (Pliocene–Pleistocene deposits) is established on the basis of a detailed study of six stratigraphic sections described and sampled in the field. Detailed examinations involve the microfacies analyses and identification of macrofossils makes it possible to determine two new informal formations, namely, from the base to the top: Esbah formation of Pliocene age and Farasan formation of Pleistocene age. The detected microfacies types of the studied samples are only carbonate facies and include five major types: mudstone, wackestone, packstone, floatstone and boundstone. No grains of quartz sand or igneous mineral were found in the islands. The nomenclature of the biostratigraphic units established in the present work is not intended to define world-wide zonal standards. It is only used to subdivide the sequence into biostratigraphic zones according to 137 macrofaunal species (78 bivalves, 56 gastropods and three echinoids). These biozones, namely: Lithophaga teres zone (Early Pliocene), Clypeaster reticulates–Laganum depressum zone and Chesapecten madisonius–Noetia limula interval zone are assigned to the Late Pliocene; meanwhile, Noetia limuli–Anadara ovalis interval zone and A. ovalis range zone are assigned to the Pleistocene age. The affinity of the Pliocene–Pleistocene fauna recorded from the Farasan Islands increase with time towards the Indo-Pacific realm. The identified bivalves and gastropods are dominated by the Indo-Pacific forms suggesting the connection of the Red Sea rift with the open Indian Ocean via the Gulf of Aden and Bab El Mandab in the latest Miocene and Early Pliocene.

Polychaete invader enhances resource utilization in a species-poor system

Ecosystem consequences of biodiversity change are often studied from a species loss perspective, while the effects of invasive species on ecosystem functions are rarely quantified. In this experimental study, we used isotope tracers to measure the incorporation and burial of carbon and nitrogen from a simulated spring phytoplankton bloom by communities of one to four species of deposit-feeding macrofauna found in the species-poor Baltic Sea. The recently invading polychaete Marenzelleria arctia, which has spread throughout the Baltic Sea, grows more rapidly than the native species Monoporeia affinis, Pontoporeia femorata (both amphipods) and Macoma balthica (a bivalve), resulting in higher biomass increase (biomass production) in treatments including the polychaete. Marenzelleria incorporated and buried bloom material at rates similar to the native species. Multi-species treatments generally had higher isotope incorporation, indicative of utilization of bloom material, than expected from monoculture yields of the respective species. The mechanism behind this observed over-yielding was mainly niche complementarity in utilization of the bloom input, and was more evident in communities including the invader. In contrast, multi-species treatments had generally lower biomass increase than expected. This contrasting pattern suggests that there is little overlap in resource use of freshly deposited bloom material between Marenzelleria and the native species but it is likely that interference competition acts to dampen resulting community biomass. In conclusion, an invasive species can enhance incorporation and burial of organic matter from settled phytoplankton blooms, two processes fundamental for marine productivity.