Bad neighbors? Niche overlap and asymmetric competition between native and Lessepsian limpets in the Eastern Mediterranean rocky intertidal.

Abstract The Eastern Mediterranean Sea hosts more non-indigenous species than any other marine region, yet their impacts on the native biota remain poorly understood. Focusing on mollusks from the Israeli rocky intertidal, we explored the hypothesis that this abiotically harsh habitat supports a limited trait diversity, and thus may promote niche overlap and competition between native and non-indigenous species. Indeed, native and non-indigenous assemblage components often had a highly similar trait composition, caused by functionally similar native (Patella caerulea) and non-indigenous (Cellana rota) limpets. Body size of P. caerulea decreased with increasing C. rota prevalence, but not vice versa, indicating potential asymmetric competition. Although both species have coexisted in Israel for >15 years, a rapid 'replacement' of native limpets by C. rota has been reported for a thermally polluted site, suggesting that competition and regionally rapid climate-related seawater warming might interact to progressively erode native limpet performance along the Israeli coast

Effect of hypoxia and anoxia on invertebrate behaviour: Ecological perspectives from species to community level

Coastal hypoxia and anoxia have become a global key stressor to marine ecosystems, with almost 500 dead zones recorded worldwide. By triggering cascading effects from the individual organism to the community-and ecosystem level, oxygen depletions threaten marine biodiversity and can alter ecosystem structure and function. By integrating both physiological function and ecological processes, animal behaviour is ideal for assessing the stress state of benthic macrofauna to low dissolved oxygen. The initial response of organisms can serve as an early warning signal, while the successive behavioural reactions of key species indicate hypoxia levels and help assess community degradation. Here we document the behavioural responses of a representative spectrum of benthic macrofauna in the natural setting in the Northern Adriatic Sea (Mediterranean). We experimentally induced small-scale anoxia with a benthic chamber in 24 m depth to overcome the difficulties in predicting the onset of hypoxia, which often hinders full documentation in the field. The behavioural reactions were documented with a time-lapse camera. Oxygen depletion elicited significant and repeatable changes in general (visibility, locomotion, body movement and posture, location) and species-specific reactions in virtually all organisms (302 individuals from 32 species and 2 species groups). Most atypical (stress) behaviours were associated with specific oxygen thresholds: arm-tipping in the ophiuroid Ophiothrix quinquemaculata, for example, with the onset of mild hypoxia (< 2 mL O2 L-1), the emergence of polychaetes on the sediment surface with moderate hypoxia (< 1 mL O 2 L-1), the emergence of the infaunal sea urchin Schizaster canaliferus on the sediment with severe hypoxia (< 0.5 mL O 2 Lg-1) and heavy body rotations in sea anemones with anoxia. Other species changed their activity patterns, for example the circadian rhythm in the hermit crab Paguristes eremita or the bioherm-associated crab Pisidia longimana. Intra-and interspecific reactions were weakened or changed: decapods ceased defensive and territorial behaviour, and predator-prey interactions and relationships shifted. This nuanced scale of resolution is a useful tool to interpret present benthic community status (behaviour) and past mortalities (community composition, e.g. survival of tolerant species). This information on the sensitivity (onset of stress response), tolerance (mortality, survival), and characteristics (i.e. life habit, functional role) of key species also helps predict potential future changes in benthic structure and ecosystem functioning. This integrated approach can transport complex ecological processes to the public and decision-makers and help define specific monitoring, assessment and conservation plans. © 2014 Author (s).This study was financed by the Austrian Science Fund (FWF; projects P17655-B03 and P21542-B17) and supported by the OEAD Bilateral Slovenian Austrian Scientific Technical Cooperation project SI 22/2009Peer Reviewe

TRACING ORIGIN AND COLLAPSE OF HOLOCENE BENTHIC BASELINE COMMUNITIES IN THE NORTHERN ADRIATIC SEA

The shallow northern Adriatic Sea has a long history of anthropogenic impacts that reaches back many centuries. While the effects of eutrophication, overfishing, pollution, and trawling over recent decades have been extensively studied, the major ecological turnovers during the Holocene as a whole remain poorly explored. In this study, we reconstruct ecological baselines defining benthic ecosystem composition prior to major anthropogenic changes at four stations characterized by low sedimentation and millennial-scale time averaging of molluscan assemblages. We discriminate between natural and anthropogenic drivers based on (1) stratigraphic changes in the composition of molluscan communities observed in sediment cores and (2) changes in concentrations of heavy metals, pollutants, and organic enrichment. The four 1.5-m long sediment cores reach back to the Pleistocene–Holocene boundary, allowing for a stratigraphic distinction of the major sea-level phases of the Holocene. During the transgressive phase and maximum flooding, sea-level and establishment of the modern circulation pattern determined the development of benthic communities in shallow-water, vegetated habitats with epifaunal biostromes and, in deeper waters, with bryozoan meadows. After sea-level stabilization, the composition of these baseline communities remained relatively uniform and started to change markedly only with the intensification of human impacts in the late highstand, leading to a dominance of infauna and a decline of epifauna at all sites. This profound ecological change reduced species richness, increased the abundance of infaunal suspension feeders, and led to a decline of grazers and deposit feeders. We suggest that modern soft-bottom benthic communities in the northern Adriatic Sea today do not show the high geographic heterogeneity in composition characteristic of benthos prior to anthropogenic influences

Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments

Beta diversity, the compositional variation among communities, is often associated with environmental gradients. Other drivers of beta diversity include stochastic processes, priority effects, predation, or competitive exclusion. Temporal turnover may also explain differences in faunal composition between fossil assemblages. To assess the drivers of beta diversity in reef-associated soft-bottom environments, we investigate community patterns in a Middle to Late Triassic reef basin assemblage from the Cassian Formation in the Dolomites, Northern Italy, and compare results with a Recent reef basin assemblage from the Northern Bay of Safaga, Red Sea, Egypt. We evaluate beta diversity with regard to age, water depth, and spatial distance, and compare the results with a null model to evaluate the stochasticity of these differences. Using pairwise proportional dissimilarity, we find very high beta diversity for the Cassian Formation (0.91 ± 0.02) and slightly lower beta diversity for the Bay of Safaga (0.89 ± 0.04). Null models show that stochasticity only plays a minor role in determining faunal differences. Spatial distance is also irrelevant. Contrary to expectations, there is no tendency of beta diversity to decrease with water depth. Although water depth has frequently been found to be a key factor in determining beta diversity, we find that it is not the major driver in these reef-associated soft-bottom environments. We postulate that priority effects and the biotic structuring of the sediment may be key determinants of beta diversity

Alleged Lessepsian foraminifera prove native and suggest Pleistocene range expansions into the Mediterranean Sea

Biogeographical patterns are increasingly modified by the human-driven translocation of species, a process that accelerated several centuries ago. Observational datasets, however, rarely range back more than a few decades, implying that a large part of invasion histories went unobserved. Small-sized organisms, like benthic foraminifera, are more likely to have been reported only recently due to their lower detectability compared to larger-sized organisms. Recently detected native species of tropical affinity may have thus been mistaken for non-indigenous species due to the lack of evidence of their occurrence in pre-invasion records. To uncover the unobserved past of the Lessepsian invasion—the entrance of tropical species into the Mediterranean through the Suez Canal—we collected sediment cores on the southern Israeli shelf. We deployed state-of-the-art radiocarbon techniques to date 7 individual foraminiferal tests belonging to 5 alleged non-indigenous species and show that they are centuries to millennia old, thus native. Two additional species previously considered non-indigenous occurred in centennial to millennia-old sediments, suggesting their native status. The evidence of multiple tropical foraminiferal species supposed to be non-indigenous but proved native in the eastern Mediterranean suggests either survival in refugia during the Messinian Salinity Crisis (5.96−5.33 million years) or, more likely, dispersal from the tropical Atlantic and Indo-Pacific during the Pleistocene. In the interglacials of this epoch, higher sea levels may have allowed biological connectivity between the Mediterranean and the Red Sea for shallow-water species, showing that the Isthmus of Suez was possibly a more biologically porous barrier than previously considered

SPECTACULAR INSIGHTS INTO ESTUARINE TO SHALLOW MARINE SEDIMENTS OF THE KARPATIAN (LOWER MIOCENE) IN THE KORNEUBURG BASIN (LOWER AUSTRIA)

The Korneuburg Basin in Lower Austria, about 18 km north of Vienna, is a ca 20 km long and at most 7 km wide asymmetric pull-apart basin formed within the Alpine-Carpathian thrustbelt during last Alpine movements in the Karpatian (late Early Miocene). During the construction of the S1 motorway south of Stetten a ca 1.8 km long section between the Tradenberg tunnel and the city of Korneuburg was geologically documented in detail (fig. 1). A flysch-elevation in the area of profile E (fig. 1) divides the section in an eastern (profiles A, F) and a western part (profiles G, D, D1, B, C1, C) causing an increasing number of faults in the Miocene sediments towards the vicinity of the flysch. In the western part constantly 20° to 30° westward dipping marl, marly silts and fine to medium sands, in some parts with intercalations of lignite and coaly clay were cropping out, whereas in the eastern part the westward dipping of similar sediments is changing to an eastward nearby the flysch high.Rich fossil content documents sedimentation in mudflats, coastal swamps and shallow sublittoral settings within an estuary. Autochthonous Lower Miocene nannofossils represented by stratigraphical important forms like Helicosphaera ampliaperta Bramlette et Wilcoxon, 1967, H. carteri (Wallich 1877) Kamptner 1954, Reticulofenestra excavata Lehotayova, 1975, Sphenolithus cf. heteromorphus Deflandre 1953, indicating nannoplankton Zone NN4 (Martini 1971). The mollusc fauna documents changing environmental conditions along the sampled transect. Nearby terrestrial habitats and freshwater influence are indicated by planorbids, hydrobiids and Melanopsis impressa. An enormous biodiversity with more than 650 taxa was documented from these paleoenvironments, allowing also precise climatic reconstruction from palynologic data: within subtropical climatic conditions intertidal to very shallow subtidal marine environments and brackish water with Agapilia pachii, Granulolabium plicatum, Terebralia bidentata, Crassostrea gryphoides, and Perna aquitanica; whereas deeper subtidal and fully marine conditions are documented by Turritella, Nassarius, Anadara, muricid gastropods, or venerids. Foraminiferal assemblages are dominated by benthic foraminifera and document brackish to shallow marine paleoenvironments. Most frequent genera are Ammonia, Aubignyna and elphidiids. Quiet water assemblages are indicated by higher portions of Caucasina and Nonion. The found assemblages enable us to trace sea level changes within the sections. They correspond largely to those described earlier by Rögl (1998). A complete measurement by hand-held gammalog spectral analysis detected throughout the succession prominent, highly significant periodicities with stratigraphic distance ranging from 12 m to 25 m, which have been interpreted as 21-kyr-precession signal. This indication for astronomical forcing allows further discussion of a reliable age-model for this section of the Korneuburg Basin

A decline in molluscan carbonate production driven by the loss of vegetated habitats encoded in the Holocene sedimentary record of the Gulf of Trieste

Carbonate sediments in non-vegetated habitats on the north-east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarceand (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand-dwelling Gouldia minima and opportunistic Corbula gibba are time-averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co-occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre-scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top-core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft-bottom vegetated zones and hard-bottom Arca beds) and present-day oligophotic communities with organic-loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats

Diversity, habitats and size-frequency distribution of the gastropod genus <i>Conus</i> at Dahab in the Gulf of Aqaba, Northern Red Sea

<p>Topographically complex subtidal reefs of the Indo-West Pacific region are characterised by a high species richness of cone snails of the genus <i>Conus</i> (up to 36 on some reefs) but low population densities (≤1 individual/m²), whereas <i>Conus</i> assemblages on reef flats usually support fewer species (5–9) and high population densities (up to 5.2 individuals/m²). Subtidal sand areas are known to be least species-rich (1–6 species). Although the diversity of this predatory gastropod genus has been described previously from different areas of the Indo-Pacific, little ecological information is available on <i>Conus</i> in the Northern Red Sea. Therefore, data from five habitat types were obtained along 73 line-transects (245 m²⁾, which yielded ecological data for a total of 175 individuals of 9 species. In accordance with former findings, our results demonstrate that the reef flat was the habitat with the highest observed population densities (6.15 individuals/m²) but low species diversity (<i>H</i>’ = 0.9; 5 species); subtidal reefs, in contrast, were characterised by low densities (0.13 individuals/m²) and a relatively high species diversity (<i>H ‘</i>= 1.5; 6 species). This suggests that <i>Conus</i> diversity and species richness in the Northern Red Sea around Dahab is lower than in other parts of the Indo-West Pacific region. Furthermore, hardand soft substrata were dominated by different <i>Conus</i> species in accordance to the distribution of favourable microhabitat patches, the degree of physical stress and the availability of refuges and prey organisms. The fact that these <i>Conus</i> were predominantly small-bodied vermivores (size range: 6–85 mm; mean shell size: 15 mm; SD = 9 mm) suggests that this size class possesses an advantage over molluscivores and piscivores. Except for subtidal reefs, which showed a highly variable species composition, the studied habitat types around Dahab were characterised by distinct assemblages of <i>Conus</i>.</p