Sediment distribution and accumulation in lagoons of the Southern Mediterranean Region (the MELMARINA Project) with special reference to environmental change and aquatic ecosystems

Surface sediments and sediment cores were collected from coastal lagoons and lakes located in the Southern Mediterranean Region (SMR) as part of the MELMARINA Project which involved integrated eco-hydrological monitoring and modelling. This study uses surface sediments and sediment cores to infer spatial characteristics and temporal changes at the MELMARINA primary sites, Merja Zerga in Morocco, Ghar El Melh in Tunisia and Lake Manzala in Egypt. In addition, surface sediment sampling was undertaken at Egyptian Lake Bardawil and sediment cores were collected from the Lagune de Nador (Morocco). Sediment distribution patterns are investigated using GIS with georeferenced sample locations to facilitate display and resurvey. Major variations in sedimentary organic matter and, particularly, carbonate content, occur within and between sites. Local landscapes combined with hydrological and biogeochemical processes influence the distributions of sediment bulk components (carbonates, organic material and clastic matter) and molluscan shells and shell debris are an important source of sedimentary carbonate at all three primary sites. Sediment cores were dated using natural (²¹⁰Pb) and artificial (¹³⁷Cs) radionuclides, and sediment accumulation rate changes indicate that sources of sediment supply varied markedly through the twentieth century but have generally diminished after the mid-1960s. Sedimentary siliceous microfossils (diatoms) were generally poorly preserved, but mollusc shell remains were well represented. Sediment chronologies and sediment bulk composition allow discussion of some recent changes in bulk, minerogenic and biogenic sediment accumulation patterns in the SMR lagoons. Sediment accumulation rates also varied between sites and multiple cores from Lake Manzala indicated that rates showed considerable spatial variability. Low-level sediment contamination by fossil fuel combustion particulates and trace metals was demonstrated for Ghar El Melh and Lagune de Nador where Pb and Zn accumulation rates were highest in twentieth century sediment. It is emphasized that sediment quality and quantity have strong influences on lagoon ecosystem function and sedimentation is relevant to hydromorphology and to concepts of ecological quality. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: J. R. Thompson & R. J. Flower Hydro-ecological Monitoring and Modelling of North African Coastal Lagoons     

New ages for Middle and Later Stone Age deposits at Mumba rockshelter, Tanzania: optically stimulated luminescence dating of quartz and feldspar grains

The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ∼60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for Mumba, and briefly discuss how the revised chronology fits in the context of existing archaeological records and palaeoclimatic reconstructions for East Africa.     

Porewater mixing by microorganisms,monitored by a radiotracer method

Bioturbation is an important process for the transport and mixing of solutes and particles in sediments. Mixing of porewater caused by motile microorganisms has not previously been considered to be of significance in this context, although no conclusive evidence that it is negligible has been presented. We have developed a radiotracer method for the direct comparison of mixing of a soluble inert substance in microbially active and sterile sediments. We found clear evidence of porewater mixing caused by motile microorganisms. Estimated diffusion coefficients (expressed as “mixing”; coefficients) were found to be about 20% larger in microbially active sediments than in sterile ones.     

Advances in optically stimulated luminescence dating of individual grains of quartz from archeological deposits

Paleoanthropologists and archeologists interested in occupation histories, faunal remains, and objects of material culture have become increasingly reliant on optically stimulated luminescence (OSL) dating to construct Quaternary chronologies. In part, the increased use of OSL dating reflects its capacity to date events beyond the range of radiocarbon dating and in contexts where suitable organic materials are absent. An earlier review in Evolutionary Anthropology by Feathers 1 provides a general account of the principles of luminescence dating. Since then, however, important advances have been made in OSL dating of quartz, so that it is now possible to date individual sand‐sized grains and thereby resolve issues of postdepositional mixing of archeological sediments. In this review, we discuss the most important of these advances and their implications with regard to improved age control of archeological sites. We cover aspects of instrumental and methodological development that have facilitated the widespread measurement of single grains related to archeological questions and illustrate our review with some examples of where archeological problems have been resolved using single‐grain OSL dating. We do not propose single‐grain dating as a panacea, because there are instances where it is not straightforward to use or the results may be difficult to interpret; dating in such contexts remains the subject of continuing research.     

Small and large mammals from the Ciota Ciara cave (Borgosesia,Vercelli, Italy): An Isotope Stage 5 assemblage

The Ciota Ciara cave is located within the Monte Fenera karst system (Borgosesia, Vercelli, Italy) at 670 m a.s.l. The cave entrance presents a deposit with Mousterian quartz and flint industry. The faunal remains from Stratigraphic Units 13, 14 and 103 are the subject of this work and are presented here as a whole for the first time. The large mammal assemblage is dominated by Ursus spelaeus. In addition, a few remains of carnivores such as Panthera leo spelaea, Panthera pardus, Meles meles have been found together with ungulates such as Cervus elaphus and Rupicapra rupicapra. The small mammal assemblage is characterized by a high biodiversity, especially in bats, by the dominance of Clethrionomys glareolus and by a relatively large number of Pliomys coronensis, a species that seems to disappear from the Italian Peninsula at the end of Marine Isotope Stage 5 or during the beginning of MIS 4. The changes in frequency of the small and large mammals between the two S.U. suggest a change from a relatively cold-humid (S.U. 14) to a warmer-still humid climate (S.U. 13). Although no radiometric dates are available yet, the small and large mammal assemblages, the presence of Pliomys coronensis and the climate change inferred by the variation of the small mammal frequencies allow us to correlate these two units of the Ciota Ciara cave to a relatively warm moment of Marine Isotope Stage 5.     

Diversity of sulfur-cycle prokaryotes in freshwater lake sediments investigated using aprA as the functional marker gene

The diversity of sulfate-reducing prokaryotes (SRPs) and sulfur-oxidizing prokaryotes (SOPs) in freshwater lake ecosystems was investigated by cloning and sequencing of the aprA gene, which encodes for a key enzyme in dissimilatory sulfate reduction and sulfur oxidation. To understand their diversity better, the spatial distribution of aprA genes was investigated in sediments collected from six geographically distant lakes in Antarctica and Japan, including a hypersaline lake for comparison. The microbial community compositions of freshwater sediments and a hypersaline sediment showed notable differences. The clones affiliated with Desulfobacteraceae and Desulfobulbaceae were frequently detected in all freshwater lake sediments. The SOP community was mainly composed of four major phylogenetic groups. One of them formed a monophyletic cluster with a sulfur-oxidizing betaproteobacterium, Sulfuricella denitrificans, but the others were not assigned to specific genera. In addition, the AprA sequences, which were not clearly affiliated to either SRP or SOP lineages, dominated the libraries from four freshwater lake sediments. The results showed the wide distribution of some sulfur-cycle prokaryotes across geographical distances and supported the idea that metabolic flexibility is an important feature for SRP survival in low-sulfate environments.     

The functional group approach to bioturbation: II. The effects of the Macoma balthica community on fluxes of nutrients and dissolved organic carbon across the sediment-water interface

We have examined the effects of individual members of the two dominant functional groups of the Macoma balthica community on fluxes of nutrients and dissolved organic carbon between sediment and overlying water. The biodiffusers M. balthica and Mya arenaria and the gallery-diffuser Nereis virens were added to microcosms containing sieved tidal flat sediment, using identical biovolume for each treatment to facilitate comparison. Both functional groups enhanced fluxes over a control without macrofauna. The gallery-diffuser had the greatest effect. The two biodiffusers had opposite effects on the flux of nitrate. M. balthica, which lives near the sediment surface, caused nitrate release whereas M. arenaria caused nitrate uptake. Both organisms increased the release of ammonia, but M. arenaria had the greater effect. We attribute this intra-functional difference not so much to different functionality as to interactions between organisms and the depth distribution of pore water constituents. Because the burrow of M. balthica is located within the nitrification zone of the sediment, the depth averaged concentration of nitrate in its burrow is higher than in the overlying water, and burrow flushing leads to net release of nitrate. In contrast, the burrow of M. arenaria includes both nitrification and denitrification zones, which lower the depth averaged concentration of nitrate below the concentration in the overlying water. The functional group approach needs to take the processes that control sediment chemistry into account in order to predict fluxes sucessfully.     

Novel pathways that contribute to the anti-proliferative and chemopreventive activities of calcitriol in prostate cancer

Calcitriol, the hormonally active form of Vitamin D, inhibits the growth and development of many cancers through multiple mechanisms. Our recent research supports the contributory role of several new and diverse pathways that add to the mechanisms already established as playing a role in the actions of calcitriol to inhibit the development and progression of prostate cancer (PCa). Calcitriol increases the expression of insulin-like growth factor binding protein-3 (IGFBP-3), which plays a critical role in the inhibition of PCa cell growth by increasing the expression of the cell cycle inhibitor p21. Calcitriol inhibits the prostaglandin (PG) pathway by three actions: (i) the inhibition of the expression of cyclooxygenase-2 (COX-2), the enzyme that synthesizes PGs, (ii) the induction of the expression of 15-prostaglandin dehydrogenase (15-PGDH), the enzyme that inactivates PGs and (iii) decreasing the expression of EP and FP PG receptors that are essential for PG signaling. Since PGs have been shown to promote carcinogenesis and progression of multiple cancers, the inhibition of the PG pathway may add to the ability of calcitriol to prevent and inhibit PCa development and growth. The combination of calcitriol and non-steroidal anti-inflammatory drugs (NSAIDs) result in a synergistic inhibition of PCa cell growth and offers a potential therapeutic strategy. Mitogen activated protein kinase phosphatase 5 (MKP5) is a member of a family of phosphatases that are negative regulators of MAP kinases. Calcitriol induces MKP5 expression in prostate cells leading to the selective dephosphorylation and inactivation of the stress-activated kinase p38. Since p38 activation is pro-carcinogenic and is a mediator of inflammation, this calcitriol action, especially coupled with the inhibition of the PG pathway, contributes to the chemopreventive activity of calcitriol in PCa. Mullerian Inhibiting Substance (MIS) has been evaluated for its inhibitory effects in cancers of the reproductive tissues and is in development as an anti-cancer drug. Calcitriol induces MIS expression in prostate cells revealing yet another mechanism contributing to the anti-cancer activity of calcitriol in PCa. Thus, we conclude that calcitriol regulates myriad pathways that contribute to the potential chemopreventive and therapeutic utility of calcitriol in PCa.     

A new Late Pleistocene non-anthropogenic vertebrate assemblage from the northern Iberian Peninsula: Artazu VII (Arrasate,Basque Country)

Late Pleistocene palaeontological sites without human intervention are limited in the Cantabrian region, and even more so those with a good state of preservation and rich biodiversity. A new vertebrate fossiliferous locality discovered at Kobate Quarry (Arrasate, northern Iberian Peninsula) is presented in this article. This site, in which remains of 40 different vertebrate taxa were accumulated, acted as a natural trap. The preliminary vertebrate faunal list includes five amphibian taxa, four reptiles, seven species of birds and 24 mammalian taxa. While small mammals are represented by 13 small mammal taxa (seven in the Order Rodentia, five in the Order Eulipotyphla, and one in the Order Chiroptera), the large mammal fauna comprises eleven species, including ungulates and carnivores. The palaeoecology inferred from this faunal assemblage suggests the existence of large forested areas with some grassland and a watercourse nearby, within a notably warm and humid climate. These palaeoenvironmental conditions, combined with AMS and AAR results carried out in macrofaunal bone samples, suggest that the deposit from Artazu VII would be located in the first half of the Late Pleistocene, in the Marine Isotope Stage (MIS) 5c.     

Treatment at different depths and vertical mixing within a 1-m deep horizontal subsurface-flow wetland

The aim of this study was to examine the variation in treatment performance at three depths, and the degree of vertical mixing, within a 1.0 m deep horizontal subsurface-flow constructed wetland (HSSF-CW) planted with Schoenoplectus tabernaemontani (Gmel.) Palla, and treating primary settled municipal wastewater in sub-tropical New South Wales, Australia. Water samples were collected from the upper (0.17 m), middle (0.5 m), and lower (0.83 m) depths at five equi-spaced sample points along the longitudinal axis of the 8.8 m² bed during two trials. Analysis of covariance (ANCOVA) indicated that the rate of pollutant concentration reduction between the three depths was not significantly different (p > 0.05) for all of the measured parameters (dissolved oxygen (DO), hydrogen electrode potentials (E_h), 5-day biochemical oxygen demand (BOD₅)) total nitrogen (TN), TKN, and NH₄-N. Thus, it can be concluded that the break-down of contaminants as wastewater moved through the HSSF-CW was approximately uniform across the 1.0 m depth profile. The lack of a significant depth effect can be largely explained by the substantial amount of vertical mixing that was observed when a pulse of lithium tracer was injected into the middle depth of the first intermediate sampling point. The tracer rapidly migrated vertically into the upper and lower depths as water moved through the bed and was almost completely mixed between the three depths by the time it reached the last intermediate sampling point.The majority of BOD₅ removal occurred within the first-third of the bed where vegetation cover was poor. Performance of the bed declined over time from Trial 1 to Trial 2, possibly due to a cumulative build-up of organic matter within the substrate as a result of limited oxygen transfer throughout the 1.0 m depth of substrate via root leakage or diffusion across the air–water interface. Root penetration was limited to the upper 0.4 m of the substrate, with the majority of below-ground biomass forming a dense mat in the upper 0.2 m. A comparison of two-parameter (K–C^*) first-order volumetric rate constant (K_v20) with those obtained from 0.4 to 0.6 m deep HSSF-CW in the same region indicate that a doubling of the wetted depth resulted in no improvement in BOD₅ removal and a decline in TN removal on an areal basis. Further investigations are warranted, comparing the performance of replicated beds spanning a range of depths (e.g. 0.25, 0.5 and 1.0 m) in order to quantitatively determine the optimal depth of HSSF-CWs treating domestic wastewater.     

Importance of a repetitive nine-residue sequence motif for intracellular stability and functional structure of a family I.3 lipase

PML5 is a functional derivative of a family I.3 lipase from Pseudomonas sp. MIS38 and contains five repeats of a nine-residue sequence motif. Two aspartate residues within the second and third repetitive sequences of PML5 were replaced by Ala. The secretion level, intracellular accumulation level, and stability of the resultant mutant protein were greatly reduced as compared to those of PML5. In addition, this mutant protein was inactive and did not bind Ca2+ ion. We propose that the repetitive sequences of PML5 form a beta-roll structure in the cells and thereby contribute to the intracellular stability and secretion efficiency of the protein.     

Plant responses to precipitation in desert ecosystems: integrating functional types,pulses, thresholds,and delays

The two-layer and pulse-reserve hypotheses were developed 30 years ago and continue to serve as the standard for many experiments and modeling studies that examine relationships between primary productivity and rainfall variability in aridlands. The two-layer hypothesis considers two important plant functional types (FTs) and predicts that woody and herbaceous plants are able to co-exist in savannas because they utilize water from different soil layers (or depths). The pulse-reserve model addresses the response of individual plants to precipitation and predicts that there are biologically important rain events that stimulate plant growth and reproduction. These pulses of precipitation may play a key role in long-term plant function and survival (as compared to seasonal or annual rainfall totals as per the two-layer model). In this paper, we re-evaluate these paradigms in terms of their generality, strengths, and limitations. We suggest that while seasonality and resource partitioning (key to the two-layer model) and biologically important precipitation events (key to the pulse-reserve model) are critical to understanding plant responses to precipitation in aridlands, both paradigms have significant limitations. Neither account for plasticity in rooting habits of woody plants, potential delayed responses of plants to rainfall, explicit precipitation thresholds, or vagaries in plant phenology. To address these limitations, we integrate the ideas of precipitation thresholds and plant delays, resource partitioning, and plant FT strategies into a simple threshold-delay model. The model contains six basic parameters that capture the nonlinear nature of plant responses to pulse precipitation. We review the literature within the context of our threshold-delay model to: (i) develop testable hypotheses about how different plant FTs respond to pulses; (ii) identify weaknesses in the current state-of-knowledge; and (iii) suggest future research directions that will provide insight into how the timing, frequency, and magnitude of rainfall in deserts affect plants, plant communities, and ecosystems.