Regional Sediment Deficits in the Dutch Lowlands: Implications for Long-Term Land-Use Options (8 pp)

Background, Aim and Scope   Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance. Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off). We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it in terms of long-term land-use options. Materials and Methods: We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment inputs are based on published minerals statistics. All results are given as first-order approximations. Results: The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145 km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts to ~23 million m3/a. Discussion: As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century. Conclusions: Conclusions, Recommendations and Perspectives. We conclude that sediment deficiency – past, present and future – challenges the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures, costs and benefits, and the implications for long-term land-use options. Recommendations and Perspectives: -     

Considering neighborhood effects improves individual dbh growth models for natural mixed-species forests in Mexico

Key message

More accurate diameter at breast height (dbh)-growth models are needed for developing management tools for mixed-species forests in Mexico. Individual distance-dependent dbh growth models that quantify local neighborhood effects have been developed for four species groups in such forests. The performance of the models is improved by distinguishing between inter- and intraspecific group competitions.

Context

The management of mixed-species forests in the northwest of Durango, Mexico, is mainly based on the selection method. Understanding the interspecific and intraspecific competition is critical to developing management tools for such mixed-species forests.

Aims

An individual-based distance-dependent modeling approach was used to model the growth of dbh and to evaluate neighborhood effects for four species groups in Mexican mixed-species stands.

Methods

Twenty-two species were classified into four groups: Pinus (seven species), other conifers (three species), other broadleaves (four species), and Quercus (eight species). Four methods were used to select neighboring trees and 12 competition indices (CIs) were calculated. Comparisons of the neighboring trees selection methods and CIs and tests of assumptions about neighborhood effects were conducted.

Results

Intra-species-group competition significantly reduced diameter growth for all species groups, except for the Quercus group. The Pinus, other conifers, and Quercus groups had significant and negative neighborhood effects on the other broadleaves species group, and not vice versa. The Quercus group also had negative neighborhood effect on the Pinus and other conifers species groups, and not vice versa. The Pinus and other conifers species groups had negative neighborhood effects on each other. All fitted age-independent dbh growth models showed a good of fit to the data (adjusted coefficient of determination larger than 0.977).

Conclusion

The growth models can be used to predict dbh growth for species groups and competition in mixed-species stand from Durango, Mexico.

     

Subtotal ostectomy of dorsal spinous processes performed in nine standing horses

OBJECTIVE: To describe and evaluate subtotal ostectomy of dorsal spinous processes (DSP) performed in standing horses. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Nine adult horses. METHODS: The diseased portions of the DSP were removed with the horses standing and sedated after infiltrating a local anesthetic agent around the affected DSP. Medical records of affected horses were reviewed to determine history, findings of physical and radiographic examination, surgical technique, postoperative complications, and outcome. RESULTS: Five horses had subtotal ostectomy of DSP because of osteomyelitis, and 4 because of impingement and/or fracture of DSP. Affected portions of DSP were removed safely and effectively, with no apparent discomfort to the horses; hemorrhage was minimal. CONCLUSIONS: Subtotal ostectomy of DSP can be performed safely in standing, conscious horses and the risks associated with general anesthesia are eliminated. Hemorrhage is minimal compared to that which occurs when the procedure is performed with horses anesthetized and in lateral recumbency. CLINICAL RELEVANCE: Access and visibility are better when subtotal ostectomy of the DSP is performed with the horse standing rather than anesthetized and in lateral recumbency. Performing subtotal ostectomy of diseased DSP with the horse standing avoids the expense and risks of general anesthesia.     

Constructed shallow zones along navigation canals: vegetation establishment and change in relation to environmental characteristics

An Erratum has been published for this article in Aquatic Conservation: Marine and Freshwater Ecosystems 12(2), 2002, 251

• 1. In recent decades shallow zones have been constructed along navigation canals in the Netherlands which form a potential new habitat for aquatic macrophytes and helophytes absent from traditional canals.
• 2. The aim of this study was to examine the relationships between the aquatic plant vegetation that becomes established and the physical and chemical characteristics of water and sediment, in order to find the determinants of species composition and the changes therein. Data were collected in 1998 and 1999 from 80 plots in bank zones at varying stages of development since construction along two navigation canals.
• 3. Plots 3–5 years old were partly dominated by rooting submerged macrophytes such as Potamogeton pectinatus, Elodea nuttallii and Potamogeton pusillus; locally non‐rooting species occurred such as Ceratophyllum demersum, Lemna minor and Spirodela polyrhiza. Older plots contained Phragmites australis, locally mixed with free‐floating species. Hydrological isolation from the eutrophic canals was indicated by the presence of Chara vulgaris.
• 4. Characteristics of both water layer and sediment could explain the variation in vegetation composition. Rooting submerged macrophytes predominantly occurred in sites with a thin (<2 cm) layer of sediment with relatively low concentrations of organic matter; moreover, ammonium concentrations in the water layer and sediment pore water were relatively low. Stands of non‐rooting macrophytes and of Phragmites australis were characterized by a relatively thick sediment layer and high ammonium levels in the pore water. Light limitation in turbid water, associated with navigation and eutrophication, may also play a role.
• 5. Although submerged aquatic macrophytes persist for a relatively short time, shallow zones nevertheless function as a habitat for helophyte communities and contribute to a higher aquatic biodiversity than is associated with traditional banks along navigation canals.

Copyright © 2001 John Wiley & Sons, Ltd.     

Improved isolation procedure for azaspiracids from shellfish, structural elucidation of azaspiracid-6, and stability studies

Azaspiracids are a group of lipophilic polyether toxins produced by the small dinoflagellate Azadinium spinosum. They may accumulate in shellfish and can result in illnesses when consumed by humans. Research into analytical methods, chemistry, metabolism, and toxicology of azaspiracids has been severely constrained by the scarcity of high-purity azaspiracids. Consequently, since their discovery in 1995, considerable efforts have been made to develop methods for the isolation of azaspiracids in sufficient amounts and purities for toxicological studies, in addition to the preparation of standard reference materials. A seven-step procedure was improved for the isolation of azaspiracids-1-3 (1, 2, and 3) increasing recoveries 2-fold as compared to previous methods and leading to isolation of sufficiently purified azaspiracid-6 (6) for structural determination by NMR spectroscopy. The procedure, which involved a series of partitioning and column chromatography steps, was performed on 500 g of Mytilus edulis hepatopancreas tissue containing ~14 mg of 1. Overall yields of 1 (52%), 2 (43%), 3 (43%), and 6 (38%) were good, and purities were confirmed by NMR spectroscopy. The structure of 6 was determined by one- and two-dimensional NMR spectroscopy and mass spectrometry. The stability of 6 relative to 1 was also assessed in three solvents in a short-term study that demonstrated the greatest stability in aqueous acetonitrile.     

Implications of the neuroanatomy of the equine thoracolumbar vertebral column with regional anaesthesia and complications following desmotomy of the interspinous ligament

Impinging/overriding dorsal spinous processes (DSPs) of the thoracolumbar vertebrae are a common cause of poor performance in horses. In the last five decades, numerous surgical treatments have been reported on, from transverse transection of the affected DSPs, and endoscopic resection of the affected DSPs, to transection of the interspinous ligament. Until recently, cosmetic outcomes have been reported as good to excellent in studies. However, a previously unreported complication of neurogenic atrophy of the contralateral epaxial muscle following desmotomy of the interspinous ligament has been recently reported. The authors hypothesised that this was because of a more lateral approach than previously described, resulting in the scissors being too far across midline and transecting a nerve in the region. Considering this finding, we have reviewed the literature on the neuroanatomy of the thoracolumbar region in the horse. Literature on the neuroanatomy of the horse is lacking when compared with that of humans and companion animals, with most of the work extrapolated from companion animals. Based on the current literature, we hypothesise that transection of an intermediate branch of the dorsal spinal nerve supplying the m. longissimus is potentially the cause of the post-operative neurogenic atrophy. The lack of detailed knowledge of the neural anatomy of the equine back has resulted in the role of local anaesthesia in localising pain in the equine back being poorly understood. The wide variation in techniques used for localising back pain may explain why some horses suffering from poor performance or an abnormal gait because of back pain improve to local anaesthesia of the back while others do not. This review article highlights a lack of anatomical knowledge regarding the equine thoracolumbar region in the literature despite diagnostic local anaesthesia, medication, and surgery in this area being relatively common.     

Natural progression of Bovine Leukemia Virus infection in Argentinean dairy cattle

We describe the progression of Bovine Leukemia Virus (BLV) infection from birth until the first lactation in 61 animals from a typical large dairy herd of Argentina, with more than 85% of prevalence. The purpose was to identify potential points to effectively break the BLV cycle of transmission in our dairy productive system. We detected early infection in 11.47% of newborn calves by nested PCR. From birth to 12 months, no evidence of new infections was observed. After 12 months of age, the detection of new reactors increased slowly with time, from 15.09% at 15 months to 24% at 27 months. After that, the number of reactors increased rapidly up to 40% and 60.76% at 30 and 36 months, respectively. This last 9-month period coincided with parturition and the entry into the milking herd. Real-time PCR showed that more than 75% of adult animals had low peripheral-blood proviral load. Complementary, all infected animals showed low levels of provirus in milk and colostrum. The most important finding was that even when management procedures to prevent BLV iatrogenic transmission were followed, no significant change was observed in the prevalence after three years, strongly suggesting that other way/s of transmission play a key role under natural conditions. This study showed an interesting baseline to draw an alternative approach based on selective segregation according to the peripheral-blood proviral load as a potential indicator of risk transmission, and as an alternative to classical control measures.     

Structural phylogenetics and the reconstruction of ancient language history

The contribution of language history to the study of the early dispersals of modern humans throughout the Old World has been limited by the shallow time depth (about 8000 +/- 2000 years) of current linguistic methods. Here it is shown that the application of biological cladistic methods, not to vocabulary (as has been previously tried) but to language structure (sound systems and grammar), may extend the time depths at which language data can be used. The method was tested against well-understood families of Oceanic Austronesian languages, then applied to the Papuan languages of Island Melanesia, a group of hitherto unrelatable isolates. Papuan languages show an archipelago-based phylogenetic signal that is consistent with the current geographical distribution of languages. The most plausible hypothesis to explain this result is the divergence of the Papuan languages from a common ancestral stock, as part of late Pleistocene dispersals.     

Sensory characteristics and nutritional value of red drum Sciaenops ocellatus reared in freshwater and seawater conditions

This study compares sensory attributes, chemical composition, fatty acid profiles, and the taste of raw and cooked red drum Sciaenops ocellatus fillets, reared in seawater (SW) and in freshwater (FW) aquaculture systems. Significant nutritional differences were found in the raw fillets. The total lipid was higher (5.31%) in FW fish than the SW (2.60%). The ratio n‐3/n‐6 and EPA/DHA was higher in SW than FW fillets. The eicosenoic acid was only present in FW fillets. DHA was dominant in SW specimens, contrary to the arachidonic acid level, which was dominant in FW fillets. The assessors perceived a significant difference in the firmness and colour of raw fillets, but its odour intensity was not affected. Fillets from SW fish have higher acceptability (33.3%) than FW fillets (26.4%). Sensory differences in raw fillet were not correlated with consumer perceptions, as cooked fish was considered to have similar flavour, independent of its origin.