Jelly-falls historic and recent observations: a review to drive future research directions

The biological pump describes the transport of particulate matter from the sea surface to the ocean’s interior including the seabed. The contribution by gelatinous zooplankton bodies as particulate organic matter (POM) vectors (“jelly-falls”) has been neglected owing to technical and spatiotemporal sampling limitations. Here, we assess the existing evidence on jelly-falls from early ocean observations to present times. The seasonality of jelly-falls indicates that they mostly occur after periods of strong upwelling and/or spring blooms in temperate/subpolar zones and during late spring/early summer. A conceptual model helps to define a jelly-fall based on empirical and field observations of biogeochemical and ecological processes. We then compile and discuss existing strategic and observational oceanographic techniques that could be implemented to further jelly-falls research. Seabed video- and photography-based studies deliver the best results, and the correct use of fishing techniques, such as trawling, could provide comprehensive regional datasets. We conclude by considering the possibility of increased gelatinous biomasses in the future ocean induced by upper ocean processes favouring their populations, thus increasing jelly-POM downward transport. We suggest that this could provide a “natural compensation” for predicted losses in pelagic POM with respect to fuelling benthic ecosystems.     

The effects of drying on sediment nitrogen content in a Mediterranean intermittent stream: a microcosms study

Mediterranean climates predispose aquatic systems to both flood and drought periods, therefore, stream sediments may be exposed to desiccation periods. Changes in oxygen concentrations and sediment water content influence the biotic processes implicated in nitrogen dynamics. The objectives of this study were to identify (1) the changes of inorganic nitrogen in stream sediments during the transition from wet to dry conditions, and (2) the underlying processes in N dynamics and its regulation. Extractable sediment NO₃ ⁻-N and NH₄ ⁺-N, organic matter and extractable organic carbon content were assessed during natural desiccation in microcosms with sediments from an intermittent Mediterranean stream. In agreement with our initial hypothesis, our results showed how the NO₃ ⁻-N content of the sediment was enhanced during the first 10 days of sediment drying, whereas NH₄ ⁺-N was lost by 14 days post-drying. During the first 10 days, sediment desiccation seemed to stimulate the net N-mineralization and net nitrification from sediments. Afterwards, the extractable NO₃ ⁻-N concentration sharply dropped, which may be attributed to lower ammonium-oxidation rates as ammonium and organic matter are depleted, and to an increase in NO₃ ⁻-N consumption by microbial populations. Denitrification was inhibited, with a significant decrease as % water-filled pore space lowered. We hypothesize that the sediment inorganic N content enhanced during sediment desiccation could be released as part of the N pulse observed after sediment rewetting. However, the stream N availability after rewetting dried sediments would differ depending on desiccation period duration.     

Flying over water: how “On bird species diversity” influenced aquatic ecology

Habitat complexity has long been known to influence animal community structure by increasing the number of available habitats. Fifty years have passed since MacArthur brothers published the seminal paper “On bird species diversity”, which revolutionized studies of habitat structure. This paper first evidenced and quantified the relationship between species diversity (birds) and habitat structural complexity (the number of stratified layers of landscape vegetation). In this article, we aim to pay homage to R. H. MacArthur’s contribution and to briefly analyze the citation history and influence of “On bird species diversity”, focusing primarily on aquatic studies. We searched for all papers that cited “On bird species diversity” on Thomson Reuters (ISI—Web of Knowledge) and analyzed them for temporal citation trends. In addition, considering only aquatic papers, we explored whether and how habitat complexity was measured, as well as the ecological organization level, attributes of organisms, taxonomic groups and study design (observational or experimental). “On bird species diversity” citations increased over time, but this paper was less cited by limnologists compared to terrestrial and marine scientists. The majority of investigations in aquatic ecosystems quantified habitat complexity, but few used mathematical modeling. The high number of citations, which continues to increase, shows the great influence of “On bird species diversity” on ecological studies and typifies it as a classic in the ecological literature. However, the low citation frequency found in papers devoted to freshwater ecosystems indicates that limnologists in general neglect this original contribution in studies of habitat complexity.     

<Emphasis Type="Italic">In vitro</Emphasis> plantlet production of the endangered <Emphasis Type="Italic">Pinguicula vulgaris</Emphasis>

This study describes the development of a micropropagation protocol for Pinguicula vulgaris using cultures initiated from in vitro produced seedlings. P. vulgaris is a carnivorous plant with a northern, disjunctly circumpolar distribution and specific habitat requirements, and is hence becoming increasingly rare. Shoot proliferation was significantly influenced by Murashige and Skoog (MS) macronutrient concentration, showing higher proliferation rates in 1/4MS, but was not affected by the addition of 0.1 mg/L 6-benzyladenine (BA) or zeatin (Zea). The best medium for propagating P. vulgaris was plant growth regulator (PGR) free ¼MS. An average of 7.62 new shoots per initial explant could be obtained after 8 weeks of culture, of which over 79% produced roots during proliferation. Moreover, rooting percentages of 100% were obtained for the initial explants in all the tested media, including media without PGRs. The plantlets were successfully acclimatized to ex vitro conditions, exhibiting normal development.     

Serum-free culture of an embryonic cell line from <Emphasis Type="Italic">Bombyx mori</Emphasis> and reinforcement of susceptibility of a recombinant BmNPV by cooling

We established the first continuous cell line that uses a serum-free culture from the embryo of Bombyx mori (Lepidoptera: Bombycidae), designated as NIAS-Bm-Ke17. This cell line was serially subcultured in the SH-Ke-117 medium. The cells adhere weakly to the culture flask, and most cells have an oval shape. The cell line was subcultured 154 times, and the population doubling time is 83.67 ± 5.22 h. Random amplification of polymorphic DNA-polymerase chain reaction with a tenmar single primer for discrimination of insect cell lines recognized the NIAS-Bm-Ke1 cell line as B. mori. This cell line does not support the growth of the B. mori nuclear polyhedrosis virus (BmNPV) in the absence of the heat-inactivated hemolymph of B. mori. However, the heat-inactivated hemolymph in 1% volume of the medium supported a high level of susceptibility to BmNPV. In addition, the cooling treatment of the cells at 2.5°C also enhanced the susceptibility. We report a new serum-free culture system of the B. mori cell line for the baculovirus expression vector system.     

Glycation in diabetic nephropathy

The kidney is an extremely complex organ with broad ranging functions in the body, including but not restricted to waste excretion, ion and water balance, maintenance of blood pressure, glucose homeostasis, generation of erythropoietin and activation of vitamin D. With diabetes, many of these integral processes are interrupted via a combination of haemodynamic and metabolic changes including increases in the accumulation of proteins modified by advanced glycation, known as advanced glycation end products (AGEs). Indeed, hyperglycaemia and the redox imbalances seen with diabetes are each independent accelerants for the production of AGEs, which synergistically combine in this disorder. In addition, as kidney function declines, characterised by a loss of glomerular filtration, the excretion of AGEs is decreased, possibly exacerbating renal injury by further elevating the body’s tissue and circulating AGE pool. Therefore, it has become apparent that decreasing the accumulation of AGEs or interrupting their downstream effects on the kidney, are desirable therapeutic targets for the treatment of diabetic renal disease.     

Effects of spatial scale and sample size in GPS-based species distribution models: are the best models trivial for red deer management?

Species distribution models (SDMs) are popular in conservation and management of a wide array of taxa. Often parameterized with coarse GIS-based environmental maps, they perform well in macro-ecological settings but it is debated if the models can predict distribution within broadly suitable “known” habitats of interest to local managers. We parameterized SDMs with GIS-derived environmental variables and location data from 82 GPS-collared female red deer (Cervus elaphus) from two study areas in Norway. Candidate GLM models were fitted to address the effect of spatial scale (landscape vs. home range), sample size, and transferability between study areas, with respect to predictability (AUC) and explained variance (Generalized R ² and deviance). The landscape level SDM captured variation in deer distribution well and performed best on all diagnostic measures of model quality, caused mainly by a trivial effect of avoidance of non-habitat (barren mountains). The home range level SDMs were far less predictable and explained comparatively little variation in space use. Landscape scale models stabilized at the low sample size of 5–10 individuals and were highly transferrable between study areas implying a low degree of individual variation in habitat selection at this scale. It is important to have realistic expectations of SDMs derived from digital elevation models and coarse habitat maps. They do perform well in highlighting potential habitat on a landscape scale, but often miss nuances necessary to predict more fine-scaled distribution of wildlife populations. Currently, there seems to be a trade-off between model quality and usefulness in local management.