Creating new littoral zones in a shallow lake to forward-restore an aquatic food web.

Current rates of habitat loss require science-based predictions on how to restore or newly create lost habitat types. In aquatic ecosystems, littoral zones are key habitats for food web functioning, but they are often replaced by unnatural steep shorelines for water safety. To reverse this trend, knowledge is needed on how to successfully (re)create littoral zones. We quantified the response of an aquatic food web to the large-scale creation of new heterogeneous littoral habitats in shallow lake Markermeer, the Netherlands. Lake Markermeer was formed by dike construction in a former estuary, which created a heavily modified homogeneous 70,000 ha turbid lake lacking littoral habitat. Fish and bird populations declined over the last decades, but classical restoration via return to former marine conditions would compromise water safety and the large spatial scale prohibited biodiversity offsets. Therefore, an innovative "forward-looking restoration" approach was adopted: a 1000 ha archipelago called "Marker Wadden" was constructed without using a historic reference situation to return to. This aimed bottom-up stimulation of the aquatic food web by adding missing gradual land-water transitions and sheltered waters to the lake. After four years, new sheltered shorelines had become vegetated if they were constructed from nutrient-rich sediments. Exposed and sandy shorelines remained free of vegetation. Zooplankton community diversity increased in sheltered waters due to bottom-up processes, which increased food availability for higher trophic levels, including young fish. The creation of sheltered waters increased macroinvertebrate densities threefold, with sediment type determining the community composition. The archipelago became new nursery habitat for 13 of the 24 fish species known to occur in the lake, with up to 10-fold higher abundances under sheltered conditions. We conclude that modifying abiotic conditions can stimulate multiple trophic levels in aquatic food webs simultaneously, even in heavily modified ecosystems. This provides proof-of-principle for the forward-looking restoration approach.

Green turtles shape the seascape through grazing patch formation around habitat features: Experimental evidence.

Understanding how megaherbivores incorporate habitat features into their foraging behavior is key toward understanding how herbivores shape the surrounding landscape. While the role of habitat structure has been studied within the context of predator-prey dynamics and grazing behavior in terrestrial systems, there is a limited understanding of how structure influences megaherbivore grazing in marine ecosystems. To investigate the response of megaherbivores (green turtles) to habitat features, we experimentally introduced structure at two spatial scales in a shallow seagrass meadow in The Bahamas. Turtle density increased 50-fold (to 311 turtles ha-1 ) in response to the structures, and turtles were mainly grazing and resting (low vigilance behavior). This resulted in a grazing patch exceeding the size of the experimental setup (242 m2 ), with reduced seagrass shoot density and aboveground biomass. After structure removal, turtle density decreased and vigilance increased (more browsing and shorter surfacing times), while seagrass within the patch partly recovered. Even at a small scale (9 m2 ), artificial structures altered turtle grazing behavior, resulting in grazing patches in 60% of the plots. Our results demonstrate that marine megaherbivores select habitat features as foraging sites, likely to be a predator refuge, resulting in heterogeneity in seagrass bed structure at the landscape scale.

More salt, please: global patterns, responses and impacts of foliar sodium in grasslands.

Sodium is unique among abundant elemental nutrients, because most plant species do not require it for growth or development, whereas animals physiologically require sodium. Foliar sodium influences consumption rates by animals and can structure herbivores across landscapes. We quantified foliar sodium in 201 locally abundant, herbaceous species representing 32 families and, at 26 sites on four continents, experimentally manipulated vertebrate herbivores and elemental nutrients to determine their effect on foliar sodium. Foliar sodium varied taxonomically and geographically, spanning five orders of magnitude. Site-level foliar sodium increased most strongly with site aridity and soil sodium; nutrient addition weakened the relationship between aridity and mean foliar sodium. Within sites, high sodium plants declined in abundance with fertilisation, whereas low sodium plants increased. Herbivory provided an explanation: herbivores selectively reduced high nutrient, high sodium plants. Thus, interactions among climate, nutrients and the resulting nutritional value for herbivores determine foliar sodium biogeography in herbaceous-dominated systems.

Experimental manipulation of predation risk and food quality: effect on grazing behaviour in a central-place foraging herbivore.

The relative importance of predation risk and food quality on spatial grazing pressure and activity patterns was tested in a central-place foraging herbivore: the European rabbit. Rabbits grazed less with increasing distance from their burrows into adjacent grassland, thereby creating a gradient of increasing vegetation height and plant biomass and decreasing plant nutrient concentration. When nitrogen concentration was experimentally increased by 150% through fertilizing and mowing, rabbits visited these plots four times more frequently than the untreated control plots. Addition of predator scent (mink pellets) did not result in different patch use by rabbits. The combined addition of fertilizer and mink pellets had the same effect as addition of fertilizer alone. However, the mink pellets changed the temporal activity pattern of rabbits as measured with infrared detectors. Rabbits were predominantly nocturnal but shifted their activities to the day when mink pellets were added, resulting in equal activities during night and day. We conclude that rabbits are sensitive to perceived predation risk, but that this does not influence their spatial grazing pressure. A selection for the highest food quality on the other hand can explain the observed natural rabbit grazing gradient. Food quality was highest close to the burrows, therefore rabbits selecting for high quality food should forage most intensely close to the burrows and only move further away for higher quality items or when the vegetation close to their burrows is depleted. Through intensive grazing close to the burrows rabbits facilitated for themselves either through stimulating fresh protein rich re-growth or the return of nutrients through faeces or both. This is in contrast with central-place foraging theory where intense feeding close to the burrow is assumed to lead to reduced food resources.

Impact of herbivores on nitrogen cycling: contrasting effects of small and large species.

Herbivores are reported to slow down as well as enhance nutrient cycling in grasslands. These conflicting results may be explained by differences in herbivore type. In this study we focus on herbivore body size as a factor that causes differences in herbivore effects on N cycling. We used an exclosure set-up in a floodplain grassland grazed by cattle, rabbits and common voles, where we subsequently excluded cattle and rabbits. Exclusion of cattle lead to an increase in vole numbers and a 1.5-fold increase in net annual N mineralization at similar herbivore densities (corrected to metabolic weight). Timing and height of the mineralization peak in spring was the same in all treatments, but mineralization in the vole-grazed treatment showed a peak in autumn, when mineralization had already declined under cattle grazing. This mineralization peak in autumn coincides with a peak in vole density and high levels of N input through vole faeces at a fine-scale distribution, whereas under cattle grazing only a few patches receive all N and most experience net nutrient removal. The other parameters that we measured, which include potential N mineralization rates measured under standardized laboratory conditions and soil parameters, plant biomass and plant nutrient content measured in the field, were the same for all three grazing treatments and could therefore not cause the observed difference. When cows were excluded, more litter accumulated in the vegetation. The formation of this litter layer may have added to the higher mineralization rates under vole grazing, through enhanced nutrient return through litter or through modification of microclimate. We conclude that different-sized herbivores have different effects on N cycling within the same habitat. Exclusion of large herbivores resulted in increased N annual mineralization under small herbivore grazing.

Pharmacological effects of a specific leukotriene B(4) receptor antagonist (VML 295) on blood leukocytes, cutaneous inflammation and epidermal proliferation.

VML 295 (LY 293111) is a potent and specific leukotriene(4) receptor antagonist. It has previously been shown in human volunteers that VML 295 at a dosage of 48 mg twice daily inhibits the ex vivo leukotriene B(4) (LTB(4))-induced upregulation of CD11b on peripheral blood neutrophils. A clear dose-response relatinship was shown. In addition, VML 295 inhibits various inflammatory aspects resulting from LTB(4) challenge of the skin, again showing a dose-response relationship. In view of the large variation in the elimination half-life of VML 295 (25-88.5 h) in individual human subjects, the present pharmacological study was designed to provide information on the pharmacodynamics of the drug by the assessment of VML 295 plasma concentrations, ex vivo LTB(4)-induced CD11b upregulation of neutrophils, neutrophil accumulation in the skin following epicutaneous application of LTB(4) and epidermal regeneration following standardized surface trauma. A group of 36 healthy volunteers were treated in a double-blind study with VML 295 at 200 mg twice daily, VML 295 at 200 mg once daily or placebo for 7 days. Before treatment, at the end of treatment and following discontinuation of treatment, VML 295 plasma concentrations and CD11b upregulation of blood neutrophils were assessed. In 18 subjects, the effects of the three treatments on LTB(4)-induced inflammatory were assessed before and at the end of treatment, and in the remaining 18 subjects the effects of these treatments on epidermal regeneration were assessed similarly. VML 295 at 200 mg either twice or once daily has a profound inhibitory effect on ex vivo LTB(4)-induced CD11b upregulation of blood neutrophils, LTB(4)-induced neutrophil accumulation in the skin, trauma-induced hyperproliferation of the epidermis and regenerative keratinization. The twice daily dose schedule was significantly more effective than the once daily regimen in reducing ex vivo CD11b stimulation of neutrophils, in blood samples collected 24 h after discontinuation of VML 295 treatment. The twice daily schedule tended to be more efficient in skin biopsies, although this difference was not statistically significant in the number of subjects investigated. A plasma concentration of 100 ng/ml proved to be the threshold for these effects. The profound biological effects, both systemically and cutaneously, as well as the safety profile, make VML 295 a promising drug for skin disorders characterized by epidermal proliferation and neutrophil accumulation.

Investigation on a novel and specific leukotriene B4 receptor antagonist in the treatment of stable plaque psoriasis.

The aim of the present study was to investigate the efficacy and clinical tolerability of the specific leukotriene B4 receptor antagonist VML295 in the treatment of stable plaque psoriasis. Immunohistochemical and flow cytometrical methods were used to assess the effects on inflammation and epidermal proliferation. VML295 in the treatment of chronic plaque psoriasis was shown to be safe and well tolerated. After treatment, there was a statistically significant difference between patients treated with VML295 and patients treated with placebo with respect to the leukotriene B4-induced CD11b up-regulation on the cell surface of polymorphonuclear leukocytes derived from peripheral blood. Ex vivo CD11b up-regulation in the VML295-treated group was completely inhibited after 7 days of treatment (P = 0.001). This effect persisted until the end of the treatment period (P = 0.004 on day 15 and P < 0.0001 after 4 weeks), whereas CD11b up-regulation in the placebo group remained unaffected. There was no statistically significant difference in the median psoriasis area and severity index between the treatment groups at the end of the treatment period. During treatment, no significant histological changes were observed in the markers for cutaneous inflammation and epidermal proliferation. Although not statistically significant, a tendency for the increased expression of some markers of cutaneous inflammation and epidermal proliferation was observed after 1 week of treatment with VML295, and a decreased expression of these markers was seen after 4 weeks of treatment with VML295. This observation could indicate anti-inflammatory effects of VML295 appearing between 2 and 4 weeks after the start of treatment.

The efficacy of a new topical treatment for psoriasis: Mirak.

BACKGROUND: A new natural product for the treatment of psoriasis has recently become available in many European countries: Mirak. The Mirak Home Care Packs consist of natural spring water, volcanic earth and vitamin E cream. Recently, the efficacy of Mirak has come into question. As this treatment is used by many psoriasis patients in Europe, it is important for dermatologists to be informed about the clinical effects of the therapy. AIM: To evaluate the efficacy and side effects of the Mirak Home Care Packs. METHODS: By means of a placebo-controlled left/right comparison, both clinical and histological parameters were evaluated during 6 weeks of treatment. RESULTS: The reduction in induration was significantly greater in the Mirak-treated lesions than in the lesions treated with a placebo. A reduction in desquamation was found in both treatments; the difference between the treatments was not statistically significant. A decrease in number of proliferative cells in the Mirak-treated lesions was seen, but the difference with placebo-treated lesions was not significant. The other investigated parameters did not change during treatment. No side effects were seen. CONCLUSIONS: The Mirak Home Care Pack induces a modest therapeutic effect compared to placebo treatment, without significant side effects. Treatment with the Mirak Home Care Packs alone will probably not be able to compete with the already existing treatments for psoriasis.

Effects of systemic treatment with liarozole on cutaneous inflammation, epidermal proliferation and differentiation in extensive plaque psoriasis.

Liarozole is a novel inhibitor of the enzyme cytochrome P450 which has inhibitory effects on the 4-hydroxylation of retinoic acid. Previous studies have shown that liarozole is effective in the treatment of psoriasis. We performed an immunohistochemical study on the lesional skin from 7 patients with extensive plaque psoriasis, who were treated with systemic liarozole 75 mg BID for a period of at least 2 months. The effects of liarozole treatment on clinical and histological parameters were investigated. In particular, the effect of liarozole on the integrin markers CD11b and CD18 was studied. For immunohistochemistry, three consecutive biopsies were taken: before treatment, after 4, and after 8 weeks of treatment. Clinical scores and side effects were recorded before and during treatment. The medication was well tolerated and only mild side effects were reported, which were comparable with hypervitaminosis A. After 2 months of treatment a statistically significant decrease of the extent of body involvement was observed. In the psoriatic plaque, markers for epidermal proliferation and cutaneous inflammation decreased, and markers for epidermal differentiation increased to values comparable to normal skin. The first therapeutic effects in the psoriatic plaque occurred after 4 weeks of treatment, and consisted of a decreased induration, accompanied by a decrease of the total number of inflammatory infiltrate cells and a decreased epidermal ICAM-1 expression. Already after 4 weeks of treatment, a decrease of CD11b-positive cells was observed. Subsequently, after 8 weeks of treatment recruitment of cycling epidermal cells and the number of involucrin-positive cell layers decreased. The present study demonstrates that liarozole treatment of psoriasis results in a reduction of aspects of cutaneous inflammation and subsequently a reduction of epidermal proliferation and promotion of differentiation. After 4 weeks of treatment, effects are observed on the epidermal ICAM-1 expression and on the CD11b-positive cell population.