How do fragmented seascapes influence fish movement behaviour? Insights from an individual-based model (IBM) using potential fields

Analysing movement is essential for understanding population dynamics and spatial distributions and has strong implications for the design of natural reserves. In coral reef systems movement patterns of fishes are particularly important as they are an essential part of the ecosystem and many fish species undertake diel migrations using different habitats. However, guidance mechanisms of these movements are not yet well understood. In this study we thus aim to elucidate potential causal mechanisms and spatiotemporal patterns of reef fish movements. To this end, we simulate the movement decision-making of the parrotfish Chlorurus sordidus by linking it with two main functional landscape features (food availability and predation risk) in a novel approach combining individual-based modelling (IBM) with potential field methods. Model results indicate that populations are more irregularly distributed among coral reef patches the more the coral reef habitat becomes fragmented and reduced. The spatial configuration of the seascape thus influences spatial exploitation of microhabitats, which may have far-reaching consequences on the ecosystem. By shaping individual space use patterns, the physical features of the environment may also impact encounter rates between individuals and thus the overall social structure of a population. Based on our findings we believe our model can provide valuable insights into the spatio-temporal variability of local herbivore fish populations. Moreover, the integration of potential field methods into IBMs seems a promising strategy to represent the complexity of dynamic decision-making of animals in applied models

How artificial potential field algorithms can help to simulate trade-offs in movement behaviour of reef fishes

IntroductionSpace use patterns in fish result from the interactions between individual movement behaviour and characteristics of the environment. Herbivorous parrotfishes, for instance, are constrained by the availability of resources and different predation risks. The resulting spatial distribution of the fish population can strongly influence community composition and ecosystem resilience.MethodsIn a novel approach, we combine individual-based modelling (IBM) with an artificial potential field algorithm to realistically represent fish movements and the decision-making process. Potential field algorithms, which are popular methods in mobile robot path planning, efficiently generate the best paths for an entity to navigate through vector fields of repellent and attracting forces. In our model the repellent and attracting forces are predation risk and food availability, both implemented as separate grid-based vector fields. The coupling of individual fish bioenergetics with a navigation capacity provides a mechanistic basis to analyse how the habitat structure influences population dynamics and space utilization.ResultsModel results indicate that movement patterns and the resulting spatial distributions strongly depend on habitat fragmentation with the bioenergetic capacity to spawn and reproduce being particularly susceptible processes at the individual level. The resulting spatial distributions of the population are more irregularly distributed among coral reef patches the more the coral reef habitat becomes fragmented and reduced.DiscussionThis heterogeneity can have strong implications for the delivered ecosystem functioning, e.g., by concentrating or diluting the grazing effort. Our results also highlight the importance of incorporating individual foraging-path patterns and the spatial exploitation of microhabitats into marine spatial planning by considering the effects of fragmentation. The integration of potential fields into IBMs represents a promising strategy to advance our understanding of complex decision-making in animals by implementing a more realistic and dynamic decision-making process, in which each fish weighs different rewards and risks of the environment. This information may help to identify core areas and essential habitat patches and assist in effective marine spatial management

Microbiome structure of the fungid coral Ctenactis echinataaligns with environmental differences

The significance of bacteria for eukaryotic functioning is increasingly recognized. Coral reef ecosystems critically rely on the relationship between coral hosts and their intracellular photosynthetic dinoflagellates, but the role of the associated bacteria remains largely theoretical. Here, we set out to relate coral-associated bacterial communities of the fungid host species Ctenactis echinata to environmental settings (geographic location, substrate cover, summer/winter, nutrient and suspended matter concentrations) and coral host abundance. We show that bacterial diversity of C.echinata aligns with ecological differences between sites and that coral colonies sampled at the species' preferred habitats are primarily structured by one bacterial taxon (genus Endozoicomonas) representing more than 60% of all bacteria. In contrast, host microbiomes from lower populated coral habitats are less structured and more diverse. Our study demonstrates that the content and structure of the coral microbiome aligns with environmental differences and denotes habitat adequacy. Availability of a range of coral host habitats might be important for the conservation of distinct microbiome structures and diversity

Biomonitoring der weiträumigen Verdriftung von Pestiziden mittels Baumrinde, Vegetation und Passivsammler

Anlass für ein Biomonitoring zur weiträumigen Verfrachtung von Pestiziden über die Luft war die wiederholte und erhebliche Kontamination von Bio-Körnerfenchel mit zugelassenen, häufig applizierten Pflanzenschutzmitteln, die kilometerweit von den Fenchelflächen angewendet wurden. Zudem wurde für Glyphosat eine breite Belastung der Bevölkerung gemessen: 99,6% von über 2000 Probanden der bundesweiten Studie „Urinale 2015“. Das Luftgüte-Rindenmonitoring mit Analysen von über 500 Pestiziden wurde von 2014 bis 2017 an 24 Standorten in Brandenburg und Bayern durchgeführt. Weitere Vegetationsproben wie Körnerfenchel und Grünkohl wurden an 11 Standorten und technische Passivsammler (PUF-SIP) an 2 Standorten zur Kalibrierung analysiert. Insgesamt wurden 55 Pestiziden gefunden, im Durchschnitt 27 (4 - 36) pro Standort. Insbesondere zeigten 15 Pestizide eine über einzelne Standorte hinausgehende, weiträumige Verbreitung auf. Diese Drift verursacht eine ubiquitäre Kontamination bishin zu weit entfernt liegenden Naturschutzgebieten. So wurde Pendimethalin an 22 von 24 Standorten (93%), Prosulfocarb bei 75% und sogar Glyphosat bei 33% aller Standorte gemessen. Für derartige hochproblematischen Pestizide sind angemessene Änderungen im Zulassungsverfahren erforderlich, um  Umweltbelastungen wirksam zu reduzieren und die Koexistenz alternativer Anbaumethoden, wie zum Beispiel des ökologischen Landbaus, zu gewährleisten

Primary ChAdOx1 vaccination does not reactivate pre-existing, cross-reactive immunity

Currently available COVID-19 vaccines include inactivated virus, live attenuated virus, mRNA-based, viral vectored and adjuvanted protein-subunit-based vaccines. All of them contain the spike glycoprotein as the main immunogen and result in reduced disease severity upon SARS-CoV-2 infection. While we and others have shown that mRNA-based vaccination reactivates pre-existing, cross-reactive immunity, the effect of vector vaccines in this regard is unknown. Here, we studied cellular and humoral responses in heterologous adenovirus-vector-based ChAdOx1 nCOV-19 (AZ; Vaxzeria, AstraZeneca) and mRNA-based BNT162b2 (BNT; Comirnaty, BioNTech/Pfizer) vaccination and compared it to a homologous BNT vaccination regimen. AZ primary vaccination did not lead to measurable reactivation of cross-reactive cellular and humoral immunity compared to BNT primary vaccination. Moreover, humoral immunity induced by primary vaccination with AZ displayed differences in linear spike peptide epitope coverage and a lack of anti-S2 IgG antibodies. Contrary to primary AZ vaccination, secondary vaccination with BNT reactivated pre-existing, cross-reactive immunity, comparable to homologous primary and secondary mRNA vaccination. While induced anti-S1 IgG antibody titers were higher after heterologous vaccination, induced CD4(+) T cell responses were highest in homologous vaccinated. However, the overall TCR repertoire breadth was comparable between heterologous AZ-BNT-vaccinated and homologous BNT-BNT-vaccinated individuals, matching TCR repertoire breadths after SARS-CoV-2 infection, too. The reasons why AZ and BNT primary vaccination elicits different immune response patterns to essentially the same antigen, and the associated benefits and risks, need further investigation to inform vaccine and vaccination schedule development

Control of human endometrial stromal cell motility by PDGF-BB, HB-EGF and trophoblast-secreted factors

Human implantation involves extensive tissue remodeling at the fetal-maternal interface. It is becoming increasingly evident that not only trophoblast, but also decidualizing endometrial stromal cells are inherently motile and invasive, and likely contribute to the highly dynamic processes at the implantation site. The present study was undertaken to further characterize the mechanisms involved in the regulation of endometrial stromal cell motility and to identify trophoblast-derived factors that modulate migration. Among local growth factors known to be present at the time of implantation, heparin-binding epidermal growth factor-like growth factor (HB-EGF) triggered chemotaxis (directed locomotion), whereas platelet-derived growth factor (PDGF)-BB elicited both chemotaxis and chemokinesis (non-directed locomotion) of endometrial stromal cells. Supernatants of the trophoblast cell line AC-1M88 and of first trimester villous explant cultures stimulated chemotaxis but not chemokinesis. Proteome profiling for cytokines and angiogenesis factors revealed neither PDGF-BB nor HB-EGF in conditioned media from trophoblast cells or villous explants, while placental growth factor, vascular endothelial growth factor and PDGF-AA were identified as prominent secretory products. Among these, only PDGF-AA triggered endometrial stromal cell chemotaxis. Neutralization of PDGF-AA in trophoblast conditioned media, however, did not diminish chemoattractant activity, suggesting the presence of additional trophoblast-derived chemotactic factors. Pathway inhibitor studies revealed ERK1/2, PI3 kinase/Akt and p38 signaling as relevant for chemotactic motility, whereas chemokinesis depended primarily on PI3 kinase/Akt activation. Both chemotaxis and chemokinesis were stimulated upon inhibition of Rho-associated, coiled-coil containing protein kinase. The chemotactic response to trophoblast secretions was not blunted by inhibition of isolated signaling cascades, indicating activation of overlapping pathways in trophoblast-endometrial communication. In conclusion, trophoblast signals attract endometrial stromal cells, while PDGF-BB and HB-EGF, although not identified as trophoblast-derived, are local growth factors that may serve to fine-tune directed and non-directed migration at the implantation site

Effects of atmospheric ammonia on acid deposition : a modelling study.

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