A prehistoric tsunami induced long-lasting ecosystem changes on a semi-arid tropical island—the case of Boka Bartol (Bonaire, Leeward Antilles)

The Caribbean is highly vulnerable to coastal hazards. Based on their short recurrence intervals over the intra-American seas, high-category tropical cyclones and their associated effects of elevated storm surge, heavy wave impacts, mudslides and floods represent the most serious threat. Given the abundance of historical accounts and trigger mechanisms (strike-slip motion and oblique collision at the northern and southern Caribbean plate boundaries, submarine and coastal landslides, volcanism), tsunamis must be considered as well. This paper presents interdisciplinary multi-proxy investigations of sediment cores (grain size distribution, carbonate content, loss-on-ignition, magnetic susceptibility, microfauna, macrofauna) from Washington-Slagbaai National Park, NW Bonaire (Leeward Antilles). No historical tsunami is recorded for this island. However, an allochthonous marine layer found in all cores at Boka Bartol reveals several sedimentary criteria typically linked with tsunami deposits. Calibrated ¹⁴C data from these cores point to a palaeotsunami with a maximum age of 3,300 years. Alternative explanations for the creation of this layer, such as inland flooding during tropical cyclones, cannot entirely be ruled out, though in recent times even the strongest of these events on Bonaire did not deposit significant amounts of sediment onshore. The setting of Boka Bartol changed from an open mangrove-fringed embayment into a poly- to hyperhaline lagoon due to the establishment or closure of a barrier of coral rubble during or subsequent to the inferred event. The timing of the event is supported by further sedimentary evidence from other lagoonal and alluvial archives on Bonaire.     

Differential effects of temperature variability on the transmission of a marine parasite

Temperature variability is particularly pronounced in intertidal systems. The importance of considering this variability has been increasingly recognised, especially in the context of climate change and disease dynamics. Here, we investigated the effects of temperature variability on the transmission of the intertidal trematode Maritrema novaezealandensis. The experimental treatments were 15 °C (control), 15 + 5 °C daily, 15 + 10 °C every second day, 15 + 15 °C every third day (overall equal thermal loading), and a heat wave treatment (15 + 10 °C daily). Daily 6 h incubations were carried out corresponding to daytime low tides over a 12-day period. Effects on output of transmission stages (cercariae) from infected Zeacumantus subcarinatus snail hosts and transmission success of cercariae to Paracalliope novizealandiae amphipod hosts were quantified, as well as the survival of amphipods. Results showed differential effects on output and transmission success. The number of cercariae emerging was similar for treatments with equal thermal loading, but was substantially increased in the heat wave treatment. Transmission success was highest and comparable for the treatments with regular daily temperature increases (i.e. 15 + 5 °C and heat wave), compared to other treatments. Amphipod survival was not affected by temperature treatment directly, but by the number of parasites infecting an amphipod, as well as amphipod sex. These results demonstrate that cercarial output depends mostly on total thermal loading, whereas successful infection of amphipods is determined by total time above 15 °C. Repeated exposure to ~25 °C, as expected under a heat wave scenario, therefore increases both transmission pressure and success, and hence, the risk of parasite-induced mortality in amphipods.     

Teil I: Stoffstromanalysen landwirtschaftlicher Produktionsverfahren

When discussing strategies for realising an environmental friendly agricultural production, there are methods for quantifying environmental effects which do not originate in agricultural contexts. For instance, the methodology of Life Cycle Assessment is mainly developed from analyses of industrial production lines and products. Substance flow analyses in agriculture contain a complete analysis of agriculturally caused substance and energy flows, to which certain environmental effects are assigned, and also an assessment of these effects. For the provision of production means, balancing agricultural production procedures includes the extraction of energy sources and mineral resources from their reservoirs. The growth phase of the crops regarded (cereals, sugar beet, rape) is described depending on the nutrients nitrogen, phophor, potassium and calcium. The nitrogen flux within the system plant-soil-atmosphere is recorded referring to its temporal dynamic. In the framework of this study, selected environmental effects of agricultural production procedures of winter wheat are calculated regarding different conditions of locations and are supplemented by declining scenario simulations. Essential features of the structure of the substance flow net, which is implemented for the calculation and which can be used completely or as for single modules for further studies, are explained. Basing on selected categories of effectiveness, ecological optimisation potentials of varying agricultural provision of production means and procedures are estimated within the whole context of provision. Thereby, the effects of a reduced employment of fertilisers, of a change as for the kind of fertiliser and of the region of origin of the N-fertiliser, as well as variations concerning mechanical work in the fields are outlined for the cultivation of winter wheat.     

Using the useful: characteristics of used palms in south-eastern Ecuador

Plant families differ greatly with regard to their usefulness to humans. Within families there are also large differences in the usefulness between species; some are used for many different purposes, while most are used for few or no purposes. Which ones and to what extent species are used often varies between areas and cultural groups. To better understand variation in speciesȁ9 usefulness we studied the use of different palm species (Arecaceae) among two socio-cultural groups (one indigenous and one colonist group of mixed ethnic descent) living in the same area. We used regression and correlation analyses to determine to what degree use is related to ecological and morphological characteristics, to geographical differences in abundance, and to peopleȁ9s perceptions of speciesȁ9 availability. We found that abundance and height were the most important characteristics related to use, possibly due to the effect of height and abundance on salience, search time, and (for height) suitability for different purposes. Abundance was most important for palm heart extraction, probably due to the opportunistic nature of this activity. There was no difference between socio-cultural groups with regard to the relationship between palm abundance and use, but abundance seemed to be more decisive for people who used moderate amounts of palms. Finally, it was seen that peopleȁ9s estimates of palm abundance were not related to our measurements of abundance, which may be due to use of different spatial scales in evaluating abundance and to the subjective nature of terms such as “rare” and “abundant”.     

Hexadecane and pristane degradation potential at the level of the aquifer—evidence from sediment incubations compared to in situ microcosms

Monitored natural attenuation is widely accepted as a sustainable remediation method. However, methods providing proof of proceeding natural attenuation within the water-unsaturated (vadose) zone are still relying on proxies such as measurements of reactive and non-reactive gases, or sediment sampling and subsequent mineralisation assays, under artificial conditions in the laboratory. In particular, at field sites contaminated with hydrophobic compounds, e.g. crude oil spills, an in situ evaluation of natural attenuation is needed, because in situ methods are assumed to provide less bias than investigations applying either proxies for biodegradation or off-site microcosm experiments. In order to compare the current toolbox of methods with the recently developed in situ microcosms, incubations with direct push-sampled sediments from the vadose and the aquifer zones of a site contaminated with crude oil were carried out in conventional microcosms and in situ microcosms. The results demonstrate the applicability of the in situ microcosm approach also outside water-saturated aquifer conditions in the vadose zone. The sediment incubation experiments demonstrated turnover rates in a similar range (vadose, 4.7 mg/kg*day; aquifer, 6.4 mg_hexadecane/kg_soil/day) of hexadecane degradation in the vadose zone and the aquifer, although mediated by slightly different microbial communities according to the analysis of fatty acid patterns and amounts. Additional experiments had the task of evaluating the degradation potential for the branched-chain alkane pristane (2,6,10,14-tetramethylpentadecane). Although this compound is regarded to be hardly degradable in comparison to n-alkanes and is thus frequently used as a reference parameter for indexing the extent of biodegradation of crude oils, it could be shown to be degraded by means of the incubation experiments. Thus, the site had a high inherent potential for natural attenuation of crude oils both in the vadose zone and the aquifer.     

PCDD/Fs and PCBs in Baltic herring during the 1990s

Baltic herring samples caught from the Baltic Sea during the spring periods of 1993-1994 and 1999 were analysed for polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and polychlorinated biphenyls (PCB). For analyses, 1570 individual herring were combined to 120 pools. Correlations between concentrations of congeners 1,2,3,7,8-PeCDD, 1,2,3,7,8-PeCDF, 2,3,4,7,8-PeCDF, and 2,3,4,6,7,8-HxCDF, and age of herring were the strongest (r>0.8) followed by correlations between PCB congeners PCB 105, 118, 126, 156, 169 and 180 (r>0.7), and age of herring. Due to higher fat percentage in herring in the Gulf of Bothnia the concentrations of PCDD/Fs and PCBs on fresh weight (fw) basis were higher than in herring in the Gulf of Finland. The concentrations of WHO(PCDD/F)-TEQs ranged from 1 to 27 pg/g fw, depending on the age and catchment area of herring, and concentrations of WHO(PCB)-TEQs reached 32 pg/g fw. Between the two studied time points no clear downward trend in concentrations was observed.