58 research outputs found
Polychaete invader enhances resource utilization in a species-poor system
Ecosystem consequences of biodiversity change are often studied from a species loss perspective, while the effects of invasive species on ecosystem functions are rarely quantified. In this experimental study, we used isotope tracers to measure the incorporation and burial of carbon and nitrogen from a simulated spring phytoplankton bloom by communities of one to four species of deposit-feeding macrofauna found in the species-poor Baltic Sea. The recently invading polychaete Marenzelleriaarctia, which has spread throughout the Baltic Sea, grows more rapidly than the native species Monoporeia affinis, Pontoporeia femorata (both amphipods) and Macoma balthica (a bivalve), resulting in higher biomass increase (biomass production) in treatments including the polychaete. Marenzelleria incorporated and buried bloom material at rates similar to the native species. Multi-species treatments generally had higher isotope incorporation, indicative of utilization of bloom material, than expected from monoculture yields of the respective species. The mechanism behind this observed over-yielding was mainly niche complementarity in utilization of the bloom input, and was more evident in communities including the invader. In contrast, multi-species treatments had generally lower biomass increase than expected. This contrasting pattern suggests that there is little overlap in resource use of freshly deposited bloom material between Marenzelleria and the native species but it is likely that interference competition acts to dampen resulting community biomass. In conclusion, an invasive species can enhance incorporation and burial of organic matter from settled phytoplankton blooms, two processes fundamental for marine productivity
Improving the Value of Standard Toxicity Test Data in REACH
Worldwide, environmental risk assessment strategies are based on the assumption that measuring direct effects of single substances, using a few single species tests, in combination with safety factors correcting for extrapolation inconsistencies, can be used to protect higher levels of biological organization, such as populations and even ecosystems. At the same time, we are currently facing a range of pollution problems (Millennium Ecosystem Assessment Series 2005), of which some could at least indirectly be linked to the fact that this assumption may not be fully valid. Consequently, there is an ongoing scientific debate on whether current chemical control protocols are sufficient for protection of ecosystems, and numerous suggestions for improvements have been presented by the scientific community, e.g. alternative tests and testing strategies. On the other hand, few of these suggestions actually reach the regulatory world (or become implemented), and risk assessment today basically follows the same paradigm as 30 years ago. While the new REACH regime is exceptionally ambitious, this chapter observes several problems and gaps in this regulatory framework. We suggest measures and approaches which imply increased ecological realism and understanding in future regulatory work
Effects of temperature in juvenile seabass (Dicentrarchus labrax L.) biomarker responses and behaviour: implications for environmental monitoring
The effects of temperature on European seabass
(Dicentrarchus labrax L.) juveniles were investigated using
a 30-day bioassay carried out at 18 and 25 °C in laboratory
conditions. A multiparameter approach was applied including
fish swimming velocity and several biochemical parameters
involved in important physiological functions. Fish exposed for
four weeks to 25 °C showed a decreased swimming capacity,
concomitant with increased oxidative stress (increased catalase
and glutathione peroxidase activities) and damage (increased
lipid peroxidation levels), increased activity of an enzyme
involved in energy production through the aerobic pathway
(isocitrate dehydrogenase) and increased activities of brain and
muscle cholinesterases (neurotransmission) compared to fish
kept at 18 °C. Globally, these findings indicate that basic
functions, essential for juvenile seabass surviving and well
performing in the wild, such as predation, predator avoidance,
neurofunction and ability to face chemical stress may be compromised
with increasing water temperature. This may be of
particular concern if D. labrax recruitment phase in northwest
European estuaries and coastal areas happens gradually inmore
warm environments as a consequence of global warming.
Considering that the selected endpoints are generally applied
in monitoring studies with different species, these findings also
highlight the need of more research, including interdisciplinary
and multiparameter approaches, on the impacts of temperature
on marine species, and stress the importance of considering
scenarios of temperature increase in environmental monitoring
and in marine ecological risk assessment
Effects of manganese on fat snook Centropomus parallelus (Carangaria: Centropomidae) exposed to different temperatures
Survivorship of juvenile surf clams Donax serra (Bivalvia, Donacidae) exposed to severe hypoxia and hydrogen sulphide
Toxic "sulphide eruptions" sporadically occur in the highly productive inshore regions of the central Namibian Benguela upwelling system. The surf clam Donax serra (Röding, 1798) dominates the intertidal and upper subtidal of large exposed sandy beaches of southern Africa and its recruitment seems to be affected by sulphide events. The reaction of juvenile surf clams to low oxygen concentrations and sulphide occurrence (0.1 mmol l-1) was examined by in vitro exposure experiments in a gas-tight continuous flow system. After 2 h of hypoxic- and hypoxic-sulphidic conditions clams moved to the sediment surface, aiding their passive transport to areas with more favourable conditions. The clams showed a high sulphide detoxification capacity by oxidising the penetrating hydrogen sulphide to non-toxic thiosulphate. Moreover, juvenile D. serra switched to anaerobic energy production, indicated by the significant accumulation of succinate and, to some extent, alanine. Test animals were not able to reduce their energy requirements enough to withstand long periods of exposure, leading to a median survival time (LT50) of 80 h under hypoxic sulphide incubation. In conclusion, natural "sulphide eruptions", especially those with a large spatial and temporal extension, have to be considered as an important factor for D. serra recruitment failures. Hydrogen sulphide is assumed to be a potential community structuring factor
Temperature and salinity: two essential structuring factors of biodiversity in the Baltic Sea
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