H.J. de Lange

Ecological vulnerability in risk assessment — A review and perspectives

This paper reviews the application of ecological vulnerability analysis in risk assessment and describes new developments in methodology. For generic non-site-specific assessments (e.g. for the requirements of most European directives on dangerous chemicals) risk is characterised just on the basis of the ratio between an effect indicator and an exposure indicator. However, when the actual risk for a specific ecosystem is desired, the concept of ecological vulnerability may be more appropriate. This calls for a change in thinking, from sensitivity at the organism level to vulnerability at higher organization levels, and thus forms the link from laboratory toxicology to field effects at population, community or ecosystem level. To do so, biological and ecological characteristics of the ecosystems under concern are needed to estimate the ecological vulnerability. In this review we describe different vulnerability analysis methods developed for populations (of a single species), communities (consisting of different populations of species) and ecosystems (community and habitat combined). We also give some examples of methods developed for socio-ecological systems. Aspects that all methods share are the use of expert judgment, the input of stakeholders, ranking and mapping of the results, and the qualitative nature of the results. A new general framework is presented to guide future ecological vulnerability analysis. This framework can be used as part of ecological risk assessment, but also in risk management. We conclude that the further quantification of ecological vulnerability is a valuable contribution to vulnerability assessment.

Framework for traits‐based assessment in ecotoxicology

A key challenge in ecotoxicology is to assess the potential risks of chemicals to the wide range of species in the environment on the basis of laboratory toxicity data derived from a limited number of species. These species are then assumed to be suitable surrogates for a wider class of related taxa. For example, Daphnia spp. are used as the indicator species for freshwater aquatic invertebrates. Extrapolation from these datasets to natural communities poses a challenge because the extent to which test species are representative of their various taxonomic groups is often largely unknown, and different taxonomic groups and chemicals are variously represented in the available datasets. Moreover, it has been recognized that physiological and ecological factors can each be powerful determinants of vulnerability to chemical stress, thus differentially influencing toxicant effects at the population and community level. Recently it was proposed that detailed study of species traits might eventually permit better understanding, and thus prediction, of the potential for adverse effects of chemicals to a wider range of organisms than those amenable for study in the laboratory. This line of inquiry stems in part from the ecology literature, in which species traits are being used for improved understanding of how communities are constructed, as well as how communities might respond to, and recover from, disturbance (see other articles in this issue). In the present work, we develop a framework for the application of traits-based assessment. The framework is based on the population vulnerability conceptual model of Van Straalen in which vulnerability is determined by traits that can be grouped into 3 major categories, i.e., external exposure, intrinsic sensitivity, and population sustainability. Within each of these major categories, we evaluate specific traits as well as how they could contribute to the assessment of the potential effects of a toxicant on an organism. We then develop an example considering bioavailability to explore how traits could be used mechanistically to estimate vulnerability. A preliminary inventory of traits for use in ecotoxicology is included; this also identifies the availability of data to quantify those traits, in addition to an indication of the strength of linkage between the trait and the affected process. Finally, we propose a way forward for the further development of traits-based approaches in ecotoxicology.

Changes in Ventilation and Locomotion of Gammarus pulex (Crustacea, Amphipoda) in Response to Low Concentrations of Pharmaceuticals

ABSTRACT Exposure to contaminants below lethal concentrations may affect the performance of organisms, resulting in measurable differences in behavior. We measured the response of the benthic invertebrate Gammarus pulex (Crustacea, Amphipoda) to sublethal concentrations of three pharmaceuticals, fluoxetine, ibuprofen and carbamazepine, and the cationic surfactant cetyltrimethylammonium bromide (CTAB). Responses in behavior during exposure were analyzed using the multivariate method of Principal Response Curves (PRC). The PRC results show that exposure to low pharmaceutical concentrations (range 1–100 ng/l) resulted in increased ventilation, whereas exposure to control or to high concentrations (1 μ g/l–1 mg/L) resulted in increased locomotion. Exposure to CTAB resulted in decreased locomotion and increased ventilation at increasing concentrations. The results of our experiments indicate that increased ventilation can be used as a general sign of stress, but not necessarily an early warning signal for mortality.

Seston composition and the potential for Daphnia growth

A field survey was conducted to study the relationships amongst the composition of the seston, the nutritional value of the seston for herbivorous zooplankton (Daphnia), and selected water clarity parameters. Sixteen ponds in a wetland area and seven larger lakes, all located in south central Saskatchewan, Canada, were sampled for seston. The phytoplankton species were identified, and various biochemical seston variables were measured. A biotest using the zooplankter Daphnia magna, was employed to assess the nutritional value of the seston. The best seston variable to explain Daphnia growth was the phospholipid content (simple linear regression analysis: R2adj = 0.50). The water absorbance ratio A250/A365 was a good predictor of lipid content of the seston. Both the absorbance ratio A250/A365 and the dissolved organic carbon (DOC) concentration were negatively correlated with Daphnia growth. We hypothesize that the penetration of visible and ultraviolet radiation is an important determinant of seston quality, especially the phospholipid content, and that this has important implications for determining ultimate growth rates of herbivorous zooplankton.

Variation in the behavior of the amphipod Gammarus pulex.

ABSTRACT Variation in the locomotion behavior of Gammarus pulex was studied using the Multispecies Freshwater Biomonitor®. Behavior was recorded individually under a 12:12 h light:dark cycle for a period of 7 d during which the amphipods were not fed. Gammarids behaved differently during the first 7 h in the laboratory chambers. Most specimens were active and decreased their activity but some were relatively inactive after the start of the experiment and increased their locomotion. At least 2 h are needed by G. pulex to accustom to the conditions. No significant relationships existed between type of behavior during the acclimation period or acclimation time and gender or length of the gammarids. There was a large variation in time spent on locomotion during the first night. In general, males were significantly more active than females. Within males, a distinction can be made between very active and less active specimens. The 7-d observation period showed that only 70% of the specimens demonstrated a clear day–night rhythm with higher activity during the night. Unexpectedly, approximately 10% of the specimens were more active during daytime. Furthermore, in this study locomotion became relatively stable only after 4 d. Inter-individual variation in behavior must be taken into account when using behavior as an endpoint in ecotoxicological bioassays.

‘Halophyte filters’: the potential of constructed wetlands for application in saline aquaculture

World consumption of seafood continues to rise, but the seas and oceans are already overexploited. Land-based (saline) aquaculture may offer a sustainable way to meet the growing demand for fish and shellfish. A major problem of aquaculture is nutrient waste, as most of the nutrients added through feed are released into the environment in dissolved form. Wetlands are natures water purifiers. Constructed wetlands are commonly used to treat contaminated freshwater effluent. Experience with saline systems is more limited. This paper explores the potential of constructed saline wetlands for treating the nutrient-rich discharge from land-based saline aquaculture systems. The primary function of constructed wetlands is water purification, but other ancillary benefits can also be incorporated into treatment wetland designs. Marsh vegetation enhances landscape beauty and plant diversity, and wetlands may offer habitat for fauna and recreational areas. Various approaches can be taken in utilizing plants (halophytes, macro-algae, micro-algae) in the treatment of saline aquaculture effluent. Their strengths and weaknesses are reviewed here, and a conceptual framework is presented that takes into account economic and ecological benefits as well as spatial constraints. Use of the framework is demonstrated for assessing various saline aquaculture systems in the southwestern delta region of the Netherlands.

Efficiency of three halophyte species in removing nutrients from saline water : a pilot study

Saline wetlands may be well suited for purifying contaminated water from saline agriculture and aquaculture or from freshwater-based agriculture in areas subject to increased salinity. However, case studies on the nutrient removal efficiency of halophyte species are scarce, especially for temperate regions. Here we tested the nutrient removal efficiency and ability to store nutrients in aboveground and belowground biomass of three halophyte species, Aster tripolium, Bolboschoenus maritimus subsp. compactus, and Spartina anglica, in a greenhouse microcosm experiment at two salinity levels. Nutrient removal from water differed among the species: Spartina had the highest nitrogen removal, Bolboschoenus and Spartina had the highest phosphorus removal. The species also differed in the allocation of the nutrient uptake. Bolboschoenus had the highest absolute uptake of nitrogen and phosphorus in shoots, whereas Spartina had the highest uptake of nitrogen and phosphorus in roots. The applicability of these three species in constructed saline wetlands depends on the local salinity and water regime.