Indirect effects in aquatic ecosystems

Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Science of The Total Environment (Impact Factor: 4.1). 01/2004; 317(1-3):207-33. DOI: 10.1016/S0048-9697(03)00141-4
Source: PubMed


Contaminants such as petroleum hydrocarbons, heavy metals and pesticides can cause direct toxic effects when released into aquatic environments. Sensitive species may be impaired by sublethal effects or decimated by lethality, and this ecological alteration may initiate a trophic cascade or a release from competition that secondarily leads to responses in tolerant species. Contaminants may exert direct effects on keystone facilitator and foundation species, and contaminant-induced changes in nutrient and oxygen dynamics may alter ecosystem function. Thus, populations and communities in nature may be directly and/or indirectly affected by exposure to pollutants. While the direct effects of toxicants usually reduce organism abundance, indirect effects may lead to increased or decreased abundance. Here we review 150 papers that reference indirect toxicant effects in aquatic environments. Studies of accidental contaminant release, chronic contamination and experimental manipulations have identified indirect contaminant effects in pelagic and benthic communities caused by many types of pollutants. Contaminant-induced changes in behavior, competition and predation/grazing rate can alter species abundances or community composition, and enhance, mask or spuriously indicate direct contaminant effects. Trophic cascades were found in 60% of the manipulative studies and, most commonly, primary producers increased in abundance when grazers were selectively eliminated by contaminants. Competitive release may also be common, but is difficult to distinguish from trophic cascades because few experiments are designed to isolate the mechanism(s) causing indirect effects. Indirect contaminant effects may have profound implications in environments with strong trophic cascades such as the freshwater pelagic. In spite of their undesirable environmental influence, contaminants can be useful manipulative tools for the study of trophic and competitive interactions in natural communities.

Download full-text


Available from: Roger M Nisbet,
  • Source
    • "However, also chronic direct effects and acute and chronic sublethal toxic effects can lead to changes in invertebrate communities through reduced reproduction or predator avoidance. Likewise, effects on other groups of organisms such as primary producers that were not included in our study may propagate to invertebrate consumers (Fleeger et al., 2003). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The European Union aims to reach a 10% share of biofuels in the transport sector by 2020. The major burden is most likely to fall on already established annual energy crops such as rapeseed and cereals for the production of biodiesel and bioethanol, respectively. Annual energy crops are typically cultivated in intensive agricultural production systems, which require the application of pesticides. Agricultural pesticides can have adverse effects on aquatic invertebrates in adjacent streams. We assessed the relative ecological risk to aquatic invertebrates associated with the chemical pest management from six energy crops (maize, potato, sugar beet, winter barley, winter rapeseed, and winter wheat) as well as from mixed cultivation scenarios. The pesticide exposure related to energy crops and cultivation scenarios was estimated as surface runoff for 253 small stream sites in Central Germany using a GIS-based runoff potential model. The ecological risk for aquatic invertebrates, an important organism group for the functioning of stream ecosystems, was assessed using acute toxicity data (48-h LC50 values) of the crustacean Daphnia magna. We calculated the Ecological Risk from potential Pesticide Runoff (ERPR) for all three main groups of pesticides (herbicides, fungicides, and insecticides). Our findings suggest that the crops potato, sugar beet, and rapeseed pose a higher ecological risk to aquatic invertebrates than maize, barley, and wheat. As maize had by far the lowest ERPR values, from the perspective of pesticide pollution, its cultivation as substrate for the production of the gaseous biofuel biomethane may be preferable compared to the production of, for example, biodiesel from rapeseed.
    Science of The Total Environment 12/2015; 537:187-196. DOI:10.1016/j.scitotenv.2015.08.011 · 4.10 Impact Factor
  • Source
    • "The release of chemical contaminants in the marine environment is one of the main threats currently altering marine individuals, populations and ecosystems (Fitzgerald and Clarkson, 1991; Fleeger et al., 2003; Halpern et al., 2008; Tartu et al., 2013). This issue is of particular concern in the Mediterranean Sea, as the numerous highly-populated and industrialized countries around this sea exert a strong pressure on it (Durrieu de Madron et al., 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Chemical contamination levels and stable isotope ratios provide integrated information about contaminant exposure, trophic position and also biological and environmental influences on marine organisms. By combining these approaches with otolith shape analyses, the aim of the present study was to document the spatial variability of Hg and PCB contamination of the European hake (Merluccius merluccius) in the French Mediterranean, hypothesizing that local contaminant sources, environmental conditions and biological specificities lead to site-specific contamination patterns. High Hg concentrations discriminated Corsica (average: 1.36±0.80μgg(-1)dm) from the Gulf of Lions (average values<0.5μgg(-1)dm), where Rhône River input caused high PCB burdens. CB 153 average concentrations ranged between 4.00±0.64 and 18.39±12.38ngg(-1)dm in the Gulf of Lions, whatever the sex of the individuals, whereas the highest values in Corsica were 6.75±4.22ngg(-1)dm. Otolith shape discriminated juveniles and adults, due to their different habitats. The use of combined ecotracers was revealed as a powerful tool to discriminate between fish populations at large and small spatial scale, and to enable understanding of the environmental and biological influences on contamination patterns. Copyright © 2015 Elsevier B.V. All rights reserved.
    Science of The Total Environment 11/2015; 532:184-194. DOI:10.1016/j.scitotenv.2015.06.020 · 4.10 Impact Factor
    • "In addition, many measurement endpoints derived from field biomonitoring such as biotic indices have mainly been designed for streams and rivers, and do not allow direct and relevant comparisons with lentic ecosystems. Thus, complementary approaches (e.g., trait-based approach, Fleeger et al. 2003; Baird et al. 2008; van den Brink et al. 2011) are strongly recommended to comprehensively assess the effects of chemical exposure at the ecosystem level. Differences between mesocosm types can also influence the interpretation of the recovery dynamics of communities. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Higher-tier ecological risk assessment (ERA) in mesocosms is commonly performed in lotic or lentic experimental systems. These systems differ in their physico-chemical and hydrological properties, leading to differences in chemical fate, community characteristics and potential recovery. This raises the issue of the relevance and sensitivity of community-level endpoints in different types of mesocosms. In this study, macroinvertebrate abundance and biomass estimates were used to assess the effects of a dithiocarbamate fungicide, thiram (35 and 170 µg l(-1)), and a petroleum middle distillate (PMD; 0.01, 0.4, 2 and 20 mg l(-1)) in outdoor stream and pond mesocosms. Streams were continuously treated during 3 weeks followed by a 2-month long post-treatment period. Ponds were treated weekly for 4 weeks, followed by a 10-month long post-treatment period. Taxonomic structure of macroinvertebrate communities was characterized using the α, β and γ components of taxa richness, Shannon and Gini-Simpson indices. Computations were based either on abundance or biomass data. Results clearly highlighted that the effects of chemicals depended on the exposure regime (for thiram) and type of system (for the PMD). Causes of the differences between streams and ponds in the magnitude and nature of effects include differential sensitivity of taxa dwelling in lentic and lotic systems and the influence of hydrology (e.g., drift from upstream) and mesocosm connectivity on recovery dynamics. This study also showed complementarities in the use of both types of mesocosms to improve the characterization of chemical effects on communities in ERA.
    Ecotoxicology 09/2015; DOI:10.1007/s10646-015-1534-5 · 2.71 Impact Factor
Show more