Potential Ecosystem Effects Research Articles

Ecosystem effects of fishing in kelp forest communities

Kelp forests, highly diverse cold water communities organized around the primary productivity and physical structure provided by members of the Laminariales, support a variety of fisheries, and the kelp itself is harvested for alginates. Worldwide, these communities generally share susceptibility to destructive overgrazing by sea urchins. The impact of sea-urchin grazing is governed by the ratio between food availability and grazing pressure, thus factors affecting the abundance of both urchins and kelps are central to ecosystem integrity. Some kelp ecosystems share a second generality, the association of exploitation of various urchin predators with destructive levels of urchin grazing, leading to cascading implications for other species dependent on the productivity and habitat provided by the kelps. Competition between abalones and sea urchins also affects some kelp communities. These ecosystem-structuring processes are complicated by a variety of bottom-up and top-down factors, including variability in ocean climate affecting kelp productivity and recruitment of key species, and echinoid disease. Potential ecosystem effects of fisheries for predators, abalones, sea urchins, and kelps are reviewed biogeographically. Given the hundreds to thousands of years that many nearshore marine ecosystems have been exploited, no-take marine reserves may be the only way to determine the true ecosystem effects of fishing.

Presentation and analysis of a model simulating the response of potash treatment of lakes

The potassium concentration in a lake may influence the caesium levels in lake biota. The biouptake and potential ecosystem effects of a caesium fall-out can be limited by addition of potassium, for example, by a potash treatment. This work presents for the first time a simple and practically useful model to facilitate the planning and to predict the outcome of potash treatments by simulating the processes that regulate the water chemical response of such a treatment. The model is a mixed model in the sense that it contains both statistical regressions and dynamic interactions within a lake ecosystem. This paper focuses on the dynamic processes and gives both calibrations and extensive validations of the model. A few examples on the practical use of the model are presented. The results indicate that the model, using only easily accessible input data, can, in fact, give good predictions on the increase and duration in potassium concentration following a potash treatment.

Intact Soil-Core Microcosms for Evaluating the Fate and Ecological Impact of the Release of Genetically Engineered Microorganisms

Intact soil-core microcosms were studied to determine their applicability for evaluating the transport, survival, and potential ecosystem effects of genetically engineered microorganisms before they are released into the environment. Soil-core microcosms were planted with wheat and maize seeds and inoculated with Azospirillum lipoferum SpBr17 and SpRG20a Tn5 mutants, respectively. Microcosm leachate, rhizosphere soil, plant endorhizosphere, insects, and xylem exudate were sampled for A. lipoferum Tn5 mutant populations. A. lipoferum Tn5 populations, determined by most-probable-number technique-DNA hybridization, varied from below detection to 10 g of dry root in the rhizosphere, with smaller populations detected in the endorhizosphere. Intact soil-core microcosms were found to maintain some of the complexities of the natural ecosystem and should be particularly useful for initial evaluations of the fate of plant-associated genetically engineered bacteria.

Attached-algal abundance altered by individual and combined treatments of zinc and pH

Attached-algal communities were employed to test the U.S. Environmental Protection Agency's (EPA) guidelines for zinc (Zn) and pH. The EPA criterion for Zn is 0.047 mg/L, and the EPA effluent standard generally requires that discharge water fall between pH 6 and 9. The experiment was designed to determine whether algal community composition and abundance would be altered by (a) pH 6 or 9, (b) 0.05 mg/L Zn, or (c) the combination of pH 6 or 9 and 0.05 mg/L Zn. Stream mesocosms were continuously supplied with natural water from the New River, Virginia, USA. Established (12-d colonization) communities on artificial substrates were sampled on days 0, 5, 10, 20, and 30 after treatment began on 9 July 1985. Total algal abundance increased in pH 6 treatment. Treatments of pH 6 and 0.05 mg/L Zn reduced abundance of species characteristic of control mesocosms. These species were replaced by species characteristic of 0.05 mg/L Zn and pH 6 mesocosms. These changes occurred even though these levels are considered “safe” by EPA. Community composition did not differ significantly between ambient (pH 8.5) and pH 9 treatments. Although further research is needed, one might speculate that this change in community composition may have potential ecosystem effects by reducing food quality from diatoms to green algae that may inhibit higher level consumers.