Michelle Bloor

Dietary Preference of Gammarus pulex and Asellus aquaticus during a Laboratory Breeding Programme for Ecotoxicological Studies

An investigation was undertaken to establish if Gammarus pulex and Asellus aquaticus preferred a diet of unconditioned, artificially or naturally conditioned alder leaves (Alnus glutinosa). Standardised, 24 hour ex situ feeding assays were undertaken with both species to determine their food preference. The results showed that A. aquaticus ate more leaf material compared to G. pulex (Z 23.909, P 0.001) when exposed to all three test variables. Also, both G. pulex and A. aquaticus demonstrated a preference for naturally conditioned leaves compared to the other two variables, with unconditioned leaves proving the least popular food option for both macroinvertebrates (Z 18.803, 𝑃l0.001). However, both species ate varying amounts of all the leaf treatments (Z 136.399, 𝑃l0.001). Subsequently, the author outlined a feeding methodology for natural alder leaf conditioning that could be used during a laboratory breeding programme.

Acute and sub-lethal toxicity of landfill leachate towards two aquatic macro-invertebrates: demonstrating the remediation potential of aerobic digestion

A specific landfill leachate that contained 1.036 mgl−1of 2-chlorobiphenyl was used in the study (255 mg l−1 COD and 133 mg l−1 BOD5). Three, 2-l semi-continuous batch reactors (SBRs) were used to simulate the treatment potential of this method on a small scale. Aerobic digestion effectively reduced the leachates COD concentration. Regardless of dilution, the leachates COD reached a <20 mg l−1 equilibrium after 96 h exposure to aerobic digestion, however, increasing the level of dilution accelerated the process. In untreated leachate, the LC50 for Asellus aquaticus was 57% v/v leachate in deionised water and 5% for Gammarus pulex (96 h, static LC50 tests without nutrition and oxygen depleting conditions). After being exposed to aerobic digestion, these values rose to 95% and 40%, respectively. Prolonged exposure to a 1:20 sub-lethal dilution of the aforementioned leachate has been previously shown to affect the breeding colony size of Asellus aquaticus and a 1:66 dilution influenced the fecundity of a Gammarus pulex population. After remediation by aerobic digestion, however, the population dynamics of both test species remained unaltered.

How leachate stress modified the population of two macro-invertebrates:water quality improvements by constructed wetlands?

Leachate stress has previously been shown to modify the population dynamics of both Asellus aquaticus (A. aquaticus) and Gammarus pulex (G. pulex), macro invertebrates ( BLOOR 2004 ). !t was found that prolonged exposure to a l :66 sublethal dilution o f a specific landfill leachate (255 mg 1-1 COD and 133 mg 1BO D s) affected the fecundity o f a G. pulex population, and even a dilution o f l :20 intluenced the breeding colony size of A. aquaticus. The ai m o f the current research was to identify whether constructed wetlands could remediate the aforementioned leachate and, therefore, protect the integrity of riverine species. Reed beds, unlike other wetland plants, have the ability to grow in environments where their root system (rhizosphere) i s submerged. The plants transport air through specialised tissues to their root, and leakage of air from the roots creates aerobic conditions within the water-saturated soi!, which would otherwise be mainly anaerobic. The soi! itself provides a habitat for a wide range of microorganisms, including bacteria, yeasts and fungi, which under natural conditions are responsible for the decay of organic matter releasing nutrients back into the soi!. In a wetland system developed for wastewater remediation these same organisms are responsible for the breakdown of organics within the waste (COBBAN et al. 1997).