Iron mining began in Wawa, Ontario in the late 1800s and ceased in 1998. The sintering process of iron pyrite produced sulfur dioxide which led to the acidification of nearby lakes. Benthic macroinvertebrate samples were collected from lakes along a gradient of historical impairment in Wawa to examine the extent to which the benthos of the lakes would separate along the historical impairment gradient. The results show that the lakes are not separated along a gradient of impairment, and acid-intolerant taxa were collected in previously acidified lakes. There was no ameliorative intervention to combat the historical acidification and the observed recovery of water chemistry and benthos is entirely due to natural ecosystem processes. The two sampling methods (littoral kick sampling using a D-net and Hester-Dendy substrates) used to sample the benthos in these lakes can lead to substantial differences in the taxa collected.

Epilithic biofilms were monitored for potential impacts of an experimental rainbow trout aquaculture operation at the Experimental Lakes Area in northwestern Ontario, Canada. Metabolic and particulate samples were collected from the middle littoral zone of the experimental and reference lakes before and during the aquaculture operation. Phosphorus stocks in the experimental lake (epilimnetic and epilithic) increased as a result of both food waste and fish excretion. These cumulative P inputs were predicted to increase epilithic biomass and productivity, cause major compositional changes in the dominant groups and increase epilithic algal toxin production (microcystins). However, no major aquaculture-related changes in algal biomass, productivity, toxins or group dominance were observed in the epilithon. The only observed changes occurred at the species-level. These species-level changes were transient but did allude to an ecosystem reacting to stress. / February 2009

Thesis (MAppSc--Applied Science) -- AUT University, 2009. / Includes bibliographical references. Also held in print ( xii, 195 p leaves ; 30 cm.) in the Archive at the City Campus (T 578.777 BOY)

This study documents the marine sponge fauna (Phylum Porifera) in the Northwest Atlantic, through the used of fishermen’s local ecological knowledge, fisheries observer data, trawl survey data and in situ exploration. A review of the role of structural benthic species, including ascidians, bryozoans, corals, hydroids and sponges as ecosystem engineers provides the context within which to discuss the contribution of sponges to seafloor habitat heterogeneity. Fishermen’s knowledge is useful in identifying areas of high concentration of benthic structural species, but is not particularly useful in determining the distribution of specific sponge species, with the exception of glass sponges, with the common name “Russian Hat”. Fisheries observer data from the Scotia Fundy Region and trawl survey data from the Newfoundland Region were obtained from the years 1977-2001 and 1973-2007 respectively. Despite the lack of systematic collection of information on sponge catches, prior to 2002, the information recorded show broad scale patterns of sponge distribution from the Scotian Shelf to the Eastern Arctic, and this thesis brings this information together for the first time. The move to deeper and more northern waters following the groundfish collapse in 1992 resulted in large catches of sponges, up to 5000kg per set, on the Labrador Shelf and Eastern Arctic. The combination of fishermen’s information, observer data and in situ research on the Scotian Shelf resulted in the identification of a previously undescribed and globally unique population of Vazella pourtalesi, a Hexactinellid sponge, in the Family Rossellidae. The impacts of fishing on the sponge community of the Gulf of Maine were examined by quantifying the sponge community inside and outside of the Western Gulf of Maine Closed Area. After two years, the sponge community within the closed area was dominated by the demosponge, Iophon sp. while the area that remained open to fishing had a higher diversity of sponges. The information presented in this thesis can inform marine ecosystem management, particularly in light of international obligations to protect vulnerable marine ecosystems.

Epilithic biofilms were monitored for potential impacts of an experimental rainbow trout aquaculture operation at the Experimental Lakes Area in northwestern Ontario, Canada. Metabolic and particulate samples were collected from the middle littoral zone of the experimental and reference lakes before and during the aquaculture operation. Phosphorus stocks in the experimental lake (epilimnetic and epilithic) increased as a result of both food waste and fish excretion. These cumulative P inputs were predicted to increase epilithic biomass and productivity, cause major compositional changes in the dominant groups and increase epilithic algal toxin production (microcystins). However, no major aquaculture-related changes in algal biomass, productivity, toxins or group dominance were observed in the epilithon. The only observed changes occurred at the species-level. These species-level changes were transient but did allude to an ecosystem reacting to stress.

No description available.

No description available.

Headwater drainage features (HDFs) in the GTA are commonly subjected to land-use modifications including agricultural uses and urbanization. A temporal study design approach was used to test whether the runoff being exported from previously modified HDFs differed from runoff exported from less disturbed forested channels. Drift nets were deployed in the permanent reaches of streams and in the HDF channels, to give an indication of the quality and quantity of drifting materials. Gastric lavage was used to remove stomach contents from creek chub living downstream from HDFs and these contents were used to determine if invertebrates in HDF runoff could act as food immediately upon reaching fish-bearing sections of stream. Reaches of streams associated with forested HDFs were found to have more fish than either those associated with agricultural or urban HDFs (203, 184 and 145 fish per forested, agricultural and urban site, respectively). Sites associated with forested catchments also had a greater number of salmonids per site. Conditions of high flow in the stream and the HDF coincided with an increased quantity of drifting invertebrates in all site types and land uses, as well as a decrease in the proportion of creek chub with empty stomachs. Overall, aquatic Diptera were the most numerous invertebrates captured in drift nets and in the stomach contents of creek chub. Hymenoptera, terrestrial Oligochaeta and Diplopoda also made major contributions to the diets of creek chub. Results indicate that HDFs in all land uses are exporting both aquatic and terrestrial invertebrates to main streams at times of high flow. Creek chub consume more prey at times of high flow, and this often includes terrestrial invertebrates, which must have been imported from terrestrial sources to the aquatic environment, however the degree to which they are exported by HDFs is still not clear. The series of complex interactions occurring at the HDF/main stream interface requires further study.

Epilithic biofilms were monitored for potential impacts of an experimental rainbow trout aquaculture operation at the Experimental Lakes Area in northwestern Ontario, Canada. Metabolic and particulate samples were collected from the middle littoral zone of the experimental and reference lakes before and during the aquaculture operation. Phosphorus stocks in the experimental lake (epilimnetic and epilithic) increased as a result of both food waste and fish excretion. These cumulative P inputs were predicted to increase epilithic biomass and productivity, cause major compositional changes in the dominant groups and increase epilithic algal toxin production (microcystins). However, no major aquaculture-related changes in algal biomass, productivity, toxins or group dominance were observed in the epilithon. The only observed changes occurred at the species-level. These species-level changes were transient but did allude to an ecosystem reacting to stress.

No description available.