Lake Ontario Long Term Biological Monitoring Program: 1981, 1982 Data Base

The Bioindex, or Long Term Biological Monitoring Program, was developed to: 1) determine normal seasonal patterns and annual ranges of abundance, community structure, and when possible, productivity of the biological components - phytoplankton, zooplankton, and benthos; 2) relate the biological components to variations in the physical, nutrient, and biological environment; and, 3) assess the adopted sampling strategy for long term monitoring. The data bases from the first two years are summarized in this document

Effect of reduced salinity conditions on the distribution and responses of the muricid intertidal snail Thais lamellosa gmelin

Limitation of the distribution of the intertidal gastropod, Thais lamellose, by reduced salinity conditions near the mouth of the Fraser River was investigated by studying the snails' responses to and tolerances of such conditions both in the field and laboratory, and by determining its physiological capacity to control body changes in conjunction with decrease in salinity. Evidence of increased tolerance of low salinity through natural selection was sought in comparisons under very low salinities of snails transferred to Spanish Banks from populations normally experiencing low (17%o: Brockton Point) and relatively higher (24%o: Lilly Point)salinities during maximum runoff of the Fraser. Characteristics of dominant species, such as Thais lamellosa, were also discussed and related to McNaughton and Wolf's (1970) hypothesis of specialized dominants. Reactions were evaluated in terms of feeding rates, vertical/horizontal distribution, attachment and mortality. Decreases in salinity effected responses in a specific sequence: feeding decreases, animals descend from exposed surfaces, attachment strength weakens, movement lessens, detachment and then mortality increases. These alterations overlap considerably due to great variability in low salinity tolerance within each population. Immature snails and those removed from the field in summer were more tolerant than adults or those removed in the winter. Duration of exposure was critical to survival. Gradual acclimation and fluctuating conditions were thought to be responsible for the greater tolerances observed in the field as compared with the laboratory. Salinity tolerances of Brockton Point and Lilly Point snails were similar, possibly due to lower salinity conditions at Lilly Point in the past when the Fraser River emptied into the sea via Boundary Bay. Differences in movement and in vertical/horizontal distribution between the two populations were related to topographical differences in the two habitats. Lilly Point consists of extensive sand tracts in the lower intertidal where wayward snails may become lost and/or die of heat exposure and desiccation during low tides in the heat of summer; Brockton Point is rocky with interspersed mats of mussel shells. The snail is capable of detecting salinity changes and of moving to more favourable conditions subtidally. At the extreme of species distribution in Stanley Park fewer animals were found in the intertidal in June, the month of minimal salinities, than in April or July. In addition the species limit corresponds with tolerances defined in the field which suggests that salinity is directly responsible for termination of distribution rather than a biological factor acting on an animal weakened by salinity stress, although this hypothesis has not been tested experimentally. Studies of oxygen consumption and changes in dry weight indicate that metabolism fell with decreases in salinity and temperature. Differences in available energy were reflected in levels of activity rather than in changes in dry weight. Presumably such a response is important in surviving unfavourable periods. With increase in temperature males utilized gonadal material while females appeared to conserve these products. Thais lamellosa is unable to regulate the salinity of its extracellular fluids but can control its volume to some extent under salinity stress, apparently in relation to its degree of euryhalinity. This ability differed between sexes although mortality due to low salinity exposure was independent of sex.Science, Faculty ofZoology, Department ofGraduat

Direct and Indirect Effects of an Invasive Planktonic Predator on Pelagic Food Webs

The relative importance of top-down invader effects relative to environmental drivers was determined by sampling crustacean zooplankton, rotifer, and phytoplankton communities in a set of invaded and noninvaded reference lakes. The non-native invertebrate predator Bythotrephes had significant effects on zooplankton community size structure, rotifers, and phytoplankton taxonomic composition, but no significant effects on crustacean zooplankton taxonomic and functional group composition. Part of the variation in phytoplankton communities was explained by the presence of the invader. Because Bythotrephes is generally known to be a carnivore and to not consume phytoplankton, this effect is likely mediated by the zooplankton community’s response to environmental gradients. Although Bythotrephes appears to indirectly alter phytoplankton composition in invaded lakes, there was no evidence of a trophic cascade, and edible phytoplankton biovolume did not increase in invaded lakes. These complex direct and indirect interactions suggest that effects of invaders may be highly context-dependent, and therefore pose a significant challenge for predicting wider community and ecosystem responses

Appendix B. The relationship between Bythotrephes biomass and absolute prey abundance in the hypolimnion.

The relationship between Bythotrephes biomass and absolute prey abundance in the hypolimnion

Appendix A. Estimates of nonlethal effect produced using a prey somatic growth rate model.

Estimates of nonlethal effect produced using a prey somatic growth rate model

Photo-oxidation processes, properties of DOC, reactive oxygen species (ROS), and their potential impacts on native biota and carbon cycling in the Rio Negro (Amazonia, Brazil)

Given the reported degraded nature of DOC in the Rio Negro, and low oxygen, pH, and bacterial riverine levels, we hypothesized: (1) DOC would have strong humic and fulvic acid fluorescence signals with high aromaticity and large mean molecular weight; and (2) photo-oxidation rates would be slow, and reactive oxygen species (ROS) concentrations low, producing no oxidative stress in biota. We surveyed the environment and properties of DOC and explored DOC photo-oxidation and fish sensitivity to DOC products. DOC properties were investigated using absorption and fluorescence indices and parallel factor analysis (PARAFAC) of excitation–emission matrices. ROS concentrations were measured spectrophotometrically. A native fish, Hemigrammus levis, was exposed to photo-oxidizing DOC and its tissues (brain, gill, liver) assayed for changes in antioxidant and biotransformation enzymes. With respect to our hypotheses, (1) DOC was highly terrigenous, with high SAC340 values (aromaticity), high capacity to produce ROS, and high tryptophan-like fluorescence (bacterial, autochthonous signal); (2) photo-oxidation rates were appreciable, while products were related to mean UV-radiation levels (total radiation was constant). ROS levels were often higher than freshwater averages, yet fish experienced no oxidative stress. Results suggest photo-oxidation influences patterns in C-cycling, bacterial production and community dynamics between wet and dry seasons. © 2016, Springer International Publishing Switzerland

Effects of natural light and depth on rates of photo-oxidation of dissolved organic carbon in a major black-water river, the Rio Negro, Brazil

Systems rich in terrigenous dissolved organic carbon (DOC), like the Rio Negro, can contribute significant amounts of carbon dioxide back to the atmosphere and support important microbial communities. We investigated photo-oxidation in the Rio Negro: (1) the depth to which light causes complete photo-oxidation to CO2 and changes in DOC structure, (2) the daily rate of change of absorbance indices, (3) the relationship between sub-surface rates of photo-oxidation to CO2 and light exposure, (4) the areal rates of photo-oxidation, and (5) the stability of fluorophore signals. Experiments were run in an outdoor pool of Rio Negro water, under natural sunlight during the dry seasons of 2015 and 2018. In 2018, rates of complete photo-oxidation and changes in absorbance indices decayed exponentially, approaching their asymptotes between 9 and 15 cm depth. In 2015, direct absorbance indices ceased changing at 14 cm depth. Fluorescence of humic acid-like moieties continued to decrease, sometimes to 35–43 cm depth. This indicates that partial photo-oxidation of DOC, and thus interaction with the microbial community, occurs to greater depths than previously expected. Areal rates of CO2 production were 28.8 and 39.3 mg C m−2 d−1 (two experiments, October 2018). Sub-surface (1.1 cm) rates were strongly related to light levels, reaching a maximum of 0.68 mg C l−1 d−1 in September. Complete photo-oxidation ceased below 29.6 mW cm−2 d−1 UV radiation, providing a daily baseline for observable production of CO2. Absorbance indices changed by 9 to 14% d−1 at high light levels, except for R254/365 (4.4% d−1). Fluorophore emission ranges were stable between 2014 and 2018, indicating that emissions can be compared across time and space. This study contributes to better estimates and understanding of photo-oxidation in tropical, black-water rivers, which will be useful for carbon modelling. © 2020 Elsevier B.V

Investigating copper toxicity in the tropical fish cardinal tetra (Paracheirodon axelrodi) in natural Amazonian waters: Measurements, modeling, and reality

Copper at high concentrations is an ionoregulatory toxicant in fish and its toxicity is known to be strongly modulated by the water chemistry. The toxicity of Cu to the tropical fish cardinal tetra (Paracheirodon axelrodi) was investigated in waters from two major rivers of the Amazon watershed: the Rio Negro (filtered <0.45 μm, pH 5.6, DOC = 8.4 mg L−1, Na = 33 μM, Ca = 8 μM) and the Rio Solimões (filtered <0.45 μm, pH 6.7, DOC = 2.8 mg L−1, Na = 185 μM, Ca = 340 μM), as well as in a natural “reference water” (groundwater) which was almost DOC-free (pH 6.0, DOC = 0.34 mg L−1, Na = 53 μM, Ca = 5 μM). Acute 96-h mortality, Cu bioaccumulation and net flux rates of Na+, Cl−, K+ and total ammonia were determined in P. axelrodi exposed in each water. Copper speciation in each water was determined by two thermodynamic models and by potentiometry, and its toxicity was predicted based on the biotic ligand model (BLM) framework. Our results indicate that high Na+ loss is the main mode of toxic action of Cu in P. axelrodi, in accordance with general theory. Cardinal tetra showed a particularly high ability to tolerate Cu and to maintain Na+ balance, similar to the ability of this and other endemic Rio Negro species to tolerate low pH and ion-poor conditions. Cu toxicity was lower in Rio Negro than in the other two waters tested, and the free [Cu2+] at the LC50, as determined by any of the three speciation methods tested, was approximately 10-fold higher. This variation could not be captured by a realistic set of BLM parameters. At least in part, this observation may be due to gill physiological alterations induced by the abundant dissolved organic matter of the Rio Negro. The implication of this observation is that, for metals risk assessment in tropical waters, similar to the Rio Negro, care must be used in applying BLM models developed using temperate DOC and temperate species. © 201

Tribute to R.G. Boutilier: The effect of size on the physiological and behavioural responses of oscar, Astronotus ocellatus, to hypoxia.

Made available in DSpace on 2016-01-29T15:04:53Z (GMT). No. of bitstreams: 5 tribute to r g boutilier.pdf: 343832 bytes, checksum: 94a9e9a1e214235a04f3682fdf9ffe65 (MD5) license_url: 49 bytes, checksum: 4afdbb8c545fd630ea7db775da747b2f (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license.txt: 120 bytes, checksum: c5ec8a89f6203da160ca192812b3f657 (MD5) Previous issue date: 2006The physiological and behavioural responses of two size groups of oscar (Astronotus ocellatus) to hypoxia were studied. The physiological responses were tested by measuring ṀO2 during decreasing environmental oxygen tensions. Larger oscars were better able to maintain oxygen consumption during a decrease in PO2, regulating routine ṀO2 to a significantly lower PO2 threshold (50 mmHg) than smaller oscars (70 mmHg). Previous studies have also demonstrated a longer survival time of large oscars exposed to extreme hypoxia, coupled with a greater anaerobic enzymatic capability. Large oscars began aquatic surface respiration (ASR) at the oxygen tension at which the first significant decrease in ṀO2 was seen (50 mmHg). Interestingly, smaller oscars postponed ASR to around 22 mmHg, well beyond the PO2 at which they switched from oxyregulation to oxyconformation. Additionally, when given the choice between an hypoxic environment containing aquatic macrophyte shelter and an open normoxic environment, small fish showed a greater preference for the hypoxic environment. Thus shelter from predators appears particularly important for juveniles, who may accept a greater physiological compromise in exchange for safety. In response to hypoxia without available shelter, larger fish reduced their level of activity (with the exception of aggressive encounters) to aid metabolic suppression whereas smaller oscars increased their activity, with the potential benefit of finding oxygen-rich areas.20

Understanding the gastrointestinal physiology and responses to feeding in air-breathing Anabantiform fishes

The Mekong Delta is host to a large number of freshwater species, including a unique group of facultative air-breathing Anabantiforms. Of these, the striped snakehead (Channa striata), the climbing perch (Anabas testudineus), the giant gourami (Osphronemus goramy) and the snakeskin gourami (Trichogaster pectoralis) are major contributors to aquaculture production in Vietnam. The gastrointestinal responses to feeding in these four species are detailed here. Relative intestinal length was lowest in the snakehead, indicating carnivory, and 5.5-fold greater in the snakeskin, indicating herbivory; climbing perch and giant gourami were intermediate, indicating omnivory. N-waste excretion (ammonia-N + urea-N) was greatest in the carnivorous snakehead and least in the herbivorous snakeskin, whereas the opposite trend was observed for net K excretion. Similarly, the more carnivorous species had a greater stomach acidity than the more herbivorous species. Measurements of acid–base flux to water indicated that the greatest postprandial alkaline tide occurred in the snakehead and a potential acidic tide in the snakeskin. Additional findings of interest were high levels of both PCO (up to 40 mmHg) and HCO (up to 33 mM) in the intestinal chyme of all four of these air-breathing species. Using in vitro gut sac preparations of the climbing perch, it was shown that the intestinal net absorption of fluid, Na and HCO was upregulated by feeding but not net Cl uptake, glucose uptake or K secretion. Upregulated net absorption of HCO suggests that the high chyme (HCO ) does not result from secretion by the intestinal epithelium. The possibility of ventilatory control of PCO to regulate postprandial acid–base balance in these air-breathing fish is discussed