Littoral microcrustacean (Cladocera and Copepoda) indicators of acidification in Canadian Shield lakes

We identify littoral microcrustacean indicators of acidification in 2 surveys of Canadian Shield lakes conducted 10 years apart. We found a total of 90 cladoceran and copepod species with richness increasing severalfold from acidic to nonacidic lakes. The fauna of the nonacidic lakes differed between the surveys. The 1987 survey employed activity traps, and caught more littoral taxa than the more recent, net-haul-based survey. Similar faunas were identified in the acidified lakes in both surveys, and several good indicator species were identified. For example, Acanthocycops vernalis was restricted to lakes with pH < 6. Sinobosmina sp. was very common but only in lakes with pH > 4.8. Tropocyclops extensus, Mesocyclops edax, and Sida crystallina were commonly found but only at pH > 5, and Chydorus faviformis only at pH > 5.9. These indicators showed promise in gauging the early stages of recovery from acidification in 3 lakes that were included in both surveys.     

Developing conceptual frameworks for the recovery of aquatic biota from acidification

Surface water acidity is decreasing in large areas of Europe and North America in response to reductions in atmospheric S deposition, but the ecological responses to these water-quality improvements are uncertain. Biota are recovering in some lakes and rivers, as water quality improves, but they are not yet recovering in others. To make sense of these different responses, and to foster effective management of the acid rain problem, we need to understand 2 things: i) the sequence of ecological steps needed for biotic communities to recover; and ii) where and how to intervene in this process should recovery stall. Here our purpose is to develop conceptual frameworks to serve these 2 needs. In the first framework, the primarily ecological one, a decision tree highlights the sequence of processes necessary for ecological recovery, linking them with management tools and responses to bottlenecks in the process. These bottlenecks are inadequate water quality, an inadequate supply of colonists to permit establishment, and community-level impediments to recovery dynamics. A second, more management-oriented framework identifies where we can intervene to overcome these bottlenecks, and what research is needed to build the models to operationalize the framework. Our ability to assess the benefits of S emission reduction would be simplified if we had models to predict the rate and extent of ecological recovery from acidification. To build such models we must identify the ecological steps in the recovery process. The frameworks we present will advance us towards this goal.     

Photodegradation of hydroxylated N-heteroaromatic derivatives in natural-like aquatic environments. A review of kinetic data of pesticide model compounds

In the present review, the results published by our group and others related with the study of the kinetic behavior and, in some cases, the mechanism of the dye-promoted photooxygenation of several hydroxypyridines, hydroxyquinolines and hydroxypyrimidines--some of them with the basic molecular structures of known pesticides, and of a few non-hydroxylated model compounds, are compiled and discussed. The main aim was to examine the experimental conditions that maximize the photodegradation efficiencies of all these compounds, under dye-sensitized photooxidation conditions similar to those frequently found in nature, with a natural dye sensitizer such as riboflavin (vitamin B2), a pigment habitually present in natural waters. The usual mechanism of action of this compound is rather complex, in many cases with the concurrent involvement of the oxidative species singlet molecular oxygen (O2(1Deltag)) and superoxide radical anion. In order to simplify the study of the processes, the results found using the synthetic dye Rose Bengal (RB), a sensitizer that generates O2(1Deltag) with high efficiency, are also discussed. RB and similar O2(1Deltag)-generators could be used for the efficient non-natural photodegradation of related pesticides in aqueous solutions under controlled conditions.     

Colony founding,queen dominance and oligogyny in the Australian meat ant Iridomyrmex purpureus

Summary Field observations and laboratory experiments demonstrate that in the Australian meat ant, Iridomyrmex purpureus, the modes of colony founding are remarkably diverse. New colonies can originate from single foundresses (haplometrosis), or foundress associations (pleometrosis), or by colony budding, or the adoption of newly-mated queens that dig founding chambers next to mature nests (probably their natal nests, as workers protect them and may help them dig). Readoption of foundresses and pleometrosis lead to the coexistence of several queens in one nest. We discovered a striking antagonistic behavior among coexisting queens in young colonies, in the form of ritualized antennation bouts. These interactions result in a reproductive rank order in which dominant queens inhibit egg-laying by subordinates, but escalation into physical fighting is rare. Workers ignore queen dominance interactions and treat all queens equally. The first quantitative ethogram of dominance display behavior between multiple ant queens, and its reproductive consequences, is presented. As a colony grows, queens become intolerant of each other's presence and permanently separate within the nest. Once separated, queens appear to be equal in status, laying approximately equal numbers of eggs. All queens continue to be tolerated by workers, even when the colony has reached a size of several thousand workers and begun to produce reproductives. Such mature nests of I. purpureus fulfill the criteria of oligogyny, defined by worker tolerance toward more than one queen and antagonism among queens, such that a limited number of fully functional queens are spaced far apart within a single colony. Oligogynous colonies can arise in this species by pleometrotic founding (primary oligogyny) or by adoption of queens into existing nests (secondary oligogyny). The adaptive significance of the complex system of colony founding, queen dominance and oligogyny in I. purpureus is discussed.     

Use of Water Clarity to Monitor the Effects of Climate Change and other Stressors on Oligotrophic Lakes

We present evidence from studies oflakes in Killarney Park, Ontario, Canada that waterclarity is a key variable for monitoring theeffects of climate change, high UV exposure andacidification. In small oligotrophic lakes, thesestressors affect water clarity primarily byaltering the concentration of DOC in lake water. Clear lakes (<2 mg L^-1 DOC) proved to be highlysensitive indicators of stressors, exhibiting largethermal and optical responses to small changes inDOC. Extremely clear (<0.5 mg L^-1 DOC) acidic lakesshowed the effects of climate change and solarbleaching in recent decades. These lakes becamemuch clearer even though they were slowlyrecovering from acidification.     

Auditing the Accuracy of a Volunteer-Based Surveillance Program for an Aquatic Invader Bythotrephes

We tested the sampling methods of a volunteer-based monitoring program designed to detect the non-indigenous spiny water flea, Bythotrephes longimanus, and found that the program could detect the majority of Bythotrephes invasions. Volunteers take two vertical hauls with a 30 cm diameter net at each of three pelagic stations. To determine if the volunteers were using a large enough net at their three stations, we performed a 17-lake comparison of the volunteer's net with a 75 cm diameter, research-grade net. We found no difference in the number of stations at which Bythotrephes was detected (paired t-test, p = 0.155) with the two nets, because Bythotrephes densities were above the detection limits for both nets. To determine if three stations were sufficient to detect the invader with the volunteer's net, we deployed it at 30 stations in two lakes with average (Harp Lake, 4.17 Bythotrephes m(-3)) vs. low Bythotrephes densities (Sugar Lake, 0.92 m(-3)). In Harp Lake, repeated randomized sampling of the 30 sets of data indicated that only three stations were needed for 100% capture success. In Sugar Lake, seven stations were needed for 100% capture success, but three stations, the current program design, failed to detect the invasion only 14% of the time.     

Are followers satisfied with conscientious leaders? The moderating influence of leader role authenticity

Leadership scholars have yet to identify a clear and consistent relationship between leader conscientiousness and followers' satisfaction with a leader. Drawing from socioanalytic theory and related personality research, we argue that the underlying motives of leader conscientiousness can manifest in systematically different behaviors aimed at team task accomplishment, ranging from rigid and order‐driven to relatively more adaptable approaches. Importantly, we posit that the relationship between a leader's conscientiousness and adaptability is conditioned by role authenticity (i.e., the extent to which a leader believes a role permits expressions of her or his “true self”). Hence, we articulate a conditional indirect effects model whereby leader conscientiousness and leader role authenticity jointly predict leader adaptability and, in turn, increasing levels of leader adaptability are positively associated with followers' shared satisfaction with their leader. Data from a sample of fire and rescue crews provide partial support for the model. Post hoc analyses suggest that the conditioning influence of leader role authenticity on leader conscientiousness is more informative when subfacets of conscientiousness are considered.