Capture of suspended particles by cylindrical collectors is an important mechanism in many aquatic processes, such as larval settlement, suspension feeding, and vegetative filtration. In these processes, the collector Reynolds number (Re c ), based on the collector diameter, ranges from well below 1 to 1,000. No analytical solutions exist to describe capture over most of this range. Capture is typically described by the efficiency, , defined as the ratio of the upstream span of particles that are captured on the collector to the collector diameter. Here, laboratory experiments are used to measure capture efficiency of a single cylinder as a function of Re c and particle ratio, R, which is the ratio of particle diameter to collector diameter. Re c is varied from 50 to 500 and three values of R are used: 0.03, 0.015, and 0.008. The selected particles have a specific gravity of 1.03. For smooth cylinders, capture increases with both Re c and R but is more strongly dependent on R. This result indicates that, in aquatic systems, where flow velocity and suspended particle type and size are fixed, higher capture efficiency will occur on the smallest collectors (those with largest R). Furthermore, we examine a similar experiment in which particles are collected by branched structures. We show that capture to individual cylindrical branches within a compound structure can be predicted by single-cylinder efficiencies. Finally, capture was increased when roughness elements were added to the collectors.

PurposeThe dynamics of organizational change related to environmental sustainability on university campuses are examined in this article. Whereas case studies of campus sustainability efforts tend to classify leadership as either “top‐down” or “bottom‐up”, this classification neglects consideration of the leadership roles of the institutional “middle” – namely the faculty and staff.Design/methodology/approachThe authors draw from research conducted on sustainability initiatives at the University of Guelph combined with a review of faculty and staff‐led initiatives at universities across Canada and the USA, as well as literature on best practices involving campus sustainability. Using concepts developed in business and leadership literature, faculty and staff are shown to be universities' equivalent to social “intrapreneurs”, i.e. those who work for social and environmental good from within large organizations.FindingsFaculty and staff members are found to be critical leaders in efforts to achieve lasting progress towards campus sustainability, and conventional portrayals of campus sustainability initiatives often obscure this. Greater attention to the potential of faculty and staff leadership and how to effectively support their efforts is needed.Originality/valueIn the paper, a case is made for emphasizing faculty and staff leadership in campus sustainability efforts and several successful strategies for overcoming barriers are presented.

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We conducted a field study including a series of cruises over an isolated offshore zebra mussel reef (7-11 m deep) in Western Lake Erie to examine the effect of zebra mussels (Dreissena spp.) on the water column. The horizontal currents over the reef were found to be primarily due to the hydraulic flow and surface gravitational seiches. The turbulence generated by these currents was found to be too weak to fully mix the water column. Although seasonal stratification was not observed, solar heating during the day and intrusions of cold central basin water caused stable stratification of the water column 60% of the time. Results from the seston analysis taken at five depths showed a statistically significant mussel-feeding signature in chlorophyll a and organic seston concentrations measured within 2 m above the reef. Estimates of clearance rates based on field data were consistent with rates measured in a flow chamber using water from the site, which indicated that zebra mussels could remove up to 40% of the total seston. The detection of a zebra mussel-induced concentration boundary layer is due to: (1) reduced vertical mixing as a result of semidiurnal periodic stratification, (2) refiltration of bottom water in zebra mussel populations, and (3) in situ clearance rates that are lower than those observed in the laboratory. Thus, offshore zebra mussel colonies may have less of an effect on the water column than had been previously estimated by simple stirred reactor models, and the role of zebra mussels in the clarification of Lake Erie should be investigated further.

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The round goby (Neogobius melanostomus) first invaded North America in 1990 when it was discovered in the St. Clair River. Despite more than 15 years of potential invasion, many Great Lakes' lotic systems remained uninvaded. Recently, we captured the round goby from several Great Lakes tributaries known as species-at-risk hotspots. With a combination of field sampling of round gobies and literature review of the impact of round gobies on native taxa, we assess the potential impacts of the secondary invasion to native species using three mechanisms: competition; predation; and indirect impacts from the loss of obligate mussel hosts. We estimate that 89% (17/19) of benthic fishes and 17% (6/36) of mussels that occur in these systems are either known or suspected to be impacted by the secondary invasion of round goby. In particular, we note that the distribution of potential impacts of round goby invasion was largely associated with species with a conservation designation, including seven endangered species (1 fish, 6 mussels). As these recent captures of round goby represent novel occurrences in high diversity watersheds, understanding the potential impacts of secondary invasion to native biota is fundamental to prevent species declines and to allow early mitigation.