The authors used data from the National Longitudinal Transition Study-2 (NLTS2; SRI International, 2000) to examine the aspects of self-determination assessed in NLTS2 and measurement equivalence and latent differences across the 12 disability categories recognized in the Individuals With Disabilities Education Act (IDEA; 2004). NLTS2 included a direct assessment with items representing 3 of the 4 essential characteristics of self-determination—autonomy, self-realization, and psychological empowerment. The authors established measurement equivalence, but significant latent differences occurred across specific disability groups. Students with high-incidence disabilities (learning disabilities, emotional disturbances, speech or language impairments, and other health impairments) showed similar latent means and variances, as did students with sensory disabilities (visual and hearing impairments) and cognitive disabilities (autism, multiple disabilities, and deaf-blindness). Students with intellectual disability, traumatic brain injury, and orthopedic impairments could not be collapsed with any other group. Across the 6 collapsed disability groups, significant differences existed in the latent variances and limited mean level differences.

National Longitudinal Transition Study-2. Specifically, the impact of race/ethnicity was examined with six disability groups established in previous research: high incidence disabilities (learning disabilities, emotional disturbances, speech language impairments, and other health impairments), sensory disabilities (visual and hearing impairments), cognitive disabilities (autism, multiple disabilities, and deaf-blindness); intellectual disability, traumatic brain injury, and orthopedic impairments. Measurement equivalence was established across groups, but significant differences in the latent means, variances, and covariances were found suggesting a complex pattern of differences based on race/ethnicity within disability groups. Implications for future research and practice are discussed.

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SUMMARY. A massive population of the common dinoflagellate Ceratium hirundinella developed in Heart Lake. Ontario, Canada during the summer of 1976 and its sudden collapse and subsequent decomposition depleted dissolved oxygen and resulted in a fish‐kill in the lake. The lake was being artificially mixed at the time by supplying compressed air to the bottom waters and the limnological events contributing to the development of the Ceratium population and its collapse appear to be closely related to the artificial destratification process. Artificial destratification during 1976 precluded the development of blue‐green algue. The process also led to an increase in the density of herbivorous zooplankters which controlled the development of smaller planktonic algae. Ceratium flourished in Heart Lake because there was little competition for nutrients from other algae and because Ceratium cells are too large to be grazed by the zooplankton. The maximum size of the Ceratium population (53 mm3 1−1) is apparently the highest biomass reported in the literature and its collapse may have been related to a depletion of inorganic nitrogen. There is apparently no previously published record of a Ceratium‐induced fish‐kill in a freshwater lake.

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