Timothy P. Henkel

Demographics of increasing populations of the giant barrel sponge Xestospongia muta in the Florida Keys

The structure of Caribbean coral reef communities has been altered by numerous anthropogenic and natural stressors. Demographic studies of key functional groups have furthered efforts to describe and understand these changes. Little is known, however, about the demographics of sponges on coral reefs, despite their abundance and the important functions they perform (e.g., increased habitat complexity, water filtration). We have monitored permanent plots on reefs off Key Largo, Florida, USA, to study the demography of a particularly important species, the giant barrel sponge, Xestospongia muta. From 2000 to 2006, population densities of X. muta significantly increased at sites on Conch Reef by a mean of 46% (range = 16-108%) and on Pickles Reef by a mean of 33%. In 2006, densities of X. muta on Conch Reef ranged from 0.134 to 0.277 sponges/m2, and mean sponge volume was 1488 cm3/m2, with the largest size class of sponges constituting 75% of the total volume. Increased population density resulted from a significant increase in the number of sponges in the smallest size class. Recruit survival did not significantly change through time; however, a significant interaction between season and year on recruitment suggests that large recruitment pulses are driving population increases. Mean yearly recruitment rates ranged from 0.011 to 0.025 recruits x m(-2) x yr(-1), with pulses as high as 0.036 recruits/m2. To explore the demographic processes behind the population increase and determine future population growth of X. muta under present reef conditions, a stage-based matrix modeling approach was used. Variable recruitment pulses and mortality events were hypothesized to be large determinants of the demographic patterns observed for X. muta. Elasticity and life table response analysis revealed that survival of individuals in the largest size class has the greatest effect on population growth. Projections indicate that populations of X. muta will continue to increase under present conditions; however population growth may be negatively affected by continued mortality of the largest individuals from a recently described pathogenic syndrome.

Indirect effects of overfishing on Caribbean reefs: sponges overgrow reef-building corals

Consumer-mediated indirect effects at the community level are difficult to demonstrate empirically. Here, we show an explicit indirect effect of overfishing on competition between sponges and reef-building corals from surveys of 69 sites across the Caribbean. Leveraging the large-scale, long-term removal of sponge predators, we selected overfished sites where intensive methods, primarily fish-trapping, have been employed for decades or more, and compared them to sites in remote or marine protected areas (MPAs) with variable levels of enforcement. Sponge-eating fishes (angelfishes and parrotfishes) were counted at each site, and the benthos surveyed, with coral colonies scored for interaction with sponges. Overfished sites had >3 fold more overgrowth of corals by sponges, and mean coral contact with sponges was 25.6%, compared with 12.0% at less-fished sites. Greater contact with corals by sponges at overfished sites was mostly by sponge species palatable to sponge predators. Palatable species have faster rates of growth or reproduction than defended sponge species, which instead make metabolically expensive chemical defenses. These results validate the top-down conceptual model of sponge community ecology for Caribbean reefs, as well as provide an unambiguous justification for MPAs to protect threatened reef-building corals. An unanticipated outcome of the benthic survey component of this study was that overfished sites had lower mean macroalgal cover (23.1% vs. 38.1% for less-fished sites), a result that is contrary to prevailing assumptions about seaweed control by herbivorous fishes. Because we did not quantify herbivores for this study, we interpret this result with caution, but suggest that additional large-scale studies comparing intensively overfished and MPA sites are warranted to examine the relative impacts of herbivorous fishes and urchins on Caribbean reefs.

Breaking the Cycle: Future Faculty Begin Teaching with Learner-Centered Strategies after Professional Development

The authors investigated the extent to which postdoctoral fellows believed in and implemented evidence-based pedagogies after completion of a 2-yr professional development program, FIRST IV. Postdocs reported greater use of learner-centered compared with teacher-centered instruction, and video ratings further documented learner-centered instruction.

Assessing faculty professional development in STEM higher education: Sustainability of outcomes

New faculty sustained the implementation of learner-centered courses in biology following professional development. We tested the effectiveness of Faculty Institutes for Reforming Science Teaching IV (FIRST), a professional development program for postdoctoral scholars, by conducting a study of program alumni. Faculty professional development programs are critical components of efforts to improve teaching and learning in the STEM (Science, Technology, Engineering, and Mathematics) disciplines, but reliable evidence of the sustained impacts of these programs is lacking. We used a paired design in which we matched a FIRST alumnus employed in a tenure-track position with a non-FIRST faculty member at the same institution. The members of a pair taught courses that were of similar size and level. To determine whether teaching practices of FIRST participants were more learner-centered than those of non-FIRST faculty, we compared faculty perceptions of their teaching strategies, perceptions of environmental factors that influence teaching, and actual teaching practice. Non-FIRST and FIRST faculty reported similar perceptions of their teaching strategies and teaching environment. FIRST faculty reported using active learning and interactive engagement in lecture sessions more frequently compared with non-FIRST faculty. Ratings from external reviewers also documented that FIRST faculty taught class sessions that were learner-centered, contrasting with the teacher-centered class sessions of most non-FIRST faculty. Despite marked differences in teaching practice, FIRST and non-FIRST participants used assessments that targeted lower-level cognitive skills. Our study demonstrated the effectiveness of the FIRST program and the empirical utility of comparison groups, where groups are well matched and controlled for contextual variables (for example, departments), for evaluating the effectiveness of professional development for subsequent teaching practices.

Education research: set a high bar.

In their report “Improved learning in a large-enrollment physics class” (13 May, p. [862][1]), L. Deslauriers et al. explored the effects of different instruction techniques on student learning in a college-level physics class. In one group, an experienced teacher taught the lesson using a