Reproductive variability over a four-year period in the sea urchin Evechinus chloroticus (Echinoidea: Echinodermata) from differing habitats in New Zealand

 The endemic New Zealand echinoid, Evechinus chloroticus (Valenciennes), was sampled approximately monthly from September 1990 to October 1994 at three sites in Tory Channel, Marlborough Sounds, New Zealand. These channel sites (outer, mid and inner) were up to 20 km from the open ocean and differed in their shore type, exposure to wave action and macrophyte abundance. E. chloroticus showed an annual reproductive cycle at each site, with gametogenesis commencing in the late austral winter and spawning in summer. Maximum gonad indices (reproductive potential) varied spatially, with the outer site generally having higher maximum gonad indices than the inner site, and temporally, with maximum gonad indices occurring earlier in 3 of the 4 seasons at the outer site than the inner site. The mid and inner sites showed much greater variation in maximum gonad indices (range 15.83 to 26.99% and 11.87 to 20.90%, respectively) than the outer site (range 19.31 to 22.95%). Reproductive output (weight of gametes released per gram echinoid) also varied, with the different sites showing significantly different outputs in the different years. A regression of maximum reproductive potential against reproductive output was significant ( p < 0.001), and had a positive slope with an r ² of 0.79. While, the initiation of gametogenesis was relatively synchronous between sites and years, and is possibly cued by increasing daylength, it progressed at different rates among populations. Spawning did show spatial and temporal variability, occurring near the time of highest sea-surface temperatures (∼15 °C). The observed variations in reproductive cycle may be related to small-scale variability in diet and environmental conditions. Furthermore, asynchronous spawning, variable spawning duration, and variable reproductive output are likely to strongly influence annual recruitment variability in E. chloroticus, with different larval subpopulations contributing unequally in different years. The ecological consequences of this, both for the ability of E. chloroticus to propagate itself in space and time and for the management of the developing E. chloroticus fishery in New Zealand, are discussed. Received: 9 December 1998 / Accepted: 13 June 2000     

An experiment on the ability of free-ranging turkey vultures (Cathartes aura) to locate carrion by chemical cues

((without abstract.))     

Interactive effects of wave exposure and tidal height on population structure of the mussel Perna perna

The influence of wave exposure and of tidal height on mussel (Perna perna Linnaeus) population structure (size, density, biomass and adult/juvenile correlations) was examined at 18 sites along the south coast of South Africa. Sites were classified as exposed or sheltered prior to sampling, without reference to the biota, on the basis of aspect, topography and wave regime. A single set of samples was collected from each site during three spring tide cycles. Adult mussels on these shores almost always attach directly to the rocks, and layering of mussels is virtually absent. Shore height always had a strong influence on population structure, but exposure had significant effects only lower on the shore, and almost exclusively on mussel sizes. Principal component analysis (PCA), based on size distribution data for each population, revealed a general upshore decrease in the modal size of the adult cohort. The effects of exposure on size distribution, however, varied with tidal height. PCA separated exposed zones, with larger mussels, from sheltered zones on the low-shore. Farther upshore the two shore types were increasingly confounded. The maximum size of mussels showed a similar pattern, with significant differences (ANOVA, p < 0.05) between exposed and sheltered sites only on the low- and mid-shores. Density was calculated from randomly placed quadrats (i.e. not necessarily from areas of 100% cover) and showed a different pattern. Adult (>15 mm) densities decreased up the shore, with low-, mid- and high-shore zones being significantly different from one another (ANOVA, p < 0.0001; followed by multiple range tests). However, exposure had no significant effect on density, nor was there a significant interaction with zone. Recruit (<15 mm) densities were positively correlated with adult (>15 mm) densities in all zones and for both exposure regimes ( p < 0.05 in all cases), but there was considerable variability and extremely low predictability in these relationships (r ² generally <0.2). Predictability tended to be greater towards the high-shore, where adults were more clumped. As with density, biomass was not affected by exposure, but decreased upshore as mean size and density decreased. A reduction in the influence of exposure farther upshore may be caused by greater emersion overriding the effects of exposure. The presence of free space within mussel beds and significant correlations between recruit and adult densities suggest that these mussel populations are recruit limited. Received: 7 January 2000 / Accepted: 6 July 2000     

Edge Effects on the Understory Bird Community in a Logged Forest in Uganda

Abstract: Understanding how the fauna of logged tropical rainforests responds to fragmentation and the creation of edges is vital to ensure conservation of biodiversity. We studied the composition of the understory bird community from the edge of a 15-ha clearing toward the interior of the forest in a part of Budongo Forest Reserve, Uganda, that was selectively logged about 45 years ago. Mist netting was conducted along five transects from the edge and 500 m into the interior. The total number of individuals captured did not change with distance from the edge, but there was a significant increase in the number of species. We sampled fewer, but more common species near the edge, whereas the interior of the forest had more, and less common species. Guild composition also changed with distance from the edge. Frugivore-insectivores and nectarivores were most common close to the edge. Among insectivores, ground foragers, bark-gleaners, and leaf-gleaners were most common in the interior of the forest, whereas sallying insectivores favored the edge. Graminivores were unaffected by the edge. Analysis of common species showed that Ispidina picta , Andropadus curvirostris , A. latirostris , Camaroptera brachyura , Terpsiphone rufiventer , and Nectarinia olivacea were associated with the edge, but no species showed significant avoidance of the edge. This finding may be explained by the generally low sample sizes of interior species. Our results show that even bird communities in logged forests respond to edges. Estimates of edge effects suggested that changes in bird densities may have occurred several hundred meters from the edge. In conclusion, logged forests provide habitat for bird species avoiding forest edges, and this should be considered in the management of such forests for conservation.     

Coral Bleaching and Global Climate Change: Scientific Findings and Policy Recommendations

Abstract: In 1998, tropical sea surface temperatures were the highest on record, topping off a 50-year trend for some tropical oceans. In the same year, coral reefs around the world suffered the most extensive and severe bleaching ( loss of symbiotic algae) and subsequent mortality on record. These events may not be attributable to local stressors or natural variability alone but were likely induced by an underlying global phenomenon. It is probable that anthropogenic global warming has contributed to the extensive coral bleaching that has occurred simultaneously throughout the reef regions of the world. The geographic extent, increasing frequency, and regional severity of mass bleaching events are an apparent result of a steadily rising baseline of marine temperatures, combined with regionally specific El Niño and La Niña events. The repercussions of the 1998 mass bleaching and mortality events will be far-reaching. Human populations dependent on reef services face losses of marine biodiversity, fisheries, and shoreline protection. Coral bleaching events may become more frequent and severe as the climate continues to warm, exposing coral reefs to an increasingly hostile environment. This global threat to corals compounds the effects of more localized anthropogenic factors that already place reefs at risk. Significant attention needs to be given to the monitoring of coral reef ecosystems, research on the projected and realized effects of global climate change, and measures to curtail greenhouse gas emissions. Even those reefs with well-enforced legal protection as marine sanctuaries, or those managed for sustainable use, are threatened by global climate change.